[PPPOE]: Use ifindex instead of device pointer in key lookups.

Otherwise we can potentially try to dereference a NULL device
pointer in some cases.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_pppox.h b/include/linux/if_pppox.h
index 4fab3d0..e33ee76 100644
--- a/include/linux/if_pppox.h
+++ b/include/linux/if_pppox.h
@@ -114,6 +114,7 @@
 #ifdef __KERNEL__
 struct pppoe_opt {
 	struct net_device      *dev;	  /* device associated with socket*/
+	int			ifindex;  /* ifindex of device associated with socket */
 	struct pppoe_addr	pa;	  /* what this socket is bound to*/
 	struct sockaddr_pppox	relay;	  /* what socket data will be
 					     relayed to (PPPoE relaying) */
@@ -132,6 +133,7 @@
 	unsigned short		num;
 };
 #define pppoe_dev	proto.pppoe.dev
+#define pppoe_ifindex	proto.pppoe.ifindex
 #define pppoe_pa	proto.pppoe.pa
 #define pppoe_relay	proto.pppoe.relay