Transmission Control Protocol, incoming traffic.

The input processing functions of the TCP layer.

These functions are generally called in the order (ip_input() ->) tcp_input() -> * tcp_process() -> tcp_receive() (-> application).

#include "lwip/opt.h"
#include "lwip/tcp_impl.h"
#include "lwip/def.h"
#include "lwip/ip_addr.h"
#include "lwip/netif.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/inet_chksum.h"
#include "lwip/stats.h"
#include "lwip/snmp.h"
#include "arch/perf.h"

Functions
void	tcp_input (struct pbuf p, struct netif inp)
	The initial input processing of TCP. More...

static err_t	tcp_listen_input (struct tcp_pcb_listen *pcb)
	Called by tcp_input() when a segment arrives for a listening connection (from tcp_input()). More...

static void	tcp_oos_insert_segment (struct tcp_seg cseg, struct tcp_seg next)
	Insert segment into the list (segments covered with new one will be deleted) More...

static void	tcp_parseopt (struct tcp_pcb *pcb)
	Parses the options contained in the incoming segment. More...

static err_t	tcp_process (struct tcp_pcb *pcb)
	Implements the TCP state machine. More...

static void	tcp_receive (struct tcp_pcb *pcb)
	Called by tcp_process. More...

static err_t	tcp_timewait_input (struct tcp_pcb *pcb)
	Called by tcp_input() when a segment arrives for a connection in TIME_WAIT. More...

Variables
static u32_t	ackno

static u8_t	flags

static struct tcp_seg	inseg

static struct ip_hdr *	iphdr

static struct pbuf *	recv_data

static u8_t	recv_flags

static u32_t	seqno

struct tcp_pcb *	tcp_input_pcb

static struct tcp_hdr *	tcphdr

static u16_t	tcplen

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 IP header)
inp	network interface on which this segment was received

References tcp_pcb::acked, ackno, CLOSED, current_iphdr_dest, current_iphdr_src, ERR_ABRT, ERR_CLSD, ERR_OK, ERR_RST, tcp_pcb::errf, flags, pbuf::flags, tcp_pcb::flags, inet_chksum_pseudo(), inseg, ip_addr_cmp, ip_addr_isany, ip_addr_isbroadcast, ip_addr_ismulticast, ip_current_dest_addr, ip_current_src_addr, IP_PROTO_TCP, IPH_HL, tcp_seg::len, LISTEN, tcp_listen_pcbs_t::listen_pcbs, LWIP_ASSERT, LWIP_DEBUGF, memp_free(), tcp_seg::next, ntohl, ntohs, NULL, tcp_seg::p, pbuf::payload, PBUF_FLAG_PUSH, PBUF_FLAG_TCP_FIN, pbuf_free(), pbuf_header(), PERF_START, PERF_STOP, tcp_pcb::rcv_wnd, recv_data, recv_flags, tcp_pcb::refused_data, tcp_pcb::remote_port, seqno, snmp_inc_tcpinerrs, snmp_inc_tcpinsegs, tcp_abort(), tcp_active_pcbs, tcp_debug_print, tcp_debug_print_flags, tcp_debug_print_state, TCP_EVENT_CLOSED, TCP_EVENT_ERR, TCP_EVENT_RECV, TCP_EVENT_SENT, TCP_FIN, TCP_INPUT_DEBUG, tcp_listen_input(), tcp_listen_pcbs, tcp_output(), tcp_pcb_remove(), tcp_pcbs_sane, tcp_process(), tcp_process_refused_data(), TCP_PSH, TCP_RST, tcp_rst(), TCP_RST_DEBUG, TCP_STATS_INC, TCP_SYN, tcp_timewait_input(), tcp_tw_pcbs, TCP_WND, TCPH_FLAGS, TCPH_HDRLEN, tcphdr, tcp_seg::tcphdr, tcplen, TF_CLOSED, TF_GOT_FIN, TF_RESET, TF_RXCLOSED, TIME_WAIT, pbuf::tot_len, U16_F, and X16_F.

