John Lowe
Embedded WebSockets Experiment
Diff: Core/lwIP/core/tcp_out.c
- Revision:
- 0:6dee052a3fa4
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/Core/lwIP/core/tcp_out.c Tue Jul 26 05:30:53 2011 +0000
@@ -0,0 +1,1032 @@
+/**
+ * @file
+ * Transmission Control Protocol, outgoing traffic
+ *
+ * The output functions of TCP.
+ *
+ */
+
+/*
+ * 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.h"
+#include "lwip/def.h"
+#include "lwip/mem.h"
+#include "lwip/memp.h"
+#include "lwip/sys.h"
+#include "lwip/ip_addr.h"
+#include "lwip/netif.h"
+#include "lwip/inet.h"
+#include "lwip/inet_chksum.h"
+#include "lwip/stats.h"
+#include "lwip/snmp.h"
+
+#include <string.h>
+
+/* Forward declarations.*/
+static void tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb);
+
+static struct tcp_hdr *
+tcp_output_set_header(struct tcp_pcb *pcb, struct pbuf *p, int optlen,
+ u32_t seqno_be /* already in network byte order */)
+{
+ struct tcp_hdr *tcphdr = (struct tcp_hdr *)p->payload;
+ tcphdr->src = htons(pcb->local_port);
+ tcphdr->dest = htons(pcb->remote_port);
+ tcphdr->seqno = seqno_be;
+ tcphdr->ackno = htonl(pcb->rcv_nxt);
+ TCPH_FLAGS_SET(tcphdr, TCP_ACK);
+ tcphdr->wnd = htons(pcb->rcv_ann_wnd);
+ tcphdr->urgp = 0;
+ TCPH_HDRLEN_SET(tcphdr, (5 + optlen / 4));
+ tcphdr->chksum = 0;
+
+ /* If we're sending a packet, update the announced right window edge */
+ pcb->rcv_ann_right_edge = pcb->rcv_nxt + pcb->rcv_ann_wnd;
+
+ return tcphdr;
+}
+
+/**
+ * Called by tcp_close() to send a segment including flags but not data.
+ *
+ * @param pcb the tcp_pcb over which to send a segment
+ * @param flags the flags to set in the segment header
+ * @return ERR_OK if sent, another err_t otherwise
+ */
+err_t
+tcp_send_ctrl(struct tcp_pcb *pcb, u8_t flags)
+{
+ /* no data, no length, flags, copy=1, no optdata */
+ return tcp_enqueue(pcb, NULL, 0, flags, TCP_WRITE_FLAG_COPY, 0);
+}
+
+/**
+ * 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().
+ *
+ * @param pcb Protocol control block of the TCP connection to enqueue data for.
+ * @param data pointer to the data to send
+ * @param len length (in bytes) of the data to send
+ * @param 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,
+ * @return ERR_OK if enqueued, another err_t on error
+ *
+ * @see tcp_write()
+ */
+err_t
+tcp_write(struct tcp_pcb *pcb, const void *data, u16_t len, u8_t apiflags)
+{
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_write(pcb=%p, data=%p, len=%"U16_F", apiflags=%"U16_F")\n", (void *)pcb,
+ data, len, (u16_t)apiflags));
+ /* connection is in valid state for data transmission? */
+ if (pcb->state == ESTABLISHED ||
+ pcb->state == CLOSE_WAIT ||
+ pcb->state == SYN_SENT ||
+ pcb->state == SYN_RCVD) {
+ if (len > 0) {
+#if LWIP_TCP_TIMESTAMPS
+ return tcp_enqueue(pcb, (void *)data, len, 0, apiflags,
+ pcb->flags & TF_TIMESTAMP ? TF_SEG_OPTS_TS : 0);
+#else
+ return tcp_enqueue(pcb, (void *)data, len, 0, apiflags, 0);
+#endif
+ }
+ return ERR_OK;
+ } else {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_STATE | 3, ("tcp_write() called in invalid state\n"));
+ return ERR_CONN;
+ }
+}
+
+/**
+ * Enqueue data and/or TCP options for transmission
+ *
+ * Called by tcp_connect(), tcp_listen_input(), tcp_send_ctrl() and tcp_write().
+ *
+ * @param pcb Protocol control block for the TCP connection to enqueue data for.
+ * @param arg Pointer to the data to be enqueued for sending.
