netdev - Re: [PATCH net] ipv4: igmp: guard against silly MTU values

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Message-Id: <20171213.131721.876602280739964396.davem@davemloft.net>
Date:   Wed, 13 Dec 2017 13:17:21 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv4: igmp: guard against silly MTU values

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 11 Dec 2017 07:17:39 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> IPv4 stack reacts to changes to small MTU, by disabling itself under
> RTNL.
> 
> But there is a window where threads not using RTNL can see a wrong
> device mtu. This can lead to surprises, in igmp code where it is
> assumed the mtu is suitable.
> 
> Fix this by reading device mtu once and checking IPv4 minimal MTU.
> 
> This patch adds missing IPV4_MIN_MTU define, to not abuse
> ETH_MIN_MTU anymore.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable.