[lwip-devel] [bug #26251] RST process in TIME_WAIT TCP state

[Simon Goldschmidt]

Follow-up Comment #14, bug #26251 (project lwip):

A relatively complete implementation of RFC 1337 vs. RFC 793 (chapter 3.9
Event Processing - Segment Arrives) is below. This is relatively complete (the
'acceptable' check is not fully made - only for SYN - but I guess it's OK like
that), but the code is also biger than before:

/* RFC 1337: in TIME_WAIT, ignore RST and ACK FINs + any 'acceptable'
segments */
/* RFC 793 3.9 Event Processing - Segment Arrives:
 * - first check sequence number - we skip that one in TIME_WAIT (always
 *   acceptable since we only send ACKs)
 * - second check the RST bit (... return) */
if (flags & TCP_RST)  {
  return ERR_OK;
}
/* - fourth, check the SYN bit, */
if (flags & TCP_SYN) {
  /* If an incoming segment is not acceptable, an acknowledgment
     should be sent in reply */
  if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt, pcb->rcv_nxt+pcb->rcv_wnd)) {
    /* If the SYN is in the window it is an error, send a reset */
    /* @todo: send RST */
    tcp_rst(ackno, seqno + tcplen, &(iphdr->dest), &(iphdr->src),
      tcphdr->dest, tcphdr->src);
    return ERR_OK;
  }
} else if (flags & TCP_FIN) {
  /* - eighth, check the FIN bit: Remain in the TIME-WAIT state.
       Restart the 2 MSL time-wait timeout.*/
  pcb->tmr = tcp_ticks;
}

if ((tcplen > 0))  {
  /* Acknowledge data, FIN or out-of-window SYN */
  pcb->flags |= TF_ACK_NOW;
  return tcp_output(pcb);
}
return ERR_OK;

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