+ * @param len Data length in bytes
+ * @param flags tcp header flags to set in the outgoing segment
+ * @param 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,
+ * @param optflags options to include in segment later on (see definition of struct tcp_seg)
+ */
+err_t
+tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len,
+ u8_t flags, u8_t apiflags, u8_t optflags)
+{
+ struct pbuf *p;
+ struct tcp_seg *seg, *useg, *queue;
+ u32_t seqno;
+ u16_t left, seglen;
+ void *ptr;
+ u16_t queuelen;
+ u8_t optlen;
+
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG,
+ ("tcp_enqueue(pcb=%p, arg=%p, len=%"U16_F", flags=%"X16_F", apiflags=%"U16_F")\n",
+ (void *)pcb, arg, len, (u16_t)flags, (u16_t)apiflags));
+ LWIP_ERROR("tcp_enqueue: packet needs payload, options, or SYN/FIN (programmer violates API)",
+ ((len != 0) || (optflags != 0) || ((flags & (TCP_SYN | TCP_FIN)) != 0)),
+ return ERR_ARG;);
+ LWIP_ERROR("tcp_enqueue: len != 0 || arg == NULL (programmer violates API)",
+ ((len != 0) || (arg == NULL)), return ERR_ARG;);
+
+ /* fail on too much data */
+ if (len > pcb->snd_buf) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too much data (len=%"U16_F" > snd_buf=%"U16_F")\n", len, pcb->snd_buf));
+ pcb->flags |= TF_NAGLEMEMERR;
+ return ERR_MEM;
+ }
+ left = len;
+ ptr = arg;
+
+ optlen = LWIP_TCP_OPT_LENGTH(optflags);
+
+ /* seqno will be the sequence number of the first segment enqueued
+ * by the call to this function. */
+ seqno = pcb->snd_lbb;
+
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: queuelen: %"U16_F"\n", (u16_t)pcb->snd_queuelen));
+
+ /* If total number of pbufs on the unsent/unacked queues exceeds the
+ * configured maximum, return an error */
+ queuelen = pcb->snd_queuelen;
+ /* check for configured max queuelen and possible overflow */
+ if ((queuelen >= TCP_SND_QUEUELEN) || (queuelen > TCP_SNDQUEUELEN_OVERFLOW)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too long queue %"U16_F" (max %"U16_F")\n", queuelen, TCP_SND_QUEUELEN));
+ TCP_STATS_INC(tcp.memerr);
+ pcb->flags |= TF_NAGLEMEMERR;
+ return ERR_MEM;
+ }
+ if (queuelen != 0) {
+ LWIP_ASSERT("tcp_enqueue: pbufs on queue => at least one queue non-empty",
+ pcb->unacked != NULL || pcb->unsent != NULL);
+ } else {
+ LWIP_ASSERT("tcp_enqueue: no pbufs on queue => both queues empty",
+ pcb->unacked == NULL && pcb->unsent == NULL);
+ }
+
+ /* First, break up the data into segments and tuck them together in
+ * the local "queue" variable. */
+ useg = queue = seg = NULL;
+ seglen = 0;
+ while (queue == NULL || left > 0) {
+ /* The segment length (including options) should be at most the MSS */
+ seglen = left > (pcb->mss - optlen) ? (pcb->mss - optlen) : left;
+
+ /* Allocate memory for tcp_seg, and fill in fields. */
+ seg = (struct tcp_seg *)memp_malloc(MEMP_TCP_SEG);
+ if (seg == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2,
+ ("tcp_enqueue: could not allocate memory for tcp_seg\n"));
+ goto memerr;
+ }
+ seg->next = NULL;
+ seg->p = NULL;
+
+ /* first segment of to-be-queued data? */
+ if (queue == NULL) {
+ queue = seg;
+ }
+ /* subsequent segments of to-be-queued data */
+ else {
+ /* Attach the segment to the end of the queued segments */
+ LWIP_ASSERT("useg != NULL", useg != NULL);
+ useg->next = seg;
+ }
+ /* remember last segment of to-be-queued data for next iteration */
+ useg = seg;
+
+ /* If copy is set, memory should be allocated
+ * and data copied into pbuf, otherwise data comes from
+ * ROM or other static memory, and need not be copied. */
+ if (apiflags & TCP_WRITE_FLAG_COPY) {
+ if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, seglen + optlen, PBUF_RAM)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2,
+ ("tcp_enqueue : could not allocate memory for pbuf copy size %"U16_F"\n", seglen));
+ goto memerr;
+ }
+ LWIP_ASSERT("check that first pbuf can hold the complete seglen",
+ (seg->p->len >= seglen + optlen));
+ queuelen += pbuf_clen(seg->p);
+ if (arg != NULL) {
+ MEMCPY((char *)seg->p->payload + optlen, ptr, seglen);
+ }
+ seg->dataptr = seg->p->payload;
+ }
+ /* do not copy data */
+ else {
+ /* First, allocate a pbuf for the headers. */
+ if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, optlen, PBUF_RAM)) == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2,
+ ("tcp_enqueue: could not allocate memory for header pbuf\n"));
+ goto memerr;
+ }
+ queuelen += pbuf_clen(seg->p);
+
+ /* Second, allocate a pbuf for holding the data.
