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1da177e4 LT |
1 | /* IP tables module for matching the value of the IPv4 and TCP ECN bits |
2 | * | |
1da177e4 LT |
3 | * (C) 2002 by Harald Welte <laforge@gnumonks.org> |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License version 2 as | |
7 | * published by the Free Software Foundation. | |
8 | */ | |
9 | ||
6709dbbb JE |
10 | #include <linux/in.h> |
11 | #include <linux/ip.h> | |
c9bdd4b5 | 12 | #include <net/ip.h> |
1da177e4 LT |
13 | #include <linux/module.h> |
14 | #include <linux/skbuff.h> | |
15 | #include <linux/tcp.h> | |
16 | ||
6709dbbb | 17 | #include <linux/netfilter/x_tables.h> |
1da177e4 LT |
18 | #include <linux/netfilter_ipv4/ip_tables.h> |
19 | #include <linux/netfilter_ipv4/ipt_ecn.h> | |
20 | ||
21 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); | |
22 | MODULE_DESCRIPTION("iptables ECN matching module"); | |
23 | MODULE_LICENSE("GPL"); | |
24 | ||
1d93a9cb JE |
25 | static inline bool match_ip(const struct sk_buff *skb, |
26 | const struct ipt_ecn_info *einfo) | |
1da177e4 | 27 | { |
eddc9ec5 | 28 | return (ip_hdr(skb)->tos & IPT_ECN_IP_MASK) == einfo->ip_ect; |
1da177e4 LT |
29 | } |
30 | ||
1d93a9cb JE |
31 | static inline bool match_tcp(const struct sk_buff *skb, |
32 | const struct ipt_ecn_info *einfo, | |
33 | bool *hotdrop) | |
1da177e4 LT |
34 | { |
35 | struct tcphdr _tcph, *th; | |
36 | ||
37 | /* In practice, TCP match does this, so can't fail. But let's | |
38 | * be good citizens. | |
39 | */ | |
c9bdd4b5 | 40 | th = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_tcph), &_tcph); |
1da177e4 | 41 | if (th == NULL) { |
cff533ac | 42 | *hotdrop = false; |
1d93a9cb | 43 | return false; |
1da177e4 LT |
44 | } |
45 | ||
46 | if (einfo->operation & IPT_ECN_OP_MATCH_ECE) { | |
47 | if (einfo->invert & IPT_ECN_OP_MATCH_ECE) { | |
48 | if (th->ece == 1) | |
1d93a9cb | 49 | return false; |
1da177e4 LT |
50 | } else { |
51 | if (th->ece == 0) | |
1d93a9cb | 52 | return false; |
1da177e4 LT |
53 | } |
54 | } | |
55 | ||
56 | if (einfo->operation & IPT_ECN_OP_MATCH_CWR) { | |
57 | if (einfo->invert & IPT_ECN_OP_MATCH_CWR) { | |
58 | if (th->cwr == 1) | |
1d93a9cb | 59 | return false; |
1da177e4 LT |
60 | } else { |
61 | if (th->cwr == 0) | |
1d93a9cb | 62 | return false; |
1da177e4 LT |
63 | } |
64 | } | |
65 | ||
1d93a9cb | 66 | return true; |
1da177e4 LT |
67 | } |
68 | ||
1d93a9cb JE |
69 | static bool match(const struct sk_buff *skb, |
70 | const struct net_device *in, const struct net_device *out, | |
71 | const struct xt_match *match, const void *matchinfo, | |
72 | int offset, unsigned int protoff, bool *hotdrop) | |
1da177e4 LT |
73 | { |
74 | const struct ipt_ecn_info *info = matchinfo; | |
75 | ||
76 | if (info->operation & IPT_ECN_OP_MATCH_IP) | |
77 | if (!match_ip(skb, info)) | |
1d93a9cb | 78 | return false; |
1da177e4 LT |
79 | |
80 | if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) { | |
eddc9ec5 | 81 | if (ip_hdr(skb)->protocol != IPPROTO_TCP) |
1d93a9cb | 82 | return false; |
1da177e4 | 83 | if (!match_tcp(skb, info, hotdrop)) |
1d93a9cb | 84 | return false; |
1da177e4 LT |
85 | } |
86 | ||
1d93a9cb | 87 | return true; |
1da177e4 LT |
88 | } |
89 | ||
ccb79bdc JE |
90 | static bool checkentry(const char *tablename, const void *ip_void, |
91 | const struct xt_match *match, | |
92 | void *matchinfo, unsigned int hook_mask) | |
1da177e4 LT |
93 | { |
94 | const struct ipt_ecn_info *info = matchinfo; | |
2e4e6a17 | 95 | const struct ipt_ip *ip = ip_void; |
1da177e4 | 96 | |
1da177e4 | 97 | if (info->operation & IPT_ECN_OP_MATCH_MASK) |
ccb79bdc | 98 | return false; |
1da177e4 LT |
99 | |
100 | if (info->invert & IPT_ECN_OP_MATCH_MASK) | |
ccb79bdc | 101 | return false; |
1da177e4 LT |
102 | |
103 | if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR) | |
104 | && ip->proto != IPPROTO_TCP) { | |
105 | printk(KERN_WARNING "ipt_ecn: can't match TCP bits in rule for" | |
106 | " non-tcp packets\n"); | |
ccb79bdc | 107 | return false; |
1da177e4 LT |
108 | } |
109 | ||
ccb79bdc | 110 | return true; |
1da177e4 LT |
111 | } |
112 | ||
6709dbbb | 113 | static struct xt_match ecn_match = { |
1da177e4 | 114 | .name = "ecn", |
6709dbbb | 115 | .family = AF_INET, |
1d5cd909 PM |
116 | .match = match, |
117 | .matchsize = sizeof(struct ipt_ecn_info), | |
118 | .checkentry = checkentry, | |
1da177e4 LT |
119 | .me = THIS_MODULE, |
120 | }; | |
121 | ||
65b4b4e8 | 122 | static int __init ipt_ecn_init(void) |
1da177e4 | 123 | { |
6709dbbb | 124 | return xt_register_match(&ecn_match); |
1da177e4 LT |
125 | } |
126 | ||
65b4b4e8 | 127 | static void __exit ipt_ecn_fini(void) |
1da177e4 | 128 | { |
6709dbbb | 129 | xt_unregister_match(&ecn_match); |
1da177e4 LT |
130 | } |
131 | ||
65b4b4e8 AM |
132 | module_init(ipt_ecn_init); |
133 | module_exit(ipt_ecn_fini); |