erspan: build the header with the right proto according to erspan_ver

As said in draft-foschiano-erspan-03#section4:

   Different frame variants known as "ERSPAN Types" can be
   distinguished based on the GRE "Protocol Type" field value: Type I
   and II's value is 0x88BE while Type III's is 0x22EB [ETYPES].

So set it properly in erspan_xmit() according to erspan_ver. While at
it, also remove the unused parameter 'proto' in erspan_fb_xmit().

Fixes: 94d7d8f ("ip6_gre: add erspan v2 support")
Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -569,19 +569,18 @@ static void gre_fb_xmit(struct sk_buff *skb, struct net_device *dev,
 	dev->stats.tx_dropped++;
 }
 
-static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev,
-			   __be16 proto)
+static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 	struct ip_tunnel_info *tun_info;
 	const struct ip_tunnel_key *key;
 	struct erspan_metadata *md;
 	struct rtable *rt = NULL;
 	bool truncate = false;
+	__be16 df, proto;
 	struct flowi4 fl;
 	int tunnel_hlen;
 	int version;
-	__be16 df;
 	int nhoff;
 	int thoff;
 
@@ -626,18 +625,20 @@ static void erspan_fb_xmit(struct sk_buff *skb, struct net_device *dev,
 	if (version == 1) {
 		erspan_build_header(skb, ntohl(tunnel_id_to_key32(key->tun_id)),
 				    ntohl(md->u.index), truncate, true);
+		proto = htons(ETH_P_ERSPAN);
 	} else if (version == 2) {
 		erspan_build_header_v2(skb,
 				       ntohl(tunnel_id_to_key32(key->tun_id)),
 				       md->u.md2.dir,
 				       get_hwid(&md->u.md2),
 				       truncate, true);
+		proto = htons(ETH_P_ERSPAN2);
 	} else {
 		goto err_free_rt;
 	}
 
 	gre_build_header(skb, 8, TUNNEL_SEQ,
-			 htons(ETH_P_ERSPAN), 0, htonl(tunnel->o_seqno++));
+			 proto, 0, htonl(tunnel->o_seqno++));
 
 	df = key->tun_flags & TUNNEL_DONT_FRAGMENT ?  htons(IP_DF) : 0;
 
@@ -721,12 +722,13 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 	bool truncate = false;
+	__be16 proto;
 
 	if (!pskb_inet_may_pull(skb))
 		goto free_skb;
 
 	if (tunnel->collect_md) {
-		erspan_fb_xmit(skb, dev, skb->protocol);
+		erspan_fb_xmit(skb, dev);
 		return NETDEV_TX_OK;
 	}
 
@@ -742,19 +744,22 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
 	}
 
 	/* Push ERSPAN header */
-	if (tunnel->erspan_ver == 1)
+	if (tunnel->erspan_ver == 1) {
 		erspan_build_header(skb, ntohl(tunnel->parms.o_key),
 				    tunnel->index,
 				    truncate, true);
-	else if (tunnel->erspan_ver == 2)
+		proto = htons(ETH_P_ERSPAN);
+	} else if (tunnel->erspan_ver == 2) {
 		erspan_build_header_v2(skb, ntohl(tunnel->parms.o_key),
 				       tunnel->dir, tunnel->hwid,
 				       truncate, true);
-	else
+		proto = htons(ETH_P_ERSPAN2);
+	} else {
 		goto free_skb;
+	}
 
 	tunnel->parms.o_flags &= ~TUNNEL_KEY;
-	__gre_xmit(skb, dev, &tunnel->parms.iph, htons(ETH_P_ERSPAN));
+	__gre_xmit(skb, dev, &tunnel->parms.iph, proto);
 	return NETDEV_TX_OK;
 
 free_skb:

net/ipv6/ip6_gre.c

@@ -922,6 +922,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
 	__u8 dsfield = false;
 	struct flowi6 fl6;
 	int err = -EINVAL;
+	__be16 proto;
 	__u32 mtu;
 	int nhoff;
 	int thoff;
@@ -1035,8 +1036,9 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
 	}
 
 	/* Push GRE header. */
-	gre_build_header(skb, 8, TUNNEL_SEQ,
-			 htons(ETH_P_ERSPAN), 0, htonl(t->o_seqno++));
+	proto = (t->parms.erspan_ver == 1) ? htons(ETH_P_ERSPAN)
+					   : htons(ETH_P_ERSPAN2);
+	gre_build_header(skb, 8, TUNNEL_SEQ, proto, 0, htonl(t->o_seqno++));
 
 	/* TooBig packet may have updated dst->dev's mtu */
 	if (!t->parms.collect_md && dst && dst_mtu(dst) > dst->dev->mtu)