lwIP 2.0.0  lwIP 2.0.0
LightweightIPstack
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

#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)

#define TCP_OVERSIZE_CALC_LENGTH (   length)    ((length) + TCP_OVERSIZE)

The size of segment pbufs created when TCP_OVERSIZE is enabled

Function Documentation

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
pcbProtocol control block for the TCP connection.
flagsTCP header flags to set in the outgoing segment.
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
pcbthe tcp_pcb for which to send a keepalive packet
err_t tcp_output ( struct tcp_pcb pcb)

Find out what we can send and send it

Parameters
pcbProtocol control block for the TCP connection to send data
Returns
ERR_OK if data has been sent or nothing to send another err_t on error
void tcp_rexmit ( struct tcp_pcb pcb)

Requeue the first unacked segment for retransmission

Called by tcp_receive() for fast retramsmit.

Parameters
pcbthe tcp_pcb for which to retransmit the first unacked segment
void tcp_rexmit_fast ( struct tcp_pcb pcb)

Handle retransmission after three dupacks received

Parameters
pcbthe tcp_pcb for which to retransmit the first unacked segment
void tcp_rexmit_rto ( struct tcp_pcb pcb)

Requeue all unacked segments for retransmission

Called by tcp_slowtmr() for slow retransmission.

Parameters
pcbthe tcp_pcb for which to re-enqueue all unacked segments
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
seqnothe sequence number to use for the outgoing segment
acknothe acknowledge number to use for the outgoing segment
local_ipthe local IP address to send the segment from
remote_ipthe remote IP address to send the segment to
local_portthe local TCP port to send the segment from
remote_portthe remote TCP port to send the segment to
err_t tcp_send_empty_ack ( struct tcp_pcb pcb)

Send an ACK without data.

Parameters
pcbProtocol control block for the TCP connection to send the ACK
err_t tcp_send_fin ( struct tcp_pcb pcb)

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

Parameters
pcbthe tcp_pcb over which to send a segment
Returns
ERR_OK if sent, another err_t otherwise
err_t tcp_write ( struct tcp_pcb pcb,
const void *  arg,
u16_t  len,
u8_t  apiflags 
)

Write data for sending (but does not send it immediately).

It waits in the expectation of more data being sent soon (as it can send them more efficiently by combining them together). To prompt the system to send data now, call tcp_output() after calling tcp_write().

Parameters
pcbProtocol control block for the TCP connection to enqueue data for.
argPointer to the data to be enqueued for sending.
lenData length in bytes
apiflagscombination of following flags :
  • TCP_WRITE_FLAG_COPY (0x01) data will be copied into memory belonging to the stack
  • TCP_WRITE_FLAG_MORE (0x02) for TCP connection, PSH flag will not be set on last segment sent,
Returns
ERR_OK if enqueued, another err_t on error
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
pcbthe tcp_pcb for which to send a zero-window probe packet