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[NETFILTER]: nf_conntrack_tcp: fix connection reopening

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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>
This commit is contained in:
Jozsef Kadlecsik 2007-10-11 14:35:52 -07:00 committed by David S. Miller
parent d71fce6b93
commit 17311393f9
1 changed files with 14 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
net/netfilter/nf_conntrack_proto_tcp.c
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@ -831,6 +831,20 @@ static int tcp_packet(struct nf_conn *conntrack,
tuple = &conntrack->tuplehash[dir].tuple; tuple = &conntrack->tuplehash[dir].tuple;
switch (new_state) { 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: case TCP_CONNTRACK_IGNORE:
/* Ignored packets: /* Ignored packets:
* *
@ -879,27 +893,6 @@ static int tcp_packet(struct nf_conn *conntrack,
nf_log_packet(pf, 0, skb, NULL, NULL, NULL, nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
"nf_ct_tcp: invalid state "); "nf_ct_tcp: invalid state ");
return -NF_ACCEPT; 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: case TCP_CONNTRACK_CLOSE:
if (index == TCP_RST_SET if (index == TCP_RST_SET
&& ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status) && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)