net: ip_gre: do not report erspan_ver for gre or gretap

Report erspan version field to userspace in ipgre_fill_info just for
erspan tunnels. The issue can be triggered with the following reproducer:

$ip link add name gre1 type gre local 192.168.0.1 remote 192.168.1.1
$ip link set dev gre1 up
$ip -d link sh gre1
13: gre1@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1476 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/gre 192.168.0.1 peer 192.168.1.1 promiscuity 0 minmtu 0 maxmtu 0
    gre remote 192.168.1.1 local 192.168.0.1 ttl inherit erspan_ver 0 addrgenmode eui64 numtxqueues 1 numrxqueues 1

Fixes: f551c91d ("net: erspan: introduce erspan v2 for ip_gre")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -1457,9 +1457,23 @@ static int ipgre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	struct ip_tunnel_parm *p = &t->parms;
 	__be16 o_flags = p->o_flags;
 
-	if ((t->erspan_ver == 1 || t->erspan_ver == 2) &&
-	    !t->collect_md)
-		o_flags |= TUNNEL_KEY;
+	if (t->erspan_ver == 1 || t->erspan_ver == 2) {
+		if (!t->collect_md)
+			o_flags |= TUNNEL_KEY;
+
+		if (nla_put_u8(skb, IFLA_GRE_ERSPAN_VER, t->erspan_ver))
+			goto nla_put_failure;
+
+		if (t->erspan_ver == 1) {
+			if (nla_put_u32(skb, IFLA_GRE_ERSPAN_INDEX, t->index))
+				goto nla_put_failure;
+		} else {
+			if (nla_put_u8(skb, IFLA_GRE_ERSPAN_DIR, t->dir))
+				goto nla_put_failure;
+			if (nla_put_u16(skb, IFLA_GRE_ERSPAN_HWID, t->hwid))
+				goto nla_put_failure;
+		}
+	}
 
 	if (nla_put_u32(skb, IFLA_GRE_LINK, p->link) ||
 	    nla_put_be16(skb, IFLA_GRE_IFLAGS,
@@ -1495,19 +1509,6 @@ static int ipgre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 			goto nla_put_failure;
 	}
 
-	if (nla_put_u8(skb, IFLA_GRE_ERSPAN_VER, t->erspan_ver))
-		goto nla_put_failure;
-
-	if (t->erspan_ver == 1) {
-		if (nla_put_u32(skb, IFLA_GRE_ERSPAN_INDEX, t->index))
-			goto nla_put_failure;
-	} else if (t->erspan_ver == 2) {
-		if (nla_put_u8(skb, IFLA_GRE_ERSPAN_DIR, t->dir))
-			goto nla_put_failure;
-		if (nla_put_u16(skb, IFLA_GRE_ERSPAN_HWID, t->hwid))
-			goto nla_put_failure;
-	}
-
 	return 0;
 
 nla_put_failure: