Author: gallatin
Date: Thu Apr  7 13:49:44 2011
New Revision: 220424
URL: http://svn.freebsd.org/changeset/base/220424

Log:
  Fix a bug in mxge's LRO which can cause dup acks to
  get aggregated & hence prevent TCP from entering
  fast retransmit.
  
  Pointed out by: jeff
  Reviewed by: gnn
  MFC after:    7 days

Modified:
  head/sys/dev/mxge/mxge_lro.c

Modified: head/sys/dev/mxge/mxge_lro.c
==============================================================================
--- head/sys/dev/mxge/mxge_lro.c        Thu Apr  7 13:14:51 2011        
(r220423)
+++ head/sys/dev/mxge/mxge_lro.c        Thu Apr  7 13:49:44 2011        
(r220424)
@@ -237,8 +237,10 @@ mxge_lro_rx(struct mxge_slice_state *ss,
                    lro->dest_ip == ip->ip_dst.s_addr) {
                        /* Try to append it */
 
-                       if (__predict_false(seq != lro->next_seq)) {
-                               /* out of order packet */
+                       if (__predict_false(seq != lro->next_seq ||
+                                   (tcp_data_len == 0 &&
+                                    lro->ack_seq == tcp->th_ack))) {
+                               /* out of order packet or dup ack */
                                SLIST_REMOVE(&ss->lro_active, lro,
                                             lro_entry, next);
                                mxge_lro_flush(ss, lro);
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