tcp_priv.h File Reference

#include "lwip/opt.h"
#include "lwip/tcp.h"
#include "lwip/mem.h"
#include "lwip/pbuf.h"
#include "lwip/ip.h"
#include "lwip/icmp.h"
#include "lwip/err.h"
#include "lwip/ip6.h"
#include "lwip/ip6_addr.h"
#include "lwip/prot/tcp.h"

Macros
#define	tcp_do_output_nagle(tpcb)
#define	TF_RESET   (u8_t)0x08U /* Connection was reset. */
#define	TCP_OVERSIZE_DBGCHECK   0
#define	TCP_CHECKSUM_ON_COPY   (LWIP_CHECKSUM_ON_COPY && CHECKSUM_GEN_TCP)
#define	TCP_BUILD_MSS_OPTION(mss)

Functions
void	tcp_init (void)
void	tcp_tmr (void)
void	tcp_slowtmr (void)
void	tcp_fasttmr (void)
void	tcp_txnow (void)
void	tcp_input (struct pbuf *p, struct netif *inp)
struct tcp_pcb *	tcp_alloc (u8_t prio)
void	tcp_free (struct tcp_pcb *pcb)
void	tcp_abandon (struct tcp_pcb *pcb, int reset)
err_t	tcp_send_empty_ack (struct tcp_pcb *pcb)
err_t	tcp_rexmit (struct tcp_pcb *pcb)
err_t	tcp_rexmit_rto_prepare (struct tcp_pcb *pcb)
void	tcp_rexmit_rto_commit (struct tcp_pcb *pcb)
void	tcp_rexmit_rto (struct tcp_pcb *pcb)
void	tcp_rexmit_fast (struct tcp_pcb *pcb)
u32_t	tcp_update_rcv_ann_wnd (struct tcp_pcb *pcb)
err_t	tcp_process_refused_data (struct tcp_pcb *pcb)
void	tcp_pcb_purge (struct tcp_pcb *pcb)
void	tcp_pcb_remove (struct tcp_pcb **pcblist, struct tcp_pcb *pcb)
void	tcp_segs_free (struct tcp_seg *seg)
void	tcp_seg_free (struct tcp_seg *seg)
struct tcp_seg *	tcp_seg_copy (struct tcp_seg *seg)
err_t	tcp_send_fin (struct tcp_pcb *pcb)
err_t	tcp_enqueue_flags (struct tcp_pcb *pcb, u8_t flags)
void	tcp_rst (const struct tcp_pcb *pcb, 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_rst_netif (struct netif *netif, 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)
u32_t	tcp_next_iss (struct tcp_pcb *pcb)
err_t	tcp_keepalive (struct tcp_pcb *pcb)
err_t	tcp_split_unsent_seg (struct tcp_pcb *pcb, u16_t split)
err_t	tcp_zero_window_probe (struct tcp_pcb *pcb)
u16_t	tcp_eff_send_mss_netif (u16_t sendmss, struct netif *outif, const ip_addr_t *dest)
err_t	tcp_recv_null (void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
void	tcp_timer_needed (void)
void	tcp_netif_ip_addr_changed (const ip_addr_t *old_addr, const ip_addr_t *new_addr)
err_t	tcp_ext_arg_invoke_callbacks_passive_open (struct tcp_pcb_listen *lpcb, struct tcp_pcb *cpcb)

Variables
struct tcp_pcb *	tcp_bound_pcbs
union tcp_listen_pcbs_t	tcp_listen_pcbs
struct tcp_pcb *	tcp_active_pcbs
struct tcp_pcb *	tcp_tw_pcbs
struct tcp_pcb **const	tcp_pcb_lists [4]

Detailed Description

TCP internal implementations (do not use in application code)

Macro Definition Documentation

TCP_BUILD_MSS_OPTION

#define TCP_BUILD_MSS_OPTION

(

mss

)

Value:

lwip_htonl(0x02040000 | ((mss) & 0xFFFF))

This returns a TCP header option for MSS in an u32_t

TCP_CHECKSUM_ON_COPY

#define TCP_CHECKSUM_ON_COPY   (LWIP_CHECKSUM_ON_COPY && CHECKSUM_GEN_TCP)

Don't generate checksum on copy if CHECKSUM_GEN_TCP is disabled

tcp_do_output_nagle

#define tcp_do_output_nagle

(

tpcb

)

Value:

                            ((((tpcb)->unacked == NULL) || \
                            ((tpcb)->flags & (TF_NODELAY | TF_INFR)) || \
                            (((tpcb)->unsent != NULL) && (((tpcb)->unsent->next != NULL) || \
                              ((tpcb)->unsent->len >= (tpcb)->mss))) || \
                            ((tcp_sndbuf(tpcb) == 0) || (tcp_sndqueuelen(tpcb) >= TCP_SND_QUEUELEN)) \
                            ) ? 1 : 0)

