From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: [PATCH -stable 02/02]: netfilter: nf_conntrack_tcp: fixing to check the lower bound of valid ACK Date: Mon, 07 Jul 2008 15:57:03 +0200 Message-ID: <487220AF.5070204@trash.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------060809080707000904000401" Cc: "David S. Miller" , Netfilter Development Mailinglist To: stable@kernel.org Return-path: Received: from stinky.trash.net ([213.144.137.162]:61403 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752939AbYGGN5G (ORCPT ); Mon, 7 Jul 2008 09:57:06 -0400 Sender: netfilter-devel-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------060809080707000904000401 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit --------------060809080707000904000401 Content-Type: text/x-diff; name="02.diff" Content-Transfer-Encoding: 8bit Content-Disposition: inline; filename="02.diff" netfilter: nf_conntrack_tcp: fixing to check the lower bound of valid ACK Upstream commit 84ebe1c: 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 Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- commit 9524a965e043b5aac8770b39a0d444da30655ec4 tree 6f88f35682e10fad204228331ec89b50c6477577 parent 44e450bf173eee791911a56f7e65a30d94608cea author Jozsef Kadlecsik Mon, 07 Jul 2008 15:52:48 +0200 committer Patrick McHardy Mon, 07 Jul 2008 15:52:48 +0200 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 6256795..fc43e22 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -332,12 +332,13 @@ 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. */ @@ -607,12 +608,12 @@ static int 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). */ --------------060809080707000904000401--