ip_gre: do not report erspan version on GRE interface

Although the type I ERSPAN is based on the barebones IP + GRE
encapsulation and no extra ERSPAN header. Report erspan version on GRE
interface looks unreasonable. Fix this by separating the erspan and gre
fill info.

IPv6 GRE does not have this info as IPv6 only supports erspan version
1 and 2.

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: f989d54 ("erspan: Add type I version 0 support.")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: William Tu <u9012063@gmail.com>
Link: https://lore.kernel.org/r/20221203032858.3130339-1-liuhangbin@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/ipv4/ip_gre.c

@@ -1492,24 +1492,6 @@ 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 <= 2) {
-		if (t->erspan_ver != 0 && !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 (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;
-		}
-	}
-
 	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)) ||
@@ -1550,6 +1532,34 @@ static int ipgre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	return -EMSGSIZE;
 }
 
+static int erspan_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+
+	if (t->erspan_ver <= 2) {
+		if (t->erspan_ver != 0 && !t->collect_md)
+			t->parms.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 (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 ipgre_fill_info(skb, dev);
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
 static void erspan_setup(struct net_device *dev)
 {
 	struct ip_tunnel *t = netdev_priv(dev);
@@ -1628,7 +1638,7 @@ static struct rtnl_link_ops erspan_link_ops __read_mostly = {
 	.changelink	= erspan_changelink,
 	.dellink	= ip_tunnel_dellink,
 	.get_size	= ipgre_get_size,
-	.fill_info	= ipgre_fill_info,
+	.fill_info	= erspan_fill_info,
 	.get_link_net	= ip_tunnel_get_link_net,
 };