openvswitch: add processing of L3 packets

Support receiving, extracting flow key and sending of L3 packets (packets
without an Ethernet header).

Note that even after this patch, non-Ethernet interfaces are still not
allowed to be added to bridges. Similarly, netlink interface for sending and
receiving L3 packets to/from user space is not in place yet.

Based on previous versions by Lorand Jakab and Simon Horman.

Signed-off-by: Lorand Jakab <lojakab@cisco.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 898ed37..b6c8524 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -485,6 +485,25 @@
 {
 	int mtu = vport->dev->mtu;
 
+	switch (vport->dev->type) {
+	case ARPHRD_NONE:
+		if (mac_proto == MAC_PROTO_ETHERNET) {
+			skb_reset_network_header(skb);
+			skb_reset_mac_len(skb);
+			skb->protocol = htons(ETH_P_TEB);
+		} else if (mac_proto != MAC_PROTO_NONE) {
+			WARN_ON_ONCE(1);
+			goto drop;
+		}
+		break;
+	case ARPHRD_ETHER:
+		if (mac_proto != MAC_PROTO_ETHERNET)
+			goto drop;
+		break;
+	default:
+		goto drop;
+	}
+
 	if (unlikely(packet_length(skb, vport->dev) > mtu &&
 		     !skb_is_gso(skb))) {
 		net_warn_ratelimited("%s: dropped over-mtu packet: %d > %d\n",