linux-kernel - Re: [2.6.24.3][net] bug: TCP 3rd handshake abnormal timeouts

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 15 Mar 2008 09:47:24 +0100
From:	Gabriel Barazer <gabriel@...va.fr>
To:	Willy Tarreau <w@....eu>
CC:	linux-kernel@...r.kernel.org, netdev@...nel.org
Subject: Re: [2.6.24.3][net] bug: TCP 3rd handshake abnormal timeouts

Hi

Thanks for the netdev Cc, I didn't know where to write to the "network 
guys".

By the way thanks for replying. It's hard to explain and describe a 
problem when you know people will ask you hundreds of questions related 
to application-level problems, or not reply because web/mysql problems 
are so common and generally not related to any kernel issue.

On 03/15/2008 7:58:49 AM +0100, Willy Tarreau <w@....eu> wrote:
> 
> You should carefully check the the SYN-ACK received by the client has a
> correct checksum ("cksum OK" in tcpdump output). It would be possible
> that for some reason, something on the network randomly corrupts it.

I used to use TCP offloading one time, and by the way never had a 
problem with it. Besides just to be sure, I have been able to reproduce 
the problem without any offload engine enabled (= not compiled into the 
kernel, mainly because it seems to hang the kernel at boot in 2.6.24.3). 
So I assume that is not the problem

I use wireshark to analyse my pcap files and it says the checksum is 
correct on all packets.

> Also, you say you have netfilter with conntrack. Is this on the client ?
> If so, you should try disabling it to rule out any possible bug in the
> connection tracking.

I have the conntrack  on both the client and server, and unfortunately 
can't disable it now on the client (I use it only for the REDIRECT 
target on a precise destination address and port, not MySQL related), 
however I will test today and disable it on the server, after I get some 
sleep (although I think the issue is on the client).

Gabriel
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/