Fixed bug #27504: tcp_enqueue wrongly concatenates segments which are not consecutive when retransmitting unacked segments

CHANGELOG

@@ -43,6 +43,10 @@ HISTORY
 
   ++ Bugfixes:
 
+  2009-10-11 Simon Goldschmidt (Jörg Kesten)
+  * tcp_out.c: Fixed bug #27504: tcp_enqueue wrongly concatenates segments
+    which are not consecutive when retransmitting unacked segments
+
   2009-10-09 Simon Goldschmidt
   * opt.h: Fixed default values of some stats to only be enabled if used
     Fixes bug #27338: sys_stats is defined when NO_SYS = 1

src/core/tcp_out.c

@@ -347,7 +347,9 @@ tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len,
     /* fit within max seg size */
     (useg->len + queue->len <= pcb->mss) &&
     /* only concatenate segments with the same options */
-    (useg->flags == queue->flags)) {
+    (useg->flags == queue->flags) &&
+    /* segments are consecutive */
+    (ntohl(useg->tcphdr->seqno) + useg->len == ntohl(queue->tcphdr->seqno)) ) {
     /* Remove TCP header from first segment of our to-be-queued list */
     if(pbuf_header(queue->p, -(TCP_HLEN + optlen))) {
       /* Can we cope with this failing?  Just assert for now */