#ifndef _IPXE_TCP_H
#define _IPXE_TCP_H
/** @file
*
* TCP protocol
*
* This file defines the iPXE TCP API.
*
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <ipxe/tcpip.h>
/**
* A TCP header
*/
struct tcp_header {
uint16_t src; /* Source port */
uint16_t dest; /* Destination port */
uint32_t seq; /* Sequence number */
uint32_t ack; /* Acknowledgement number */
uint8_t hlen; /* Header length (4), Reserved (4) */
uint8_t flags; /* Reserved (2), Flags (6) */
uint16_t win; /* Advertised window */
uint16_t csum; /* Checksum */
uint16_t urg; /* Urgent pointer */
} __attribute__ (( packed ));
/** @defgroup tcpopts TCP options
* @{
*/
/** End of TCP options list */
#define TCP_OPTION_END 0
/** TCP option pad */
#define TCP_OPTION_NOP 1
/** Generic TCP option */
struct tcp_option {
uint8_t kind;
uint8_t length;
} __attribute__ (( packed ));
/** TCP MSS option */
struct tcp_mss_option {
uint8_t kind;
uint8_t length;
uint16_t mss;
} __attribute__ (( packed ));
/** Code for the TCP MSS option */
#define TCP_OPTION_MSS 2
/** TCP window scale option */
struct tcp_window_scale_option {
uint8_t kind;
uint8_t length;
uint8_t scale;
} __attribute__ (( packed ));
/** Padded TCP window scale option (used for sending) */
struct tcp_window_scale_padded_option {
uint8_t nop;
struct tcp_window_scale_option wsopt;
} __attribute (( packed ));
/** Code for the TCP window scale option */
#define TCP_OPTION_WS 3
/** Advertised TCP window scale
*
* Using a scale factor of 2**9 provides for a maximum window of 32MB,
* which is sufficient to allow Gigabit-speed transfers with a 200ms
* RTT. The minimum advertised window is 512 bytes, which is still
* less than a single packet.
*/
#define TCP_RX_WINDOW_SCALE 9
/** TCP selective acknowledgement permitted option */
struct tcp_sack_permitted_option {
uint8_t kind;
uint8_t length;
} __attribute__ (( packed ));
/** Padded TCP selective acknowledgement permitted option (used for sending) */
struct tcp_sack_permitted_padded_option {
uint8_t nop[2];
struct tcp_sack_permitted_option spopt;
} __attribute__ (( packed ));
/** Code for the TCP selective acknowledgement permitted option */
#define TCP_OPTION_SACK_PERMITTED 4
/** TCP selective acknowledgement option */
struct tcp_sack_option {
uint8_t kind;
uint8_t length;
} __attribute__ (( packed ));
/** TCP selective acknowledgement block */
struct tcp_sack_block {
uint32_t left;
uint32_t right;
} __attribute__ (( packed ));
/** Maximum number of selective acknowledgement blocks
*
* This allows for the presence of the TCP timestamp option.
*/
#define TCP_SACK_MAX 3
/** Padded TCP selective acknowledgement option (used for sending) */
struct tcp_sack_padded_option {
uint8_t nop[2];
struct tcp_sack_option sackopt;
} __attribute__ (( packed ));
/** Code for the TCP selective acknowledgement option */
#define TCP_OPTION_SACK 5
/** TCP timestamp option */
struct tcp_timestamp_option {
uint8_t kind;
uint8_t length;
uint32_t tsval;
uint32_t tsecr;
} __attribute__ (( packed ));
/** Padded TCP timestamp option (used for sending) */
struct tcp_timestamp_padded_option {
uint8_t nop[2];
struct tcp_timestamp_option tsopt;
} __attribute__ (( packed ));
/** Code for the TCP timestamp option */
#define TCP_OPTION_TS 8
/** Parsed TCP options */
struct tcp_options {
/** Window scale option, if present */
const struct tcp_window_scale_option *wsopt;
/** SACK permitted option, if present */
const struct tcp_sack_permitted_option *spopt;
/** Timestamp option, if present */
const struct tcp_timestamp_option *tsopt;
};
/** @} */
/*
* TCP flags
*/
#define TCP_CWR 0x80
#define TCP_ECE 0x40
#define TCP_URG 0x20
#define TCP_ACK 0x10
#define TCP_PSH 0x08
#define TCP_RST 0x04
#define TCP_SYN 0x02
#define TCP_FIN 0x01
/**
* @defgroup tcpstates TCP states
*
* The TCP state is defined by a combination of the flags that have
* been sent to the peer, the flags that have been acknowledged by the
* peer, and the flags that have been received from the peer.