+ * since the referenced data is available at least until it is sent out on the
+ * link (as it has to be ACKed by the remote party) we can safely use PBUF_ROM
+ * instead of PBUF_REF here.
+ */
+ if (left > 0) {
+ if ((p = pbuf_alloc(PBUF_RAW, seglen, PBUF_ROM)) == NULL) {
+ /* If allocation fails, we have to deallocate the header pbuf as well. */
+ pbuf_free(seg->p);
+ seg->p = NULL;
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2,
+ ("tcp_enqueue: could not allocate memory for zero-copy pbuf\n"));
+ goto memerr;
+ }
+ ++queuelen;
+ /* reference the non-volatile payload data */
+ p->payload = ptr;
+ seg->dataptr = ptr;
+
+ /* Concatenate the headers and data pbufs together. */
+ pbuf_cat(seg->p/*header*/, p/*data*/);
+ p = NULL;
+ }
+ }
+
+ /* Now that there are more segments queued, we check again if the
+ length of the queue exceeds the configured maximum or overflows. */
+ if ((queuelen > TCP_SND_QUEUELEN) || (queuelen > TCP_SNDQUEUELEN_OVERFLOW)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: queue too long %"U16_F" (%"U16_F")\n", queuelen, TCP_SND_QUEUELEN));
+ goto memerr;
+ }
+
+ seg->len = seglen;
+
+ /* build TCP header */
+ if (pbuf_header(seg->p, TCP_HLEN)) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: no room for TCP header in pbuf.\n"));
+ TCP_STATS_INC(tcp.err);
+ goto memerr;
+ }
+ seg->tcphdr = (struct tcp_hdr *)seg->p->payload;
+ seg->tcphdr->src = htons(pcb->local_port);
+ seg->tcphdr->dest = htons(pcb->remote_port);
+ seg->tcphdr->seqno = htonl(seqno);
+ seg->tcphdr->urgp = 0;
+ TCPH_FLAGS_SET(seg->tcphdr, flags);
+ /* don't fill in tcphdr->ackno and tcphdr->wnd until later */
+
+ seg->flags = optflags;
+
+ /* Set the length of the header */
+ TCPH_HDRLEN_SET(seg->tcphdr, (5 + optlen / 4));
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_TRACE, ("tcp_enqueue: queueing %"U32_F":%"U32_F" (0x%"X16_F")\n",
+ ntohl(seg->tcphdr->seqno),
+ ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg),
+ (u16_t)flags));
+
+ left -= seglen;
+ seqno += seglen;
+ ptr = (void *)((u8_t *)ptr + seglen);
+ }
+
+ /* Now that the data to be enqueued has been broken up into TCP
+ segments in the queue variable, we add them to the end of the
+ pcb->unsent queue. */
+ if (pcb->unsent == NULL) {
+ useg = NULL;
+ }
+ else {
+ for (useg = pcb->unsent; useg->next != NULL; useg = useg->next);
+ }
+ /* { useg is last segment on the unsent queue, NULL if list is empty } */
+
+ /* If there is room in the last pbuf on the unsent queue,
+ chain the first pbuf on the queue together with that. */
+ if (useg != NULL &&
+ TCP_TCPLEN(useg) != 0 &&
+ !(TCPH_FLAGS(useg->tcphdr) & (TCP_SYN | TCP_FIN)) &&
+ !(flags & (TCP_SYN | TCP_FIN)) &&
+ /* fit within max seg size */
+ (useg->len + queue->len <= pcb->mss) &&
+ /* only concatenate segments with the same options */
+ (useg->flags == queue->flags) &&
+ /* segments are consecutive */
+ (ntohl(useg->tcphdr->seqno) + useg->len == ntohl(queue->tcphdr->seqno)) ) {
+ /* Remove TCP header from first segment of our to-be-queued list */
+ if(pbuf_header(queue->p, -(TCP_HLEN + optlen))) {
+ /* Can we cope with this failing? Just assert for now */
+ LWIP_ASSERT("pbuf_header failed\n", 0);
+ TCP_STATS_INC(tcp.err);
+ goto memerr;
+ }
+ if (queue->p->len == 0) {
+ /* free the first (header-only) pbuf if it is now empty (contained only headers) */
+ struct pbuf *old_q = queue->p;
+ queue->p = queue->p->next;
+ old_q->next = NULL;
