netdev - Re: [RFC] sctp/tcp: Question -- ICMPv4 length check (not) redundant?

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Message-ID: <48906362.2090902@hp.com>
Date:	Wed, 30 Jul 2008 08:49:38 -0400
From:	Vlad Yasevich <vladislav.yasevich@...com>
To:	David Miller <davem@...emloft.net>
Cc:	gerrit@....abdn.ac.uk, netdev@...r.kernel.org
Subject: Re: [RFC] sctp/tcp: Question -- ICMPv4 length check (not) redundant?

David Miller wrote:
> From: Vlad Yasevich <vladislav.yasevich@...com>
> Date: Mon, 28 Jul 2008 14:09:55 -0400
> 
>> The IPv6 checks are much different.  The MUST requirement is to provide as much
>> data as possible upto IPv6 min mtu.  So, the IPv6 icmp code should probably look
>> to see if min(payload_len, min_mtu) is provided.
> 
> "Be liberal in what you accept..." -Jon Postel

Yeah, that check is really too strict.

> 
> Also, do you know any case where 576 bytes won't provide enough
> quoted packet bytes? :-)
> 

Yes, I've seen a case where a full 1280 was needed.  It involved a
very convoluted packet that had extension headers and then went
through 2 encapsulations.  This was an extreme test scenario and
not a real world example.

-vlad
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