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
19 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
20 MODULE_DESCRIPTION("Xtables: DSCP/TOS field modification");
21 MODULE_LICENSE("GPL");
22 MODULE_ALIAS("ipt_DSCP");
23 MODULE_ALIAS("ip6t_DSCP");
24 MODULE_ALIAS("ipt_TOS");
25 MODULE_ALIAS("ip6t_TOS");
26
27 #define XT_DSCP_ECN_MASK 3u
28
29 static unsigned int
dscp_tg(struct sk_buff * skb,const struct xt_action_param * par)30 dscp_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
46 static unsigned int
dscp_tg6(struct sk_buff * skb,const struct xt_action_param * par)47 dscp_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
dscp_tg_check(const struct xt_tgchk_param * par)62 static 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
71 static unsigned int
tos_tg(struct sk_buff * skb,const struct xt_action_param * par)72 tos_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
91 static unsigned int
tos_tg6(struct sk_buff * skb,const struct xt_action_param * par)92 tos_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
111 static 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
dscp_tg_init(void)150 static int __init dscp_tg_init(void)
151 {
152 return xt_register_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));
153 }
154
dscp_tg_exit(void)155 static void __exit dscp_tg_exit(void)
156 {
157 xt_unregister_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));
158 }
159
160 module_init(dscp_tg_init);
161 module_exit(dscp_tg_exit);
162