1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /* L2TP internal definitions.
3  *
4  * Copyright (c) 2008,2009 Katalix Systems Ltd
5  */
6 #include <linux/refcount.h>
7 
8 #ifndef _L2TP_CORE_H_
9 #define _L2TP_CORE_H_
10 
11 #include <net/dst.h>
12 #include <net/sock.h>
13 
14 #ifdef CONFIG_XFRM
15 #include <net/xfrm.h>
16 #endif
17 
18 /* Random numbers used for internal consistency checks of tunnel and session structures */
19 #define L2TP_TUNNEL_MAGIC	0x42114DDA
20 #define L2TP_SESSION_MAGIC	0x0C04EB7D
21 
22 /* Per tunnel session hash table size */
23 #define L2TP_HASH_BITS	4
24 #define L2TP_HASH_SIZE	BIT(L2TP_HASH_BITS)
25 
26 /* System-wide session hash table size */
27 #define L2TP_HASH_BITS_2	8
28 #define L2TP_HASH_SIZE_2	BIT(L2TP_HASH_BITS_2)
29 
30 struct sk_buff;
31 
32 struct l2tp_stats {
33 	atomic_long_t		tx_packets;
34 	atomic_long_t		tx_bytes;
35 	atomic_long_t		tx_errors;
36 	atomic_long_t		rx_packets;
37 	atomic_long_t		rx_bytes;
38 	atomic_long_t		rx_seq_discards;
39 	atomic_long_t		rx_oos_packets;
40 	atomic_long_t		rx_errors;
41 	atomic_long_t		rx_cookie_discards;
42 	atomic_long_t		rx_invalid;
43 };
44 
45 struct l2tp_tunnel;
46 
47 /* L2TP session configuration */
48 struct l2tp_session_cfg {
49 	enum l2tp_pwtype	pw_type;
50 	unsigned int		recv_seq:1;	/* expect receive packets with sequence numbers? */
51 	unsigned int		send_seq:1;	/* send packets with sequence numbers? */
52 	unsigned int		lns_mode:1;	/* behave as LNS?
53 						 * LAC enables sequence numbers under LNS control.
54 						 */
55 	u16			l2specific_type; /* Layer 2 specific type */
56 	u8			cookie[8];	/* optional cookie */
57 	int			cookie_len;	/* 0, 4 or 8 bytes */
58 	u8			peer_cookie[8];	/* peer's cookie */
59 	int			peer_cookie_len; /* 0, 4 or 8 bytes */
60 	int			reorder_timeout; /* configured reorder timeout (in jiffies) */
61 	char			*ifname;
62 };
63 
64 /* Represents a session (pseudowire) instance.
65  * Tracks runtime state including cookies, dataplane packet sequencing, and IO statistics.
66  * Is linked into a per-tunnel session hashlist; and in the case of an L2TPv3 session into
67  * an additional per-net ("global") hashlist.
68  */
69 #define L2TP_SESSION_NAME_MAX 32
70 struct l2tp_session {
71 	int			magic;		/* should be L2TP_SESSION_MAGIC */
72 	long			dead;
73 
74 	struct l2tp_tunnel	*tunnel;	/* back pointer to tunnel context */
75 	u32			session_id;
76 	u32			peer_session_id;
77 	u8			cookie[8];
78 	int			cookie_len;
79 	u8			peer_cookie[8];
80 	int			peer_cookie_len;
81 	u16			l2specific_type;
82 	u16			hdr_len;
83 	u32			nr;		/* session NR state (receive) */
84 	u32			ns;		/* session NR state (send) */
85 	struct sk_buff_head	reorder_q;	/* receive reorder queue */
86 	u32			nr_max;		/* max NR. Depends on tunnel */
87 	u32			nr_window_size;	/* NR window size */
88 	u32			nr_oos;		/* NR of last OOS packet */
89 	int			nr_oos_count;	/* for OOS recovery */
90 	int			nr_oos_count_max;
91 	struct hlist_node	hlist;		/* hash list node */
92 	refcount_t		ref_count;
93 
94 	char			name[L2TP_SESSION_NAME_MAX]; /* for logging */
95 	char			ifname[IFNAMSIZ];
96 	unsigned int		recv_seq:1;	/* expect receive packets with sequence numbers? */
97 	unsigned int		send_seq:1;	/* send packets with sequence numbers? */
98 	unsigned int		lns_mode:1;	/* behave as LNS?
99 						 * LAC enables sequence numbers under LNS control.
