tcp_out.c File Reference

#include "lwip/opt.h"
#include "lwip/priv/tcp_priv.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/ip_addr.h"
#include "lwip/netif.h"
#include "lwip/inet_chksum.h"
#include "lwip/stats.h"
#include "lwip/ip6.h"
#include "lwip/ip6_addr.h"
#include <string.h>

Macros
#define	TCP_CHECKSUM_ON_COPY_SANITY_CHECK   0
#define	TCP_OVERSIZE_CALC_LENGTH(length)   ((length) + TCP_OVERSIZE)

Functions
err_t	tcp_send_fin (struct tcp_pcb *pcb)
err_t	tcp_write (struct tcp_pcb *pcb, const void *arg, u16_t len, u8_t apiflags)
err_t	tcp_enqueue_flags (struct tcp_pcb *pcb, u8_t flags)
err_t	tcp_send_empty_ack (struct tcp_pcb *pcb)
err_t	tcp_output (struct tcp_pcb *pcb)
void	tcp_rst (u32_t seqno, u32_t ackno, const ip_addr_t *local_ip, const ip_addr_t *remote_ip, u16_t local_port, u16_t remote_port)
void	tcp_rexmit_rto (struct tcp_pcb *pcb)
void	tcp_rexmit (struct tcp_pcb *pcb)
void	tcp_rexmit_fast (struct tcp_pcb *pcb)
err_t	tcp_keepalive (struct tcp_pcb *pcb)
err_t	tcp_zero_window_probe (struct tcp_pcb *pcb)

Detailed Description

Transmission Control Protocol, outgoing traffic

The output functions of TCP.

Macro Definition Documentation

TCP_CHECKSUM_ON_COPY_SANITY_CHECK

#define TCP_CHECKSUM_ON_COPY_SANITY_CHECK   0

Define this to 1 for an extra check that the output checksum is valid (usefule when the checksum is generated by the application, not the stack)

TCP_OVERSIZE_CALC_LENGTH

#define TCP_OVERSIZE_CALC_LENGTH

(

length

)

((length) + TCP_OVERSIZE)

The size of segment pbufs created when TCP_OVERSIZE is enabled

Function Documentation

tcp_enqueue_flags()

err_t tcp_enqueue_flags	(	struct tcp_pcb *	pcb,
		u8_t	flags
	)

Enqueue TCP options for transmission.

Called by tcp_connect(), tcp_listen_input(), and tcp_send_ctrl().

Parameters

pcb	Protocol control block for the TCP connection.
flags	TCP header flags to set in the outgoing segment.

tcp_keepalive()

err_t tcp_keepalive

(

struct tcp_pcb *

pcb

)

Send keepalive packets to keep a connection active although no data is sent over it.

Called by tcp_slowtmr()

Parameters

pcb	the tcp_pcb for which to send a keepalive packet

tcp_rexmit()

void tcp_rexmit

(

struct tcp_pcb *

pcb

)

Requeue the first unacked segment for retransmission

Called by tcp_receive() for fast retransmit.

Parameters

pcb	the tcp_pcb for which to retransmit the first unacked segment

tcp_rexmit_fast()

void tcp_rexmit_fast

(

struct tcp_pcb *

pcb

)

Handle retransmission after three dupacks received

Parameters

pcb	the tcp_pcb for which to retransmit the first unacked segment

tcp_rexmit_rto()

void tcp_rexmit_rto

(

struct tcp_pcb *

pcb

)

Requeue all unacked segments for retransmission

Called by tcp_slowtmr() for slow retransmission.

Parameters

pcb	the tcp_pcb for which to re-enqueue all unacked segments

tcp_rst()

void tcp_rst	(	u32_t	seqno,
		u32_t	ackno,
		const ip_addr_t *	local_ip,
		const ip_addr_t *	remote_ip,
		u16_t	local_port,
		u16_t	remote_port
	)

Send a TCP RESET packet (empty segment with RST flag set) either to abort a connection or to show that there is no matching local connection for a received segment.

Called by tcp_abort() (to abort a local connection), tcp_input() (if no matching local pcb was found), tcp_listen_input() (if incoming segment has ACK flag set) and tcp_process() (received segment in the wrong state)

Since a RST segment is in most cases not sent for an active connection, tcp_rst() has a number of arguments that are taken from a tcp_pcb for most other segment output functions.

Parameters

seqno	the sequence number to use for the outgoing segment
ackno	the acknowledge number to use for the outgoing segment
local_ip	the local IP address to send the segment from
remote_ip	the remote IP address to send the segment to
local_port	the local TCP port to send the segment from
remote_port	the remote TCP port to send the segment to

tcp_send_empty_ack()

err_t tcp_send_empty_ack

(

struct tcp_pcb *

pcb

)

Send an ACK without data.

Parameters

pcb	Protocol control block for the TCP connection to send the ACK

tcp_send_fin()

err_t tcp_send_fin

(

struct tcp_pcb *

pcb

)

Called by tcp_close() to send a segment including FIN flag but not data.

Parameters

pcb	the tcp_pcb over which to send a segment

Returns

ERR_OK if sent, another err_t otherwise

tcp_zero_window_probe()

err_t tcp_zero_window_probe

(

struct tcp_pcb *

pcb

)

Send persist timer zero-window probes to keep a connection active when a window update is lost.

Called by tcp_slowtmr()

Parameters

pcb	the tcp_pcb for which to send a zero-window probe packet