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Diff: core/tcp_in.c
- Revision:
- 0:51ac1d130fd4
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/core/tcp_in.c Fri Jun 22 09:25:39 2012 +0000
@@ -0,0 +1,1567 @@
+/**
+ * @file
+ * 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).
+ *
+ */
+
+/*
+ * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+ * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+ * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ *
+ * This file is part of the lwIP TCP/IP stack.
+ *
+ * Author: Adam Dunkels <adam@sics.se>
+ *
+ */
+
+#include "lwip/opt.h"
+
+#if LWIP_TCP /* don't build if not configured for use in lwipopts.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"
+
+/* These variables are global to all functions involved in the input
+ processing of TCP segments. They are set by the tcp_input()
+ function. */
+static struct tcp_seg inseg;
+static struct tcp_hdr *tcphdr;
+static struct ip_hdr *iphdr;
+static u32_t seqno, ackno;
+static u8_t flags;
+static u16_t tcplen;
+
+static u8_t recv_flags;
+static struct pbuf *recv_data;
+
+struct tcp_pcb *tcp_input_pcb;
+
+/* Forward declarations. */
+static err_t tcp_process(struct tcp_pcb *pcb);
+static void tcp_receive(struct tcp_pcb *pcb);
+static void tcp_parseopt(struct tcp_pcb *pcb);
+
+static err_t tcp_listen_input(struct tcp_pcb_listen *pcb);
+static err_t tcp_timewait_input(struct tcp_pcb *pcb);
+
+/**
+ * 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()).
+ *
+ * @param p received TCP segment to process (p->payload pointing to the IP header)
+ * @param inp network interface on which this segment was received
+ */
+void
+tcp_input(struct pbuf *p, struct netif *inp)
+{
+ struct tcp_pcb *pcb, *prev;
+ struct tcp_pcb_listen *lpcb;
+#if SO_REUSE
+ struct tcp_pcb *lpcb_prev = NULL;
+ struct tcp_pcb_listen *lpcb_any = NULL;
+#endif /* SO_REUSE */
+ u8_t hdrlen;
+ err_t err;
+
+ PERF_START;
+
+ TCP_STATS_INC(tcp.recv);
+ snmp_inc_tcpinsegs();
+
+ iphdr = (struct ip_hdr *)p->payload;
+ tcphdr = (struct tcp_hdr *)((u8_t *)p->payload + IPH_HL(iphdr) * 4);
+
+#if TCP_INPUT_DEBUG
+ tcp_debug_print(tcphdr);
+#endif
+
+ /* remove header from payload */
+ if (pbuf_header(p, -((s16_t)(IPH_HL(iphdr) * 4))) || (p->tot_len < sizeof(struct tcp_hdr))) {
+ /* drop short packets */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: short packet (%"U16_F" bytes) discarded\n", p->tot_len));
+ TCP_STATS_INC(tcp.lenerr);
+ TCP_STATS_INC(tcp.drop);
+ snmp_inc_tcpinerrs();
+ pbuf_free(p);
+ return;
+ }
+
+ /* Don't even process incoming broadcasts/multicasts. */
+ if (ip_addr_isbroadcast(¤t_iphdr_dest, inp) ||
+ ip_addr_ismulticast(¤t_iphdr_dest)) {
+ TCP_STATS_INC(tcp.proterr);
+ TCP_STATS_INC(tcp.drop);
+ snmp_inc_tcpinerrs();
+ pbuf_free(p);
+ return;
+ }
+
+#if CHECKSUM_CHECK_TCP
+ /* Verify TCP checksum. */
+ if (inet_chksum_pseudo(p, ip_current_src_addr(), ip_current_dest_addr(),
+ IP_PROTO_TCP, p->tot_len) != 0) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: packet discarded due to failing checksum 0x%04"X16_F"\n",
+ inet_chksum_pseudo(p, ip_current_src_addr(), ip_current_dest_addr(),
+ IP_PROTO_TCP, p->tot_len)));
+#if TCP_DEBUG
+ tcp_debug_print(tcphdr);
+#endif /* TCP_DEBUG */
+ TCP_STATS_INC(tcp.chkerr);
+ TCP_STATS_INC(tcp.drop);
+ snmp_inc_tcpinerrs();
+ pbuf_free(p);
+ return;
+ }
+#endif
+
+ /* Move the payload pointer in the pbuf so that it points to the
+ TCP data instead of the TCP header. */
+ hdrlen = TCPH_HDRLEN(tcphdr);
+ if(pbuf_header(p, -(hdrlen * 4))){
+ /* drop short packets */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: short packet\n"));
+ TCP_STATS_INC(tcp.lenerr);
+ TCP_STATS_INC(tcp.drop);
+ snmp_inc_tcpinerrs();
+ pbuf_free(p);
+ return;
+ }
+
+ /* Convert fields in TCP header to host byte order. */
+ tcphdr->src = ntohs(tcphdr->src);
+ tcphdr->dest = ntohs(tcphdr->dest);
+ seqno = tcphdr->seqno = ntohl(tcphdr->seqno);
+ ackno = tcphdr->ackno = ntohl(tcphdr->ackno);
+ tcphdr->wnd = ntohs(tcphdr->wnd);
+
+ flags = TCPH_FLAGS(tcphdr);
+ tcplen = p->tot_len + ((flags & (TCP_FIN | TCP_SYN)) ? 1 : 0);
+
+ /* Demultiplex an incoming segment. First, we check if it is destined
+ for an active connection. */
+ prev = NULL;
+
+
+ for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
+ LWIP_ASSERT("tcp_input: active pcb->state != CLOSED", pcb->state != CLOSED);
+ LWIP_ASSERT("tcp_input: active pcb->state != TIME-WAIT", pcb->state != TIME_WAIT);
+ LWIP_ASSERT("tcp_input: active pcb->state != LISTEN", pcb->state != LISTEN);
+ if (pcb->remote_port == tcphdr->src &&
+ pcb->local_port == tcphdr->dest &&
+ ip_addr_cmp(&(pcb->remote_ip), ¤t_iphdr_src) &&
+ ip_addr_cmp(&(pcb->local_ip), ¤t_iphdr_dest)) {
+
+ /* Move this PCB to the front of the list so that subsequent
+ lookups will be faster (we exploit locality in TCP segment
+ arrivals). */
+ LWIP_ASSERT("tcp_input: pcb->next != pcb (before cache)", pcb->next != pcb);
+ if (prev != NULL) {
+ prev->next = pcb->next;
+ pcb->next = tcp_active_pcbs;
+ tcp_active_pcbs = pcb;
+ }
+ LWIP_ASSERT("tcp_input: pcb->next != pcb (after cache)", pcb->next != pcb);
+ break;
+ }
+ prev = pcb;
+ }
+
+ if (pcb == NULL) {
+ /* If it did not go to an active connection, we check the connections
+ in the TIME-WAIT state. */
+ for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
+ LWIP_ASSERT("tcp_input: TIME-WAIT pcb->state == TIME-WAIT", pcb->state == TIME_WAIT);
+ if (pcb->remote_port == tcphdr->src &&
+ pcb->local_port == tcphdr->dest &&
+ ip_addr_cmp(&(pcb->remote_ip), ¤t_iphdr_src) &&
+ ip_addr_cmp(&(pcb->local_ip), ¤t_iphdr_dest)) {
+ /* We don't really care enough to move this PCB to the front
+ of the list since we are not very likely to receive that
+ many segments for connections in TIME-WAIT. */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: packed for TIME_WAITing connection.\n"));
+ tcp_timewait_input(pcb);
+ pbuf_free(p);
+ return;
+ }
+ }
+
+ /* Finally, if we still did not get a match, we check all PCBs that
+ are LISTENing for incoming connections. */
+ prev = NULL;
