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07bc73e087
A window size of 256kB should be sufficient to allow for full-bandwidth transfers over a Gigabit LAN, and for acceptable transfer speeds over other typical links. Signed-off-by: Michael Brown <mcb30@ipxe.org>
383 lines
10 KiB
C
383 lines
10 KiB
C
#ifndef _IPXE_TCP_H
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#define _IPXE_TCP_H
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/** @file
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*
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* TCP protocol
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*
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* This file defines the iPXE TCP API.
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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#include <ipxe/tcpip.h>
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/**
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* A TCP header
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*/
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struct tcp_header {
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uint16_t src; /* Source port */
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uint16_t dest; /* Destination port */
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uint32_t seq; /* Sequence number */
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uint32_t ack; /* Acknowledgement number */
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uint8_t hlen; /* Header length (4), Reserved (4) */
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uint8_t flags; /* Reserved (2), Flags (6) */
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uint16_t win; /* Advertised window */
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uint16_t csum; /* Checksum */
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uint16_t urg; /* Urgent pointer */
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};
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/** @defgroup tcpopts TCP options
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* @{
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*/
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/** End of TCP options list */
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#define TCP_OPTION_END 0
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/** TCP option pad */
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#define TCP_OPTION_NOP 1
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/** Generic TCP option */
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struct tcp_option {
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uint8_t kind;
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uint8_t length;
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} __attribute__ (( packed ));
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/** TCP MSS option */
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struct tcp_mss_option {
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uint8_t kind;
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uint8_t length;
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uint16_t mss;
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} __attribute__ (( packed ));
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/** Code for the TCP MSS option */
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#define TCP_OPTION_MSS 2
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/** TCP window scale option */
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struct tcp_window_scale_option {
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uint8_t kind;
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uint8_t length;
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uint8_t scale;
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} __attribute__ (( packed ));
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/** Padded TCP window scale option (used for sending) */
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struct tcp_window_scale_padded_option {
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uint8_t nop;
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struct tcp_window_scale_option wsopt;
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} __attribute (( packed ));
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/** Code for the TCP window scale option */
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#define TCP_OPTION_WS 3
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/** Advertised TCP window scale
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*
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* Using a scale factor of 2**9 provides for a maximum window of 32MB,
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* which is sufficient to allow Gigabit-speed transfers with a 200ms
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* RTT. The minimum advertised window is 512 bytes, which is still
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* less than a single packet.
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*/
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#define TCP_RX_WINDOW_SCALE 9
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/** TCP timestamp option */
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struct tcp_timestamp_option {
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uint8_t kind;
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uint8_t length;
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uint32_t tsval;
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uint32_t tsecr;
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} __attribute__ (( packed ));
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/** Padded TCP timestamp option (used for sending) */
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struct tcp_timestamp_padded_option {
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uint8_t nop[2];
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struct tcp_timestamp_option tsopt;
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} __attribute__ (( packed ));
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/** Code for the TCP timestamp option */
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#define TCP_OPTION_TS 8
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/** Parsed TCP options */
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struct tcp_options {
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/** MSS option, if present */
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const struct tcp_mss_option *mssopt;
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/** Window scale option, if present */
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const struct tcp_window_scale_option *wsopt;
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/** Timestamp option, if present */
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const struct tcp_timestamp_option *tsopt;
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};
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/** @} */
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/*
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* TCP flags
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*/
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#define TCP_CWR 0x80
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#define TCP_ECE 0x40
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#define TCP_URG 0x20
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#define TCP_ACK 0x10
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#define TCP_PSH 0x08
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#define TCP_RST 0x04
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#define TCP_SYN 0x02
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#define TCP_FIN 0x01
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/**
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* @defgroup tcpstates TCP states
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*
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* The TCP state is defined by a combination of the flags that have
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* been sent to the peer, the flags that have been acknowledged by the
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* peer, and the flags that have been received from the peer.
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*
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* @{
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*/
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/** TCP flags that have been sent in outgoing packets */
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#define TCP_STATE_SENT(flags) ( (flags) << 0 )
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#define TCP_FLAGS_SENT(state) ( ( (state) >> 0 ) & 0xff )
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/** TCP flags that have been acknowledged by the peer
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*
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* Note that this applies only to SYN and FIN.
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*/
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#define TCP_STATE_ACKED(flags) ( (flags) << 8 )
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#define TCP_FLAGS_ACKED(state) ( ( (state) >> 8 ) & 0xff )
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/** TCP flags that have been received from the peer
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*
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* Note that this applies only to SYN and FIN, and that once SYN has
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* been received, we should always be sending ACK.
