/**
 * @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 = 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 = 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 = 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);
  }