+ for(lpcb = tcp_listen_pcbs.listen_pcbs; lpcb != NULL; lpcb = lpcb->next) {
+ if (lpcb->local_port == tcphdr->dest) {
+#if SO_REUSE
+ if (ip_addr_cmp(&(lpcb->local_ip), ¤t_iphdr_dest)) {
+ /* found an exact match */
+ break;
+ } else if(ip_addr_isany(&(lpcb->local_ip))) {
+ /* found an ANY-match */
+ lpcb_any = lpcb;
+ lpcb_prev = prev;
+ }
+#else /* SO_REUSE */
+ if (ip_addr_cmp(&(lpcb->local_ip), ¤t_iphdr_dest) ||
+ ip_addr_isany(&(lpcb->local_ip))) {
+ /* found a match */
+ break;
+ }
+#endif /* SO_REUSE */
+ }
+ prev = (struct tcp_pcb *)lpcb;
+ }
+#if SO_REUSE
+ /* first try specific local IP */
+ if (lpcb == NULL) {
+ /* only pass to ANY if no specific local IP has been found */
+ lpcb = lpcb_any;
+ prev = lpcb_prev;
+ }
+#endif /* SO_REUSE */
+ if (lpcb != NULL) {
+ /* Move this PCB to the front of the list so that subsequent
+ lookups will be faster (we exploit locality in TCP segment
+ arrivals). */
+ if (prev != NULL) {
+ ((struct tcp_pcb_listen *)prev)->next = lpcb->next;
+ /* our successor is the remainder of the listening list */
+ lpcb->next = tcp_listen_pcbs.listen_pcbs;
+ /* put this listening pcb at the head of the listening list */
+ tcp_listen_pcbs.listen_pcbs = lpcb;
+ }
+
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: packed for LISTENing connection.\n"));
+ tcp_listen_input(lpcb);
+ pbuf_free(p);
+ return;
+ }
+ }
+
+#if TCP_INPUT_DEBUG
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("+-+-+-+-+-+-+-+-+-+-+-+-+-+- tcp_input: flags "));
+ tcp_debug_print_flags(TCPH_FLAGS(tcphdr));
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("-+-+-+-+-+-+-+-+-+-+-+-+-+-+\n"));
+#endif /* TCP_INPUT_DEBUG */
+
+
+ if (pcb != NULL) {
+ /* The incoming segment belongs to a connection. */
+#if TCP_INPUT_DEBUG
+#if TCP_DEBUG
+ tcp_debug_print_state(pcb->state);
+#endif /* TCP_DEBUG */
+#endif /* TCP_INPUT_DEBUG */
+
+ /* Set up a tcp_seg structure. */
+ inseg.next = NULL;
+ inseg.len = p->tot_len;
+ inseg.p = p;
+ inseg.tcphdr = tcphdr;
+
+ recv_data = NULL;
+ recv_flags = 0;
+
+ /* If there is data which was previously "refused" by upper layer */
+ if (pcb->refused_data != NULL) {
+ /* Notify again application with data previously received. */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: notify kept packet\n"));
+ TCP_EVENT_RECV(pcb, pcb->refused_data, ERR_OK, err);
+ if (err == ERR_OK) {
+ pcb->refused_data = NULL;
+ } else if ((err == ERR_ABRT) || (tcplen > 0)) {
+ /* if err == ERR_ABRT, 'pcb' is already deallocated */
+ /* Drop incoming packets because pcb is "full" (only if the incoming
+ segment contains data). */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: drop incoming packets, because pcb is \"full\"\n"));
+ TCP_STATS_INC(tcp.drop);
+ snmp_inc_tcpinerrs();
+ pbuf_free(p);
+ return;
+ }
+ }
+ tcp_input_pcb = pcb;
+ err = tcp_process(pcb);
+ /* A return value of ERR_ABRT means that tcp_abort() was called
+ and that the pcb has been freed. If so, we don't do anything. */
+ if (err != ERR_ABRT) {
+ if (recv_flags & TF_RESET) {
+ /* TF_RESET means that the connection was reset by the other
+ end. We then call the error callback to inform the
+ application that the connection is dead before we
+ deallocate the PCB. */
+ TCP_EVENT_ERR(pcb->errf, pcb->callback_arg, ERR_RST);
+ tcp_pcb_remove(&tcp_active_pcbs, pcb);
+ memp_free(MEMP_TCP_PCB, pcb);
+ } else if (recv_flags & TF_CLOSED) {
+ /* The connection has been closed and we will deallocate the
+ PCB. */
+ tcp_pcb_remove(&tcp_active_pcbs, pcb);
+ memp_free(MEMP_TCP_PCB, pcb);
+ } else {
+ err = ERR_OK;
+ /* If the application has registered a "sent" function to be
+ called when new send buffer space is available, we call it
+ now. */
+ if (pcb->acked > 0) {
+ TCP_EVENT_SENT(pcb, pcb->acked, err);
+ if (err == ERR_ABRT) {
+ goto aborted;
+ }
+ }
+
+ if (recv_data != NULL) {
+ LWIP_ASSERT("pcb->refused_data == NULL", pcb->refused_data == NULL);
+ if (pcb->flags & TF_RXCLOSED) {
+ /* received data although already closed -> abort (send RST) to
+ notify the remote host that not all data has been processed */
+ pbuf_free(recv_data);
+ tcp_abort(pcb);
+ goto aborted;
+ }
+ if (flags & TCP_PSH) {
+ recv_data->flags |= PBUF_FLAG_PUSH;
+ }
+
+ /* Notify application that data has been received. */
+ TCP_EVENT_RECV(pcb, recv_data, ERR_OK, err);
+ if (err == ERR_ABRT) {
+ goto aborted;
+ }
+
+ /* If the upper layer can't receive this data, store it */
+ if (err != ERR_OK) {
+ pcb->refused_data = recv_data;
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: keep incoming packet, because pcb is \"full\"\n"));
+ }
+ }
+
+ /* If a FIN segment was received, we call the callback
+ function with a NULL buffer to indicate EOF. */
+ if (recv_flags & TF_GOT_FIN) {
+ /* correct rcv_wnd as the application won't call tcp_recved()
+ for the FIN's seqno */
+ if (pcb->rcv_wnd != TCP_WND) {
+ pcb->rcv_wnd++;
+ }
+ TCP_EVENT_CLOSED(pcb, err);
+ if (err == ERR_ABRT) {
+ goto aborted;
+ }
+ }
+
+ tcp_input_pcb = NULL;
+ /* Try to send something out. */
+ tcp_output(pcb);
+#if TCP_INPUT_DEBUG
+#if TCP_DEBUG
+ tcp_debug_print_state(pcb->state);
+#endif /* TCP_DEBUG */
+#endif /* TCP_INPUT_DEBUG */
+ }
+ }
+ /* Jump target if pcb has been aborted in a callback (by calling tcp_abort()).
+ Below this line, 'pcb' may not be dereferenced! */
+aborted:
+ tcp_input_pcb = NULL;
+ recv_data = NULL;
+
+ /* give up our reference to inseg.p */
+ if (inseg.p != NULL)
+ {
+ pbuf_free(inseg.p);
+ inseg.p = NULL;
+ }
+ } else {
+
+ /* If no matching PCB was found, send a TCP RST (reset) to the
+ sender. */
+ LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_input: no PCB match found, resetting.\n"));
+ if (!(TCPH_FLAGS(tcphdr) & TCP_RST)) {
+ TCP_STATS_INC(tcp.proterr);
+ TCP_STATS_INC(tcp.drop);
+ tcp_rst(ackno, seqno + tcplen,
+ ip_current_dest_addr(), ip_current_src_addr(),
+ tcphdr->dest, tcphdr->src);
+ }
+ pbuf_free(p);
+ }
+
+ LWIP_ASSERT("tcp_input: tcp_pcbs_sane()", tcp_pcbs_sane());
+ PERF_STOP("tcp_input");
+}
+
+/**
+ * Called by tcp_input() when a segment arrives for a listening
+ * connection (from tcp_input()).
+ *
+ * @param pcb the tcp_pcb_listen for which a segment arrived
+ * @return ERR_OK if the segment was processed
+ * another err_t on error
+ *
+ * @note the return value is not (yet?) used in tcp_input()
+ * @note the segment which arrived is saved in global variables, therefore only the pcb
+ * involved is passed as a parameter to this function
+ */
+static err_t
+tcp_listen_input(struct tcp_pcb_listen *pcb)
+{
+ struct tcp_pcb *npcb;
+ err_t rc;
+
+ /* In the LISTEN state, we check for incoming SYN segments,
+ creates a new PCB, and responds with a SYN|ACK. */
+ if (flags & TCP_ACK) {
+ /* For incoming segments with the ACK flag set, respond with a
+ RST. */
+ LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_listen_input: ACK in LISTEN, sending reset\n"));
+ tcp_rst(ackno + 1, seqno + tcplen,
+ ip_current_dest_addr(), ip_current_src_addr(),
+ tcphdr->dest, tcphdr->src);
+ } else if (flags & TCP_SYN) {
+ LWIP_DEBUGF(TCP_DEBUG, ("TCP connection request %"U16_F" -> %"U16_F".\n", tcphdr->src, tcphdr->dest));
+#if TCP_LISTEN_BACKLOG
+ if (pcb->accepts_pending >= pcb->backlog) {
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_listen_input: listen backlog exceeded for port %"U16_F"\n", tcphdr->dest));
+ return ERR_ABRT;
+ }
+#endif /* TCP_LISTEN_BACKLOG */
+ npcb = tcp_alloc(pcb->prio);
+ /* If a new PCB could not be created (probably due to lack of memory),
+ we don't do anything, but rely on the sender will retransmit the
+ SYN at a time when we have more memory available. */
+ if (npcb == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_listen_input: could not allocate PCB\n"));
+ TCP_STATS_INC(tcp.memerr);
+ return ERR_MEM;
+ }
+#if TCP_LISTEN_BACKLOG
+ pcb->accepts_pending++;
+#endif /* TCP_LISTEN_BACKLOG */
+ /* Set up the new PCB. */
+ ip_addr_copy(npcb->local_ip, current_iphdr_dest);
+ npcb->local_port = pcb->local_port;
+ ip_addr_copy(npcb->remote_ip, current_iphdr_src);
+ npcb->remote_port = tcphdr->src;
+ npcb->state = SYN_RCVD;
+ npcb->rcv_nxt = seqno + 1;
+ npcb->rcv_ann_right_edge = npcb->rcv_nxt;
+ npcb->snd_wnd = tcphdr->wnd;
+ npcb->ssthresh = npcb->snd_wnd;
+ npcb->snd_wl1 = seqno - 1;/* initialise to seqno-1 to force window update */
+ npcb->callback_arg = pcb->callback_arg;
+#if LWIP_CALLBACK_API
+ npcb->accept = pcb->accept;
+#endif /* LWIP_CALLBACK_API */
+ /* inherit socket options */
+ npcb->so_options = pcb->so_options & SOF_INHERITED;
+ /* Register the new PCB so that we can begin receiving segments
+ for it. */
+ TCP_REG(&tcp_active_pcbs, npcb);
+
+ /* Parse any options in the SYN. */
+ tcp_parseopt(npcb);
+#if TCP_CALCULATE_EFF_SEND_MSS
+ npcb->mss = tcp_eff_send_mss(npcb->mss, &(npcb->remote_ip));
+#endif /* TCP_CALCULATE_EFF_SEND_MSS */
+
+ snmp_inc_tcppassiveopens();
+
+ /* Send a SYN|ACK together with the MSS option. */
+ rc = tcp_enqueue_flags(npcb, TCP_SYN | TCP_ACK);
+ if (rc != ERR_OK) {
+ tcp_abandon(npcb, 0);
+ return rc;
+ }
+ return tcp_output(npcb);
+ }
+ return ERR_OK;
+}
+
+/**
+ * Called by tcp_input() when a segment arrives for a connection in
+ * TIME_WAIT.
+ *
+ * @param 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
+ */
+static err_t
+tcp_timewait_input(struct tcp_pcb *pcb)
+{
+ /* RFC 1337: in TIME_WAIT, ignore RST and ACK FINs + any 'acceptable' segments */
+ /* RFC 793 3.9 Event Processing - Segment Arrives:
+ * - first check sequence number - we skip that one in TIME_WAIT (always
+ * acceptable since we only send ACKs)
+ * - second check the RST bit (... return) */
+ if (flags & TCP_RST) {
+ return ERR_OK;
+ }
+ /* - fourth, check the SYN bit, */
+ if (flags & TCP_SYN) {
+ /* If an incoming segment is not acceptable, an acknowledgment
+ should be sent in reply */
+ if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt+pcb->rcv_wnd)) {
+ /* If the SYN is in the window it is an error, send a reset */
+ tcp_rst(ackno, seqno + tcplen, ip_current_dest_addr(), ip_current_src_addr(),
+ tcphdr->dest, tcphdr->src);
+ return ERR_OK;
+ }
+ } else if (flags & TCP_FIN) {
+ /* - eighth, check the FIN bit: Remain in the TIME-WAIT state.
+ Restart the 2 MSL time-wait timeout.*/
+ pcb->tmr = tcp_ticks;
+ }
+
+ if ((tcplen > 0)) {
+ /* Acknowledge data, FIN or out-of-window SYN */
+ pcb->flags |= TF_ACK_NOW;
+ return tcp_output(pcb);
+ }
+ return ERR_OK;
+}
+
+/**
+ * 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.
