[PATCH RFC 2/2] veth: propagate bridge GSO to peer

[Stephen Hemminger]

This allows veth device in containers to see the GSO maximum
settings of the actual device being used for output.

Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
---
 drivers/net/veth.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index f5438d0978ca..0c9ce156943b 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -511,17 +511,89 @@ static struct rtnl_link_ops veth_link_ops = {
        .get_link_net   = veth_get_link_net,
 };
 
+/* When veth device is added to a bridge or other master device
+ * then reflect the GSO max values from the upper device
+ * to the other end of veth pair.
+ */
+static void veth_change_upper(struct net_device *dev,
+                     const struct netdev_notifier_changeupper_info *info)
+{
+       struct net_device *upper = info->upper_dev;
+       struct net_device *peer;
+       struct veth_priv *priv;
+
+       if (dev->netdev_ops != &veth_netdev_ops)
+               return;
+
+       priv = netdev_priv(dev);
+       peer = rtnl_dereference(priv->peer);
+       if (!peer)
+               return;
+
+       if (upper) {
+               peer->gso_max_segs = upper->gso_max_segs;
+               peer->gso_max_size = upper->gso_max_size;
+       } else {
+               peer->gso_max_segs = GSO_MAX_SEGS;
+               peer->gso_max_size = GSO_MAX_SIZE;
+       }
+}
+
+static void veth_change_upper_gso(struct net_device *upper)
+{
+       struct net_device *peer, *dev;
+       struct veth_priv *priv;
+
+       for_each_netdev(dev_net(upper), dev) {
+               if (dev->netdev_ops != &veth_netdev_ops)
+                       continue;
+               if (!netdev_has_upper_dev(dev, upper))
+                       continue;
+
+               priv = netdev_priv(dev);
+               peer = rtnl_dereference(priv->peer);
+               if (!peer)
+                       continue;
+               peer->gso_max_segs = upper->gso_max_segs;
+               peer->gso_max_size = upper->gso_max_size;
+       }
+}
+
+static int veth_netdev_event(struct notifier_block *this,
+                            unsigned long event, void *ptr)
+{
+       struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
+
+       /* Propagate the upper (bridge) device settings to peer */
+       switch (event) {
+       case NETDEV_CHANGEUPPER:
+               veth_change_upper(event_dev, ptr);
+               break;
+       case NETDEV_CHANGE_GSO_MAX:
+               veth_change_upper_gso(event_dev);
+               break;
+       }
+
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block veth_netdev_notifier = {
+       .notifier_call = veth_netdev_event,
+};
+
 /*
  * init/fini
  */
 
 static __init int veth_init(void)
 {
+       register_netdevice_notifier(&veth_netdev_notifier);
        return rtnl_link_register(&veth_link_ops);
 }
 
 static __exit void veth_exit(void)
 {
+       unregister_netdevice_notifier(&veth_netdev_notifier);
        rtnl_link_unregister(&veth_link_ops);
 }
 
-- 
2.11.0