This is the Nagle algorithm: try to combine user data to send as few TCP segments as possible. Only send if

• no previously transmitted data on the connection remains unacknowledged or
• the TF_NODELAY flag is set (nagle algorithm turned off for this pcb) or
• the only unsent segment is at least pcb->mss bytes long (or there is more than one unsent segment - with lwIP, this can happen although unsent->len < mss)
• or if we are in fast-retransmit (TF_INFR)

TCP_OVERSIZE_DBGCHECK

#define TCP_OVERSIZE_DBGCHECK   0

Enabled extra-check for TCP_OVERSIZE if LWIP_DEBUG is enabled

TF_RESET

#define TF_RESET   (u8_t)0x08U /* Connection was reset. */

Flags used on input processing, not on pcb->flags

Function Documentation

tcp_abandon()

void tcp_abandon	(	struct tcp_pcb *	pcb,
		int	reset )

Abandons a connection and optionally sends a RST to the remote host. Deletes the local protocol control block. This is done when a connection is killed because of shortage of memory.

Parameters

pcb	the tcp_pcb to abort
reset	boolean to indicate whether a reset should be sent

tcp_alloc()

struct tcp_pcb * tcp_alloc

(

u8_t

prio

)

Allocate a new tcp_pcb structure.

Parameters

prio	priority for the new pcb

Returns

a new tcp_pcb that initially is in state CLOSED

tcp_eff_send_mss_netif()

u16_t tcp_eff_send_mss_netif	(	u16_t	sendmss,
		struct netif *	outif,
		const ip_addr_t *	dest )

Calculates the effective send mss that can be used for a specific IP address by calculating the minimum of TCP_MSS and the mtu (if set) of the target netif (if not NULL).

tcp_enqueue_flags()

err_t tcp_enqueue_flags	(	struct tcp_pcb *	pcb,
		u8_t	flags )

Enqueue SYN or FIN for transmission.

Called by tcp_connect, tcp_listen_input, and tcp_close (via tcp_send_fin)

Parameters

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

tcp_ext_arg_invoke_callbacks_passive_open()

err_t tcp_ext_arg_invoke_callbacks_passive_open	(	struct tcp_pcb_listen *	lpcb,
		struct tcp_pcb *	cpcb )

This function calls the "passive_open" callback for all ext_args if a connection is in the process of being accepted. This is called just after the SYN is received and before a SYN/ACK is sent, to allow to modify the very first segment sent even on passive open. Naturally, the "accepted" callback of the pcb has not been called yet!

tcp_fasttmr()

void tcp_fasttmr

(

void

)

Is called every TCP_FAST_INTERVAL (250 ms) and process data previously "refused" by upper layer (application) and sends delayed ACKs or pending FINs.

Automatically called from tcp_tmr().

tcp_free()

void tcp_free

(

struct tcp_pcb *

pcb

)

Free a tcp pcb

tcp_init()

void tcp_init

(

void

)

Initialize this module.

tcp_input()

void tcp_input	(	struct pbuf *	p,
		struct netif *	inp )

The initial input processing of TCP. It verifies the TCP header, demultiplexes the segment between the PCBs and passes it on to tcp_process(), which implements the TCP finite state machine. This function is called by the IP layer (in ip_input()).

Parameters

p	received TCP segment to process (p->payload pointing to the TCP header)
inp	network interface on which this segment was received

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_netif_ip_addr_changed()

void tcp_netif_ip_addr_changed	(	const ip_addr_t *	old_addr,
		const ip_addr_t *	new_addr )

This function is called from netif.c when address is changed or netif is removed

Parameters

old_addr	IP address of the netif before change
new_addr	IP address of the netif after change or NULL if netif has been removed

tcp_next_iss()

u32_t tcp_next_iss

(

struct tcp_pcb *

pcb

)

Calculates a new initial sequence number for new connections.

Returns

u32_t pseudo random sequence number

tcp_pcb_purge()

void tcp_pcb_purge

(

struct tcp_pcb *

pcb

)

Purges a TCP PCB. Removes any buffered data and frees the buffer memory (pcb->ooseq, pcb->unsent and pcb->unacked are freed).

Parameters

pcb	tcp_pcb to purge. The pcb itself is not deallocated!

tcp_pcb_remove()

void tcp_pcb_remove	(	struct tcp_pcb **	pcblist,
		struct tcp_pcb *	pcb )

Purges the PCB and removes it from a PCB list. Any delayed ACKs are sent first.

