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 };
43
44 struct l2tp_tunnel;
45
46 /* L2TP session configuration */
47 struct l2tp_session_cfg {
48 enum l2tp_pwtype pw_type;
49 unsigned int recv_seq:1; /* expect receive packets with sequence numbers? */
50 unsigned int send_seq:1; /* send packets with sequence numbers? */
51 unsigned int lns_mode:1; /* behave as LNS?
52 * LAC enables sequence numbers under LNS control.
53 */
54 u16 l2specific_type; /* Layer 2 specific type */
55 u8 cookie[8]; /* optional cookie */
56 int cookie_len; /* 0, 4 or 8 bytes */
57 u8 peer_cookie[8]; /* peer's cookie */
58 int peer_cookie_len; /* 0, 4 or 8 bytes */
59 int reorder_timeout; /* configured reorder timeout (in jiffies) */
60 char *ifname;
61 };
62
63 /* Represents a session (pseudowire) instance.
64 * Tracks runtime state including cookies, dataplane packet sequencing, and IO statistics.
65 * Is linked into a per-tunnel session hashlist; and in the case of an L2TPv3 session into
66 * an additional per-net ("global") hashlist.
67 */
68 #define L2TP_SESSION_NAME_MAX 32
69 struct l2tp_session {
70 int magic; /* should be L2TP_SESSION_MAGIC */
71 long dead;
72
73 struct l2tp_tunnel *tunnel; /* back pointer to tunnel context */
74 u32 session_id;
75 u32 peer_session_id;
76 u8 cookie[8];
77 int cookie_len;
78 u8 peer_cookie[8];
79 int peer_cookie_len;
80 u16 l2specific_type;
81 u16 hdr_len;
82 u32 nr; /* session NR state (receive) */
83 u32 ns; /* session NR state (send) */
84 struct sk_buff_head reorder_q; /* receive reorder queue */
85 u32 nr_max; /* max NR. Depends on tunnel */
86 u32 nr_window_size; /* NR window size */
87 u32 nr_oos; /* NR of last OOS packet */
88 int nr_oos_count; /* for OOS recovery */
89 int nr_oos_count_max;
90 struct hlist_node hlist; /* hash list node */
91 refcount_t ref_count;
92
93 char name[L2TP_SESSION_NAME_MAX]; /* for logging */
94 char ifname[IFNAMSIZ];
95 unsigned int recv_seq:1; /* expect receive packets with sequence numbers? */
96 unsigned int send_seq:1; /* send packets with sequence numbers? */
97 unsigned int lns_mode:1; /* behave as LNS?
98 * LAC enables sequence numbers under LNS control.
99 */
100 int reorder_timeout; /* configured reorder timeout (in jiffies) */
101 int reorder_skip; /* set if skip to next nr */
102 enum l2tp_pwtype pwtype;
103 struct l2tp_stats stats;
104 struct hlist_node global_hlist; /* global hash list node */
105
106 /* Session receive handler for data packets.
107 * Each pseudowire implementation should implement this callback in order to
108 * handle incoming packets. Packets are passed to the pseudowire handler after
109 * reordering, if data sequence numbers are enabled for the session.
110 */
111 void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
112
113 /* Session close handler.
114 * Each pseudowire implementation may implement this callback in order to carry
115 * out pseudowire-specific shutdown actions.
116 * The callback is called by core after unhashing the session and purging its
117 * reorder queue.
118 */
119 void (*session_close)(struct l2tp_session *session);
120
121 /* Session show handler.
122 * Pseudowire-specific implementation of debugfs session rendering.
123 * The callback is called by l2tp_debugfs.c after rendering core session
124 * information.
125 */
126 void (*show)(struct seq_file *m, void *priv);
127
128 u8 priv[]; /* private data */
129 };
130
131 /* L2TP tunnel configuration */
132 struct l2tp_tunnel_cfg {
133 enum l2tp_encap_type encap;
134
135 /* Used only for kernel-created sockets */
136 struct in_addr local_ip;
137 struct in_addr peer_ip;
138 #if IS_ENABLED(CONFIG_IPV6)
139 struct in6_addr *local_ip6;
140 struct in6_addr *peer_ip6;
141 #endif
142 u16 local_udp_port;
143 u16 peer_udp_port;
144 unsigned int use_udp_checksums:1,
145 udp6_zero_tx_checksums:1,
146 udp6_zero_rx_checksums:1;
147 };
148
149 /* Represents a tunnel instance.
150 * Tracks runtime state including IO statistics.
151 * Holds the tunnel socket (either passed from userspace or directly created by the kernel).
152 * Maintains a hashlist of sessions belonging to the tunnel instance.
153 * Is linked into a per-net list of tunnels.
154 */
155 #define L2TP_TUNNEL_NAME_MAX 20
156 struct l2tp_tunnel {
157 int magic; /* Should be L2TP_TUNNEL_MAGIC */
158
159 unsigned long dead;
160
161 struct rcu_head rcu;
162 rwlock_t hlist_lock; /* protect session_hlist */
163 bool acpt_newsess; /* indicates whether this tunnel accepts
164 * new sessions. Protected by hlist_lock.
165 */
166 struct hlist_head session_hlist[L2TP_HASH_SIZE];
167 /* hashed list of sessions, hashed by id */
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 list_head list; /* list node on per-namespace list of tunnels */
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
l2tp_session_priv(struct l2tp_session * session)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 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
227 u32 session_id);
228
229 struct l2tp_session *l2tp_session_get(const struct net *net, 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, unsigned long arg);
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
l2tp_get_l2specific_len(struct l2tp_session * session)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
l2tp_tunnel_dst_mtu(const struct l2tp_tunnel * tunnel)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
l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel * tunnel)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
l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel * tunnel)316 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
317 {
318 return false;
319 }
320 #endif
321
l2tp_v3_ensure_opt_in_linear(struct l2tp_session * session,struct sk_buff * skb,unsigned char ** ptr,unsigned char ** optr)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
