From e37ad9fd636071e45368d1d9cc3b7b421281ce7f Mon Sep 17 00:00:00 2001 From: Marcelo Leitner Date: Mon, 13 Oct 2014 13:09:28 -0300 Subject: [PATCH] netfilter: nf_conntrack: allow server to become a client in TW handling When a port that was used to listen for inbound connections gets closed and reused for outgoing connections (like rsh ends up doing for stderr flow), current we may reject the SYN/ACK packet for the new connection because tcp_conntracks states forbirds a port to become a client while there is still a TIME_WAIT entry in there for it. As TCP may expire the TIME_WAIT socket in 60s and conntrack's timeout for it is 120s, there is a ~60s window that the application can end up opening a port that conntrack will end up blocking. This patch fixes this by simply allowing such state transition: if we see a SYN, in TIME_WAIT state, on REPLY direction, move it to sSS. Note that the rest of the code already handles this situation, more specificly in tcp_packet(), first switch clause. Signed-off-by: Marcelo Ricardo Leitner Acked-by: Jozsef Kadlecsik Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_proto_tcp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index 44d1ea32570a..d87b6423ffb2 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -213,7 +213,7 @@ static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = { { /* REPLY */ /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ -/*syn*/ { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sS2 }, +/*syn*/ { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sSS, sIV, sS2 }, /* * sNO -> sIV Never reached. * sSS -> sS2 Simultaneous open @@ -223,7 +223,7 @@ static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = { * sFW -> sIV * sCW -> sIV * sLA -> sIV - * sTW -> sIV Reopened connection, but server may not do it. + * sTW -> sSS Reopened connection, but server may have switched role * sCL -> sIV */ /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ -- GitLab