net/ip_tunnels: Introduce tunnel_id_to_key32() and key32_to_tunnel_id()

Add utility functions to convert a 32 bits key into a 64 bits tunnel and
vice versa.
These functions will be used instead of cloning code in GRE and VXLAN,
and in tc act_iptunnel which will be introduced in a following patch in
this patchset.

Signed-off-by: Amir Vadai <amir@vadai.me>
Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Reviewed-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Acked-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 199dec0..4bfeb97 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1291,7 +1291,7 @@
 		struct metadata_dst *tun_dst;
 
 		tun_dst = udp_tun_rx_dst(skb, vxlan_get_sk_family(vs), TUNNEL_KEY,
-					 vxlan_vni_to_tun_id(vni), sizeof(*md));
+					 key32_to_tunnel_id(vni), sizeof(*md));
 
 		if (!tun_dst)
 			goto drop;
@@ -1945,7 +1945,7 @@
 			goto drop;
 		}
 		dst_port = info->key.tp_dst ? : vxlan->cfg.dst_port;
-		vni = vxlan_tun_id_to_vni(info->key.tun_id);
+		vni = tunnel_id_to_key32(info->key.tun_id);
 		remote_ip.sa.sa_family = ip_tunnel_info_af(info);
 		if (remote_ip.sa.sa_family == AF_INET) {
 			remote_ip.sin.sin_addr.s_addr = info->key.u.ipv4.dst;