tcp_out.c File Reference

Functions
err_t	tcp_send_ctrl (struct tcp_pcb *pcb, u8_t flags)
err_t	tcp_write (struct tcp_pcb *pcb, const void *data, u16_t len, u8_t apiflags)
err_t	tcp_enqueue (struct tcp_pcb *pcb, void *arg, u16_t len, u8_t flags, u8_t apiflags, u8_t *optdata, u8_t optlen)
err_t	tcp_output (struct tcp_pcb *pcb)
void	tcp_rst (u32_t seqno, u32_t ackno, struct ip_addr *local_ip, struct ip_addr *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_keepalive (struct tcp_pcb *pcb)
void	tcp_zero_window_probe (struct tcp_pcb *pcb)

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Detailed Description

Transmission Control Protocol, outgoing traffic

The output functions of TCP.

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Function Documentation

err_t tcp_enqueue	(	struct tcp_pcb *	pcb,
		void *	arg,
		u16_t	len,
		u8_t	flags,
		u8_t	apiflags,
		u8_t *	optdata,
		u8_t	optlen
	)

Enqueue either data or TCP options (but not both) for tranmission

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

Parameters:

	pcb	Protocol control block for the TCP connection to enqueue data for.
	arg	Pointer to the data to be enqueued for sending.
	len	Data length in bytes
	flags	tcp header flags to set in the outgoing segment
	apiflags	combination 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,
	optdata
	optlen

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:

pcb

the 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:

pcb

Protocol 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:

pcb

the 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:

pcb

the tcp_pcb for which to re-enqueue all unacked segments

void tcp_rst	(	u32_t	seqno,
		u32_t	ackno,
		struct ip_addr *	local_ip,
		struct ip_addr *	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

err_t tcp_send_ctrl	(	struct tcp_pcb *	pcb,
		u8_t	flags
	)

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

Parameters:

	pcb	the tcp_pcb over which to send a segment
	flags	the flags to set in the segment header

Returns:

ERR_OK if sent, another err_t otherwise

err_t tcp_write	(	struct tcp_pcb *	pcb,
		const void *	data,
		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:

	pcb	Protocol control block of the TCP connection to enqueue data for.
	data	pointer to the data to send
	len	length (in bytes) of the data to send
	apiflags	combination 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

See also:

tcp_write()

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:

pcb

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

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