linux-kernel - Re: [PATCH v2 1/2] ip6_gre: Fix MTU setting for ip6gretap

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Message-Id: <20160524.143417.15421952212090108.davem@davemloft.net>
Date:	Tue, 24 May 2016 14:34:17 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	yanhaishuang@...s.chinamobile.com
Cc:	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] ip6_gre: Fix MTU setting for ip6gretap

From: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
Date: Sat, 21 May 2016 18:17:34 +0800

> When creat an ip6gretap interface with an unreachable route,
> the MTU is about 14 bytes larger than what was needed.
 ...
> Because rt is not NULL here, so dev->mtu will subtract the ethernet
> header length later. But when rt is NULL, it just simply return, so
> dev->mtu doesn't update correctly in this situation.
> 
> This patch first verify the dev->type is ARPHRD_ETHER for ip6gretap
> interface, and then decrease the mtu as early as possible.
> 
> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>

Applied.