gso: Handle Trans-Ether-Bridging protocol in skb_network_protocol()

Rather than having logic to calculate inner protocol in every
tunnel gso handler move it to gso code. This simplifies code.

Cc: Eric Dumazet <[e-mail]>
Cc: Cong Wang <[e-mail]>
Cc: David S. Miller <[e-mail]>
Signed-off-by: Pravin B Shelar <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/dev.c

···
 	__be16 type = skb->protocol;
 	int vlan_depth = ETH_HLEN;
 
+	/* Tunnel gso handlers can set protocol to ethernet. */
+	if (type == htons(ETH_P_TEB)) {
+		struct ethhdr *eth;
+
+		if (unlikely(!pskb_may_pull(skb, sizeof(struct ethhdr))))
+			return 0;
+
+		eth = (struct ethhdr *)skb_mac_header(skb);
+		type = eth->h_proto;
+	}
+
 	while (type == htons(ETH_P_8021Q) || type == htons(ETH_P_8021AD)) {
 		struct vlan_hdr *vh;
 

net/ipv4/gre.c

···
 		csum = false;
 
 	/* setup inner skb. */
-	if (greh->protocol == htons(ETH_P_TEB)) {
-		struct ethhdr *eth = (struct ethhdr *)skb_inner_mac_header(skb);
-		skb->protocol = eth->h_proto;
-	} else {
-		skb->protocol = greh->protocol;
-	}
-
+	skb->protocol = greh->protocol;
 	skb->encapsulation = 0;
 
 	if (unlikely(!pskb_may_pull(skb, ghl)))

net/ipv4/udp.c

···
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	int mac_len = skb->mac_len;
 	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
-	struct ethhdr *inner_eth = (struct ethhdr *)skb_inner_mac_header(skb);
 	__be16 protocol = skb->protocol;
 	netdev_features_t enc_features;
 	int outer_hlen;
···
 	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, skb_inner_network_offset(skb));
 	skb->mac_len = skb_inner_network_offset(skb);
-	inner_eth = (struct ethhdr *)skb_mac_header(skb);
-	skb->protocol = inner_eth->h_proto;
+	skb->protocol = htons(ETH_P_TEB);
 
 	/* segment inner packet. */
 	enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);