/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2022 Alexander V. Chernikov <melifaro@FreeBSD.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef _NETLINK_NETLINK_MESSAGE_PARSER_H_
#define _NETLINK_NETLINK_MESSAGE_PARSER_H_

#ifdef _KERNEL

#include <sys/bitset.h>

/*
 * It is not meant to be included directly
 */

/* Parsing state */
struct linear_buffer {
        char            *base;  /* Base allocated memory pointer */
        uint32_t        offset; /* Currently used offset */
        uint32_t        size;   /* Total buffer size */
} __aligned(_Alignof(__max_align_t));

static inline void *
lb_alloc(struct linear_buffer *lb, int len)
{
        len = roundup2(len, _Alignof(__max_align_t));
        if (lb->offset + len > lb->size)
                return (NULL);
        void *data = (void *)(lb->base + lb->offset);
        lb->offset += len;
        return (data);
}

static inline void
lb_clear(struct linear_buffer *lb)
{
        memset(lb->base, 0, lb->size);
        lb->offset = 0;
}

#define NL_MAX_ERROR_BUF        128
#define SCRATCH_BUFFER_SIZE     (1024 + NL_MAX_ERROR_BUF)
struct nl_pstate {
        struct linear_buffer    lb;     /* Per-message scratch buffer */
        struct nlpcb            *nlp;   /* Originator socket */
        struct nl_writer        *nw;    /* Message writer to use */
        struct nlmsghdr         *hdr;   /* Current parsed message header */
        uint32_t                err_off; /* error offset from hdr start */
        int                     error;  /* last operation error */
        char                    *err_msg; /* Description of last error */
        struct nlattr           *cookie; /* NLA to return to the userspace */
        bool                    strict; /* Strict parsing required */
};

static inline void *
npt_alloc(struct nl_pstate *npt, int len)
{
        return (lb_alloc(&npt->lb, len));
}
#define npt_alloc_sockaddr(_npt, _len)  \
        ((struct sockaddr *)(npt_alloc((_npt), (_len))))

typedef int parse_field_f(void *hdr, struct nl_pstate *npt, void *target);
struct nlfield_parser {
        uint16_t        off_in;
        uint16_t        off_out;
        parse_field_f   *cb;
};
static const struct nlfield_parser nlf_p_empty[] = {};

int nlf_get_ifp(void *src, struct nl_pstate *npt, void *target);
int nlf_get_ifpz(void *src, struct nl_pstate *npt, void *target);
int nlf_get_u8(void *src, struct nl_pstate *npt, void *target);
int nlf_get_u16(void *src, struct nl_pstate *npt, void *target);
int nlf_get_u32(void *src, struct nl_pstate *npt, void *target);
int nlf_get_u8_u32(void *src, struct nl_pstate *npt, void *target);

struct nlattr_parser;
typedef int parse_attr_f(struct nlattr *attr, struct nl_pstate *npt,
    const void *arg, void *target);
struct nlattr_parser {
        uint16_t        type;   /* Attribute type */
        uint16_t        off;    /* field offset in the target structure */
        parse_attr_f    *cb;    /* parser function to call */
        const void      *arg;
};

typedef bool strict_parser_f(void *hdr, struct nl_pstate *npt);
typedef bool post_parser_f(void *parsed_attrs, struct nl_pstate *npt);

struct nlhdr_parser {
        u_int                   nl_hdr_off; /* aligned netlink header size */
        u_int                   out_hdr_off; /* target header size */
        u_int                   fp_size;
        u_int                   np_size;
        const struct nlfield_parser     *fp; /* array of header field parsers */
        const struct nlattr_parser      *np; /* array of attribute parsers */
        strict_parser_f         *sp; /* Pre-parse strict validation function */
        post_parser_f           *post_parse;
};

#define NL_DECLARE_PARSER_EXT(_name, _t, _sp, _fp, _np, _pp)    \
static const struct nlhdr_parser _name = {                      \
        .nl_hdr_off = sizeof(_t),                               \
        .fp = &((_fp)[0]),                                      \
        .np = &((_np)[0]),                                      \
        .fp_size = nitems(_fp),                                 \
        .np_size = nitems(_np),                                 \
        .sp = _sp,                                              \
        .post_parse = _pp,                                      \
}

#define NL_DECLARE_PARSER(_name, _t, _fp, _np)                  \
        NL_DECLARE_PARSER_EXT(_name, _t, NULL, _fp, _np, NULL)

#define NL_DECLARE_STRICT_PARSER(_name, _t, _sp, _fp, _np)      \
        NL_DECLARE_PARSER_EXT(_name, _t, _sp, _fp, _np, NULL)

#define NL_DECLARE_ARR_PARSER(_name, _t, _o, _fp, _np)  \
static const struct nlhdr_parser _name = {              \
        .nl_hdr_off = sizeof(_t),                       \
        .out_hdr_off = sizeof(_o),                      \
        .fp = &((_fp)[0]),                              \
        .np = &((_np)[0]),                              \
        .fp_size = nitems(_fp),                         \
        .np_size = nitems(_np),                         \
}

#define NL_DECLARE_ATTR_PARSER_EXT(_name, _np, _pp)     \
static const struct nlhdr_parser _name = {              \
        .np = &((_np)[0]),                              \
        .np_size = nitems(_np),                         \
        .post_parse = (_pp)                             \
}

#define NL_DECLARE_ATTR_PARSER(_name, _np)              \
        NL_DECLARE_ATTR_PARSER_EXT(_name, _np, NULL)

#define NL_ATTR_BMASK_SIZE      128
BITSET_DEFINE(nlattr_bmask, NL_ATTR_BMASK_SIZE);

void nl_get_attrs_bmask_raw(struct nlattr *nla_head, uint32_t len,
    struct nlattr_bmask *bm);
bool nl_has_attr(const struct nlattr_bmask *bm, uint16_t nla_type);

int nl_parse_attrs_raw(struct nlattr *nla_head, uint16_t len,
    const struct nlattr_parser *ps, u_int pslen, struct nl_pstate *npt,
    void *target);

int nlattr_get_flag(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_ip(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_bool(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_uint8(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_uint16(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_uint32(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_uint64(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_in_addr(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_in6_addr(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_ifp(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_ifpz(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_ipvia(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_chara(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_string(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_stringn(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_bytes(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_nla(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_nested(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);
int nlattr_get_nested_ptr(struct nlattr *nla, struct nl_pstate *npt,
    const void *arg, void *target);

bool nlmsg_report_err_msg(struct nl_pstate *npt, const char *fmt, ...)
        __printflike(2, 3);

#define NLMSG_REPORT_ERR_MSG(_npt, _fmt, ...) { \
        nlmsg_report_err_msg(_npt, _fmt, ## __VA_ARGS__); \
        NLP_LOG(LOG_DEBUG, (_npt)->nlp, _fmt, ## __VA_ARGS__); \
}

bool nlmsg_report_err_offset(struct nl_pstate *npt, uint32_t off);

void nlmsg_report_cookie(struct nl_pstate *npt, struct nlattr *nla);
void nlmsg_report_cookie_u32(struct nl_pstate *npt, uint32_t val);

/*
 * Have it inline so compiler can optimize field accesses into
 * the list of direct function calls without iteration.
 */
static inline int
nl_parse_header(void *hdr, uint32_t len, const struct nlhdr_parser *parser,
    struct nl_pstate *npt, void *target)
{
        int error;

        if (__predict_false(len < parser->nl_hdr_off)) {
                void *tmp_hdr;

                if (npt->strict) {
                        nlmsg_report_err_msg(npt,
                            "header too short: expected %d, got %d",
                            parser->nl_hdr_off, len);
                        return (EINVAL);
                }

                /*
                 * Compatibility with older applications:
                 * pretend there's a full header.
                 */
                tmp_hdr = npt_alloc(npt, parser->nl_hdr_off);
                if (tmp_hdr == NULL)
                        return (EINVAL);
                memcpy(tmp_hdr, hdr, len);
                hdr = tmp_hdr;
                len = parser->nl_hdr_off;
        }

        if (npt->strict && parser->sp != NULL && !parser->sp(hdr, npt))
                return (EINVAL);

        /* Extract fields first */
        for (u_int i = 0; i < parser->fp_size; i++) {
                const struct nlfield_parser *fp = &parser->fp[i];
                void *src = (char *)hdr + fp->off_in;
                void *dst = (char *)target + fp->off_out;

                error = fp->cb(src, npt, dst);
                if (error != 0)
                        return (error);
        }

        error = nl_parse_attrs_raw(
            (struct nlattr *)((char *)hdr + parser->nl_hdr_off),
            len - parser->nl_hdr_off, parser->np, parser->np_size, npt, target);

        if (parser->post_parse != NULL && error == 0) {
                if (!parser->post_parse(target, npt))
                        return (EINVAL);
        }

        return (error);
}

static inline int
nl_parse_nested(struct nlattr *nla, const struct nlhdr_parser *parser,
    struct nl_pstate *npt, void *target)
{
        return (nl_parse_attrs_raw((struct nlattr *)NLA_DATA(nla),
            NLA_DATA_LEN(nla), parser->np, parser->np_size, npt, target));
}

/*
 * Checks that attributes are sorted by attribute type.
 */
static inline void
nl_verify_parsers(const struct nlhdr_parser **parser, int count)
{
#ifdef INVARIANTS
        for (int i = 0; i < count; i++) {
                const struct nlhdr_parser *p = parser[i];
                int attr_type = 0;
                for (int j = 0; j < p->np_size; j++) {
                        MPASS(p->np[j].type > attr_type);
                        attr_type = p->np[j].type;

                        /* Recurse into nested objects. */
                        if (p->np[j].cb == nlattr_get_nested ||
                            p->np[j].cb == nlattr_get_nested_ptr) {
                                const struct nlhdr_parser *np =
                                    (const struct nlhdr_parser *)p->np[j].arg;
                                nl_verify_parsers(&np, 1);
                        }
                }
        }
#endif
}
void nl_verify_parsers(const struct nlhdr_parser **parser, int count);
#define NL_VERIFY_PARSERS(_p)   nl_verify_parsers((_p), nitems(_p))

static inline int
nl_parse_nlmsg(struct nlmsghdr *hdr, const struct nlhdr_parser *parser,
    struct nl_pstate *npt, void *target)
{
        return (nl_parse_header(hdr + 1, hdr->nlmsg_len - sizeof(*hdr), parser,
            npt, target));
}

static inline void
nl_get_attrs_bmask_nlmsg(struct nlmsghdr *hdr,
    const struct nlhdr_parser *parser, struct nlattr_bmask *bm)
{
        nl_get_attrs_bmask_raw(
            (struct nlattr *)((char *)(hdr + 1) + parser->nl_hdr_off),
            hdr->nlmsg_len - sizeof(*hdr) - parser->nl_hdr_off, bm);
}

#endif
#endif