tcp4input.c

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        TcpClearAllTimer (Tcb);

        if (Tcb->TimeWaitTimeout != 0) {

          TcpSetTimer (Tcb, TCP_TIMER_2MSL, Tcb->TimeWaitTimeout);
        } else {

          TCP4_DEBUG_WARN (("Connection closed immediately "
            "because app disables TIME_WAIT timer for %x\n", Tcb));

          TcpSendAck (Tcb);
          TcpClose (Tcb);
        }
        break;

      case TCP_CLOSE_WAIT:
      case TCP_CLOSING:
      case TCP_LAST_ACK:
      case TCP_TIME_WAIT:
        //
        // The peer sends to us junk FIN byte. Discard 
        // the buffer then reset the connection
        //
        NetbufFree (Nbuf);
        return -1;
        break;
      }

      TCP_SET_FLG (Tcb->CtrlFlag, TCP_CTRL_ACK_NOW);

      Seg->End--;
    }

    //
    // Don't delay the ack if PUSH flag is on.
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_PSH)) {

      TCP_SET_FLG (Tcb->CtrlFlag, TCP_CTRL_ACK_NOW);
    }

    if (Nbuf->TotalSize) {
      Urgent = 0;

      if (TCP_FLG_ON (Tcb->CtrlFlag, TCP_CTRL_RCVD_URG) &&
          TCP_SEQ_LEQ (Seg->Seq, Tcb->RcvUp)) {

        if (TCP_SEQ_LEQ (Seg->End, Tcb->RcvUp)) {
          Urgent = Nbuf->TotalSize;
        } else {
          Urgent = TCP_SUB_SEQ (Tcb->RcvUp, Seg->Seq) + 1;
        }
      }

      SockDataRcvd (Tcb->Sk, Nbuf, Urgent);
    }

    if (TCP_FIN_RCVD (Tcb->State)) {

      SockNoMoreData (Tcb->Sk);
    }

    NetbufFree (Nbuf);
  }

  return 0;
}

VOID
TcpQueueData (
  IN TCP_CB  *Tcb,
  IN NET_BUF *Nbuf
  )
/*++

Routine Description:

  Store the data into the reassemble queue.

Arguments:

  Tcb   - Pointer to the TCP_CB of this TCP instance.
  Nbuf  - Pointer to the buffer containing the data to be queued.

Returns:

  None.

--*/
{
  TCP_SEG         *Seg;
  NET_LIST_ENTRY  *Head;
  NET_LIST_ENTRY  *Prev;
  NET_LIST_ENTRY  *Cur;
  NET_BUF         *Node;

  ASSERT (Tcb && Nbuf && (Nbuf->Tcp == NULL));

  NET_GET_REF (Nbuf);

  Seg   = TCPSEG_NETBUF (Nbuf);
  Head  = &Tcb->RcvQue;

  //
  // Fast path to process normal case. That is,
  // no out-of-order segments are received.
  //
  if (NetListIsEmpty (Head)) {

    NetListInsertTail (Head, &Nbuf->List);
    return ;
  }

  //
  // Find the point to insert the buffer
  //
  for (Prev = Head, Cur = Head->ForwardLink;
      Cur != Head;
      Prev = Cur, Cur = Cur->ForwardLink) {

    Node = NET_LIST_USER_STRUCT (Cur, NET_BUF, List);

    if (TCP_SEQ_LT (Seg->Seq, TCPSEG_NETBUF (Node)->Seq)) {
      break;
    }
  }

  //
  // Check whether the current segment overlaps with the
  // previous segment.
  //
  if (Prev != Head) {
    Node = NET_LIST_USER_STRUCT (Prev, NET_BUF, List);

    if (TCP_SEQ_LT (Seg->Seq, TCPSEG_NETBUF (Node)->End)) {

      if (TCP_SEQ_LEQ (Seg->End, TCPSEG_NETBUF (Node)->End)) {

        NetbufFree (Nbuf);
        return ;
      }

      TcpTrimSegment (Nbuf, TCPSEG_NETBUF (Node)->End, Seg->End);
    }
  }

  NetListInsertHead (Prev, &Nbuf->List);

  TCP_SET_FLG (Tcb->CtrlFlag, TCP_CTRL_ACK_NOW);

  //
  // Check the segments after the insert point.
  //
  while (Cur != Head) {
    Node = NET_LIST_USER_STRUCT (Cur, NET_BUF, List);

    if (TCP_SEQ_LEQ (TCPSEG_NETBUF (Node)->End, Seg->End)) {

      Cur = Cur->ForwardLink;

      NetListRemoveEntry (&Node->List);
      NetbufFree (Node);
      continue;
    }

    if (TCP_SEQ_LT (TCPSEG_NETBUF (Node)->Seq, Seg->End)) {

      if (TCP_SEQ_LEQ (TCPSEG_NETBUF (Node)->Seq, Seg->Seq)) {

        NetListRemoveEntry (&Nbuf->List);
        NetbufFree (Nbuf);
        return ;
      }

      TcpTrimSegment (Nbuf, Seg->Seq, TCPSEG_NETBUF (Node)->Seq);
      break;
    }

    Cur = Cur->ForwardLink;
  }
}

VOID
TcpAdjustSndQue (
  IN TCP_CB    *Tcb,
  IN TCP_SEQNO Ack
  )
/*++

Routine Description:

  Ajust the send queue or the retransmit queue.

