erspan: set erspan_ver to 1 by default when adding an erspan dev

After erspan_ver is introudced, if erspan_ver is not set in iproute, its
value will be left 0 by default. Since Commit 02f99df1 ("erspan: fix
invalid erspan version."), it has broken the traffic due to the version
check in erspan_xmit if users are not aware of 'erspan_ver' param, like
using an old version of iproute.

To fix this compatibility problem, it sets erspan_ver to 1 by default
when adding an erspan dev in erspan_setup. Note that we can't do it in
ipgre_netlink_parms, as this function is also used by ipgre_changelink.

Fixes: 02f99df1 ("erspan: fix invalid erspan version.")
Reported-by: NJianlin Shi <jishi@redhat.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -1508,11 +1508,14 @@ static int ipgre_fill_info(struct sk_buff *skb, const struct net_device *dev)
 
 static void erspan_setup(struct net_device *dev)
 {
+	struct ip_tunnel *t = netdev_priv(dev);
+
 	ether_setup(dev);
 	dev->netdev_ops = &erspan_netdev_ops;
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 	ip_tunnel_setup(dev, erspan_net_id);
+	t->erspan_ver = 1;
 }
 
 static const struct nla_policy ipgre_policy[IFLA_GRE_MAX + 1] = {

net/ipv6/ip6_gre.c

@@ -1778,6 +1778,7 @@ static void ip6gre_netlink_parms(struct nlattr *data[],
 	if (data[IFLA_GRE_COLLECT_METADATA])
 		parms->collect_md = true;
 
+	parms->erspan_ver = 1;
 	if (data[IFLA_GRE_ERSPAN_VER])
 		parms->erspan_ver = nla_get_u8(data[IFLA_GRE_ERSPAN_VER]);