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TOMOYO Linux Cross Reference
Linux/net/l2tp/l2tp_core.h

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  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         int                     debug;          /* bitmask of debug message categories */
 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 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[32];       /* 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                     debug;          /* bitmask of debug message categories */
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         int                     debug;          /* bitmask of debug message categories */
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 hashlist of sessions belonging to the tunnel instance.
155  * Is linked into a per-net list of tunnels.
156  */
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[20];       /* for logging */
174         int                     debug;          /* bitmask of debug message categories */
175         enum l2tp_encap_type    encap;
176         struct l2tp_stats       stats;
177 
178         struct list_head        list;           /* list node on per-namespace list of tunnels */
179         struct net              *l2tp_net;      /* the net we belong to */
180 
181         refcount_t              ref_count;
182         void (*old_sk_destruct)(struct sock *sk);
183         struct sock             *sock;          /* parent socket */
184         int                     fd;             /* parent fd, if tunnel socket was created
185                                                  * by userspace
186                                                  */
187 
188         struct work_struct      del_work;
189 };
190 
191 /* Pseudowire ops callbacks for use with the l2tp genetlink interface */
192 struct l2tp_nl_cmd_ops {
193         /* The pseudowire session create callback is responsible for creating a session
194          * instance for a specific pseudowire type.
195          * It must call l2tp_session_create and l2tp_session_register to register the
196          * session instance, as well as carry out any pseudowire-specific initialisation.
197          * It must return >= 0 on success, or an appropriate negative errno value on failure.
198          */
199         int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
200                               u32 session_id, u32 peer_session_id,
201                               struct l2tp_session_cfg *cfg);
202 
203         /* The pseudowire session delete callback is responsible for initiating the deletion
204          * of a session instance.
205          * It must call l2tp_session_delete, as well as carry out any pseudowire-specific
206          * teardown actions.
207          */
208         void (*session_delete)(struct l2tp_session *session);
209 };
210 
211 static inline void *l2tp_session_priv(struct l2tp_session *session)
212 {
213         return &session->priv[0];
214 }
215 
216 /* Tunnel and session refcounts */
217 void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel);
218 void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel);
219 void l2tp_session_inc_refcount(struct l2tp_session *session);
220 void l2tp_session_dec_refcount(struct l2tp_session *session);
221 
222 /* Tunnel and session lookup.
223  * These functions take a reference on the instances they return, so
224  * the caller must ensure that the reference is dropped appropriately.
225  */
226 struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
227 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth);
228 struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
229                                              u32 session_id);
230 
231 struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id);
232 struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
233 struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
234                                                 const char *ifname);
235 
236 /* Tunnel and session lifetime management.
237  * Creation of a new instance is a two-step process: create, then register.
238  * Destruction is triggered using the *_delete functions, and completes asynchronously.
239  */
240 int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
241                        u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
242                        struct l2tp_tunnel **tunnelp);
243 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
244                          struct l2tp_tunnel_cfg *cfg);
245 void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
246 
247 struct l2tp_session *l2tp_session_create(int priv_size,
248                                          struct l2tp_tunnel *tunnel,
249                                          u32 session_id, u32 peer_session_id,
250                                          struct l2tp_session_cfg *cfg);
251 int l2tp_session_register(struct l2tp_session *session,
252                           struct l2tp_tunnel *tunnel);
253 void l2tp_session_delete(struct l2tp_session *session);
254 
255 /* Receive path helpers.  If data sequencing is enabled for the session these
256  * functions handle queuing and reordering prior to passing packets to the
257  * pseudowire code to be passed to userspace.
258  */
259 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
260                       unsigned char *ptr, unsigned char *optr, u16 hdrflags,
261                       int length);
262 int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
263 
264 /* Transmit path helpers for sending packets over the tunnel socket. */
265 void l2tp_session_set_header_len(struct l2tp_session *session, int version);
266 int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb,
267                   int hdr_len);
268 
269 /* Pseudowire management.
270  * Pseudowires should register with l2tp core on module init, and unregister
271  * on module exit.
272  */
273 int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops);
274 void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
275 
276 /* IOCTL helper for IP encap modules. */
277 int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);
278 
279 static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
280 {
281         switch (session->l2specific_type) {
282         case L2TP_L2SPECTYPE_DEFAULT:
283                 return 4;
284         case L2TP_L2SPECTYPE_NONE:
285         default:
286                 return 0;
287         }
288 }
289 
290 static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
291 {
292         struct dst_entry *dst;
293         u32 mtu;
294 
295         dst = sk_dst_get(tunnel->sock);
296         if (!dst)
297                 return 0;
298 
299         mtu = dst_mtu(dst);
300         dst_release(dst);
301 
302         return mtu;
303 }
304 
305 #ifdef CONFIG_XFRM
306 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
307 {
308         struct sock *sk = tunnel->sock;
309 
310         return sk && (rcu_access_pointer(sk->sk_policy[0]) ||
311                       rcu_access_pointer(sk->sk_policy[1]));
312 }
313 #else
314 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
315 {
316         return false;
317 }
318 #endif
319 
320 static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
321                                                unsigned char **ptr, unsigned char **optr)
322 {
323         int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);
324 
325         if (opt_len > 0) {
326                 int off = *ptr - *optr;
327 
328                 if (!pskb_may_pull(skb, off + opt_len))
329                         return -1;
330 
331                 if (skb->data != *optr) {
332                         *optr = skb->data;
333                         *ptr = skb->data + off;
334                 }
335         }
336 
337         return 0;
338 }
339 
340 #define l2tp_printk(ptr, type, func, fmt, ...)                          \
341 do {                                                                    \
342         if (((ptr)->debug) & (type))                                    \
343                 func(fmt, ##__VA_ARGS__);                               \
344 } while (0)
345 
346 #define l2tp_warn(ptr, type, fmt, ...)                                  \
347         l2tp_printk(ptr, type, pr_warn, fmt, ##__VA_ARGS__)
348 #define l2tp_info(ptr, type, fmt, ...)                                  \
349         l2tp_printk(ptr, type, pr_info, fmt, ##__VA_ARGS__)
350 #define l2tp_dbg(ptr, type, fmt, ...)                                   \
351         l2tp_printk(ptr, type, pr_debug, fmt, ##__VA_ARGS__)
352 
353 #define MODULE_ALIAS_L2TP_PWTYPE(type) \
354         MODULE_ALIAS("net-l2tp-type-" __stringify(type))
355 
356 #endif /* _L2TP_CORE_H_ */
357 

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