[SERVER] iscsi: Implement relaying requests to uplink servers

2 files changed, 69 insertions, 3 deletions

diff --git a/src/server/iscsi.c b/src/server/iscsi.c
index b44f695..c634013 100644
--- a/src/server/iscsi.c
+++ b/src/server/iscsi.c
@@ -46,7 +46,9 @@
 #include "ini.h"
 #include "iscsi.h"
 #include "locks.h"
+#include "uplink.h"
 #include "threadpool.h"
+#include "reference.h"
 
 /**
  * @file iscsi.c
@@ -1310,7 +1312,7 @@ int iscsi_create()
 		}
 
 		globvec->flags                          = (ISCSI_GLOBALS_FLAGS_INIT_R2T | ISCSI_GLOBALS_FLAGS_IMMEDIATE_DATA | ISCSI_GLOBALS_FLAGS_DATA_PDU_IN_ORDER | ISCSI_GLOBALS_FLAGS_DATA_SEQ_IN_ORDER | ISCSI_GLOBALS_FLAGS_SCSI_IO_REMOVABLE | ISCSI_GLOBALS_FLAGS_SCSI_IO_WRITE_PROTECT);
-		globvec->target_name_check              = ISCSI_GLOBALS_TARGET_NAME_CHECK_FULL;
+		globvec->target_name_check              = ISCSI_GLOBALS_TARGET_NAME_CHECK_RELAXED;
 		globvec->max_sessions                   = 0U;
 		globvec->header_digest                  = 0;
 		globvec->data_digest                    = 0;
@@ -5269,6 +5271,25 @@ static uint64_t iscsi_scsi_emu_blocks_to_bytes(uint64_t *offset_bytes, const uin
 }
 
 /**
+ * @brief Called when data requested via an uplink server has arrived.
+ *
+ * @param[in] data related scsi_task
+ * @param[in] handle pointer to destination buffer, as passed to iscsi_scsi_emu_io_block_read()
+ * @param[in] start start of range in bytes
+ * @param[in] length length of range in bytes, as passed to uplink_request()
+ * @param[in] buffer data for requested range
+ */
+static void iscsi_uplink_callback(void *data, uint64_t handle, uint64_t start UNUSED, uint32_t length, const char *buffer)
+{
+	iscsi_scsi_task *scsi_task = (iscsi_scsi_task*)data;
+
+	memcpy( (uint8_t*)handle, buffer, length );
+	pthread_mutex_lock( &scsi_task->up_mutex );
+	pthread_cond_signal( &scsi_task->up_cond );
+	pthread_mutex_unlock( &scsi_task->up_mutex );
+}
+
+/**
  * @brief Reads a number of blocks from a block offset of a DNBD3 image to a specified buffer.
  *
  * This function enqueues the I/O read
@@ -5301,8 +5322,6 @@ int iscsi_scsi_emu_io_block_read(iscsi_scsi_task *scsi_task, uint8_t *buf, dnbd3
 {
 	uint64_t offset_bytes;
 	const uint64_t num_bytes                = iscsi_scsi_emu_blocks_to_bytes( &offset_bytes, offset_blocks, num_blocks, block_size );
-	const int64_t len                       = pread( image->readFd, buf, (size_t) num_bytes, offset_bytes );
-	const bool success                      = ((uint64_t) len == num_bytes);
 	iscsi_connection_exec_queue *exec_queue = (iscsi_connection_exec_queue *) malloc( sizeof(struct iscsi_connection_exec_queue) );
 
 	if ( exec_queue == NULL ) {
@@ -5311,6 +5330,47 @@ int iscsi_scsi_emu_io_block_read(iscsi_scsi_task *scsi_task, uint8_t *buf, dnbd3
 		return -ENOMEM;
 	}
 
+	dnbd3_cache_map_t *cache = ref_get_cachemap( image );
+	bool readFromFile;
+
+	if ( cache == NULL ) {
+		readFromFile = true;
+	} else {
+		// This is a proxyed image, check if we need to relay the request...
+		const uint64_t start = offset_bytes & ~(uint64_t)(DNBD3_BLOCK_SIZE - 1);
+		const uint64_t end = (offset_bytes + num_bytes + DNBD3_BLOCK_SIZE - 1) & ~(uint64_t)(DNBD3_BLOCK_SIZE - 1);
+		readFromFile = image_isRangeCachedUnsafe( cache, start, end );
+		ref_put( &cache->reference );
+
+		if ( !readFromFile ) {
+			// Not cached, request via uplink
+			pthread_mutex_init( &scsi_task->up_mutex, NULL );
+			pthread_cond_init( &scsi_task->up_cond, NULL );
+			pthread_mutex_lock( &scsi_task->up_mutex );
+			if ( !uplink_request( image, scsi_task, &iscsi_uplink_callback, (uint64_t)buf, offset_bytes, num_bytes ) ) {
+				pthread_mutex_unlock( &scsi_task->up_mutex );
+				pthread_cond_destroy( &scsi_task->up_cond );
+				pthread_mutex_destroy( &scsi_task->up_mutex );
+				logadd( LOG_DEBUG1, "Could not relay uncached request to upstream proxy for image %s:%d",
+						image->name, image->rid );
+				return -EIO;
+			}
+			// Wait sync (Maybe use pthread_cond_timedwait to detect unavailable uplink instead of hanging...)
+			pthread_cond_wait( &scsi_task->up_cond, &scsi_task->up_mutex );
+			pthread_mutex_unlock( &scsi_task->up_mutex );
+			pthread_cond_destroy( &scsi_task->up_cond );
+			pthread_mutex_destroy( &scsi_task->up_mutex );
+		}
+	}
+
+	bool success;
+	if ( readFromFile ) {
+		const int64_t len          = pread( image->readFd, buf, (size_t) num_bytes, offset_bytes );
+		success                    = ((uint64_t) len == num_bytes);
+	} else {
+		success                    = true;
+	}
+
 	exec_queue->data.io.callback  = callback;
 	exec_queue->data.io.image     = image;
 	exec_queue->data.io.user_data = user_data;
diff --git a/src/server/iscsi.h b/src/server/iscsi.h
index 193b292..4c284e0 100644
--- a/src/server/iscsi.h
+++ b/src/server/iscsi.h
@@ -10858,6 +10858,12 @@ typedef struct iscsi_scsi_task {
 
     /// Task management response code.
     uint8_t task_mgmt_response;
+
+    /// Uplink read mutex for sync
+    pthread_mutex_t up_mutex;
+
+    /// Conditional to signal uplink read complete
+    pthread_cond_t up_cond;
 } iscsi_scsi_task;