From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: conntrackd failover works partially, was Re: conntrack performance test results in INVALID packets Date: Thu, 04 Sep 2008 13:40:42 +0200 Message-ID: <48BFC93A.1050905@netfilter.org> References: <488064DD.5080509@bock.nu> <488075F1.80901@bock.nu> <4880891C.4090004@netfilter.org> <4880A6BA.6030007@bock.nu> <489C0835.3090900@netfilter.org> <48BD09B6.5010905@bock.nu> <48BD0DD6.9000803@netfilter.org> <48BD32CC.5010203@bock.nu> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <48BD32CC.5010203@bock.nu> Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Bernhard Bock Cc: netfilter@vger.kernel.org Bernhard Bock wrote: > Pablo Neira Ayuso wrote: >> That's exactly the test that I do in my testbed and it works fine here, >> the problem must be elsewhere. The following line should help to see how >> the connection tracking is marking the traffic as invalid: >> >> echo 255 > /proc/sys/net/ipv4/netfilter/ip_conntrack_log_invalid >> >> However, please see the comment below before doing this and repeating >> the test. > > I didn't know one can increase the verbosity. Now I get some (more) > helpful logs. > > kernel: nf_ct_tcp: invalid packet ignored IN= OUT= SRC=10.5.0.101 > DST=10.6.6.102 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=9977 DF PROTO=TCP > SPT=39101 DPT=80 SEQ=3381624888 ACK=0 WINDOW=5840 RES=0x00 SYN URGP=0 OPT > > Invalid syn packet? The firewall is out-of-sync, this means that firewall has a different state than the client and the server. The packet is not marked as invalid, so it is not dropped but it is logged if ip_conntrack_log_invalid is set up. > Hm. And then: > > kernel: nf_ct_tcp: killing out of sync session IN= OUT= SRC=10.6.6.102 > DST=10.5.0.101 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=TCP SPT=80 > DPT=41647 SEQ=3243074286 ACK=3280173284 WINDOW=5792 RES=0x00 ACK SYN > URGP=0 OPT The firewall sees the syn-ack from the server after the previous - ignored - syn packet. Since the firewall is out-of-sync, the connection tracking system kills conntrack and now it blocks the packet. Thus, the client has to resend the syn to start a clean session. Just to clarify, I don't think that these logs are very helpful for the problem that you're reporting. -- "Los honestos son inadaptados sociales" -- Les Luthiers