netdev - Re: [PATCH net 1/2] vxlan: Relax the MTU constraint on vxlan devices

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Message-ID: <20160107112414.GH32456@pox.localdomain>
Date:	Thu, 7 Jan 2016 12:24:14 +0100
From:	Thomas Graf <tgraf@...g.ch>
To:	David Wragg <david@...ve.works>
Cc:	netdev@...r.kernel.org, dev@...nvswitch.org
Subject: Re: [PATCH net 1/2] vxlan: Relax the MTU constraint on vxlan devices

On 01/06/16 at 01:33pm, David Wragg wrote:
> Allow the MTU of vxlan devices without an underlying device to be set to
> larger values (up to a maximum based on IP packet limits and vxlan
> overhead).
> 
> Previously, their MTUs could not be set to higher than the conventional
> ethernet value of 1500.  This is a very arbitrary value in the context
> of vxlan, and prevented such vxlan devices from being able to take
> advantage of jumbo frames etc.
> 
> The default MTU remains 1500, for compatibility.
> 
> Signed-off-by: David Wragg <david@...ve.works>

A remain of eth_change_mtu

> +	int max_mtu = 65535;

This should probably be represented as a new const DEV_MAX_MTU which
can be used by veth, tun, and virtio as well instead of hardcoding
this separately in each driver.

> +static int vxlan_change_mtu(struct net_device *dev, int new_mtu)
> +{
> +	struct vxlan_dev *vxlan = netdev_priv(dev);
> +	struct vxlan_rdst *dst = &vxlan->default_dst;
> +	struct net_device *lowerdev = __dev_get_by_index(vxlan->net,
> +							 dst->remote_ifindex);
> +	return __vxlan_change_mtu(dev, lowerdev, dst, new_mtu);

Any particular reason for the indirection?
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