+ queuelen--;
+ pbuf_free(old_q);
+ }
+ LWIP_ASSERT("zero-length pbuf", (queue->p != NULL) && (queue->p->len > 0));
+ pbuf_cat(useg->p, queue->p);
+ useg->len += queue->len;
+ useg->next = queue->next;
+
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE, ("tcp_enqueue: chaining segments, new len %"U16_F"\n", useg->len));
+ if (seg == queue) {
+ seg = useg;
+ seglen = useg->len;
+ }
+ memp_free(MEMP_TCP_SEG, queue);
+ }
+ else {
+ /* empty list */
+ if (useg == NULL) {
+ /* initialize list with this segment */
+ pcb->unsent = queue;
+ }
+ /* enqueue segment */
+ else {
+ useg->next = queue;
+ }
+ }
+ if ((flags & TCP_SYN) || (flags & TCP_FIN)) {
+ ++len;
+ }
+ if (flags & TCP_FIN) {
+ pcb->flags |= TF_FIN;
+ }
+ pcb->snd_lbb += len;
+
+ pcb->snd_buf -= len;
+
+ /* update number of segments on the queues */
+ pcb->snd_queuelen = queuelen;
+ LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: %"S16_F" (after enqueued)\n", pcb->snd_queuelen));
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_enqueue: valid queue length",
+ pcb->unacked != NULL || pcb->unsent != NULL);
+ }
+
+ /* Set the PSH flag in the last segment that we enqueued, but only
+ if the segment has data (indicated by seglen > 0). */
+ if (seg != NULL && seglen > 0 && seg->tcphdr != NULL && ((apiflags & TCP_WRITE_FLAG_MORE)==0)) {
+ TCPH_SET_FLAG(seg->tcphdr, TCP_PSH);
+ }
+
+ return ERR_OK;
+memerr:
+ pcb->flags |= TF_NAGLEMEMERR;
+ TCP_STATS_INC(tcp.memerr);
+
+ if (queue != NULL) {
+ tcp_segs_free(queue);
+ }
+ if (pcb->snd_queuelen != 0) {
+ LWIP_ASSERT("tcp_enqueue: valid queue length", pcb->unacked != NULL ||
+ pcb->unsent != NULL);
+ }
+ LWIP_DEBUGF(TCP_QLEN_DEBUG | LWIP_DBG_STATE, ("tcp_enqueue: %"S16_F" (with mem err)\n", pcb->snd_queuelen));
+ return ERR_MEM;
+}
+
+
+#if LWIP_TCP_TIMESTAMPS
+/* Build a timestamp option (12 bytes long) at the specified options pointer)
+ *
+ * @param pcb tcp_pcb
+ * @param opts option pointer where to store the timestamp option
+ */
+static void
+tcp_build_timestamp_option(struct tcp_pcb *pcb, u32_t *opts)
+{
+ /* Pad with two NOP options to make everything nicely aligned */
+ opts[0] = htonl(0x0101080A);
+ opts[1] = htonl(sys_now());
+ opts[2] = htonl(pcb->ts_recent);
+}
+#endif
+
+
+/**
+ * Find out what we can send and send it
+ *
+ * @param pcb Protocol control block for the TCP connection to send data
+ * @return ERR_OK if data has been sent or nothing to send
+ * another err_t on error
+ */
+err_t
+tcp_output(struct tcp_pcb *pcb)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+ struct tcp_seg *seg, *useg;
+ u32_t wnd, snd_nxt;
+#if TCP_CWND_DEBUG
+ s16_t i = 0;
+#endif /* TCP_CWND_DEBUG */
+ u8_t optlen = 0;
+
+ /* First, check if we are invoked by the TCP input processing
+ code. If so, we do not output anything. Instead, we rely on the
+ input processing code to call us when input processing is done
+ with. */
+ if (tcp_input_pcb == pcb) {
+ return ERR_OK;
+ }
+
+ wnd = LWIP_MIN(pcb->snd_wnd, pcb->cwnd);
+
+ seg = pcb->unsent;
+
+ /* useg should point to last segment on unacked queue */
+ useg = pcb->unacked;
+ if (useg != NULL) {
+ for (; useg->next != NULL; useg = useg->next);
+ }
+
+ /* If the TF_ACK_NOW flag is set and no data will be sent (either
+ * because the ->unsent queue is empty or because the window does
+ * not allow it), construct an empty ACK segment and send it.
+ *
+ * If data is to be sent, we will just piggyback the ACK (see below).
