tcp_in.c

基于STM32F107的UDP服务器程序

            /* 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
        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;
              memp_free(MEMP_TCP_SEG, old_ooseq);
            }               
          } else if (TCP_SEQ_LEQ(pcb->ooseq->tcphdr->seqno, seqno + tcplen)) {
            if (pcb->ooseq->len > 0) {
              /* We have to trim the second edge of the incoming segment. */
              LWIP_ASSERT("tcp_receive: trimmed segment would have zero length\n",
                          TCP_SEQ_GT(pcb->ooseq->tcphdr->seqno, seqno));
              /* FIN in inseg already handled by dropping whole ooseq queue */
              inseg.len = (u16_t)(pcb->ooseq->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) == pcb->ooseq->tcphdr->seqno);
            } 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 */

        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
           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);
          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_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 {
      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. 
 *
 * 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 */