// SPDX-License-Identifier: GPL-2.0-only

  /* x_tables module for setting the IPv4/IPv6 DSCP field, Version 1.8
   *
   * (C) 2002 by Harald Welte <laforge@netfilter.org>
   * based on ipt_FTOS.c (C) 2000 by Matthew G. Marsh <mgm@paktronix.com>
   *

   * See RFC2474 for a description of the DSCP field within the IP Header.

  */

  #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 modification");

  MODULE_LICENSE("GPL");
  MODULE_ALIAS("ipt_DSCP");
  MODULE_ALIAS("ip6t_DSCP");

  MODULE_ALIAS("ipt_TOS");

  MODULE_ALIAS("ip6t_TOS");

  static unsigned int

  dscp_tg(struct sk_buff *skb, const struct xt_action_param *par)

  {

  	const struct xt_DSCP_info *dinfo = par->targinfo;

  	u_int8_t dscp = ipv4_get_dsfield(ip_hdr(skb)) >> XT_DSCP_SHIFT;

  
  	if (dscp != dinfo->dscp) {

  		if (skb_ensure_writable(skb, sizeof(struct iphdr)))

  			return NF_DROP;

  		ipv4_change_dsfield(ip_hdr(skb),
  				    (__force __u8)(~XT_DSCP_MASK),

  				    dinfo->dscp << XT_DSCP_SHIFT);
  
  	}
  	return XT_CONTINUE;
  }

  static unsigned int

  dscp_tg6(struct sk_buff *skb, const struct xt_action_param *par)

  {

  	const struct xt_DSCP_info *dinfo = par->targinfo;

  	u_int8_t dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> XT_DSCP_SHIFT;

  
  	if (dscp != dinfo->dscp) {

  		if (skb_ensure_writable(skb, sizeof(struct ipv6hdr)))

  			return NF_DROP;

  		ipv6_change_dsfield(ipv6_hdr(skb),
  				    (__force __u8)(~XT_DSCP_MASK),

  				    dinfo->dscp << XT_DSCP_SHIFT);
  	}
  	return XT_CONTINUE;
  }

  static int dscp_tg_check(const struct xt_tgchk_param *par)

  {

  	const struct xt_DSCP_info *info = par->targinfo;

  	if (info->dscp > XT_DSCP_MAX)

  		return -EDOM;

  	return 0;

  }

  static unsigned int

  tos_tg(struct sk_buff *skb, const struct xt_action_param *par)

  {

  	const struct xt_tos_target_info *info = par->targinfo;

  	struct iphdr *iph = ip_hdr(skb);
  	u_int8_t orig, nv;
  
  	orig = ipv4_get_dsfield(iph);

  	nv   = (orig & ~info->tos_mask) ^ info->tos_value;

  
  	if (orig != nv) {

  		if (skb_ensure_writable(skb, sizeof(struct iphdr)))

  			return NF_DROP;
  		iph = ip_hdr(skb);

  		ipv4_change_dsfield(iph, 0, nv);

  	}
  
  	return XT_CONTINUE;
  }
  
  static unsigned int

  tos_tg6(struct sk_buff *skb, const struct xt_action_param *par)

  {

  	const struct xt_tos_target_info *info = par->targinfo;

  	struct ipv6hdr *iph = ipv6_hdr(skb);
  	u_int8_t orig, nv;
  
  	orig = ipv6_get_dsfield(iph);

  	nv   = (orig & ~info->tos_mask) ^ info->tos_value;

  
  	if (orig != nv) {

  		if (skb_ensure_writable(skb, sizeof(struct iphdr)))

  			return NF_DROP;
  		iph = ipv6_hdr(skb);

  		ipv6_change_dsfield(iph, 0, nv);

  	}
  
  	return XT_CONTINUE;
  }

  static struct xt_target dscp_tg_reg[] __read_mostly = {

  	{
  		.name		= "DSCP",

  		.family		= NFPROTO_IPV4,

  		.checkentry	= dscp_tg_check,
  		.target		= dscp_tg,

  		.targetsize	= sizeof(struct xt_DSCP_info),
  		.table		= "mangle",
  		.me		= THIS_MODULE,
  	},
  	{
  		.name		= "DSCP",

  		.family		= NFPROTO_IPV6,

  		.checkentry	= dscp_tg_check,
  		.target		= dscp_tg6,

  		.targetsize	= sizeof(struct xt_DSCP_info),
  		.table		= "mangle",
  		.me		= THIS_MODULE,
  	},

  	{
  		.name		= "TOS",

  		.revision	= 1,

  		.family		= NFPROTO_IPV4,

  		.table		= "mangle",
  		.target		= tos_tg,
  		.targetsize	= sizeof(struct xt_tos_target_info),
  		.me		= THIS_MODULE,
  	},
  	{
  		.name		= "TOS",
  		.revision	= 1,

  		.family		= NFPROTO_IPV6,

  		.table		= "mangle",
  		.target		= tos_tg6,
  		.targetsize	= sizeof(struct xt_tos_target_info),
  		.me		= THIS_MODULE,
  	},

  };

  static int __init dscp_tg_init(void)

  {

  	return xt_register_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));

  }

  static void __exit dscp_tg_exit(void)

  {

  	xt_unregister_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));

  }

  module_init(dscp_tg_init);
  module_exit(dscp_tg_exit);