+ */
+ if (pcb->flags & TF_ACK_NOW &&
+ (seg == NULL ||
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > wnd)) {
+#if LWIP_TCP_TIMESTAMPS
+ if (pcb->flags & TF_TIMESTAMP)
+ optlen = LWIP_TCP_OPT_LENGTH(TF_SEG_OPTS_TS);
+#endif
+ p = pbuf_alloc(PBUF_IP, TCP_HLEN + optlen, PBUF_RAM);
+ if (p == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: (ACK) could not allocate pbuf\n"));
+ return ERR_BUF;
+ }
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG,
+ ("tcp_output: sending ACK for %"U32_F"\n", pcb->rcv_nxt));
+ /* remove ACK flags from the PCB, as we send an empty ACK now */
+ pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
+
+ tcphdr = tcp_output_set_header(pcb, p, optlen, htonl(pcb->snd_nxt));
+
+ /* NB. MSS option is only sent on SYNs, so ignore it here */
+#if LWIP_TCP_TIMESTAMPS
+ pcb->ts_lastacksent = pcb->rcv_nxt;
+
+ if (pcb->flags & TF_TIMESTAMP)
+ tcp_build_timestamp_option(pcb, (u32_t *)(tcphdr + 1));
+#endif
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, &(pcb->local_ip), &(pcb->remote_ip),
+ IP_PROTO_TCP, p->tot_len);
+#endif
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP, &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+ pbuf_free(p);
+
+ return ERR_OK;
+ }
+
+#if TCP_OUTPUT_DEBUG
+ if (seg == NULL) {
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: nothing to send (%p)\n",
+ (void*)pcb->unsent));
+ }
+#endif /* TCP_OUTPUT_DEBUG */
+#if TCP_CWND_DEBUG
+ if (seg == NULL) {
+ LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %"U16_F
+ ", cwnd %"U16_F", wnd %"U32_F
+ ", seg == NULL, ack %"U32_F"\n",
+ pcb->snd_wnd, pcb->cwnd, wnd, pcb->lastack));
+ } else {
+ LWIP_DEBUGF(TCP_CWND_DEBUG,
+ ("tcp_output: snd_wnd %"U16_F", cwnd %"U16_F", wnd %"U32_F
+ ", effwnd %"U32_F", seq %"U32_F", ack %"U32_F"\n",
+ pcb->snd_wnd, pcb->cwnd, wnd,
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len,
+ ntohl(seg->tcphdr->seqno), pcb->lastack));
+ }
+#endif /* TCP_CWND_DEBUG */
+ /* data available and window allows it to be sent? */
+ while (seg != NULL &&
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len <= wnd) {
+ LWIP_ASSERT("RST not expected here!",
+ (TCPH_FLAGS(seg->tcphdr) & TCP_RST) == 0);
+ /* Stop sending if the nagle algorithm would prevent it
+ * Don't stop:
+ * - if tcp_enqueue had a memory error before (prevent delayed ACK timeout) or
+ * - if FIN was already enqueued for this PCB (SYN is always alone in a segment -
+ * either seg->next != NULL or pcb->unacked == NULL;
+ * RST is no sent using tcp_enqueue/tcp_output.
+ */
+ if((tcp_do_output_nagle(pcb) == 0) &&
+ ((pcb->flags & (TF_NAGLEMEMERR | TF_FIN)) == 0)){
+ break;
+ }
+#if TCP_CWND_DEBUG
+ LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %"U16_F", cwnd %"U16_F", wnd %"U32_F", effwnd %"U32_F", seq %"U32_F", ack %"U32_F", i %"S16_F"\n",
+ pcb->snd_wnd, pcb->cwnd, wnd,
+ ntohl(seg->tcphdr->seqno) + seg->len -
+ pcb->lastack,
+ ntohl(seg->tcphdr->seqno), pcb->lastack, i));
+ ++i;
+#endif /* TCP_CWND_DEBUG */
+
+ pcb->unsent = seg->next;
+
+ if (pcb->state != SYN_SENT) {
+ TCPH_SET_FLAG(seg->tcphdr, TCP_ACK);
+ pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
+ }
+
+ tcp_output_segment(seg, pcb);
+ snd_nxt = ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg);
+ if (TCP_SEQ_LT(pcb->snd_nxt, snd_nxt)) {
+ pcb->snd_nxt = snd_nxt;
+ }
+ /* put segment on unacknowledged list if length > 0 */
+ if (TCP_TCPLEN(seg) > 0) {
+ seg->next = NULL;
+ /* unacked list is empty? */
+ if (pcb->unacked == NULL) {
+ pcb->unacked = seg;
+ useg = seg;
+ /* unacked list is not empty? */
+ } else {
+ /* In the case of fast retransmit, the packet should not go to the tail
+ * of the unacked queue, but rather somewhere before it. We need to check for
+ * this case. -STJ Jul 27, 2004 */
+ if (TCP_SEQ_LT(ntohl(seg->tcphdr->seqno), ntohl(useg->tcphdr->seqno))){
+ /* add segment to before tail of unacked list, keeping the list sorted */
+ struct tcp_seg **cur_seg = &(pcb->unacked);
+ while (*cur_seg &&
+ TCP_SEQ_LT(ntohl((*cur_seg)->tcphdr->seqno), ntohl(seg->tcphdr->seqno))) {
+ cur_seg = &((*cur_seg)->next );
+ }
+ seg->next = (*cur_seg);
+ (*cur_seg) = seg;
+ } else {
+ /* add segment to tail of unacked list */
+ useg->next = seg;
+ useg = useg->next;
+ }
+ }
+ /* do not queue empty segments on the unacked list */
+ } else {
+ tcp_seg_free(seg);
+ }
+ seg = pcb->unsent;
+ }
+
+ if (seg != NULL && pcb->persist_backoff == 0 &&
+ ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > pcb->snd_wnd) {
+ /* prepare for persist timer */
+ pcb->persist_cnt = 0;
+ pcb->persist_backoff = 1;
+ }
+
+ pcb->flags &= ~TF_NAGLEMEMERR;
+ return ERR_OK;
+}
+
+/**
+ * Called by tcp_output() to actually send a TCP segment over IP.
