// SPDX-License-Identifier: GPL-2.0-only
/* IP tables module for matching the value of the IPv4/IPv6 DSCP field
 *
 * (C) 2002 by Harald Welte <laforge@netfilter.org>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <net/dsfield.h>

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

MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: DSCP/TOS field match");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_dscp");
MODULE_ALIAS("ip6t_dscp");
MODULE_ALIAS("ipt_tos");
MODULE_ALIAS("ip6t_tos");

static bool
dscp_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_dscp_info *info = par->matchinfo;
        u_int8_t dscp = ipv4_get_dsfield(ip_hdr(skb)) >> XT_DSCP_SHIFT;

        return (dscp == info->dscp) ^ !!info->invert;
}

static bool
dscp_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_dscp_info *info = par->matchinfo;
        u_int8_t dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> XT_DSCP_SHIFT;

        return (dscp == info->dscp) ^ !!info->invert;
}

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

        if (info->dscp > XT_DSCP_MAX)
                return -EDOM;

        return 0;
}

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

        if (xt_family(par) == NFPROTO_IPV4)
                return ((ip_hdr(skb)->tos & info->tos_mask) ==
                       info->tos_value) ^ !!info->invert;
        else
                return ((ipv6_get_dsfield(ipv6_hdr(skb)) & info->tos_mask) ==
                       info->tos_value) ^ !!info->invert;
}

static struct xt_match dscp_mt_reg[] __read_mostly = {
        {
                .name           = "dscp",
                .family         = NFPROTO_IPV4,
                .checkentry     = dscp_mt_check,
                .match          = dscp_mt,
                .matchsize      = sizeof(struct xt_dscp_info),
                .me             = THIS_MODULE,
        },
        {
                .name           = "dscp",
                .family         = NFPROTO_IPV6,
                .checkentry     = dscp_mt_check,
                .match          = dscp_mt6,
                .matchsize      = sizeof(struct xt_dscp_info),
                .me             = THIS_MODULE,
        },
        {
                .name           = "tos",
                .revision       = 1,
                .family         = NFPROTO_IPV4,
                .match          = tos_mt,
                .matchsize      = sizeof(struct xt_tos_match_info),
                .me             = THIS_MODULE,
        },
        {
                .name           = "tos",
                .revision       = 1,
                .family         = NFPROTO_IPV6,
                .match          = tos_mt,
                .matchsize      = sizeof(struct xt_tos_match_info),
                .me             = THIS_MODULE,
        },
};

static int __init dscp_mt_init(void)
{
        return xt_register_matches(dscp_mt_reg, ARRAY_SIZE(dscp_mt_reg));
}

static void __exit dscp_mt_exit(void)
{
        xt_unregister_matches(dscp_mt_reg, ARRAY_SIZE(dscp_mt_reg));
}

module_init(dscp_mt_init);
module_exit(dscp_mt_exit);