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*/
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#define TCP_STATE_RCVD(flags) ( (flags) << 16 )
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#define TCP_FLAGS_RCVD(state) ( ( (state) >> 16 ) & 0xff )
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/** TCP flags that are currently being sent in outgoing packets */
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#define TCP_FLAGS_SENDING(state) \
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( TCP_FLAGS_SENT ( state ) & ~TCP_FLAGS_ACKED ( state ) )
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/** CLOSED
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*
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* The connection has not yet been used for anything.
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*/
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#define TCP_CLOSED TCP_RST
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/** LISTEN
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*
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* Not currently used as a state; we have no support for listening
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* connections. Given a unique value to avoid compiler warnings.
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*/
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#define TCP_LISTEN 0
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/** SYN_SENT
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*
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* SYN has been sent, nothing has yet been received or acknowledged.
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*/
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#define TCP_SYN_SENT ( TCP_STATE_SENT ( TCP_SYN ) )
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/** SYN_RCVD
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*
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* SYN has been sent but not acknowledged, SYN has been received.
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*/
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#define TCP_SYN_RCVD ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK ) | \
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TCP_STATE_RCVD ( TCP_SYN ) )
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/** ESTABLISHED
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*
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* SYN has been sent and acknowledged, SYN has been received.
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*/
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#define TCP_ESTABLISHED ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK ) | \
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TCP_STATE_ACKED ( TCP_SYN ) | \
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TCP_STATE_RCVD ( TCP_SYN ) )
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/** FIN_WAIT_1
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*
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* SYN has been sent and acknowledged, SYN has been received, FIN has
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* been sent but not acknowledged, FIN has not been received.
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*
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* RFC 793 shows that we can enter FIN_WAIT_1 without have had SYN
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* acknowledged, i.e. if the application closes the connection after
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* sending and receiving SYN, but before having had SYN acknowledged.
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* However, we have to *pretend* that SYN has been acknowledged
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* anyway, otherwise we end up sending SYN and FIN in the same
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* sequence number slot. Therefore, when we transition from SYN_RCVD
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* to FIN_WAIT_1, we have to remember to set TCP_STATE_ACKED(TCP_SYN)
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* and increment our sequence number.
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*/
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#define TCP_FIN_WAIT_1 ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
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TCP_STATE_ACKED ( TCP_SYN ) | \
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TCP_STATE_RCVD ( TCP_SYN ) )
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/** FIN_WAIT_2
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*
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* SYN has been sent and acknowledged, SYN has been received, FIN has
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* been sent and acknowledged, FIN ha not been received.
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*/
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#define TCP_FIN_WAIT_2 ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
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TCP_STATE_ACKED ( TCP_SYN | TCP_FIN ) | \
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TCP_STATE_RCVD ( TCP_SYN ) )
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/** CLOSING / LAST_ACK
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*
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* SYN has been sent and acknowledged, SYN has been received, FIN has
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* been sent but not acknowledged, FIN has been received.
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*
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* This state actually encompasses both CLOSING and LAST_ACK; they are
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* identical with the definition of state that we use. I don't
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* *believe* that they need to be distinguished.
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*/
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#define TCP_CLOSING_OR_LAST_ACK \
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( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
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TCP_STATE_ACKED ( TCP_SYN ) | \
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TCP_STATE_RCVD ( TCP_SYN | TCP_FIN ) )
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/** TIME_WAIT
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*
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* SYN has been sent and acknowledged, SYN has been received, FIN has
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* been sent and acknowledged, FIN has been received.
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*/
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#define TCP_TIME_WAIT ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK | TCP_FIN ) | \
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TCP_STATE_ACKED ( TCP_SYN | TCP_FIN ) | \
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TCP_STATE_RCVD ( TCP_SYN | TCP_FIN ) )
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/** CLOSE_WAIT
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*
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* SYN has been sent and acknowledged, SYN has been received, FIN has
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* been received.
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*/
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#define TCP_CLOSE_WAIT ( TCP_STATE_SENT ( TCP_SYN | TCP_ACK ) | \
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TCP_STATE_ACKED ( TCP_SYN ) | \
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TCP_STATE_RCVD ( TCP_SYN | TCP_FIN ) )
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/** Can send data in current state
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*
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* We can send data if and only if we have had our SYN acked and we
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* have not yet sent our FIN.
