linux-kernel - Re: [PATCHv3] tun: only queue packets on device

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] [day] [month] [year] [list]

Date:	Mon, 03 Dec 2012 15:07:59 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	mst@...hat.com
Cc:	jasowang@...hat.com, nhorman@...driver.com, ramirose@...il.com,
	davej@...hat.com, mtk.manpages@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3] tun: only queue packets on device

From: "Michael S. Tsirkin" <mst@...hat.com>
Date: Mon, 3 Dec 2012 22:07:14 +0200

> Historically tun supported two modes of operation:
> - in default mode, a small number of packets would get queued
>   at the device, the rest would be queued in qdisc
> - in one queue mode, all packets would get queued at the device
> 
> This might have made sense up to a point where we made the
> queue depth for both modes the same and set it to
> a huge value (500) so unless the consumer
> is stuck the chance of losing packets is small.
> 
> Thus in practice both modes behave the same, but the
> default mode has some problems:
> - if packets are never consumed, fragments are never orphaned
>   which cases a DOS for sender using zero copy transmit
> - overrun errors are hard to diagnose: fifo error is incremented
>   only once so you can not distinguish between
>   userspace that is stuck and a transient failure,
>   tcpdump on the device does not show any traffic
> 
> Userspace solves this simply by enabling IFF_ONE_QUEUE
> but there seems to be little point in not doing the
> right thing for everyone, by default.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Applied, thanks Michael.
--
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/