gre: Fix dev_addr clobbering for gretap

Nathan Neulinger noticed that gretap devices get their MAC address
from the local IP address, which results in invalid MAC addresses
half of the time.

This is because gretap is still using the tunnel netdev ops rather
than the correct tap netdev ops struct.

This patch also fixes changelink to not clobber the MAC address
for the gretap case.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Tested-by: Nathan Neulinger <nneul@mst.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -1464,7 +1464,7 @@ static void ipgre_tap_setup(struct net_device *dev)
 
 	ether_setup(dev);
 
-	dev->netdev_ops		= &ipgre_netdev_ops;
+	dev->netdev_ops		= &ipgre_tap_netdev_ops;
 	dev->destructor 	= free_netdev;
 
 	dev->iflink		= 0;
@@ -1525,10 +1525,11 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
 		if (t->dev != dev)
 			return -EEXIST;
 	} else {
-		unsigned nflags = 0;
-
 		t = nt;
 
+		if (dev->type != ARPHRD_ETHER) {
+			unsigned nflags = 0;
+
 			if (ipv4_is_multicast(p.iph.daddr))
 				nflags = IFF_BROADCAST;
 			else if (p.iph.daddr)
@@ -1537,13 +1538,16 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
 			if ((dev->flags ^ nflags) &
 			    (IFF_POINTOPOINT | IFF_BROADCAST))
 				return -EINVAL;
+		}
 
 		ipgre_tunnel_unlink(ign, t);
 		t->parms.iph.saddr = p.iph.saddr;
 		t->parms.iph.daddr = p.iph.daddr;
 		t->parms.i_key = p.i_key;
+		if (dev->type != ARPHRD_ETHER) {
 			memcpy(dev->dev_addr, &p.iph.saddr, 4);
 			memcpy(dev->broadcast, &p.iph.daddr, 4);
+		}
 		ipgre_tunnel_link(ign, t);
 		netdev_state_change(dev);
 	}