ipv6: Refactor common ip6gre_tunnel_init codes

It is a prep work to fix the dst_entry refcnt bugs in ip6_tunnel.

This patch refactors some common init codes used by both
ip6gre_tunnel_init and ip6gre_tap_init.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -1245,7 +1245,7 @@ static void ip6gre_tunnel_setup(struct net_device *dev)
 	netif_keep_dst(dev);
 }
 
-static int ip6gre_tunnel_init(struct net_device *dev)
+static int ip6gre_tunnel_init_common(struct net_device *dev)
 {
 	struct ip6_tnl *tunnel;
 
@@ -1255,16 +1255,30 @@ static int ip6gre_tunnel_init(struct net_device *dev)
 	tunnel->net = dev_net(dev);
 	strcpy(tunnel->parms.name, dev->name);
 
+	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
+	if (!dev->tstats)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int ip6gre_tunnel_init(struct net_device *dev)
+{
+	struct ip6_tnl *tunnel;
+	int ret;
+
+	ret = ip6gre_tunnel_init_common(dev);
+	if (ret)
+		return ret;
+
+	tunnel = netdev_priv(dev);
+
 	memcpy(dev->dev_addr, &tunnel->parms.laddr, sizeof(struct in6_addr));
 	memcpy(dev->broadcast, &tunnel->parms.raddr, sizeof(struct in6_addr));
 
 	if (ipv6_addr_any(&tunnel->parms.raddr))
 		dev->header_ops = &ip6gre_header_ops;
 
-	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
-	if (!dev->tstats)
-		return -ENOMEM;
-
 	return 0;
 }
 
@@ -1460,19 +1474,16 @@ static void ip6gre_netlink_parms(struct nlattr *data[],
 static int ip6gre_tap_init(struct net_device *dev)
 {
 	struct ip6_tnl *tunnel;
+	int ret;
 
-	tunnel = netdev_priv(dev);
+	ret = ip6gre_tunnel_init_common(dev);
+	if (ret)
+		return ret;
 
-	tunnel->dev = dev;
-	tunnel->net = dev_net(dev);
-	strcpy(tunnel->parms.name, dev->name);
+	tunnel = netdev_priv(dev);
 
 	ip6gre_tnl_link_config(tunnel, 1);
 
-	dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
-	if (!dev->tstats)
-		return -ENOMEM;
-
 	return 0;
 }