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tcp_out.c File Reference

tcp_out.c File Reference

Transmission Control Protocol, outgoing traffic. More...

Go to the source code of this file.

Functions

static void tcp_output_segment (struct tcp_seg *seg, struct tcp_pcb *pcb)
 Called by tcp_output() to actually send a TCP segment over IP.
static struct pbuf * tcp_output_alloc_header (struct tcp_pcb *pcb, u16_t optlen, u16_t datalen, u32_t seqno_be)
 Allocate a pbuf and create a tcphdr at p->payload, used for output functions other than the default tcp_output -> tcp_output_segment (e.g.
err_t tcp_send_fin (struct tcp_pcb *pcb)
 Called by tcp_close() to send a segment including FIN flag but not data.
static struct tcp_seg * tcp_create_segment (struct tcp_pcb *pcb, struct pbuf *p, u8_t flags, u32_t seqno, u8_t optflags)
 Create a TCP segment with prefilled header.
static struct pbuf * tcp_pbuf_prealloc (pbuf_layer layer, u16_t length, u16_t max_length, u16_t *oversize, struct tcp_pcb *pcb, u8_t apiflags, u8_t first_seg)
 Allocate a PBUF_RAM pbuf, perhaps with extra space at the end.
static void tcp_seg_add_chksum (u16_t chksum, u16_t len, u16_t *seg_chksum, u8_t *seg_chksum_swapped)
 Add a checksum of newly added data to the segment.
static err_t tcp_write_checks (struct tcp_pcb *pcb, u16_t len)
 Checks if tcp_write is allowed or not (checks state, snd_buf and snd_queuelen).
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).
err_t tcp_enqueue_flags (struct tcp_pcb *pcb, u8_t flags)
 Enqueue TCP options for transmission.
err_t tcp_send_empty_ack (struct tcp_pcb *pcb)
 Send an ACK without data.
err_t tcp_output (struct tcp_pcb *pcb)
 Find out what we can send and send it.
void tcp_rst (u32_t seqno, u32_t ackno, ip_addr_t *local_ip, 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.
void tcp_rexmit_rto (struct tcp_pcb *pcb)
 Requeue all unacked segments for retransmission.
void tcp_rexmit (struct tcp_pcb *pcb)
 Requeue the first unacked segment for retransmission.
void tcp_rexmit_fast (struct tcp_pcb *pcb)
 Handle retransmission after three dupacks received.
void tcp_keepalive (struct tcp_pcb *pcb)
 Send keepalive packets to keep a connection active although no data is sent over it.
void 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.

Detailed Description

Transmission Control Protocol, outgoing traffic.

The output functions of TCP.

Definition in file tcp_out.c.


Function Documentation

static struct tcp_seg* tcp_create_segment ( struct tcp_pcb *  pcb,
struct pbuf *  p,
u8_t  flags,
u32_t  seqno,
u8_t  optflags 
) [static, read]

Create a TCP segment with prefilled header.

Called by tcp_write and tcp_enqueue_flags.

Parameters:
pcbProtocol control block for the TCP connection.
ppbuf that is used to hold the TCP header.
flagsTCP flags for header.
seqnoTCP sequence number of this packet
optflagsoptions to include in TCP header
Returns:
a new tcp_seg pointing to p, or NULL. The TCP header is filled in except ackno and wnd. p is freed on failure.

Definition at line 156 of file tcp_out.c.

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.
optdatapointer to TCP options, or NULL.
optlenlength of TCP options in bytes.

Definition at line 720 of file tcp_out.c.

void 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

Definition at line 1365 of file tcp_out.c.

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

Definition at line 896 of file tcp_out.c.

static struct pbuf* tcp_output_alloc_header ( struct tcp_pcb *  pcb,
u16_t  optlen,
u16_t  datalen,
u32_t  seqno_be 
) [static, read]

Allocate a pbuf and create a tcphdr at p->payload, used for output functions other than the default tcp_output -> tcp_output_segment (e.g.

tcp_send_empty_ack, etc.)

Parameters:
pcbtcp pcb for which to send a packet (used to initialize tcp_hdr)
optlenlength of header-options
datalenlength of tcp data to reserve in pbuf
seqno_beseqno in network byte order (big-endian)
Returns:
pbuf with p->payload being the tcp_hdr

Definition at line 92 of file tcp_out.c.

static void tcp_output_segment ( struct tcp_seg *  seg,
struct tcp_pcb *  pcb 
) [static]

Called by tcp_output() to actually send a TCP segment over IP.

Parameters:
segthe tcp_seg to send
pcbthe tcp_pcb for the TCP connection used to send the segment

Definition at line 1055 of file tcp_out.c.

static struct pbuf* tcp_pbuf_prealloc ( pbuf_layer  layer,
u16_t  length,
u16_t  max_length,
u16_t *  oversize,
struct tcp_pcb *  pcb,
u8_t  apiflags,
u8_t  first_seg 
) [static, read]

Allocate a PBUF_RAM pbuf, perhaps with extra space at the end.

This function is like pbuf_alloc(layer, length, PBUF_RAM) except there may be extra bytes available at the end.

Parameters:
layerflag to define header size.
lengthsize of the pbuf's payload.
max_lengthmaximum usable size of payload+oversize.
oversizepointer to a u16_t that will receive the number of usable tail bytes.
pcbThe TCP connection that willo enqueue the pbuf.
apiflagsAPI flags given to tcp_write.
first_segtrue when this pbuf will be used in the first enqueued segment.

Definition at line 217 of file tcp_out.c.

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

Definition at line 1282 of file tcp_out.c.

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

Definition at line 1322 of file tcp_out.c.

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

Definition at line 1247 of file tcp_out.c.

void tcp_rst ( u32_t  seqno,
u32_t  ackno,
ip_addr_t *  local_ip,
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

Definition at line 1203 of file tcp_out.c.

static void tcp_seg_add_chksum ( u16_t  chksum,
u16_t  len,
u16_t *  seg_chksum,
u8_t *  seg_chksum_swapped 
) [static]

Add a checksum of newly added data to the segment.

Definition at line 270 of file tcp_out.c.

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

Definition at line 840 of file tcp_out.c.

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

Definition at line 123 of file tcp_out.c.

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 be set on last segment sent,
Returns:
ERR_OK if enqueued, another err_t on error

Definition at line 352 of file tcp_out.c.

static err_t tcp_write_checks ( struct tcp_pcb *  pcb,
u16_t  len 
) [static]

Checks if tcp_write is allowed or not (checks state, snd_buf and snd_queuelen).

Parameters:
pcbthe tcp pcb to check for
lenlength of data to send (checked agains snd_buf)
Returns:
ERR_OK if tcp_write is allowed to proceed, another err_t otherwise

Definition at line 292 of file tcp_out.c.

void 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

Definition at line 1415 of file tcp_out.c.