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Commit 7e059158 authored by David Wragg's avatar David Wragg Committed by David S. Miller
Browse files

vxlan, gre, geneve: Set a large MTU on ovs-created tunnel devices 



Prior to 4.3, openvswitch tunnel vports (vxlan, gre and geneve) could
transmit vxlan packets of any size, constrained only by the ability to
send out the resulting packets.  4.3 introduced netdevs corresponding
to tunnel vports.  These netdevs have an MTU, which limits the size of
a packet that can be successfully encapsulated.  The default MTU
values are low (1500 or less), which is awkwardly small in the context
of physical networks supporting jumbo frames, and leads to a
conspicuous change in behaviour for userspace.

Instead, set the MTU on openvswitch-created netdevs to be the relevant
maximum (i.e. the maximum IP packet size minus any relevant overhead),
effectively restoring the behaviour prior to 4.3.

Signed-off-by: default avatarDavid Wragg <david@weave.works>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 55e5bfb5

drivers/net/geneve.c

+14 −4
Original line number Diff line number Diff line
@@ -1453,12 +1453,22 @@ struct net_device *geneve_dev_create_fb(struct net *net, const char *name, 


	err = geneve_configure(net, dev, &geneve_remote_unspec,

			       0, 0, 0, htons(dst_port), true, 0);

	if (err) {

	if (err)

		goto err;



	/* openvswitch users expect packet sizes to be unrestricted,

	 * so set the largest MTU we can.

	 */

	err = geneve_change_mtu(dev, IP_MAX_MTU);

	if (err)

		goto err;



	return dev;



 err:

	free_netdev(dev);

	return ERR_PTR(err);

}

	return dev;

}

EXPORT_SYMBOL_GPL(geneve_dev_create_fb);



static __net_init int geneve_init_net(struct net *net)

drivers/net/vxlan.c

+8 −3
Original line number Diff line number Diff line
@@ -2779,6 +2779,7 @@ static int vxlan_dev_configure(struct net *src_net, struct net_device *dev, 
	int err;

	bool use_ipv6 = false;

	__be16 default_port = vxlan->cfg.dst_port;

	struct net_device *lowerdev = NULL;



	vxlan->net = src_net;
@@ -2799,9 +2800,7 @@ static int vxlan_dev_configure(struct net *src_net, struct net_device *dev, 
	}



	if (conf->remote_ifindex) {

		struct net_device *lowerdev

			 = __dev_get_by_index(src_net, conf->remote_ifindex);



		lowerdev = __dev_get_by_index(src_net, conf->remote_ifindex);

		dst->remote_ifindex = conf->remote_ifindex;



		if (!lowerdev) {
@@ -2825,6 +2824,12 @@ static int vxlan_dev_configure(struct net *src_net, struct net_device *dev, 
		needed_headroom = lowerdev->hard_header_len;

	}



	if (conf->mtu) {

		err = __vxlan_change_mtu(dev, lowerdev, dst, conf->mtu, false);

		if (err)

			return err;

	}



	if (use_ipv6 || conf->flags & VXLAN_F_COLLECT_METADATA)

		needed_headroom += VXLAN6_HEADROOM;

	else

include/net/ip_tunnels.h

+1 −0
Original line number Diff line number Diff line
@@ -230,6 +230,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev, 
int ip_tunnel_ioctl(struct net_device *dev, struct ip_tunnel_parm *p, int cmd);

int ip_tunnel_encap(struct sk_buff *skb, struct ip_tunnel *t,

		    u8 *protocol, struct flowi4 *fl4);

int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict);

int ip_tunnel_change_mtu(struct net_device *dev, int new_mtu);



struct rtnl_link_stats64 *ip_tunnel_get_stats64(struct net_device *dev,

net/ipv4/ip_gre.c

+8 −0
Original line number Diff line number Diff line
@@ -1240,6 +1240,14 @@ struct net_device *gretap_fb_dev_create(struct net *net, const char *name, 
	err = ipgre_newlink(net, dev, tb, NULL);

	if (err < 0)

		goto out;



	/* openvswitch users expect packet sizes to be unrestricted,

	 * so set the largest MTU we can.

	 */

	err = __ip_tunnel_change_mtu(dev, IP_MAX_MTU, false);

	if (err)

		goto out;



	return dev;

out:

	free_netdev(dev);

net/ipv4/ip_tunnel.c

+17 −3
Original line number Diff line number Diff line
@@ -943,17 +943,31 @@ int ip_tunnel_ioctl(struct net_device *dev, struct ip_tunnel_parm *p, int cmd) 
}

EXPORT_SYMBOL_GPL(ip_tunnel_ioctl);



int ip_tunnel_change_mtu(struct net_device *dev, int new_mtu)

int __ip_tunnel_change_mtu(struct net_device *dev, int new_mtu, bool strict)

{

	struct ip_tunnel *tunnel = netdev_priv(dev);

	int t_hlen = tunnel->hlen + sizeof(struct iphdr);

	int max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;



	if (new_mtu < 68)

		return -EINVAL;



	if (new_mtu < 68 ||

	    new_mtu > 0xFFF8 - dev->hard_header_len - t_hlen)

	if (new_mtu > max_mtu) {

		if (strict)

			return -EINVAL;



		new_mtu = max_mtu;

	}



	dev->mtu = new_mtu;

	return 0;

}

EXPORT_SYMBOL_GPL(__ip_tunnel_change_mtu);



int ip_tunnel_change_mtu(struct net_device *dev, int new_mtu)

{

	return __ip_tunnel_change_mtu(dev, new_mtu, true);

}

EXPORT_SYMBOL_GPL(ip_tunnel_change_mtu);



static void ip_tunnel_dev_free(struct net_device *dev)