From 72d4d3e3980702809509586d36015b7c3c51fad4 Mon Sep 17 00:00:00 2001 From: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu> Date: Sat, 21 Apr 2018 13:43:48 +0200 Subject: netfilter: Fix handling simultaneous open in TCP conntrack Dominique Martinet reported a TCP hang problem when simultaneous open was used. The problem is that the tcp_conntracks state table is not smart enough to handle the case. The state table could be fixed by introducing a new state, but that would require more lines of code compared to this patch, due to the required backward compatibility with ctnetlink. Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu> Reported-by: Dominique Martinet <asmadeus@codewreck.org> Tested-by: Dominique Martinet <asmadeus@codewreck.org> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> --- net/netfilter/nf_conntrack_proto_tcp.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'net/netfilter') diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index e97cdc1cf98c..8e67910185a0 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -981,6 +981,17 @@ static int tcp_packet(struct nf_conn *ct, return NF_ACCEPT; /* Don't change state */ } break; + case TCP_CONNTRACK_SYN_SENT2: + /* tcp_conntracks table is not smart enough to handle + * simultaneous open. + */ + ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN; + break; + case TCP_CONNTRACK_SYN_RECV: + if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET && + ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN) + new_state = TCP_CONNTRACK_ESTABLISHED; + break; case TCP_CONNTRACK_CLOSE: if (index == TCP_RST_SET && (ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) -- cgit v1.2.3