+ *
+ * @param seg the tcp_seg to send
+ * @param pcb the tcp_pcb for the TCP connection used to send the segment
+ */
+static void
+tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb)
+{
+ u16_t len;
+ struct netif *netif;
+ u32_t *opts;
+
+ /** @bug Exclude retransmitted segments from this count. */
+ snmp_inc_tcpoutsegs();
+
+ /* The TCP header has already been constructed, but the ackno and
+ wnd fields remain. */
+ seg->tcphdr->ackno = htonl(pcb->rcv_nxt);
+
+ /* advertise our receive window size in this TCP segment */
+ seg->tcphdr->wnd = htons(pcb->rcv_ann_wnd);
+
+ pcb->rcv_ann_right_edge = pcb->rcv_nxt + pcb->rcv_ann_wnd;
+
+ /* Add any requested options. NB MSS option is only set on SYN
+ packets, so ignore it here */
+ opts = (u32_t *)(seg->tcphdr + 1);
+ if (seg->flags & TF_SEG_OPTS_MSS) {
+ TCP_BUILD_MSS_OPTION(*opts);
+ opts += 1;
+ }
+#if LWIP_TCP_TIMESTAMPS
+ pcb->ts_lastacksent = pcb->rcv_nxt;
+
+ if (seg->flags & TF_SEG_OPTS_TS) {
+ tcp_build_timestamp_option(pcb, opts);
+ opts += 3;
+ }
+#endif
+
+ /* If we don't have a local IP address, we get one by
+ calling ip_route(). */
+ if (ip_addr_isany(&(pcb->local_ip))) {
+ netif = ip_route(&(pcb->remote_ip));
+ if (netif == NULL) {
+ return;
+ }
+ ip_addr_set(&(pcb->local_ip), &(netif->ip_addr));
+ }
+
+ /* Set retransmission timer running if it is not currently enabled */
+ if(pcb->rtime == -1)
+ pcb->rtime = 0;
+
+ if (pcb->rttest == 0) {
+ pcb->rttest = tcp_ticks;
+ pcb->rtseq = ntohl(seg->tcphdr->seqno);
+
+ LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_output_segment: rtseq %"U32_F"\n", pcb->rtseq));
+ }
+ LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output_segment: %"U32_F":%"U32_F"\n",
+ htonl(seg->tcphdr->seqno), htonl(seg->tcphdr->seqno) +
+ seg->len));
+
+ len = (u16_t)((u8_t *)seg->tcphdr - (u8_t *)seg->p->payload);
+
+ seg->p->len -= len;
+ seg->p->tot_len -= len;
+
+ seg->p->payload = seg->tcphdr;
+
+ seg->tcphdr->chksum = 0;
+#if CHECKSUM_GEN_TCP
+ seg->tcphdr->chksum = inet_chksum_pseudo(seg->p,
+ &(pcb->local_ip),
+ &(pcb->remote_ip),
+ IP_PROTO_TCP, seg->p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP, &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos,
+ IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+}
+
+/**
+ * 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.
