/* SPDX-License-Identifier: GPL-2.0 */
/*
 * connection tracking helpers.
 *
 * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *      - generalize L3 protocol dependent part.
 *
 * Derived from include/linux/netfiter_ipv4/ip_conntrack_helper.h
 */

#ifndef _NF_CONNTRACK_HELPER_H
#define _NF_CONNTRACK_HELPER_H
#include <linux/refcount.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_extend.h>
#include <net/netfilter/nf_conntrack_expect.h>

#define NF_NAT_HELPER_PREFIX            "ip_nat_"
#define NF_NAT_HELPER_NAME(name)        NF_NAT_HELPER_PREFIX name
#define MODULE_ALIAS_NF_NAT_HELPER(name) \
        MODULE_ALIAS(NF_NAT_HELPER_NAME(name))

struct module;

enum nf_ct_helper_flags {
        NF_CT_HELPER_F_USERSPACE        = (1 << 0),
        NF_CT_HELPER_F_CONFIGURED       = (1 << 1),
};

#define NF_CT_HELPER_NAME_LEN   16

struct nf_conntrack_helper {
        struct hlist_node hnode;        /* Internal use. */

        char name[NF_CT_HELPER_NAME_LEN]; /* name of the module */
        refcount_t refcnt;
        struct module *me;              /* pointer to self */
        const struct nf_conntrack_expect_policy *expect_policy;

        /* Tuple of things we will help (compared against server response) */
        struct nf_conntrack_tuple tuple;

        /* Function to call when data passes; return verdict, or -1 to
           invalidate. */
        int (*help)(struct sk_buff *skb,
                    unsigned int protoff,
                    struct nf_conn *ct,
                    enum ip_conntrack_info conntrackinfo);

        void (*destroy)(struct nf_conn *ct);

        int (*from_nlattr)(struct nlattr *attr, struct nf_conn *ct);
        int (*to_nlattr)(struct sk_buff *skb, const struct nf_conn *ct);
        unsigned int expect_class_max;

        unsigned int flags;

        /* For user-space helpers: */
        unsigned int queue_num;
        /* length of userspace private data stored in nf_conn_help->data */
        u16 data_len;
        /* name of NAT helper module */
        char nat_mod_name[NF_CT_HELPER_NAME_LEN];
};

/* Must be kept in sync with the classes defined by helpers */
#define NF_CT_MAX_EXPECT_CLASSES        4

/* nf_conn feature for connections that have a helper */
struct nf_conn_help {
        /* Helper. if any */
        struct nf_conntrack_helper __rcu *helper;

        struct hlist_head expectations;

        /* Current number of expected connections */
        u8 expecting[NF_CT_MAX_EXPECT_CLASSES];

        /* private helper information. */
        char data[32] __aligned(8);
};

#define NF_CT_HELPER_BUILD_BUG_ON(structsize) \
        BUILD_BUG_ON((structsize) > sizeof_field(struct nf_conn_help, data))

struct nf_conntrack_helper *__nf_conntrack_helper_find(const char *name,
                                                       u16 l3num, u8 protonum);

struct nf_conntrack_helper *nf_conntrack_helper_try_module_get(const char *name,
                                                               u16 l3num,
                                                               u8 protonum);
void nf_conntrack_helper_put(struct nf_conntrack_helper *helper);

void nf_ct_helper_init(struct nf_conntrack_helper *helper,
                       u16 l3num, u16 protonum, const char *name,
                       u16 default_port, u16 spec_port, u32 id,
                       const struct nf_conntrack_expect_policy *exp_pol,
                       u32 expect_class_max,
                       int (*help)(struct sk_buff *skb, unsigned int protoff,
                                   struct nf_conn *ct,
                                   enum ip_conntrack_info ctinfo),
                       int (*from_nlattr)(struct nlattr *attr,
                                          struct nf_conn *ct),
                       struct module *module);

int nf_conntrack_helper_register(struct nf_conntrack_helper *);
void nf_conntrack_helper_unregister(struct nf_conntrack_helper *);

int nf_conntrack_helpers_register(struct nf_conntrack_helper *, unsigned int);
void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *,
                                     unsigned int);

struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp);

int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
                              gfp_t flags);

int nf_ct_helper(struct sk_buff *skb, struct nf_conn *ct,
                 enum ip_conntrack_info ctinfo, u16 proto);
int nf_ct_add_helper(struct nf_conn *ct, const char *name, u8 family,
                     u8 proto, bool nat, struct nf_conntrack_helper **hp);

void nf_ct_helper_destroy(struct nf_conn *ct);

static inline struct nf_conn_help *nfct_help(const struct nf_conn *ct)
{
        return nf_ct_ext_find(ct, NF_CT_EXT_HELPER);
}

static inline void *nfct_help_data(const struct nf_conn *ct)
{
        struct nf_conn_help *help;

        help = nf_ct_ext_find(ct, NF_CT_EXT_HELPER);

        return (void *)help->data;
}

int nf_conntrack_helper_init(void);
void nf_conntrack_helper_fini(void);

int nf_conntrack_broadcast_help(struct sk_buff *skb, struct nf_conn *ct,
                                enum ip_conntrack_info ctinfo,
                                unsigned int timeout);

struct nf_ct_helper_expectfn {
        struct list_head head;
        const char *name;
        void (*expectfn)(struct nf_conn *ct, struct nf_conntrack_expect *exp);
};

__printf(3,4)
void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
                      const char *fmt, ...);

void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n);
void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n);
struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_name(const char *name);
struct nf_ct_helper_expectfn *
nf_ct_helper_expectfn_find_by_symbol(const void *symbol);

extern struct hlist_head *nf_ct_helper_hash;
extern unsigned int nf_ct_helper_hsize;

struct nf_conntrack_nat_helper {
        struct list_head list;
        char mod_name[NF_CT_HELPER_NAME_LEN];   /* module name */
        struct module *module;                  /* pointer to self */
};

#define NF_CT_NAT_HELPER_INIT(name) \
        { \
        .mod_name = NF_NAT_HELPER_NAME(name), \
        .module = THIS_MODULE \
        }

void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat);
void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat);
int nf_nat_helper_try_module_get(const char *name, u16 l3num,
                                 u8 protonum);
void nf_nat_helper_put(struct nf_conntrack_helper *helper);
#endif /*_NF_CONNTRACK_HELPER_H*/