seg6: fix SRv6 L2 tunnels to use IANA-assigned protocol number

The Internet Assigned Numbers Authority (IANA) has recently assigned
a protocol number value of 143 for Ethernet [1].

Before this assignment, encapsulation mechanisms such as Segment Routing
used the IPv6-NoNxt protocol number (59) to indicate that the encapsulated
payload is an Ethernet frame.

In this patch, we add the definition of the Ethernet protocol number to the
kernel headers and update the SRv6 L2 tunnels to use it.

[1] https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml

Signed-off-by: Paolo Lungaroni <paolo.lungaroni@cnit.it>
Reviewed-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Acked-by: Ahmed Abdelsalam <ahmed.abdelsalam@gssi.it>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/in.h

@@ -74,6 +74,8 @@ enum {
 #define IPPROTO_UDPLITE		IPPROTO_UDPLITE
   IPPROTO_MPLS = 137,		/* MPLS in IP (RFC 4023)		*/
 #define IPPROTO_MPLS		IPPROTO_MPLS
+  IPPROTO_ETHERNET = 143,	/* Ethernet-within-IPv6 Encapsulation	*/
+#define IPPROTO_ETHERNET	IPPROTO_ETHERNET
   IPPROTO_RAW = 255,		/* Raw IP packets			*/
 #define IPPROTO_RAW		IPPROTO_RAW
   IPPROTO_MPTCP = 262,		/* Multipath TCP connection		*/

net/ipv6/seg6_iptunnel.c

@@ -268,7 +268,7 @@ static int seg6_do_srh(struct sk_buff *skb)
 		skb_mac_header_rebuild(skb);
 		skb_push(skb, skb->mac_len);
 
-		err = seg6_do_srh_encap(skb, tinfo->srh, NEXTHDR_NONE);
+		err = seg6_do_srh_encap(skb, tinfo->srh, IPPROTO_ETHERNET);
 		if (err)
 			return err;
 

net/ipv6/seg6_local.c

@@ -282,7 +282,7 @@ static int input_action_end_dx2(struct sk_buff *skb,
 	struct net_device *odev;
 	struct ethhdr *eth;
 
-	if (!decap_and_validate(skb, NEXTHDR_NONE))
+	if (!decap_and_validate(skb, IPPROTO_ETHERNET))
 		goto drop;
 
 	if (!pskb_may_pull(skb, ETH_HLEN))