ipv6: add struct hop_jumbo_hdr definition

Following patches will need to add and remove local IPv6 jumbogram
options to enable BIG TCP.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -151,6 +151,17 @@ struct frag_hdr {
 	__be32	identification;
 };
 
+/*
+ * Jumbo payload option, as described in RFC 2675 2.
+ */
+struct hop_jumbo_hdr {
+	u8	nexthdr;
+	u8	hdrlen;
+	u8	tlv_type;	/* IPV6_TLV_JUMBO, 0xC2 */
+	u8	tlv_len;	/* 4 */
+	__be32	jumbo_payload_len;
+};
+
 #define	IP6_MF		0x0001
 #define	IP6_OFFSET	0xFFF8