Parameters

pcblist	PCB list to purge.
pcb	tcp_pcb to purge. The pcb itself is NOT deallocated!

tcp_process_refused_data()

err_t tcp_process_refused_data

(

struct tcp_pcb *

pcb

)

Pass pcb->refused_data to the recv callback

tcp_recv_null()

err_t tcp_recv_null	(	void *	arg,
		struct tcp_pcb *	pcb,
		struct pbuf *	p,
		err_t	err )

Default receive callback that is called if the user didn't register a recv callback for the pcb.

tcp_rexmit()

err_t 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_process() only, tcp_slowtmr() needs to do some things between "prepare" and "commit".

Parameters

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

tcp_rexmit_rto_commit()

void tcp_rexmit_rto_commit

(

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_rexmit_rto_prepare()

err_t tcp_rexmit_rto_prepare

(

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	(	const struct tcp_pcb *	pcb,
		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) to abort a connection.

Called by tcp_abort() (to abort a local connection), tcp_closen() (if not all data has been received by the application), tcp_timewait_input() (if a SYN is received) 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

pcb	TCP pcb (may be NULL if no pcb is available)
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_rst_netif()

void tcp_rst_netif	(	struct netif *	netif,
		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) to show that there is no matching local connection for a received segment.

Called by tcp_input() (if no matching local pcb was found) and tcp_listen_input() (if incoming segment has ACK flag set).

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

netif	the netif on which to send the RST (since we have no pcb)
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_seg_copy()

struct tcp_seg * tcp_seg_copy

(

struct tcp_seg *

seg

)

Returns a copy of the given TCP segment. The pbuf and data are not copied, only the pointers

Parameters

seg	the old tcp_seg

Returns

a copy of seg

tcp_seg_free()

void tcp_seg_free

(

struct tcp_seg *

seg

)

Frees a TCP segment (tcp_seg structure).

Parameters

seg	single tcp_seg to free

tcp_segs_free()

void tcp_segs_free

(

struct tcp_seg *

seg

)

Deallocates a list of TCP segments (tcp_seg structures).

Parameters

seg	tcp_seg list of TCP segments to free

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. This FIN may be added to an existing segment or a new, otherwise empty segment is enqueued.

Parameters

pcb	the tcp_pcb over which to send a segment

Returns

ERR_OK if sent, another err_t otherwise

tcp_slowtmr()

void tcp_slowtmr

(

void

)

Called every 500 ms and implements the retransmission timer and the timer that removes PCBs that have been in TIME-WAIT for enough time. It also increments various timers such as the inactivity timer in each PCB.

Automatically called from tcp_tmr().

tcp_split_unsent_seg()

err_t tcp_split_unsent_seg	(	struct tcp_pcb *	pcb,
		u16_t	split )

Split segment on the head of the unsent queue. If return is not ERR_OK, existing head remains intact

The split is accomplished by creating a new TCP segment and pbuf which holds the remainder payload after the split. The original pbuf is trimmed to new length. This allows splitting of read-only pbufs

Parameters

pcb	the tcp_pcb for which to split the unsent head
split	the amount of payload to remain in the head

tcp_timer_needed()

void tcp_timer_needed

(

void

)

External function (implemented in timers.c), called when TCP detects that a timer is needed (i.e. active- or time-wait-pcb found).

Called from TCP_REG when registering a new PCB: the reason is to have the TCP timer only running when there are active (or time-wait) PCBs.

tcp_tmr()

void tcp_tmr

(

void

)

Called periodically to dispatch TCP timers.

tcp_txnow()

void tcp_txnow

(

void

)

Call tcp_output for all active pcbs that have TF_NAGLEMEMERR set

tcp_update_rcv_ann_wnd()

u32_t tcp_update_rcv_ann_wnd

(

struct tcp_pcb *

pcb

)

Update the state that tracks the available window space to advertise.

Returns how much extra window would be advertised if we sent an update now.

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

Variable Documentation

tcp_active_pcbs

struct tcp_pcb* tcp_active_pcbs

extern

List of all TCP PCBs that are in a state in which they accept or send data.

tcp_bound_pcbs

struct tcp_pcb* tcp_bound_pcbs

extern

List of all TCP PCBs bound but not yet (connected || listening)

tcp_listen_pcbs

union tcp_listen_pcbs_t tcp_listen_pcbs

extern

List of all TCP PCBs in LISTEN state

tcp_pcb_lists

struct tcp_pcb** const tcp_pcb_lists[4]

extern

An array with all (non-temporary) PCB lists, mainly used for smaller code size

tcp_tw_pcbs

struct tcp_pcb* tcp_tw_pcbs

extern

List of all TCP PCBs in TIME-WAIT state