1 /* Kernel module to match connection tracking information.
2 * Superset of Rusty's minimalistic state match.
3 *
4 * (C) 2001 Marc Boucher (marc@mbsi.ca).
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11 #include <linux/module.h>
12 #include <linux/skbuff.h>
13 #include <linux/netfilter_ipv4/ip_conntrack.h>
14 #include <linux/netfilter_ipv4/ip_tables.h>
15 #include <linux/netfilter_ipv4/ipt_conntrack.h>
16
17 MODULE_LICENSE("GPL");
18 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
19 MODULE_DESCRIPTION("iptables connection tracking match module");
20
21 static int
22 match(const struct sk_buff *skb,
23 const struct net_device *in,
24 const struct net_device *out,
25 const void *matchinfo,
26 int offset,
27 int *hotdrop)
28 {
29 const struct ipt_conntrack_info *sinfo = matchinfo;
30 struct ip_conntrack *ct;
31 enum ip_conntrack_info ctinfo;
32 unsigned int statebit;
33
34 ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
35
36 #define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
37
38 if (ct == &ip_conntrack_untracked)
39 statebit = IPT_CONNTRACK_STATE_UNTRACKED;
40 else if (ct)
41 statebit = IPT_CONNTRACK_STATE_BIT(ctinfo);
42 else
43 statebit = IPT_CONNTRACK_STATE_INVALID;
44
45 if(sinfo->flags & IPT_CONNTRACK_STATE) {
46 if (ct) {
47 if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip !=
48 ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip)
49 statebit |= IPT_CONNTRACK_STATE_SNAT;
50
51 if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip !=
52 ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip)
53 statebit |= IPT_CONNTRACK_STATE_DNAT;
54 }
55
56 if (FWINV((statebit & sinfo->statemask) == 0, IPT_CONNTRACK_STATE))
57 return 0;
58 }
59
60 if(sinfo->flags & IPT_CONNTRACK_PROTO) {
61 if (!ct || FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum, IPT_CONNTRACK_PROTO))
62 return 0;
63 }
64
65 if(sinfo->flags & IPT_CONNTRACK_ORIGSRC) {
66 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip&sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) != sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip, IPT_CONNTRACK_ORIGSRC))
67 return 0;
68 }
69
70 if(sinfo->flags & IPT_CONNTRACK_ORIGDST) {
71 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip&sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip, IPT_CONNTRACK_ORIGDST))
72 return 0;
73 }
74
75 if(sinfo->flags & IPT_CONNTRACK_REPLSRC) {
76 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip&sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) != sinfo->tuple[IP_CT_DIR_REPLY].src.ip, IPT_CONNTRACK_REPLSRC))
77 return 0;
78 }
79
80 if(sinfo->flags & IPT_CONNTRACK_REPLDST) {
81 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip&sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) != sinfo->tuple[IP_CT_DIR_REPLY].dst.ip, IPT_CONNTRACK_REPLDST))
82 return 0;
83 }
84
85 if(sinfo->flags & IPT_CONNTRACK_STATUS) {
86 if (!ct || FWINV((ct->status & sinfo->statusmask) == 0, IPT_CONNTRACK_STATUS))
87 return 0;
88 }
89
90 if(sinfo->flags & IPT_CONNTRACK_EXPIRES) {
91 unsigned long expires;
92
93 if(!ct)
94 return 0;
95
96 expires = timer_pending(&ct->timeout) ? (ct->timeout.expires - jiffies)/HZ : 0;
97
98 if (FWINV(!(expires >= sinfo->expires_min && expires <= sinfo->expires_max), IPT_CONNTRACK_EXPIRES))
99 return 0;
100 }
101
102 return 1;
103 }
104
105 static int check(const char *tablename,
106 const struct ipt_ip *ip,
107 void *matchinfo,
108 unsigned int matchsize,
109 unsigned int hook_mask)
110 {
111 if (matchsize != IPT_ALIGN(sizeof(struct ipt_conntrack_info)))
112 return 0;
113
114 return 1;
115 }
116
117 static struct ipt_match conntrack_match = {
118 .name = "conntrack",
119 .match = &match,
120 .checkentry = &check,
121 .me = THIS_MODULE,
122 };
123
124 static int __init init(void)
125 {
126 need_ip_conntrack();
127 return ipt_register_match(&conntrack_match);
128 }
129
130 static void __exit fini(void)
131 {
132 ipt_unregister_match(&conntrack_match);
133 }
134
135 module_init(init);
136 module_exit(fini);
137
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