Merge branch 'iscsi-refactor'

1 files changed, 5152 insertions, 0 deletions

diff --git a/src/server/iscsi.h b/src/server/iscsi.h
new file mode 100644
index 0000000..a1582fe
--- /dev/null
+++ b/src/server/iscsi.h
@@ -0,0 +1,5152 @@
+/*
+ * This file is part of the Distributed Network Block Device 3
+ *
+ * Copyright(c) 2011-2012 Johann Latocha <johann@latocha.de>
+ *
+ * This file may be licensed under the terms of the
+ * GNU General Public License Version 2 (the ``GPL'').
+ *
+ * Software distributed under the License is distributed
+ * on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
+ * express or implied. See the GPL for the specific language
+ * governing rights and limitations.
+ *
+ * You should have received a copy of the GPL along with this
+ * program. If not, go to http://www.gnu.org/licenses/gpl.html
+ * or write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+/**
+ * @file iscsi.h
+ * @author Sebastian Vater
+ * @date 07 Jul 2025
+ * @brief iSCSI header for DNBD3.
+ *
+ * This file contains the header file for the iSCSI
+ * implementation according to RFC7143 for dnbd3-server.
+ * @see https://www.rfc-editor.org/rfc/rfc7143
+ */
+
+#ifndef DNBD3_ISCSI_H_
+#define DNBD3_ISCSI_H_
+
+#include <limits.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <dnbd3/types.h>
+
+#include "globals.h"
+
+#if defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
+	 // GCC-compatible compiler, targeting x86/x86-64
+	 #include <x86intrin.h>
+#elif defined(__GNUC__) && defined(__ARM_NEON__)
+	 // GCC-compatible compiler, targeting ARM with NEON
+	 #include <arm_neon.h>
+#elif defined(__GNUC__) && defined(__IWMMXT__)
+	 // GCC-compatible compiler, targeting ARM with WMMX
+	 #include <mmintrin.h>
+#elif (defined(__GNUC__) || defined(__xlC__)) && (defined(__VEC__) || defined(__ALTIVEC__))
+	 // XLC or GCC-compatible compiler, targeting PowerPC with VMX/VSX
+	 #include <altivec.h>
+#elif defined(__GNUC__) && defined(__SPE__)
+	 // GCC-compatible compiler, targeting PowerPC with SPE
+	 #include <spe.h>
+#elif defined(_MSC_VER)
+	 // Microsoft C/C++-compatible compiler
+	 #include <intrin.h>
+#endif
+
+#if defined(__BIG_ENDIAN__) || (defined(__BYTE_ORDER) && defined(__BIG_ENDIAN) && __BYTE_ORDER == __BIG_ENDIAN) || (defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#define iscsi_get_be16(x) (x)
+#define iscsi_get_be24(x) (iscsi_get_be32((*(uint32_t *) ((uint8_t *) x - 1))) & 0xFFFFFFUL)
+#define iscsi_get_be32(x) (x)
+#define iscsi_get_be64(x) (x)
+
+static inline void iscsi_put_be16(uint8_t *data, const uint16_t value)
+{
+	(*(uint16_t *) data) = value;
+}
+
+static inline void iscsi_put_be24(uint8_t *data, const uint32_t value)
+{
+	data--;
+
+	(*(uint32_t *) data) = (((uint32_t ) *data << 24UL) | (value & 0xFFFFFFUL));
+}
+
+static inline void iscsi_put_be32(uint8_t *data, const uint32_t value)
+{
+	(*(uint32_t *) data) = value;
+}
+
+static inline void iscsi_put_be64(uint8_t *data, const uint64_t value)
+{
+	(*(uint64_t *) data) = value;
+}
+
+#elif defined(__LITTLE_ENDIAN__) || (defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && __BYTE_ORDER == __LITTLE_ENDIAN) || (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__) || defined(__i386__) || defined(__i386) || defined(__x86_64)
+#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
+// GCC or CLang
+#define iscsi_get_be16(x) (__builtin_bswap16(x))
+#define iscsi_get_be24(x) (iscsi_get_be32((*(uint32_t *) ((uint8_t *) x - 1))) & 0xFFFFFFUL)
+#define iscsi_get_be32(x) (__builtin_bswap32(x))
+#define iscsi_get_be64(x) (__builtin_bswap64(x))
+#elif defined(_MSC_VER)
+// MSVC
+#define iscsi_get_be16(x) (_byteswap_ushort(x))
+#define iscsi_get_be24(x) (iscsi_get_be32((*(uint32_t *) ((uint8_t *) x - 1))) & 0xFFFFFFUL)
+#define iscsi_get_be32(x) (_byteswap_ulong(x))
+#define iscsi_get_be64(x) (_byteswap_uint64(x))
+#elif defined(__INTEL_COMPILER) || defined(__ECC)
+// Intel Compiler
+#define iscsi_get_be16(x) (_bswap16(x))
+#define iscsi_get_be24(x) (iscsi_get_be32((*(uint32_t *) ((uint8_t *) x - 1))) & 0xFFFFFFUL)
+#define iscsi_get_be32(x) (_bswap(x))
+#define iscsi_get_be64(x) (_bswap64(x))
+#else
+// Other compilers (use slow conversion method with bit rotation, bit shift and logcal AND)
+#define iscsi_get_be16(x) ((((uint16_t) (x)) << 8U) | (((uint16_t) (x)) >> 8U))
+#define iscsi_get_be24(x) (iscsi_get_be32((*(uint32_t *) ((uint8_t *) x - 1))) & 0xFFFFFFUL)
+#define iscsi_get_be32(x) ((((uint32_t) (x) & 0xFFUL) << 24UL) | (((uint32_t) (x) & 0xFF00UL) << 8UL) | (((uint32_t) (x) & 0xFF0000UL) >> 8UL) | (((uint32_t) (x) >> 24UL)))
+#define iscsi_get_be64(x) ((uint64_t)((((x) & 0xFFULL) << 56ULL) | (((x) & 0xFF00ULL) << 40ULL) | (((x) & 0xFF0000ull) << 24ULL) | (((x) & 0xFF000000ULL) << 8ULL) | (((x) & 0xFF00000000ULL) >> 8ULL) | (((x) & 0xFF0000000000ULL) >> 24ULL) | (((x) & 0xFF000000000000ULL) >> 40ULL) | (((x) & 0xFF00000000000000ULL) >> 56ULL)))
+#endif
+
+static inline void iscsi_put_be16(uint8_t *data, const uint16_t value)
+{
+	(*(uint16_t *) data) = iscsi_get_be16(value);
+}
+
+static inline void iscsi_put_be24(uint8_t *data, const uint32_t value)
+{
+	data--;
+
+	(*(uint32_t *) data) = ((uint32_t ) *data | (iscsi_get_be32(value) & 0xFFFFFF00UL));
+}
+
+static inline void iscsi_put_be32(uint8_t *data, const uint32_t value)
+{
+	(*(uint32_t *) data) = iscsi_get_be32(value);
+}
+
+static inline void iscsi_put_be64(uint8_t *data, const uint64_t value)
+{
+	(*(uint64_t *) data) = iscsi_get_be64(value);
+}
+
+#else
+#error "Unknown CPU endianness"
+#endif
+
+
+/// Determines the next offset after member b of struct a.
+#define ISCSI_NEXT_OFFSET(a, b) (offsetof(struct a, b) + sizeof(((struct a *) 0)->b))
+
+
+/// Bit sequence manipulation double word (32 bits) mask bits: Gets mask for filtering out a bit range between a and b, b may NOT exceed 30 bits range.
+#define ISCSI_BITS_GET_MASK(a, b) (((1U << (a)) - 1U) ^ ((1U << ((b) + 1U)) - 1U))
+
+/// Bit sequence manipulation double word (32 bits) test bits: Tests value x in of a bit range between a and b, b may NOT exceed 30 bits range.
+#define ISCSI_BITS_TST(x, a, b) ((x) & ISCSI_BITS_GET_MASK(a, b))
+
+/// Bit sequence manipulation double word (32 bits) get bits: Extracts a value x out of a bit range between a and b, b may NOT exceed 30 bits range.
+#define ISCSI_BITS_GET(x, a, b) (ISCSI_BITS_TST(x, a, b) >> (a))
+
+/// Bit sequence manipulation double word (32 bits) get bits: Puts a value x into a bit range between a and b, b may NOT exceed 30 bits range.
+#define ISCSI_BITS_PUT(x, a, b) (((x) << (a)) & ISCSI_BITS_GET_MASK(a, b))
+
+
+/// Aligns value x by rounding up, so it's evenly divisable by n.
+#define ISCSI_ALIGN(x, n) (((x) + (n) - 1) & ~((n) - 1))
+
+
+/// Determines the length of a zero terminated string at compile time.
+#define ISCSI_STRLEN(x) ((sizeof(x) / sizeof(uint8_t)) - 1)
+
+
+/* iSCSI protocol stuff (all WORD/DWORD/QWORD values are big endian by default
+   unless specified otherwise). */
+
+/// iSCSI Basic Header Segment (BHS) size.
+#define ISCSI_BHS_SIZE 48UL
+
+/// iSCSI Advanced Header Segment (AHS) maximum allowed size.
+#define ISCSI_MAX_AHS_SIZE (255UL << 2UL)
+
+/// iSCSI DataSegment maximum allowed size.
+#define ISCSI_MAX_DS_SIZE 16777215
+
+/// iSCSI packet data alignment (BHS, AHS and DataSegment).
+#define ISCSI_ALIGN_SIZE 4UL
+
+
+/// iSCSI Default receive DataSegment (DS) size in bytes.
+#define ISCSI_DEFAULT_RECV_DS_LEN 16384UL
+
+/// iSCSI default maximum DataSegment receive length in bytes.
+#define ISCSI_DEFAULT_MAX_RECV_DS_LEN 524288UL
+
+
+/// Current minimum iSCSI protocol version supported by this implementation.
+#define ISCSI_VERSION_MIN 0
+
+/// Current maximum iSCSI protocol version supported by this implementation.
+#define ISCSI_VERSION_MAX 0
+
+
+/// iSCSI initiator (client) command opcode: NOP-Out.
+#define ISCSI_OPCODE_CLIENT_NOP_OUT        0x00
+
+/// iSCSI initiator (client) command opcode: SCSI Command (encapsulates a SCSI Command Descriptor Block).
+#define ISCSI_OPCODE_CLIENT_SCSI_CMD       0x01
+
+/// iSCSI initiator (client) command opcode: SCSI Task Management Function Request.
+#define ISCSI_OPCODE_CLIENT_TASK_FUNC_REQ  0x02
+
+/// iSCSI initiator (client) command opcode: Login Request.
+#define ISCSI_OPCODE_CLIENT_LOGIN_REQ      0x03
+
+/// iSCSI initiator (client) command opcode: Text Request.
+#define ISCSI_OPCODE_CLIENT_TEXT_REQ       0x04
+
+/// iSCSI initiator (client) command opcode: SCSI Data-Out (for write operations).
+#define ISCSI_OPCODE_CLIENT_SCSI_DATA_OUT  0x05
+
+/// iSCSI initiator (client) command opcode: Logout Request.
+#define ISCSI_OPCODE_CLIENT_LOGOUT_REQ     0x06
+
+/// iSCSI initiator (client) command opcode: Selective Negative / Sequence Number Acknowledgment (SNACK) Request.
+#define ISCSI_OPCODE_CLIENT_SNACK_REQ      0x10
+
+/// iSCSI initiator (client) command opcode: Vendor-specific code #1.
+#define ISCSI_OPCODE_CLIENT_VENDOR_CODE1   0x1C
+
+/// iSCSI initiator (client) command opcode: Vendor-specific code #2.
+#define ISCSI_OPCODE_CLIENT_VENDOR_CODE2   0x1D
+
+/// iSCSI initiator (client) command opcode: Vendor-specific code #3.
+#define ISCSI_OPCODE_CLIENT_VENDOR_CODE3   0x1E
+
+/// First iSCSI initiator (client) command opcode.
+#define ISCSI_OPCODE_CLIENT_FIRST          0x00
+
+/// Last iSCSI initiator (client) command opcode.
+#define ISCSI_OPCODE_CLIENT_LAST           0x1F
+
+
+/// iSCSI target (server) command opcode: NOP-In.
+#define ISCSI_OPCODE_SERVER_NOP_IN         0x20
+
+/// iSCSI target (server) command opcode: SCSI Response - contains SCSI status and possibly sense information or other response information.
+#define ISCSI_OPCODE_SERVER_SCSI_RESPONSE  0x21
+
+/// iSCSI target (server) command opcode: SCSI Task Management Function Response.
+#define ISCSI_OPCODE_SERVER_TASK_FUNC_RES  0x22
+
+/// iSCSI target (server) command opcode: Login Response.
+#define ISCSI_OPCODE_SERVER_LOGIN_RES      0x23
+
+/// iSCSI target (server) command opcode: Text Response.
+#define ISCSI_OPCODE_SERVER_TEXT_RES       0x24
+
+/// iSCSI target (server) command opcode: SCSI Data-In (for read operations).
+#define ISCSI_OPCODE_SERVER_SCSI_DATA_IN   0x25
+
+/// iSCSI target (server) command opcode: Logout Response.
+#define ISCSI_OPCODE_SERVER_LOGOUT_RES     0x26
+
+/// iSCSI target (server) command opcode: Ready To Transfer (R2T) - sent by target when it is ready to receive data.
+#define ISCSI_OPCODE_SERVER_READY_XFER     0x31
+
+/// iSCSI target (server) command opcode: Asynchronous Message - sent by target to indicate certain special conditions.
+#define ISCSI_OPCODE_SERVER_ASYNC_MSG      0x32
+
+/// iSCSI target (server) command opcode: Vendor-specific code #1.
+#define ISCSI_OPCODE_SERVER_VENDOR_CODE1   0x3C
+
+/// iSCSI target (server) command opcode: Vendor-specific code #2.
+#define ISCSI_OPCODE_SERVER_VENDOR_CODE2   0x3D
+
+/// iSCSI target (server) command opcode: Vendor-specific code #3.
+#define ISCSI_OPCODE_SERVER_VENDOR_CODE3   0x3E
+
+/// iSCSI target (server) command opcode: Reject.
+#define ISCSI_OPCODE_SERVER_REJECT         0x3F
+
+
+/// First iSCSI target (server) command opcode.
+#define ISCSI_OPCODE_SERVER_FIRST          0x20
+
+/// Last iSCSI target (server) command opcode.
+#define ISCSI_OPCODE_SERVER_LAST           0x3F
+
+
+/// iSCSI opcode bit mask (bits 0-5 used).
+#define ISCSI_OPCODE_MASK           0x3F
+
+/// Macro which extracts iSCSI packet data opcode out of opcode byte.
+#define ISCSI_GET_OPCODE(x) ((x) & ISCSI_OPCODE_MASK)
+
+/// iSCSI opcode flags (I) Immediate bit: For Request PDUs, the I bit set to 1 is an immediate delivery marker.
+#define ISCSI_OPCODE_FLAGS_IMMEDIATE (1 << 6L)
+
+#define ASSERT_IS_BHS(structname) _Static_assert( sizeof(structname) == ISCSI_BHS_SIZE, #structname " messed up" )
+
+/**
+ * @brief iSCSI Basic Header Segment packet data.
+ *
+ * This structure contains the basic iSCSI packet
+ * data and is shared among all opcodes. This has
+ * to be used before the opcode of the packet data
+ * has been determined.
+ */
+typedef struct __attribute__((packed)) iscsi_bhs_packet {
+	/// Command opcode.
+	uint8_t opcode;
+
+	/// Opcode-specific fields.
+	uint8_t opcode_fields[3];
+
+	/// Total length of AHS (Advanced Header Segment).
+	uint8_t total_ahs_len;
+
+	/// Length of Data Segment.
+	uint8_t ds_len[3];
+
+	union {
+		/// SCSI LUN bit mask.
+		uint64_t lun;
+
+		/// Opcode-specific fields.
+		uint8_t opcode_spec[8];
+	} lun_opcode;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/// Opcode-specific fields.
+	uint8_t opcode_spec_fields[28];
+} iscsi_bhs_packet;
+ASSERT_IS_BHS( iscsi_bhs_packet );
+
+
+/**
+ * @brief iSCSI Advanced Header Segment packet data.
+ *
+ * This structure contains the advanced iSCSI packet
+ * data and is shared among all opcodes. This has
+ * to be used before the opcode of the packet data
+ * has been determined.
+ */
+typedef struct __attribute__((packed)) iscsi_ahs_packet {
+	/// AHSLength.
+	uint16_t len;
+
+	/// AHSType.
+	uint8_t type;
+
+	/// AHS-Specific.
+	uint8_t specific;
+} iscsi_ahs_packet;
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure.
+ *
+ * There are 16 bytes in the CDB field to accommodate the commonly used
+ * CDBs. Whenever the CDB is larger than 16 bytes, an Extended CDB AHS
+ * MUST be used to contain the CDB spillover.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Additional op-code specific data.
+	uint8_t data[15];
+} iscsi_scsi_cdb;
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for INQUIRY command flags: Enable Vital Product Data (EVPD).
+#define ISCSI_SCSI_CDB_INQUIRY_FLAGS_EVPD  (1 << 0)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for INQUIRY command flags: Command Support Data (CMDDT).
+#define ISCSI_SCSI_CDB_INQUIRY_FLAGS_CMDDT (1 << 1)
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI INQUIRY command.
+ *
+ * There are 6 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_inquiry {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Logical Unit Number (LUN), CMMDT and EVPD.
+	uint8_t lun_flags;
+
+	/// Page code.
+	uint8_t page_code;
+
+	/// Allocation length in bytes.
+	uint16_t alloc_len;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_inquiry;
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI READ(6) and WRITE(6) commands.
+ *
+ * There are 6 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_read_write_6 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Logical Block Address (LBA).
+	uint8_t lba[3];
+
+	/// Transfer length in bytes.
+	uint8_t xfer_len;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_read_write_6;
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI READ(10) and WRITE(10) commands.
+ *
+ * There are 10 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_read_write_10 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Logical Block Address (LBA).
+	uint32_t lba;
+
+	/// Group number.
+	uint8_t group_num;
+
+	/// Transfer length in bytes.
+	uint16_t xfer_len;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_read_write_10;
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI READ(12) and WRITE(12) commands.
+ *
+ * There are 12 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_read_write_12 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Logical Block Address (LBA).
+	uint32_t lba;
+
+	/// Transfer length in bytes.
+	uint32_t xfer_len;
+
+	/// Restricted for MMC-6 and group number.
+	uint8_t restrict_group_num;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_read_write_12;
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI READ(16) and WRITE(16) commands.
+ *
+ * There are 16 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_read_write_16 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Logical Block Address (LBA).
+	uint64_t lba;
+
+	/// Transfer length in bytes.
+	uint32_t xfer_len;
+
+	/// Restricted for MMC-6 and group number.
+	uint8_t restrict_group_num;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_read_write_16;
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for REPORT LUNS command select report: Logical unit with addressing method.
+#define ISCSI_SCSI_CDB_REPORT_LUNS_SELECT_REPORT_LU_ADDR_METHOD 0x00
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for REPORT LUNS command select report: Well known logical unit.
+#define ISCSI_SCSI_CDB_REPORT_LUNS_SELECT_REPORT_LU_KNOWN       0x01
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for REPORT LUNS command select report: Logical unit.
+#define ISCSI_SCSI_CDB_REPORT_LUNS_SELECT_REPORT_LU_ALL         0x02
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for REPORT LUNS command.
+ *
+ * There are 12 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_report_luns {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Select report.
+	uint8_t select_report;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint16_t reserved2;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved3;
+
+	/// Allocation length in bytes.
+	uint32_t alloc_len;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved4;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_report_luns;
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: READ CAPACITY(16).
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_READ_CAPACITY_16 0x10
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: READ LONG(16).
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_READ_LONG_16     0x11
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: First bit of the five bits.
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_FIRST_BIT        0
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: Last bit of the five bits.
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_LAST_BIT         ((ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_FIRST_BIT) + 5 - 1)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: Bit mask.
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_MASK             (ISCSI_BITS_GET_MASK(ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_FIRST_BIT, ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: Extracts the service action bits.
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_GET_ACTION(x)           (ISCSI_BITS_GET((x), ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_FIRST_BIT, ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for SERVICE ACTION IN(16) command service action: Stores into the service action bits.
+#define ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_PUT_ACTION(x)           (ISCSI_BITS_PUT((x), ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_FIRST_BIT, ISCSI_SCSI_CDB_SERVICE_ACTION_IN_16_ACTION_LAST_BIT))
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI SERVICE IN ACTION(16) command.
+ *
+ * There are 16 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_service_action_in_16 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Service action.
+	uint8_t action;
+
+	/// Logical Block Address (LBA), obselete by now.
+	uint64_t lba;
+
+	/// Allocation length in bytes.
+	uint32_t alloc_len;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_service_action_in_16;
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command flags: Disable Block Descriptors (DBD).
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_FLAGS_DBD (1 << 3)
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page code: First bit of the six bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_FIRST_BIT         0
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page code: Last bit of the six bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_LAST_BIT          ((ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_FIRST_BIT) + 6 - 1)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page code: Bit mask.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_MASK              (ISCSI_BITS_GET_MASK(ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page code: Extracts the page code bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_GET_PAGE_CODE(x)            (ISCSI_BITS_GET((x), ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page code: Stores into the page code bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PUT_PAGE_CODE(x)            (ISCSI_BITS_PUT((x), ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Current values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_CURRENT_VALUES 0x0
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Changeable values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_CHG_VALUES     0x1
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Default values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_DEFAULT_VALUES 0x2
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Saved values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_SAVED_VALUES   0x3
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: First bit of the two bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_FIRST_BIT      6
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Last bit of the two bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_LAST_BIT       ((ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_FIRST_BIT) + 2 - 1)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Bit mask.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_MASK           (ISCSI_BITS_GET_MASK(ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Extracts the page control bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_GET_PAGE_CONTROL(x)         (ISCSI_BITS_GET((x), ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(6) command page control: Stores into the page control bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_6_PUT_PAGE_CONTROL(x)         (ISCSI_BITS_PUT((x), ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_6_PAGE_CONTROL_LAST_BIT))
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI MODE SENSE(6) command.
