net: ip6_gre: do not report erspan_ver for ip6gre or ip6gretap

Report erspan version field to userspace in ip6gre_fill_info just for
erspan_v6 tunnels. Moreover report IFLA_GRE_ERSPAN_INDEX only for
erspan version 1.
The issue can be triggered with the following reproducer:

$ip link add name gre6 type ip6gre local 2001::1 remote 2002::2
$ip link set gre6 up
$ip -d link sh gre6
14: grep6@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1448 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/gre6 2001::1 peer 2002::2 promiscuity 0 minmtu 0 maxmtu 0
    ip6gre remote 2002::2 local 2001::1 hoplimit 64 encaplimit 4 tclass 0x00 flowlabel 0x00000 erspan_index 0 erspan_ver 0 addrgenmode eui64

Fixes: 94d7d8f2 ("ip6_gre: add erspan v2 support")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -2104,10 +2104,24 @@ static int ip6gre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	struct __ip6_tnl_parm *p = &t->parms;
 	__be16 o_flags = p->o_flags;
 
-	if ((p->erspan_ver == 1 || p->erspan_ver == 2) &&
-	    !p->collect_md)
+	if (p->erspan_ver == 1 || p->erspan_ver == 2) {
+		if (!p->collect_md)
 			o_flags |= TUNNEL_KEY;
 
+		if (nla_put_u8(skb, IFLA_GRE_ERSPAN_VER, p->erspan_ver))
+			goto nla_put_failure;
+
+		if (p->erspan_ver == 1) {
+			if (nla_put_u32(skb, IFLA_GRE_ERSPAN_INDEX, p->index))
+				goto nla_put_failure;
+		} else {
+			if (nla_put_u8(skb, IFLA_GRE_ERSPAN_DIR, p->dir))
+				goto nla_put_failure;
+			if (nla_put_u16(skb, IFLA_GRE_ERSPAN_HWID, p->hwid))
+				goto nla_put_failure;
+		}
+	}
+
 	if (nla_put_u32(skb, IFLA_GRE_LINK, p->link) ||
 	    nla_put_be16(skb, IFLA_GRE_IFLAGS,
 			 gre_tnl_flags_to_gre_flags(p->i_flags)) ||
@@ -2121,8 +2135,7 @@ static int ip6gre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	    nla_put_u8(skb, IFLA_GRE_ENCAP_LIMIT, p->encap_limit) ||
 	    nla_put_be32(skb, IFLA_GRE_FLOWINFO, p->flowinfo) ||
 	    nla_put_u32(skb, IFLA_GRE_FLAGS, p->flags) ||
-	    nla_put_u32(skb, IFLA_GRE_FWMARK, p->fwmark) ||
-	    nla_put_u32(skb, IFLA_GRE_ERSPAN_INDEX, p->index))
+	    nla_put_u32(skb, IFLA_GRE_FWMARK, p->fwmark))
 		goto nla_put_failure;
 
 	if (nla_put_u16(skb, IFLA_GRE_ENCAP_TYPE,
@@ -2140,19 +2153,6 @@ static int ip6gre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 			goto nla_put_failure;
 	}
 
-	if (nla_put_u8(skb, IFLA_GRE_ERSPAN_VER, p->erspan_ver))
-		goto nla_put_failure;
-
-	if (p->erspan_ver == 1) {
-		if (nla_put_u32(skb, IFLA_GRE_ERSPAN_INDEX, p->index))
-			goto nla_put_failure;
-	} else if (p->erspan_ver == 2) {
-		if (nla_put_u8(skb, IFLA_GRE_ERSPAN_DIR, p->dir))
-			goto nla_put_failure;
-		if (nla_put_u16(skb, IFLA_GRE_ERSPAN_HWID, p->hwid))
-			goto nla_put_failure;
-	}
-
 	return 0;
 
 nla_put_failure: