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Commit 72564b59 authored by David Wragg's avatar David Wragg Committed by David S. Miller
Browse files

vxlan: Relax MTU constraints 



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 vxlan devices from being able
to take advantage of jumbo frames etc.

The default MTU remains 1500, for compatibility.

Signed-off-by: default avatarDavid Wragg <david@weave.works>
Acked-by: default avatarRoopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 461547f3

drivers/net/vxlan.c

+25 −11
Original line number Diff line number Diff line
@@ -2367,29 +2367,43 @@ static void vxlan_set_multicast_list(struct net_device *dev) 
{

}



static int vxlan_change_mtu(struct net_device *dev, int new_mtu)

static int __vxlan_change_mtu(struct net_device *dev,

			      struct net_device *lowerdev,

			      struct vxlan_rdst *dst, int new_mtu, bool strict)

{

	struct vxlan_dev *vxlan = netdev_priv(dev);

	struct vxlan_rdst *dst = &vxlan->default_dst;

	struct net_device *lowerdev;

	int max_mtu;

	int max_mtu = IP_MAX_MTU;



	lowerdev = __dev_get_by_index(vxlan->net, dst->remote_ifindex);

	if (lowerdev == NULL)

		return eth_change_mtu(dev, new_mtu);

	if (lowerdev)

		max_mtu = lowerdev->mtu;



	if (dst->remote_ip.sa.sa_family == AF_INET6)

		max_mtu = lowerdev->mtu - VXLAN6_HEADROOM;

		max_mtu -= VXLAN6_HEADROOM;

	else

		max_mtu = lowerdev->mtu - VXLAN_HEADROOM;

		max_mtu -= VXLAN_HEADROOM;



	if (new_mtu < 68 || new_mtu > max_mtu)

	if (new_mtu < 68)

		return -EINVAL;



	if (new_mtu > max_mtu) {

		if (strict)

			return -EINVAL;



		new_mtu = max_mtu;

	}



	dev->mtu = new_mtu;

	return 0;

}



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, true);

}



static int egress_ipv4_tun_info(struct net_device *dev, struct sk_buff *skb,

				struct ip_tunnel_info *info,

				__be16 sport, __be16 dport)