+ *
+ * There are 6 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_mode_sense_6 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Page code and page control.
+	uint8_t page_code_control;
+
+	/// Sub page code.
+	uint8_t sub_page_code;
+
+	/// Allocation length in bytes.
+	uint8_t alloc_len;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_mode_sense_6;
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command flags: Disable Block Descriptors (DBD).
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_FLAGS_DBD   (1 << 3)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command flags: Long LBA Accepted (LLBAA).
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_FLAGS_LLBAA (1 << 4)
+
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page code: First bit of the six bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_FIRST_BIT         0
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page code: Last bit of the six bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_LAST_BIT          ((ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_FIRST_BIT) + 6 - 1)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page code: Bit mask.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_MASK              (ISCSI_BITS_GET_MASK(ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page code: Extracts the page code bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_GET_PAGE_CODE(x)            (ISCSI_BITS_GET((x), ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page code: Stores into the page code bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PUT_PAGE_CODE(x)            (ISCSI_BITS_PUT((x), ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Current values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_CURRENT_VALUES 0x0
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Changeable values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_CHG_VALUES     0x1
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Default values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_DEFAULT_VALUES 0x2
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Saved values.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_SAVED_VALUES   0x3
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: First bit of the two bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_FIRST_BIT      6
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Last bit of the two bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_LAST_BIT       ((ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_FIRST_BIT) + 2 - 1)
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Bit mask.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_MASK           (ISCSI_BITS_GET_MASK(ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Extracts the page control bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_GET_PAGE_CONTROL(x)         (ISCSI_BITS_GET((x), ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_LAST_BIT))
+
+/// iSCSI SCSI Command Descriptor Block (CDB) for MODE SENSE(10) command page control: Stores into the page control bits.
+#define ISCSI_SCSI_CDB_MODE_SENSE_10_PUT_PAGE_CONTROL(x)         (ISCSI_BITS_PUT((x), ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_FIRST_BIT, ISCSI_SCSI_CDB_MODE_SENSE_10_PAGE_CONTROL_LAST_BIT))
+
+
+/**
+ * @brief iSCSI SCSI CDB packet data structure for SCSI MODE SENSE(10) command.
+ *
+ * There are 10 bytes in the CDB field for this command.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cdb_mode_sense_10 {
+	/// SCSI opcode.
+	uint8_t opcode;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Page code and page control.
+	uint8_t page_code_control;
+
+	/// Sub page code.
+	uint8_t sub_page_code;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint16_t reserved;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved2;
+
+	/// Allocation length in bytes.
+	uint16_t alloc_len;
+
+	/// Control.
+	uint8_t control;
+} iscsi_scsi_cdb_mode_sense_10;
+
+
+/**
+ * @brief iSCSI SCSI DataSegment Command packet structure.
+ *
+ * iSCSI targets MUST support and enable Autosense. If Status is CHECK
+ * CONDITION (0x02), then the data segment MUST contain sense data for
+ * the failed command.
+ *
+ * For some iSCSI responses, the response data segment MAY contain some
+ * response-related information (e.g., for a target failure, it may
+ * contain a vendor-specific detailed description of the failure).
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_ds_cmd_data {
+	/// SenseLength: This field indicates the length of Sense Data.
+	uint16_t len;
+
+	/// The Sense Data contains detailed information about a CHECK CONDITION. SPC3 specifies the format and content of the Sense Data.
+	uint8_t sense_data[];
+} iscsi_scsi_ds_cmd_data;
+
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type: Direct access device.
+#define	ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_DIRECT    0x00
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type: First bit of the five bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT 0
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type: Last bit of the five bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT  ((ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT) + 5 - 1)
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type: Bit mask.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MASK      (ISCSI_BITS_GET_MASK(ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type: Extracts the peripheral device type bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_GET_PERIPHERAL_TYPE(x)    (ISCSI_BITS_GET((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type: Stores into the peripheral device type bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PUT_PERIPHERAL_TYPE(x)    (ISCSI_BITS_PUT((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: The specified peripheral device type is currently connected to this logical unit, or connection state could not be determined.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_POSSIBLE    0x0
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: The target is capable of supporting the specified peripheral device type on this logical unit, but not connected.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_SUPPORTED   0x1
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: The target is not capable of supporting a physical device on this logical unit.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_NEVER       0x3
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Vendor specific.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_VENDOR_UNIQ 0x4
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: First bit of the three bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT   5
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Last bit of the three bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT    ((ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT) + 3 - 1)
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Bit mask.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_MASK        (ISCSI_BITS_GET_MASK(ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Extracts the peripheral device identifier bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_GET_PERIPHERAL_ID(x)      (ISCSI_BITS_GET((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Stores into the peripheral device identifier bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PUT_PERIPHERAL_ID(x)      (ISCSI_BITS_PUT((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT))
+
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type modifier: First bit of the seven bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_FIRST_BIT             0
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type modifier: Last bit of the seven bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_LAST_BIT              ((ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_FIRST_BIT) + 7 - 1)
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type modifier: Bit mask.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_MASK                  (ISCSI_BITS_GET_MASK(ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Extracts the peripheral type modifier bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_GET_PERIPHERAL_TYPE_MOD(x)                (ISCSI_BITS_GET((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral identifier: Stores into the peripheral type modifier bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PUT_PERIPHERAL_TYPE_MOD(x)                (ISCSI_BITS_PUT((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data peripheral type modifier: Removable media.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PERIPHERAL_TYPE_MOD_FLAGS_REMOVABLE_MEDIA (1 << 7)
+
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: None.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_NONE       0x0
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: SPC.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_SPC        0x3
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: SPC2.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_SPC2       0x4
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: SPC3.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_SPC3       0x5
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: SPC4.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_SPC4       0x6
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: SPC5.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_SPC5       0x7
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: First bit of the three bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_FIRST_BIT  0
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: Last bit of the three bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_LAST_BIT   ((ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_FIRST_BIT) + 3 - 1)
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: Bit mask.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_MASK       (ISCSI_BITS_GET_MASK(ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: Extracts the ANSI version bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_GET_VERSION_ANSI(x)     (ISCSI_BITS_GET((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data ANSI version: Stores into the ANSI version bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PUT_VERSION_ANSI(x)     (ISCSI_BITS_PUT((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_VERSION_ANSI_LAST_BIT))
+
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: This structure complies with SCSI-1 specifications.
+#define	ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_LEVEL_0                0x00
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: This structure complies with CCS pseudo specifications.
+#define	ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_CCS                    0x01
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: This structure complies with SCSI-2/3 specifications.
+#define	ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_SCSI_2                 0x02
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: First bit of the four bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_FIRST_BIT              0
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Last bit of the four bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_LAST_BIT              ((ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_FIRST_BIT) + 4 - 1)
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Bit mask.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_MASK                  (ISCSI_BITS_GET_MASK(ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Extracts the response data format flags bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_GET_RESPONSE_DATA_FMT_FLAGS(x)                (ISCSI_BITS_GET((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Stores into the response data format flags bits.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_PUT_RESPONSE_DATA_FMT_FLAGS(x)                (ISCSI_BITS_PUT((x), ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_FIRST_BIT, ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_LAST_BIT))
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Hierarchical Support.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_HISUP                 (1 << 4)
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Normal ACA Supported.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_NORMACA               (1 << 5)
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: TERMINATE I/O PROCESS message device support.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_TERMINATE_IO_PROC_MSG (1 << 6)
+
+/// iSCSI SCSI Basic Inquiry Data response data format flags: Asynchronous Event Notification device support.
+#define ISCSI_SCSI_BASIC_INQUIRY_DATA_RESPONSE_DATA_FMT_FLAGS_ASYNC_EVENT_NOTIFY    (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI basic inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * cleared.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_basic_inquiry_data_packet {
+	/// Peripheral device type and qualifier.
+	uint8_t peripheral_type_id;
+
+	/// Peripheral device type modifier and removable media bit.
+	uint8_t peripheral_type_mod_flags;
+
+	/// ANSI-Approved, ECMA and ISO version.
+	uint8_t version;
+
+	/// Response data format, HISUP, NORMACA, AENC and TrmIOP flags.
+	uint8_t response_data_fmt_flags;
+
+	/// Additional length in bytes.
+	uint8_t add_len;
+} iscsi_scsi_basic_inquiry_data_packet;
+
+
+/// iSCSI SCSI Standard Inquiry Data vendor identifier for disk.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_DISK_VENDOR_ID "UNI FRBG"
+
+
+/// iSCSI SCSI Standard Inquiry Data services flags: Multi Port (MULTIP).
+#define ISCSI_SCSI_STD_INQUIRY_DATA_SERVICES_FLAGS_MULTIP  (1 << 4)
+
+/// iSCSI SCSI Standard Inquiry Data services flags: VS.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_SERVICES_FLAGS_VS      (1 << 5)
+
+/// iSCSI SCSI Standard Inquiry Data services flags: Enclosure Services (ENCSERV).
+#define ISCSI_SCSI_STD_INQUIRY_DATA_SERVICES_FLAGS_ENCSERV (1 << 6)
+
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device responds with soft reset instead of hard reset to reset condition.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_SOFT_RESET    (1 << 0)
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device supports tagged command queueing.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_COMMAND_QUEUE (1 << 1)
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device supports linked commands for this logical unit.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_LINKED_CMDS   (1 << 3)
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device supports synchronous data transfers.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_SYNC          (1 << 4)
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device supports 16-bit wide data transfers.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_WIDE_16_BIT   (1 << 5)
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device supports 32-bit wide data transfers.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_WIDE_32_BIT   (1 << 6)
+
+/// iSCSI SCSI Standard Inquiry Data flags: Device supports relative addressing mode of this logical unit.
+#define ISCSI_SCSI_STD_INQUIRY_DATA_FLAGS_REL_ADDR      (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI standard inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * cleared.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_std_inquiry_data_packet {
+	/// iSCSI SCSI basic inquiry data packet.
+	iscsi_scsi_basic_inquiry_data_packet basic_inquiry;
+
+	/// PROTECT, 3PC, TPGS, ACC and SCCS.
+	uint8_t tpgs_flags;
+
+	/// MULTIP, VS and ENCSERV.
+	uint8_t services_flags;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Vendor identification.
+	uint8_t vendor_id[8];
+
+	/// Product identification.
+	uint8_t product_id[16];
+
+	/// Product revision level.
+	uint8_t product_rev_level[4];
+} iscsi_scsi_std_inquiry_data_packet;
+
+
+/// iSCSI SCSI Extended Inquiry Data vendor specific.
+#define ISCSI_SCSI_EXT_INQUIRY_DATA_VENDOR_SPEC_ID "UNI FREIBURG DNBD3"
+
+
+/// iSCSI SCSI Extended Inquiry Data version descriptor: iSCSI (no version claimed).
+#define ISCSI_SCSI_EXT_INQUIRY_DATA_VERSION_DESC_ISCSI_NO_VERSION 0x0960
+
+/// iSCSI SCSI Extended Inquiry Data version descriptor: SPC3 (no version claimed).
+#define ISCSI_SCSI_EXT_INQUIRY_DATA_VERSION_DESC_SPC3_NO_VERSION  0x0300
+
+/// iSCSI SCSI Extended Inquiry Data version descriptor: SBC2 (no version claimed).
+#define ISCSI_SCSI_EXT_INQUIRY_DATA_VERSION_DESC_SBC2_NO_VERSION  0x0320
+
+/// iSCSI SCSI Extended Inquiry Data version descriptor: SAM2 (no version claimed).
+#define ISCSI_SCSI_EXT_INQUIRY_DATA_VERSION_DESC_SAM2_NO_VERSION  0x0040
+
+
+/**
+ * @brief iSCSI SCSI extended inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * cleared.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_ext_inquiry_data_packet {
+	/// iSCSI SCSI standard inquiry data packet.
+	iscsi_scsi_std_inquiry_data_packet std_inquiry;
+
+	/// Vendor specific.
+	uint8_t vendor_spec[20];
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint8_t reserved;
+
+	/// Version descriptors.
+	uint16_t version_desc[8];
+
+	/// Reserved for future usage (always MUST be 0).
+	uint64_t reserved2[2];
+
+	/// Reserved for future usage (always MUST be 0).
+	uint32_t reserved3;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint16_t reserved4;
+} iscsi_scsi_ext_inquiry_data_packet;
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral type: Direct access device.
+#define	ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_DIRECT    0x00
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral type: First bit of the five bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT 0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral type: Last bit of the five bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT  ((ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT) + 5 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral type: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_MASK      (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral type: Extracts the peripheral device type bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_GET_PERIPHERAL_TYPE(x)    (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral type: Stores into the peripheral device type bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PUT_PERIPHERAL_TYPE(x)    (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: The specified peripheral device type is currently connected to this logical unit, or connection state could not be determined.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_POSSIBLE    0x0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: The target is capable of supporting the specified peripheral device type on this logical unit, but not connected.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_SUPPORTED   0x1
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: The target is not capable of supporting a physical device on this logical unit.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_NEVER       0x3
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: Vendor specific.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_VENDOR_UNIQ 0x4
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: First bit of the three bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT   5
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: Last bit of the three bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT    ((ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT) + 3 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_MASK        (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: Extracts the peripheral device identifier bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_GET_PERIPHERAL_ID(x)      (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data peripheral identifier: Stores into the peripheral device identifier bits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PUT_PERIPHERAL_ID(x)      (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PERIPHERAL_ID_LAST_BIT))
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Supported VPD pages.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_SUPPORTED_VPD_PAGES      0x00
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Unit serial number.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_UNIT_SERIAL_NUMBER       0x80
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Device identification.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_DEVICE_ID                0x83
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Software interface identification.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_SOFTWARE_IFACE_ID        0x84
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Management network addresses.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_MANAGEMENT_NETWORK_ADDRS 0x85
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Extended inquiry data.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_EXTENDED_INQUIRY_DATA    0x86
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Mode page policy.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_MODE_PAGE_POLICY         0x87
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: SCSI ports.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_SCSI_PORTS               0x88
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Block limits.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_BLOCK_LIMITS             0xB0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Block device characteristics.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_BLOCK_DEV_CHARS          0xB1
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Inquiry Data page code: Thin provisioning.
+#define ISCSI_SCSI_VPD_PAGE_INQUIRY_DATA_PAGE_CODE_THIN_PROVISION           0xB2
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_inquiry_data_packet {
+	/// Peripheral device type and qualifier.
+	uint8_t peripheral_type_id;
+
+	/// Page code.
+	uint8_t page_code;
+
+	/// Allocation length in bytes.
+	uint16_t alloc_len;
+
+	/// Parameters.
+	uint8_t params[];
+} iscsi_scsi_vpd_page_inquiry_data_packet;
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data protocol identifier: iSCSI.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_ISCSI     0x05
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data protocol identifier: First bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_FIRST_BIT 4
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data protocol identifier: Last bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_LAST_BIT  ((ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_FIRST_BIT) + 8 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data protocol identifier: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_MASK      (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data protocol identifier: Extracts the protocol identifier bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_GET_PROTOCOL_ID(x)    (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data protocol identifier: Stores into the protocol identifier bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PUT_PROTOCOL_ID(x)    (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PROTOCOL_ID_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: Binary encoding.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_BINARY       0x01
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: ASCII encoding.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_ASCII        0x02
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: UTF-8 encoding.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_UTF8         0x03
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: First bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_FIRST_BIT    0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: Last bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_LAST_BIT     ((ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_FIRST_BIT) + 4 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_MASK         (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: Extracts the protocol identifier bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_GET_CODE_SET(x)       (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data code set: Stores into the protocol identifier bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_PUT_CODE_SET(x)       (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_CODE_SET_LAST_BIT))
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Vendor specific.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_VENDOR_SPEC        0x00
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: T10 vendor identifier.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_T10_VENDOR_ID      0x01
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: EUI64.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_EUI64              0x02
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: NAA.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_NAA                0x03
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Relative target port.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_REL_TARGET_PORT    0x04
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Target port group.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_TARGET_PORT_GROUP  0x05
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Logical unit group.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_LOGICAL_UNIT_GROUP 0x06
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: MD5 logical unit.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_MD5_LOGICAL_UNIT   0x07
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: SCSI name.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_SCSI_NAME          0x08
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: First bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_FIRST_BIT          0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Last bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_LAST_BIT           ((ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_FIRST_BIT) + 4 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_MASK               (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Extracts the type bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_GET_TYPE(x)             (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags type: Stores into the type bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_PUT_TYPE(x)             (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_TYPE_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Logical unit.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_LOGICAL_UNIT      0x0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Target port.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_TARGET_PORT       0x1
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Target device.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_TARGET_DEVICE     0x2
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: First bit of the two bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_FIRST_BIT         4
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Last bit of the two bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_LAST_BIT          ((ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_FIRST_BIT) + 6 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_MASK              (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Extracts the association bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_GET_ASSOC(x)            (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags association: Stores into the association bits.
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_PUT_ASSOC(x)            (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_ASSOC_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data flags: Protocol Identifier Valid (PIV).
+#define ISCSI_SCSI_VPD_PAGE_DESIGN_DESC_INQUIRY_DATA_FLAGS_PIV                     (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_design_desc_inquiry_data_packet {
+	/// Protocol identifier and code set.
+	uint8_t protocol_id_code_set;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint8_t reserved;
+
+	/// Length in bytes.
+	uint8_t len;
+
+	/// Designation descriptor.
+	uint8_t desc[];
+} iscsi_scsi_vpd_page_design_desc_inquiry_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor IEEE NAA Extended Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_design_desc_ieee_naa_ext_inquiry_data_packet {
+	/// IEEE NAA Extended.
+	uint64_t ieee_naa_ext;
+} iscsi_scsi_vpd_page_design_desc_ieee_naa_ext_inquiry_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor T10 Vendor ID Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_design_desc_t10_vendor_id_inquiry_data_packet {
+	/// Vendor identification.
+	uint8_t vendor_id[8];
+
+	/// Product identification.
+	uint8_t product_id[16];
+
+	/// Unit serial number.
+	uint8_t unit_serial_num[32];
+} iscsi_scsi_vpd_page_design_desc_t10_vendor_id_inquiry_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Relative Target Port Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_design_desc_rel_target_port_inquiry_data_packet {
+	/// Reserved for future usage (always MUST be 0).
+	uint16_t reserved;
+
+	/// Port index.
+	uint16_t index;
+} iscsi_scsi_vpd_page_design_desc_rel_target_port_inquiry_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Target Port Group Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_design_desc_target_port_group_inquiry_data_packet {
+	/// Reserved for future usage (always MUST be 0).
+	uint16_t reserved;
+
+	/// Port group index.
+	uint16_t index;
+} iscsi_scsi_vpd_page_design_desc_target_port_group_inquiry_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Designation Descriptor Logical Unit Group Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_design_desc_logical_unit_group_inquiry_data_packet {
+	/// Reserved for future usage (always MUST be 0).
+	uint16_t reserved;
+
+	/// Logical unit identifier.
+	uint16_t id;
+} iscsi_scsi_vpd_page_design_desc_logical_unit_group_inquiry_data_packet;
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Extended Inquiry Data support flags: SIMP support.
+#define ISCSI_SCSI_VPD_PAGE_EXT_INQUIRY_DATA_SUPPORT_FLAGS_SIMPSUP   (1 << 0)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Extended Inquiry Data support flags: HEAD support.
+#define ISCSI_SCSI_VPD_PAGE_EXT_INQUIRY_DATA_SUPPORT_FLAGS_HEADSUP   (1 << 2)
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Extended Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_ext_inquiry_data_packet {
+	/// Peripheral device type and qualifier.
+	uint8_t peripheral_type_id;
+
+	/// Page code.
+	uint8_t page_code;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint8_t reserved;
+
+	/// Page length in bytes.
+	uint8_t page_len;
+
+	/// Check flags.
+	uint8_t check_flags;
+
+	/// Support flags.
+	uint8_t support_flags;
+
+	/// More support flags.
+	uint8_t support_flags_2;
+
+	/// LUICLR.
+	uint8_t luiclr;
+
+	/// CBCS.
+	uint8_t cbcs;
+
+	/// Micro DL.
+	uint8_t micro_dl;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint64_t reserved2[6];
+
+	/// Reserved for future usage (always MUST be 0).
+	uint32_t reserved3;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint16_t reserved4;
+} iscsi_scsi_vpd_page_ext_inquiry_data_packet;
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Block Limits Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_block_limits_inquiry_data_packet {
+	/// Flags.
+	uint8_t flags;
+
+	/// Maximum COMPARE AND WRITE length in logical blocks.
+	uint8_t max_cmp_write_len;
+
+	/// Optimal transfer length granularity in logical blocks.
+	uint16_t optimal_granularity_xfer_len;
+
+	/// Maximum transfer length in logical blocks.
+	uint32_t max_xfer_len;
+
+	/// Optimal transfer length in logical blocks.
+	uint32_t optimal_xfer_len;
+
+	/// Maximum prefetch length in logical blocks.
+	uint32_t max_prefetch_len;
+
+	/// Maximum UNMAP LBA count in LBAs.
+	uint32_t max_unmap_lba_cnt;
+
+	/// Maximum UNMAP block descriptor count in block descriptors.
+	uint32_t max_unmap_block_desc_cnt;
+
+	/// Optimal UNMAP granularity in logical blocks.
+	uint32_t optimal_unmap_granularity;
+
+	/// UNMAP granularity alignment (first LBA) and UGAVALID bit.
+	uint32_t unmap_granularity_align_ugavalid;
+
+	/// Maximum WRITE SAME length in logical blocks.
+	uint64_t max_write_same_len;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint64_t reserved[2];
+
+	/// Reserved for future usage (always MUST be 0).
+	uint32_t reserved2;
+} iscsi_scsi_vpd_page_block_limits_inquiry_data_packet;
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data medium rotation rate: Medium rotation rate is not reported.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_MEDIUM_ROTATION_RATE_NOT_REPORTED 0x0000
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data medium rotation rate: Non-rotating medium (e.g., solid state).
