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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         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         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[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 
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, unsigned long arg);
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 
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 
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
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
317 static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
318 {
319         return false;
320 }
321 #endif
322 
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 

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