netdev - Re: [PATCH][net-next][v2] bridge: allow the maximum mtu to 64k

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Message-ID: <20160224134456.3ea94f0a@xeon-e3>
Date:	Wed, 24 Feb 2016 13:44:56 -0800
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	roy.qing.li@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH][net-next][v2] bridge: allow the maximum mtu to 64k

On Tue, 23 Feb 2016 09:00:56 +0800
roy.qing.li@...il.com wrote:

> This is especially annoying for the virtualization case because the
> KVM's tap driver will by default adopt the bridge's MTU on startup
> making it impossible (without the workaround) to use a large MTU on the
> guest VMs.
> 
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1399064

This use case looks like KVM misusing bridge MTU. I.e it should set TAP
MTU to what it wants then enslave it, not vice versa.