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_MEDIUM_ROTATION_RATE_NONE         0x0001
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data product type: Not indicated.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_PRODUCT_TYPE_NOT_INDICATED       0x00
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data flags nominal form factor: Nominal form factor is not reported.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_NOT_REPORTED 0x0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data flags nominal form factor: First bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_FIRST_BIT    0
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data flags nominal form factor: Last bit of the four bits.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_LAST_BIT     ((ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_FIRST_BIT) + 4 - 1)
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data flags nominal form factor: Bit mask.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_MASK         (ISCSI_BITS_GET_MASK(ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data flags nominal form factor: Extracts the nominal form factor bits.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_GET_NOMINAL_FORM_FACTOR(x)       (ISCSI_BITS_GET((x), ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_LAST_BIT))
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data flags nominal form factor: Stores into the nominal form factor bits.
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_PUT_NOMINAL_FORM_FACTOR(x)       (ISCSI_BITS_PUT((x), ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_FIRST_BIT, ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_FLAGS_NOMINAL_FORM_FACTOR_LAST_BIT))
+
+
+/// iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data support flags: Verify Byte Check Unmapped LBA Supported (VBULS).
+#define ISCSI_SCSI_VPD_PAGE_BLOCK_DEV_CHARS_INQUIRY_DATA_SUPPORT_FLAGS_VBULS (1 << 0)
+
+
+/**
+ * @brief iSCSI SCSI Vital Product Data (VPD) Page Block Device Characteristics Inquiry data packet.
+ *
+ * This structure is used by the SCSI INQUIRY command
+ * in order to fill in the result if the EVPD bit is
+ * set.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_vpd_page_block_dev_chars_inquiry_data_packet {
+	/// Medium rotation rate.
+	uint16_t medium_rotation_rate;
+
+	/// Product type.
+	uint8_t product_type;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Support flags.
+	uint8_t support_flags;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint64_t reserved[6];
+
+	/// Reserved for future usage (always MUST be 0).
+	uint32_t reserved2;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint16_t reserved3;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint8_t reserved4;
+} iscsi_scsi_vpd_page_block_dev_chars_inquiry_data_packet;
+
+
+/// iSCSI SCSI sense data response code: Current format.
+#define ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_CURRENT_FMT  0x70
+
+/// iSCSI SCSI sense data response code: Deferred format.
+#define ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_DEFERRED_FMT 0x71
+
+/// iSCSI SCSI sense data response code: First bit of the seven bits.
+#define ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_FIRST_BIT    0
+
+/// iSCSI SCSI sense data response code: Last bit of the seven bits.
+#define ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_LAST_BIT     ((ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_FIRST_BIT) + 7 - 1)
+
+/// iSCSI SCSI sense data response code: Bit mask.
+#define ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_MASK         (ISCSI_BITS_GET_MASK(ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_FIRST_BIT, ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_LAST_BIT))
+
+/// iSCSI SCSI sense data response code: Extracts the response code bits.
+#define ISCSI_SCSI_SENSE_DATA_GET_RESPONSE_CODE(x)       (ISCSI_BITS_GET((x), ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_FIRST_BIT, ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_LAST_BIT))
+
+/// iSCSI SCSI sense data response code: Stores into the response code bits.
+#define ISCSI_SCSI_SENSE_DATA_PUT_RESPONSE_CODE(x)       (ISCSI_BITS_PUT((x), ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_FIRST_BIT, ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_LAST_BIT))
+
+/// iSCSI SCSI sense data response code: Valid.
+#define ISCSI_SCSI_SENSE_DATA_RESPONSE_CODE_VALID        (1 << 7)
+
+
+/// iSCSI SCSI sense data sense key: First bit of the four bits.
+#define ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FIRST_BIT   0
+
+/// iSCSI SCSI sense data sense key: Last bit of the four bits.
+#define ISCSI_SCSI_SENSE_DATA_SENSE_KEY_LAST_BIT   ((ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FIRST_BIT) + 4 - 1)
+
+/// iSCSI SCSI sense data sense key: Bit mask.
+#define ISCSI_SCSI_SENSE_DATA_SENSE_KEY_MASK (ISCSI_BITS_GET_MASK(ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FIRST_BIT, ISCSI_SCSI_SENSE_DATA_SENSE_KEY_LAST_BIT))
+
+/// iSCSI SCSI sense data sense key: Extracts the Sense Key (SK) bits.
+#define ISCSI_SCSI_SENSE_DATA_GET_SENSE_KEY(x) (ISCSI_BITS_GET((x), ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FIRST_BIT, ISCSI_SCSI_SENSE_DATA_SENSE_KEY_LAST_BIT))
+
+/// iSCSI SCSI sense data sense key: Stores into the Sense Key (SK) bits.
+#define ISCSI_SCSI_SENSE_DATA_PUT_SENSE_KEY(x) (ISCSI_BITS_PUT((x), ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FIRST_BIT, ISCSI_SCSI_SENSE_DATA_SENSE_KEY_LAST_BIT))
+
+// iSCSI SCSI sense data sense key flags: ILI.
+#define ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FLAGS_ILI      (1 << 5)
+
+// iSCSI SCSI sense data sense key flags: EOM.
+#define ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FLAGS_EOM      (1 << 6)
+
+// iSCSI SCSI sense data sense key flags: FILEMARK.
+#define ISCSI_SCSI_SENSE_DATA_SENSE_KEY_FLAGS_FILEMARK (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI basic sense data packet data.
+ *
+ * This is the basic SCSI sense data shared by
+ * all SCSI sense data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_sense_data_packet {
+	/// Response code.
+	uint8_t response_code;
+
+	/// Reserved for future usage (always MUST be 0).
+	uint8_t reserved;
+
+	/// Sense key and flags.
+	uint8_t sense_key_flags;
+
+	/// Information.
+	uint32_t info;
+
+	/// Additional sense length in bytes.
+	uint8_t add_len;
+} iscsi_scsi_sense_data_packet;
+
+/// iSCSI SCSI maximum sense data length.
+#define ISCSI_SCSI_MAX_SENSE_DATA_LEN (sizeof(struct iscsi_scsi_sense_data_packet) + 255U)
+
+
+/**
+ * @brief iSCSI SCSI sense data check condition packet data.
+ *
+ * This is the additional SCSI sense data used by
+ * the check condition status code.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_sense_data_check_cond_packet {
+	/// Basic SCSI sense data packet.
+	iscsi_scsi_sense_data_packet sense_data;
+
+	/// Information.
+	uint32_t cmd_spec_info;
+
+	/// Additional Sense Code (ASC).
+	uint8_t asc;
+
+	/// Additional Sense Code Qualifier (ASCQ).
+	uint8_t ascq;
+
+	/// Field replaceable unit code.
+	uint32_t field_rep_unit_code;
+
+	/// Sense key specific.
+	uint8_t sense_key_spec_flags;
+
+	/// Sense key specific.
+	uint16_t sense_key_spec;
+} iscsi_scsi_sense_data_check_cond_packet;
+
+
+/**
+ * @brief iSCSI SCSI command READ CAPACITY(10) parameter data packet data.
+ *
+ * This returns the Logical Block Address (LBA)
+ * and block length in bytes.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_read_capacity_10_parameter_data_packet {
+	/// Last valid Logical Block Address (LBA).
+	uint32_t lba;
+
+	/// Block length in bytes.
+	uint32_t block_len;
+} iscsi_scsi_read_capacity_10_parameter_data_packet;
+
+
+/// iSCSI SCSI command SERVICE ACTION IN(16) parameter data logical blocks per physical block exponent: First bit of the four bits.
+#define ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_FIRST_BIT 0
+
+/// iSCSI SCSI command SERVICE ACTION IN(16) parameter data logical blocks per physical block exponent: Last bit of the four bits.
+#define ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_LAST_BIT ((ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_FIRST_BIT) + 4 - 1)
+
+/// iSCSI SCSI command SERVICE ACTION IN(16) parameter data logical blocks per physical block exponent: Bit mask.
+#define ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_MASK     (ISCSI_BITS_GET_MASK(ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_FIRST_BIT, ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_LAST_BIT))
+
+/// iSCSI SCSI command SERVICE ACTION IN(16) parameter data logical blocks per physical block exponent: Extracts the logical blocks per physical block bits.
+#define ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_GET_LBPPB_EXPONENT(x)   (ISCSI_BITS_GET((x), ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_FIRST_BIT, ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_LAST_BIT))
+
+/// iSCSI SCSI command SERVICE ACTION IN(16) parameter data logical blocks per physical block exponent: Stores into the logical blocks per physical block bits.
+#define ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_PUT_LBPPB_EXPONENT(x)   (ISCSI_BITS_PUT((x), ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_FIRST_BIT, ISCSI_SCSI_SERVICE_ACTION_IN_16_PARAM_DATA_LBPPB_EXPONENT_LAST_BIT))
+
+
+/**
+ * @brief iSCSI SCSI command SERVICE ACTION IN(16) parameter data packet data.
+ *
+ * This returns the Logical Block Address (LBA),
+ * block length in bytes and LBP information.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_service_action_in_16_parameter_data_packet {
+	/// Last valid Logical Block Address (LBA).
+	uint64_t lba;
+
+	/// Block length in bytes.
+	uint32_t block_len;
+
+	/// Flags: RC_BASIS, P_TYPE and PROT_EN.
+	uint8_t flags;
+
+	/// P_I_EXPONENT and logical blocks per physical block exponent.
+	uint8_t exponents;
+
+	/// Logical Block Provisioning Management Enabled (LBPME), Logical Block Provisioning Read Zeros (LBPRZ) and Lowest Aligned Logical Block Address (LALBA).
+	uint16_t lbp_lalba;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint64_t reserved[2];
+} iscsi_scsi_service_action_in_16_parameter_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command REPORT LUNS parameter data LUN list packet data.
+ *
+ * This returns the number of entries in the
+ * LUN list in bytes.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_report_luns_parameter_data_lun_list_packet {
+	/// Number of LUN's following this packet in bytes.
+	uint32_t lun_list_len;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint32_t reserved;
+} iscsi_scsi_report_luns_parameter_data_lun_list_packet;
+
+
+/// iSCSI SCSI command MODE SENSE(6) parameter header data flags: DPO and FUA support (DPOFUA).
+#define ISCSI_SCSI_MODE_SENSE_6_PARAM_HDR_DATA_FLAGS_DPOFUA (1 << 4)
+
+/// iSCSI SCSI command MODE SENSE(6) parameter header data flags: Write Protect (WP).
+#define ISCSI_SCSI_MODE_SENSE_6_PARAM_HDR_DATA_FLAGS_WP     (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) parameter header packet data.
+ *
+ * This returns the mode parameter header
+ * data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_6_parameter_header_data_packet {
+	/// Mode data length in bytes.
+	uint8_t mode_data_len;
+
+	/// Medium type.
+	uint8_t medium_type;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Block descriptor length in bytes.
+	uint8_t block_desc_len;
+} iscsi_scsi_mode_sense_6_parameter_header_data_packet;
+
+
+/// iSCSI SCSI command MODE SENSE(10) parameter header data flags: DPO and FUA support (DPOFUA).
+#define ISCSI_SCSI_MODE_SENSE_10_PARAM_HDR_DATA_FLAGS_DPOFUA (1 << 4)
+
+/// iSCSI SCSI command MODE SENSE(10) parameter header data flags: Write Protect (WP).
+#define ISCSI_SCSI_MODE_SENSE_10_PARAM_HDR_DATA_FLAGS_WP     (1 << 7)
+
+
+/// iSCSI SCSI command MODE SENSE(10) parameter header data Long Logical Block Address (LONGLBA).
+#define ISCSI_SCSI_MODE_SENSE_10_PARAM_HDR_DATA_LONGLBA (1 << 0)
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(10) parameter header packet data.
+ *
+ * This returns the mode parameter header
+ * data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_10_parameter_header_data_packet {
+	/// Mode data length in bytes.
+	uint16_t mode_data_len;
+
+	/// Medium type.
+	uint8_t medium_type;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Long Logical Block Address (LONGLBA).
+	uint8_t long_lba;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Block descriptor length in bytes.
+	uint16_t block_desc_len;
+} iscsi_scsi_mode_sense_10_parameter_header_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) short LBA mode parameter block descriptor packet data.
+ *
+ * This returns the short Logical Block
+ * Address (LBA) mode parameter block
+ * descriptor data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_lba_parameter_block_desc_data_packet {
+	/// Number of blocks in logical blocks.
+	uint32_t num_blocks;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Logical blcok length in bytes.
+	uint8_t block_len[3];
+} iscsi_scsi_mode_sense_lba_parameter_block_desc_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(10) long LBA mode parameter block descriptor packet data.
+ *
+ * This returns the long Logical Block
+ * Address (LBA) mode parameter block
+ * descriptor data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_long_lba_parameter_block_desc_data_packet {
+	/// Number of blocks in logical blocks.
+	uint64_t num_blocks;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint32_t reserved;
+
+	/// Logical blcok length in bytes.
+	uint32_t block_len;
+} iscsi_scsi_mode_sense_long_lba_parameter_block_desc_data_packet;
+
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Vendor specific.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_VENDOR_SPEC                   0x00
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Read/Write error recovery.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_READ_WRITE_ERR_RECOVERY       0x01
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Disconnect / Reconnect.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_DISCONNECT_RECONNECT          0x02
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Format device.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_FORMAT_DEVICE                 0x03
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Rigid disk geometry.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_RIGID_DISK_GEOMETRY           0x04
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Rigid disk geometry.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_RIGID_DISK_GEOMETRY_2         0x05
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Verify error recovery.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_VERIFY_ERR_RECOVERY           0x07
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Caching.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_CACHING                       0x08
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Control.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_CONTROL                       0x0A
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Medium types supported.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_MEDIUM_TYPES_SUPPORTED        0x0B
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Notch and partition.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_NOTCH_AND_PARTITION           0x0C
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: XOR control.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_XOR_CONTROL                   0x10
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Enclosure services management.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_ENCLOSURE_SERVICES_MGMT       0x14
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Protocol specific LUN.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_PROTOCOL_SPEC_LUN             0x18
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Protocol specific Port.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_PROTOCOL_SPEC_PORT            0x19
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Power condition.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_POWER_COND                    0x1A
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Informational exceptions control.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_INFO_EXCEPTIOS_CONTROL        0x1C
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Report all mode pages.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_REPORT_ALL_MODE_PAGES         0x3F
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode sub page code: Control.
+#define ISCSI_SCSI_MODE_SENSE_MODE_SUB_PAGE_CODE_CONTROL                   0x00
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode sub page code: Control extension.
+#define ISCSI_SCSI_MODE_SENSE_MODE_SUB_PAGE_CODE_CONTROL_EXT               0x01
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode sub page code: All sub pages.
+#define ISCSI_SCSI_MODE_SENSE_MODE_SUB_PAGE_CODE_CONTROL_ALL               0xFF
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode sub page code: Report all mode pages.
+#define ISCSI_SCSI_MODE_SENSE_MODE_SUB_PAGE_CODE_REPORT_ALL_MODE_PAGES     0x00
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode sub page code: Report all mode pages and sub pages.
+#define ISCSI_SCSI_MODE_SENSE_MODE_SUB_PAGE_CODE_REPORT_ALL_MODE_SUB_PAGES 0xFF
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: First bit of the six bits.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_FIRST_BIT                     0
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Last bit of the six bits.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_LAST_BIT                      ((ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_FIRST_BIT) + 6 - 1)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Bit mask.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_MASK                          (ISCSI_BITS_GET_MASK(ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Extracts the page code bits.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_GET_PAGE_CODE(x)                   (ISCSI_BITS_GET((x), ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page code: Stores into the page code bits.
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_PUT_PAGE_CODE(x)                   (ISCSI_BITS_PUT((x), ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_FIRST_BIT, ISCSI_SCSI_MODE_SENSE_MODE_PAGE_CODE_LAST_BIT))
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page flags: Sub Page Format (SPF).
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_FLAGS_SPF                          (1 << 6)
+
+/// iSCSI SCSI command MODE SENSE(10) parameter header data flags: Parameters Saveable (PS).
+#define ISCSI_SCSI_MODE_SENSE_MODE_PAGE_FLAGS_PS                           (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_mode_page_data_header {
+	/// Page code and flags.
+	uint8_t page_code_flags;
+
+	/// Page length in bytes.
+	uint8_t page_len;
+} iscsi_scsi_mode_sense_mode_page_data_header;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) mode sub page packet data.
+ *
+ * This returns mode sub page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_mode_sub_page_data_header {
+	/// Page code and flags.
+	uint8_t page_code_flags;
+
+	/// Sub page code.
+	uint8_t sub_page_code;
+
+	/// Page length in bytes.
+	uint16_t page_len;
+} iscsi_scsi_mode_sense_mode_sub_page_data_header;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) read/write error recovery mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_read_write_err_recovery_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Read retry count.
+	uint8_t read_retry_cnt;
+
+	/// Obselete.
+	uint8_t obselete[3];
+
+	/// Restricted for MMC-6.
+	uint8_t restrict_mmc_6;
+
+	/// Write_retry count.
+	uint8_t write_retry_cnt;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Recovery time limit.
+	uint16_t recovery_time_limit;
+} iscsi_scsi_mode_sense_read_write_err_recovery_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) disconnect / reconnect mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_disconnect_reconnect_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint16_t reserved;
+
+	/// Bus inactivity time limit.
+	uint16_t bus_inactivity_time_limit;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint16_t reserved2;
+
+	/// Maximum connect time limit.
+	uint16_t max_connect_time_limit;
+
+	/// Maximum burst size.
+	uint16_t max_burst_size;
+
+	/// Restricted.
+	uint8_t restricted;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved3;
+
+	/// First burst size.
+	uint16_t first_burst_size;
+} iscsi_scsi_mode_sense_disconnect_reconnect_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) verify error recovery mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_verify_err_recovery_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Verify retry count.
+	uint8_t verify_retry_cnt;
+
+	/// Obselete.
+	uint8_t obselete;
+
+	/// Head offset count.
+	uint8_t head_offset_cnt;
+
+	/// Data strobe offset count.
+	uint8_t data_strobe_offset_cnt;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Write retry count.
+	uint8_t write_retry_cnt;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved2;
+
+	/// Verify_recovery time limit.
+	uint16_t verify_recovery_time_limit;
+} iscsi_scsi_mode_sense_verify_err_recovery_mode_page_data_packet;
+
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: READ Cache Disable (RCD).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_RCD  (1 << 0)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Multiplication factor (MF).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_MF   (1 << 1)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Write Cache Enable (WCE).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_WCE  (1 << 2)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Size Enable (SIZE).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_SIZE (1 << 3)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Discontinuity (DISC).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_DISC (1 << 4)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Caching Analysis Permitted (CAP).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_CAP  (1 << 5)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Abort Prefetch (ABPF).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_ABPF (1 << 6)
+
+/// iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page flags: Initiator Control (IC).
+#define ISCSI_SCSI_MODE_SENSE_CACHING_MODE_PAGE_FLAGS_IC   (1 << 7)
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) caching mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_caching_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Retention priority.
+	uint8_t retention_pri;
+
+	/// Disable prefetch transfer length.
+	uint16_t disable_prefetch_xfer_len;
+
+	/// Minimum prefetch.
+	uint16_t min_prefetch;
+
+	/// Maximum prefetch.
+	uint16_t max_prefetch;
+
+	/// Maximum prefetch ceiling.
+	uint16_t max_prefetch_ceil;
+
+	/// Cache flags.
+	uint8_t cache_flags;
+
+	/// Number of cache segments.
+	uint8_t num_cache_segs;
+
+	/// Cache segment size.
+	uint16_t cache_seg_size;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Obselete.
+	uint8_t obselete[3];
+} iscsi_scsi_mode_sense_caching_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) control mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_control_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Queue flags.
+	uint8_t queue_flags;
+
+	/// Control flags.
+	uint8_t control_flags;
+
+	/// Application task flags.
+	uint8_t app_task_flags;
+
+	/// Ready AER holdoff period.
+	uint16_t ready_aer_holdoff_period;
+
+	/// Busy timeout period.
+	uint16_t busy_timeout_period;
+
+	/// Extended self-test completition time.
+	uint16_t ext_self_test_complete_time;
+} iscsi_scsi_mode_sense_control_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) control extension mode sub page packet data.
+ *
+ * This returns mode sub page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_control_ext_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_sub_page_data_header mode_sub_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Initial command priority.
+	uint8_t init_cmd_pri;
+
+	/// Maximum sense data length in bytes.
+	uint8_t max_sense_data_len;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint64_t reserved[3];
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved2;
+} iscsi_scsi_mode_sense_control_ext_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) XOR extension mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_xor_ext_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved;
+
+	/// Maximum XOR write size in logical blocks.
+	uint32_t max_xor_write_size;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint32_t reserved2;
+
+	/// Maximum regenerate size in logical blocks.
+	uint32_t max_regenerate_size;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint32_t reserved3;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint16_t reserved4;
+
+	/// Rebuild delay.
+	uint16_t rebuild_delay;
+} iscsi_scsi_mode_sense_xor_ext_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) power condition mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_power_cond_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Idle and standby flags.
+	uint8_t idle_standby_flags;
+
+	/// idle_a condition timer.
+	uint32_t idle_a_cond_timer;
+
+	/// standby_z condition timer.
+	uint32_t standby_z_cond_timer;
+
+	/// idle_b condition timer.
+	uint32_t idle_b_cond_timer;
+
+	/// idle_c condition timer.
+	uint32_t idle_c_cond_timer;
+
+	/// standby_y condition timer.
+	uint32_t standby_y_cond_timer;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint64_t reserved;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint32_t reserved2;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint16_t reserved3;
+
+	/// Reserved for future usage (always MUST be 0 for now).
+	uint8_t reserved4;
+
+	/// Check Condition From (CCF) flags.
+	uint8_t ccf_flags;
+} iscsi_scsi_mode_sense_power_cond_mode_page_data_packet;
+
+
+/**
+ * @brief iSCSI SCSI command MODE SENSE(6) and MODE SENSE(10) informational exceptions control mode page packet data.
+ *
+ * This returns mode page specific data.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_mode_sense_info_exceptions_control_mode_page_data_packet {
+	/// Mode page.
+	iscsi_scsi_mode_sense_mode_page_data_header mode_page;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// Method Of Reporting Informational Exceptions (MRIE) flags.
+	uint8_t mrie;
+
+	/// Interval timer.
+	uint32_t interval_timer;
+
+	/// Report count.
