tcp_out.c

lWIP是TCPIP的协议的源代码。采用的是最新LWIP0.6.4版本。为了得到最佳性能

/**
 * @file
 *
 * Transmission Control Protocol, outgoing traffic
 */
/*
 * Copyright (c) 2001-2003 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 <[e-mail]>
 *
 */

/*-----------------------------------------------------------------------------------*/
/* tcp_output.c
 *
 * The output functions of TCP.
 *
 */
/*-----------------------------------------------------------------------------------*/


#include "../include/tcpincludes.h"

#if LWIP_TCP

/* Forward declarations.*/
static void tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb);


/*-----------------------------------------------------------------------------------*/
err_t
tcp_send_ctrl(struct tcp_pcb *pcb, u8_t flags)
{
  return tcp_enqueue(pcb, NULL, 0, flags, 1, NULL, 0);

}
/*-----------------------------------------------------------------------------------*/
err_t
tcp_write(struct tcp_pcb *pcb, const void *arg, u16_t len, u8_t copy)
{
  LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_write(pcb=%p, arg=%p, len=%u, copy=%d)\n", (void *)pcb,
    arg, len, (unsigned int)copy));
  if (pcb->state == SYN_SENT ||
     pcb->state == SYN_RCVD ||
     pcb->state == ESTABLISHED ||
     pcb->state == CLOSE_WAIT) {
    if (len > 0) {
      return tcp_enqueue(pcb, (void *)arg, len, 0, copy, NULL, 0);
    }
    return ERR_OK;
  } else {
    LWIP_DEBUGF(TCP_OUTPUT_DEBUG | DBG_STATE | 3, ("tcp_write() called in invalid state\n"));
    return ERR_CONN;
  }
}
/*-----------------------------------------------------------------------------------*/
err_t
tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len,
      u8_t flags, u8_t copy,
            u8_t *optdata, u8_t optlen)
{
  struct pbuf *p;
  struct tcp_seg *seg, *useg, *queue;
  u32_t left, seqno;
  u16_t seglen;
  void *ptr;
  u8_t queuelen;

  LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_enqueue(pcb=%p, arg=%p, len=%u, flags=%x, copy=%u)\n",
    (void *)pcb, arg, len, (unsigned int)flags, (unsigned int)copy));
  left = len;
  ptr = arg;
  /* fail on too much data */
  if (len > pcb->snd_buf) {
    LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too much data (len=%u > snd_buf=%u)\n", len, pcb->snd_buf));
    return ERR_MEM;
  }

  /* seqno will be the sequence number of the first segment enqueued
   * by the call to this function. */
  seqno = pcb->snd_lbb;

  queue = NULL;
  LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: queuelen: %u\n", (unsigned int)pcb->snd_queuelen));

  /* Check if the queue length exceeds the configured maximum queue
   * length. If so, we return an error. */
  queuelen = pcb->snd_queuelen;
  if (queuelen >= TCP_SND_QUEUELEN) {
    LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too long queue %u (max %u)\n", queuelen, TCP_SND_QUEUELEN));
    goto memerr;
  }

  if (pcb->snd_queuelen != 0) {
    LWIP_ASSERT("tcp_enqueue: valid queue length", pcb->unacked != NULL ||
    pcb->unsent != NULL);
  }

  seg = NULL;
  seglen = 0;

  /* First, break up the data into segments and tuck them together in
   * the local "queue" variable. */
  while (queue == NULL || left > 0) {

    /* The segment length should be the MSS if the data to be enqueued
     * is larger than the MSS. */
    seglen = left > pcb->mss? pcb->mss: left;

