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

[ Upstream commit 7e059158d57b79159eaf1f504825d19866ef2c42 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 240620c5888a18538e2bb66d6b2bda6d0209fd1b..69e31e2a68fcc5782f8553eabbfe588158765d17 100644 (file)
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1356,11 +1356,21 @@ 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);
-       if (err) {
-               free_netdev(dev);
-               return ERR_PTR(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);
 }
 EXPORT_SYMBOL_GPL(geneve_dev_create_fb);
 

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 2f44bc5b20a41d1ac11b7fa5f1bd78078c0f4317..003780901628760e733b07b0fc7cf43e87e373f2 100644 (file)
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2776,6 +2776,7 @@ 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;
 
@@ -2796,9 +2797,7 @@ 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) {
@@ -2822,6 +2821,12 @@ 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

diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index 62a750a6a8f8cb32c9eb5d8d160aa94a20898473..af40bc586a1b6ae03ef751ce61276e58934e7406 100644 (file)
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -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,

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 7dc962b89fa166ea2b055b9eaab92fd4854b153b..3e4184088082f2b7708f16bc4bc86b80b888a90b 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1247,6 +1247,14 @@ 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);

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index ce30c8b72457fd425438ca675ff42cdd67e17505..3310ac75e3f394afff6359e36933f5aa2501b161 100644 (file)
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -948,17 +948,31 @@ done:
 }
 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 ||
-           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;
 }
+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)

diff --git a/net/openvswitch/vport-vxlan.c b/net/openvswitch/vport-vxlan.c
index d933cb89efac18651174ea34ae2cb3d6f23a1701..5eb7694348b5b82a3e80dc6262912eef441ec88e 100644 (file)
--- a/net/openvswitch/vport-vxlan.c
+++ b/net/openvswitch/vport-vxlan.c
@@ -91,6 +91,8 @@ static struct vport *vxlan_tnl_create(const struct vport_parms *parms)
        struct vxlan_config conf = {
                .no_share = true,
                .flags = VXLAN_F_COLLECT_METADATA | VXLAN_F_UDP_ZERO_CSUM6_RX,
+               /* Don't restrict the packets that can be sent by MTU */
+               .mtu = IP_MAX_MTU,
        };
 
        if (!options) {