Messages in this thread | | | Date | Sat, 15 Mar 2008 09:55:27 +0100 | From | Willy Tarreau <> | Subject | Re: [2.6.24.3][net] bug: TCP 3rd handshake abnormal timeouts |
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On Sat, Mar 15, 2008 at 09:47:24AM +0100, Gabriel Barazer wrote: > Hi > > Thanks for the netdev Cc, I didn't know where to write to the "network > guys".
except I just noticed I got it wrong: it's netdev@vger.kernel.org, and I omitted the "vger" part. That's what is expected when posting before caffeine :-)
Feel free to repost the whole issue overthere (along with your new tests) if you don't get useful replies in a few days.
> 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.
What caught my attention was the usual "3s delay", which is purely TCP and application-independant.
> On 03/15/2008 7:58:49 AM +0100, Willy Tarreau <w@1wt.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
OK
> I use wireshark to analyse my pcap files and it says the checksum is > correct on all packets.
OK
> >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).
I'm sure it's a client issue too, that's why it would be reasonable to be able to try without conntrack. Can't you use a TCP proxy instead of REDIRECT ? Also, you said that you also noticed the same behaviour in other environments, maybe there you can disable conntrack ?
Willy
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