netdev - Re: [RFC] packet: handle too big packets for PACKET

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Message-ID: <1408068085.6804.75.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 14 Aug 2014 19:01:25 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Daniel Borkmann <dborkman@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [RFC] packet: handle too big packets for PACKET_V3

On Fri, 2014-08-15 at 03:04 +0200, Hannes Frederic Sowa wrote:

> Sure, but if I would have written such a tool without knowledge of GRO I
> would have queried at least the MTU. ;)

Would all existing tools react to a mtu change properly ?

(It would have to reinit its af_packet ring)

I do not think its a GRO issue, really, but an optimistic PACKET_V3
implementation. GRO was already there when PACKET_V3 was added.

Even a non GRO packet might not fit and we need to avoid the
crash/corruption.

I believe I am going to implement 2)  (clamp the snaplen)

An application should catch that tp_len might be bigger than tp_snaplen
and eventually do something sensible about it.

BTW, tp_sizeof_priv doesnt look to be checked at all, user input is
accepted as is.

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