From: Sabrina Dubroca <[email protected]>
Date: Mon, 26 Feb 2018 16:13:43 +0100

> According to RFC 1191 sections 3 and 4, ICMP frag-needed messages
> indicating an MTU below 68 should be rejected:
> 
>     A host MUST never reduce its estimate of the Path MTU below 68
>     octets.
> 
> and (talking about ICMP frag-needed's Next-Hop MTU field):
> 
>     This field will never contain a value less than 68, since every
>     router "must be able to forward a datagram of 68 octets without
>     fragmentation".
> 
> Furthermore, by letting net.ipv4.route.min_pmtu be set to negative
> values, we can end up with a very large PMTU when (-1) is cast into u32.
> 
> Let's also make ip_rt_min_pmtu a u32, since it's only ever compared to
> unsigned ints.
> 
> Reported-by: Jianlin Shi <[email protected]>
> Signed-off-by: Sabrina Dubroca <[email protected]>
> Reviewed-by: Stefano Brivio <[email protected]>

Applied and queued up for -stable, thanks Sabrina.

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