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netfilter: nf_ct_tcp: fix flow recovery with TCP window tracking enabled

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This patch adds the missing bits to support the recovery of TCP flows
without disabling window tracking (aka be_liberal). To ensure a
successful recovery, we have to inject the window scale factor via
ctnetlink.

This patch has been tested with a development snapshot of conntrackd
and the new clause `TCPWindowTracking' that allows to perform strict
TCP window tracking recovery across fail-overs.

With this patch, we don't update the receiver's window until it's not
initiated. We require this to perform a successful recovery. Jozsef
confirmed in a private email that this spotted a real issue since that
should not happen.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Pablo Neira Ayuso 2010-07-15 17:09:04 +02:00 committed by Patrick McHardy
parent cca5cf91c7
commit fac42a9a92
1 changed files with 9 additions and 1 deletions
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10
net/netfilter/nf_conntrack_proto_tcp.c
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@ -585,8 +585,16 @@ static bool tcp_in_window(const struct nf_conn *ct,
* Let's try to use the data from the packet.
*/
sender->td_end = end;
win <<= sender->td_scale;
sender->td_maxwin = (win == 0 ? 1 : win);
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)
receiver->td_end = receiver->td_maxend = sack;
}
} else if (((state->state == TCP_CONNTRACK_SYN_SENT
&& dir == IP_CT_DIR_ORIGINAL)
@ -680,7 +688,7 @@ static bool tcp_in_window(const struct nf_conn *ct,
/*
* Update receiver data.
*/
if (after(end, sender->td_maxend))
if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))
receiver->td_maxwin += end - sender->td_maxend;
if (after(sack + win, receiver->td_maxend - 1)) {
receiver->td_maxend = sack + win;