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11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12#include <linux/in.h>
13#include <linux/ip.h>
14#include <net/ip.h>
15#include <linux/module.h>
16#include <linux/skbuff.h>
17#include <linux/tcp.h>
18
19#include <linux/netfilter/x_tables.h>
20#include <linux/netfilter/xt_ecn.h>
21#include <linux/netfilter_ipv4/ip_tables.h>
22#include <linux/netfilter_ipv6/ip6_tables.h>
23
24MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
25MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match");
26MODULE_LICENSE("GPL");
27MODULE_ALIAS("ipt_ecn");
28MODULE_ALIAS("ip6t_ecn");
29
30static bool match_tcp(const struct sk_buff *skb, struct xt_action_param *par)
31{
32 const struct xt_ecn_info *einfo = par->matchinfo;
33 struct tcphdr _tcph;
34 const struct tcphdr *th;
35
36
37
38
39 th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
40 if (th == NULL)
41 return false;
42
43 if (einfo->operation & XT_ECN_OP_MATCH_ECE) {
44 if (einfo->invert & XT_ECN_OP_MATCH_ECE) {
45 if (th->ece == 1)
46 return false;
47 } else {
48 if (th->ece == 0)
49 return false;
50 }
51 }
52
53 if (einfo->operation & XT_ECN_OP_MATCH_CWR) {
54 if (einfo->invert & XT_ECN_OP_MATCH_CWR) {
55 if (th->cwr == 1)
56 return false;
57 } else {
58 if (th->cwr == 0)
59 return false;
60 }
61 }
62
63 return true;
64}
65
66static inline bool match_ip(const struct sk_buff *skb,
67 const struct xt_ecn_info *einfo)
68{
69 return ((ip_hdr(skb)->tos & XT_ECN_IP_MASK) == einfo->ip_ect) ^
70 !!(einfo->invert & XT_ECN_OP_MATCH_IP);
71}
72
73static bool ecn_mt4(const struct sk_buff *skb, struct xt_action_param *par)
74{
75 const struct xt_ecn_info *info = par->matchinfo;
76
77 if (info->operation & XT_ECN_OP_MATCH_IP && !match_ip(skb, info))
78 return false;
79
80 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
81 !match_tcp(skb, par))
82 return false;
83
84 return true;
85}
86
87static int ecn_mt_check4(const struct xt_mtchk_param *par)
88{
89 const struct xt_ecn_info *info = par->matchinfo;
90 const struct ipt_ip *ip = par->entryinfo;
91
92 if (info->operation & XT_ECN_OP_MATCH_MASK)
93 return -EINVAL;
94
95 if (info->invert & XT_ECN_OP_MATCH_MASK)
96 return -EINVAL;
97
98 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
99 (ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) {
100 pr_info("cannot match TCP bits in rule for non-tcp packets\n");
101 return -EINVAL;
102 }
103
104 return 0;
105}
106
107static inline bool match_ipv6(const struct sk_buff *skb,
108 const struct xt_ecn_info *einfo)
109{
110 return (((ipv6_hdr(skb)->flow_lbl[0] >> 4) & XT_ECN_IP_MASK) ==
111 einfo->ip_ect) ^
112 !!(einfo->invert & XT_ECN_OP_MATCH_IP);
113}
114
115static bool ecn_mt6(const struct sk_buff *skb, struct xt_action_param *par)
116{
117 const struct xt_ecn_info *info = par->matchinfo;
118
119 if (info->operation & XT_ECN_OP_MATCH_IP && !match_ipv6(skb, info))
120 return false;
121
122 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
123 !match_tcp(skb, par))
124 return false;
125
126 return true;
127}
128
129static int ecn_mt_check6(const struct xt_mtchk_param *par)
130{
131 const struct xt_ecn_info *info = par->matchinfo;
132 const struct ip6t_ip6 *ip = par->entryinfo;
133
134 if (info->operation & XT_ECN_OP_MATCH_MASK)
135 return -EINVAL;
136
137 if (info->invert & XT_ECN_OP_MATCH_MASK)
138 return -EINVAL;
139
140 if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
141 (ip->proto != IPPROTO_TCP || ip->invflags & IP6T_INV_PROTO)) {
142 pr_info("cannot match TCP bits in rule for non-tcp packets\n");
143 return -EINVAL;
144 }
145
146 return 0;
147}
148
149static struct xt_match ecn_mt_reg[] __read_mostly = {
150 {
151 .name = "ecn",
152 .family = NFPROTO_IPV4,
153 .match = ecn_mt4,
154 .matchsize = sizeof(struct xt_ecn_info),
155 .checkentry = ecn_mt_check4,
156 .me = THIS_MODULE,
157 },
158 {
159 .name = "ecn",
160 .family = NFPROTO_IPV6,
161 .match = ecn_mt6,
162 .matchsize = sizeof(struct xt_ecn_info),
163 .checkentry = ecn_mt_check6,
164 .me = THIS_MODULE,
165 },
166};
167
168static int __init ecn_mt_init(void)
169{
170 return xt_register_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg));
171}
172
173static void __exit ecn_mt_exit(void)
174{
175 xt_unregister_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg));
176}
177
178module_init(ecn_mt_init);
179module_exit(ecn_mt_exit);
180