*
* @{
*/
/** TCP flags that have been sent in outgoing packets */
#define TCP_STATE_SENT(flags) ( (flags) << 0 )
#define TCP_FLAGS_SENT(state) ( ( (state) >> 0 ) & 0xff )
/** TCP flags that have been acknowledged by the peer
*
* Note that this applies only to SYN and FIN.
*/
#define TCP_STATE_ACKED(flags) ( (flags) << 8 )
#define TCP_FLAGS_ACKED(state) ( ( (state) >> 8 ) & 0xff )
/** TCP flags that have been received from the peer
*
* Note that this applies only to SYN and FIN, and that once SYN has
* been received, we should always be sending ACK.
*/
#define TCP_STATE_RCVD(flags) ( (flags) << 16 )
#define TCP_FLAGS_RCVD(state) ( ( (state) >> 16 ) & 0xff )
/** TCP flags that are currently being sent in outgoing packets */
#define TCP_FLAGS_SENDING(state) \
( TCP_FLAGS_SENT ( state ) & ~TCP_FLAGS_ACKED ( state ) )
/** CLOSED
*
* The connection has not yet been used for anything.
*/
#define TCP_CLOSED TCP_RST
/** LISTEN
*
* Not currently used as a state; we have no support for listening
* connections. Given a unique value to avoid compiler warnings.
*/
#define TCP_LISTEN 0
/** SYN_SENT
*
* SYN has been sent, nothing has yet been received or acknowledged.
*/
#define TCP_SYN_SENT ( TCP_STATE_SENT ( TCP_SYN ) )
/** SYN_RCVD
*
* SYN has been sent but not acknowledged, SYN has been received.
*/
#define TCP_SYN_RCVD ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK ) | \
TCP_STATE_RCVD ( TCP_SYN ) )
/** ESTABLISHED
*
* SYN has been sent and acknowledged, SYN has been received.
*/
#define TCP_ESTABLISHED ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK ) | \
TCP_STATE_ACKED ( TCP_SYN ) | \
TCP_STATE_RCVD ( TCP_SYN ) )
/** FIN_WAIT_1
*
* SYN has been sent and acknowledged, SYN has been received, FIN has
* been sent but not acknowledged, FIN has not been received.
*
* RFC 793 shows that we can enter FIN_WAIT_1 without have had SYN
* acknowledged, i.e. if the application closes the connection after
* sending and receiving SYN, but before having had SYN acknowledged.
* However, we have to *pretend* that SYN has been acknowledged
* anyway, otherwise we end up sending SYN and FIN in the same
* sequence number slot. Therefore, when we transition from SYN_RCVD
* to FIN_WAIT_1, we have to remember to set TCP_STATE_ACKED(TCP_SYN)
* and increment our sequence number.
*/
#define TCP_FIN_WAIT_1 ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
TCP_STATE_ACKED ( TCP_SYN ) | \
TCP_STATE_RCVD ( TCP_SYN ) )
/** FIN_WAIT_2
*
* SYN has been sent and acknowledged, SYN has been received, FIN has
* been sent and acknowledged, FIN ha not been received.
*/
#define TCP_FIN_WAIT_2 ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
TCP_STATE_ACKED ( TCP_SYN | TCP_FIN ) | \
TCP_STATE_RCVD ( TCP_SYN ) )
/** CLOSING / LAST_ACK
*
* SYN has been sent and acknowledged, SYN has been received, FIN has
* been sent but not acknowledged, FIN has been received.
*
* This state actually encompasses both CLOSING and LAST_ACK; they are
* identical with the definition of state that we use. I don't
* *believe* that they need to be distinguished.
*/
#define TCP_CLOSING_OR_LAST_ACK \
( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
TCP_STATE_ACKED ( TCP_SYN ) | \
TCP_STATE_RCVD ( TCP_SYN | TCP_FIN ) )
/** TIME_WAIT
*
* SYN has been sent and acknowledged, SYN has been received, FIN has
* been sent and acknowledged, FIN has been received.
*/
#define TCP_TIME_WAIT ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
TCP_STATE_ACKED ( TCP_SYN | TCP_FIN ) | \
TCP_STATE_RCVD ( TCP_SYN | TCP_FIN ) )
/** CLOSE_WAIT
*
* SYN has been sent and acknowledged, SYN has been received, FIN has
* been received.
*/
#define TCP_CLOSE_WAIT ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK ) | \
TCP_STATE_ACKED ( TCP_SYN ) | \
TCP_STATE_RCVD ( TCP_SYN | TCP_FIN ) )
/** Can send data in current state
*
* We can send data if and only if we have had our SYN acked and we
* have not yet sent our FIN.
*/
#define TCP_CAN_SEND_DATA(state) \
( ( (state) & ( TCP_STATE_ACKED ( TCP_SYN ) | \
TCP_STATE_SENT ( TCP_FIN ) ) ) \
== TCP_STATE_ACKED ( TCP_SYN ) )
/** Have ever been fully established
*
* We have been fully established if we have both received a SYN and
* had our own SYN acked.