+ *
+ * @param seqno the sequence number to use for the outgoing segment
+ * @param ackno the acknowledge number to use for the outgoing segment
+ * @param local_ip the local IP address to send the segment from
+ * @param remote_ip the remote IP address to send the segment to
+ * @param local_port the local TCP port to send the segment from
+ * @param remote_port the remote TCP port to send the segment to
+ */
+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)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+ p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM);
+ if (p == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_rst: could not allocate memory for pbuf\n"));
+ return;
+ }
+ LWIP_ASSERT("check that first pbuf can hold struct tcp_hdr",
+ (p->len >= sizeof(struct tcp_hdr)));
+
+ tcphdr = (struct tcp_hdr *)p->payload;
+ tcphdr->src = htons(local_port);
+ tcphdr->dest = htons(remote_port);
+ tcphdr->seqno = htonl(seqno);
+ tcphdr->ackno = htonl(ackno);
+ TCPH_FLAGS_SET(tcphdr, TCP_RST | TCP_ACK);
+ tcphdr->wnd = htons(TCP_WND);
+ tcphdr->urgp = 0;
+ TCPH_HDRLEN_SET(tcphdr, 5);
+
+ tcphdr->chksum = 0;
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, local_ip, remote_ip,
+ IP_PROTO_TCP, p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+ snmp_inc_tcpoutrsts();
+ /* Send output with hardcoded TTL since we have no access to the pcb */
+ ip_output(p, local_ip, remote_ip, TCP_TTL, 0, IP_PROTO_TCP);
+ pbuf_free(p);
+ LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_rst: seqno %"U32_F" ackno %"U32_F".\n", seqno, ackno));
+}
+
+/**
+ * Requeue all unacked segments for retransmission
+ *
+ * Called by tcp_slowtmr() for slow retransmission.
+ *
+ * @param pcb the tcp_pcb for which to re-enqueue all unacked segments
+ */
+void
+tcp_rexmit_rto(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *seg;
+
+ if (pcb->unacked == NULL) {
+ return;
+ }
+
+ /* Move all unacked segments to the head of the unsent queue */
+ for (seg = pcb->unacked; seg->next != NULL; seg = seg->next);
+ /* concatenate unsent queue after unacked queue */
+ seg->next = pcb->unsent;
+ /* unsent queue is the concatenated queue (of unacked, unsent) */
+ pcb->unsent = pcb->unacked;
+ /* unacked queue is now empty */
+ pcb->unacked = NULL;
+
+ /* increment number of retransmissions */
+ ++pcb->nrtx;
+
+ /* Don't take any RTT measurements after retransmitting. */
+ pcb->rttest = 0;
+
+ /* Do the actual retransmission */
+ tcp_output(pcb);
+}
+
+/**
+ * Requeue the first unacked segment for retransmission
+ *
+ * Called by tcp_receive() for fast retramsmit.
+ *
+ * @param pcb the tcp_pcb for which to retransmit the first unacked segment
+ */
+void
+tcp_rexmit(struct tcp_pcb *pcb)
+{
+ struct tcp_seg *seg;
+ struct tcp_seg **cur_seg;
+
+ if (pcb->unacked == NULL) {
+ return;
+ }
+
+ /* Move the first unacked segment to the unsent queue */
+ /* Keep the unsent queue sorted. */
+ seg = pcb->unacked;
+ pcb->unacked = seg->next;
+
+ cur_seg = &(pcb->unsent);
+ while (*cur_seg &&
+ TCP_SEQ_LT(ntohl((*cur_seg)->tcphdr->seqno), ntohl(seg->tcphdr->seqno))) {
+ cur_seg = &((*cur_seg)->next );
+ }
+ seg->next = *cur_seg;
+ *cur_seg = seg;
+
+ ++pcb->nrtx;
+
+ /* Don't take any rtt measurements after retransmitting. */
+ pcb->rttest = 0;
+
+ /* Do the actual retransmission. */
+ snmp_inc_tcpretranssegs();
+ tcp_output(pcb);
+}
+
+
+/**
+ * Handle retransmission after three dupacks received
+ *
+ * @param pcb the tcp_pcb for which to retransmit the first unacked segment
+ */
+void
+tcp_rexmit_fast(struct tcp_pcb *pcb)
+{
+ if (pcb->unacked != NULL && !(pcb->flags & TF_INFR)) {
+ /* This is fast retransmit. Retransmit the first unacked segment. */
+ LWIP_DEBUGF(TCP_FR_DEBUG,
+ ("tcp_receive: dupacks %"U16_F" (%"U32_F
+ "), fast retransmit %"U32_F"\n",
+ (u16_t)pcb->dupacks, pcb->lastack,
+ ntohl(pcb->unacked->tcphdr->seqno)));
+ tcp_rexmit(pcb);
+
+ /* Set ssthresh to half of the minimum of the current
+ * cwnd and the advertised window */
+ if (pcb->cwnd > pcb->snd_wnd)
+ pcb->ssthresh = pcb->snd_wnd / 2;
+ else
+ pcb->ssthresh = pcb->cwnd / 2;
+
+ /* The minimum value for ssthresh should be 2 MSS */
+ if (pcb->ssthresh < 2*pcb->mss) {
+ LWIP_DEBUGF(TCP_FR_DEBUG,
+ ("tcp_receive: The minimum value for ssthresh %"U16_F
+ " should be min 2 mss %"U16_F"...\n",
+ pcb->ssthresh, 2*pcb->mss));
+ pcb->ssthresh = 2*pcb->mss;
+ }
+
+ pcb->cwnd = pcb->ssthresh + 3 * pcb->mss;
+ pcb->flags |= TF_INFR;
+ }
+}
+
+
+/**
+ * Send keepalive packets to keep a connection active although
+ * no data is sent over it.
