net/l2tp/l2tp_core.h

   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
 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
 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_ */