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 struct sk_buff;
23
24 struct l2tp_stats {
25 atomic_long_t tx_packets;
26 atomic_long_t tx_bytes;
27 atomic_long_t tx_errors;
28 atomic_long_t rx_packets;
29 atomic_long_t rx_bytes;
30 atomic_long_t rx_seq_discards;
31 atomic_long_t rx_oos_packets;
32 atomic_long_t rx_errors;
33 atomic_long_t rx_cookie_discards;
34 atomic_long_t rx_invalid;
35 };
36
37 struct l2tp_tunnel;
38
39 /* L2TP session configuration */
40 struct l2tp_session_cfg {
41 enum l2tp_pwtype pw_type;
42 unsigned int recv_seq:1; /* expect receive packets with sequence numbers? */
43 unsigned int send_seq:1; /* send packets with sequence numbers? */
44 unsigned int lns_mode:1; /* behave as LNS?
45 * LAC enables sequence numbers under LNS control.
46 */
47 u16 l2specific_type; /* Layer 2 specific type */
48 u8 cookie[8]; /* optional cookie */
49 int cookie_len; /* 0, 4 or 8 bytes */
50 u8 peer_cookie[8]; /* peer's cookie */
51 int peer_cookie_len; /* 0, 4 or 8 bytes */
52 int reorder_timeout; /* configured reorder timeout (in jiffies) */
53 char *ifname;
54 };
55
56 struct l2tp_session_coll_list {
57 spinlock_t lock; /* for access to list */
58 struct list_head list;
59 refcount_t ref_count;
60 };
61
62 /* Represents a session (pseudowire) instance.
63 * Tracks runtime state including cookies, dataplane packet sequencing, and IO statistics.
64 * Is linked into a per-tunnel session list and a per-net ("global") IDR tree.
65 */
66 #define L2TP_SESSION_NAME_MAX 32
67 struct l2tp_session {
68 int magic; /* should be L2TP_SESSION_MAGIC */
69 long dead;
70 struct rcu_head rcu;
71
72 struct l2tp_tunnel *tunnel; /* back pointer to tunnel context */
73 u32 session_id;
74 u32 peer_session_id;
75 u8 cookie[8];
76 int cookie_len;
77 u8 peer_cookie[8];
78 int peer_cookie_len;
79 u16 l2specific_type;
80 u16 hdr_len;
81 u32 nr; /* session NR state (receive) */
82 u32 ns; /* session NR state (send) */
83 struct sk_buff_head reorder_q; /* receive reorder queue */
84 u32 nr_max; /* max NR. Depends on tunnel */
85 u32 nr_window_size; /* NR window size */
86 u32 nr_oos; /* NR of last OOS packet */
87 int nr_oos_count; /* for OOS recovery */
88 int nr_oos_count_max;
89 struct list_head list; /* per-tunnel list node */
90 refcount_t ref_count;
91 struct hlist_node hlist; /* per-net session hlist */
92 unsigned long hlist_key; /* key for session hlist */
93 struct l2tp_session_coll_list *coll_list; /* session collision list */
94 struct list_head clist; /* for coll_list */
95
96 char name[L2TP_SESSION_NAME_MAX]; /* for logging */
97 char ifname[IFNAMSIZ];
98 unsigned int recv_seq:1; /* expect receive packets with sequence numbers? */
99 unsigned int send_seq:1; /* send packets with sequence numbers? */
100 unsigned int lns_mode:1; /* behave as LNS?
101 * LAC enables sequence numbers under LNS control.
102 */
103 int reorder_timeout; /* configured reorder timeout (in jiffies) */
104 int reorder_skip; /* set if skip to next nr */
105 enum l2tp_pwtype pwtype;
106 struct l2tp_stats stats;
107
108 /* Session receive handler for data packets.
109 * Each pseudowire implementation should implement this callback in order to
110 * handle incoming packets. Packets are passed to the pseudowire handler after
111 * reordering, if data sequence numbers are enabled for the session.
112 */
113 void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
114
115 /* Session close handler.
116 * Each pseudowire implementation may implement this callback in order to carry
117 * out pseudowire-specific shutdown actions.
118 * The callback is called by core after unlisting the session and purging its
119 * reorder queue.
120 */
121 void (*session_close)(struct l2tp_session *session);
122
123 /* Session show handler.
124 * Pseudowire-specific implementation of debugfs session rendering.
125 * The callback is called by l2tp_debugfs.c after rendering core session
126 * information.
127 */
128 void (*show)(struct seq_file *m, void *priv);
129
130 u8 priv[]; /* private data */
131 };
132
133 /* L2TP tunnel configuration */
134 struct l2tp_tunnel_cfg {
135 enum l2tp_encap_type encap;
136
137 /* Used only for kernel-created sockets */
138 struct in_addr local_ip;
139 struct in_addr peer_ip;
140 #if IS_ENABLED(CONFIG_IPV6)
141 struct in6_addr *local_ip6;
142 struct in6_addr *peer_ip6;
143 #endif
144 u16 local_udp_port;
145 u16 peer_udp_port;
146 unsigned int use_udp_checksums:1,
147 udp6_zero_tx_checksums:1,
148 udp6_zero_rx_checksums:1;
149 };
150
151 /* Represents a tunnel instance.
