netdev - Re: [PATCH 5/5] ipv4: Don't use the cached pmtu informations for input routes

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Message-ID: <20111124001035.GA14996@gondor.apana.org.au>
Date:	Thu, 24 Nov 2011 08:10:35 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	steffen.klassert@...unet.com, netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] ipv4: Don't use the cached pmtu informations for
	input routes

On Wed, Nov 23, 2011 at 04:49:41PM -0500, David Miller wrote:
>
> The issue is that "we", the forwarding entity, end up with a cached on
> the input route and report this cached PMTU to the sender.
> 
> This takes a while to time out.

I understand.  However, this could be seen as an optimisation
as if somehow we as a router discovered the smaller MTU this
would save everybody behind us from having to disocver it by
probing until our discovery expires.

Is there a particular scenario where this breaks? I could only think
of policy routing cases but that's not unique to forwarding as it
also affects us as a host.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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