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

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Date:	Mon, 28 Jul 2008 21:08:19 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Gerrit Renker <gerrit@....abdn.ac.uk>,
	David Miller <davem@...emloft.net>, vladislav.yasevich@...com,
	netdev@...r.kernel.org
Subject: Re: [RFC] sctp/tcp: Question -- ICMPv4 length check (not) redundant?

On Mon, Jul 28, 2008 at 12:25:27PM +0100, Gerrit Renker wrote:
> Thank you for the input. To sum up,
>  * removing the per-protocol "ICMP payload too short" test and error counter
>    increment as initially suggested does not seem right;
>  * there are protocols such as IPComp which have a header length less than
>    8 bytes(and for these the test in the ICMP handler may be too much);
>  * there are protocols such as DCCP which need more than 8 bytes (at least 12)
>    to interpret the ICMP message in a meaningful way;
>  * the requirement of having at least 8 bytes of transport-layer data available
>    is stringent (afaik) only for ICMPv4, but not ICMPv6;
>  * only TCP/SCTP seem to have a proper per-protocol "payload too short" test;
>  * for DCCP, the work is actually doubled since 
>    - first the ICMP handler tests for minimally 8 bytes, 
>    - then the DCCP error handler tests for required minimum of 12 bytes.
> 
> Thus the patch at the begginning of this thread should be disregarded.
> It might be worth to consider per-protocol handlers.

Yes the centralised test predates protocols such as IPComp and
DCCP.  I think it's best to just kill it and add checks in the
protocol handlers where needed.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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