+	uint32_t report_cnt;
+} iscsi_scsi_mode_sense_info_exceptions_control_mode_page_data_packet;
+
+
+
+/// SCSI command opcode (embedded in iSCSI protocol): TEST UNIT READY.
+#define ISCSI_SCSI_OPCODE_TESTUNITREADY          0x00
+
+/// SCSI command opcode (embedded in iSCSI protocol): REQUEST SENSE.
+#define ISCSI_SCSI_OPCODE_REQUESTSENSE           0x03
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ(6).
+#define ISCSI_SCSI_OPCODE_READ6                  0x08
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE(6).
+#define ISCSI_SCSI_OPCODE_WRITE6                 0x0A
+
+/// SCSI command opcode (embedded in iSCSI protocol): INQUIRY.
+#define ISCSI_SCSI_OPCODE_INQUIRY                0x12
+
+/// SCSI command opcode (embedded in iSCSI protocol): MODE SELECT(6).
+#define ISCSI_SCSI_OPCODE_MODESELECT6            0x15
+
+/// SCSI command opcode (embedded in iSCSI protocol): RESERVE(6).
+#define ISCSI_SCSI_OPCODE_RESERVE6               0x16
+
+/// SCSI command opcode (embedded in iSCSI protocol): RELEASE(6).
+#define ISCSI_SCSI_OPCODE_RELEASE6               0x17
+
+/// SCSI command opcode (embedded in iSCSI protocol): MODE SENSE(6).
+#define ISCSI_SCSI_OPCODE_MODESENSE6             0x1A
+
+/// SCSI command opcode (embedded in iSCSI protocol): START STOP UNIT.
+#define ISCSI_SCSI_OPCODE_STARTSTOPUNIT          0x1B
+
+/// SCSI command opcode (embedded in iSCSI protocol): PREVENT ALLOW MEDIUM REMOVAL.
+#define ISCSI_SCSI_OPCODE_PREVENTALLOW           0x1E
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ CAPACITY(10).
+#define ISCSI_SCSI_OPCODE_READCAPACITY10         0x25
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ(10).
+#define ISCSI_SCSI_OPCODE_READ10                 0x28
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE(10).
+#define ISCSI_SCSI_OPCODE_WRITE10                0x2A
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE AND VERIFY(10).
+#define ISCSI_SCSI_OPCODE_WRITE_VERIFY10         0x2E
+
+/// SCSI command opcode (embedded in iSCSI protocol): VERIFY(10).
+#define ISCSI_SCSI_OPCODE_VERIFY10               0x2F
+
+/// SCSI command opcode (embedded in iSCSI protocol): PRE-FETCH(10).
+#define ISCSI_SCSI_OPCODE_PREFETCH10             0x34
+
+/// SCSI command opcode (embedded in iSCSI protocol): SYNCHRONIZE CACHE(10).
+#define ISCSI_SCSI_OPCODE_SYNCHRONIZECACHE10     0x35
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ DEFECT DATA(10).
+#define ISCSI_SCSI_OPCODE_READ_DEFECT_DATA10     0x37
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE SAME(10).
+#define ISCSI_SCSI_OPCODE_WRITE_SAME10           0x41
+
+/// SCSI command opcode (embedded in iSCSI protocol): UNMAP.
+#define ISCSI_SCSI_OPCODE_UNMAP                  0x42
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ TOC/PMA/ATIP.
+#define ISCSI_SCSI_OPCODE_READTOC                0x43
+
+/// SCSI command opcode (embedded in iSCSI protocol): SANITIZE.
+#define ISCSI_SCSI_OPCODE_SANITIZE               0x48
+
+/// SCSI command opcode (embedded in iSCSI protocol): LOG SELECT.
+#define ISCSI_SCSI_OPCODE_LOGSELECT              0x4C
+
+/// SCSI command opcode (embedded in iSCSI protocol): LOG SENSE.
+#define ISCSI_SCSI_OPCODE_LOGSENSE               0x4D
+
+/// SCSI command opcode (embedded in iSCSI protocol): MODE SELECT(10).
+#define ISCSI_SCSI_OPCODE_MODESELECT10           0x55
+
+/// SCSI command opcode (embedded in iSCSI protocol): RESERVE(10).
+#define ISCSI_SCSI_OPCODE_RESERVE10              0x56
+
+/// SCSI command opcode (embedded in iSCSI protocol): RELEASE(10).
+#define ISCSI_SCSI_OPCODE_RELEASE10              0x57
+
+/// SCSI command opcode (embedded in iSCSI protocol): MODE SENSE(10).
+#define ISCSI_SCSI_OPCODE_MODESENSE10            0x5A
+
+/// SCSI command opcode (embedded in iSCSI protocol): PERSISTENT RESERVE IN.
+#define ISCSI_SCSI_OPCODE_PERSISTENT_RESERVE_IN  0x5E
+
+/// SCSI command opcode (embedded in iSCSI protocol): PERSISTENT RESERVE OUT.
+#define ISCSI_SCSI_OPCODE_PERSISTENT_RESERVE_OUT 0x5F
+
+/// SCSI command opcode (embedded in iSCSI protocol): Third-party Copy OUT.
+#define ISCSI_SCSI_OPCODE_EXTENDED_COPY          0x83
+
+/// SCSI command opcode (embedded in iSCSI protocol): Third-party Copy IN.
+#define ISCSI_SCSI_OPCODE_RECEIVE_COPY_RESULTS   0x84
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ(16).
+#define ISCSI_SCSI_OPCODE_READ16                 0x88
+
+/// SCSI command opcode (embedded in iSCSI protocol): COMPARE AND WRITE.
+#define ISCSI_SCSI_OPCODE_COMPARE_AND_WRITE      0x89
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE(16).
+#define ISCSI_SCSI_OPCODE_WRITE16                0x8A
+
+/// SCSI command opcode (embedded in iSCSI protocol): ORWRITE.
+#define ISCSI_SCSI_OPCODE_ORWRITE                0x8B
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE AND VERIFY(16).
+#define ISCSI_SCSI_OPCODE_WRITE_VERIFY16         0x8E
+
+/// SCSI command opcode (embedded in iSCSI protocol): VERIFY(16).
+#define ISCSI_SCSI_OPCODE_VERIFY16               0x8F
+
+/// SCSI command opcode (embedded in iSCSI protocol): PRE-FETCH(16).
+#define ISCSI_SCSI_OPCODE_PREFETCH16             0x90
+
+/// SCSI command opcode (embedded in iSCSI protocol): SYNCHRONIZE CACHE(16).
+#define ISCSI_SCSI_OPCODE_SYNCHRONIZECACHE16     0x91
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE SAME(16).
+#define ISCSI_SCSI_OPCODE_WRITE_SAME16           0x93
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE ATOMIC(16).
+#define ISCSI_SCSI_OPCODE_WRITE_ATOMIC16         0x9C
+
+/// SCSI command opcode (embedded in iSCSI protocol): SERVICE ACTION IN(16).
+#define ISCSI_SCSI_OPCODE_SERVICE_ACTION_IN_16   0x9E
+
+/// SCSI command opcode (embedded in iSCSI protocol): REPORT LUNS.
+#define ISCSI_SCSI_OPCODE_REPORTLUNS             0xA0
+
+/// SCSI command opcode (embedded in iSCSI protocol): MAINTENANCE IN.
+#define ISCSI_SCSI_OPCODE_MAINTENANCE_IN         0xA3
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ(12).
+#define ISCSI_SCSI_OPCODE_READ12                 0xA8
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE(12).
+#define ISCSI_SCSI_OPCODE_WRITE12                0xAA
+
+/// SCSI command opcode (embedded in iSCSI protocol): WRITE AND VERIFY(12).
+#define ISCSI_SCSI_OPCODE_WRITE_VERIFY12         0xAE
+
+/// SCSI command opcode (embedded in iSCSI protocol): VERIFY(12).
+#define ISCSI_SCSI_OPCODE_VERIFY12               0xAF
+
+/// SCSI command opcode (embedded in iSCSI protocol): READ DEFECT DATA(12).
+#define ISCSI_SCSI_OPCODE_READ_DEFECT_DATA12     0xB7
+
+
+/**
+ * @brief iSCSI SCSI command flags: No unsolicited data.
+ *
+ * (F) is set to 1 when no unsolicited SCSI Data-Out PDUs
+ * follow this PDU. When F = 1 for a write and if Expected
+ * Data Transfer Length is larger than the
+ * DataSegmentLength, the target may solicit additional data
+ * through R2T.
+ */
+#define ISCSI_SCSI_CMD_FLAGS_TASK_NO_UNSOLICITED_DATA   (1 << 7)
+
+
+/// SCSI SCSI command flags: Final.
+#define ISCSI_SCSI_CMD_FLAGS_FINAL                      (1 << 7)
+
+/**
+ * @brief iSCSI SCSI command flags: Expected input data.
+ *
+ * (R) is set to 1 when the command is expected to input data.
+ */
+#define ISCSI_SCSI_CMD_FLAGS_TASK_READ                  (1 << 6)
+
+/**
+ * @brief iSCSI SCSI command flags: Expected output data.
+ *
+ * (W) is set to 1 when the command is expected to output data.
+ */
+#define ISCSI_SCSI_CMD_FLAGS_TASK_WRITE                 (1 << 5)
+
+
+/// SCSI command flags task attribute: Untagged.
+#define ISCSI_SCSI_CMD_FLAGS_TASK_ATTR_UNTAGGED         0x0
+
+/// SCSI command flags task attribute: Simple.
+#define ISCSI_SCSI_CMD_FLAGS_TASK_ATTR_SIMPLE           0x1
+
+/// SCSI command flags task attribute: Ordered.
+#define ISCSI_SCSI_CMD_FLAGS_TASK_ATTR_ORDERED          0x2
+
+/// SCSI command flags task attribute: Head of queue.
+#define ISCSI_SCSI_CMD_FLAGS_TASK_ATTR_HEAD_QUEUE       0x3
+
+/// SCSI command flags task attribute: ACA.
+#define ISCSI_SCSI_CMD_FLAGS_TASK_ATTR_ACA              0x4
+
+/// SCSI command flags Task Attributes (ATTR) are encoded in the first three LSBs.
+#define ISCSI_SCSI_CMD_FLAGS_TASK_ATTR_MASK             0x7
+
+
+/**
+ * @brief iSCSI Flag and Task Attributes for SCSI command packet data.
+ *
+ * Flags and Task Attributes:
+ * At least one of the W and F bits MUST be set to 1.\n
+ * Either or both of R and W MAY be 1 when the Expected Data Transfer
+ * Length and/or the Bidirectional Read Expected Data Transfer Length
+ * are 0, but they MUST NOT both be 0 when the Expected Data Transfer
+ * Length and/or Bidirectional Read Expected Data Transfer Length are
+ * not 0 (i.e., when some data transfer is expected, the transfer
+ * direction is indicated by the R and/or W bit).
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_cmd_packet {
+	/// Always 1 according to the iSCSI specification.
+	uint8_t opcode;
+
+	/// Flags and Task Attributes.
+	uint8_t flags_task;
+
+	/// Reserved for future usage, MUST always be 0.
+	uint16_t reserved;
+
+	/// Total length of AHS.
+	uint8_t total_ahs_len;
+
+	/// Length of DataSegment.
+	uint8_t ds_len[3];
+
+	/// SCSI LUN bit mask.
+	uint64_t lun;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Expected Data Transfer Length.
+	 *
+	 * For unidirectional operations, the Expected Data Transfer Length
+	 * field contains the number of bytes of data involved in this SCSI
+	 * operation. For a unidirectional write operation (W flag set to 1 and
+	 * R flag set to 0), the initiator uses this field to specify the number
+	 * of bytes of data it expects to transfer for this operation. For a
+	 * unidirectional read operation (W flag set to 0 and R flag set to 1),
+	 * the initiator uses this field to specify the number of bytes of data
+	 * it expects the target to transfer to the initiator. It corresponds
+	 * to the SAM-2 byte count.\n
+	 * For bidirectional operations (both R and W flags are set to 1), this
+	 * field contains the number of data bytes involved in the write
+	 * transfer. For bidirectional operations, an additional header segment
+	 * MUST be present in the header sequence that indicates the
+	 * Bidirectional Read Expected Data Transfer Length. The Expected Data
+	 * Transfer Length field and the Bidirectional Read Expected Data
+	 * Transfer Length field correspond to the SAM-2 byte count.
+	 * If the Expected Data Transfer Length for a write and the length of
+	 * the immediate data part that follows the command (if any) are the
+	 * same, then no more data PDUs are expected to follow. In this case,
+	 * the F bit MUST be set to 1.\n
+	 * If the Expected Data Transfer Length is higher than the
+	 * FirstBurstLength (the negotiated maximum amount of unsolicited data
+	 * the target will accept), the initiator MUST send the maximum amount
+	 * of unsolicited data OR ONLY the immediate data, if any.
+	 * Upon completion of a data transfer, the target informs the initiator
+	 * (through residual counts) of how many bytes were actually processed
+	 * (sent and/or received) by the target.
+	 */
+	uint32_t exp_xfer_len;
+
+	/// The CmdSN enables ordered delivery across multiple connections in a single session.
+	uint32_t cmd_sn;
+
+	/// Command responses up to ExpStatSN - 1 (modulo 2**32) have been received (acknowledges status) on the connection.
+	uint32_t exp_stat_sn;
+
+	/**
+	 * @brief SCSI Command Descriptor Block (CDB).
+	 *
+	 * There are 16 bytes in the CDB field to accommodate the commonly used
+	 * CDBs. Whenever the CDB is larger than 16 bytes, an Extended CDB AHS
+	 * MUST be used to contain the CDB spillover.
+	 */
+	iscsi_scsi_cdb scsi_cdb;
+} iscsi_scsi_cmd_packet;
+
+
+/**
+ * @brief SCSI response flags: Residual Underflow.
+ *
+ * (U) set for Residual Underflow. In this case, the Residual
+ * Count indicates the number of bytes that were not
+ * transferred out of the number of bytes that were expected
+ * to be transferred. For a bidirectional operation, the
+ * Residual Count contains the residual for the write
+ * operation.
+ *
+ * Bits O and U and bits o and u are mutually exclusive (i.e., having
+ * both o and u or O and U set to 1 is a protocol error).
+ *
+ * For a response other than "Command Completed at Target", bits 3-6
+ * MUST be 0.
+ */
+#define ISCSI_SCSI_RESPONSE_FLAGS_RES_UNDERFLOW   (1 << 1)
+
+/**
+ * @brief SCSI response flags: Residual Overflow.
+ *
+ * (O) set for Residual Overflow. In this case, the Residual
+ * Count indicates the number of bytes that were not
+ * transferred because the initiator's Expected Data
+ * Transfer Length was not sufficient. For a bidirectional
+ * operation, the Residual Count contains the residual for
+ * the write operation.
+ *
+ * Bits O and U and bits o and u are mutually exclusive (i.e., having
+ * both o and u or O and U set to 1 is a protocol error).
+ *
+ * For a response other than "Command Completed at Target", bits 3-6
+ * MUST be 0.
+ */
+#define ISCSI_SCSI_RESPONSE_FLAGS_RES_OVERFLOW    (1 << 2)
+
+/**
+ * @brief SCSI response flags: Bidirectional Read Residual Underflow.
+ *
+ * (u) set for Bidirectional Read Residual Underflow. In this
+ * case, the Bidirectional Read Residual Count indicates the
+ * number of bytes that were not transferred to the
+ * initiator out of the number of bytes expected to be
+ * transferred.
+ *
+ * Bits O and U and bits o and u are mutually exclusive (i.e., having
+ * both o and u or O and U set to 1 is a protocol error).
+ *
+ * For a response other than "Command Completed at Target", bits 3-6
+ * MUST be 0.
+ */
+#define ISCSI_SCSI_RESPONSE_FLAGS_BIDI_READ_RES_UNDERFLOW   (1 << 3)
+
+/**
+ * @brief SCSI response flags: Bidirectional Read Residual Overflow.
+ *
+ + (o) set for Bidirectional Read Residual Overflow. In this
+ * case, the Bidirectional Read Residual Count indicates the
+ * number of bytes that were not transferred to the
+ * initiator because the initiator's Bidirectional Read
+ * Expected Data Transfer Length was not sufficient.
+ *
+ * Bits O and U and bits o and u are mutually exclusive (i.e., having
+ * both o and u or O and U set to 1 is a protocol error).
+ *
+ * For a response other than "Command Completed at Target", bits 3-6
+ * MUST be 0.
+ */
+#define ISCSI_SCSI_RESPONSE_FLAGS_BIDI_READ_RES_OVERFLOW    (1 << 4)
+
+/**
+ * @brief SCSI status response code: Good.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_GOOD          0x00
+
+/**
+ * @brief SCSI status response code: Check condition.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_CHECK_COND    0x02
+
+/**
+ * @brief SCSI status response code: Busy.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_BUSY          0x08
+
+/**
+ * @brief SCSI status response code: Residual conflict.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_RES_CONFLICT  0x18
+
+/**
+ * @brief SCSI status response code: Task set full.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_TASK_SET_FULL 0x28
+
+/**
+ * @brief SCSI status response code: ACA active.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_ACA_ACTIVE    0x30
+
+/**
+ * @brief SCSI status response code: Task aborted.
+ *
+ * The Status field is used to report the SCSI status of the command (as
+ * specified in SAM2) and is only valid if the response code is
+ * Command Completed at Target.
+ *
+ * If a SCSI device error is detected while data from the initiator is
+ * still expected (the command PDU did not contain all the data and the
+ * target has not received a data PDU with the Final bit set), the
+ * target MUST wait until it receives a data PDU with the F bit set in
+ * the last expected sequence before sending the Response PDU.
+ */
+#define ISCSI_SCSI_RESPONSE_STATUS_TASK_ABORTED  0x40
+
+
+/// SCSI response code: Command Completed at Target.
+#define ISCSI_SCSI_RESPONSE_CODE_OK              0x00
+
+/// SCSI response code: Target Failure.
+#define ISCSI_SCSI_RESPONSE_CODE_FAIL            0x01
+
+/**
+ * @brief iSCSI SCSI command response packet data.
+ *
+ * The Response field is used to report a service response. The mapping
+ * of the response code into a SCSI service response code value, if
+ * needed, is outside the scope of this document. However, in symbolic
+ * terms, response value 0x00 maps to the SCSI service response (see
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_response_packet {
+	/// Always 0x21 according to specification.
+	uint8_t opcode;
+
+	/// Flags.
+	uint8_t flags;
+
+	/// This field contains the iSCSI service response.
+	uint8_t response;
+
+	/// The Status field is used to report the SCSI status of the command (as specified in SAM2) and is only valid if the response code is Command Completed at Target.
+	uint8_t status;
+
+	/// Total AHS length.
+	uint8_t total_ahs_len;
+
+	/// Data segment length.
+	uint8_t ds_len[3];
+
+	/// Reserved for future usage. Always MUST be 0.
+	uint64_t reserved;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Copy of the last accepted Selective Negative / Sequence Number Acknowledgment (SNACK) tag.
+	 *
+	 * This field contains a copy of the SNACK Tag of the last SNACK Tag
+	 * accepted by the target on the same connection and for the command for
+	 * which the response is issued. Otherwise, it is reserved and should
+	 * be set to 0.\n
+	 * After issuing a R-Data SNACK, the initiator must discard any SCSI
+	 * status unless contained in a SCSI Response PDU carrying the same
+	 * SNACK Tag as the last issued R-Data SNACK for the SCSI command on the
+	 * current connection.
+	 */
+	uint32_t snack_tag;
+
+	/**
+	 * @brief StatSN - Status Sequence Number.
+	 *
+	 * The StatSN is a sequence number that the target iSCSI layer generates
+	 * per connection and that in turn enables the initiator to acknowledge
+	 * status reception. The StatSN is incremented by 1 for every
+	 * response/status sent on a connection, except for responses sent as a
+	 * result of a retry or SNACK. In the case of responses sent due to a
+	 * retransmission request, the StatSN MUST be the same as the first time
+	 * the PDU was sent, unless the connection has since been restarted.
+	 */
+	uint32_t stat_sn;
+
+	/**
+	 * @brief ExpCmdSN - Next Expected CmdSN from This Initiator.
+	 *
+	 * The ExpCmdSN is a sequence number that the target iSCSI returns to
+	 * the initiator to acknowledge command reception. It is used to update
+	 * a local variable with the same name. An ExpCmdSN equal to
+	 * MaxCmdSN + 1 indicates that the target cannot accept new commands.
+	 */
+	uint32_t exp_cmd_sn;
+
+	/**
+	 * @brief MaxCmdSN - Maximum CmdSN from This Initiator.
+	 *
+	 * The MaxCmdSN is a sequence number that the target iSCSI returns to
+	 * the initiator to indicate the maximum CmdSN the initiator can send.
+	 * It is used to update a local variable with the same name. If the
+	 * MaxCmdSN is equal to ExpCmdSN - 1, this indicates to the initiator
+	 * that the target cannot receive any additional commands. When the
+	 * MaxCmdSN changes at the target while the target has no pending PDUs
+	 * to convey this information to the initiator, it MUST generate a
+	 * NOP-In to carry the new MaxCmdSN.
+	 */
+	uint32_t max_cmd_sn;
+
+	/**
+	 * @brief ExpDataSN or Reserved.
+	 *
+	 * This field indicates the number of Data-In (read) PDUs the target has
+	 * sent for the command.\n
+	 * This field MUST be 0 if the response code is not Command Completed at
+	 * Target or the target sent no Data-In PDUs for the command.
+	 */
+	uint32_t exp_data_sn;
+
+	/**
+	 * @brief Bidirectional Read Residual Count or Reserved.
+	 *
+	 * The Bidirectional Read Residual Count field MUST be valid in the case
+	 * where either the u bit or the o bit is set. If neither bit is set,
+	 * the Bidirectional Read Residual Count field is reserved. Targets may
+	 * set the Bidirectional Read Residual Count, and initiators may use it
+	 * when the response code is Command Completed at Target. If the o bit
+	 * is set, the Bidirectional Read Residual Count indicates the number of
+	 * bytes that were not transferred to the initiator because the
+	 * initiator's Bidirectional Read Expected Data Transfer Length was not
+	 * sufficient. If the u bit is set, the Bidirectional Read Residual
+	 * Count indicates the number of bytes that were not transferred to the
+	 * initiator out of the number of bytes expected to be transferred.
