1// SPDX-License-Identifier: GPL-2.0-only
2/* x_tables module for setting the IPv4/IPv6 DSCP field, Version 1.8
3 *
4 * (C) 2002 by Harald Welte <laforge@netfilter.org>
5 * based on ipt_FTOS.c (C) 2000 by Matthew G. Marsh <mgm@paktronix.com>
6 *
7 * See RFC2474 for a description of the DSCP field within the IP Header.
8*/
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/ip.h>
13#include <linux/ipv6.h>
14#include <net/dsfield.h>
15
16#include <linux/netfilter/x_tables.h>
17#include <linux/netfilter/xt_DSCP.h>
18
19MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
20MODULE_DESCRIPTION("Xtables: DSCP/TOS field modification");
21MODULE_LICENSE("GPL");
22MODULE_ALIAS("ipt_DSCP");
23MODULE_ALIAS("ip6t_DSCP");
24MODULE_ALIAS("ipt_TOS");
25MODULE_ALIAS("ip6t_TOS");
26
27#define XT_DSCP_ECN_MASK	3u
28
29static unsigned int
30dscp_tg(struct sk_buff *skb, const struct xt_action_param *par)
31{
32	const struct xt_DSCP_info *dinfo = par->targinfo;
33	u_int8_t dscp = ipv4_get_dsfield(ip_hdr(skb)) >> XT_DSCP_SHIFT;
34
35	if (dscp != dinfo->dscp) {
36		if (skb_ensure_writable(skb, sizeof(struct iphdr)))
37			return NF_DROP;
38
39		ipv4_change_dsfield(ip_hdr(skb), XT_DSCP_ECN_MASK,
40				    dinfo->dscp << XT_DSCP_SHIFT);
41
42	}
43	return XT_CONTINUE;
44}
45
46static unsigned int
47dscp_tg6(struct sk_buff *skb, const struct xt_action_param *par)
48{
49	const struct xt_DSCP_info *dinfo = par->targinfo;
50	u_int8_t dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> XT_DSCP_SHIFT;
51
52	if (dscp != dinfo->dscp) {
53		if (skb_ensure_writable(skb, sizeof(struct ipv6hdr)))
54			return NF_DROP;
55
56		ipv6_change_dsfield(ipv6_hdr(skb), XT_DSCP_ECN_MASK,
57				    dinfo->dscp << XT_DSCP_SHIFT);
58	}
59	return XT_CONTINUE;
60}
61
62static int dscp_tg_check(const struct xt_tgchk_param *par)
63{
64	const struct xt_DSCP_info *info = par->targinfo;
65
66	if (info->dscp > XT_DSCP_MAX)
67		return -EDOM;
68	return 0;
69}
70
71static unsigned int
72tos_tg(struct sk_buff *skb, const struct xt_action_param *par)
73{
74	const struct xt_tos_target_info *info = par->targinfo;
75	struct iphdr *iph = ip_hdr(skb);
76	u_int8_t orig, nv;
77
78	orig = ipv4_get_dsfield(iph);
79	nv   = (orig & ~info->tos_mask) ^ info->tos_value;
80
81	if (orig != nv) {
82		if (skb_ensure_writable(skb, sizeof(struct iphdr)))
83			return NF_DROP;
84		iph = ip_hdr(skb);
85		ipv4_change_dsfield(iph, 0, nv);
86	}
87
88	return XT_CONTINUE;
89}
90
91static unsigned int
92tos_tg6(struct sk_buff *skb, const struct xt_action_param *par)
93{
94	const struct xt_tos_target_info *info = par->targinfo;
95	struct ipv6hdr *iph = ipv6_hdr(skb);
96	u_int8_t orig, nv;
97
98	orig = ipv6_get_dsfield(iph);
99	nv   = (orig & ~info->tos_mask) ^ info->tos_value;
100
101	if (orig != nv) {
102		if (skb_ensure_writable(skb, sizeof(struct iphdr)))
103			return NF_DROP;
104		iph = ipv6_hdr(skb);
105		ipv6_change_dsfield(iph, 0, nv);
106	}
107
108	return XT_CONTINUE;
109}
110
111static struct xt_target dscp_tg_reg[] __read_mostly = {
112	{
113		.name		= "DSCP",
114		.family		= NFPROTO_IPV4,
115		.checkentry	= dscp_tg_check,
116		.target		= dscp_tg,
117		.targetsize	= sizeof(struct xt_DSCP_info),
118		.table		= "mangle",
119		.me		= THIS_MODULE,
120	},
121	{
122		.name		= "DSCP",
123		.family		= NFPROTO_IPV6,
124		.checkentry	= dscp_tg_check,
125		.target		= dscp_tg6,
126		.targetsize	= sizeof(struct xt_DSCP_info),
127		.table		= "mangle",
128		.me		= THIS_MODULE,
129	},
130	{
131		.name		= "TOS",
132		.revision	= 1,
133		.family		= NFPROTO_IPV4,
134		.table		= "mangle",
135		.target		= tos_tg,
136		.targetsize	= sizeof(struct xt_tos_target_info),
137		.me		= THIS_MODULE,
138	},
139	{
140		.name		= "TOS",
141		.revision	= 1,
142		.family		= NFPROTO_IPV6,
143		.table		= "mangle",
144		.target		= tos_tg6,
145		.targetsize	= sizeof(struct xt_tos_target_info),
146		.me		= THIS_MODULE,
147	},
148};
149
150static int __init dscp_tg_init(void)
151{
152	return xt_register_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));
153}
154
155static void __exit dscp_tg_exit(void)
156{
157	xt_unregister_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));
158}
159
160module_init(dscp_tg_init);
161module_exit(dscp_tg_exit);
162