ip_tunnel: Emit events for post-register MTU changes

For tunnels created with IFLA_MTU, MTU of the netdevice is set by
rtnl_create_link() (called from rtnl_newlink()) before the device is
registered. However without IFLA_MTU that's not done.

rtnl_newlink() proceeds by calling struct rtnl_link_ops.newlink, which
via ip_tunnel_newlink() calls register_netdevice(), and that emits
NETDEV_REGISTER. Thus any listeners that inspect the netdevice get the
MTU of 0.

After ip_tunnel_newlink() corrects the MTU after registering the
netdevice, but since there's no event, the listeners don't get to know
about the MTU until something else happens--such as a NETDEV_UP event.
That's not ideal.

So instead of setting the MTU directly, go through dev_set_mtu(), which
takes care of distributing the necessary NETDEV_PRECHANGEMTU and
NETDEV_CHANGEMTU events.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 6d21068..7b85ffa 100644 (file)
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -362,13 +362,18 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
        struct ip_tunnel *nt;
        struct net_device *dev;
        int t_hlen;
+       int mtu;
+       int err;
 
        BUG_ON(!itn->fb_tunnel_dev);
        dev = __ip_tunnel_create(net, itn->fb_tunnel_dev->rtnl_link_ops, parms);
        if (IS_ERR(dev))
                return ERR_CAST(dev);
 
-       dev->mtu = ip_tunnel_bind_dev(dev);
+       mtu = ip_tunnel_bind_dev(dev);
+       err = dev_set_mtu(dev, mtu);
+       if (err)
+               goto err_dev_set_mtu;
 
        nt = netdev_priv(dev);
        t_hlen = nt->hlen + sizeof(struct iphdr);
@@ -376,6 +381,10 @@ static struct ip_tunnel *ip_tunnel_create(struct net *net,
        dev->max_mtu = 0xFFF8 - dev->hard_header_len - t_hlen;
        ip_tunnel_add(itn, nt);
        return nt;
+
+err_dev_set_mtu:
+       unregister_netdevice(dev);
+       return ERR_PTR(err);
 }
 
 int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
@@ -1102,17 +1111,24 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
        nt->fwmark = fwmark;
        err = register_netdevice(dev);
        if (err)
-               goto out;
+               goto err_register_netdevice;
 
        if (dev->type == ARPHRD_ETHER && !tb[IFLA_ADDRESS])
                eth_hw_addr_random(dev);
 
        mtu = ip_tunnel_bind_dev(dev);
-       if (!tb[IFLA_MTU])
-               dev->mtu = mtu;
+       if (!tb[IFLA_MTU]) {
+               err = dev_set_mtu(dev, mtu);
+               if (err)
+                       goto err_dev_set_mtu;
+       }
 
        ip_tunnel_add(itn, nt);
-out:
+       return 0;
+
+err_dev_set_mtu:
+       unregister_netdevice(dev);
+err_register_netdevice:
        return err;
 }
 EXPORT_SYMBOL_GPL(ip_tunnel_newlink);