+	 */
+	uint32_t bidi_read_res_cnt;
+
+	/**
+	 * @brief Residual Count or Reserved.
+	 *
+	 * The Residual Count field MUST be valid in the case where either the U
+	 * bit or the O bit is set. If neither bit is set, the Residual Count
+	 * field MUST be ignored on reception and SHOULD be set to 0 when
+	 * sending. Targets may set the residual count, and initiators may use
+	 * it when the response code is Command Completed at Target (even if the
+	 * status returned is not GOOD). If the O bit is set, the Residual
+	 * Count indicates the number of bytes that were not transferred because
+	 * the initiator's Expected Data Transfer Length was not sufficient. If
+	 * the U bit is set, the Residual Count indicates the number of bytes
+	 * that were not transferred out of the number of bytes expected to be
+	 * transferred.
+	 */
+	uint32_t res_cnt;
+} iscsi_scsi_response_packet;
+
+
+/**
+ * @brief iSCSI Task Management Function Request packet data.
+ *
+ * This structure is used to explicity control the execution of one
+ * or more tasks (iSCSI and SCSI).
+ */
+typedef struct __attribute__((packed)) iscsi_task_mgmt_func_req_packet {
+    /// Always 2 according to iSCSI specification.
+    uint8_t opcode;
+
+    /**
+     * @brief Function.
+     *
+     * The task management functions provide an initiator with a way to
+     * explicitly control the execution of one or more tasks (SCSI and iSCSI
+     * tasks). The task management function codes are listed below. For a
+     * more detailed description of SCSI task management, see SAM2.
+     */
+    uint8_t func;
+
+    /// Reserved fot future usage, always MUST be 0.
+    uint16_t reserved;
+
+    /// TotalAHSLength (MUST be 0 for this PDU).
+    uint8_t total_ahs_len;
+
+    /// DataSegmentLength (MUST be 0 for this PDU).
+    uint8_t ds_len[3];
+
+    /**
+     * @brief Logical Unit Number (LUN) or Reserved.
+     *
+     * This field is required for functions that address a specific LU
+     * (ABORT TASK, CLEAR TASK SET, ABORT TASK SET, CLEAR ACA, LOGICAL UNIT
+     * RESET) and is reserved in all others
+     */
+    uint64_t lun;
+
+    /**
+     * @brief Initiator Task Tag (ITT).
+     *
+     * This is the Initiator Task Tag of the task to be aborted for the
+     * ABORT TASK function or reassigned for the TASK REASSIGN function.
+     * For all the other functions, this field MUST be set to the reserved
+     * value 0xFFFFFFFF.
+     */
+    uint32_t init_task_tag;
+
+    /// Referenced task tag or 0xFFFFFFFF.
+    uint32_t ref_task_tag;
+
+    /// CmdSN.
+    uint32_t cmd_sn;
+
+    /// ExpStatSN
+    uint32_t exp_stat_sn;
+
+    /**
+     * @brief RefCmdSN or Reserved.
+     *
+     * If an ABORT TASK is issued for a task created by an immediate
+     * command, then the RefCmdSN MUST be that of the task management
+     * request itself (i.e., the CmdSN and RefCmdSN are equal).\n
+     * For an ABORT TASK of a task created by a non-immediate command, the
+     * RefCmdSN MUST be set to the CmdSN of the task identified by the
+     * Referenced Task Tag field. Targets must use this field when the task
+     * identified by the Referenced Task Tag field is not with the target.
+     * Otherwise, this field is reserved.
+     */
+    uint32_t ref_cmd_sn;
+
+    /**
+     * @brief ExpDataSN or Reserved.
+     *
+     * For recovery purposes, the iSCSI target and initiator maintain a data
+     * acknowledgment reference number - the first input DataSN number
+     * unacknowledged by the initiator. When issuing a new command, this
+     * number is set to 0. If the function is TASK REASSIGN, which
+     * establishes a new connection allegiance for a previously issued read
+     * or bidirectional command, the ExpDataSN will contain an updated data
+     * acknowledgment reference number or the value 0; the latter indicates
+     * that the data acknowledgment reference number is unchanged. The
+     * initiator MUST discard any data PDUs from the previous execution that
+     * it did not acknowledge, and the target MUST transmit all Data-In PDUs
+     * (if any) starting with the data acknowledgment reference number. The
+     * number of retransmitted PDUs may or may not be the same as the
+     * original transmission, depending on if there was a change in
+     * MaxRecvDataSegmentLength in the reassignment. The target MAY also
+     * send no more Data-In PDUs if all data has been acknowledged.
+     * The value of ExpDataSN MUST be 0 or higher than the DataSN of the
+     * last acknowledged Data-In PDU, but not larger than DataSN + 1 of the
+     * last Data-IN PDU sent by the target. Any other value MUST be ignored
+     * by the target.
+     * For other functions, this field is reserved
+     */
+    uint32_t exp_data_sn;
+
+    /// Reserved for future usage, always MUST be 0.
+    uint64_t reserved2;
+} iscsi_task_mgmt_func_req_packet;
+
+
+/// Task management function response: Function complete.
+#define ISCSI_TASK_MGMT_FUNC_RESPONSE_FUNC_COMPLETE               0x00
+
+/**
+ * @brief iSCSI Task Management Function Response packet data.
+ *
+ * For the functions ABORT TASK, ABORT TASK SET, CLEAR ACA, CLEAR TASK
+ * SET, LOGICAL UNIT RESET, TARGET COLD RESET, TARGET WARM RESET, and
+ * TASK REASSIGN, the target performs the requested task management
+ * function and sends a task management response back to the initiator.
+ * For TASK REASSIGN, the new connection allegiance MUST ONLY become
+ * effective at the target after the target issues the task management
+ * response.
+ */
+typedef struct __attribute__((packed)) iscsi_task_mgmt_func_response_packet {
+    /// Always 0x22 according to specification.
+    uint8_t opcode;
+
+    /// Reserved for future usage (always MUST be 0x80 for now).
+    uint8_t flags;
+
+    /**
+     * @brief Function response.
+     *
+     * For the TARGET COLD RESET and TARGET WARM RESET functions, the target
+     * cancels all pending operations across all LUs known to the issuing
+     * initiator. For the TARGET COLD RESET function, the target MUST then
+     * close all of its TCP connections to all initiators (terminates all
+     * sessions).\n
+     * The mapping of the response code into a SCSI service response code
+     * value, if needed, is outside the scope of this document. However, in
+     * symbolic terms, Response values 0 and 1 map to the SCSI service
+     * response of FUNCTION COMPLETE. Response value 2 maps to the SCSI
+     * service response of INCORRECT LOGICAL UNIT NUMBER. All other
+     * Response values map to the SCSI service response of FUNCTION
+     * REJECTED. If a Task Management Function Response PDU does not arrive
+     * before the session is terminated, the SCSI service response is
+     * SERVICE DELIVERY OR TARGET FAILURE.\n
+     * The response to ABORT TASK SET and CLEAR TASK SET MUST only be issued
+     * by the target after all of the commands affected have been received
+     * by the target, the corresponding task management functions have been
+     * executed by the SCSI target, and the delivery of all responses
+     * delivered until the task management function completion has been
+     * confirmed (acknowledged through the ExpStatSN) by the initiator on
+     * all connections of this session.\n
+     * For the ABORT TASK function,\n
+     * -# if the Referenced Task Tag identifies a valid task leading to a
+     *    successful termination, then targets must return the "Function
+     *    complete" response.
+     * -# if the Referenced Task Tag does not identify an existing task
+     *    but the CmdSN indicated by the RefCmdSN field in the Task
+     *    Management Function Request is within the valid CmdSN window
+     *    and less than the CmdSN of the Task Management Function Request
+     *    itself, then targets must consider the CmdSN as received and
+     *    return the "Function complete" response.
+     * -# if the Referenced Task Tag does not identify an existing task
+     *    and the CmdSN indicated by the RefCmdSN field in the Task
+     *    Management Function Request is outside the valid CmdSN window,
+     *    then targets must return the "Task does not exist" response
+     */
+    uint8_t response;
+
+    /// Reserved for future usage, always MUST be 0.
+    uint8_t reserved;
+
+    /// TotalAHSLength (MUST be 0 for this PDU).
+    uint8_t total_ahs_len;
+
+    /// DataSegmentLength (MUST be 0 for this PDU).
+    uint8_t ds_len[3];
+
+    /// Reserved for future usage, always MUST be 0.
+    uint64_t reserved2;
+
+    /// Initiator Task Tag (ITT).
+    uint32_t init_task_tag;
+
+    /// Reserved for future usage, always MUST be 0.
+    uint32_t reserved3;
+
+    /// StatSN.
+    uint32_t stat_sn;
+
+    /// ExpCmdSN.
+    uint32_t exp_cmd_sn;
+
+    /// MaxCmdSN.
+    uint32_t max_cmd_sn;
+
+    /// Reserved for future usage, always MUST be 0.
+    uint32_t reserved4;
+
+    /// Reserved for future usage, always MUST be 0.
+    uint64_t reserved5;
+} iscsi_task_mgmt_func_response_packet;
+
+/**
+ * @brief SCSI Data In reponse flags: Status.
+ *
+ * (S) set to indicate that the Command Status field
+ * contains status. If this bit is set to 1, the
+ * F bit MUST also be set to 1.
+ */
+#define ISCSI_SCSI_DATA_IN_RESPONSE_FLAGS_STATUS        (1 << 0)
+
+/**
+ * @brief SCSI Data In reponse flags: Residual Underflow.
+ *
+ * (U) set for Residual Underflow. In this case, the Residual
+ * Count indicates the number of bytes that were not
+ * transferred out of the number of bytes that were expected
+ * to be transferred. For a bidirectional operation, the
+ * Residual Count contains the residual for the write
+ * operation.
+ */
+#define ISCSI_SCSI_DATA_IN_RESPONSE_FLAGS_RES_UNDERFLOW (1 << 1)
+
+/**
+ * @brief SCSI Data In reponse flags: Residual Overflow.
+ *
+ * (O) set for Residual Overflow. In this case, the Residual
+ * Count indicates the number of bytes that were not
+ * transferred because the initiator's Expected Data
+ * Transfer Length was not sufficient. For a bidirectional
+ * operation, the Residual Count contains the residual for
+ * the write operation.
+ */
+#define ISCSI_SCSI_DATA_IN_RESPONSE_FLAGS_RES_OVERFLOW  (1 << 2)
+
+/**
+ * @brief SCSI Data In reponse flags: ACK.
+ *
+ * (A) for sessions with ErrorRecoveryLevel=1 or higher, the target sets
+ * this bit to 1 to indicate that it requests a positive acknowledgment
+ * from the initiator for the data received. The target should use the
+ * A bit moderately; it MAY only set the A bit to 1 once every
+ * MaxBurstLength bytes, or on the last Data-In PDU that concludes the
+ * entire requested read data transfer for the task from the target's
+ * perspective, and it MUST NOT do so more frequently. The target MUST
+ * NOT set to 1 the A bit for sessions with ErrorRecoveryLevel=0. The
+ * initiator MUST ignore the A bit set to 1 for sessions with
+ * ErrorRecoveryLevel=0.\n
+ * On receiving a Data-In PDU with the A bit set to 1 on a session with
+ * ErrorRecoveryLevel greater than 0, if there are no holes in the read
+ * data until that Data-In PDU, the initiator MUST issue a SNACK of type
+ * DataACK, except when it is able to acknowledge the status for the
+ * task immediately via the ExpStatSN on other outbound PDUs if the
+ * status for the task is also received. In the latter case
+ * (acknowledgment through the ExpStatSN), sending a SNACK of type
+ * DataACK in response to the A bit is OPTIONAL, but if it is done, it
+ * must not be sent after the status acknowledgment through the
+ * ExpStatSN. If the initiator has detected holes in the read data
+ * prior to that Data-In PDU, it MUST postpone issuing the SNACK of type
+ * DataACK until the holes are filled. An initiator also MUST NOT
+ * acknowledge the status for the task before those holes are filled. A
+ * status acknowledgment for a task that generated the Data-In PDUs is
+ * considered by the target as an implicit acknowledgment of the Data-In
+ * PDUs if such an acknowledgment was requested by the target.
+ */
+#define ISCSI_SCSI_DATA_IN_RESPONSE_FLAGS_ACK           (1 << 6)
+
+/**
+ * @brief SCSI Data In reponse flags: Final.
+ *
+ * (F) for outgoing data, this bit is 1 for the last PDU of unsolicited
+ * data or the last PDU of a sequence that answers an R2T.
+ * For incoming data, this bit is 1 for the last input (read) data PDU
+ * of a sequence. Input can be split into several sequences, each
+ * having its own F bit. Splitting the data stream into sequences does
+ * not affect DataSN counting on Data-In PDUs. It MAY be used as a
+ * "change direction" indication for bidirectional operations that need
+ * such a change.\n
+ * DataSegmentLength MUST NOT exceed MaxRecvDataSegmentLength for the
+ * direction it is sent, and the total of all the DataSegmentLength of
+ * all PDUs in a sequence MUST NOT exceed MaxBurstLength (or
+ * FirstBurstLength for unsolicited data). However, the number of
+ * individual PDUs in a sequence (or in total) may be higher than the
+ * ratio of MaxBurstLength (or FirstBurstLength) to
+ * MaxRecvDataSegmentLength (as PDUs may be limited in length by the
+ * capabilities of the sender). Using a DataSegmentLength of 0 may
+ * increase beyond what is reasonable for the number of PDUs and should
+ * therefore be avoided.\n
+ * For bidirectional operations, the F bit is 1 for both the end of the
+ * input sequences and the end of the output sequences
+ */
+#define ISCSI_SCSI_DATA_IN_RESPONSE_FLAGS_FINAL         (1 << 7)
+
+/**
+ * @brief iSCSI SCSI Data In response packet data.
+ *
+ * THis structure is used by iSCSI for SCSI data input
+ * responses, i.e. read operations.
+ */
+typedef struct __attribute__((packed)) iscsi_scsi_data_in_response_packet {
+	/// Always 0x25 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Incoming data flags. The fields StatSN, Status, and Residual Count only have meaningful content if the S bit is set to 1.
+	uint8_t flags;
+
+	/// Rserved for future usage, always MUST be 0.
+	uint8_t reserved;
+
+	/**
+	 * @brief Status or Reserved.
+	 *
+	 * Status can accompany the last Data-In PDU if the command did not end
+	 * with an exception (i.e., the status is "good status" - GOOD,
+	 * CONDITION MET, or INTERMEDIATE-CONDITION MET). The presence of
+	 * status (and of a residual count) is signaled via the S flag bit.
+	 * Although targets MAY choose to send even non-exception status in
+	 * separate responses, initiators MUST support non-exception status in
+	 * Data-In PDUs.
+	 */
+	uint8_t status;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/**
+	 * @brief DataSegmentLength.
+	 *
+	 * This is the data payload length of a SCSI Data-In or SCSI Data-Out
+	 * PDU. The sending of 0-length data segments should be avoided, but
+	 * initiators and targets MUST be able to properly receive 0-length data
+	 * segments.\n
+	 * The data segments of Data-In and Data-Out PDUs SHOULD be filled to
+	 * the integer number of 4-byte words (real payload), unless the F bit
+	 * is set to 1.
+	 */
+	uint8_t ds_len[3];
+
+	/**
+	 * @brief Logical Unit Number (LUN) or Reserved.
+	 *
+	 * If the Target Transfer Tag is provided, then the LUN field MUST hold a
+	 * valid value and be consistent with whatever was specified with the command;
+	 * otherwise, the LUN field is reserved.
+	 */
+	uint64_t lun;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Target Transfer Tag or 0xFFFFFFFF.
+	 *
+	 * On incoming data, the Target Transfer Tag and LUN MUST be provided by
+	 * the target if the A bit is set to 1; otherwise, they are reserved.
+	 * The Target Transfer Tag and LUN are copied by the initiator into the
+	 * SNACK of type DataACK that it issues as a result of receiving a SCSI
+	 * Data-In PDU with the A bit set to 1.\n
+	 * The Target Transfer Tag values are not specified by this protocol,
+	 * except that the value 0xFFFFFFFF is reserved and means that the
+	 * Target Transfer Tag is not supplied.
+	 */
+	uint32_t target_xfer_tag;
+
+	/// StatSN.
+	uint32_t stat_sn;
+
+	/// ExpCmdSN.
+
+	uint32_t exp_cmd_sn;
+
+	/// MaxCmdSN.
+	uint32_t max_cmd_sn;
+
+	/**
+	 * @brief DataSN.
+	 *
+	 * For input (read) or bidirectional Data-In PDUs, the DataSN is the
+	 * input PDU number within the data transfer for the command identified
+	 * by the Initiator Task Tag.\n
+	 * R2T and Data-In PDUs, in the context of bidirectional commands, share
+	 * the numbering sequence.
+	 */
+	uint32_t data_sn;
+
+	/**
+	 * @brief Buffer Offset.
+	 *
+	 * The Buffer Offset field contains the offset of this PDU payload data
+	 * within the complete data transfer. The sum of the buffer offset and
+	 * length should not exceed the expected transfer length for the
+	 * command.\n
+	 * The order of data PDUs within a sequence is determined by
+	 * DataPDUInOrder. When set to Yes, it means that PDUs have to be in
+	 * increasing buffer offset order and overlays are forbidden.\n
+	 * The ordering between sequences is determined by DataSequenceInOrder.
+	 * When set to Yes, it means that sequences have to be in increasing
+	 * buffer offset order and overlays are forbidden.
+	 */
+	uint32_t buf_offset;
+
+	/// Residual Count or Reserved.
+	uint32_t res_cnt;
+} iscsi_scsi_data_in_response_packet;
+
+/**
+ * @brief Text Request flags: Continue.
+ *
+ * (C) When set to 1, this bit indicates that the text (set of key=value
+ * pairs) in this Text Request is not complete (it will be continued on
+ * subsequent Text Requests); otherwise, it indicates that this Text
+ * Request ends a set of key=value pairs. A Text Request with the C bit
+ * set to 1 MUST have the F bit set to 0.
+ */
+#define ISCSI_TEXT_REQ_FLAGS_CONTINUE (1 << 6)
+
+/**
+ * @brief Text Request flags: Final.
+ *
+ * (F) When set to 1, this bit indicates that this is the last or only Text
+ * Request in a sequence of Text Requests; otherwise, it indicates that
+ * more Text Requests will follow.
+ */
+#define ISCSI_TEXT_REQ_FLAGS_FINAL    (1 << 7)
+
+/**
+ * @brief iSCSI Text Request packet data.
+ *
+ * The Text Request is provided to allow for the exchange of information
+ * and for future extensions. It permits the initiator to inform a
+ * target of its capabilities or request some special operations.
+ *
+ * An initiator MUST NOT have more than one outstanding Text Request on
+ * a connection at any given time.
+ *
+ * On a connection failure, an initiator must either explicitly abort
+ * any active allegiant text negotiation task or cause such a task to be
+ * implicitly terminated by the target.
+ */
+typedef struct __attribute__((packed)) iscsi_text_req_packet {
+	/// Always 0x04 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Text request flags.
+	uint8_t flags;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// Logical Unit Number (LUN) or Reserved.
+	uint64_t lun;
+
+	/**
+	 * @brief Initiator Task Tag (ITT).
+	 *
+	 * This is the initiator-assigned identifier for this Text Request. If
+	 * the command is sent as part of a sequence of Text Requests and
+	 * responses, the Initiator Task Tag MUST be the same for all the
+	 * requests within the sequence (similar to linked SCSI commands). The
+	 * I bit for all requests in a sequence also MUST be the same.
+	 */
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Target Transfer Tag (TTT).
+	 *
+	 * When the Target Transfer Tag is set to the reserved value 0xFFFFFFFF,
+	 * it tells the target that this is a new request, and the target resets
+	 * any internal state associated with the Initiator Task Tag (resets the
+	 * current negotiation state).\n
+	 * The target sets the Target Transfer Tag in a Text Response to a value
+	 * other than the reserved value 0xFFFFFFFF whenever it indicates that
+	 * it has more data to send or more operations to perform that are
+	 * associated with the specified Initiator Task Tag. It MUST do so
+	 * whenever it sets the F bit to 0 in the response. By copying the
+	 * Target Transfer Tag from the response to the next Text Request, the
+	 * initiator tells the target to continue the operation for the specific
+	 * Initiator Task Tag. The initiator MUST ignore the Target Transfer
+	 * Tag in the Text Response when the F bit is set to 1.\n
+	 * This mechanism allows the initiator and target to transfer a large
+	 * amount of textual data over a sequence of text-command/text-response
+	 * exchanges or to perform extended negotiation sequences.\n
+	 * If the Target Transfer Tag is not 0xFFFFFFFF, the LUN field MUST be
+	 * sent by the target in the Text Response.\n
+	 * A target MAY reset its internal negotiation state if an exchange is
+	 * stalled by the initiator for a long time or if it is running out of
+	 * resources.\n
+	 * Long Text Responses are handled as shown in the following example:\n
+	 * @verbatim
+	 *    I->T Text SendTargets=All (F = 1, TTT = 0xFFFFFFFF)
+	 *    T->I Text <part 1> (F = 0, TTT = 0x12345678)
+	 *    I->T Text <empty> (F = 1, TTT = 0x12345678)
+	 *    T->I Text <part 2> (F = 0, TTT = 0x12345678)
+	 *    I->T Text <empty> (F = 1, TTT = 0x12345678)
+	 *    ...
+	 *    T->I Text <part n> (F = 1, TTT = 0xFFFFFFFF)
+	 * @endverbatim
+	 */
+	uint32_t target_xfer_tag;
+
+	/// CmdSN.
+	uint32_t cmd_sn;
+
+	/// ExpStatSN.
+	uint32_t exp_stat_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2[2];
+} iscsi_text_req_packet;
+
+
+/**
+ * @brief Text Response flags: Continue.
+ *
+ * (C) When set to 1, this bit indicates that the text (set of key=value
+ * pairs) in this Text Response is not complete (it will be continued on
+ * subsequent Text Responses); otherwise, it indicates that this Text
+ * Response ends a set of key=value pairs. A Text Response with the
+ * C bit set to 1 MUST have the F bit set to 0.