+ *
+ * @param 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
+ */
+static err_t
+tcp_process(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *rseg;
+ u8_t acceptable = 0;
+ err_t err;
+
+ err = ERR_OK;
+
+ /* Process incoming RST segments. */
+ if (flags & TCP_RST) {
+ /* First, determine if the reset is acceptable. */
+ if (pcb->state == SYN_SENT) {
+ if (ackno == pcb->snd_nxt) {
+ acceptable = 1;
+ }
+ } else {
+ if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt,
+ pcb->rcv_nxt+pcb->rcv_wnd)) {
+ acceptable = 1;
+ }
+ }
+
+ if (acceptable) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_process: Connection RESET\n"));
+ LWIP_ASSERT("tcp_input: pcb->state != CLOSED", pcb->state != CLOSED);
+ recv_flags |= TF_RESET;
+ pcb->flags &= ~TF_ACK_DELAY;
+ return ERR_RST;
+ } else {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_process: unacceptable reset seqno %"U32_F" rcv_nxt %"U32_F"\n",
+ seqno, pcb->rcv_nxt));
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_process: unacceptable reset seqno %"U32_F" rcv_nxt %"U32_F"\n",
+ seqno, pcb->rcv_nxt));
+ return ERR_OK;
+ }
+ }
+
+ if ((flags & TCP_SYN) && (pcb->state != SYN_SENT && pcb->state != SYN_RCVD)) {
+ /* Cope with new connection attempt after remote end crashed */
+ tcp_ack_now(pcb);
+ return ERR_OK;
+ }
+
+ if ((pcb->flags & TF_RXCLOSED) == 0) {
+ /* Update the PCB (in)activity timer unless rx is closed (see tcp_shutdown) */
+ pcb->tmr = tcp_ticks;
+ }
+ pcb->keep_cnt_sent = 0;
+
+ tcp_parseopt(pcb);
+
+ /* Do different things depending on the TCP state. */
+ switch (pcb->state) {
+ case SYN_SENT:
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("SYN-SENT: ackno %"U32_F" pcb->snd_nxt %"U32_F" unacked %"U32_F"\n", ackno,
+ pcb->snd_nxt, ntohl(pcb->unacked->tcphdr->seqno)));
+ /* received SYN ACK with expected sequence number? */
+ if ((flags & TCP_ACK) && (flags & TCP_SYN)
+ && ackno == ntohl(pcb->unacked->tcphdr->seqno) + 1) {
+ pcb->snd_buf++;
+ pcb->rcv_nxt = seqno + 1;
+ pcb->rcv_ann_right_edge = pcb->rcv_nxt;
+ pcb->lastack = ackno;
+ pcb->snd_wnd = tcphdr->wnd;
+ pcb->snd_wl1 = seqno - 1; /* initialise to seqno - 1 to force window update */
+ pcb->state = ESTABLISHED;
+
+#if TCP_CALCULATE_EFF_SEND_MSS
+ pcb->mss = tcp_eff_send_mss(pcb->mss, &(pcb->remote_ip));
+#endif /* TCP_CALCULATE_EFF_SEND_MSS */
+
+ /* Set ssthresh again after changing pcb->mss (already set in tcp_connect
+ * but for the default value of pcb->mss) */
+ pcb->ssthresh = pcb->mss * 10;
+
+ pcb->cwnd = ((pcb->cwnd == 1) ? (pcb->mss * 2) : pcb->mss);
+ LWIP_ASSERT("pcb->snd_queuelen > 0", (pcb->snd_queuelen > 0));
+ --pcb->snd_queuelen;
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_process: SYN-SENT --queuelen %"U16_F"\n", (u16_t)pcb->snd_queuelen));
+ rseg = pcb->unacked;
+ pcb->unacked = rseg->next;
+
+ /* If there's nothing left to acknowledge, stop the retransmit
+ timer, otherwise reset it to start again */
+ if(pcb->unacked == NULL)
+ pcb->rtime = -1;
+ else {
+ pcb->rtime = 0;
+ pcb->nrtx = 0;
+ }
+
+ tcp_seg_free(rseg);
+
+ /* Call the user specified function to call when sucessfully
+ * connected. */
+ TCP_EVENT_CONNECTED(pcb, ERR_OK, err);
+ if (err == ERR_ABRT) {
+ return ERR_ABRT;
+ }
+ tcp_ack_now(pcb);
+ }
+ /* received ACK? possibly a half-open connection */
+ else if (flags & TCP_ACK) {
+ /* send a RST to bring the other side in a non-synchronized state. */
+ tcp_rst(ackno, seqno + tcplen, ip_current_dest_addr(), ip_current_src_addr(),
+ tcphdr->dest, tcphdr->src);
+ }
+ break;
+ case SYN_RCVD:
+ if (flags & TCP_ACK) {
+ /* expected ACK number? */
+ if (TCP_SEQ_BETWEEN(ackno, pcb->lastack+1, pcb->snd_nxt)) {
+ u16_t old_cwnd;
+ pcb->state = ESTABLISHED;
+ LWIP_DEBUGF(TCP_DEBUG, ("TCP connection established %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
+#if LWIP_CALLBACK_API
+ LWIP_ASSERT("pcb->accept != NULL", pcb->accept != NULL);
+#endif
+ /* Call the accept function. */
+ TCP_EVENT_ACCEPT(pcb, ERR_OK, err);
+ if (err != ERR_OK) {
+ /* If the accept function returns with an error, we abort
+ * the connection. */
+ /* Already aborted? */
+ if (err != ERR_ABRT) {
+ tcp_abort(pcb);
+ }
+ return ERR_ABRT;
+ }
+ old_cwnd = pcb->cwnd;
+ /* If there was any data contained within this ACK,
+ * we'd better pass it on to the application as well. */
+ tcp_receive(pcb);
+
+ /* Prevent ACK for SYN to generate a sent event */
+ if (pcb->acked != 0) {
+ pcb->acked--;
+ }
+
+ pcb->cwnd = ((old_cwnd == 1) ? (pcb->mss * 2) : pcb->mss);
+
+ if (recv_flags & TF_GOT_FIN) {
+ tcp_ack_now(pcb);
+ pcb->state = CLOSE_WAIT;
+ }
+ } else {
+ /* incorrect ACK number, send RST */
+ tcp_rst(ackno, seqno + tcplen, ip_current_dest_addr(), ip_current_src_addr(),
+ tcphdr->dest, tcphdr->src);
+ }
+ } else if ((flags & TCP_SYN) && (seqno == pcb->rcv_nxt - 1)) {
+ /* Looks like another copy of the SYN - retransmit our SYN-ACK */
+ tcp_rexmit(pcb);
+ }
+ break;
+ case CLOSE_WAIT:
+ /* FALLTHROUGH */
+ case ESTABLISHED:
+ tcp_receive(pcb);
+ if (recv_flags & TF_GOT_FIN) { /* passive close */
+ tcp_ack_now(pcb);
+ pcb->state = CLOSE_WAIT;
+ }
+ break;
+ case FIN_WAIT_1:
+ tcp_receive(pcb);
+ if (recv_flags & TF_GOT_FIN) {
+ if ((flags & TCP_ACK) && (ackno == pcb->snd_nxt)) {
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("TCP connection closed: FIN_WAIT_1 %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
+ tcp_ack_now(pcb);
+ tcp_pcb_purge(pcb);
+ TCP_RMV(&tcp_active_pcbs, pcb);
+ pcb->state = TIME_WAIT;
+ TCP_REG(&tcp_tw_pcbs, pcb);
+ } else {
+ tcp_ack_now(pcb);
+ pcb->state = CLOSING;
+ }
+ } else if ((flags & TCP_ACK) && (ackno == pcb->snd_nxt)) {
+ pcb->state = FIN_WAIT_2;
+ }
+ break;
+ case FIN_WAIT_2:
+ tcp_receive(pcb);
+ if (recv_flags & TF_GOT_FIN) {
+ LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed: FIN_WAIT_2 %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
+ tcp_ack_now(pcb);
+ tcp_pcb_purge(pcb);
+ TCP_RMV(&tcp_active_pcbs, pcb);
+ pcb->state = TIME_WAIT;
+ TCP_REG(&tcp_tw_pcbs, pcb);
+ }
+ break;
+ case CLOSING:
+ tcp_receive(pcb);
+ if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
+ LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed: CLOSING %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
+ tcp_pcb_purge(pcb);
+ TCP_RMV(&tcp_active_pcbs, pcb);
+ pcb->state = TIME_WAIT;
+ TCP_REG(&tcp_tw_pcbs, pcb);
+ }
+ break;
+ case LAST_ACK:
+ tcp_receive(pcb);
+ if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
+ LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed: LAST_ACK %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
+ /* bugfix #21699: don't set pcb->state to CLOSED here or we risk leaking segments */
+ recv_flags |= TF_CLOSED;
+ }
+ break;
+ default:
+ break;
+ }
+ return ERR_OK;
+}
+
+#if TCP_QUEUE_OOSEQ
+/**
+ * Insert segment into the list (segments covered with new one will be deleted)
+ *
+ * Called from tcp_receive()
+ */
+static void
+tcp_oos_insert_segment(struct tcp_seg *cseg, struct tcp_seg *next)
+{
+ struct tcp_seg *old_seg;
+
+ if (TCPH_FLAGS(cseg->tcphdr) & TCP_FIN) {
+ /* received segment overlaps all following segments */
+ tcp_segs_free(next);
+ next = NULL;
+ }
+ else {
+ /* delete some following segments
+ oos queue may have segments with FIN flag */
+ while (next &&
+ TCP_SEQ_GEQ((seqno + cseg->len),
+ (next->tcphdr->seqno + next->len))) {
+ /* cseg with FIN already processed */
+ if (TCPH_FLAGS(next->tcphdr) & TCP_FIN) {
+ TCPH_SET_FLAG(cseg->tcphdr, TCP_FIN);
+ }
+ old_seg = next;
+ next = next->next;
+ tcp_seg_free(old_seg);
+ }
+ if (next &&
+ TCP_SEQ_GT(seqno + cseg->len, next->tcphdr->seqno)) {
+ /* We need to trim the incoming segment. */
+ cseg->len = (u16_t)(next->tcphdr->seqno - seqno);
+ pbuf_realloc(cseg->p, cseg->len);
+ }
+ }
+ cseg->next = next;
+}
+#endif /* TCP_QUEUE_OOSEQ */
+
+/**
+ * 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
+ * i 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().
