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
71 struct l2tp_tunnel *tunnel; /* back pointer to tunnel context */
72 u32 session_id;
73 u32 peer_session_id;
74 u8 cookie[8];
75 int cookie_len;
76 u8 peer_cookie[8];
77 int peer_cookie_len;
78 u16 l2specific_type;
79 u16 hdr_len;
80 u32 nr; /* session NR state (receive) */
81 u32 ns; /* session NR state (send) */
82 struct sk_buff_head reorder_q; /* receive reorder queue */
83 u32 nr_max; /* max NR. Depends on tunnel */
84 u32 nr_window_size; /* NR window size */
85 u32 nr_oos; /* NR of last OOS packet */
86 int nr_oos_count; /* for OOS recovery */
87 int nr_oos_count_max;
88 struct list_head list; /* per-tunnel list node */
89 refcount_t ref_count;
90 struct hlist_node hlist; /* per-net session hlist */
91 unsigned long hlist_key; /* key for session hlist */
92 struct l2tp_session_coll_list *coll_list; /* session collision list */
93 struct list_head clist; /* for coll_list */
94
95 char name[L2TP_SESSION_NAME_MAX]; /* for logging */
96 char ifname[IFNAMSIZ];
97 unsigned int recv_seq:1; /* expect receive packets with sequence numbers? */
98 unsigned int send_seq:1; /* send packets with sequence numbers? */
99 unsigned int lns_mode:1; /* behave as LNS?
100 * LAC enables sequence numbers under LNS control.
101 */
102 int reorder_timeout; /* configured reorder timeout (in jiffies) */
103 int reorder_skip; /* set if skip to next nr */
104 enum l2tp_pwtype pwtype;
105 struct l2tp_stats stats;
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 unlisting 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 list 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 spinlock_t list_lock; /* write-protection for session_list */
164 bool acpt_newsess; /* indicates whether this tunnel accepts
165 * new sessions. Protected by list_lock.
166 */
167 struct list_head session_list; /* list of sessions */
168 u32 tunnel_id;
169 u32 peer_tunnel_id;
170 int version; /* 2=>L2TPv2, 3=>L2TPv3 */
171
172 char name[L2TP_TUNNEL_NAME_MAX]; /* for logging */
173 enum l2tp_encap_type encap;
174 struct l2tp_stats stats;
175
176 struct net *l2tp_net; /* the net we belong to */
177
178 refcount_t ref_count;
179 void (*old_sk_destruct)(struct sock *sk);
180 struct sock *sock; /* parent socket */
181 int fd; /* parent fd, if tunnel socket was created
182 * by userspace
183 */
184
185 struct work_struct del_work;
186 };
187
188 /* Pseudowire ops callbacks for use with the l2tp genetlink interface */
189 struct l2tp_nl_cmd_ops {
190 /* The pseudowire session create callback is responsible for creating a session
191 * instance for a specific pseudowire type.
192 * It must call l2tp_session_create and l2tp_session_register to register the
193 * session instance, as well as carry out any pseudowire-specific initialisation.
194 * It must return >= 0 on success, or an appropriate negative errno value on failure.
195 */
196 int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
197 u32 session_id, u32 peer_session_id,
198 struct l2tp_session_cfg *cfg);
199
200 /* The pseudowire session delete callback is responsible for initiating the deletion
201 * of a session instance.
202 * It must call l2tp_session_delete, as well as carry out any pseudowire-specific
203 * teardown actions.
204 */
205 void (*session_delete)(struct l2tp_session *session);
206 };
207
208 static inline void *l2tp_session_priv(struct l2tp_session *session)
209 {
210 return &session->priv[0];
211 }
212
213 /* Tunnel and session refcounts */
214 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel);
215 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel);
216 void l2tp_session_inc_refcount(struct l2tp_session *session);
217 void l2tp_session_dec_refcount(struct l2tp_session *session);
218
219 /* Tunnel and session lookup.
220 * These functions take a reference on the instances they return, so
221 * the caller must ensure that the reference is dropped appropriately.
222 */
223 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
224 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth);
225
226 struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk, u32 session_id);
227 struct l2tp_session *l2tp_v2_session_get(const struct net *net, u16 tunnel_id, u16 session_id);
228 struct l2tp_session *l2tp_session_get(const struct net *net, struct sock *sk, int pver,
229 u32 tunnel_id, u32 session_id);
230 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
231 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
232 const char *ifname);
233
234 /* Tunnel and session lifetime management.
235 * Creation of a new instance is a two-step process: create, then register.
236 * Destruction is triggered using the *_delete functions, and completes asynchronously.
237 */
238 int l2tp_tunnel_create(int fd, int version, u32 tunnel_id,
239 u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
240 struct l2tp_tunnel **tunnelp);
241 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
242 struct l2tp_tunnel_cfg *cfg);
243 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
244
245 struct l2tp_session *l2tp_session_create(int priv_size,
246 struct l2tp_tunnel *tunnel,
247 u32 session_id, u32 peer_session_id,
248 struct l2tp_session_cfg *cfg);
249 int l2tp_session_register(struct l2tp_session *session,
250 struct l2tp_tunnel *tunnel);
251 void l2tp_session_delete(struct l2tp_session *session);
252
253 /* Receive path helpers. If data sequencing is enabled for the session these
254 * functions handle queuing and reordering prior to passing packets to the
255 * pseudowire code to be passed to userspace.
256 */
257 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
258 unsigned char *ptr, unsigned char *optr, u16 hdrflags,
259 int length);
260 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
261
262 /* Transmit path helpers for sending packets over the tunnel socket. */
263 void l2tp_session_set_header_len(struct l2tp_session *session, int version);
264 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb);
265
266 /* Pseudowire management.
267 * Pseudowires should register with l2tp core on module init, and unregister
268 * on module exit.
269 */
270 int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops);
271 void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
272
273 /* IOCTL helper for IP encap modules. */
274 int l2tp_ioctl(struct sock *sk, int cmd, int *karg);
275
276 /* Extract the tunnel structure from a socket's sk_user_data pointer,
277 * validating the tunnel magic feather.
278 */
279 struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk);
280
281 static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
282 {
283 switch (session->l2specific_type) {
284 case L2TP_L2SPECTYPE_DEFAULT:
285 return 4;
286 case L2TP_L2SPECTYPE_NONE:
287 default:
288 return 0;
289 }
290 }
291
292 static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
293 {
294 struct dst_entry *dst;
295 u32 mtu;
296
297 dst = sk_dst_get(tunnel->sock);
298 if (!dst)
299 return 0;
300
301 mtu = dst_mtu(dst);
302 dst_release(dst);
303
304 return mtu;
305 }
306
307 #ifdef CONFIG_XFRM
308 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
309 {
310 struct sock *sk = tunnel->sock;
311
312 return sk && (rcu_access_pointer(sk->sk_policy[0]) ||
313 rcu_access_pointer(sk->sk_policy[1]));
314 }
315 #else
316 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
317 {
318 return false;
319 }
320 #endif
321
322 static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
323 unsigned char **ptr, unsigned char **optr)
324 {
325 int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);
326
327 if (opt_len > 0) {
328 int off = *ptr - *optr;
329
330 if (!pskb_may_pull(skb, off + opt_len))
331 return -1;
332
333 if (skb->data != *optr) {
334 *optr = skb->data;
335 *ptr = skb->data + off;
336 }
337 }
338
339 return 0;
340 }
341
342 #define MODULE_ALIAS_L2TP_PWTYPE(type) \
343 MODULE_ALIAS("net-l2tp-type-" __stringify(type))
344
345 #endif /* _L2TP_CORE_H_ */
346
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