+ */
+#define ISCSI_TEXT_RESPONSE_FLAGS_CONTINUE (1 << 6)
+
+/**
+ * @brief Text Response flags: Final.
+ *
+ * (F) When set to 1, in response to a Text Request with the Final bit set
+ * to 1, the F bit indicates that the target has finished the whole
+ * operation. Otherwise, if set to 0 in response to a Text Request with
+ * the Final Bit set to 1, it indicates that the target has more work to
+ * do (invites a follow-on Text Request). A Text Response with the
+ * F bit set to 1 in response to a Text Request with the F bit set to 0
+ * is a protocol error.\n
+ * A Text Response with the F bit set to 1 MUST NOT contain key=value
+ * pairs that may require additional answers from the initiator.
+ * A Text Response with the F bit set to 1 MUST have a Target Transfer
+ * Tag field set to the reserved value 0xFFFFFFFF.\n
+ * A Text Response with the F bit set to 0 MUST have a Target Transfer
+ * Tag field set to a value other than the reserved value 0xFFFFFFFF.
+ */
+#define ISCSI_TEXT_RESPONSE_FLAGS_FINAL    (1 << 7)
+
+/**
+ * @brief iSCSI Text Response packet data.
+ *
+ * The Text Response PDU contains the target's responses to the
+ * initiator's Text Request. The format of the Text field matches that
+ * of the Text Request.
+ */
+typedef struct __attribute__((packed)) iscsi_text_response_packet {
+	/// Always 0x24 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Text response flags.
+	uint8_t flags;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// Logical Unit Number (LUN) or Reserved.
+	uint64_t lun;
+
+	/// The Initiator Task Tag matches the tag used in the initial Text Request.
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Target Transfer Tag (TTT).
+	 *
+	 * When a target has more work to do (e.g., cannot transfer all the
+	 * remaining text data in a single Text Response or has to continue the
+	 * negotiation) and has enough resources to proceed, it MUST set the
+	 * Target Transfer Tag to a value other than the reserved value
+	 * 0xFFFFFFFF. Otherwise, the Target Transfer Tag MUST be set to
+	 * 0xFFFFFFFF.\n
+	 * When the Target Transfer Tag is not 0xFFFFFFFF, the LUN field may be
+	 * significant.\n
+	 * The initiator MUST copy the Target Transfer Tag and LUN in its next
+	 * request to indicate that it wants the rest of the data.\n
+	 * When the target receives a Text Request with the Target Transfer Tag
+	 * set to the reserved value 0xFFFFFFFF, it resets its internal
+	 * information (resets state) associated with the given Initiator Task
+	 * Tag (restarts the negotiation).\n
+	 * When a target cannot finish the operation in a single Text Response
+	 * and does not have enough resources to continue, it rejects the Text
+	 * Request with the appropriate Reject code.\n
+	 * A target may reset its internal state associated with an Initiator
+	 * Task Tag (the current negotiation state) as expressed through the
+	 * Target Transfer Tag if the initiator fails to continue the exchange
+	 * for some time. The target may reject subsequent Text Requests with
+	 * the Target Transfer Tag set to the "stale" value.
+	 */
+	uint32_t target_xfer_tag;
+
+	/// StatSN. The target StatSN variable is advanced by each Text Response sent.
+	uint32_t stat_sn;
+
+	/// ExpCmdSN.
+	uint32_t exp_cmd_sn;
+
+	/// MaxCmdSN.
+	uint32_t max_cmd_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2[2];
+} iscsi_text_response_packet;
+
+
+/**
+ * @brief iSCSI Initiator Session ID (ISID) packet data.
+ *
+ * This is an initiator-defined component of the session identifier and
+ * is structured as follows:
+ *
+ * For the T field values 00b and 01b, a combination of A and B (for
+ * 00b) or B and C (for 01b) identifies the vendor or organization whose
+ * component (software or hardware) generates this ISID. A vendor or
+ * organization with one or more OUIs, or one or more Enterprise
+ * Numbers, MUST use at least one of these numbers and select the
+ * appropriate value for the T field when its components generate ISIDs.
+ * An OUI or EN MUST be set in the corresponding fields in network byte
+ * order (byte big-endian).
+ *
+ * If the T field is 10b, B and C are set to a random 24-bit unsigned
+ * integer value in network byte order (byte big-endian).
+ *
+ * The Qualifier field is a 16-bit or 24-bit unsigned integer value that
+ * provides a range of possible values for the ISID within the selected
+ * namespace. It may be set to any value within the constraints
+ * specified in the iSCSI protocol.
+ *
+ * If the ISID is derived from something assigned to a hardware adapter
+ * or interface by a vendor as a preset default value, it MUST be
+ * configurable to a value assigned according to the SCSI port behavior
+ * desired by the system in which it is installed. The resultant ISID
+ * MUST also be persistent over power cycles, reboot, card swap, etc.
+ */
+typedef struct __attribute__((packed)) iscsi_isid {
+	/// Meaning depends on T bit, either 22-bit OUI or reserved.
+	uint8_t a;
+
+	/// Meaning depends on T bit, either 22-bit OUI, EN (IANA Enterprise Number) or random.
+	uint16_t b;
+
+	/// Meaning depends on T bit, either 24-bit Qualifier, EN (IANA Enterprise Number) or random.
+	uint8_t c;
+
+	/// Meaning depends on T bit, either 24-bit Qualifier or Qualifier.
+	uint16_t d;
+} iscsi_isid;
+
+
+/**
+ * @brief Login request flags: Next Stage (NSG): First bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with a specific stage in the session (SecurityNegotiation,\n
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move. The Next Stage value is only
+ * valid when the T bit is 1; otherwise, it is reserved.
+ */
+#define ISCSI_LOGIN_REQ_FLAGS_NEXT_STAGE_FIRST_BIT                     0
+
+/**
+ * @brief Login request flags: Next Stage (NSG): Last bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with a specific stage in the session (SecurityNegotiation,\n
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move. The Next Stage value is only
+ * valid when the T bit is 1; otherwise, it is reserved.
+ */
+#define ISCSI_LOGIN_REQ_FLAGS_NEXT_STAGE_LAST_BIT                      ((ISCSI_LOGIN_REQ_FLAGS_NEXT_STAGE_FIRST_BIT) + 2 - 1)
+
+/// Login request flags: Next Stage (NSG): Bit mask.
+#define ISCSI_LOGIN_REQ_FLAGS_NEXT_STAGE_MASK                          (ISCSI_BITS_GET_MASK(ISCSI_LOGIN_REQ_FLAGS_NEXT_STAGE_FIRST_BIT, ISCSI_LOGIN_REQ_FLAGS_NEXT_STAGE_LAST_BIT))
+
+
+/**
+ * @brief Login request flags: Current Stage (CSG): First bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with aspecific stage in the session (SecurityNegotiation,
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move.
+ */
+#define ISCSI_LOGIN_REQ_FLAGS_CURRENT_STAGE_FIRST_BIT                     2
+
+/**
+ * @brief Login request flags: Current Stage (CSG): Last bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with aspecific stage in the session (SecurityNegotiation,
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move.
+ */
+#define ISCSI_LOGIN_REQ_FLAGS_CURRENT_STAGE_LAST_BIT                      ((ISCSI_LOGIN_REQ_FLAGS_CURRENT_STAGE_FIRST_BIT) + 2 - 1)
+
+/// Login request flags: Current Stage (CSG): Bit mask.
+#define ISCSI_LOGIN_REQ_FLAGS_CURRENT_STAGE_MASK                          (ISCSI_BITS_GET_MASK(ISCSI_LOGIN_REQ_FLAGS_CURRENT_STAGE_FIRST_BIT, ISCSI_LOGIN_REQ_FLAGS_CURRENT_STAGE_LAST_BIT))
+
+
+/**
+ * @brief Login request flags: Continue.
+ *
+ * (C) When set to 1, this bit indicates that the text (set of key=value
+ * pairs) in this Login Request is not complete (it will be continued on
+ * subsequent Login Requests); otherwise, it indicates that this Login
+ * Request ends a set of key=value pairs. A Login Request with the
+ * C bit set to 1 MUST have the T bit set to 0.
+ */
+#define ISCSI_LOGIN_REQ_FLAGS_CONTINUE (1 << 6)
+
+/**
+ * @brief Login request flags: Transmit.
+ *
+ * (T) When set to 1, this bit indicates that the initiator is ready to
+ * transit to the next stage.\n
+ * If the T bit is set to 1 and the NSG is set to FullFeaturePhase, then
+ * this also indicates that the initiator is ready for the Login
+ * Final-Response.
+ */
+#define ISCSI_LOGIN_REQ_FLAGS_TRANSIT  (1 << 7)
+
+
+/**
+ * @brief iSCSI Login Request packet data.
+ *
+ * After establishing a TCP connection between an initiator and a
+ * target, the initiator MUST start a Login Phase to gain further access
+ * to the target's resources.
+ *
+ * The Login Phase consists of a sequence of Login Requests and Login
+ * Responses that carry the same Initiator Task Tag.
+ *
+ * Login Requests are always considered as immediate.
+ */
+typedef struct __attribute__((packed)) iscsi_login_req_packet {
+	/// Always 0x03 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Login request flags.
+	uint8_t flags;
+
+	/**
+	 * @brief Version-max indicates the maximum version number supported.
+	 *
+	 * All Login Requests within the Login Phase MUST carry the same
+	 * Version-max. Currently, this is always 0.\n
+	 * The target MUST use the value presented with the first Login Request.
+	 */
+	uint8_t version_max;
+
+	/**
+	 * @brief Version-min indicates the minimum version number supported.
+	 *
+	 * All Login Requests within the Login Phase MUST carry the same
+	 * Version-min. The target MUST use the value presented with the first
+	 * Login Request. Always 0 for now.
+	 */
+	uint8_t version_min;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// Initiator Session ID (ISID).
+	iscsi_isid isid;
+
+	/**
+	 * @brief Target Session Identifying Handle (TSIH).
+	 *
+	 * The TSIH must be set in the first Login Request. The reserved value
+	 * 0 MUST be used on the first connection for a new session. Otherwise,
+	 * the TSIH sent by the target at the conclusion of the successful login
+	 * of the first connection for this session MUST be used. The TSIH
+	 * identifies to the target the associated existing session for this new
+	 * connection.\n
+	 * All Login Requests within a Login Phase MUST carry the same TSIH.
+	 * The target MUST check the value presented with the first Login
+	 * Request.
+	 */
+	uint16_t tsih;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Connection ID (CID).
+	 *
+	 * The CID provides a unique ID for this connection within the session.\n
+	 * All Login Requests within the Login Phase MUST carry the same CID.
+	 * The target MUST use the value presented with the first Login Request.\n
+	 * A Login Request with a non-zero TSIH and a CID equal to that of an
+	 * existing connection implies a logout of the connection followed by a
+	 * login.
+	 */
+	uint16_t cid;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved;
+
+	/**
+	 * @brief CmdSN.
+	 *
+	 * The CmdSN is either the initial command sequence number of a session
+	 * (for the first Login Request of a session - the "leading" login) or
+	 * the command sequence number in the command stream if the login is for
+	 * a new connection in an existing session.\n
+	 * Examples:
+	 * - Login on a leading connection: If the leading login carries the
+	 *   CmdSN 123, all other Login Requests in the same Login Phase carry
+	 *   the CmdSN 123, and the first non-immediate command in the Full
+	 *   Feature Phase also carries the CmdSN 123.
+	 * - Login on other than a leading connection: If the current CmdSN at
+	 *   the time the first login on the connection is issued is 500, then
+	 *   that PDU carries CmdSN=500. Subsequent Login Requests that are
+	 *   needed to complete this Login Phase may carry a CmdSN higher than
+	 *   500 if non-immediate requests that were issued on other connections
+	 *   in the same session advance the CmdSN.
+	 *
+	 * If the Login Request is a leading Login Request, the target MUST use
+	 * the value presented in the CmdSN as the target value for the
+	 * ExpCmdSN.
+	 */
+	uint32_t cmd_sn;
+
+	/**
+	 * @brief ExpStatSN.
+	 *
+	 * For the first Login Request on a connection, this is the ExpStatSN
+	 * for the old connection, and this field is only valid if the Login
+	 * Request restarts a connection.\n
+	 * For subsequent Login Requests, it is used to acknowledge the Login
+	 * Responses with their increasing StatSN values.
+	 */
+	uint32_t exp_stat_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2[2];
+} iscsi_login_req_packet;
+ASSERT_IS_BHS( iscsi_login_req_packet );
+
+/// Login response Next Stage (NSG) flags: SecurityNegotiation.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_SECURITY_NEGOTIATION          0x0
+
+/// Login response Next Stage (NSG) flags: LoginOperationalNegotiation.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_LOGIN_OPERATIONAL_NEGOTIATION 0x1
+
+/// Login response Next Stage (NSG) flags: Reserved for future usage, may NOT be used.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_RESERVED                      0x2
+
+/// Login response Next Stage (NSG) flags: FullFeaturePhase.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_FULL_FEATURE_PHASE            0x3
+
+/**
+ * @brief Login response flags: Next Stage (NSG): First bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with a specific stage in the session (SecurityNegotiation,
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move The Next Stage value is only
+ * valid when the T bit is 1; otherwise, it is reserved.
+ */
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_FIRST_BIT                     0
+
+/**
+ * @brief Login response flags: Next Stage (NSG): Last bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with a specific stage in the session (SecurityNegotiation,
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move The Next Stage value is only
+ * valid when the T bit is 1; otherwise, it is reserved.
+ */
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_LAST_BIT                      ((ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_FIRST_BIT) + 2 - 1)
+
+/// Login response flags: Next Stage (NSG): Bit mask.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_MASK                          (ISCSI_BITS_GET_MASK(ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_FIRST_BIT, ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_LAST_BIT))
+
+/// Login response flags: Extracts the Next Stage (NSG) bits.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_GET_NEXT_STAGE(x)                        (ISCSI_BITS_GET((x), ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_FIRST_BIT, ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_LAST_BIT))
+
+/// Login response flags: Stores into the Next Stage (NSG) bits.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_PUT_NEXT_STAGE(x)                        (ISCSI_BITS_PUT((x), ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_FIRST_BIT, ISCSI_LOGIN_RESPONSE_FLAGS_NEXT_STAGE_LAST_BIT))
+
+
+/// Login response Current Stage (CSG) flags: SecurityNegotiation.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_SECURITY_NEGOTIATION          0x0
+
+/// Login response Current Stage (CSG) flags: LoginOperationalNegotiation.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_LOGIN_OPERATIONAL_NEGOTIATION 0x1
+
+/// Login response Current Stage (CSG) flags: Reserved for future usage, may NOT be used.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_RESERVED                      0x2
+
+/// Login response Current Stage (CSG) flags: FullFeaturePhase.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_FULL_FEATURE_PHASE            0x3
+
+/**
+ * @brief Login response flags: Current Stage (CSG): First bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with aspecific stage in the session (SecurityNegotiation,
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move.
+ */
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_FIRST_BIT                     2
+
+/**
+ * @brief Login response flags: Current Stage (CSG): First bit of the two bits.
+ *
+ * The Login negotiation requests and responses are associated
+ * with aspecific stage in the session (SecurityNegotiation,
+ * LoginOperationalNegotiation, FullFeaturePhase) and may indicate the
+ * next stage to which they want to move.
+ */
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_LAST_BIT                      ((ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_FIRST_BIT) + 2 - 1)
+
+/// Login request flags: Current Stage (CSG): Bit mask.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_MASK                          (ISCSI_BITS_GET_MASK(ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_FIRST_BIT, ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_LAST_BIT))
+
+/// Login request flags: Extracts the Current Stage (CSG) bits.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_GET_CURRENT_STAGE(x)                        (ISCSI_BITS_GET((x), ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_FIRST_BIT, ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_LAST_BIT))
+
+/// Login request flags: Stores into the Current Stage (CSG) bits.
+#define ISCSI_LOGIN_RESPONSE_FLAGS_PUT_CURRENT_STAGE(x)                        (ISCSI_BITS_PUT((x), ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_FIRST_BIT, ISCSI_LOGIN_RESPONSE_FLAGS_CURRENT_STAGE_LAST_BIT))
+
+
+/**
+ * @brief Login response flags: Continue.
+ *
+ * (C) When set to 1, this bit indicates that the text (set of key=value
+ * pairs) in this Login Response is not complete (it will be continued
+ * on subsequent Login Responses); otherwise, it indicates that this
+ * Login Response ends a set of key=value pairs. A Login Response with
+ * the C bit set to 1 MUST have the T bit set to 0.
+ */
+#define ISCSI_LOGIN_RESPONSE_FLAGS_CONTINUE      (1 << 6)
+
+/**
+ * @brief Login response flags: Transmit.
+ *
+ * (T) The T bit is set to 1 as an indicator of the end of the stage. If
+ * the T bit is set to 1 and the NSG is set to FullFeaturePhase, then
+ * this is also the Login Final-Response. A T bit of 0 indicates a
+ * "partial" response, which means "more negotiation needed".\n
+ * A Login Response with the T bit set to 1 MUST NOT contain key=value
+ * pairs that may require additional answers from the initiator within
+ * the same stage.\n
+ * If the Status-Class is 0, the T bit MUST NOT be set to 1 if the T bit
+ * in the request was set to 0.
+ */
+#define ISCSI_LOGIN_RESPONSE_FLAGS_TRANSIT       (1 << 7)
+
+
+/**
+ * @brief Login response status class: Success.
+ *
+ * Indicates that the iSCSI target successfully received, understood,
+ * and accepted the request. The numbering fields (StatSN, ExpCmdSN,
+ * MaxCmdSN) are only valid if Status-Class is 0.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_CLASS_SUCCESS 0x00
+
+/**
+ * @brief Login response status details: Success.
+ *
+ * Login is proceeding OK. If the response T bit is set to 1 in both the
+ * request and the matching response, and the NSG is set to
+ * FullFeaturePhase in both the request and the matching response, the
+ * Login Phase is finished, and the initiator may proceed to issue SCSI
+ * commands.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_SUCCESS 0x00
+
+
+/**
+ * @brief Login response status class: Redirection.
+ *
+ * Indicates that the initiator must take further action
+ * to complete the request. This is usually due to the
+ * target moving to a different address. All of the redirection
+ * Status-Class responses MUST return one or more text key
+ * parameters of the type "TargetAddress", which indicates the
+ * target's new address. A redirection response MAY be issued by
+ * a target prior to or after completing a security negotiation if
+ * a security negotiation is required. A redirection SHOULD be
+ * accepted by an initiator, even without having the target
+ * complete a security negotiation if any security negotiation is
+ * required, and MUST be accepted by the initiator after the
+ * completion of the security negotiation if any security
+ * negotiation is required.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_CLASS_REDIRECT 0x01
+
+/**
+ * @brief Login response status details: Temporarily redirected.
+ *
+ * The requested iSCSI Target Name (ITN) has temporarily moved
+ * to the address provided.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_REDIRECT_TEMP 0x01
+
+/**
+ * @brief Login response status details: Permanently redirected.
+ *
+ * The requested ITN has permanently moved to the address provided.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_REDIRECT_PERM 0x02
+
+
+/**
+ * @brief Login response status class: Initiator Error (not a format error).
+ *
+ * Indicates that the initiator most likely caused the error.\n
+ * This MAY be due to a request for a resource for which the
+ * initiator does not have permission. The request should
+ * not be tried again.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_CLASS_CLIENT_ERR 0x02
+
+/// Login response status details: Miscellaneous iSCSI initiator errors.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_MISC                   0x00
+
+/// Login response status details: The initiator could not be successfully authenticated or target authentication is not supported.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_AUTH_ERR               0x01
+
+/// Login response status details: The initiator is not allowed access to the given target.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_AUTH_FAIL              0x02
+
+/// Login response status details: The requested iSCSI Target Name (ITN) does not exist at this address.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_NOT_FOUND              0x03
+
+/// Login response status details: The requested ITN has been removed, and no forwarding address is provided.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_TARGET_REMOVED         0x04
+
+/// Login response status details: The requested iSCSI version range is not supported by the target.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_WRONG_VERSION          0x05
+
+/// Login response status details: Too many connections on this Session ID (SSID).
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_TOO_MANY_CONNECTIONS   0x06
+
+/// Login response status details: Missing parameters (e.g. iSCSI Initiator Name and/or Target Name).
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_MISSING_PARAMETER      0x07
+
+/// Login response status details: Target does not support session spanning to this connection (address).
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_NO_SESSION_SPANNING    0x08
+
+/// Login response status details: Target does not support this type of session or not from this initiator.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_SESSION_NO_SUPPORT     0x09
+
+/// Login response status details: Attempt to add a connection to a non-existent session.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_SESSION_NO_EXIST       0x0A
+
+/// Login response status details: Invalid request type during login.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_CLIENT_ERR_INVALID_LOGIN_REQ_TYPE 0x0B
+
+
+/**
+ * @brief Login response status class: Target Error.
+ *
+ * Indicates that the target sees no errors in the
+ * initiator's Login Request but is currently incapable of
+ * fulfilling the request. The initiator may retry the same Login
+ * Request later.
+ */
+#define ISCSI_LOGIN_RESPONSE_STATUS_CLASS_SERVER_ERR 0x03
+
+/// Login response status details: Target hardware or software error.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_SERVER_ERR_TARGET_ERROR        0x00
+
+/// Login response status details: The iSCSI service or target is not currently operational.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_SERVER_ERR_SERVICE_UNAVAILABLE 0x01
+
+/// The target has insufficient session, connection, or other resources.
+#define ISCSI_LOGIN_RESPONSE_STATUS_DETAILS_SERVER_ERR_OUT_OF_RESOURCES    0x02
+
+
+/**
+ * @brief iSCSI Login Response packet data.
+ *
+ * The Login Response indicates the progress and/or end of the Login
+ * Phase.
+ */
+typedef struct __attribute__((packed)) iscsi_login_response_packet {
+	/// Always 0x23 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Login response flags.
+	uint8_t flags;
+
+	/**
+	 * @brief This is the highest version number supported by the target.
+	 *
+	 * All Login Responses within the Login Phase MUST carry the same
+	 * Version-max.