+ */
+static void
+tcp_receive(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *next;
+#if TCP_QUEUE_OOSEQ
+ struct tcp_seg *prev, *cseg;
+#endif /* TCP_QUEUE_OOSEQ */
+ struct pbuf *p;
+ s32_t off;
+ s16_t m;
+ u32_t right_wnd_edge;
+ u16_t new_tot_len;
+ int found_dupack = 0;
+
+ if (flags & TCP_ACK) {
+ right_wnd_edge = pcb->snd_wnd + pcb->snd_wl2;
+
+ /* Update window. */
+ if (TCP_SEQ_LT(pcb->snd_wl1, seqno) ||
+ (pcb->snd_wl1 == seqno && TCP_SEQ_LT(pcb->snd_wl2, ackno)) ||
+ (pcb->snd_wl2 == ackno && tcphdr->wnd > pcb->snd_wnd)) {
+ pcb->snd_wnd = tcphdr->wnd;
+ pcb->snd_wl1 = seqno;
+ pcb->snd_wl2 = ackno;
+ if (pcb->snd_wnd > 0 && pcb->persist_backoff > 0) {
+ pcb->persist_backoff = 0;
+ }
+ LWIP_DEBUGF(TCP_WND_DEBUG, ("tcp_receive: window update %"U16_F"\n", pcb->snd_wnd));
+#if TCP_WND_DEBUG
+ } else {
+ if (pcb->snd_wnd != tcphdr->wnd) {
+ LWIP_DEBUGF(TCP_WND_DEBUG,
+ ("tcp_receive: no window update lastack %"U32_F" ackno %"
+ U32_F" wl1 %"U32_F" seqno %"U32_F" wl2 %"U32_F"\n",
+ pcb->lastack, ackno, pcb->snd_wl1, seqno, pcb->snd_wl2));
+ }
+#endif /* TCP_WND_DEBUG */
+ }
+
+ /* (From Stevens TCP/IP Illustrated Vol II, p970.) Its only a
+ * duplicate ack if:
+ * 1) It doesn't ACK new data
+ * 2) length of received packet is zero (i.e. no payload)
+ * 3) the advertised window hasn't changed
+ * 4) There is outstanding unacknowledged data (retransmission timer running)
+ * 5) The ACK is == biggest ACK sequence number so far seen (snd_una)
+ *
+ * If it passes all five, should process as a dupack:
+ * a) dupacks < 3: do nothing
+ * b) dupacks == 3: fast retransmit
+ * c) dupacks > 3: increase cwnd
+ *
+ * If it only passes 1-3, should reset dupack counter (and add to
+ * stats, which we don't do in lwIP)
+ *
+ * If it only passes 1, should reset dupack counter
+ *
+ */
+
+ /* Clause 1 */
+ if (TCP_SEQ_LEQ(ackno, pcb->lastack)) {
+ pcb->acked = 0;
+ /* Clause 2 */
+ if (tcplen == 0) {
+ /* Clause 3 */
+ if (pcb->snd_wl2 + pcb->snd_wnd == right_wnd_edge){
+ /* Clause 4 */
+ if (pcb->rtime >= 0) {
+ /* Clause 5 */
+ if (pcb->lastack == ackno) {
+ found_dupack = 1;
+ if (pcb->dupacks + 1 > pcb->dupacks)
+ ++pcb->dupacks;
+ if (pcb->dupacks > 3) {
+ /* Inflate the congestion window, but not if it means that
+ the value overflows. */
+ if ((u16_t)(pcb->cwnd + pcb->mss) > pcb->cwnd) {
+ pcb->cwnd += pcb->mss;
+ }
+ } else if (pcb->dupacks == 3) {
+ /* Do fast retransmit */
+ tcp_rexmit_fast(pcb);
+ }
+ }
+ }
+ }
+ }
+ /* If Clause (1) or more is true, but not a duplicate ack, reset
+ * count of consecutive duplicate acks */
+ if (!found_dupack) {
+ pcb->dupacks = 0;
+ }
+ } else if (TCP_SEQ_BETWEEN(ackno, pcb->lastack+1, pcb->snd_nxt)){
+ /* We come here when the ACK acknowledges new data. */
+
+ /* Reset the "IN Fast Retransmit" flag, since we are no longer
+ in fast retransmit. Also reset the congestion window to the
+ slow start threshold. */
+ if (pcb->flags & TF_INFR) {
+ pcb->flags &= ~TF_INFR;
+ pcb->cwnd = pcb->ssthresh;
+ }
+
+ /* Reset the number of retransmissions. */
+ pcb->nrtx = 0;
+
+ /* Reset the retransmission time-out. */
+ pcb->rto = (pcb->sa >> 3) + pcb->sv;
+
+ /* Update the send buffer space. Diff between the two can never exceed 64K? */
+ pcb->acked = (u16_t)(ackno - pcb->lastack);
+
+ pcb->snd_buf += pcb->acked;
+
+ /* Reset the fast retransmit variables. */
+ pcb->dupacks = 0;
+ pcb->lastack = ackno;
+
+ /* Update the congestion control variables (cwnd and
+ ssthresh). */
+ if (pcb->state >= ESTABLISHED) {
+ if (pcb->cwnd < pcb->ssthresh) {
+ if ((u16_t)(pcb->cwnd + pcb->mss) > pcb->cwnd) {
+ pcb->cwnd += pcb->mss;
+ }
+ LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_receive: slow start cwnd %"U16_F"\n", pcb->cwnd));
+ } else {
+ u16_t new_cwnd = (pcb->cwnd + pcb->mss * pcb->mss / pcb->cwnd);
+ if (new_cwnd > pcb->cwnd) {
+ pcb->cwnd = new_cwnd;
+ }
+ LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_receive: congestion avoidance cwnd %"U16_F"\n", pcb->cwnd));
+ }
+ }
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: ACK for %"U32_F", unacked->seqno %"U32_F":%"U32_F"\n",
+ ackno,
+ pcb->unacked != NULL?
+ ntohl(pcb->unacked->tcphdr->seqno): 0,
+ pcb->unacked != NULL?