Arguments:

  Tcb - Pointer to the TCP_CB of this TCP instance.
  Ack - The acknowledge seuqence number of the received segment.

Returns:

  None.

--*/
{
  NET_LIST_ENTRY  *Head;
  NET_LIST_ENTRY  *Cur;
  NET_BUF         *Node;
  TCP_SEG         *Seg;

  Head  = &Tcb->SndQue;
  Cur   = Head->ForwardLink;

  while (Cur != Head) {
    Node  = NET_LIST_USER_STRUCT (Cur, NET_BUF, List);
    Seg   = TCPSEG_NETBUF (Node);

    if (TCP_SEQ_GEQ (Seg->Seq, Ack)) {
      break;
    }

    //
    // Remove completely ACKed segments
    //
    if (TCP_SEQ_LEQ (Seg->End, Ack)) {
      Cur = Cur->ForwardLink;

      NetListRemoveEntry (&Node->List);
      NetbufFree (Node);
      continue;
    }

    TcpTrimSegment (Node, Ack, Seg->End);
    break;
  }
}

INTN
TcpInput (
  IN NET_BUF *Nbuf,
  IN UINT32  Src,
  IN UINT32  Dst
  )
/*++

Routine Description:

  Process the received TCP segments.

Arguments:

  Nbuf  - Buffer that contains received TCP segment without IP header.
  Src   - Source address of the segment, or the peer's IP address.
  Dst   - Destination address of the segment, or the local end's IP address.

Returns:

  0     - Segment is processed successfully. It is either accepted or discarded.
          But no connection is reset by the segment.
  -1    - A connection is reset by the segment.

--*/
{
  TCP_CB      *Tcb;
  TCP_CB      *Parent;
  TCP_OPTION  Option;
  TCP_HEAD    *Head;
  INT32       Len;
  TCP_SEG     *Seg;
  TCP_SEQNO   Right;
  TCP_SEQNO   Urg;

  NET_CHECK_SIGNATURE (Nbuf, NET_BUF_SIGNATURE);

  Parent  = NULL;
  Tcb     = NULL;

  Head    = (TCP_HEAD *) NetbufGetByte (Nbuf, 0, NULL);
  Len     = Nbuf->TotalSize - (Head->HeadLen << 2);

  if ((Head->HeadLen < 5) || (Len < 0) ||
      TcpChecksum (Nbuf, NetPseudoHeadChecksum (Src, Dst, 6, 0))) {

    TCP4_DEBUG_TRACE (("TcpInput: received an mal-formated packet\n"));
    goto DISCARD;
  }

  if (TCP_FLG_ON (Head->Flag, TCP_FLG_SYN)) {
    Len++;
  }

  if (TCP_FLG_ON (Head->Flag, TCP_FLG_FIN)) {
    Len++;
  }

  Tcb = TcpLocateTcb (
          Head->DstPort,
          Dst,
          Head->SrcPort,
          Src,
          (BOOLEAN) TCP_FLG_ON (Head->Flag, TCP_FLG_SYN)
          );

  if ((Tcb == NULL) || (Tcb->State == TCP_CLOSED)) {
    TCP4_DEBUG_TRACE (("TcpInput: send reset because no TCB find\n"));

    Tcb = NULL;
    goto SEND_RESET;
  }

  Seg = TcpFormatNetbuf (Tcb, Nbuf);

  //
  // RFC1122 recommended reaction to illegal option
  // (in fact, an illegal option length) is reset.
  //
  if (TcpParseOption (Nbuf->Tcp, &Option) == -1) {
    TCP4_DEBUG_ERROR (("TcpInput: reset the peer because"
      " of mal-format option for Tcb %x\n", Tcb));

    goto SEND_RESET;
  }

  //
  // From now on, the segment is headless
  //
  NetbufTrim (Nbuf, (Head->HeadLen << 2), NET_BUF_HEAD);
  Nbuf->Tcp = NULL;

  //
  // TODO: add fast path process here
  //

  //
  // Process the segment in LISTEN state.
  //
  if (Tcb->State == TCP_LISTEN) {
    //
    // First step: Check RST
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_RST)) {
      TCP4_DEBUG_WARN (("TcpInput: discard a reset segment "
        "for TCB %x in listening\n", Tcb));

      goto DISCARD;
    }

    //
    // Second step: Check ACK.
    // Any ACK sent to TCP in LISTEN is reseted.
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_ACK)) {
      TCP4_DEBUG_WARN (("TcpInput: send reset because of"
        " segment with ACK for TCB %x in listening\n", Tcb));

      goto SEND_RESET;
    }

    //
    // Third step: Check SYN
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_SYN)) {
      //
      // create a child TCB to handle the data
      //
      Parent  = Tcb;

