[lwip-devel] [bug #25622] Lack of return code checks in tcp_listen_input can cause incoming connections to become blocked.

[Roman Trunov]

Follow-up Comment #4, bug #25622 (project lwip):

Look like I found more correct and generic solution by adding additional
logic to tcp_process(). If possible, please try this in your setup since you
can reproduce problem easily. Of course your patch must be removed first.

diff -u -r1.5 tcp_in.c
--- tcp_in.c    10 Mar 2009 14:05:53 -0000      1.5
+++ tcp_in.c    12 Mar 2009 08:54:52 -0000
@@ -624,6 +624,15 @@
     }
     break;
   case SYN_RCVD:
+    if ((flags & TCP_SYN) && !(flags & TCP_ACK)) {
+      /* Connection request repeated, may be our ACK was lost. Send another
one. */
+      u32_t optdata;
+      /* Build an MSS option. */
+      optdata = TCP_BUILD_MSS_OPTION();
+      /* Send a SYN|ACK together with the MSS option. */
+      tcp_enqueue(pcb, NULL, 0, TCP_SYN | TCP_ACK, 0, (u8_t *)&optdata, 4);
+      break;
+    }
     if (flags & TCP_ACK &&
        !(flags & TCP_RST)) {
       /* expected ACK number? */


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