netdev - Re: Does ICMP_FRAG_NEEDED automatically update the routing cache?

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Date:	Fri, 14 Feb 2014 15:44:12 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Howells <dhowells@...hat.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Does ICMP_FRAG_NEEDED automatically update the routing cache?

Hi!

On Fri, Feb 14, 2014 at 02:36:48PM +0000, David Howells wrote:
> Am I reading the ipv4 code right?  If a UDP packet we send results in an
> ICMP_FRAG_NEEDED packet being received, the cached routing information for the
> peer will automatically be updated by __udp4_lib_err()?

A next hop exception will be generated (or reused) which stores the path
mtu towards that target, yes (there is no more routing cache).

Prior to that a validation check happens if the socket really exists (this is
e.g. needed to identify the namespace or routing table the update should occur
on).

> And something similar in __udp6_lib_err()?

Exactly.

Greetings,

  Hannes

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