+ ntohl(pcb->unacked->tcphdr->seqno) + TCP_TCPLEN(pcb->unacked): 0));
+
+ /* Remove segment from the unacknowledged list if the incoming
+ ACK acknowlegdes them. */
+ while (pcb->unacked != NULL &&
+ TCP_SEQ_LEQ(ntohl(pcb->unacked->tcphdr->seqno) +
+ TCP_TCPLEN(pcb->unacked), ackno)) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: removing %"U32_F":%"U32_F" from pcb->unacked\n",
+ ntohl(pcb->unacked->tcphdr->seqno),
+ ntohl(pcb->unacked->tcphdr->seqno) +
+ TCP_TCPLEN(pcb->unacked)));
+
+ next = pcb->unacked;
+ pcb->unacked = pcb->unacked->next;
+
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_receive: queuelen %"U16_F" ... ", (u16_t)pcb->snd_queuelen));
+ LWIP_ASSERT("pcb->snd_queuelen >= pbuf_clen(next->p)", (pcb->snd_queuelen >= pbuf_clen(next->p)));
+ /* Prevent ACK for FIN to generate a sent event */
+ if ((pcb->acked != 0) && ((TCPH_FLAGS(next->tcphdr) & TCP_FIN) != 0)) {
+ pcb->acked--;
+ }
+
+ pcb->snd_queuelen -= pbuf_clen(next->p);
+ tcp_seg_free(next);
+
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("%"U16_F" (after freeing unacked)\n", (u16_t)pcb->snd_queuelen));
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_receive: valid queue length", pcb->unacked != NULL ||
+ pcb->unsent != NULL);
+ }
+ }
+
+ /* If there's nothing left to acknowledge, stop the retransmit
+ timer, otherwise reset it to start again */
+ if(pcb->unacked == NULL)
+ pcb->rtime = -1;
+ else
+ pcb->rtime = 0;
+
+ pcb->polltmr = 0;
+ } else {
+ /* Fix bug bug #21582: out of sequence ACK, didn't really ack anything */
+ pcb->acked = 0;
+ }
+
+ /* We go through the ->unsent list to see if any of the segments
+ on the list are acknowledged by the ACK. This may seem
+ strange since an "unsent" segment shouldn't be acked. The
+ rationale is that lwIP puts all outstanding segments on the
+ ->unsent list after a retransmission, so these segments may
+ in fact have been sent once. */
+ while (pcb->unsent != NULL &&
+ TCP_SEQ_BETWEEN(ackno, ntohl(pcb->unsent->tcphdr->seqno) +
+ TCP_TCPLEN(pcb->unsent), pcb->snd_nxt)) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: removing %"U32_F":%"U32_F" from pcb->unsent\n",
+ ntohl(pcb->unsent->tcphdr->seqno), ntohl(pcb->unsent->tcphdr->seqno) +
+ TCP_TCPLEN(pcb->unsent)));
+
+ next = pcb->unsent;
+ pcb->unsent = pcb->unsent->next;
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_receive: queuelen %"U16_F" ... ", (u16_t)pcb->snd_queuelen));
+ LWIP_ASSERT("pcb->snd_queuelen >= pbuf_clen(next->p)", (pcb->snd_queuelen >= pbuf_clen(next->p)));
+ /* Prevent ACK for FIN to generate a sent event */
+ if ((pcb->acked != 0) && ((TCPH_FLAGS(next->tcphdr) & TCP_FIN) != 0)) {
+ pcb->acked--;
+ }
+ pcb->snd_queuelen -= pbuf_clen(next->p);
+ tcp_seg_free(next);
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("%"U16_F" (after freeing unsent)\n", (u16_t)pcb->snd_queuelen));
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_receive: valid queue length",
+ pcb->unacked != NULL || pcb->unsent != NULL);
+ }
+ }
+ /* End of ACK for new data processing. */
+
+ LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_receive: pcb->rttest %"U32_F" rtseq %"U32_F" ackno %"U32_F"\n",
+ pcb->rttest, pcb->rtseq, ackno));
+
+ /* RTT estimation calculations. This is done by checking if the
+ incoming segment acknowledges the segment we use to take a
+ round-trip time measurement. */
+ if (pcb->rttest && TCP_SEQ_LT(pcb->rtseq, ackno)) {
+ /* diff between this shouldn't exceed 32K since this are tcp timer ticks
+ and a round-trip shouldn't be that long... */
+ m = (s16_t)(tcp_ticks - pcb->rttest);
+
+ LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_receive: experienced rtt %"U16_F" ticks (%"U16_F" msec).\n",
+ m, m * TCP_SLOW_INTERVAL));
+
+ /* This is taken directly from VJs original code in his paper */
+ m = m - (pcb->sa >> 3);
+ pcb->sa += m;
+ if (m < 0) {
+ m = -m;
+ }
+ m = m - (pcb->sv >> 2);
+ pcb->sv += m;
+ pcb->rto = (pcb->sa >> 3) + pcb->sv;
+
+ LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_receive: RTO %"U16_F" (%"U16_F" milliseconds)\n",
+ pcb->rto, pcb->rto * TCP_SLOW_INTERVAL));
+
+ pcb->rttest = 0;
+ }
+ }
+
+ /* If the incoming segment contains data, we must process it
+ further. */
+ if (tcplen > 0) {
+ /* This code basically does three things:
+
+ +) If the incoming segment contains data that is the next
+ in-sequence data, this data is passed to the application. This
+ might involve trimming the first edge of the data. The rcv_nxt
+ variable and the advertised window are adjusted.
+
+ +) If the incoming segment has data that is above the next
+ sequence number expected (->rcv_nxt), the segment is placed on
+ the ->ooseq queue. This is done by finding the appropriate
+ place in the ->ooseq queue (which is ordered by sequence
+ number) and trim the segment in both ends if needed. An
+ immediate ACK is sent to indicate that we received an
+ out-of-sequence segment.
+
+ +) Finally, we check if the first segment on the ->ooseq queue
+ now is in sequence (i.e., if rcv_nxt >= ooseq->seqno). If
+ rcv_nxt > ooseq->seqno, we must trim the first edge of the
+ segment on ->ooseq before we adjust rcv_nxt. The data in the
+ segments that are now on sequence are chained onto the
+ incoming segment so that we only need to call the application
+ once.
+ */
+
+ /* First, we check if we must trim the first edge. We have to do
+ this if the sequence number of the incoming segment is less
+ than rcv_nxt, and the sequence number plus the length of the
+ segment is larger than rcv_nxt. */
+ /* if (TCP_SEQ_LT(seqno, pcb->rcv_nxt)){
+ if (TCP_SEQ_LT(pcb->rcv_nxt, seqno + tcplen)) {*/
+ if (TCP_SEQ_BETWEEN(pcb->rcv_nxt, seqno + 1, seqno + tcplen - 1)){
+ /* Trimming the first edge is done by pushing the payload
+ pointer in the pbuf downwards. This is somewhat tricky since
+ we do not want to discard the full contents of the pbuf up to
+ the new starting point of the data since we have to keep the
+ TCP header which is present in the first pbuf in the chain.
+
+ What is done is really quite a nasty hack: the first pbuf in
+ the pbuf chain is pointed to by inseg.p. Since we need to be
+ able to deallocate the whole pbuf, we cannot change this
+ inseg.p pointer to point to any of the later pbufs in the
+ chain. Instead, we point the ->payload pointer in the first
+ pbuf to data in one of the later pbufs. We also set the
+ inseg.data pointer to point to the right place. This way, the
+ ->p pointer will still point to the first pbuf, but the
+ ->p->payload pointer will point to data in another pbuf.
