/*
 * L2TP internal definitions.
 *
 * Copyright (c) 2008,2009 Katalix Systems Ltd
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/refcount.h>

#ifndef _L2TP_CORE_H_
#define _L2TP_CORE_H_

/* Just some random numbers */
#define L2TP_TUNNEL_MAGIC       0x42114DDA
#define L2TP_SESSION_MAGIC      0x0C04EB7D

/* Per tunnel, session hash table size */
#define L2TP_HASH_BITS  4
#define L2TP_HASH_SIZE  (1 << L2TP_HASH_BITS)

/* System-wide, session hash table size */
#define L2TP_HASH_BITS_2        8
#define L2TP_HASH_SIZE_2        (1 << L2TP_HASH_BITS_2)

struct sk_buff;

struct l2tp_stats {
        atomic_long_t           tx_packets;
        atomic_long_t           tx_bytes;
        atomic_long_t           tx_errors;
        atomic_long_t           rx_packets;
        atomic_long_t           rx_bytes;
        atomic_long_t           rx_seq_discards;
        atomic_long_t           rx_oos_packets;
        atomic_long_t           rx_errors;
        atomic_long_t           rx_cookie_discards;
};

struct l2tp_tunnel;

/* Describes a session. Contains information to determine incoming
 * packets and transmit outgoing ones.
 */
struct l2tp_session_cfg {
        enum l2tp_pwtype        pw_type;
        unsigned int            data_seq:2;     /* data sequencing level
                                                 * 0 => none, 1 => IP only,
                                                 * 2 => all
                                                 */
        unsigned int            recv_seq:1;     /* expect receive packets with
                                                 * sequence numbers? */
        unsigned int            send_seq:1;     /* send packets with sequence
                                                 * numbers? */
        unsigned int            lns_mode:1;     /* behave as LNS? LAC enables
                                                 * sequence numbers under
                                                 * control of LNS. */
        int                     debug;          /* bitmask of debug message
                                                 * categories */
        u16                     vlan_id;        /* VLAN pseudowire only */
        u16                     l2specific_type; /* Layer 2 specific type */
        u8                      cookie[8];      /* optional cookie */
        int                     cookie_len;     /* 0, 4 or 8 bytes */
        u8                      peer_cookie[8]; /* peer's cookie */
        int                     peer_cookie_len; /* 0, 4 or 8 bytes */
        int                     reorder_timeout; /* configured reorder timeout
                                                  * (in jiffies) */
        int                     mtu;
        int                     mru;
        char                    *ifname;
};

struct l2tp_session {
        int                     magic;          /* should be
                                                 * L2TP_SESSION_MAGIC */
        long                    dead;

        struct l2tp_tunnel      *tunnel;        /* back pointer to tunnel
                                                 * context */
        u32                     session_id;
        u32                     peer_session_id;
        u8                      cookie[8];
        int                     cookie_len;
        u8                      peer_cookie[8];
        int                     peer_cookie_len;
        u16                     l2specific_type;
        u16                     hdr_len;
        u32                     nr;             /* session NR state (receive) */
        u32                     ns;             /* session NR state (send) */
        struct sk_buff_head     reorder_q;      /* receive reorder queue */
        u32                     nr_max;         /* max NR. Depends on tunnel */
        u32                     nr_window_size; /* NR window size */
        u32                     nr_oos;         /* NR of last OOS packet */
        int                     nr_oos_count;   /* For OOS recovery */
        int                     nr_oos_count_max;
        struct hlist_node       hlist;          /* Hash list node */
        refcount_t              ref_count;

        char                    name[32];       /* for logging */
        char                    ifname[IFNAMSIZ];
        unsigned int            data_seq:2;     /* data sequencing level
                                                 * 0 => none, 1 => IP only,
                                                 * 2 => all
                                                 */
        unsigned int            recv_seq:1;     /* expect receive packets with
                                                 * sequence numbers? */
        unsigned int            send_seq:1;     /* send packets with sequence
                                                 * numbers? */
        unsigned int            lns_mode:1;     /* behave as LNS? LAC enables
                                                 * sequence numbers under
                                                 * control of LNS. */
        int                     debug;          /* bitmask of debug message
                                                 * categories */
        int                     reorder_timeout; /* configured reorder timeout
                                                  * (in jiffies) */
        int                     reorder_skip;   /* set if skip to next nr */
        int                     mtu;
        int                     mru;
        enum l2tp_pwtype        pwtype;
        struct l2tp_stats       stats;
        struct hlist_node       global_hlist;   /* Global hash list node */

        int (*build_header)(struct l2tp_session *session, void *buf);
        void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
        void (*session_close)(struct l2tp_session *session);
#if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
        void (*show)(struct seq_file *m, void *priv);
#endif
        uint8_t                 priv[0];        /* private data */
};

/* Describes the tunnel. It contains info to track all the associated
 * sessions so incoming packets can be sorted out
 */
struct l2tp_tunnel_cfg {
        int                     debug;          /* bitmask of debug message
                                                 * categories */
        enum l2tp_encap_type    encap;

