Fix loopback traffic on link local IPv6 addresses.
The problem is the loopback interface can only receive packets with a single scope ID, namely the scope ID of the loopback interface. To mitigate this packets which use the scope ID are appearing as received by the real network interface, see "origifp" in the patch. The current code would drop packets which are designated for loopback which use a link-local scope ID in the destination address or source address, because they won't match the lo0's scope ID. To fix this restore the network interface pointer from the scope ID in the destination address for the problematic cases. See comments added in patch for a more detailed description.
MFC after: 1 week
Sponsored by: Mellanox Technologies