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authorJozsef Kadlecsik <kadlec@blackhole.kfki.hu>2008-02-19 16:24:01 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2008-02-25 15:59:23 -0800
commit98d047714d208a6f8a933175a32d7d33931198ad (patch)
tree9bc3e7418afc8ed7321e11fcfec7a428c6cac378
parent3b62bc1363411799eac3d7dab2412b2df3fa9ac0 (diff)
NETFILTER: nf_conntrack_tcp: conntrack reopening fix
[NETFILTER]: nf_conntrack_tcp: conntrack reopening fix [Upstream commits b2155e7f + d0c1fd7a] TCP connection tracking in netfilter did not handle TCP reopening properly: active close was taken into account for one side only and not for any side, which is fixed now. The patch includes more comments to explain the logic how the different cases are handled. The bug was discovered by Jeff Chua. Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--net/netfilter/nf_conntrack_proto_tcp.c33
1 files changed, 26 insertions, 7 deletions
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 2721ff4b1c18..baff1f420875 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -143,7 +143,7 @@ enum tcp_bit_set {
* CLOSE_WAIT: ACK seen (after FIN)
* LAST_ACK: FIN seen (after FIN)
* TIME_WAIT: last ACK seen
- * CLOSE: closed connection
+ * CLOSE: closed connection (RST)
*
* LISTEN state is not used.
*
@@ -842,8 +842,21 @@ static int tcp_packet(struct nf_conn *conntrack,
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)
+ /* RFC 1122: "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..."
+ * We ignore the conditions because we are in the
+ * TIME-WAIT state anyway.
+ *
+ * Handle aborted connections: we and the server
+ * think there is an existing connection but the client
+ * aborts it and starts a new one.
+ */
+ if (((conntrack->proto.tcp.seen[dir].flags
+ | conntrack->proto.tcp.seen[!dir].flags)
+ & IP_CT_TCP_FLAG_CLOSE_INIT)
|| (conntrack->proto.tcp.last_dir == dir
&& conntrack->proto.tcp.last_index == TCP_RST_SET)) {
/* Attempt to reopen a closed/aborted connection.
@@ -858,16 +871,23 @@ static int tcp_packet(struct nf_conn *conntrack,
case TCP_CONNTRACK_IGNORE:
/* Ignored packets:
*
+ * Our connection entry may be out of sync, so ignore
+ * packets which may signal the real connection between
+ * the client and the server.
+ *
* a) SYN in ORIGINAL
* b) SYN/ACK in REPLY
* c) ACK in reply direction after initial SYN in original.
+ *
+ * If the ignored packet is invalid, the receiver will send
+ * a RST we'll catch below.
*/
if (index == TCP_SYNACK_SET
&& conntrack->proto.tcp.last_index == TCP_SYN_SET
&& conntrack->proto.tcp.last_dir != dir
&& ntohl(th->ack_seq) ==
conntrack->proto.tcp.last_end) {
- /* This SYN/ACK acknowledges a SYN that we earlier
+ /* b) This SYN/ACK acknowledges a SYN that we earlier
* ignored as invalid. This means that the client and
* the server are both in sync, while the firewall is
* not. We kill this session and block the SYN/ACK so
@@ -892,7 +912,7 @@ static int tcp_packet(struct nf_conn *conntrack,
write_unlock_bh(&tcp_lock);
if (LOG_INVALID(IPPROTO_TCP))
nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
- "nf_ct_tcp: invalid packed ignored ");
+ "nf_ct_tcp: invalid packet ignored ");
return NF_ACCEPT;
case TCP_CONNTRACK_MAX:
/* Invalid packet */
@@ -948,8 +968,7 @@ static int tcp_packet(struct nf_conn *conntrack,
conntrack->proto.tcp.state = new_state;
if (old_state != new_state
- && (new_state == TCP_CONNTRACK_FIN_WAIT
- || new_state == TCP_CONNTRACK_CLOSE))
+ && new_state == TCP_CONNTRACK_FIN_WAIT)
conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
timeout = conntrack->proto.tcp.retrans >= nf_ct_tcp_max_retrans
&& *tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans