// SPDX-License-Identifier: GPL-2.0-only
/* Xtables module to match packets using a BPF filter.
 * Copyright 2013 Google Inc.
 * Written by Willem de Bruijn <willemb@google.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/skbuff.h>
#include <linux/filter.h>
#include <linux/bpf.h>

#include <linux/netfilter/xt_bpf.h>
#include <linux/netfilter/x_tables.h>

MODULE_AUTHOR("Willem de Bruijn <willemb@google.com>");
MODULE_DESCRIPTION("Xtables: BPF filter match");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_bpf");
MODULE_ALIAS("ip6t_bpf");

static int __bpf_mt_check_bytecode(struct sock_filter *insns, __u16 len,
                                   struct bpf_prog **ret)
{
        struct sock_fprog_kern program;

        if (len > XT_BPF_MAX_NUM_INSTR)
                return -EINVAL;

        program.len = len;
        program.filter = insns;

        if (bpf_prog_create(ret, &program)) {
                pr_info_ratelimited("check failed: parse error\n");
                return -EINVAL;
        }

        return 0;
}

static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
{
        struct bpf_prog *prog;

        prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        *ret = prog;
        return 0;
}

static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
{
        if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
                return -EINVAL;

        *ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
        return PTR_ERR_OR_ZERO(*ret);
}

static int bpf_mt_check(const struct xt_mtchk_param *par)
{
        struct xt_bpf_info *info = par->matchinfo;

        return __bpf_mt_check_bytecode(info->bpf_program,
                                       info->bpf_program_num_elem,
                                       &info->filter);
}

static int bpf_mt_check_v1(const struct xt_mtchk_param *par)
{
        struct xt_bpf_info_v1 *info = par->matchinfo;

        if (info->mode == XT_BPF_MODE_BYTECODE)
                return __bpf_mt_check_bytecode(info->bpf_program,
                                               info->bpf_program_num_elem,
                                               &info->filter);
        else if (info->mode == XT_BPF_MODE_FD_ELF)
                return __bpf_mt_check_fd(info->fd, &info->filter);
        else if (info->mode == XT_BPF_MODE_PATH_PINNED)
                return __bpf_mt_check_path(info->path, &info->filter);
        else
                return -EINVAL;
}

static bool bpf_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_bpf_info *info = par->matchinfo;

        return bpf_prog_run(info->filter, skb);
}

static bool bpf_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_bpf_info_v1 *info = par->matchinfo;

        return !!bpf_prog_run_save_cb(info->filter, (struct sk_buff *) skb);
}

static void bpf_mt_destroy(const struct xt_mtdtor_param *par)
{
        const struct xt_bpf_info *info = par->matchinfo;

        bpf_prog_destroy(info->filter);
}

static void bpf_mt_destroy_v1(const struct xt_mtdtor_param *par)
{
        const struct xt_bpf_info_v1 *info = par->matchinfo;

        bpf_prog_destroy(info->filter);
}

static struct xt_match bpf_mt_reg[] __read_mostly = {
        {
                .name           = "bpf",
                .revision       = 0,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = bpf_mt_check,
                .match          = bpf_mt,
                .destroy        = bpf_mt_destroy,
                .matchsize      = sizeof(struct xt_bpf_info),
                .usersize       = offsetof(struct xt_bpf_info, filter),
                .me             = THIS_MODULE,
        },
        {
                .name           = "bpf",
                .revision       = 1,
                .family         = NFPROTO_UNSPEC,
                .checkentry     = bpf_mt_check_v1,
                .match          = bpf_mt_v1,
                .destroy        = bpf_mt_destroy_v1,
                .matchsize      = sizeof(struct xt_bpf_info_v1),
                .usersize       = offsetof(struct xt_bpf_info_v1, filter),
                .me             = THIS_MODULE,
        },
};

static int __init bpf_mt_init(void)
{
        return xt_register_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
}

static void __exit bpf_mt_exit(void)
{
        xt_unregister_matches(bpf_mt_reg, ARRAY_SIZE(bpf_mt_reg));
}

module_init(bpf_mt_init);
module_exit(bpf_mt_exit);