Referenced by ip_input().

static err_t tcp_listen_input ( struct tcp_pcb_listen * pcb )

static

Called by tcp_input() when a segment arrives for a listening connection (from tcp_input()).

Parameters

pcb	the tcp_pcb_listen for which a segment arrived

Returns: ERR_OK if the segment was processed another err_t on error

Note: the return value is not (yet?) used in tcp_input(); the segment which arrived is saved in global variables, therefore only the pcb involved is passed as a parameter to this function

References ackno, current_iphdr_dest, current_iphdr_src, ERR_ABRT, ERR_MEM, ERR_OK, flags, ip_addr_copy, ip_current_dest_addr, ip_current_src_addr, LWIP_DEBUGF, tcp_pcb::mss, NULL, tcp_pcb::rcv_ann_right_edge, tcp_pcb::rcv_nxt, tcp_pcb::remote_port, seqno, tcp_pcb::snd_wl1, tcp_pcb::snd_wnd, tcp_pcb::snd_wnd_max, snmp_inc_tcppassiveopens, SOF_INHERITED, tcp_pcb::ssthresh, SYN_RCVD, tcp_abandon(), TCP_ACK, tcp_alloc(), TCP_DEBUG, tcp_eff_send_mss(), tcp_enqueue_flags(), tcp_output(), tcp_parseopt(), TCP_REG_ACTIVE, TCP_RST, tcp_rst(), TCP_RST_DEBUG, TCP_STATS_INC, TCP_SYN, tcplen, and U16_F.

Referenced by tcp_input().

static void tcp_oos_insert_segment	(	struct tcp_seg *	cseg,
		struct tcp_seg *	next
	)

static

Insert segment into the list (segments covered with new one will be deleted)

Called from tcp_receive()

References tcp_seg::len, next, tcp_seg::next, NULL, tcp_seg::p, pbuf_realloc(), seqno, TCP_FIN, tcp_seg_free(), tcp_segs_free(), TCP_SEQ_GEQ, TCP_SEQ_GT, TCPH_FLAGS, TCPH_SET_FLAG, and tcp_seg::tcphdr.

Referenced by tcp_receive().

static void tcp_parseopt ( struct tcp_pcb * pcb )

static

Parses the options contained in the incoming segment.

Called from tcp_listen_input() and tcp_process(). Currently, only the MSS option is supported!

Parameters

pcb	the tcp_pcb for which a segment arrived

References flags, tcp_pcb::flags, LWIP_DEBUGF, tcp_pcb::mss, ntohl, seqno, TCP_HLEN, TCP_INPUT_DEBUG, TCP_MSS, TCP_SEQ_BETWEEN, TCP_SYN, TCPH_HDRLEN, tcplen, and TF_TIMESTAMP.

Referenced by tcp_listen_input(), and tcp_process().

static err_t tcp_process ( struct tcp_pcb * pcb )

static

Implements the TCP state machine.

Called by tcp_input. In some states tcp_receive() is called to receive data. The tcp_seg argument will be freed by the caller (tcp_input()) unless the recv_data pointer in the pcb is set.

Parameters

pcb	the tcp_pcb for which a segment arrived

Note: the segment which arrived is saved in global variables, therefore only the pcb involved is passed as a parameter to this function

