[PATCH nf-next] netfilter: synproxy: fix rst sequence number mismatch

[PATCH nf-next] netfilter: synproxy: fix rst sequence number mismatch

[Fernando Fernandez Mancera]

14:51:00.024418 IP 192.168.122.1.41462 > netfilter.90: Flags [S], seq
4023580551, win 64240, options [mss 1460,sackOK,TS val 2149563785 ecr
0,nop,wscale 7], length 0
14:51:00.024454 IP netfilter.90 > 192.168.122.1.41462: Flags [S.], seq
727560212, ack 4023580552, win 0, options [mss 1460,sackOK,TS val 355031 ecr
2149563785,nop,wscale 7], length 0
14:51:00.024524 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1, win
502, options [nop,nop,TS val 2149563785 ecr 355031], length 0
14:51:00.024550 IP netfilter.90 > 192.168.122.1.41462: Flags [R.], seq
3567407084, ack 1, win 0, length 0
14:51:00.231196 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1, win
502, options [nop,nop,TS val 2149563992 ecr 355031], length 0
14:51:00.647911 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1, win
502, options [nop,nop,TS val 2149564408 ecr 355031], length 0
14:51:01.474395 IP 192.168.122.1.41462 > netfilter.90: Flags [.], ack 1, win
502, options [nop,nop,TS val 2149565235 ecr 355031], length 0

Fixes: 48b1de4c110a ("netfilter: add SYNPROXY core/target")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
---
 net/netfilter/nf_synproxy_core.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index 6676a3842a0c..cc6f951d156b 100644
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -694,8 +694,11 @@ ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
 		}
 
 		if (!th->syn || th->ack ||
-		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
+		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
+			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
+						      ntohl(th->seq) + 1);
 			break;
+		}
 
 		/* Reopened connection - reset the sequence number and timestamp
 		 * adjustments, they will get initialized once the connection is
@@ -1118,8 +1121,11 @@ ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
 		}
 
 		if (!th->syn || th->ack ||
-		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
+		    CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
+			nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
+						      ntohl(th->seq) + 1);
 			break;
+		}
 
 		/* Reopened connection - reset the sequence number and timestamp
 		 * adjustments, they will get initialized once the connection is
-- 
2.20.1