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authorJozsef Kadlecsik <kadlec@blackhole.kfki.hu>2008-06-30 23:41:30 +0400
committerDavid S. Miller <davem@davemloft.net>2008-06-30 23:41:30 +0400
commit84ebe1cdae56707b9aa1b40ae5aa7d817ba745f5 (patch)
treed325c80abe018baac9cd492a76d38b998ae87d4c /net
parentd420895efb259a78dda50f95289571faa6e10e41 (diff)
downloadlinux-84ebe1cdae56707b9aa1b40ae5aa7d817ba745f5.tar.xz
netfilter: nf_conntrack_tcp: fixing to check the lower bound of valid ACK
Lost connections was reported by Thomas Bätzler (running 2.6.25 kernel) on the netfilter mailing list (see the thread "Weird nat/conntrack Problem with PASV FTP upload"). He provided tcpdump recordings which helped to find a long lingering bug in conntrack. In TCP connection tracking, checking the lower bound of valid ACK could lead to mark valid packets as INVALID because: - We have got a "higher or equal" inequality, but the test checked the "higher" condition only; fixed. - If the packet contains a SACK option, it could occur that the ACK value was before the left edge of our (S)ACK "window": if a previous packet from the other party intersected the right edge of the window of the receiver, we could move forward the window parameters beyond accepting a valid ack. Therefore in this patch we check the rightmost SACK edge instead of the ACK value in the lower bound of valid (S)ACK test. Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/nf_conntrack_proto_tcp.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index ba94004fe323..271cd01d57ae 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -331,12 +331,13 @@ static unsigned int get_conntrack_index(const struct tcphdr *tcph)
I. Upper bound for valid data: seq <= sender.td_maxend
II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin
- III. Upper bound for valid ack: sack <= receiver.td_end
- IV. Lower bound for valid ack: ack >= receiver.td_end - MAXACKWINDOW
+ III. Upper bound for valid (s)ack: sack <= receiver.td_end
+ IV. Lower bound for valid (s)ack: sack >= receiver.td_end - MAXACKWINDOW
- where sack is the highest right edge of sack block found in the packet.
+ where sack is the highest right edge of sack block found in the packet
+ or ack in the case of packet without SACK option.
- The upper bound limit for a valid ack is not ignored -
+ The upper bound limit for a valid (s)ack is not ignored -
we doesn't have to deal with fragments.
*/
@@ -606,12 +607,12 @@ static bool tcp_in_window(const struct nf_conn *ct,
before(seq, sender->td_maxend + 1),
after(end, sender->td_end - receiver->td_maxwin - 1),
before(sack, receiver->td_end + 1),
- after(ack, receiver->td_end - MAXACKWINDOW(sender)));
+ after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1));
if (before(seq, sender->td_maxend + 1) &&
after(end, sender->td_end - receiver->td_maxwin - 1) &&
before(sack, receiver->td_end + 1) &&
- after(ack, receiver->td_end - MAXACKWINDOW(sender))) {
+ after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) {
/*
* Take into account window scaling (RFC 1323).
*/