152 * Tracks runtime state including IO statistics.
153 * Holds the tunnel socket (either passed from userspace or directly created by the kernel).
154 * Maintains a list of sessions belonging to the tunnel instance.
155 * Is linked into a per-net list of tunnels.
156 */
157 #define L2TP_TUNNEL_NAME_MAX 20
158 struct l2tp_tunnel {
159 int magic; /* Should be L2TP_TUNNEL_MAGIC */
160
161 unsigned long dead;
162
163 struct rcu_head rcu;
164 spinlock_t list_lock; /* write-protection for session_list */
165 bool acpt_newsess; /* indicates whether this tunnel accepts
166 * new sessions. Protected by list_lock.
167 */
168 struct list_head session_list; /* list of sessions */
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 net *l2tp_net; /* the net we belong to */
178
179 refcount_t ref_count;
180 void (*old_sk_destruct)(struct sock *sk);
181 struct sock *sock; /* parent socket */
182 int fd; /* parent fd, if tunnel socket was created
183 * by userspace
184 */
185
186 struct work_struct del_work;
187 };
188
189 /* Pseudowire ops callbacks for use with the l2tp genetlink interface */
190 struct l2tp_nl_cmd_ops {
191 /* The pseudowire session create callback is responsible for creating a session
192 * instance for a specific pseudowire type.
193 * It must call l2tp_session_create and l2tp_session_register to register the
194 * session instance, as well as carry out any pseudowire-specific initialisation.
195 * It must return >= 0 on success, or an appropriate negative errno value on failure.
196 */
197 int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
198 u32 session_id, u32 peer_session_id,
199 struct l2tp_session_cfg *cfg);
200
201 /* The pseudowire session delete callback is responsible for initiating the deletion
202 * of a session instance.
203 * It must call l2tp_session_delete, as well as carry out any pseudowire-specific
204 * teardown actions.
205 */
206 void (*session_delete)(struct l2tp_session *session);
207 };
208
209 static inline void *l2tp_session_priv(struct l2tp_session *session)
210 {
211 return &session->priv[0];
212 }
213
214 /* Tunnel and session refcounts */
215 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel);
216 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel);
217 void l2tp_session_inc_refcount(struct l2tp_session *session);
218 void l2tp_session_dec_refcount(struct l2tp_session *session);
219
220 /* Tunnel and session lookup.
221 * These functions take a reference on the instances they return, so
222 * the caller must ensure that the reference is dropped appropriately.
223 */
224 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
225 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth);
226
227 struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk, u32 session_id);
228 struct l2tp_session *l2tp_v2_session_get(const struct net *net, u16 tunnel_id, u16 session_id);
229 struct l2tp_session *l2tp_session_get(const struct net *net, struct sock *sk, int pver,
230 u32 tunnel_id, 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 enum l2tp_encap_type encap);
266 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb);
267
268 /* Pseudowire management.
269 * Pseudowires should register with l2tp core on module init, and unregister
270 * on module exit.
271 */
272 int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops);
273 void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
274
275 /* IOCTL helper for IP encap modules. */
276 int l2tp_ioctl(struct sock *sk, int cmd, int *karg);
277
278 /* Extract the tunnel structure from a socket's sk_user_data pointer,
279 * validating the tunnel magic feather.
280 */
281 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk);
282
283 static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
284 {
285 switch (session->l2specific_type) {
286 case L2TP_L2SPECTYPE_DEFAULT:
287 return 4;
288 case L2TP_L2SPECTYPE_NONE:
289 default:
290 return 0;
291 }
292 }
293
294 static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
295 {
296 struct dst_entry *dst;
297 u32 mtu;
298
299 dst = sk_dst_get(tunnel->sock);
300 if (!dst)
301 return 0;
302
303 mtu = dst_mtu(dst);
304 dst_release(dst);
305
306 return mtu;
307 }
308
309 #ifdef CONFIG_XFRM
310 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
311 {
312 struct sock *sk = tunnel->sock;
313
314 return sk && (rcu_access_pointer(sk->sk_policy[0]) ||
315 rcu_access_pointer(sk->sk_policy[1]));
316 }
317 #else
318 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
319 {
320 return false;
321 }
322 #endif
323
324 static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
325 unsigned char **ptr, unsigned char **optr)
326 {
327 int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);
328
329 if (opt_len > 0) {
330 int off = *ptr - *optr;
331
332 if (!pskb_may_pull(skb, off + opt_len))
333 return -1;
334
335 if (skb->data != *optr) {
336 *optr = skb->data;
337 *ptr = skb->data + off;
338 }
339 }
340
341 return 0;
342 }
343
344 #define MODULE_ALIAS_L2TP_PWTYPE(type) \
345 MODULE_ALIAS("net-l2tp-type-" __stringify(type))
346
347 #endif /* _L2TP_CORE_H_ */
348
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.