path: root/net/ipv4/ip_tunnel.c
diff options
authorDavid Wragg <david@weave.works>2016-02-10 00:05:58 +0000
committerDavid S. Miller <davem@davemloft.net>2016-02-10 05:50:03 -0500
commit7e059158d57b79159eaf1f504825d19866ef2c42 (patch)
tree08f87eb3b0e08a48203e1ec95b2ddd00b91ca412 /net/ipv4/ip_tunnel.c
parentgeneve: Relax MTU constraints (diff)
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: David Wragg <david@weave.works> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_tunnel.c')
1 files changed, 17 insertions, 3 deletions
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index c7bd72e9b544..89e8861e05fc 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -943,17 +943,31 @@ done:
-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 ||
- new_mtu > 0xFFF8 - dev->hard_header_len - t_hlen)
+ 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;
+int ip_tunnel_change_mtu(struct net_device *dev, int new_mtu)
+ return __ip_tunnel_change_mtu(dev, new_mtu, true);
static void ip_tunnel_dev_free(struct net_device *dev)