+
+ After we are done with adjusting the pbuf pointers we must
+ adjust the ->data pointer in the seg and the segment
+ length.*/
+
+ off = pcb->rcv_nxt - seqno;
+ p = inseg.p;
+ LWIP_ASSERT("inseg.p != NULL", inseg.p);
+ LWIP_ASSERT("insane offset!", (off < 0x7fff));
+ if (inseg.p->len < off) {
+ LWIP_ASSERT("pbuf too short!", (((s32_t)inseg.p->tot_len) >= off));
+ new_tot_len = (u16_t)(inseg.p->tot_len - off);
+ while (p->len < off) {
+ off -= p->len;
+ /* KJM following line changed (with addition of new_tot_len var)
+ to fix bug #9076
+ inseg.p->tot_len -= p->len; */
+ p->tot_len = new_tot_len;
+ p->len = 0;
+ p = p->next;
+ }
+ if(pbuf_header(p, (s16_t)-off)) {
+ /* Do we need to cope with this failing? Assert for now */
+ LWIP_ASSERT("pbuf_header failed", 0);
+ }
+ } else {
+ if(pbuf_header(inseg.p, (s16_t)-off)) {
+ /* Do we need to cope with this failing? Assert for now */
+ LWIP_ASSERT("pbuf_header failed", 0);
+ }
+ }
+ inseg.len -= (u16_t)(pcb->rcv_nxt - seqno);
+ inseg.tcphdr->seqno = seqno = pcb->rcv_nxt;
+ }
+ else {
+ if (TCP_SEQ_LT(seqno, pcb->rcv_nxt)){
+ /* the whole segment is < rcv_nxt */
+ /* must be a duplicate of a packet that has already been correctly handled */
+
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: duplicate seqno %"U32_F"\n", seqno));
+ tcp_ack_now(pcb);
+ }
+ }
+
+ /* The sequence number must be within the window (above rcv_nxt
+ and below rcv_nxt + rcv_wnd) in order to be further
+ processed. */
+ if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt,
+ pcb->rcv_nxt + pcb->rcv_wnd - 1)){
+ if (pcb->rcv_nxt == seqno) {
+ /* The incoming segment is the next in sequence. We check if
+ we have to trim the end of the segment and update rcv_nxt
+ and pass the data to the application. */
+ tcplen = TCP_TCPLEN(&inseg);
+
+ if (tcplen > pcb->rcv_wnd) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG,
+ ("tcp_receive: other end overran receive window"
+ "seqno %"U32_F" len %"U16_F" right edge %"U32_F"\n",
+ seqno, tcplen, pcb->rcv_nxt + pcb->rcv_wnd));
+ if (TCPH_FLAGS(inseg.tcphdr) & TCP_FIN) {
+ /* Must remove the FIN from the header as we're trimming
+ * that byte of sequence-space from the packet */
+ TCPH_FLAGS_SET(inseg.tcphdr, TCPH_FLAGS(inseg.tcphdr) &~ TCP_FIN);
+ }
+ /* Adjust length of segment to fit in the window. */
+ inseg.len = pcb->rcv_wnd;
+ if (TCPH_FLAGS(inseg.tcphdr) & TCP_SYN) {
+ inseg.len -= 1;
+ }
+ pbuf_realloc(inseg.p, inseg.len);
+ tcplen = TCP_TCPLEN(&inseg);
+ LWIP_ASSERT("tcp_receive: segment not trimmed correctly to rcv_wnd\n",
+ (seqno + tcplen) == (pcb->rcv_nxt + pcb->rcv_wnd));
+ }
+#if TCP_QUEUE_OOSEQ
+ /* Received in-sequence data, adjust ooseq data if:
+ - FIN has been received or
+ - inseq overlaps with ooseq */
+ if (pcb->ooseq != NULL) {
+ if (TCPH_FLAGS(inseg.tcphdr) & TCP_FIN) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG,
+ ("tcp_receive: received in-order FIN, binning ooseq queue\n"));
+ /* Received in-order FIN means anything that was received
+ * out of order must now have been received in-order, so
+ * bin the ooseq queue */
+ while (pcb->ooseq != NULL) {
+ struct tcp_seg *old_ooseq = pcb->ooseq;
+ pcb->ooseq = pcb->ooseq->next;
+ tcp_seg_free(old_ooseq);
+ }
+ }
+ else {
+ next = pcb->ooseq;
+ /* Remove all segments on ooseq that are covered by inseg already.
+ * FIN is copied from ooseq to inseg if present. */
+ while (next &&
+ TCP_SEQ_GEQ(seqno + tcplen,
+ next->tcphdr->seqno + next->len)) {
+ /* inseg cannot have FIN here (already processed above) */
+ if (TCPH_FLAGS(next->tcphdr) & TCP_FIN &&
+ (TCPH_FLAGS(inseg.tcphdr) & TCP_SYN) == 0) {
+ TCPH_SET_FLAG(inseg.tcphdr, TCP_FIN);
+ tcplen = TCP_TCPLEN(&inseg);
+ }
+ prev = next;
+ next = next->next;
+ tcp_seg_free(prev);
+ }
+ /* Now trim right side of inseg if it overlaps with the first
+ * segment on ooseq */
+ if (next &&
+ TCP_SEQ_GT(seqno + tcplen,
+ next->tcphdr->seqno)) {
+ /* inseg cannot have FIN here (already processed above) */
+ inseg.len = (u16_t)(next->tcphdr->seqno - seqno);
+ if (TCPH_FLAGS(inseg.tcphdr) & TCP_SYN) {
+ inseg.len -= 1;
+ }
+ pbuf_realloc(inseg.p, inseg.len);
+ tcplen = TCP_TCPLEN(&inseg);
+ LWIP_ASSERT("tcp_receive: segment not trimmed correctly to ooseq queue\n",
+ (seqno + tcplen) == next->tcphdr->seqno);
+ }
+ pcb->ooseq = next;
+ }
+ }
+#endif /* TCP_QUEUE_OOSEQ */
+
+ pcb->rcv_nxt = seqno + tcplen;
+
+ /* Update the receiver's (our) window. */
+ LWIP_ASSERT("tcp_receive: tcplen > rcv_wnd\n", pcb->rcv_wnd >= tcplen);
+ pcb->rcv_wnd -= tcplen;
+
+ tcp_update_rcv_ann_wnd(pcb);
+
+ /* If there is data in the segment, we make preparations to
+ pass this up to the application. The ->recv_data variable
+ is used for holding the pbuf that goes to the
+ application. The code for reassembling out-of-sequence data
+ chains its data on this pbuf as well.
+
+ If the segment was a FIN, we set the TF_GOT_FIN flag that will
+ be used to indicate to the application that the remote side has
+ closed its end of the connection. */
+ if (inseg.p->tot_len > 0) {
+ recv_data = inseg.p;
+ /* Since this pbuf now is the responsibility of the
+ application, we delete our reference to it so that we won't
+ (mistakingly) deallocate it. */
+ inseg.p = NULL;
+ }
+ if (TCPH_FLAGS(inseg.tcphdr) & TCP_FIN) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: received FIN.\n"));
+ recv_flags |= TF_GOT_FIN;
+ }
+
+#if TCP_QUEUE_OOSEQ
+ /* We now check if we have segments on the ->ooseq queue that
+ are now in sequence. */
+ while (pcb->ooseq != NULL &&
+ pcb->ooseq->tcphdr->seqno == pcb->rcv_nxt) {
+
+ cseg = pcb->ooseq;
+ seqno = pcb->ooseq->tcphdr->seqno;
+
+ pcb->rcv_nxt += TCP_TCPLEN(cseg);
+ LWIP_ASSERT("tcp_receive: ooseq tcplen > rcv_wnd\n",
+ pcb->rcv_wnd >= TCP_TCPLEN(cseg));
+ pcb->rcv_wnd -= TCP_TCPLEN(cseg);
+
+ tcp_update_rcv_ann_wnd(pcb);
+
+ if (cseg->p->tot_len > 0) {
+ /* Chain this pbuf onto the pbuf that we will pass to
+ the application. */
+ if (recv_data) {
+ pbuf_cat(recv_data, cseg->p);
+ } else {
+ recv_data = cseg->p;
+ }
+ cseg->p = NULL;
+ }
+ if (TCPH_FLAGS(cseg->tcphdr) & TCP_FIN) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_receive: dequeued FIN.\n"));
+ recv_flags |= TF_GOT_FIN;
+ if (pcb->state == ESTABLISHED) { /* force passive close or we can move to active close */
+ pcb->state = CLOSE_WAIT;
+ }
+ }
+
+ pcb->ooseq = cseg->next;
+ tcp_seg_free(cseg);
+ }
+#endif /* TCP_QUEUE_OOSEQ */
+
+
+ /* Acknowledge the segment(s). */
+ tcp_ack(pcb);
+
+ } else {
+ /* We get here if the incoming segment is out-of-sequence. */
+ tcp_send_empty_ack(pcb);
+#if TCP_QUEUE_OOSEQ
+ /* We queue the segment on the ->ooseq queue. */
+ if (pcb->ooseq == NULL) {
+ pcb->ooseq = tcp_seg_copy(&inseg);
+ } else {
+ /* If the queue is not empty, we walk through the queue and
+ try to find a place where the sequence number of the
+ incoming segment is between the sequence numbers of the
+ previous and the next segment on the ->ooseq queue. That is
+ the place where we put the incoming segment. If needed, we
+ trim the second edges of the previous and the incoming
+ segment so that it will fit into the sequence.
