1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Xtables module for matching the value of the IPv4/IPv6 and TCP ECN bits |
4 | * |
5 | * (C) 2002 by Harald Welte <laforge@gnumonks.org> |
6 | * (C) 2011 Patrick McHardy <kaber@trash.net> |
7 | */ |
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
9 | #include <linux/in.h> |
10 | #include <linux/ip.h> |
11 | #include <net/ip.h> |
12 | #include <linux/module.h> |
13 | #include <linux/skbuff.h> |
14 | #include <linux/tcp.h> |
15 | |
16 | #include <linux/netfilter/x_tables.h> |
17 | #include <linux/netfilter/xt_ecn.h> |
18 | #include <linux/netfilter_ipv4/ip_tables.h> |
19 | #include <linux/netfilter_ipv6/ip6_tables.h> |
20 | |
21 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>" ); |
22 | MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match" ); |
23 | MODULE_LICENSE("GPL" ); |
24 | MODULE_ALIAS("ipt_ecn" ); |
25 | MODULE_ALIAS("ip6t_ecn" ); |
26 | |
27 | static bool match_tcp(const struct sk_buff *skb, struct xt_action_param *par) |
28 | { |
29 | const struct xt_ecn_info *einfo = par->matchinfo; |
30 | struct tcphdr _tcph; |
31 | const struct tcphdr *th; |
32 | |
33 | /* In practice, TCP match does this, so can't fail. But let's |
34 | * be good citizens. |
35 | */ |
36 | th = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_tcph), buffer: &_tcph); |
37 | if (th == NULL) |
38 | return false; |
39 | |
40 | if (einfo->operation & XT_ECN_OP_MATCH_ECE) { |
41 | if (einfo->invert & XT_ECN_OP_MATCH_ECE) { |
42 | if (th->ece == 1) |
43 | return false; |
44 | } else { |
45 | if (th->ece == 0) |
46 | return false; |
47 | } |
48 | } |
49 | |
50 | if (einfo->operation & XT_ECN_OP_MATCH_CWR) { |
51 | if (einfo->invert & XT_ECN_OP_MATCH_CWR) { |
52 | if (th->cwr == 1) |
53 | return false; |
54 | } else { |
55 | if (th->cwr == 0) |
56 | return false; |
57 | } |
58 | } |
59 | |
60 | return true; |
61 | } |
62 | |
63 | static inline bool match_ip(const struct sk_buff *skb, |
64 | const struct xt_ecn_info *einfo) |
65 | { |
66 | return ((ip_hdr(skb)->tos & XT_ECN_IP_MASK) == einfo->ip_ect) ^ |
67 | !!(einfo->invert & XT_ECN_OP_MATCH_IP); |
68 | } |
69 | |
70 | static bool ecn_mt4(const struct sk_buff *skb, struct xt_action_param *par) |
71 | { |
72 | const struct xt_ecn_info *info = par->matchinfo; |
73 | |
74 | if (info->operation & XT_ECN_OP_MATCH_IP && !match_ip(skb, einfo: info)) |
75 | return false; |
76 | |
77 | if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && |
78 | !match_tcp(skb, par)) |
79 | return false; |
80 | |
81 | return true; |
82 | } |
83 | |
84 | static int ecn_mt_check4(const struct xt_mtchk_param *par) |
85 | { |
86 | const struct xt_ecn_info *info = par->matchinfo; |
87 | const struct ipt_ip *ip = par->entryinfo; |
88 | |
89 | if (info->operation & XT_ECN_OP_MATCH_MASK) |
90 | return -EINVAL; |
91 | |
92 | if (info->invert & XT_ECN_OP_MATCH_MASK) |
93 | return -EINVAL; |
94 | |
95 | if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && |
96 | (ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) { |
97 | pr_info_ratelimited("cannot match TCP bits for non-tcp packets\n" ); |
98 | return -EINVAL; |
99 | } |
100 | |
101 | return 0; |
102 | } |
103 | |
104 | static inline bool match_ipv6(const struct sk_buff *skb, |
105 | const struct xt_ecn_info *einfo) |
106 | { |
107 | return (((ipv6_hdr(skb)->flow_lbl[0] >> 4) & XT_ECN_IP_MASK) == |
108 | einfo->ip_ect) ^ |
109 | !!(einfo->invert & XT_ECN_OP_MATCH_IP); |
110 | } |
111 | |
112 | static bool ecn_mt6(const struct sk_buff *skb, struct xt_action_param *par) |
113 | { |
114 | const struct xt_ecn_info *info = par->matchinfo; |
115 | |
116 | if (info->operation & XT_ECN_OP_MATCH_IP && !match_ipv6(skb, einfo: info)) |
117 | return false; |
118 | |
119 | if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && |
120 | !match_tcp(skb, par)) |
121 | return false; |
122 | |
123 | return true; |
124 | } |
125 | |
126 | static int ecn_mt_check6(const struct xt_mtchk_param *par) |
127 | { |
128 | const struct xt_ecn_info *info = par->matchinfo; |
129 | const struct ip6t_ip6 *ip = par->entryinfo; |
130 | |
131 | if (info->operation & XT_ECN_OP_MATCH_MASK) |
132 | return -EINVAL; |
133 | |
134 | if (info->invert & XT_ECN_OP_MATCH_MASK) |
135 | return -EINVAL; |
136 | |
137 | if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) && |
138 | (ip->proto != IPPROTO_TCP || ip->invflags & IP6T_INV_PROTO)) { |
139 | pr_info_ratelimited("cannot match TCP bits for non-tcp packets\n" ); |
140 | return -EINVAL; |
141 | } |
142 | |
143 | return 0; |
144 | } |
145 | |
146 | static struct xt_match ecn_mt_reg[] __read_mostly = { |
147 | { |
148 | .name = "ecn" , |
149 | .family = NFPROTO_IPV4, |
150 | .match = ecn_mt4, |
151 | .matchsize = sizeof(struct xt_ecn_info), |
152 | .checkentry = ecn_mt_check4, |
153 | .me = THIS_MODULE, |
154 | }, |
155 | { |
156 | .name = "ecn" , |
157 | .family = NFPROTO_IPV6, |
158 | .match = ecn_mt6, |
159 | .matchsize = sizeof(struct xt_ecn_info), |
160 | .checkentry = ecn_mt_check6, |
161 | .me = THIS_MODULE, |
162 | }, |
163 | }; |
164 | |
165 | static int __init ecn_mt_init(void) |
166 | { |
167 | return xt_register_matches(match: ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg)); |
168 | } |
169 | |
170 | static void __exit ecn_mt_exit(void) |
171 | { |
172 | xt_unregister_matches(match: ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg)); |
173 | } |
174 | |
175 | module_init(ecn_mt_init); |
176 | module_exit(ecn_mt_exit); |
177 | |