[lwip-devel] [bug #20515] TCP delayed ack does not work as expected

[Kieran Mansley]

Follow-up Comment #26, bug #20515 (project lwip):

OK, the change I've made is as follows.  I also spotted I wasn't using the
TCP_SEG_* macros to compare sequence numbers, which was another bug.  I've
also updated the patch to incorporate this change and attached it here.  Oleg:
could you check that this resolves your issue with the advertised window going
to 65535?  If so, I'll check it in so that it can get some wider testing.


diff -r 02a296cfc521 core/tcp.c
--- a/core/tcp.c
+++ b/core/tcp.c
@@ -393,13 +393,19 @@ u32_t tcp_update_rcv_ann_wnd(struct tcp_
 {
   u32_t new_right_edge = pcb->rcv_nxt + pcb->rcv_wnd;

-  if (new_right_edge >= pcb->rcv_ann_right_edge + pcb->mss) {
+  if (TCP_SEQ_GEQ(new_right_edge, pcb->rcv_ann_right_edge + pcb->mss)) {
     /* we can advertise more window */
     pcb->rcv_ann_wnd = pcb->rcv_wnd;
     return new_right_edge - pcb->rcv_ann_right_edge;
   } else {
-    /* keep the right edge of window constant */
-    pcb->rcv_ann_wnd = pcb->rcv_ann_right_edge - pcb->rcv_nxt;
+    if (TCP_SEQ_GT(pcb->rcv_nxt, pcb->rcv_ann_right_edge)) {
+      /* Can happen due to other end sending out of advertised window,
+       * but within actual available (but not yet advertised) window */
+      pcb->rcv_ann_wnd = 0;
+    } else {
+      /* keep the right edge of window constant */
+      pcb->rcv_ann_wnd = pcb->rcv_ann_right_edge - pcb->rcv_nxt;
+    }
     return 0;
   }
 }


(file #17844)
    _______________________________________________________

Additional Item Attachment:

File name: window_updates                 Size:10 KB


    _______________________________________________________

Reply to this item at:

  <http://savannah.nongnu.org/bugs/?20515>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.nongnu.org/