+	 */
+	uint8_t version_max;
+
+	/**
+	 * @brief Version-active indicates the highest version supported by the target and initiator.
+	 *
+	 * If the target does not support a version within the
+	 * range specified by the initiator, the target rejects the login and
+	 * this field indicates the lowest version supported by the target.
+	 * All Login Responses within the Login Phase MUST carry the same
+	 * Version-active.\n
+	 * The initiator MUST use the value presented as a response to the first
+	 * Login Request.
+	 */
+	uint8_t version_active;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// Initiator Session ID (ISID).
+	iscsi_isid isid;
+
+	/**
+	 * @brief Target Session Identifying Handle (TSIH).
+	 *
+	 * The TSIH is the target-assigned session-identifying handle. Its
+	 * internal format and content are not defined by this protocol, except
+	 * for the value 0, which is reserved. With the exception of the Login
+	 * Final-Response in a new session, this field should be set to the TSIH
+	 * provided by the initiator in the Login Request. For a new session,
+	 * the target MUST generate a non-zero TSIH and ONLY return it in the
+	 * Login Final-Response.
+	 */
+	uint16_t tsih;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint32_t reserved;
+
+	/**
+	 * @brief StatSN.
+	 *
+	 * For the first Login Response (the response to the first Login
+	 * Request), this is the starting status sequence number for the
+	 * connection. The next response of any kind - including the next
+	 * Login Response, if any, in the same Login Phase - will carry this
+	 * number + 1. This field is only valid if the Status-Class is 0.
+	 */
+	uint32_t stat_sn;
+
+	/// ExpCmdSN.
+	uint32_t exp_cmd_sn;
+
+	/// MaxCmdSN.
+	uint32_t max_cmd_sn;
+
+	/**
+	 * @brief Status-class.
+	 *
+	 * Status-class (see above for details). If the Status-Class is
+	 * not 0, the initiator and target MUST close the TCP connection
+	 * If the target wishes to reject the Login Request for more than one
+	 * reason, it should return the primary reason for the rejection.
+	 */
+	uint8_t status_class;
+
+	/// Status-detail.
+	uint8_t status_detail;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved2;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved3;
+} iscsi_login_response_packet;
+
+
+/// Logout request reason code: Close the session. All commands associated with the session (if any) are terminated.
+#define ISCSI_LOGOUT_REQ_REASON_CODE_CLOSE_SESSION              0x00
+
+/// Logout request reason code: Close the connection. All commands associated with the connection (if any) are terminated.
+#define ISCSI_LOGOUT_REQ_REASON_CODE_CLOSE_CONNECTION           0x01
+
+/// Logout request reason code: Remove the connection for recovery. The connection is closed, and all commands associated with it, if any, are to be prepared for a new allegiance.
+#define ISCSI_LOGOUT_REQ_REASON_CODE_REMOVE_CONNECTION_RECOVERY 0x02
+
+/// Mask to get the logout reason from the reason_code field (lower 7 bits)
+#define ISCSI_LOGOUT_REQ_REASON_CODE_MASK                       0x7f
+
+/**
+ * @brief Logout request implicit reason code: Session reinstatement.
+ *
+ * The entire logout discussion in this section is also applicable for
+ * an implicit Logout realized by way of a connection reinstatement or
+ * session reinstatement. When a Login Request performs an implicit
+ * Logout, the implicit Logout is performed as if having the reason
+ * codes specified below:
+ */
+#define ISCSI_LOGOUT_REQ_REASON_CODE_IMPLICIT_SESSION_REINSTATEMENT      0x00
+
+/**
+ * @brief Logout request implicit reason code: Connection reinstatement when the operational ErrorRecoveryLevel < 2.
+ *
+ * The entire logout discussion in this section is also applicable for
+ * an implicit Logout realized by way of a connection reinstatement or
+ * session reinstatement. When a Login Request performs an implicit
+ * Logout, the implicit Logout is performed as if having the reason
+ * codes specified below:
+ */
+#define ISCSI_LOGOUT_REQ_REASON_CODE_IMPLICIT_CONNECTION_REINSTATEMENT   0x01
+
+/**
+ * @brief Logout request implicit reason code: Connection reinstatement when the operational ErrorRecoveryLevel = 2.
+ *
+ * The entire logout discussion in this section is also applicable for
+ * an implicit Logout realized by way of a connection reinstatement or
+ * session reinstatement. When a Login Request performs an implicit
+ * Logout, the implicit Logout is performed as if having the reason
+ * codes specified below:
+ */
+#define ISCSI_LOGOUT_REQ_REASON_CODE_IMPLICIT_CONNECTION_REINSTATEMENT_2 0x02
+
+
+/**
+ * @brief iSCSI Logout Request packet data.
+ *
+ * The Logout Request is used to perform a controlled closing of a
+ * connection.
+ *
+ * An initiator MAY use a Logout Request to remove a connection from a
+ * session or to close an entire session.
+ *
+ * After sending the Logout Request PDU, an initiator MUST NOT send any
+ * new iSCSI requests on the closing connection. If the Logout Request
+ * is intended to close the session, new iSCSI requests MUST NOT be sent
+ * on any of the connections participating in the session.
+ *
+ * When receiving a Logout Request with the reason code "close the
+ * connection" or "close the session", the target MUST terminate all
+ * pending commands, whether acknowledged via the ExpCmdSN or not, on
+ * that connection or session, respectively.
+ *
+ * When receiving a Logout Request with the reason code "remove the
+ * connection for recovery", the target MUST discard all requests not
+ * yet acknowledged via the ExpCmdSN that were issued on the specified
+ * connection and suspend all data/status/R2T transfers on behalf of
+ * pending commands on the specified connection.
+ *
+ * The target then issues the Logout Response and half-closes the TCP
+ * connection (sends FIN). After receiving the Logout Response and
+ * attempting to receive the FIN (if still possible), the initiator MUST
+ * completely close the logging-out connection. For the terminated
+ * commands, no additional responses should be expected.
+ *
+ * A Logout for a CID may be performed on a different transport
+ * connection when the TCP connection for the CID has already been
+ * terminated. In such a case, only a logical "closing" of the iSCSI
+ * connection for the CID is implied with a Logout.
+ *
+ * All commands that were not terminated or not completed (with status)
+ * and acknowledged when the connection is closed completely can be
+ * reassigned to a new connection if the target supports connection
+ * recovery.
+ *
+ * If an initiator intends to start recovery for a failing connection,
+ * it MUST use the Logout Request to "clean up" the target end of a
+ * failing connection and enable recovery to start, or use the Login
+ * Request with a non-zero TSIH and the same CID on a new connection for
+ * the same effect. In sessions with a single connection, the
+ * connection can be closed and then a new connection reopened. A
+ * connection reinstatement login can be used for recovery.
+ *
+ * A successful completion of a Logout Request with the reason code
+ * "close the connection" or "remove the connection for recovery"
+ * results at the target in the discarding of unacknowledged commands
+ * received on the connection being logged out. These are commands that
+ * have arrived on the connection being logged out but that have not
+ * been delivered to SCSI because one or more commands with a smaller
+ * CmdSN have not been received by iSCSI. The resulting holes in the
+ * command sequence numbers will have to be handled by appropriate
+ * recovery, unless the session is also closed.
+ */
+typedef struct __attribute__((packed)) iscsi_logout_req_packet {
+	/// Always 6 according to iSCSI specification.
+	uint8_t opcode;
+
+	/**
+	 * @brief Reason code.
+	 *
+	 * A target implicitly terminates the active tasks due to the iSCSI
+	 * protocol in the following cases:
+	 * -# When a connection is implicitly or explicitly logged out with
+	 *    the reason code "close the connection" and there are active
+	 *    tasks allegiant to that connection.
+	 * -# When a connection fails and eventually the connection state
+	 *    times out and there are active tasks allegiant to that
+	 *    connection
+	 * -# When a successful recovery Logout is performed while there are
+	 *    active tasks allegiant to that connection and those tasks
+	 *    eventually time out after the Time2Wait and Time2Retain periods
+	 *    without allegiance reassignment
+	 * -# When a connection is implicitly or explicitly logged out with
+	 *    the reason code "close the session" and there are active tasks
+	 *    in that session
+	 *
+	 * If the tasks terminated in any of the above cases are SCSI tasks,
+	 * they must be internally terminated as if with CHECK CONDITION status.
+	 * This status is only meaningful for appropriately handling the
+	 * internal SCSI state and SCSI side effects with respect to ordering,
+	 * because this status is never communicated back as a terminating
+	 * status to the initiator. However, additional actions may have to be
+	 * taken at the SCSI level, depending on the SCSI context as defined by
+	 * the SCSI standards (e.g., queued commands and ACA; UA for the next
+	 * command on the I_T nexus in cases a), b), and c) above). After the
+	 * tasks are terminated, the target MUST report a Unit Attention condition
+	 * on the next command processed on any connection for each affected
+	 * I_T_L nexus with the status of CHECK CONDITION, the ASC/ASCQ value
+	 * of 0x47 / 0x7F ("SOME COMMANDS CLEARED BY ISCSI PROTOCOL EVENT"), etc.
+	 */
+	uint8_t reason_code;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved;
+
+	/// TotalAHSLength (MUST be 0 for this PDU).
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength (MUST be 0 for this PDU).
+	uint8_t ds_len[3];
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Connection ID (CID).
+	 *
+	 * This is the connection ID of the connection to be closed (including
+	 * closing the TCP stream). This field is only valid if the reason code
+	 * is not "close the session".
+	 */
+	uint16_t cid;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved3;
+
+	/// CmdSN.
+	uint32_t cmd_sn;
+
+	/// This is the last ExpStatSN value for the connection to be closed.
+	uint32_t exp_stat_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved4[2];
+} iscsi_logout_req_packet;
+
+
+/// Logout response - response code: Connection or session closed successfully.
+#define ISCSI_LOGOUT_RESPONSE_CLOSED_SUCCESSFULLY               0x00
+
+/// Logout response - response code: Connection ID (CID) not found.
+#define ISCSI_LOGOUT_RESPONSE_CID_NOT_FOUND                     0x01
+
+/// Logout response - response code: Connection recovery is not supported (i.e., the Logout reason code was "remove the connection for recovery" and the target does not support it as indicated by the operational ErrorRecoveryLevel).
+#define ISCSI_LOGOUT_RESPONSE_CONNECTION_RECOVERY_NOT_SUPPORTED 0x02
+
+/// Logout response - response code: Cleanup failed for various reasons.
+#define ISCSI_LOGOUT_RESPONSE_CLEANUP_FAILED                    0x03
+
+/**
+ * @brief iSCSI Logout Response packet data.
+ *
+ * The Logout Response is used by the target to indicate if the cleanup
+ * operation for the connection(s) has completed.
+ *
+ * After Logout, the TCP connection referred by the CID MUST be closed
+ * at both ends (or all connections must be closed if the logout reason
+ * was session close).
+ */
+typedef struct __attribute__((packed)) iscsi_logout_response_packet {
+	/// Always 0x26 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Reserved for future usage (must be always 0x80 for now).
+	uint8_t flags;
+
+	/// Response.
+	uint8_t response;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint8_t reserved;
+
+	/// TotalAHSLength (MUST be 0 for this PDU).
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength (MUST be 0 for this PDU).
+	uint8_t ds_len[3];
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint32_t reserved3;
+
+	/// StatSN.
+	uint32_t stat_sn;
+
+	/// ExpCmdSN.
+	uint32_t exp_cmd_sn;
+
+	/// MaxCmdSN.
+	uint32_t max_cmd_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint32_t reserved4;
+
+	/**
+	 * @brief Time2Wait.
+	 *
+	 * If the Logout response code is 0 and the operational
+	 * ErrorRecoveryLevel is 2, this is the minimum amount of time, in
+	 * seconds, to wait before attempting task reassignment. If the Logout
+	 * response code is 0 and the operational ErrorRecoveryLevel is less
+	 * than 2, this field is to be ignored.\n
+	 * This field is invalid if the Logout response code is 1.\n
+	 * If the Logout response code is 2 or 3, this field specifies the
+	 * minimum time to wait before attempting a new implicit or explicit
+	 * logout.\n
+	 * If Time2Wait is 0, the reassignment or a new Logout may be attempted
+	 * immediately.
+	 */
+	uint16_t time_wait;
+
+	/**
+	 * @brief Time2Retain.
+	 *
+	 * If the Logout response code is 0 and the operational
+	 * ErrorRecoveryLevel is 2, this is the maximum amount of time, in
+	 * seconds, after the initial wait (Time2Wait) that the target waits for
+	 * the allegiance reassignment for any active task, after which the task
+	 * state is discarded. If the Logout response code is 0 and the
+	 * operational ErrorRecoveryLevel is less than 2, this field is to be
+	 * ignored.\n
+	 * This field is invalid if the Logout response code is 1.\n
+	 * If the Logout response code is 2 or 3, this field specifies the
+	 * maximum amount of time, in seconds, after the initial wait
+	 * (Time2Wait) that the target waits for a new implicit or explicit
+	 * logout.\n
+	 * If it is the last connection of a session, the whole session state is
+	 * discarded after Time2Retain.\n
+	 * If Time2Retain is 0, the target has already discarded the connection
+	 * (and possibly the session) state along with the task states. No
+	 * reassignment or Logout is required in this case.
+	 */
+	uint16_t time_retain;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint32_t reserved5;
+} iscsi_logout_response_packet;
+
+
+/// iSCSI Reject packet data: Reserved, original PDU can't be resent.
+#define ISCSI_REJECT_REASON_RESERVED                    0x01
+
+/**
+ * @brief iSCSI Reject packet data: Data (payload) digest error, original PDU can be resent.
+ *
+ * For iSCSI, Data-Out PDU retransmission is only done if the
+ * target requests retransmission with a recovery R2T. However,
+ * if this is the data digest error on immediate data, the
+ * initiator may choose to retransmit the whole PDU, including
+ * the immediate data.
+ */
+#define ISCSI_REJECT_REASON_DATA_DIGEST_ERR             0x02
+
+/// iSCSI Reject reason packet data: SNACK Reject (original PDU can be resent).
+#define ISCSI_REJECT_REASON_SNACK_REJECT                0x03
+
+/// iSCSI Reject reason packet data: Protocol Error (e.g., SNACK Request for a status that was already acknowledged). Original PDU can't be resent.
+#define ISCSI_REJECT_REASON_PROTOCOL_ERR                0x04
+
+/// iSCSI Reject reason packet data: Command not supported (original PDU can't be resent).
+#define ISCSI_REJECT_REASON_COMMAND_NOT_SUPPORTED       0x05
+
+/// iSCSI Reject reason packet data: Immediate command reject - too many immediate commands (original PDU can be resent).
+#define ISCSI_REJECT_REASON_TOO_MANY_IMMEDIATE_COMMANDS 0x06
+
+/// iSCSI Reject reason packet data: Task in progress (original PDU can't be resent).
+#define ISCSI_REJECT_REASON_TASK_IN_PROGRESS            0x07
+
+/// iSCSI Reject reason packet data: Invalid data ack (original PDU can't be resent).
+#define ISCSI_REJECT_REASON_INVALID_DATA_ACK            0x08
+
+/**
+ * @brief iSCSI Reject reason packet data: Invalid PDU field, original PDU can't be resent.
+ *
+ * A target should use this reason code for all invalid values
+ * of PDU fields that are meant to describe a task, a response,
+ * or a data transfer. Some examples are invalid TTT/ITT,
+ * buffer offset, LUN qualifying a TTT, and an invalid sequence
+ * number in a SNACK.
+ */
+#define ISCSI_REJECT_REASON_INVALID_PDU_FIELD           0x09
+
+/// iSCSI Reject reason packet data: Long op reject - Can't generate Target Transfer Tag - out of resources. Original PDU can be resent later.
+#define ISCSI_REJECT_REASON_OUT_OF_RESOURCES            0x0A
+
+/**
+ * @brief iSCSI Reject reason packet data: Deprecated; MUST NOT be used.
+ *
+ * Reason code 0x0B is deprecated and MUST NOT be used by
+ * implementations. An implementation receiving reason code
+ * 0x0B MUST treat it as a negotiation failure that terminates
+ * the Login Phase and the TCP connection.
+ */
+#define ISCSI_REJECT_REASON_DEPRECATED                  0x0B
+
+/// iSCSI Reject reason packet data: Waiting for Logout, original PDU can't be resent.
+#define ISCSI_REJECT_REASON_WAITING_FOR_LOGOUT          0x0C
+
+/**
+ * @brief iSCSI Reject packet data.
+ *
+ * This structure will be received or sent, if an iSCSI
+ * packet was rejected or has been rejected for some reason.
+ */
+typedef struct __attribute__((packed)) iscsi_reject_packet {
+	/// Always 0x3F according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Reserved for future usage (must be always 0x80 for now).
+	uint8_t flags;
+
+	/**
+	 * @brief Reject reason.
+	 *
+	 * In all the cases in which a pre-instantiated SCSI task is terminated
+	 * because of the reject, the target MUST issue a proper SCSI command
+	 * response with CHECK CONDITION. In these cases in which a status for
+	 * the SCSI task was already sent before the reject, no additional
+	 * status is required. If the error is detected while data from the
+	 * initiator is still expected (i.e., the command PDU did not contain
+	 * all the data and the target has not received a Data-Out PDU with the
+	 * Final bit set to 1 for the unsolicited data, if any, and all
+	 * outstanding R2Ts, if any), the target MUST wait until it receives
+	 * the last expected Data-Out PDUs with the F bit set to 1 before
+	 * sending the Response PDU.
+	 */
+	uint8_t reason;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint8_t reserved;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2;
+
+	/// Always 0xFFFFFFFF for now.
+	uint32_t tag;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint32_t reserved3;
+
+	/**
+	 * @brief StatSN.
+	 *
+	 * This field carries its usual value and is not related to the
+	 * rejected command. The StatSN is advanced after a Reject.
+	 */
+	uint32_t stat_sn;
+
+	/**
+	 * @brief ExpCmdSN.
+	 *
+	 * This field carries its usual value and is not related to the
+	 * rejected command.
+	 */
+	uint32_t exp_cmd_sn;
+
+	/**
+	 * @brief MaxCmdSN.
+	 *
+	 * This field carries its usual value and is not related to the
+	 * rejected command.
+	 */
+	uint32_t max_cmd_sn;
+
+	/**
+	 * @brief DataSN / Ready To Transfer Sequence Number (R2TSN) or Reserved.
+	 *
+	 * This field is only valid if the rejected PDU is a Data/R2T SNACK and
+	 * the Reject reason code is "Protocol Error". The DataSN/R2TSN is the
+	 * next Data/R2T sequence number that the target would send for the
+	 * task, if any.
+	 */
+	uint32_t data_r2t_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved4;
+
+	/**
+	 * @brief Complete Header of Bad PDU.
+	 *
+	 * The target returns the header (not including the digest) of the
+	 * PDU in error as the data of the response.
+	 */
+	iscsi_bhs_packet bad_pdu_hdr;
+} iscsi_reject_packet;
+
+/**
+ * @brief iSCSI NOP-Out packet data.
+ *
+ * NOP-Out may be used by an initiator as a "ping request" to verify
+ * that a connection/session is still active and all its components are
+ * operational. The NOP-In response is the "ping echo".
+ *
+ * A NOP-Out is also sent by an initiator in response to a NOP-In.
+ *
+ * A NOP-Out may also be used to confirm a changed ExpStatSN if another
+ * PDU will not be available for a long time.
+ *
+ * Upon receipt of a NOP-In with the Target Transfer Tag set to a valid
+ * value (not the reserved value 0xffffffff), the initiator MUST respond
+ * with a NOP-Out. In this case, the NOP-Out Target Transfer Tag MUST
+ * contain a copy of the NOP-In Target Transfer Tag. The initiator
+ *
+ * SHOULD NOT send a NOP-Out in response to any other received NOP-In,
+ * in order to avoid lengthy sequences of NOP-In and NOP-Out PDUs sent
+ * in response to each other.
+ */
+typedef struct __attribute__((packed)) iscsi_nop_out_packet {
+	/// Always 0x00 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Reserved for future usage (must be always 0x80 for now).
+	uint8_t flags;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved;
+
+	/// TotalAHSLength.
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// LUN or Reserved.
+	uint64_t lun;
+
+	/**
+	 * @brief Initiator Task Tag (ITT).
+	 *
+	 * The NOP-Out MUST have the Initiator Task Tag set to a valid value
+	 * only if a response in the form of a NOP-In is requested (i.e., the
+	 * NOP-Out is used as a ping request). Otherwise, the Initiator Task
+	 * Tag MUST be set to 0xFFFFFFFF.\n
+	 * When a target receives the NOP-Out with a valid Initiator Task Tag,
+	 * it MUST respond with a NOP-In Response.\n
+	 * If the Initiator Task Tag contains 0xFFFFFFFF, the I bit MUST be set
+	 * to 1, and the CmdSN is not advanced after this PDU is sent.
+	 */
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Target Transfer Tag (TTT).
+	 *
+	 * The Target Transfer Tag is a target-assigned identifier for the
+	 * operation.\n
+	 * The NOP-Out MUST only have the Target Transfer Tag set if it is
+	 * issued in response to a NOP-In with a valid Target Transfer Tag. In
+	 * this case, it copies the Target Transfer Tag from the NOP-In PDU.\n
+	 * Otherwise, the Target Transfer Tag MUST be set to 0xFFFFFFFF.\n
+	 * When the Target Transfer Tag is set to a value other than 0xFFFFFFFF,
+	 * the LUN field MUST also be copied from the NOP-In.
+	 */
+	uint32_t target_xfer_tag;
+
+	/// CmdSN.
+	uint32_t cmd_sn;
+
+	/// ExpStatSN.
+	uint32_t exp_stat_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved2[2];
+} iscsi_nop_out_packet;
+
+
+/**
+ * @brief iSCSI NOP-In packet data.
+ *
+ * NOP-In is sent by a target as either a response to a NOP-Out, a
+ * "ping" to an initiator, or a means to carry a changed ExpCmdSN and/or
+ * MaxCmdSN if another PDU will not be available for a long time (as
+ * determined by the target).