References tcp_pcb::acked, ackno, CLOSE_WAIT, CLOSED, CLOSING, tcp_pcb::cwnd, ERR_ABRT, ERR_OK, ERR_RST, ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, flags, tcp_pcb::flags, inseg, ip_current_dest_addr, ip_current_src_addr, tcp_pcb::keep_cnt_sent, LAST_ACK, tcp_pcb::lastack, LWIP_ASSERT, LWIP_DEBUGF, tcp_pcb::mss, tcp_seg::next, tcp_pcb::nrtx, ntohl, NULL, tcp_pcb::rcv_ann_right_edge, tcp_pcb::rcv_nxt, tcp_pcb::rcv_wnd, recv_flags, tcp_pcb::rtime, seqno, tcp_pcb::snd_buf, tcp_pcb::snd_nxt, tcp_pcb::snd_queuelen, tcp_pcb::snd_wl1, tcp_pcb::snd_wnd, tcp_pcb::snd_wnd_max, tcp_pcb::ssthresh, SYN_RCVD, SYN_SENT, tcp_abort(), TCP_ACK, tcp_ack_now, TCP_DEBUG, tcp_eff_send_mss(), TCP_EVENT_ACCEPT, TCP_EVENT_CONNECTED, TCP_INPUT_DEBUG, tcp_parseopt(), tcp_pcb_purge(), TCP_QLEN_DEBUG, tcp_receive(), TCP_REG, tcp_rexmit(), TCP_RMV_ACTIVE, TCP_RST, tcp_rst(), tcp_seg_free(), TCP_SEQ_BETWEEN, TCP_SYN, tcp_ticks, tcp_tw_pcbs, tcp_seg::tcphdr, tcplen, TF_ACK_DELAY, TF_CLOSED, TF_GOT_FIN, TF_RESET, TF_RXCLOSED, TIME_WAIT, tcp_pcb::tmr, U16_F, U32_F, and tcp_pcb::unacked.

Referenced by tcp_input().

static void tcp_receive ( struct tcp_pcb * pcb )

static

Called by tcp_process.

Checks if the given segment is an ACK for outstanding data, and if so frees the memory of the buffered data. Next, is places the segment on any of the receive queues (pcb->recved or pcb->ooseq). If the segment is buffered, the pbuf is referenced by pbuf_ref so that it will not be freed until it has been removed from the buffer.

If the incoming segment constitutes an ACK for a segment that was used for RTT estimation, the RTT is estimated here as well.

Called from tcp_process().

References tcp_pcb::acked, ackno, CLOSE_WAIT, tcp_pcb::cwnd, tcp_pcb::dupacks, ESTABLISHED, flags, tcp_pcb::flags, inseg, tcp_pcb::lastack, pbuf::len, tcp_seg::len, LWIP_ASSERT, LWIP_DEBUGF, tcp_pcb::mss, pbuf::next, next, tcp_seg::next, tcp_pcb::nrtx, ntohl, NULL, tcp_pcb::ooseq, tcp_seg::p, pbuf_cat(), pbuf_clen(), pbuf_header(), pbuf_realloc(), tcp_pcb::persist_backoff, tcp_pcb::persist_cnt, tcp_pcb::polltmr, tcp_pcb::rcv_nxt, tcp_pcb::rcv_wnd, recv_flags, tcp_pcb::rtime, tcp_pcb::rto, tcp_pcb::rtseq, tcp_pcb::rttest, tcp_pcb::sa, seqno, tcp_pcb::snd_buf, tcp_pcb::snd_nxt, tcp_pcb::snd_queuelen, tcp_pcb::snd_wl1, tcp_pcb::snd_wl2, tcp_pcb::snd_wnd, tcp_pcb::snd_wnd_max, tcp_pcb::ssthresh, tcp_pcb::sv, TCP_ACK, tcp_ack, tcp_ack_now, TCP_CWND_DEBUG, TCP_FIN, TCP_INPUT_DEBUG, tcp_oos_insert_segment(), TCP_QLEN_DEBUG, tcp_rexmit_fast(), TCP_RTO_DEBUG, tcp_seg_copy(), tcp_seg_free(), tcp_segs_free(), tcp_send_empty_ack(), TCP_SEQ_BETWEEN, TCP_SEQ_GEQ, TCP_SEQ_GT, TCP_SEQ_LEQ, TCP_SEQ_LT, TCP_SLOW_INTERVAL, TCP_SYN, TCP_TCPLEN, tcp_ticks, tcp_update_rcv_ann_wnd(), TCP_WND_DEBUG, TCPH_FLAGS, TCPH_FLAGS_SET, TCPH_SET_FLAG, tcp_seg::tcphdr, tcplen, TF_GOT_FIN, TF_INFR, pbuf::tot_len, U16_F, U32_F, tcp_pcb::unacked, tcp_pcb::unsent, and tcp_pcb::unsent_oversize.