datapath: ip6_gre: Split up ip6gre_changelink()

commit c8632fc30bb03aa0c3bd7bcce85355a10feb8149
Author: Petr Machata <petrm@mellanox.com>
Date:   Thu May 17 16:36:45 2018 +0200

    net: ip6_gre: Split up ip6gre_changelink()

    Extract from ip6gre_changelink() a reusable function
    ip6gre_changelink_common(). This will allow introduction of
    ERSPAN-specific _changelink() function with not a lot of code
    duplication.

    Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support")
    Signed-off-by: Petr Machata <petrm@mellanox.com>
    Acked-by: William Tu <u9012063@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Cc: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Reviewed-by: Greg Rose <gvrose8192@gmail.com>
Tested-by: Greg Rose <gvrose8192@gmail.com>

datapath/linux/compat/ip6_gre.c

@@ -2170,41 +2170,67 @@ static int rpl_ip6gre_newlink(struct net *src_net, struct net_device *dev,
 #define ip6gre_newlink rpl_ip6gre_newlink
 
 #ifdef HAVE_IP6GRE_EXTACK
-static int rpl_ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
-				 struct nlattr *data[],
-				 struct netlink_ext_ack *extack)
+static struct ip6_tnl *
+rpl_ip6gre_changelink_common(struct net_device *dev, struct nlattr *tb[],
+			 struct nlattr *data[], struct __ip6_tnl_parm *p_p,
+			 struct netlink_ext_ack *extack)
 #else
-static int rpl_ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
-				 struct nlattr *data[])
+static struct ip6_tnl *
+rpl_ip6gre_changelink_common(struct net_device *dev, struct nlattr *tb[],
+			 struct nlattr *data[], struct __ip6_tnl_parm *p_p)
 #endif
 {
 	struct ip6_tnl *t, *nt = netdev_priv(dev);
 	struct net *net = nt->net;
 	struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
-	struct __ip6_tnl_parm p;
 	struct ip_tunnel_encap ipencap;
 
 	if (dev == ign->fb_tunnel_dev)
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	if (ip6gre_netlink_encap_parms(data, &ipencap)) {
 		int err = ip6_tnl_encap_setup(nt, &ipencap);
 
 		if (err < 0)
-			return err;
+			return ERR_PTR(err);
 	}
 
-	ip6gre_netlink_parms(data, &p);
+	ip6gre_netlink_parms(data, p_p);
 
-	t = ip6gre_tunnel_locate(net, &p, 0);
+	t = ip6gre_tunnel_locate(net, p_p, 0);
 
 	if (t) {
 		if (t->dev != dev)
-			return -EEXIST;
+			return ERR_PTR(-EEXIST);
 	} else {
 		t = nt;
 	}
 
+	return t;
+}
+#define ip6gre_changelink_common rpl_ip6gre_changelink_common
+
+#ifdef HAVE_IP6GRE_EXTACK
+static int rpl_ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
+			     struct nlattr *data[],
+			     struct netlink_ext_ack *extack)
+#else
+static int rpl_ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
+			     struct nlattr *data[])
+#endif
+{
+	struct ip6gre_net *ign = net_generic(dev_net(dev), ip6gre_net_id);
+	struct __ip6_tnl_parm p;
+	struct ip6_tnl *t;
+
+#ifdef HAVE_IP6GRE_EXTACK
+	t = ip6gre_changelink_common(dev, tb, data, &p, extack);
+#else
+	t = ip6gre_changelink_common(dev, tb, data, &p);
+#endif
+	if (IS_ERR(t))
+		return PTR_ERR(t);
+
 	ip6gre_tunnel_unlink(ign, t);
 	ip6gre_tnl_change(t, &p, !tb[IFLA_MTU]);
 	ip6gre_tunnel_link(ign, t);