100 						 */
101 	int			reorder_timeout; /* configured reorder timeout (in jiffies) */
102 	int			reorder_skip;	/* set if skip to next nr */
103 	enum l2tp_pwtype	pwtype;
104 	struct l2tp_stats	stats;
105 	struct hlist_node	global_hlist;	/* global hash list node */
106 
107 	/* Session receive handler for data packets.
108 	 * Each pseudowire implementation should implement this callback in order to
109 	 * handle incoming packets.  Packets are passed to the pseudowire handler after
110 	 * reordering, if data sequence numbers are enabled for the session.
111 	 */
112 	void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
113 
114 	/* Session close handler.
115 	 * Each pseudowire implementation may implement this callback in order to carry
116 	 * out pseudowire-specific shutdown actions.
117 	 * The callback is called by core after unhashing the session and purging its
118 	 * reorder queue.
119 	 */
120 	void (*session_close)(struct l2tp_session *session);
121 
122 	/* Session show handler.
123 	 * Pseudowire-specific implementation of debugfs session rendering.
124 	 * The callback is called by l2tp_debugfs.c after rendering core session
125 	 * information.
126 	 */
127 	void (*show)(struct seq_file *m, void *priv);
128 
129 	u8			priv[];		/* private data */
130 };
131 
132 /* L2TP tunnel configuration */
133 struct l2tp_tunnel_cfg {
134 	enum l2tp_encap_type	encap;
135 
136 	/* Used only for kernel-created sockets */
137 	struct in_addr		local_ip;
138 	struct in_addr		peer_ip;
139 #if IS_ENABLED(CONFIG_IPV6)
140 	struct in6_addr		*local_ip6;
141 	struct in6_addr		*peer_ip6;
142 #endif
143 	u16			local_udp_port;
144 	u16			peer_udp_port;
145 	unsigned int		use_udp_checksums:1,
146 				udp6_zero_tx_checksums:1,
147 				udp6_zero_rx_checksums:1;
148 };
149 
150 /* Represents a tunnel instance.
151  * Tracks runtime state including IO statistics.
152  * Holds the tunnel socket (either passed from userspace or directly created by the kernel).
153  * Maintains a hashlist of sessions belonging to the tunnel instance.
154  * Is linked into a per-net list of tunnels.
155  */
156 #define L2TP_TUNNEL_NAME_MAX 20
157 struct l2tp_tunnel {
158 	int			magic;		/* Should be L2TP_TUNNEL_MAGIC */
159 
160 	unsigned long		dead;
161 
162 	struct rcu_head rcu;
163 	rwlock_t		hlist_lock;	/* protect session_hlist */
164 	bool			acpt_newsess;	/* indicates whether this tunnel accepts
165 						 * new sessions. Protected by hlist_lock.
166 						 */
167 	struct hlist_head	session_hlist[L2TP_HASH_SIZE];
168 						/* hashed list of sessions, hashed by id */
169 	u32			tunnel_id;
170 	u32			peer_tunnel_id;
171 	int			version;	/* 2=>L2TPv2, 3=>L2TPv3 */
172 
173 	char			name[L2TP_TUNNEL_NAME_MAX]; /* for logging */
174 	enum l2tp_encap_type	encap;
175 	struct l2tp_stats	stats;
176 
177 	struct list_head	list;		/* list node on per-namespace list of tunnels */
178 	struct net		*l2tp_net;	/* the net we belong to */
179 
180 	refcount_t		ref_count;
181 	void (*old_sk_destruct)(struct sock *sk);
182 	struct sock		*sock;		/* parent socket */
183 	int			fd;		/* parent fd, if tunnel socket was created
184 						 * by userspace
185 						 */
186 
187 	struct work_struct	del_work;
188 };
189 
190 /* Pseudowire ops callbacks for use with the l2tp genetlink interface */
191 struct l2tp_nl_cmd_ops {
192 	/* The pseudowire session create callback is responsible for creating a session
193 	 * instance for a specific pseudowire type.
194 	 * It must call l2tp_session_create and l2tp_session_register to register the
195 	 * session instance, as well as carry out any pseudowire-specific initialisation.
196 	 * It must return >= 0 on success, or an appropriate negative errno value on failure.
197 	 */
198 	int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
199 			      u32 session_id, u32 peer_session_id,
200 			      struct l2tp_session_cfg *cfg);
201 
202 	/* The pseudowire session delete callback is responsible for initiating the deletion
203 	 * of a session instance.
204 	 * It must call l2tp_session_delete, as well as carry out any pseudowire-specific
205 	 * teardown actions.
