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 sets
IFLA_GTP_CREATE_SOCKETS attribute, 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.

Note: GTP instance created with only this change applied, does
not handle GTP Echo Requests. This is implemented in the following
patch.

Signed-off-by: Wojciech Drewek <[e-mail]>
Signed-off-by: Tony Nguyen <[e-mail]>

drivers/net/gtp.c

···
 
 	struct sock		*sk0;
 	struct sock		*sk1u;
+	u8			sk_created;
 
 	struct net_device	*dev;
+	struct net		*net;
 
 	unsigned int		role;
 	unsigned int		hash_size;
···
 
 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.
···
 	kfree(gtp->tid_hash);
 }
 
+static struct sock *gtp_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 = htons(GTP0_PORT);
+	else if (type == UDP_ENCAP_GTP1U)
+		udp_conf.local_udp_port = htons(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_create_sockets(struct gtp_dev *gtp, struct nlattr *data[])
+{
+	struct sock *sk1u = NULL;
+	struct sock *sk0 = NULL;
+
+	sk0 = gtp_create_sock(UDP_ENCAP_GTP0, gtp);
+	if (IS_ERR(sk0))
+		return PTR_ERR(sk0);
+
+	sk1u = gtp_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;
+	gtp->sk0 = sk0;
+	gtp->sk1u = sk1u;
+
+	return 0;
+}
+
 static int gtp_newlink(struct net *src_net, struct net_device *dev,
 		       struct nlattr *tb[], struct nlattr *data[],
 		       struct netlink_ext_ack *extack)
 {
+	unsigned int role = GTP_ROLE_GGSN;
 	struct gtp_dev *gtp;
 	struct gtp_net *gn;
 	int hashsize, err;
-
-	if (!data[IFLA_GTP_FD0] && !data[IFLA_GTP_FD1])
-		return -EINVAL;
 
 	gtp = netdev_priv(dev);
 
···
 			hashsize = 1024;
 	}
 
+	if (data[IFLA_GTP_ROLE]) {
+		role = nla_get_u32(data[IFLA_GTP_ROLE]);
+		if (role > GTP_ROLE_SGSN)
+			return -EINVAL;
+	}
+	gtp->role = role;
+
+	gtp->net = src_net;
+
 	err = gtp_hashtable_new(gtp, hashsize);
 	if (err < 0)
 		return err;
 
-	err = gtp_encap_enable(gtp, data);
+	if (data[IFLA_GTP_CREATE_SOCKETS])
+		err = gtp_create_sockets(gtp, data);
+	else
+		err = gtp_encap_enable(gtp, data);
 	if (err < 0)
 		goto out_hashtable;
 
···
 	[IFLA_GTP_FD1]			= { .type = NLA_U32 },
 	[IFLA_GTP_PDP_HASHSIZE]		= { .type = NLA_U32 },
 	[IFLA_GTP_ROLE]			= { .type = NLA_U32 },
+	[IFLA_GTP_CREATE_SOCKETS]	= { .type = NLA_U8 },
 };
 
 static int gtp_validate(struct nlattr *tb[], struct nlattr *data[],
···
 {
 	struct sock *sk1u = NULL;
 	struct sock *sk0 = NULL;
-	unsigned int role = GTP_ROLE_GGSN;
+
+	if (!data[IFLA_GTP_FD0] && !data[IFLA_GTP_FD1])
+		return -EINVAL;
 
 	if (data[IFLA_GTP_FD0]) {
 		u32 fd0 = nla_get_u32(data[IFLA_GTP_FD0]);
···
 		}
 	}
 
-	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);
-			return -EINVAL;
-		}
-	}
-
 	gtp->sk0 = sk0;
 	gtp->sk1u = sk1u;
-	gtp->role = role;
 
 	return 0;
 }

include/uapi/linux/if_link.h

···
 	IFLA_GTP_FD1,
 	IFLA_GTP_PDP_HASHSIZE,
 	IFLA_GTP_ROLE,
+	IFLA_GTP_CREATE_SOCKETS,
 	__IFLA_GTP_MAX,
 };
 #define IFLA_GTP_MAX (__IFLA_GTP_MAX - 1)