gtp: Allow to create GTP device without FDs

Currently, when the user wants to create GTP device, he has to
provide file handles to the sockets created in userspace (IFLA_GTP_FD0,
IFLA_GTP_FD1). This behaviour is not ideal, considering the option of
adding support for GTP device creation through ip link. Ip link
application is not a good place to create such sockets.

This patch allows to create GTP device without providing
IFLA_GTP_FD0 and IFLA_GTP_FD1 arguments. If the user does not
provide file handles to the sockets, then GTP module takes care
of creating UDP sockets by itself. Sockets are created with the
commonly known UDP ports used for GTP protocol (GTP0_PORT and
GTP1U_PORT). In this case we don't have to provide encap_destroy
because no extra deinitialization is needed, everything is covered
by udp_tunnel_sock_release.

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>

drivers/net/gtp.c

@@ -66,8 +66,10 @@ struct gtp_dev {
 
 	struct sock		*sk0;
 	struct sock		*sk1u;
+	u8			sk_created;
 
 	struct net_device	*dev;
+	struct net		*net;
 
 	unsigned int		role;
 	unsigned int		hash_size;
@@ -320,8 +322,16 @@ static void gtp_encap_disable_sock(struct sock *sk)
 
 static void gtp_encap_disable(struct gtp_dev *gtp)
 {
-	gtp_encap_disable_sock(gtp->sk0);
-	gtp_encap_disable_sock(gtp->sk1u);
+	if (gtp->sk_created) {
+		udp_tunnel_sock_release(gtp->sk0->sk_socket);
+		udp_tunnel_sock_release(gtp->sk1u->sk_socket);
+		gtp->sk_created = false;
+		gtp->sk0 = NULL;
+		gtp->sk1u = NULL;
+	} else {
+		gtp_encap_disable_sock(gtp->sk0);
+		gtp_encap_disable_sock(gtp->sk1u);
+	}
 }
 
 /* UDP encapsulation receive handler. See net/ipv4/udp.c.
@@ -664,9 +674,6 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,
 	struct gtp_net *gn;
 	int hashsize, err;
 
-	if (!data[IFLA_GTP_FD0] && !data[IFLA_GTP_FD1])
-		return -EINVAL;
-
 	gtp = netdev_priv(dev);
 
 	if (!data[IFLA_GTP_PDP_HASHSIZE]) {
@@ -677,6 +684,8 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,
 			hashsize = 1024;
 	}
 
+	gtp->net = src_net;
+
 	err = gtp_hashtable_new(gtp, hashsize);
 	if (err < 0)
 		return err;
@@ -844,6 +853,38 @@ static struct sock *gtp_encap_enable_socket(int fd, int type,
 	return sk;
 }
 
+static struct sock *gtp_encap_create_sock(int type, struct gtp_dev *gtp)
+{
+	struct udp_tunnel_sock_cfg tuncfg = {};
+	struct udp_port_cfg udp_conf = {
+		.local_ip.s_addr	= htonl(INADDR_ANY),
+		.family			= AF_INET,
+	};
+	struct net *net = gtp->net;
+	struct socket *sock;
+	int err;
+
+	if (type == UDP_ENCAP_GTP0)
+		udp_conf.local_udp_port = ntohs(GTP0_PORT);
+	else if (type == UDP_ENCAP_GTP1U)
+		udp_conf.local_udp_port = ntohs(GTP1U_PORT);
+	else
+		return ERR_PTR(-EINVAL);
+
+	err = udp_sock_create(net, &udp_conf, &sock);
+	if (err)
+		return ERR_PTR(err);
+
+	tuncfg.sk_user_data = gtp;
+	tuncfg.encap_type = type;
+	tuncfg.encap_rcv = gtp_encap_recv;
+	tuncfg.encap_destroy = NULL;
+
+	setup_udp_tunnel_sock(net, sock, &tuncfg);
+
+	return sock->sk;
+}
+
 static int gtp_encap_enable(struct gtp_dev *gtp, struct nlattr *data[])
 {
 	struct sock *sk1u = NULL;
@@ -868,11 +909,30 @@ static int gtp_encap_enable(struct gtp_dev *gtp, struct nlattr *data[])
 		}
 	}
 
+	if (!data[IFLA_GTP_FD0] && !data[IFLA_GTP_FD1]) {
+		sk0 = gtp_encap_create_sock(UDP_ENCAP_GTP0, gtp);
+		if (IS_ERR(sk0))
+			return PTR_ERR(sk0);
+
+		sk1u = gtp_encap_create_sock(UDP_ENCAP_GTP1U, gtp);
+		if (IS_ERR(sk1u)) {
+			udp_tunnel_sock_release(sk0->sk_socket);
+			return PTR_ERR(sk1u);
+		}
+		gtp->sk_created = true;
+	}
+
 	if (data[IFLA_GTP_ROLE]) {
 		role = nla_get_u32(data[IFLA_GTP_ROLE]);
 		if (role > GTP_ROLE_SGSN) {
-			gtp_encap_disable_sock(sk0);
-			gtp_encap_disable_sock(sk1u);
+			if (gtp->sk_created) {
+				udp_tunnel_sock_release(sk0->sk_socket);
+				udp_tunnel_sock_release(sk1u->sk_socket);
+				gtp->sk_created = false;
+			} else {
+				gtp_encap_disable_sock(sk0);
+				gtp_encap_disable_sock(sk1u);
+			}
 			return -EINVAL;
 		}
 	}