206 	 */
207 	void (*session_delete)(struct l2tp_session *session);
208 };
209 
l2tp_session_priv(struct l2tp_session * session)210 static inline void *l2tp_session_priv(struct l2tp_session *session)
211 {
212 	return &session->priv[0];
213 }
214 
215 /* Tunnel and session refcounts */
216 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel);
217 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel);
218 void l2tp_session_inc_refcount(struct l2tp_session *session);
219 void l2tp_session_dec_refcount(struct l2tp_session *session);
220 
221 /* Tunnel and session lookup.
222  * These functions take a reference on the instances they return, so
223  * the caller must ensure that the reference is dropped appropriately.
224  */
225 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
226 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth);
227 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
228 					     u32 session_id);
229 
230 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id);
231 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
232 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
233 						const char *ifname);
234 
235 /* Tunnel and session lifetime management.
236  * Creation of a new instance is a two-step process: create, then register.
237  * Destruction is triggered using the *_delete functions, and completes asynchronously.
238  */
239 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id,
240 		       u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
241 		       struct l2tp_tunnel **tunnelp);
242 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
243 			 struct l2tp_tunnel_cfg *cfg);
244 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
245 
246 struct l2tp_session *l2tp_session_create(int priv_size,
247 					 struct l2tp_tunnel *tunnel,
248 					 u32 session_id, u32 peer_session_id,
249 					 struct l2tp_session_cfg *cfg);
250 int l2tp_session_register(struct l2tp_session *session,
251 			  struct l2tp_tunnel *tunnel);
252 void l2tp_session_delete(struct l2tp_session *session);
253 
254 /* Receive path helpers.  If data sequencing is enabled for the session these
255  * functions handle queuing and reordering prior to passing packets to the
256  * pseudowire code to be passed to userspace.
257  */
258 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
259 		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
260 		      int length);
261 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
262 
263 /* Transmit path helpers for sending packets over the tunnel socket. */
264 void l2tp_session_set_header_len(struct l2tp_session *session, int version);
265 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb);
266 
267 /* Pseudowire management.
268  * Pseudowires should register with l2tp core on module init, and unregister
269  * on module exit.
270  */
271 int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops);
272 void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
273 
274 /* IOCTL helper for IP encap modules. */
275 int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);
276 
277 /* Extract the tunnel structure from a socket's sk_user_data pointer,
278  * validating the tunnel magic feather.
279  */
280 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk);
281 
l2tp_get_l2specific_len(struct l2tp_session * session)282 static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
283 {
284 	switch (session->l2specific_type) {
285 	case L2TP_L2SPECTYPE_DEFAULT:
286 		return 4;
287 	case L2TP_L2SPECTYPE_NONE:
288 	default:
289 		return 0;
290 	}
291 }
292 
l2tp_tunnel_dst_mtu(const struct l2tp_tunnel * tunnel)293 static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
294 {
295 	struct dst_entry *dst;
296 	u32 mtu;
297 
298 	dst = sk_dst_get(tunnel->sock);
299 	if (!dst)
300 		return 0;
301 
302 	mtu = dst_mtu(dst);
303 	dst_release(dst);
304 
305 	return mtu;
306 }
307 
308 #ifdef CONFIG_XFRM
l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel * tunnel)309 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
310 {
311 	struct sock *sk = tunnel->sock;
312 
313 	return sk && (rcu_access_pointer(sk->sk_policy[0]) ||
314 		      rcu_access_pointer(sk->sk_policy[1]));
315 }
316 #else
l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel * tunnel)317 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
318 {
319 	return false;
320 }
321 #endif
322 
l2tp_v3_ensure_opt_in_linear(struct l2tp_session * session,struct sk_buff * skb,unsigned char ** ptr,unsigned char ** optr)323 static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
324 					       unsigned char **ptr, unsigned char **optr)
325 {
326 	int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);
327 
328 	if (opt_len > 0) {
329 		int off = *ptr - *optr;
330 
331 		if (!pskb_may_pull(skb, off + opt_len))
332 			return -1;
333 
334 		if (skb->data != *optr) {
335 			*optr = skb->data;
336 			*ptr = skb->data + off;
337 		}
338 	}
339 
340 	return 0;
341 }
342 
343 #define MODULE_ALIAS_L2TP_PWTYPE(type) \
344 	MODULE_ALIAS("net-l2tp-type-" __stringify(type))
345 
346 #endif /* _L2TP_CORE_H_ */
347