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authorFrancesco Ruggeri <fruggeri@arista.com>2020-10-07 12:32:52 -0700
committerPablo Neira Ayuso <pablo@netfilter.org>2020-10-20 13:54:53 +0200
commit4f25434bccc28cf8a07876ef5142a2869a674353 (patch)
treead57d912022c7ec6be42bc0bed4fb52d1e3bdeac /net
parent79dce09ab02729a90cf6ce49c9aaaf17aa0d21db (diff)
downloadlinux-stericsson-4f25434bccc28cf8a07876ef5142a2869a674353.tar.gz
netfilter: conntrack: connection timeout after re-register
If the first packet conntrack sees after a re-register is an outgoing keepalive packet with no data (SEG.SEQ = SND.NXT-1), td_end is set to SND.NXT-1. When the peer correctly acknowledges SND.NXT, tcp_in_window fails check III (Upper bound for valid (s)ack: sack <= receiver.td_end) and returns false, which cascades into nf_conntrack_in setting skb->_nfct = 0 and in later conntrack iptables rules not matching. In cases where iptables are dropping packets that do not match conntrack rules this can result in idle tcp connections to time out. v2: adjust td_end when getting the reply rather than when sending out the keepalive packet. Fixes: f94e63801ab2 ("netfilter: conntrack: reset tcp maxwin on re-register") Signed-off-by: Francesco Ruggeri <fruggeri@arista.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/nf_conntrack_proto_tcp.c19
1 files changed, 13 insertions, 6 deletions
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index e8c86ee4c1c4..c8fb2187ad4b 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -541,13 +541,20 @@ static bool tcp_in_window(const struct nf_conn *ct,
swin = win << sender->td_scale;
sender->td_maxwin = (swin == 0 ? 1 : swin);
sender->td_maxend = end + sender->td_maxwin;
- /*
- * We haven't seen traffic in the other direction yet
- * but we have to tweak window tracking to pass III
- * and IV until that happens.
- */
- if (receiver->td_maxwin == 0)
+ if (receiver->td_maxwin == 0) {
+ /* We haven't seen traffic in the other
+ * direction yet but we have to tweak window
+ * tracking to pass III and IV until that
+ * happens.
+ */
receiver->td_end = receiver->td_maxend = sack;
+ } else if (sack == receiver->td_end + 1) {
+ /* Likely a reply to a keepalive.
+ * Needed for III.
+ */
+ receiver->td_end++;
+ }
+
}
} else if (((state->state == TCP_CONNTRACK_SYN_SENT
&& dir == IP_CT_DIR_ORIGINAL)