1/* Kernel module to match connection tracking information.
2 * Superset of Rusty's minimalistic state match.
3 * GPL (C) 2001  Marc Boucher (marc@mbsi.ca).
4 */
5#include <linux/module.h>
6#include <linux/skbuff.h>
7#include <linux/netfilter_ipv4/ip_conntrack.h>
8#include <linux/netfilter_ipv4/ip_tables.h>
9#include <linux/netfilter_ipv4/ipt_conntrack.h>
10
11static int
12match(const struct sk_buff *skb,
13      const struct net_device *in,
14      const struct net_device *out,
15      const void *matchinfo,
16      int offset,
17      const void *hdr,
18      u_int16_t datalen,
19      int *hotdrop)
20{
21	const struct ipt_conntrack_info *sinfo = matchinfo;
22	struct ip_conntrack *ct;
23	enum ip_conntrack_info ctinfo;
24	unsigned int statebit;
25
26	ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
27
28#define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
29
30	statebit = ct ? IPT_CONNTRACK_STATE_INVALID : IPT_CONNTRACK_STATE_BIT(ctinfo);
31	if(sinfo->flags & IPT_CONNTRACK_STATE) {
32		if (ct) {
33			if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip !=
34			    ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip)
35				statebit |= IPT_CONNTRACK_STATE_SNAT;
36
37			if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip !=
38			    ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip)
39				statebit |= IPT_CONNTRACK_STATE_DNAT;
40		}
41
42		if (FWINV((statebit & sinfo->statemask) == 0, IPT_CONNTRACK_STATE))
43			return 0;
44	}
45
46	if(sinfo->flags & IPT_CONNTRACK_PROTO) {
47		if (!ct || FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum, IPT_CONNTRACK_PROTO))
48                	return 0;
49	}
50
51	if(sinfo->flags & IPT_CONNTRACK_ORIGSRC) {
52		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))
53			return 0;
54	}
55
56	if(sinfo->flags & IPT_CONNTRACK_ORIGDST) {
57		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))
58			return 0;
59	}
60
61	if(sinfo->flags & IPT_CONNTRACK_REPLSRC) {
62		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))
63			return 0;
64	}
65
66	if(sinfo->flags & IPT_CONNTRACK_REPLDST) {
67		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))
68			return 0;
69	}
70
71	if(sinfo->flags & IPT_CONNTRACK_STATUS) {
72		if (!ct || FWINV((ct->status & sinfo->statusmask) == 0, IPT_CONNTRACK_STATUS))
73			return 0;
74	}
75
76	if(sinfo->flags & IPT_CONNTRACK_EXPIRES) {
77		unsigned long expires;
78
79		if(!ct)
80			return 0;
81
82		expires = timer_pending(&ct->timeout) ? (ct->timeout.expires - jiffies)/HZ : 0;
83
84		if (FWINV(!(expires >= sinfo->expires_min && expires <= sinfo->expires_max), IPT_CONNTRACK_EXPIRES))
85			return 0;
86	}
87
88	return 1;
89}
90
91static int check(const char *tablename,
92		 const struct ipt_ip *ip,
93		 void *matchinfo,
94		 unsigned int matchsize,
95		 unsigned int hook_mask)
96{
97	if (matchsize != IPT_ALIGN(sizeof(struct ipt_conntrack_info)))
98		return 0;
99
100	return 1;
101}
102
103static struct ipt_match conntrack_match
104= { { NULL, NULL }, "conntrack", &match, &check, NULL, THIS_MODULE };
105
106static int __init init(void)
107{
108	/* NULL if ip_conntrack not a module */
109	if (ip_conntrack_module)
110		__MOD_INC_USE_COUNT(ip_conntrack_module);
111	return ipt_register_match(&conntrack_match);
112}
113
114static void __exit fini(void)
115{
116	ipt_unregister_match(&conntrack_match);
117	if (ip_conntrack_module)
118		__MOD_DEC_USE_COUNT(ip_conntrack_module);
119}
120
121module_init(init);
122module_exit(fini);
123MODULE_LICENSE("GPL");
124