      Tcb     = TcpCloneTcb (Parent);
      if (Tcb == NULL) {
        TCP4_DEBUG_ERROR (("TcpInput: discard a segment because"
          "failed to clone a child for TCB%x\n", Tcb));

        goto DISCARD;
      }

      TCP4_DEBUG_TRACE (("TcpInput: create a child for TCB %x"
        " in listening\n", Tcb));

      //
      // init the TCB structure
      //
      Tcb->LocalEnd.Ip    = Dst;
      Tcb->LocalEnd.Port  = Head->DstPort;
      Tcb->RemoteEnd.Ip   = Src;
      Tcb->RemoteEnd.Port = Head->SrcPort;

      TcpInitTcbLocal (Tcb);
      TcpInitTcbPeer (Tcb, Seg, &Option);

      TcpSetState (Tcb, TCP_SYN_RCVD);
      TcpSetTimer (Tcb, TCP_TIMER_CONNECT, Tcb->ConnectTimeout);
      TcpTrimInWnd (Tcb, Nbuf);

      goto StepSix;
    }

    goto DISCARD;

  } else if (Tcb->State == TCP_SYN_SENT) {
    //
    // First step: Check ACK bit
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_ACK) && (Seg->Ack != Tcb->Iss + 1)) {
 
      TCP4_DEBUG_WARN (("TcpInput: send reset because of "
        "wrong ACK received for TCB %x in SYN_SENT\n", Tcb));

      goto SEND_RESET;
    }

    //
    // Second step: Check RST bit
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_RST)) {

      if (TCP_FLG_ON (Seg->Flag, TCP_FLG_ACK)) {

        TCP4_DEBUG_WARN (("TcpInput: connection reset by"
          " peer for TCB%x in SYN_SENT\n", Tcb));

        SOCK_ERROR (Tcb->Sk, EFI_CONNECTION_RESET);
        goto DROP_CONNECTION;
      } else {

        TCP4_DEBUG_WARN (("TcpInput: discard a reset segment "
          "because of no ACK for TCB%x in SYN_SENT\n", Tcb));

        goto DISCARD;
      }
    }

    //
    // Third step: Check security and precedence. Skipped
    //

    //
    // Fourth step: Check SYN. Pay attention to sitimulatous open
    //
    if (TCP_FLG_ON (Seg->Flag, TCP_FLG_SYN)) {

      TcpInitTcbPeer (Tcb, Seg, &Option);

      if (TCP_FLG_ON (Seg->Flag, TCP_FLG_ACK)) {

        Tcb->SndUna = Seg->Ack;
      }

      TcpClearTimer (Tcb, TCP_TIMER_REXMIT);

      if (TCP_SEQ_GT (Tcb->SndUna, Tcb->Iss)) {

        TcpSetState (Tcb, TCP_ESTABLISHED);

        TcpClearTimer (Tcb, TCP_TIMER_CONNECT);
        TcpDeliverData (Tcb);

        if ((Tcb->CongestState == TCP_CONGEST_OPEN) && 
            TCP_FLG_ON (Tcb->CtrlFlag, TCP_CTRL_RTT_ON)) {

          TcpComputeRtt (Tcb, Tcb->RttMeasure);
          TCP_CLEAR_FLG (Tcb->CtrlFlag, TCP_CTRL_RTT_ON);
        }

        TcpTrimInWnd (Tcb, Nbuf);

        TCP_SET_FLG (Tcb->CtrlFlag, TCP_CTRL_ACK_NOW);

        TCP4_DEBUG_TRACE (("TcpInput: connection established"
          " for TCB %x in SYN_SENT\n", Tcb));

        goto StepSix;
      } else {
        //
        // Received a SYN segment without ACK, simultanous open. 
        //
        TcpSetState (Tcb, TCP_SYN_RCVD);

        ASSERT (Tcb->SndNxt == Tcb->Iss + 1);
        TcpAdjustSndQue (Tcb, Tcb->SndNxt);

        TcpTrimInWnd (Tcb, Nbuf);

        TCP4_DEBUG_WARN (("TcpInput: simultanous open "
          "for TCB %x in SYN_SENT\n", Tcb));

        goto StepSix;
      }
    }

    goto DISCARD;
  }

  //
  // Process segment in SYN_RCVD or TCP_CONNECTED states
  //

  //
  // First step: Check whether SEG.SEQ is acceptable
  //
  if (!TcpSeqAcceptable (Tcb, Seg)) {
    TCP4_DEBUG_WARN (("TcpInput: sequence acceptance"
      " test failed for segment of TCB %x\n", Tcb));

    if (!TCP_FLG_ON (Seg->Flag, TCP_FLG_RST)) {
      TcpSendAck (Tcb);
    }

    goto DISCARD;
  }

  if ((TCP_SEQ_LT (Seg->Seq, Tcb->RcvWl2)) &&
      (Tcb->RcvWl2 == Seg->End) &&
      !TCP_FLG_ON (Seg->Flag, TCP_FLG_SYN | TCP_FLG_FIN)) {

    TCP_SET_FLG (Tcb->CtrlFlag, TCP_CTRL_ACK_NOW);
  }