netfilter: conntrack: don't refresh sctp entries in closed state

Vivek Thrivikraman reported:
 An SCTP server application which is accessed continuously by client
 application.
 When the session disconnects the client retries to establish a connection.
 After restart of SCTP server application the session is not established
 because of stale conntrack entry with connection state CLOSED as below.

 (removing this entry manually established new connection):

 sctp 9 CLOSED src=10.141.189.233 [..]  [ASSURED]

Just skip timeout update of closed entries, we don't want them to
stay around forever.

Reported-and-tested-by: Vivek Thrivikraman <vivek.thrivikraman@est.tech>
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1579
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index 2394238..5a93633 100644 (file)
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -489,6 +489,15 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct,
                        pr_debug("Setting vtag %x for dir %d\n",
                                 ih->init_tag, !dir);
                        ct->proto.sctp.vtag[!dir] = ih->init_tag;
+
+                       /* don't renew timeout on init retransmit so
+                        * port reuse by client or NAT middlebox cannot
+                        * keep entry alive indefinitely (incl. nat info).
+                        */
+                       if (new_state == SCTP_CONNTRACK_CLOSED &&
+                           old_state == SCTP_CONNTRACK_CLOSED &&
+                           nf_ct_is_confirmed(ct))
+                               ignore = true;
                }
 
                ct->proto.sctp.state = new_state;