linux-kernel - 3.14 regression: huge latency in read/select on tun

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-next>] [day] [month] [year] [list]

Message-ID: <533C381E.9090103@odi.ch>
Date:	Wed, 02 Apr 2014 18:17:34 +0200
From:	Ortwin Glück <odi@....ch>
To:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: 3.14 regression: huge latency in read/select on tun

Hi,

Since 3.14 the openconnect VPN tunnel becomes unusable for me because
packets appear on the tun device at a horribly low rate. 3.12 and 3.13
do not exhibt the problem.

Here is an strace of openconnect trying to read from its fd
  7 -> /dev/net/tun

15:07:33.130640 read(7, 0x1e05e58, 1280) = -1 EAGAIN (Resource
temporarily unavailable)
===> should return available data already
15:07:33.130745 select(8, [3 6 7], [], [6], {30, 0}) = 1 (in [7], left
{29, 783272})
===> HUGE 217ms delay here
15:07:33.347681 read(6, 0x1dfc973, 5)   = -1 EAGAIN (Resource
temporarily unavailable)
15:07:33.347806 read(7,
"E\10\5\0b\343@\0@\6\17~\n\363X\236\n\271UE\222:\0\26\37O\7\342\315\21q\33"...,
1280) = 1280


The send queue of the socket being routed via the tun device has a lot
of outstanding data (here an scp/ssh upload):
tcp        0  29788 local:46577  remote:22   ESTABLISHED

(IPs replaced for privacy)

toggling TCP autocorking has no influence.

Any ideas what could be the culprit?

Ortwin
--
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/