*/
#define TCP_HAS_BEEN_ESTABLISHED(state) \
( ( (state) & ( TCP_STATE_ACKED ( TCP_SYN ) | \
TCP_STATE_RCVD ( TCP_SYN ) ) ) \
== ( TCP_STATE_ACKED ( TCP_SYN ) | TCP_STATE_RCVD ( TCP_SYN ) ) )
/** Have closed gracefully
*
* We have closed gracefully if we have both received a FIN and had
* our own FIN acked.
*/
#define TCP_CLOSED_GRACEFULLY(state) \
( ( (state) & ( TCP_STATE_ACKED ( TCP_FIN ) | \
TCP_STATE_RCVD ( TCP_FIN ) ) ) \
== ( TCP_STATE_ACKED ( TCP_FIN ) | TCP_STATE_RCVD ( TCP_FIN ) ) )
/** @} */
/** Mask for TCP header length field */
#define TCP_MASK_HLEN 0xf0
/** Smallest port number on which a TCP connection can listen */
#define TCP_MIN_PORT 1
/**
* Maxmimum advertised TCP window size
*
* The maximum bandwidth on any link is limited by
*
* max_bandwidth * round_trip_time = tcp_window
*
* Some rough expectations for achievable bandwidths over various
* links are:
*
* a) Gigabit LAN: expected bandwidth 125MB/s, typical RTT 0.5ms,
* minimum required window 64kB
*
* b) Home Internet connection: expected bandwidth 10MB/s, typical
* RTT 25ms, minimum required window 256kB
*
* c) WAN: expected bandwidth 2MB/s, typical RTT 100ms, minimum
* required window 200kB.
*
* The maximum possible value for the TCP window size is 1GB (using
* the maximum window scale of 2**14). However, it is advisable to
* keep the window size as small as possible (without limiting
* bandwidth), since in the event of a lost packet the window size
* represents the maximum amount that will need to be retransmitted.
*
* We therefore choose a maximum window size of 256kB.
*/
#define TCP_MAX_WINDOW_SIZE ( 256 * 1024 )
/**
* Path MTU
*
* IPv6 requires all data link layers to support a datagram size of
* 1280 bytes. We choose to use this as our maximum transmitted
* datagram size, on the assumption that any practical link layer we
* encounter will allow this size. This is a very conservative
* assumption in practice, but the impact of making such a
* conservative assumption is insignificant since the amount of data
* that we transmit (rather than receive) is negligible.
*
* We allow space within this 1280 bytes for an IPv6 header, a TCP
* header, and a (padded) TCP timestamp option.
*/
#define TCP_PATH_MTU \
( 1280 - 40 /* IPv6 */ - 20 /* TCP */ - 12 /* TCP timestamp */ )
/** TCP maximum segment lifetime
*
* Currently set to 2 minutes, as per RFC 793.
*/
#define TCP_MSL ( 2 * 60 * TICKS_PER_SEC )
/**
* TCP keepalive period
*
* We send keepalive ACKs after this period of inactivity has elapsed
* on an established connection.
*/
#define TCP_KEEPALIVE_DELAY ( 15 * TICKS_PER_SEC )
/**
* TCP maximum header length
*
*/
#define TCP_MAX_HEADER_LEN \
( MAX_LL_NET_HEADER_LEN + \
sizeof ( struct tcp_header ) + \
sizeof ( struct tcp_mss_option ) + \
sizeof ( struct tcp_window_scale_padded_option ) + \
sizeof ( struct tcp_timestamp_padded_option ) )
/**
* Compare TCP sequence numbers
*
* @v seq1 Sequence number 1
* @v seq2 Sequence number 2
* @ret diff Sequence difference
*
* Analogous to memcmp(), returns an integer less than, equal to, or
* greater than zero if @c seq1 is found, respectively, to be before,
* equal to, or after @c seq2.
*/
static inline __attribute__ (( always_inline )) int32_t
tcp_cmp ( uint32_t seq1, uint32_t seq2 ) {
return ( ( int32_t ) ( seq1 - seq2 ) );
}
/**
* Check if TCP sequence number lies within window
*
* @v seq Sequence number
* @v start Start of window
* @v len Length of window
* @ret in_window Sequence number is within window
*/
static inline int tcp_in_window ( uint32_t seq, uint32_t start,
uint32_t len ) {
return ( ( seq - start ) < len );
}
/** TCP finish wait time
*
* Currently set to one second, since we should not allow a slowly
* responding server to substantially delay a call to shutdown().
*/
#define TCP_FINISH_TIMEOUT ( 1 * TICKS_PER_SEC )
extern struct tcpip_protocol tcp_protocol __tcpip_protocol;
#endif /* _IPXE_TCP_H */