+ *
+ * When a target receives the NOP-Out with a valid Initiator Task Tag
+ * (not the reserved value 0xFFFFFFFF), it MUST respond with a NOP-In
+ * with the same Initiator Task Tag that was provided in the NOP-Out
+ * request. It MUST also duplicate up to the first
+ * MaxRecvDataSegmentLength bytes of the initiator-provided Ping Data.
+ * For such a response, the Target Transfer Tag MUST be 0xFFFFFFFF.
+ *
+ * The target SHOULD NOT send a NOP-In in response to any other received
+ * NOP-Out in order to avoid lengthy sequences of NOP-In and NOP-Out
+ * PDUs sent in response to each other.
+ *
+ * Otherwise, when a target sends a NOP-In that is not a response to a
+ * NOP-Out received from the initiator, the Initiator Task Tag MUST be
+ * set to 0xFFFFFFFF, and the data segment MUST NOT contain any data
+ * (DataSegmentLength MUST be 0).
+ */
+typedef struct __attribute__((packed)) iscsi_nop_in_packet {
+	/// Always 0x20 according to iSCSI specification.
+	uint8_t opcode;
+
+	/// Reserved for future usage (must be always 0x80 for now).
+	uint8_t flags;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint16_t reserved;
+
+	/// TotalAHSLength
+	uint8_t total_ahs_len;
+
+	/// DataSegmentLength.
+	uint8_t ds_len[3];
+
+	/// A LUN MUST be set to a correct value when the Target Transfer Tag is valid (not the reserved value 0xFFFFFFFF).
+	uint64_t lun;
+
+	/// Initiator Task Tag (ITT) or 0xFFFFFFFF.
+	uint32_t init_task_tag;
+
+	/**
+	 * @brief Target Transfer Tag (TTT).
+	 *
+	 * If the target is responding to a NOP-Out, this field is set to the
+	 * reserved value 0xFFFFFFFF.\n
+	 * If the target is sending a NOP-In as a ping (intending to receive a
+	 * corresponding NOP-Out), this field is set to a valid value (not the
+	 * reserved value 0xFFFFFFFF).\n
+	 * If the target is initiating a NOP-In without wanting to receive a
+	 * corresponding NOP-Out, this field MUST hold the reserved value
+	 * 0xFFFFFFFF.
+	 */
+	uint32_t target_xfer_tag;
+
+	/**
+	 * @brief StatSN.
+	 *
+	 * The StatSN field will always contain the next StatSN. However, when
+	 * the Initiator Task Tag is set to 0xFFFFFFFF, the StatSN for the
+	 * connection is not advanced after this PDU is sent.
+	 */
+	uint32_t stat_sn;
+
+	/// ExpCmdSN.
+	uint32_t exp_cmd_sn; // ExpCmdSN
+
+	/// MaxCmdSN.
+	uint32_t max_cmd_sn;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint32_t reserved2;
+
+	/// Reserved for future usage, always MUST be 0.
+	uint64_t reserved3;
+} iscsi_nop_in_packet;
+
+
+/// Maximum length of a key according to iSCSI specifications.
+#define ISCSI_TEXT_KEY_MAX_LEN          63U
+
+/// Maximum length of value for a simple key type.
+#define ISCSI_TEXT_VALUE_MAX_SIMPLE_LEN 255U
+
+/// Maximum length of value for a normal key.
+#define ISCSI_TEXT_VALUE_MAX_LEN        8192U
+
+
+typedef struct iscsi_connection iscsi_connection;
+
+
+/// Read/write lock for iSCSI global vector. MUST be initialized with iscsi_create before any iSCSI functions are used.
+//extern pthread_rwlock_t iscsi_globvec_rwlock;
+
+
+/// iSCSI SCSI status code: Good.
+#define ISCSI_SCSI_STATUS_GOOD                  0x00
+
+/// iSCSI SCSI status code: Check condition.
+#define ISCSI_SCSI_STATUS_CHECK_COND            0x02
+
+/// iSCSI SCSI status code: Condition met.
+#define ISCSI_SCSI_STATUS_COND_MET              0x04
+
+/// iSCSI SCSI status code: Busy.
+#define ISCSI_SCSI_STATUS_BUSY                  0x08
+
+/// iSCSI SCSI status code: Intermediate.
+#define ISCSI_SCSI_STATUS_INTERMEDIATE          0x10
+
+/// iSCSI SCSI status code: Intermediate condition met.
+#define ISCSI_SCSI_STATUS_INTERMEDIATE_COND_MET 0x14
+
+/// iSCSI SCSI status code: Reservation conflict.
+#define ISCSI_SCSI_STATUS_RESERVATION_CONFLICT  0x18
+
+/// iSCSI SCSI status code: Task set full.
+#define ISCSI_SCSI_STATUS_TASK_SET_FULL         0x28
+
+/// iSCSI SCSI status code: ACA active.
+#define ISCSI_SCSI_STATUS_ACA_ACTIVE            0x30
+
+/// iSCSI SCSI status code: Task aborted.
+#define ISCSI_SCSI_STATUS_TASK_ABORTED          0x40
+
+
+/// iSCSI SCSI sense key: No sense.
+#define ISCSI_SCSI_SENSE_KEY_NO_SENSE        0x00
+
+/// iSCSI SCSI sense key: Recovered error.
+#define ISCSI_SCSI_SENSE_KEY_RECOVERED_ERR   0x01
+
+/// iSCSI SCSI sense key: Not ready.
+#define ISCSI_SCSI_SENSE_KEY_NOT_READY       0x02
+
+/// iSCSI SCSI sense key: Medium error.
+#define ISCSI_SCSI_SENSE_KEY_MEDIUM_ERR      0x03
+
+/// iSCSI SCSI sense key: Hardware error.
+#define ISCSI_SCSI_SENSE_KEY_HARDWARE_ERR    0x04
+
+/// iSCSI SCSI sense key: Illegal request.
+#define ISCSI_SCSI_SENSE_KEY_ILLEGAL_REQ     0x05
+
+/// iSCSI SCSI sense key: Unit attention.
+#define ISCSI_SCSI_SENSE_KEY_UNIT_ATTENTION  0x06
+
+/// iSCSI SCSI sense key: Data protect.
+#define ISCSI_SCSI_SENSE_KEY_DATA_PROTECT    0x07
+
+/// iSCSI SCSI sense key: Blank check.
+#define ISCSI_SCSI_SENSE_KEY_BLANK_CHECK     0x08
+
+/// iSCSI SCSI sense key: Vendor specific.
+#define ISCSI_SCSI_SENSE_KEY_VENDOR_SPECIFIC 0x09
+
+/// iSCSI SCSI sense key: Copy aborted.
+#define ISCSI_SCSI_SENSE_KEY_COPY_ABORTED    0x0A
+
+/// iSCSI SCSI sense key: Aborted command.
+#define ISCSI_SCSI_SENSE_KEY_ABORTED_COMMAND 0x0B
+
+/// iSCSI SCSI sense key: Volume overflow.
+#define ISCSI_SCSI_SENSE_KEY_VOLUME_OVERFLOW 0x0D
+
+/// iSCSI SCSI sense key: Miscompare.
+#define ISCSI_SCSI_SENSE_KEY_MISCOMPARE      0x0E
+
+
+/// iSCSI SCSI Additional Sense Code (ASC): No additional sense.
+#define ISCSI_SCSI_ASC_NO_ADDITIONAL_SENSE                0x00
+
+/// iSCSI SCSI Additional Sense Code (ASC): Peripheral device write fault.
+#define ISCSI_SCSI_ASC_PERIPHERAL_DEVICE_WRITE_FAULT      0x03
+
+/// iSCSI SCSI Additional Sense Code (ASC): Logical unit not ready.
+#define ISCSI_SCSI_ASC_LOGICAL_UNIT_NOT_READY             0x04
+
+/// iSCSI SCSI Additional Sense Code (ASC): Warning.
+#define ISCSI_SCSI_ASC_WARNING                            0x0B
+
+/// iSCSI SCSI Additional Sense Code (ASC): Write error.
+#define ISCSI_SCSI_ASC_WRITE_ERR                          0x0C
+
+/// iSCSI SCSI Additional Sense Code (ASC): Block guard check failed.
+#define ISCSI_SCSI_ASC_LOGICAL_BLOCK_GUARD_CHECK_FAIL     0x10
+
+/// iSCSI SCSI Additional Sense Code (ASC): Block application tag checdk failed.
+#define ISCSI_SCSI_ASC_LOGICAL_BLOCK_APP_TAG_CHECK_FAIL   0x10
+
+/// iSCSI SCSI Additional Sense Code (ASC): Block reference tag check failed.
+#define ISCSI_SCSI_ASC_LOGICAL_BLOCK_REF_TAG_CHECK_FAIL   0x10
+
+/// iSCSI SCSI Additional Sense Code (ASC): Unrecovered read error.
+#define ISCSI_SCSI_ASC_UNRECOVERED_READ_ERR               0x11
+
+/// iSCSI SCSI Additional Sense Code (ASC): Miscompare during verify operation.
+#define ISCSI_SCSI_ASC_MISCOMPARE_DURING_VERIFY_OPERATION 0x1D
+
+/// iSCSI SCSI Additional Sense Code (ASC): Invalid command operation code.
+#define ISCSI_SCSI_ASC_INVALID_COMMAND_OPERATION_CODE     0x20
+
+/// iSCSI SCSI Additional Sense Code (ASC): Access denied.
+#define ISCSI_SCSI_ASC_ACCESS_DENIED                      0x20
+
+/// iSCSI SCSI Additional Sense Code (ASC): Logical block address out of range.
+#define ISCSI_SCSI_ASC_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE 0x21
+
+/// iSCSI SCSI Additional Sense Code (ASC): Invalid field in CDB.
+#define ISCSI_SCSI_ASC_INVALID_FIELD_IN_CDB               0x24
+
+/// iSCSI SCSI Additional Sense Code (ASC): Logical unit not supported.
+#define ISCSI_SCSI_ASC_LU_NOT_SUPPORTED                   0x25
+
+/// iSCSI SCSI Additional Sense Code (ASC): Write protected.
+#define ISCSI_SCSI_ASC_WRITE_PROTECTED                    0x27
+
+/// iSCSI SCSI Additional Sense Code (ASC): Data has changed.
+#define ISCSI_SCSI_ASC_CAPACITY_DATA_HAS_CHANGED          0x2A
+
+/// iSCSI SCSI Additional Sense Code (ASC): Format command failed.
+#define ISCSI_SCSI_ASC_FORMAT_COMMAND_FAIL                0x31
+
+/// iSCSI SCSI Additional Sense Code (ASC): Saving parameters not supported.
+#define ISCSI_SCSI_ASC_SAVING_PARAMETERS_NOT_SUPPORTED    0x39
+
+/// iSCSI SCSI Additional Sense Code (ASC): Internal target failure.
+#define ISCSI_SCSI_ASC_INTERNAL_TARGET_FAIL               0x44
+
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Cause not reportable.
+#define ISCSI_SCSI_ASCQ_CAUSE_NOT_REPORTABLE             0x00
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Becoming ready.
+#define ISCSI_SCSI_ASCQ_BECOMING_READY                   0x01
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Format command failed.
+#define ISCSI_SCSI_ASCQ_FORMAT_COMMAND_FAIL              0x01
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Block guard check failed.
+#define ISCSI_SCSI_ASCQ_LOGICAL_BLOCK_GUARD_CHECK_FAIL   0x01
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Block application tag check failed.
+#define ISCSI_SCSI_ASCQ_LOGICAL_BLOCK_APP_TAG_CHECK_FAIL 0x02
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): No access rights.
+#define ISCSI_SCSI_ASCQ_NO_ACCESS_RIGHTS                 0x02
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Manual intervention required.
+#define ISCSI_SCSI_ASCQ_MANUAL_INTERVENTION_REQUIRED     0x03
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Block reference tag check failed.
+#define ISCSI_SCSI_ASCQ_LOGICAL_BLOCK_REF_TAG_CHECK_FAIL 0x03
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Power loss expected.
+#define ISCSI_SCSI_ASCQ_POWER_LOSS_EXPECTED              0x08
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Invalid logical unit identifier.
+#define ISCSI_SCSI_ASCQ_INVALID_LU_IDENTIFIER            0x09
+
+/// iSCSI SCSI Additional Sense Code Qualifier (ASCQ): Capacity data has changed.
+#define ISCSI_SCSI_ASCQ_CAPACITY_DATA_HAS_CHANGED        0x09
+
+
+
+
+/// iSCSI SCSI task run: Unknown.
+#define ISCSI_SCSI_TASK_RUN_UNKNOWN  (-1)
+
+/// iSCSI SCSI task run: Completed.
+#define ISCSI_SCSI_TASK_RUN_COMPLETE  0
+
+
+typedef struct iscsi_scsi_task iscsi_scsi_task;
+typedef struct iscsi_scsi_lun iscsi_scsi_lun;
+
+
+/**
+ * @brief iSCSI SCSI Task.
+ *
+ * This structure is used for the iSCSI SCSI
+ * layer task management.
+ */
+typedef struct iscsi_scsi_task {
+	/// Connection associated with this task.
+	iscsi_connection *connection;
+
+	/// SCSI Command Descriptor Block (CDB).
+	iscsi_scsi_cdb *cdb;
+
+	/// SCSI sense data. If set, owned by this struct.
+	iscsi_scsi_sense_data_packet *sense_data;
+
+	/// Output buffer. If set, owned by this struct.
+	uint8_t *buf;
+
+	/// Offset in bytes in image for DATA-in command.
+	size_t file_offset;
+
+	/// Length of buffer in bytes.
+	uint32_t len;
+
+	/// Expected data transfer length (from iSCSI PDU field)
+	uint32_t exp_xfer_len;
+
+	/// Unique identifier for this task.
+	uint64_t id;
+
+	/// Whether the R bit was set in the iSCSI request (BHS).
+	bool is_read;
+
+	/// Whether the W bit was set in the iSCSI request (BHS).
+	bool is_write;
+
+	/// Sense data length.
+	uint8_t sense_data_len;
+
+	/// iSCSI SCSI status code.
+	uint8_t status;
+
+	/// Uplink read mutex for sync
+	pthread_mutex_t uplink_mutex;
+
+	/// Conditional to signal uplink read complete
+	pthread_cond_t uplink_cond;
+} iscsi_scsi_task;
+
+
+/// iSCSI SCSI emulation physical block size in bytes.
+#define ISCSI_SCSI_EMU_PHYSICAL_BLOCK_SIZE      DNBD3_BLOCK_SIZE
+
+/// iSCSI SCSI emulation logical block size in bytes.
+#define ISCSI_SCSI_EMU_LOGICAL_BLOCK_SIZE      (512)
+
+/// Block shift difference between dnbd3 (4k) and iSCSI (512b)
+#define ISCSI_SCSI_EMU_BLOCK_DIFF_SHIFT     (3)
+
+_Static_assert( (ISCSI_SCSI_EMU_LOGICAL_BLOCK_SIZE << ISCSI_SCSI_EMU_BLOCK_DIFF_SHIFT) == ISCSI_SCSI_EMU_PHYSICAL_BLOCK_SIZE,
+	"Block size parameters are inconsistent" );
+
+
+/// iSCSI target node WWN identifier prefix string.
+#define ISCSI_TARGET_NODE_WWN_NAME_PREFIX "wwn-0x"
+
+/// iSCSI target node maximum length
+#define ISCSI_TARGET_NODE_MAX_NAME_LEN 223U
+
+
+/**
+ * All mandatory fields in login process.
+ * Set to -1 or NULL if not sent by client.
+ */
+typedef struct iscsi_login_kvp
+{
+	/// Largest PDU client can receive.
+	int MaxRecvDataSegmentLength;
+
+	/// Maximum burst length client can receive.
+	int MaxBurstLength;
+
+	// Maximum unsolicited burst length client can receive.
+	int FirstBurstLength;
+
+	/// Maximum number of connections.
+	int MaxConnections;
+
+	/// Error recovery level.
+	int ErrorRecoveryLevel;
+
+	/// The session type (Discovery, Normal).
+	const char *SessionType;
+
+	/// Desired auth method.
+	const char *AuthMethod;
+
+	/// SendTargets command.
+	const char *SendTargets;
+
+	/// HeaderDigest requested by client.
+	const char *HeaderDigest;
+
+	/// DataDigest requested by client.
+	const char *DataDigest;
+
+	const char *InitiatorName;
+
+	const char *TargetName;
+} iscsi_negotiation_kvp;
+
+/**
+ * Options/limits the client told us that
+ * are relevant for proper communication
+ */
+typedef struct iscsi_session_options
+{
+	/// Largest PDU client can receive.
+	int MaxRecvDataSegmentLength;
+
+	/// Maximum burst length client can receive.
+	int MaxBurstLength;
+
+	// Maximum unsolicited burst length client can receive.
+	int FirstBurstLength;
+} iscsi_session_options;
+
+
+typedef struct iscsi_pdu iscsi_pdu;
+
+
+/// iSCSI connection read packet data return code from iscsi_connection_pdu_read function: Packet parsed successfully.
+#define ISCSI_CONNECT_PDU_READ_OK                                 0
+
+/// iSCSI connection read packet data return code from iscsi_connection_pdu_read function: Fatail error during packet parsing.
+#define ISCSI_CONNECT_PDU_READ_ERR_FATAL                         (-1)
+
+/// iSCSI connection read packet data return code from iscsi_connection_pdu_read function: Login error response.
+#define ISCSI_CONNECT_PDU_READ_ERR_LOGIN_RESPONSE                (-2)
+
+/// iSCSI connection read packet data return code from iscsi_connection_pdu_read function: Login parameter error.
+#define ISCSI_CONNECT_PDU_READ_ERR_LOGIN_PARAMETER               (-3)
+
+/// iSCSI connection read packet data return code from iscsi_connection_pdu_read function: Login parameter not exchanged once error.
+#define ISCSI_CONNECT_PDU_READ_ERR_LOGIN_PARAMETER_XCHG_NOT_ONCE (-4)
+
+
+/// iSCSI connection state: Fresh connection, no login yet.
+#define ISCSI_CONNECT_STATE_NEW 0
+
+/// iSCSI connection state: Running as session type "normal".
+#define ISCSI_CONNECT_STATE_NORMAL_SESSION 1
+
+/// iSCSI connection state: Exiting, teardown of connection imminent.
+#define ISCSI_CONNECT_STATE_EXITING 2
+
+/// iSCSI connection state: Invalid.
+#define ISCSI_CONNECT_STATE_INVALID 3
+
+
+/// Number of attempts for writing to iSCSI connection socket.
+#define ISCSI_CONNECT_SOCKET_WRITE_RETRIES 3
+
+
+/**
+ * @brief iSCSI incoming connection.
+ *
+ * This structure is used for maintaining incoming iSCSI
+ * connections. Negiotiated text key=value pairs are
+ * stored here, status of the connection, session
+ * and iSCSI portals.
+ */
+typedef struct iscsi_connection {
+	/// Associated dnbd3 client
+	dnbd3_client_t *client;
+
+	/// Internal connection identifier
+	int id;
+
+	/// iSCSI connection flags.
+	int flags;
+
+	/// iSCSI connection state.
+	int state;
+
+	/// Initiator Session ID (ISID).
+	iscsi_isid isid;
+
+	/// Target Session Identifying Handle (TSIH).
+	uint16_t tsih;
+
+	/// Connection ID (CID).
+	uint16_t cid;
+
+	/// StatSN.
+	uint32_t stat_sn;
+
+	/// ExpCmdSN.
+	uint32_t exp_cmd_sn;
+
+	/// MaxCmdSN.
+	uint32_t max_cmd_sn;
+
+	/// Session options client sent in login request.
+	iscsi_session_options opts;
+} iscsi_connection;
+
+
+typedef struct iscsi_task iscsi_task;
+
+
+/// iSCSI PDU will contain a small buffer for sending/receiving trivial PDUs with no/very small DS, and small AH
+#define ISCSI_INTERNAL_BUFFER_SIZE (2 * ISCSI_BHS_SIZE)
+
+/**
+ * @brief This structure is used to partially read PDU data.
+ *
+ * Since TCP/IP packets can be fragmented, this
+ * structure is needed which maintains reading
+ * and filling the BHS, AHS and DS properly.
+ */
+typedef struct iscsi_pdu {
+	/// iSCSI Basic Header Segment (BHS) packet data.
+	iscsi_bhs_packet *bhs_pkt;
+
+	/// iSCSI Advanced Header Segment (AHS) packet data for fast access and is straight after BHS packet in memory.
+	iscsi_ahs_packet *ahs_pkt;
+
+	/// iSCSI DataSegment (DS) packet data for fast access and is straight after BHS, AHS and header digest packet in memory.
+	void *ds_cmd_data;
+
+	/// Flags.
+	int flags;
+
+	/// Bytes of Basic Header Segment (BHS) already read.
+	uint bhs_pos;
+
+	/// AHSLength.
+	uint ahs_len;
+
+	/// DataSegmentLength.
+	uint32_t ds_len;
+
+	/// DS Buffer write pos when filling buffer for sending.
+	uint32_t ds_write_pos;
+
+	/// CmdSN.
+	uint32_t cmd_sn;
+
+	/// If we need a larger area than internal_buffer
+	void *big_alloc;
+
+	/// Used for smaller PDUs to avoid extra malloc/free
+	char internal_buffer[ISCSI_INTERNAL_BUFFER_SIZE];
+} iscsi_pdu;
+
+
+/**
+ * @brief This structure is used for iSCSI task management.
+ *
+ * This structure maintains the iSCSI task handling
+ * including the underlying SCSI layer.
+ */
+typedef struct iscsi_task {
+	/// Underlying SCSI task structure.
+	iscsi_scsi_task scsi_task;
+
+	/// Buffer length in bytes.
+	uint32_t len;
+
+	/// LUN identifier associated with this task (always MUST be between 0 and 7), used for hot removal tracking.
+	int lun_id;
+
+	/// Initiator Task Tag (ITT).
+	uint32_t init_task_tag;
+
+	/// Target Transfer Tag (TTT).
+	uint32_t target_xfer_tag;
+} iscsi_task;
+
+void iscsi_connection_handle(dnbd3_client_t *client, const dnbd3_request_t *request, const int len); // Handles an iSCSI connection until connection is closed
+
+#endif /* DNBD3_ISCSI_H_ */