[lwip-users] PATCH TCP connection restart

[Paul]

Hi everyone,

Here is patch that fixes the condition where lwip starts a tcp 
connection with a sequence number that is valid for a previous session.
lwip sends a SYN the other end just sends back ACK. With this patch a 
reset is sent and the sequence number is invalidated.
This seqence commonly occurs when debugging lwip or reseting lwip as the 
starting sequence number is fixed.

Paul

Index: tcp_in.c
===================================================================
RCS file: lwip/src/core/tcp_in.c,v
retrieving revision 1.2
diff -u -r1.2 tcp_in.c
--- tcp_in.c    5 Mar 2004 03:36:30 -0000       1.2
+++ tcp_in.c    16 Mar 2004 06:07:04 -0000
@@ -540,8 +540,16 @@
   case SYN_SENT:
     LWIP_DEBUGF(TCP_INPUT_DEBUG, ("SYN-SENT: ackno %lu pcb->snd_nxt %lu 
unacked %lu\n", ackno,
      pcb->snd_nxt, ntohl(pcb->unacked->tcphdr->seqno)));
-    if ((flags & TCP_ACK) && (flags & TCP_SYN)
-        && ackno == ntohl(pcb->unacked->tcphdr->seqno) + 1) {
+    if (flags & (TCP_ACK | TCP_SYN))
+    {
+        if ( ackno != ntohl(pcb->unacked->tcphdr->seqno) + 1) {
+          tcp_rst( ackno, ackno, &(pcb->local_ip), &(pcb->remote_ip), 
pcb->local_port, pcb->remote_port);
+          return ERR_OK;          
+        }
+    } else
+    {
+        return ERR_OK;
+    }
       pcb->rcv_nxt = seqno + 1;
       pcb->lastack = ackno;
       pcb->snd_wnd = tcphdr->wnd;
@@ -561,7 +569,6 @@
        * connected. */
       TCP_EVENT_CONNECTED(pcb, ERR_OK, err);
       tcp_ack(pcb);
-    }
     break;
   case SYN_RCVD:
     if (flags & TCP_ACK &&