1 files changed, 20 insertions, 9 deletions

diff --git a/net/ipv4/netfilter/ip_conntrack_proto_tcp.c b/net/ipv4/netfilter/ip_conntrack_proto_tcp.c
index 625981676776..aeb7353d4777 100644
--- a/net/ipv4/netfilter/ip_conntrack_proto_tcp.c
+++ b/net/ipv4/netfilter/ip_conntrack_proto_tcp.c
@@ -272,9 +272,9 @@ static const enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
  *      sCL -> sCL
  */
 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
-/*ack*/    { sIV, sIV, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
+/*ack*/    { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 /*
- *      sSS -> sIV      Might be a half-open connection.
+ *      sSS -> sIG      Might be a half-open connection.
  *      sSR -> sSR      Might answer late resent SYN.
  *      sES -> sES      :-)
  *      sFW -> sCW      Normal close request answered by ACK.
@@ -917,8 +917,12 @@ static int tcp_packet(struct ip_conntrack *conntrack,
 
         switch (new_state) {
         case TCP_CONNTRACK_IGNORE:
-                /* Either SYN in ORIGINAL
-                 * or SYN/ACK in REPLY. */
+                /* Ignored packets:
+                 * 
+                 * a) SYN in ORIGINAL
+                 * b) SYN/ACK in REPLY
+                 * c) ACK in reply direction after initial SYN in original.
+                 */
                 if (index == TCP_SYNACK_SET
                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
                     && conntrack->proto.tcp.last_dir != dir
@@ -985,13 +989,20 @@ static int tcp_packet(struct ip_conntrack *conntrack,
                 }
         case TCP_CONNTRACK_CLOSE:
                 if (index == TCP_RST_SET
-                    && test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
-                    && conntrack->proto.tcp.last_index == TCP_SYN_SET
+                    && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
+                         && conntrack->proto.tcp.last_index == TCP_SYN_SET)
+                        || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
+                            && conntrack->proto.tcp.last_index == TCP_ACK_SET))
                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
-                        /* RST sent to invalid SYN we had let trough
-                         * SYN was in window then, tear down connection.
+                        /* RST sent to invalid SYN or ACK we had let trough
+                         * at a) and c) above:
+                         *
+                         * a) SYN was in window then
+                         * c) we hold a half-open connection.
+                         *
+                         * Delete our connection entry.
                          * We skip window checking, because packet might ACK
-                         * segments we ignored in the SYN. */
+                         * segments we ignored. */
                         goto in_window;
                 }
                 /* Just fall trough */