diff options
| author | Jozsef Kadlecsik <kadlec@blackhole.kfki.hu> | 2008-06-30 12:41:30 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2008-06-30 12:41:30 -0700 |
| commit | 84ebe1cdae56707b9aa1b40ae5aa7d817ba745f5 (patch) | |
| tree | d325c80abe018baac9cd492a76d38b998ae87d4c /net/netfilter | |
| parent | d420895efb259a78dda50f95289571faa6e10e41 (diff) | |
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/netfilter')
| -rw-r--r-- | net/netfilter/nf_conntrack_proto_tcp.c | 13 |
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 ba94004fe32..271cd01d57a 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). */ |