[NETFILTER]: nf_conntrack_tcp: fix connection reopening

With your description I could reproduce the bug and actually you were
completely right: the code above is incorrect. Somehow I was able to
misread RFC1122 and mixed the roles :-(:

   When a connection is >>closed actively<<, it MUST linger in
   TIME-WAIT state for a time 2xMSL (Maximum Segment Lifetime).
   However, it MAY >>accept<< a new SYN from the remote TCP to
   reopen the connection directly from TIME-WAIT state, if it:
   [...]

The fix is as follows: if the receiver initiated an active close, then the
sender may reopen the connection - otherwise try to figure out if we hold
a dead connection.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Tested-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index df718e7c7ee4cc2b80df5ea5aad8a442de360109..c7075345971b000d6396fd07b4c710fcefc22227 100644 (file)
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -831,6 +831,20 @@ static int tcp_packet(struct nf_conn *conntrack,
        tuple = &conntrack->tuplehash[dir].tuple;
 
        switch (new_state) {
+       case TCP_CONNTRACK_SYN_SENT:
+               if (old_state < TCP_CONNTRACK_TIME_WAIT)
+                       break;
+               if (conntrack->proto.tcp.seen[!dir].flags &
+                       IP_CT_TCP_FLAG_CLOSE_INIT) {
+                       /* Attempt to reopen a closed connection.
+                       * Delete this connection and look up again. */
+                       write_unlock_bh(&tcp_lock);
+                       if (del_timer(&conntrack->timeout))
+                               conntrack->timeout.function((unsigned long)
+                                                           conntrack);
+                       return -NF_REPEAT;
+               }
+               /* Fall through */
        case TCP_CONNTRACK_IGNORE:
                /* Ignored packets:
                 *
@@ -879,27 +893,6 @@ static int tcp_packet(struct nf_conn *conntrack,
                        nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
                                  "nf_ct_tcp: invalid state ");
                return -NF_ACCEPT;
-       case TCP_CONNTRACK_SYN_SENT:
-               if (old_state < TCP_CONNTRACK_TIME_WAIT)
-                       break;
-               if ((conntrack->proto.tcp.seen[dir].flags &
-                       IP_CT_TCP_FLAG_CLOSE_INIT)
-                   || after(ntohl(th->seq),
-                            conntrack->proto.tcp.seen[dir].td_end)) {
-                       /* Attempt to reopen a closed connection.
-                       * Delete this connection and look up again. */
-                       write_unlock_bh(&tcp_lock);
-                       if (del_timer(&conntrack->timeout))
-                               conntrack->timeout.function((unsigned long)
-                                                           conntrack);
-                       return -NF_REPEAT;
-               } else {
-                       write_unlock_bh(&tcp_lock);
-                       if (LOG_INVALID(IPPROTO_TCP))
-                               nf_log_packet(pf, 0, skb, NULL, NULL,
-                                             NULL, "nf_ct_tcp: invalid SYN");
-                       return -NF_ACCEPT;
-               }
        case TCP_CONNTRACK_CLOSE:
                if (index == TCP_RST_SET
                    && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)