tcp_in.c

lm3s下lwip的udp

          LWIP_ASSERT("pbuf_header failed", 0);
        }
      }
      /* KJM following line changed to use p->payload rather than inseg->p->payload
         to fix bug #9076 */
      inseg.dataptr = p->payload;
      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_ann_wnd - 1)){
      if (pcb->rcv_nxt == seqno) {
        accepted_inseq = 1; 
        /* 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. */
#if TCP_QUEUE_OOSEQ
        if (pcb->ooseq != NULL &&
                TCP_SEQ_LEQ(pcb->ooseq->tcphdr->seqno, seqno + inseg.len)) {
          if (pcb->ooseq->len > 0) {
            /* We have to trim the second edge of the incoming
               segment. */
            inseg.len = (u16_t)(pcb->ooseq->tcphdr->seqno - seqno);
            pbuf_realloc(inseg.p, inseg.len);
          } else {
            /* does the ooseq segment contain only flags that are in inseg also? */
            if ((TCPH_FLAGS(inseg.tcphdr) & (TCP_FIN|TCP_SYN)) ==
                (TCPH_FLAGS(pcb->ooseq->tcphdr) & (TCP_FIN|TCP_SYN))) {
              struct tcp_seg *old_ooseq = pcb->ooseq;
              pcb->ooseq = pcb->ooseq->next;
              memp_free(MEMP_TCP_SEG, old_ooseq);
            }
          }
        }
#endif /* TCP_QUEUE_OOSEQ */

        tcplen = TCP_TCPLEN(&inseg);

        /* First received FIN will be ACKed +1, on any successive (duplicate)
         * FINs we are already in CLOSE_WAIT and have already done +1.
         */
        if (pcb->state != CLOSE_WAIT) {
          pcb->rcv_nxt += tcplen;
        }

        /* Update the receiver's (our) window. */
        if (pcb->rcv_wnd < tcplen) {
          pcb->rcv_wnd = 0;
        } else {
          pcb->rcv_wnd -= tcplen;
        }

        if (pcb->rcv_ann_wnd < tcplen) {
          pcb->rcv_ann_wnd = 0;
        } else {
          pcb->rcv_ann_wnd -= tcplen;
        }

        /* 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
           is 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);
          if (pcb->rcv_wnd < TCP_TCPLEN(cseg)) {
            pcb->rcv_wnd = 0;
          } else {
            pcb->rcv_wnd -= TCP_TCPLEN(cseg);
          }
          if (pcb->rcv_ann_wnd < TCP_TCPLEN(cseg)) {
            pcb->rcv_ann_wnd = 0;
          } else {
            pcb->rcv_ann_wnd -= TCP_TCPLEN(cseg);
          }

          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_ack_now(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 the old segment with the new
                   one. */
                cseg = tcp_seg_copy(&inseg);
                if (cseg != NULL) {
                  cseg->next = next->next;
                  if (prev != NULL) {
                    prev->next = cseg;
                  } else {
                    pcb->ooseq = cseg;
                  }
                }
                tcp_seg_free(next);
                if (cseg->next != NULL) {
                  next = cseg->next;
                  if (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);
                  }
                }
                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. */

                  if (TCP_SEQ_GT(seqno + inseg.len, next->tcphdr->seqno)) {
                    /* We need to trim the incoming segment. */
                    inseg.len = (u16_t)(next->tcphdr->seqno - seqno);
                    pbuf_realloc(inseg.p, inseg.len);
                  }
                  cseg = tcp_seg_copy(&inseg);
                  if (cseg != NULL) {
                    cseg->next = next;
                    pcb->ooseq = cseg;
                  }
                  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 and insert the
                   incoming segment and trim the previous segment, if
                   needed. */
                if (TCP_SEQ_GT(seqno + inseg.len, next->tcphdr->seqno)) {
                  /* We need to trim the incoming segment. */
                  inseg.len = (u16_t)(next->tcphdr->seqno - seqno);
                  pbuf_realloc(inseg.p, inseg.len);
                }

                cseg = tcp_seg_copy(&inseg);
                if (cseg != NULL) {
                  cseg->next = next;
                  prev->next = cseg;
                  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);
                  }
                }
                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)) {
                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);
                  }
                }
                break;
              }
            }
            prev = next;
          }
        }
#endif /* TCP_QUEUE_OOSEQ */

      }
    } else {
      if(!TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, 
                          pcb->rcv_nxt + pcb->rcv_ann_wnd-1)){
        tcp_ack_now(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);
    }
  }
  return accepted_inseq;
}

/**
 * Parses the options contained in the incoming segment. (Code taken
 * from uIP with only small changes.)
 *
 * 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)
{
  u8_t c;
  u8_t *opts, opt;
  u16_t mss;

  opts = (u8_t *)tcphdr + TCP_HLEN;

  /* Parse the TCP MSS option, if present. */
  if(TCPH_HDRLEN(tcphdr) > 0x5) {
    for(c = 0; c < (TCPH_HDRLEN(tcphdr) - 5) << 2 ;) {
      opt = opts[c];
      if (opt == 0x00) {
        /* End of options. */
        break;
      } else if (opt == 0x01) {
        ++c;
        /* NOP option. */
      } else if (opt == 0x02 &&
        opts[c + 1] == 0x04) {
        /* An MSS option with the right option length. */
        mss = (opts[c + 2] << 8) | opts[c + 3];
        pcb->mss = mss > TCP_MSS? TCP_MSS: mss;

        /* And we are done processing options. */
        break;
      } else {
        if (opts[c + 1] == 0) {
          /* If the length field is zero, the options are malformed
             and we don't process them further. */
          break;
        }
        /* All other options have a length field, so that we easily
           can skip past them. */
        c += opts[c + 1];
      }
    }
  }
}

#endif /* LWIP_TCP */