net: Fixed updating of ethertype in skb_mpls_push()

The skb_mpls_push was not updating ethertype of an ethernet packet if
the packet was originally received from a non ARPHRD_ETHER device.

In the below OVS data path flow, since the device corresponding to
port 7 is an l3 device (ARPHRD_NONE) the skb_mpls_push function does
not update the ethertype of the packet even though the previous
push_eth action had added an ethernet header to the packet.

recirc_id(0),in_port(7),eth_type(0x0800),ipv4(tos=0/0xfc,ttl=64,frag=no),
actions:push_eth(src=00:00:00:00:00:00,dst=00:00:00:00:00:00),
push_mpls(label=13,tc=0,ttl=64,bos=1,eth_type=0x8847),4

Fixes: 8822e270d697 ("net: core: move push MPLS functionality from OvS to core helper")
Signed-off-by: Martin Varghese <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/skbuff.h

···
 int skb_vlan_pop(struct sk_buff *skb);
 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
 int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
-		  int mac_len);
+		  int mac_len, bool ethernet);
 int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len,
 		 bool ethernet);
 int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse);

net/core/skbuff.c

···
  * Returns 0 on success, -errno otherwise.
  */
 int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
-		  int mac_len)
+		  int mac_len, bool ethernet)
 {
 	struct mpls_shim_hdr *lse;
 	int err;
···
 	lse->label_stack_entry = mpls_lse;
 	skb_postpush_rcsum(skb, lse, MPLS_HLEN);
 
-	if (skb->dev && skb->dev->type == ARPHRD_ETHER)
+	if (ethernet)
 		skb_mod_eth_type(skb, eth_hdr(skb), mpls_proto);
 	skb->protocol = mpls_proto;
 

net/openvswitch/actions.c

···
 	int err;
 
 	err = skb_mpls_push(skb, mpls->mpls_lse, mpls->mpls_ethertype,
-			    skb->mac_len);
+			    skb->mac_len,
+			    ovs_key_mac_proto(key) == MAC_PROTO_ETHERNET);
 	if (err)
 		return err;
 

net/sched/act_mpls.c

···
 		break;
 	case TCA_MPLS_ACT_PUSH:
 		new_lse = tcf_mpls_get_lse(NULL, p, !eth_p_mpls(skb->protocol));
-		if (skb_mpls_push(skb, new_lse, p->tcfm_proto, mac_len))
+		if (skb_mpls_push(skb, new_lse, p->tcfm_proto, mac_len,
+				  skb->dev && skb->dev->type == ARPHRD_ETHER))
 			goto drop;
 		break;
 	case TCA_MPLS_ACT_MODIFY: