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

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Message-ID: <26769.1392390042@warthog.procyon.org.uk>
Date:	Fri, 14 Feb 2014 15:00:42 +0000
From:	David Howells <dhowells@...hat.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	dhowells@...hat.com, netdev@...r.kernel.org
Subject: Re: Does ICMP_FRAG_NEEDED automatically update the routing cache?

Hannes Frederic Sowa <hannes@...essinduktion.org> wrote:

> 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).

Sounds good.  Does this work even if the socket is not connected (ie. the UDP
packets are being routed by the address fields in struct msghdr)?

David
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