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 spinlock_t hlist_lock; /* write-protection for 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, int *karg);
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