From: Andrew Savchenko <bircoph@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: [BUG] Kernel recieves DNS reply, but doesn't deliver it to a waiting application
Date: Mon, 4 Feb 2013 17:39:32 +0400 [thread overview]
Message-ID: <20130204173932.bad780bc.bircoph@gmail.com> (raw)
In-Reply-To: <20130116203644.8eb2a16f.bircoph@gmail.com>
[-- Attachment #1.1: Type: text/plain, Size: 1480 bytes --]
Hello,
On Wed, 16 Jan 2013 20:36:44 +0400 Andrew Savchenko wrote:
> On Fri, 28 Dec 2012 10:11:03 -0800 Eric Dumazet wrote:
[...]
> > Thanks a lot !
> >
> > I see strange drops in dev_hard_start_xmit()
> >
> > l2tp needs some care.
> >
> > Please try the following patch, as skb_cow_head() API
> > doesnt really ease skb->truesize exact tracking anyway, better not mess
> > with it.
>
> Sorry for the delay, but I was able to reboot kernel only today.
> Your patch is applied on top of the 3.7.2 vanilla kernel.
>
> l2tp works fine and /proc/net/udp tx_queue values are normal now, see
> attached /prot/net/udp output. This is a good hint that problem is
> probably solved, but we need to wait at least several weeks to be
> sure.
With 16-days uptime system works fine.
Also I was able to reproduce this bug on another box: an embedded
system running openwrt with 3.7.5 kernel with openl2tpd client and
dnsmasq server. Due to limited memory resources this bug happened to
be easily reproducible: several thousands of dns queries were
sufficient to reproduce this bug. Full debug on embedded box was not
possible due to constrained resources, but bug appearance was the same
and /proc/net/udp is apparently broken (see attached log).
I applied your patch on openwrt's 3.7.5 kernel and it fixed the bug
on this box too.
So we've found a solution and I'm looking forward for it in the main
kernel :)
Best regards,
Andrew Savchenko
[-- Attachment #1.2: proc.net.udp --]
[-- Type: application/octet-stream, Size: 1794 bytes --]
# cat /proc/net/udp
sl local_address rem_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode ref pointer drops
42: 00000000:7B2A 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6239 2 816bb760 1
53: 00000000:0035 00000000:0000 07 00000000:00000000 00:00000000 00000000 0 0 1476 2 81b6e440 0
67: 00000000:0043 00000000:0000 07 00000000:00000000 00:00000000 00000000 0 0 1471 2 81b6e220 0
76: 00000000:1B4C 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6225 2 816bacc0 1
95: 00000000:165F 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6221 2 816ba880 1
101: 0A34182E:AE65 0A320014:06A5 01 00000000:00000000 00:00000000 00000000 0 0 1538 4 81b6ecc0 0
123: 00000000:007B 00000000:0000 07 00000000:00000000 00:00000000 00000000 0 0 1530 2 81b6e880 0
126: 00000000:847E 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6223 2 816baaa0 1
153: 00000000:CF99 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6233 2 816bb540 1
163: 00000000:09A3 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6227 2 816baee0 1
165: 00000000:06A5 00000000:0000 07 00000000:00000000 00:00000000 00000000 0 0 1523 2 81b6e660 0
184: 00000000:70B8 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6231 2 816bb320 1
226: 00000000:CCE2 00000000:0000 07 FFFFFFB0:00000000 00:00000000 00000000 65534 0 6229 2 816bb100 1
[-- Attachment #2: Type: application/pgp-signature, Size: 198 bytes --]
next prev parent reply other threads:[~2013-02-04 13:39 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-03 19:25 Kernel recieves DNS reply, but doesn't deliver it to a waiting application Andrew Savchenko
2012-10-13 12:36 ` [BUG] " Andrew Savchenko
2012-10-13 13:44 ` Eric Dumazet
2012-10-13 23:11 ` Andrew Savchenko
2012-10-20 23:25 ` Andrew Savchenko
2012-10-21 12:52 ` Eric Dumazet
2012-10-22 3:36 ` Andrew Savchenko
2012-10-22 6:48 ` Eric Dumazet
2012-10-22 21:27 ` Andrew Savchenko
2012-12-12 8:27 ` Andrew Savchenko
2012-12-23 11:06 ` Andrew Savchenko
2012-12-28 18:11 ` Eric Dumazet
2013-01-16 16:36 ` Andrew Savchenko
2013-02-04 13:39 ` Andrew Savchenko [this message]
2013-02-04 15:21 ` Eric Dumazet
2012-11-23 7:45 ` Andrew Savchenko
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