From: Hannes Frederic Sowa <hannes@stressinduktion•org>
To: "Steinar H. Gunderson" <sgunderson@bigfoot•com>
Cc: netdev@vger•kernel.org, edumazet@google•com, fan.du@windriver•com
Subject: Re: IPv6 path MTU discovery broken
Date: Mon, 7 Oct 2013 03:52:52 +0200 [thread overview]
Message-ID: <20131007015252.GE9295@order.stressinduktion.org> (raw)
In-Reply-To: <20131006120612.GA27852@sesse.net>
On Sun, Oct 06, 2013 at 02:06:12PM +0200, Steinar H. Gunderson wrote:
> On Sat, Sep 28, 2013 at 10:33:18PM +0200, Hannes Frederic Sowa wrote:
> >> So the “packet too big” packets really look like they're being ignored.
> >> However, they _do_ reach the kernel somehow, since Icmp6InPktTooBigs
> >> seems to increase.
> >>
> >> Could this be related somehow to the packets coming from 2001:67c:29f4::31,
> >> while the default route is to a link-local address? (An RPF issue?) This used
> >> to work (although it was often flaky for me) in 3.10 and before. I can't
> >> easily bisect, though, as I don't boot this machine too often.
> > This looks like a bug and should definitely get fixed. There should be
> > no RPF issue. May I have a look at your /proc/net/ipv6_route?
>
> It started again, so now I could capture what you asked for:
>
> pannekake:~> cat /proc/net/ipv6_route
> 2001067c00a400037c4d9ae8ab73230f 80 00000000000000000000000000000000 00 fe80000000000000023048fffe555743 00000000 00000001 00000137 01000023 eth0
This one does look like the most probable route which could have the problem.
It has a RTF_MODIFIED flag indicating it received a pmtu update.
Did you take the snapshot while the tcp connection was hanging? We normally
take 2 references to the rt6_info while the tcp connection is running, this
oddly only has one (but got used a lot). But doing a judgement on the
reference count is imprecise.
If you write that this got worse in recent kernels I suspect commit
commit ca4c3fc24e293719fe7410c4e63da9b6bc633b83
Author: fan.du <fan.du@windriver•com>
Date: Tue Jul 30 08:33:53 2013 +0800
net: split rt_genid for ipv4 and ipv6
The commit itself is fine, we may have a problem in our dst check logic
or do not bump rt6_genid at some point? If this is the case I might have
an idea how to reproduce the problem.
Greetings,
Hannes
next prev parent reply other threads:[~2013-10-07 1:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-27 20:14 IPv6 path MTU discovery broken Steinar H. Gunderson
2013-09-28 20:33 ` Hannes Frederic Sowa
2013-09-28 20:51 ` Steinar H. Gunderson
2013-09-28 21:19 ` Hannes Frederic Sowa
2013-10-06 12:06 ` Steinar H. Gunderson
2013-10-06 12:44 ` Hannes Frederic Sowa
2013-10-06 12:48 ` Steinar H. Gunderson
2013-10-07 1:52 ` Hannes Frederic Sowa [this message]
2013-10-07 3:09 ` Hannes Frederic Sowa
2013-10-07 8:32 ` Steinar H. Gunderson
2013-10-07 14:32 ` Hannes Frederic Sowa
2013-10-07 14:34 ` Steinar H. Gunderson
2013-10-07 15:49 ` Eric Dumazet
2013-10-13 10:40 ` Steinar H. Gunderson
2013-10-13 16:51 ` Eric Dumazet
2013-10-13 17:56 ` Hannes Frederic Sowa
2013-10-07 8:29 ` Steinar H. Gunderson
2013-10-07 8:37 ` Steinar H. Gunderson
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