Fixed bug #21494: The send mss (pcb->mss) is set to 536 (or TCP_MSS if that is smaller) as long as no MSS option is received from the remote host.

CHANGELOG

@@ -435,6 +435,11 @@ HISTORY
 
   ++ Bug fixes:
 
+  2007-11-01 Simon Goldschmidt
+  * tcp.c, tcp_in.c: Fixed bug #21494: The send mss (pcb->mss) is set to 536 (or
+    TCP_MSS if that is smaller) as long as no MSS option is received from the
+    remote host.
+
   2007-11-01 Simon Goldschmidt
   * tcp.h, tcp.c, tcp_in.c: Fixed bug #21491: The MSS option sent (with SYN)
     is now based on TCP_MSS instead of pcb->mss (on passive open now effectively

src/core/tcp.c

@@ -492,7 +492,7 @@ tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
   pcb->rcv_wnd = TCP_WND;
   pcb->snd_wnd = TCP_WND;
   /* The send MSS is updated when an MSS option is received. */
-  pcb->mss = TCP_MSS;
+  pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
   pcb->cwnd = 1;
   pcb->ssthresh = pcb->mss * 10;
   pcb->state = SYN_SENT;
@@ -932,7 +932,7 @@ tcp_alloc(u8_t prio)
     pcb->tos = 0;
     pcb->ttl = TCP_TTL;
     /* The send MSS is updated when an MSS option is received. */
-    pcb->mss = TCP_MSS;
+    pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
     pcb->rto = 3000 / TCP_SLOW_INTERVAL;
     pcb->sa = 0;
     pcb->sv = 3000 / TCP_SLOW_INTERVAL;

src/core/tcp_in.c

@@ -519,6 +519,10 @@ tcp_process(struct tcp_pcb *pcb)
        * can be changed by the received options! */
       tcp_parseopt(pcb);
 
+      /* Set ssthresh again after changing pcb->mss (already set in tcp_connect
+       * but for the default value of pcb->mss) */
+      pcb->ssthresh = pcb->mss * 10;
+
       pcb->cwnd = ((pcb->cwnd == 1) ? (pcb->mss * 2) : pcb->mss);
       LWIP_ASSERT("pcb->snd_queuelen > 0", (pcb->snd_queuelen > 0));
       --pcb->snd_queuelen;