netdev - Re: [PATCH] tun: orphan an skb on tx

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Message-ID: <4BC4A139.3010605@siemens.com>
Date:	Tue, 13 Apr 2010 18:52:09 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"Michael S. Tsirkin" <mst@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	Paul Moore <paul.moore@...com>,
	David Woodhouse <David.Woodhouse@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [PATCH] tun: orphan an skb on tx

Eric Dumazet wrote:
> Le mardi 13 avril 2010 à 17:36 +0200, Jan Kiszka a écrit :
>> Michael S. Tsirkin wrote:
>>> The following situation was observed in the field:
>>> tap1 sends packets, tap2 does not consume them, as a result
>>> tap1 can not be closed.
>> And before that, tap1 may not be able to send further packets to anyone
>> else on the bridge as its TX resources were blocked by tap2 - that's
>> what we saw in the field.
>>
> 
> After the patch, tap1 is able to flood tap2, and tap3/tap4 not able to
> send one single frame. Is it OK ?

I think if that's a real issue, you have to apply traffic shaping to the
untrusted nodes. The existing flow-control scheme was fragile anyway as
you had to translate packet lengths on TX side to packet counts on RX.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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