+
+ If the incoming segment has the same sequence number as a
+ segment on the ->ooseq queue, we discard the segment that
+ contains less data. */
+
+ prev = NULL;
+ for(next = pcb->ooseq; next != NULL; next = next->next) {
+ if (seqno == next->tcphdr->seqno) {
+ /* The sequence number of the incoming segment is the
+ same as the sequence number of the segment on
+ ->ooseq. We check the lengths to see which one to
+ discard. */
+ if (inseg.len > next->len) {
+ /* The incoming segment is larger than the old
+ segment. We replace some segments with the new
+ one. */
+ cseg = tcp_seg_copy(&inseg);
+ if (cseg != NULL) {
+ if (prev != NULL) {
+ prev->next = cseg;
+ } else {
+ pcb->ooseq = cseg;
+ }
+ tcp_oos_insert_segment(cseg, next);
+ }
+ break;
+ } else {
+ /* Either the lenghts are the same or the incoming
+ segment was smaller than the old one; in either
+ case, we ditch the incoming segment. */
+ break;
+ }
+ } else {
+ if (prev == NULL) {
+ if (TCP_SEQ_LT(seqno, next->tcphdr->seqno)) {
+ /* The sequence number of the incoming segment is lower
+ than the sequence number of the first segment on the
+ queue. We put the incoming segment first on the
+ queue. */
+ cseg = tcp_seg_copy(&inseg);
+ if (cseg != NULL) {
+ pcb->ooseq = cseg;
+ tcp_oos_insert_segment(cseg, next);
+ }
+ break;
+ }
+ } else {
+ /*if (TCP_SEQ_LT(prev->tcphdr->seqno, seqno) &&
+ TCP_SEQ_LT(seqno, next->tcphdr->seqno)) {*/
+ if (TCP_SEQ_BETWEEN(seqno, prev->tcphdr->seqno+1, next->tcphdr->seqno-1)) {
+ /* The sequence number of the incoming segment is in
+ between the sequence numbers of the previous and
+ the next segment on ->ooseq. We trim trim the previous
+ segment, delete next segments that included in received segment
+ and trim received, if needed. */
+ cseg = tcp_seg_copy(&inseg);
+ if (cseg != NULL) {
+ if (TCP_SEQ_GT(prev->tcphdr->seqno + prev->len, seqno)) {
+ /* We need to trim the prev segment. */
+ prev->len = (u16_t)(seqno - prev->tcphdr->seqno);
+ pbuf_realloc(prev->p, prev->len);
+ }
+ prev->next = cseg;
+ tcp_oos_insert_segment(cseg, next);
+ }
+ break;
+ }
+ }
+ /* If the "next" segment is the last segment on the
+ ooseq queue, we add the incoming segment to the end
+ of the list. */
+ if (next->next == NULL &&
+ TCP_SEQ_GT(seqno, next->tcphdr->seqno)) {
+ if (TCPH_FLAGS(next->tcphdr) & TCP_FIN) {
+ /* segment "next" already contains all data */
+ break;
+ }
+ next->next = tcp_seg_copy(&inseg);
+ if (next->next != NULL) {
+ if (TCP_SEQ_GT(next->tcphdr->seqno + next->len, seqno)) {
+ /* We need to trim the last segment. */
+ next->len = (u16_t)(seqno - next->tcphdr->seqno);
+ pbuf_realloc(next->p, next->len);
+ }
+ /* check if the remote side overruns our receive window */
+ if ((u32_t)tcplen + seqno > pcb->rcv_nxt + (u32_t)pcb->rcv_wnd) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG,
+ ("tcp_receive: other end overran receive window"
+ "seqno %"U32_F" len %"U16_F" right edge %"U32_F"\n",
+ seqno, tcplen, pcb->rcv_nxt + pcb->rcv_wnd));
+ if (TCPH_FLAGS(next->next->tcphdr) & TCP_FIN) {
+ /* Must remove the FIN from the header as we're trimming
+ * that byte of sequence-space from the packet */
+ TCPH_FLAGS_SET(next->next->tcphdr, TCPH_FLAGS(next->next->tcphdr) &~ TCP_FIN);
+ }
+ /* Adjust length of segment to fit in the window. */
+ next->next->len = pcb->rcv_nxt + pcb->rcv_wnd - seqno;
+ pbuf_realloc(next->next->p, next->next->len);
+ tcplen = TCP_TCPLEN(next->next);
+ LWIP_ASSERT("tcp_receive: segment not trimmed correctly to rcv_wnd\n",
+ (seqno + tcplen) == (pcb->rcv_nxt + pcb->rcv_wnd));
+ }
+ }
+ break;
+ }
+ }
+ prev = next;
+ }
+ }
+#endif /* TCP_QUEUE_OOSEQ */
+
+ }
+ } else {
+ /* The incoming segment is not withing the window. */
+ tcp_send_empty_ack(pcb);
+ }
+ } else {
+ /* Segments with length 0 is taken care of here. Segments that
+ fall out of the window are ACKed. */
+ /*if (TCP_SEQ_GT(pcb->rcv_nxt, seqno) ||
+ TCP_SEQ_GEQ(seqno, pcb->rcv_nxt + pcb->rcv_wnd)) {*/
+ if(!TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt + pcb->rcv_wnd-1)){
+ tcp_ack_now(pcb);
+ }
+ }
+}
+
+/**
+ * Parses the options contained in the incoming segment.
+ *
+ * Called from tcp_listen_input() and tcp_process().
+ * Currently, only the MSS option is supported!
+ *
+ * @param pcb the tcp_pcb for which a segment arrived
+ */
+static void
+tcp_parseopt(struct tcp_pcb *pcb)
+{
+ u16_t c, max_c;
+ u16_t mss;
+ u8_t *opts, opt;
+#if LWIP_TCP_TIMESTAMPS
+ u32_t tsval;
+#endif
+
+ opts = (u8_t *)tcphdr + TCP_HLEN;
+
+ /* Parse the TCP MSS option, if present. */
+ if(TCPH_HDRLEN(tcphdr) > 0x5) {
+ max_c = (TCPH_HDRLEN(tcphdr) - 5) << 2;
+ for (c = 0; c < max_c; ) {
+ opt = opts[c];
+ switch (opt) {
+ case 0x00:
+ /* End of options. */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: EOL\n"));
+ return;
+ case 0x01:
+ /* NOP option. */
+ ++c;
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: NOP\n"));
+ break;
+ case 0x02:
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: MSS\n"));
+ if (opts[c + 1] != 0x04 || c + 0x04 > max_c) {
+ /* Bad length */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
+ return;
+ }
+ /* An MSS option with the right option length. */
+ mss = (opts[c + 2] << 8) | opts[c + 3];
+ /* Limit the mss to the configured TCP_MSS and prevent division by zero */
+ pcb->mss = ((mss > TCP_MSS) || (mss == 0)) ? TCP_MSS : mss;
+ /* Advance to next option */
+ c += 0x04;
+ break;
+#if LWIP_TCP_TIMESTAMPS
+ case 0x08:
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: TS\n"));
+ if (opts[c + 1] != 0x0A || c + 0x0A > max_c) {
+ /* Bad length */
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
+ return;
+ }
+ /* TCP timestamp option with valid length */
+ tsval = (opts[c+2]) | (opts[c+3] << 8) |
+ (opts[c+4] << 16) | (opts[c+5] << 24);
+ if (flags & TCP_SYN) {
+ pcb->ts_recent = ntohl(tsval);
+ pcb->flags |= TF_TIMESTAMP;
+ } else if (TCP_SEQ_BETWEEN(pcb->ts_lastacksent, seqno, seqno+tcplen)) {
+ pcb->ts_recent = ntohl(tsval);
+ }
+ /* Advance to next option */
+ c += 0x0A;
+ break;
+#endif
+ default:
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: other\n"));
+ if (opts[c + 1] == 0) {
+ LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
+ /* If the length field is zero, the options are malformed
+ and we don't process them further. */
+ return;
+ }
+ /* All other options have a length field, so that we easily
+ can skip past them. */
+ c += opts[c + 1];
+ }
+ }
+ }
+}
+
+#endif /* LWIP_TCP */