+ *
+ * Called by tcp_slowtmr()
+ *
+ * @param pcb the tcp_pcb for which to send a keepalive packet
+ */
+void
+tcp_keepalive(struct tcp_pcb *pcb)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: sending KEEPALIVE probe to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
+ ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
+ ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip)));
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: tcp_ticks %"U32_F" pcb->tmr %"U32_F" pcb->keep_cnt_sent %"U16_F"\n",
+ tcp_ticks, pcb->tmr, pcb->keep_cnt_sent));
+
+ p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM);
+
+ if(p == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("tcp_keepalive: could not allocate memory for pbuf\n"));
+ return;
+ }
+ LWIP_ASSERT("check that first pbuf can hold struct tcp_hdr",
+ (p->len >= sizeof(struct tcp_hdr)));
+
+ tcphdr = tcp_output_set_header(pcb, p, 0, htonl(pcb->snd_nxt - 1));
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, &pcb->local_ip, &pcb->remote_ip,
+ IP_PROTO_TCP, p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+
+ /* Send output to IP */
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP,
+ &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+
+ pbuf_free(p);
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: seqno %"U32_F" ackno %"U32_F".\n",
+ pcb->snd_nxt - 1, pcb->rcv_nxt));
+}
+
+
+/**
+ * Send persist timer zero-window probes to keep a connection active
+ * when a window update is lost.
+ *
+ * Called by tcp_slowtmr()
+ *
+ * @param pcb the tcp_pcb for which to send a zero-window probe packet
+ */
+void
+tcp_zero_window_probe(struct tcp_pcb *pcb)
+{
+ struct pbuf *p;
+ struct tcp_hdr *tcphdr;
+ struct tcp_seg *seg;
+ u16_t len;
+ u8_t is_fin;
+
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("tcp_zero_window_probe: sending ZERO WINDOW probe to %"
+ U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
+ ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
+ ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip)));
+
+ LWIP_DEBUGF(TCP_DEBUG,
+ ("tcp_zero_window_probe: tcp_ticks %"U32_F
+ " pcb->tmr %"U32_F" pcb->keep_cnt_sent %"U16_F"\n",
+ tcp_ticks, pcb->tmr, pcb->keep_cnt_sent));
+
+ seg = pcb->unacked;
+
+ if(seg == NULL)
+ seg = pcb->unsent;
+
+ if(seg == NULL)
+ return;
+
+ is_fin = ((TCPH_FLAGS(seg->tcphdr) & TCP_FIN) != 0) && (seg->len == 0);
+ len = is_fin ? TCP_HLEN : TCP_HLEN + 1;
+
+ p = pbuf_alloc(PBUF_IP, len, PBUF_RAM);
+ if(p == NULL) {
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: no memory for pbuf\n"));
+ return;
+ }
+ LWIP_ASSERT("check that first pbuf can hold struct tcp_hdr",
+ (p->len >= sizeof(struct tcp_hdr)));
+
+ tcphdr = tcp_output_set_header(pcb, p, 0, seg->tcphdr->seqno);
+
+ if (is_fin) {
+ /* FIN segment, no data */
+ TCPH_FLAGS_SET(tcphdr, TCP_ACK | TCP_FIN);
+ } else {
+ /* Data segment, copy in one byte from the head of the unacked queue */
+ *((char *)p->payload + sizeof(struct tcp_hdr)) = *(char *)seg->dataptr;
+ }
+
+#if CHECKSUM_GEN_TCP
+ tcphdr->chksum = inet_chksum_pseudo(p, &pcb->local_ip, &pcb->remote_ip,
+ IP_PROTO_TCP, p->tot_len);
+#endif
+ TCP_STATS_INC(tcp.xmit);
+
+ /* Send output to IP */
+#if LWIP_NETIF_HWADDRHINT
+ ip_output_hinted(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP,
+ &(pcb->addr_hint));
+#else /* LWIP_NETIF_HWADDRHINT*/
+ ip_output(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP);
+#endif /* LWIP_NETIF_HWADDRHINT*/
+
+ pbuf_free(p);
+
+ LWIP_DEBUGF(TCP_DEBUG, ("tcp_zero_window_probe: seqno %"U32_F
+ " ackno %"U32_F".\n",
+ pcb->snd_nxt - 1, pcb->rcv_nxt));
+}
+#endif /* LWIP_TCP */