    /* Allocate memory for tcp_seg, and fill in fields. */
    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;

    if (queue == NULL) {
      queue = seg;
    }
    else {
      /* Attach the segment to the end of the queued segments. */
      for (useg = queue; useg->next != NULL; useg = useg->next);
      useg->next = 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
     * optdata is != NULL, we have options instead of data. */
    if (optdata != NULL) {
      if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, optlen, PBUF_RAM)) == NULL) {
        goto memerr;
      }
      ++queuelen;
      seg->dataptr = seg->p->payload;
    }
    else if (copy) {
      if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, seglen, PBUF_RAM)) == NULL) {
        LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue : could not allocate memory for pbuf copy size %u\n", seglen));
        goto memerr;
      }
      ++queuelen;
      if (arg != NULL) {
        memcpy(seg->p->payload, ptr, seglen);
      }
      seg->dataptr = seg->p->payload;
    }
    /* do not copy data */
    else {

      /* first, 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 ((p = pbuf_alloc(PBUF_TRANSPORT, seglen, PBUF_ROM)) == NULL) {
        LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: could not allocate memory for zero-copy pbuf\n"));
        goto memerr;
      }
      ++queuelen;
      p->payload = ptr;
      seg->dataptr = ptr;

      /* Second, allocate a pbuf for the headers. */
      if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, 0, PBUF_RAM)) == NULL) {
        /* If allocation fails, we have to deallocate the data pbuf as
         * well. */
        pbuf_free(p);
        LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: could not allocate memory for header pbuf\n"));
        goto memerr;
      }
      ++queuelen;

      /* Chain the headers and data pbufs together. */
      pbuf_chain(seg->p, p);
      pbuf_free(p);
      p = NULL;
    }

    /* Now that there are more segments queued, we check again if the
    length of the queue exceeds the configured maximum. */
    if (queuelen > TCP_SND_QUEUELEN) {
      LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: queue too long %u (%u)\n", queuelen, TCP_SND_QUEUELEN));
      goto memerr;
    }

    seg->len = seglen;
#if 0 /* Was commented out. TODO: can someone say why this is here? */
    if ((flags & TCP_SYN) || (flags & TCP_FIN)) {
      ++seg->len;
    }
#endif
    /* 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"));

#ifdef TCP_STATS
      ++lwip_stats.tcp.err;
#endif /* TCP_STATS */
      goto memerr;
    }
    seg->tcphdr = 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 */

    /* Copy the options into the header, if they are present. */
    if (optdata == NULL) {
      TCPH_OFFSET_SET(seg->tcphdr, 5 << 4);
    }
    else {
      TCPH_OFFSET_SET(seg->tcphdr, (5 + optlen / 4) << 4);
      /* Copy options into data portion of segment.
       Options can thus only be sent in non data carrying
       segments such as SYN|ACK. */
      memcpy(seg->dataptr, optdata, optlen);
    }
    LWIP_DEBUGF(TCP_OUTPUT_DEBUG | DBG_TRACE, ("tcp_enqueue: queueing %lu:%lu (0x%x)\n",
      ntohl(seg->tcphdr->seqno),
      ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg),
      flags));

    left -= seglen;
    seqno += seglen;
    ptr = (void *)((char *)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);
  }

  /* 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)) &&
    useg->len + queue->len <= pcb->mss) {
    /* Remove TCP header from first segment. */
    pbuf_header(queue->p, -TCP_HLEN);
    pbuf_chain(useg->p, queue->p);
    /* Free buffer which was merged. Note that the previous pbuf_chain call
     * will have incremented the ref count, so here the ref count will still
     * be 1 for the 1 pointer still being used on this buffer. */
    pbuf_free(queue->p);
    useg->len += queue->len;
    useg->next = queue->next;

    LWIP_DEBUGF(TCP_OUTPUT_DEBUG | DBG_TRACE | DBG_STATE, ("tcp_enqueue: chaining, new len %u\n", useg->len));
    if (seg == queue) {
      seg = NULL;
    }
    memp_free(MEMP_TCP_SEG, queue);
  }
  else {
    if (useg == NULL) {
      pcb->unsent = queue;

    }
    else {