From 874ab9233eeddb85fd2dd85131c145bde75da39a Mon Sep 17 00:00:00 2001 From: Jozsef Kadlecsik Date: Tue, 2 Jun 2009 13:58:56 +0200 Subject: netfilter: nf_ct_tcp: TCP simultaneous open support The patch below adds supporting TCP simultaneous open to conntrack. The unused LISTEN state is replaced by a new state (SYN_SENT2) denoting the second SYN sent from the reply direction in the new case. The state table is updated and the function tcp_in_window is modified to handle simultaneous open. The functionality can fairly easily be tested by socat. A sample tcpdump recording 23:21:34.244733 IP (tos 0x0, ttl 64, id 49224, offset 0, flags [DF], proto TCP (6), length 60) 192.168.0.254.2020 > 192.168.0.1.2020: S, cksum 0xe75f (correct), 3383710133:3383710133(0) win 5840 23:21:34.244783 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.0.1.2020 > 192.168.0.254.2020: R, cksum 0x0253 (correct), 0:0(0) ack 3383710134 win 0 23:21:36.038680 IP (tos 0x0, ttl 64, id 28092, offset 0, flags [DF], proto TCP (6), length 60) 192.168.0.1.2020 > 192.168.0.254.2020: S, cksum 0x704b (correct), 2634546729:2634546729(0) win 5840 23:21:36.038777 IP (tos 0x0, ttl 64, id 49225, offset 0, flags [DF], proto TCP (6), length 60) 192.168.0.254.2020 > 192.168.0.1.2020: S, cksum 0xb179 (correct), 3383710133:3383710133(0) ack 2634546730 win 5840 23:21:36.038847 IP (tos 0x0, ttl 64, id 28093, offset 0, flags [DF], proto TCP (6), length 52) 192.168.0.1.2020 > 192.168.0.254.2020: ., cksum 0xebad (correct), ack 3383710134 win 2920 and the corresponding netlink events: [NEW] tcp 6 120 SYN_SENT src=192.168.0.254 dst=192.168.0.1 sport=2020 dport=2020 [UNREPLIED] src=192.168.0.1 dst=192.168.0.254 sport=2020 dport=2020 [UPDATE] tcp 6 120 LISTEN src=192.168.0.254 dst=192.168.0.1 sport=2020 dport=2020 src=192.168.0.1 dst=192.168.0.254 sport=2020 dport=2020 [UPDATE] tcp 6 60 SYN_RECV src=192.168.0.254 dst=192.168.0.1 sport=2020 dport=2020 src=192.168.0.1 dst=192.168.0.254 sport=2020 dport=2020 [UPDATE] tcp 6 432000 ESTABLISHED src=192.168.0.254 dst=192.168.0.1 sport=2020 dport=2020 src=192.168.0.1 dst=192.168.0.254 sport=2020 dport=2020 [ASSURED] The RST packet was dropped in the raw table, thus it did not reach conntrack. nfnetlink_conntrack is unpatched so it shows the new SYN_SENT2 state as the old unused LISTEN. With TCP simultaneous open support we satisfy REQ-2 in RFC 5382 ;-) . Additional minor correction in this patch is that in order to catch uninitialized reply directions, "td_maxwin == 0" is used instead of "td_end == 0" because the former can't be true except in uninitialized state while td_end may accidentally be equal to zero in the mid of a connection. Signed-off-by: Jozsef Kadlecsik Signed-off-by: Patrick McHardy --- include/linux/netfilter/nf_conntrack_tcp.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/netfilter/nf_conntrack_tcp.h b/include/linux/netfilter/nf_conntrack_tcp.h index 3066789..74c27ca 100644 --- a/include/linux/netfilter/nf_conntrack_tcp.h +++ b/include/linux/netfilter/nf_conntrack_tcp.h @@ -15,7 +15,8 @@ enum tcp_conntrack { TCP_CONNTRACK_LAST_ACK, TCP_CONNTRACK_TIME_WAIT, TCP_CONNTRACK_CLOSE, - TCP_CONNTRACK_LISTEN, + TCP_CONNTRACK_LISTEN, /* obsolete */ +#define TCP_CONNTRACK_SYN_SENT2 TCP_CONNTRACK_LISTEN TCP_CONNTRACK_MAX, TCP_CONNTRACK_IGNORE }; -- cgit v1.1