        /* Used only for kernel-created sockets */
        struct in_addr          local_ip;
        struct in_addr          peer_ip;
#if IS_ENABLED(CONFIG_IPV6)
        struct in6_addr         *local_ip6;
        struct in6_addr         *peer_ip6;
#endif
        u16                     local_udp_port;
        u16                     peer_udp_port;
        unsigned int            use_udp_checksums:1,
                                udp6_zero_tx_checksums:1,
                                udp6_zero_rx_checksums:1;
};

struct l2tp_tunnel {
        int                     magic;          /* Should be L2TP_TUNNEL_MAGIC */

        unsigned long           dead;

        struct rcu_head rcu;
        rwlock_t                hlist_lock;     /* protect session_hlist */
        bool                    acpt_newsess;   /* Indicates whether this
                                                 * tunnel accepts new sessions.
                                                 * Protected by hlist_lock.
                                                 */
        struct hlist_head       session_hlist[L2TP_HASH_SIZE];
                                                /* hashed list of sessions,
                                                 * hashed by id */
        u32                     tunnel_id;
        u32                     peer_tunnel_id;
        int                     version;        /* 2=>L2TPv2, 3=>L2TPv3 */

        char                    name[20];       /* for logging */
        int                     debug;          /* bitmask of debug message
                                                 * categories */
        enum l2tp_encap_type    encap;
        struct l2tp_stats       stats;

        struct list_head        list;           /* Keep a list of all tunnels */
        struct net              *l2tp_net;      /* the net we belong to */

        refcount_t              ref_count;
        void (*old_sk_destruct)(struct sock *);
        struct sock             *sock;          /* Parent socket */
        int                     fd;             /* Parent fd, if tunnel socket
                                                 * was created by userspace */

        struct work_struct      del_work;

        uint8_t                 priv[0];        /* private data */
};

struct l2tp_nl_cmd_ops {
        int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
                              u32 session_id, u32 peer_session_id,
                              struct l2tp_session_cfg *cfg);
        int (*session_delete)(struct l2tp_session *session);
};

static inline void *l2tp_tunnel_priv(struct l2tp_tunnel *tunnel)
{
        return &tunnel->priv[0];
}

static inline void *l2tp_session_priv(struct l2tp_session *session)
{
        return &session->priv[0];
}

struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth);

void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);

struct l2tp_session *l2tp_session_get(const struct net *net,
                                      struct l2tp_tunnel *tunnel,
                                      u32 session_id);
struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
                                                const char *ifname);

int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
                       u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
                       struct l2tp_tunnel **tunnelp);
int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
                         struct l2tp_tunnel_cfg *cfg);

void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
struct l2tp_session *l2tp_session_create(int priv_size,
                                         struct l2tp_tunnel *tunnel,
                                         u32 session_id, u32 peer_session_id,
                                         struct l2tp_session_cfg *cfg);
int l2tp_session_register(struct l2tp_session *session,
                          struct l2tp_tunnel *tunnel);

void __l2tp_session_unhash(struct l2tp_session *session);
int l2tp_session_delete(struct l2tp_session *session);
void l2tp_session_free(struct l2tp_session *session);
void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
                      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
                      int length);
int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
void l2tp_session_set_header_len(struct l2tp_session *session, int version);

int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb,
                  int hdr_len);

int l2tp_nl_register_ops(enum l2tp_pwtype pw_type,
                         const struct l2tp_nl_cmd_ops *ops);
void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);

static inline void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel)
{
        refcount_inc(&tunnel->ref_count);
}

static inline void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel)
{
        if (refcount_dec_and_test(&tunnel->ref_count))
                l2tp_tunnel_free(tunnel);
}

/* Session reference counts. Incremented when code obtains a reference
 * to a session.
 */
static inline void l2tp_session_inc_refcount(struct l2tp_session *session)
{
        refcount_inc(&session->ref_count);
}

static inline void l2tp_session_dec_refcount(struct l2tp_session *session)
{
        if (refcount_dec_and_test(&session->ref_count))
                l2tp_session_free(session);
}

static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
{
        switch (session->l2specific_type) {
        case L2TP_L2SPECTYPE_DEFAULT:
                return 4;
        case L2TP_L2SPECTYPE_NONE:
        default:
                return 0;
        }
}

static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
                                               unsigned char **ptr, unsigned char **optr)
{
        int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);

        if (opt_len > 0) {
                int off = *ptr - *optr;

                if (!pskb_may_pull(skb, off + opt_len))
                        return -1;

                if (skb->data != *optr) {
                        *optr = skb->data;
                        *ptr = skb->data + off;
                }
        }

        return 0;
}

#define l2tp_printk(ptr, type, func, fmt, ...)                          \
do {                                                                    \
        if (((ptr)->debug) & (type))                                    \
                func(fmt, ##__VA_ARGS__);                               \
} while (0)

#define l2tp_warn(ptr, type, fmt, ...)                                  \
        l2tp_printk(ptr, type, pr_warn, fmt, ##__VA_ARGS__)
#define l2tp_info(ptr, type, fmt, ...)                                  \
        l2tp_printk(ptr, type, pr_info, fmt, ##__VA_ARGS__)
#define l2tp_dbg(ptr, type, fmt, ...)                                   \
        l2tp_printk(ptr, type, pr_debug, fmt, ##__VA_ARGS__)

#define MODULE_ALIAS_L2TP_PWTYPE(type) \
        MODULE_ALIAS("net-l2tp-type-" __stringify(type))

#endif /* _L2TP_CORE_H_ */