gre: Fix wrong tpi->proto in WCCP

When dealing with WCCP in gre6 tunnel, it sets the wrong tpi->protocol,
that is, ETH_P_IP instead of ETH_P_IPV6 for the encapuslated traffic.

Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index d78e2ee..4c39f4f 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -62,7 +62,7 @@
 
 /* Fills in tpi and returns header length to be pulled. */
 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
-		     bool *csum_err)
+		     bool *csum_err, __be16 proto)
 {
 	const struct gre_base_hdr *greh;
 	__be32 *options;
@@ -109,11 +109,11 @@
 		tpi->seq = 0;
 	}
 	/* WCCP version 1 and 2 protocol decoding.
-	 * - Change protocol to IP
+	 * - Change protocol to IPv4/IPv6
 	 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
 	 */
 	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
-		tpi->proto = htons(ETH_P_IP);
+		tpi->proto = proto;
 		if ((*(u8 *)options & 0xF0) != 0x40)
 			hdr_len += 4;
 	}
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 2b267e7..aaeb478 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -222,7 +222,7 @@
 	struct tnl_ptk_info tpi;
 	bool csum_err = false;
 
-	if (gre_parse_header(skb, &tpi, &csum_err) < 0) {
+	if (gre_parse_header(skb, &tpi, &csum_err, htons(ETH_P_IP)) < 0) {
 		if (!csum_err)		/* ignore csum errors. */
 			return;
 	}
@@ -335,7 +335,7 @@
 	}
 #endif
 
-	hdr_len = gre_parse_header(skb, &tpi, &csum_err);
+	hdr_len = gre_parse_header(skb, &tpi, &csum_err, htons(ETH_P_IP));
 	if (hdr_len < 0)
 		goto drop;