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*/
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#define TCP_CAN_SEND_DATA(state) \
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( ( (state) & ( TCP_STATE_ACKED ( TCP_SYN ) | \
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TCP_STATE_SENT ( TCP_FIN ) ) ) \
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== TCP_STATE_ACKED ( TCP_SYN ) )
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/** Have ever been fully established
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*
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* We have been fully established if we have both received a SYN and
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* had our own SYN acked.
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*/
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#define TCP_HAS_BEEN_ESTABLISHED(state) \
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( ( (state) & ( TCP_STATE_ACKED ( TCP_SYN ) | \
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TCP_STATE_RCVD ( TCP_SYN ) ) ) \
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== ( TCP_STATE_ACKED ( TCP_SYN ) | TCP_STATE_RCVD ( TCP_SYN ) ) )
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/** Have closed gracefully
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*
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* We have closed gracefully if we have both received a FIN and had
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* our own FIN acked.
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*/
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#define TCP_CLOSED_GRACEFULLY(state) \
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( ( (state) & ( TCP_STATE_ACKED ( TCP_FIN ) | \
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TCP_STATE_RCVD ( TCP_FIN ) ) ) \
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== ( TCP_STATE_ACKED ( TCP_FIN ) | TCP_STATE_RCVD ( TCP_FIN ) ) )
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/** @} */
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/** Mask for TCP header length field */
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#define TCP_MASK_HLEN 0xf0
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/** Smallest port number on which a TCP connection can listen */
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#define TCP_MIN_PORT 1
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/**
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* Maxmimum advertised TCP window size
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*
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* The maximum bandwidth on any link is limited by
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*
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* max_bandwidth * round_trip_time = tcp_window
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*
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* Some rough expectations for achievable bandwidths over various
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* links are:
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*
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* a) Gigabit LAN: expected bandwidth 125MB/s, typical RTT 0.5ms,
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* minimum required window 64kB
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*
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* b) Home Internet connection: expected bandwidth 10MB/s, typical
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* RTT 25ms, minimum required window 256kB
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*
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* c) WAN: expected bandwidth 2MB/s, typical RTT 100ms, minimum
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* required window 200kB.
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*
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* The maximum possible value for the TCP window size is 1GB (using
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* the maximum window scale of 2**14). However, it is advisable to
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* keep the window size as small as possible (without limiting
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* bandwidth), since in the event of a lost packet the window size
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* represents the maximum amount that will need to be retransmitted.
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*
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* We therefore choose a maximum window size of 256kB.
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*/
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#define TCP_MAX_WINDOW_SIZE ( 256 * 1024 )
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/**
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* Path MTU
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*
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* We really ought to implement Path MTU discovery. Until we do,
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* anything with a path MTU greater than this may fail.
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*/
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#define TCP_PATH_MTU 1460
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/**
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* Advertised TCP MSS
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*
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* We currently hardcode this to a reasonable value and hope that the
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* sender uses path MTU discovery. The alternative is breaking the
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* abstraction layer so that we can find out the MTU from the IP layer
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* (which would have to find out from the net device layer).
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*/
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#define TCP_MSS 1460
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/** TCP maximum segment lifetime
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*
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* Currently set to 2 minutes, as per RFC 793.
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*/
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#define TCP_MSL ( 2 * 60 * TICKS_PER_SEC )
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/**
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* TCP maximum header length
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*
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*/
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#define TCP_MAX_HEADER_LEN \
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( MAX_LL_NET_HEADER_LEN + \
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sizeof ( struct tcp_header ) + \
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sizeof ( struct tcp_mss_option ) + \
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sizeof ( struct tcp_window_scale_padded_option ) + \
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sizeof ( struct tcp_timestamp_padded_option ) )
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/**
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* Compare TCP sequence numbers
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*
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* @v seq1 Sequence number 1
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* @v seq2 Sequence number 2
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* @ret diff Sequence difference
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*
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* Analogous to memcmp(), returns an integer less than, equal to, or
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* greater than zero if @c seq1 is found, respectively, to be before,
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* equal to, or after @c seq2.
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*/
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static inline __attribute__ (( always_inline )) int32_t
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tcp_cmp ( uint32_t seq1, uint32_t seq2 ) {
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return ( ( int32_t ) ( seq1 - seq2 ) );
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}
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/**
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* Check if TCP sequence number lies within window
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*
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* @v seq Sequence number
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* @v start Start of window
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* @v len Length of window
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* @ret in_window Sequence number is within window
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*/
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static inline int tcp_in_window ( uint32_t seq, uint32_t start,
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uint32_t len ) {
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return ( ( seq - start ) < len );
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}
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extern struct tcpip_protocol tcp_protocol __tcpip_protocol;
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#endif /* _IPXE_TCP_H */
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