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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/x_tables.h> | |
14 | #include <linux/netfilter/xt_conntrack.h> | |
15 | #include <net/netfilter/nf_conntrack.h> | |
16 | ||
17 | MODULE_LICENSE("GPL"); | |
18 | MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>"); | |
19 | MODULE_DESCRIPTION("iptables connection tracking match module"); | |
20 | MODULE_ALIAS("ipt_conntrack"); | |
21 | ||
22 | static bool | |
23 | match(const struct sk_buff *skb, | |
24 | const struct net_device *in, | |
25 | const struct net_device *out, | |
26 | const struct xt_match *match, | |
27 | const void *matchinfo, | |
28 | int offset, | |
29 | unsigned int protoff, | |
30 | bool *hotdrop) | |
31 | { | |
32 | const struct xt_conntrack_info *sinfo = matchinfo; | |
33 | const struct nf_conn *ct; | |
34 | enum ip_conntrack_info ctinfo; | |
35 | unsigned int statebit; | |
36 | ||
37 | ct = nf_ct_get(skb, &ctinfo); | |
38 | ||
39 | #define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg)) | |
40 | ||
41 | if (ct == &nf_conntrack_untracked) | |
42 | statebit = XT_CONNTRACK_STATE_UNTRACKED; | |
43 | else if (ct) | |
44 | statebit = XT_CONNTRACK_STATE_BIT(ctinfo); | |
45 | else | |
46 | statebit = XT_CONNTRACK_STATE_INVALID; | |
47 | ||
48 | if (sinfo->flags & XT_CONNTRACK_STATE) { | |
49 | if (ct) { | |
50 | if (test_bit(IPS_SRC_NAT_BIT, &ct->status)) | |
51 | statebit |= XT_CONNTRACK_STATE_SNAT; | |
52 | if (test_bit(IPS_DST_NAT_BIT, &ct->status)) | |
53 | statebit |= XT_CONNTRACK_STATE_DNAT; | |
54 | } | |
55 | if (FWINV((statebit & sinfo->statemask) == 0, | |
56 | XT_CONNTRACK_STATE)) | |
57 | return false; | |
58 | } | |
59 | ||
60 | if (ct == NULL) { | |
61 | if (sinfo->flags & ~XT_CONNTRACK_STATE) | |
62 | return false; | |
63 | return true; | |
64 | } | |
65 | ||
66 | if (sinfo->flags & XT_CONNTRACK_PROTO && | |
67 | FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum != | |
68 | sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum, | |
69 | XT_CONNTRACK_PROTO)) | |
70 | return false; | |
71 | ||
72 | if (sinfo->flags & XT_CONNTRACK_ORIGSRC && | |
73 | FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip & | |
74 | sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) != | |
75 | sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip, | |
76 | XT_CONNTRACK_ORIGSRC)) | |
77 | return false; | |
78 | ||
79 | if (sinfo->flags & XT_CONNTRACK_ORIGDST && | |
80 | FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip & | |
81 | sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) != | |
82 | sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip, | |
83 | XT_CONNTRACK_ORIGDST)) | |
84 | return false; | |
85 | ||
86 | if (sinfo->flags & XT_CONNTRACK_REPLSRC && | |
87 | FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip & | |
88 | sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) != | |
89 | sinfo->tuple[IP_CT_DIR_REPLY].src.ip, | |
90 | XT_CONNTRACK_REPLSRC)) | |
91 | return false; | |
92 | ||
93 | if (sinfo->flags & XT_CONNTRACK_REPLDST && | |
94 | FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip & | |
95 | sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) != | |
96 | sinfo->tuple[IP_CT_DIR_REPLY].dst.ip, | |
97 | XT_CONNTRACK_REPLDST)) | |
98 | return false; | |
99 | ||
100 | if (sinfo->flags & XT_CONNTRACK_STATUS && | |
101 | FWINV((ct->status & sinfo->statusmask) == 0, | |
102 | XT_CONNTRACK_STATUS)) | |
103 | return false; | |
104 | ||
105 | if(sinfo->flags & XT_CONNTRACK_EXPIRES) { | |
106 | unsigned long expires = timer_pending(&ct->timeout) ? | |
107 | (ct->timeout.expires - jiffies)/HZ : 0; | |
108 | ||
109 | if (FWINV(!(expires >= sinfo->expires_min && | |
110 | expires <= sinfo->expires_max), | |
111 | XT_CONNTRACK_EXPIRES)) | |
112 | return false; | |
113 | } | |
114 | return true; | |
115 | } | |
116 | ||
117 | static bool | |
118 | checkentry(const char *tablename, | |
119 | const void *ip, | |
120 | const struct xt_match *match, | |
121 | void *matchinfo, | |
122 | unsigned int hook_mask) | |
123 | { | |
124 | if (nf_ct_l3proto_try_module_get(match->family) < 0) { | |
125 | printk(KERN_WARNING "can't load conntrack support for " | |
126 | "proto=%d\n", match->family); | |
127 | return false; | |
128 | } | |
129 | return true; | |
130 | } | |
131 | ||
132 | static void destroy(const struct xt_match *match, void *matchinfo) | |
133 | { | |
134 | nf_ct_l3proto_module_put(match->family); | |
135 | } | |
136 | ||
137 | #ifdef CONFIG_COMPAT | |
138 | struct compat_xt_conntrack_info | |
139 | { | |
140 | compat_uint_t statemask; | |
141 | compat_uint_t statusmask; | |
142 | struct ip_conntrack_old_tuple tuple[IP_CT_DIR_MAX]; | |
143 | struct in_addr sipmsk[IP_CT_DIR_MAX]; | |
144 | struct in_addr dipmsk[IP_CT_DIR_MAX]; | |
145 | compat_ulong_t expires_min; | |
146 | compat_ulong_t expires_max; | |
147 | u_int8_t flags; | |
148 | u_int8_t invflags; | |
149 | }; | |
150 | ||
151 | static void compat_from_user(void *dst, void *src) | |
152 | { | |
153 | const struct compat_xt_conntrack_info *cm = src; | |
154 | struct xt_conntrack_info m = { | |
155 | .statemask = cm->statemask, | |
156 | .statusmask = cm->statusmask, | |
157 | .expires_min = cm->expires_min, | |
158 | .expires_max = cm->expires_max, | |
159 | .flags = cm->flags, | |
160 | .invflags = cm->invflags, | |
161 | }; | |
162 | memcpy(m.tuple, cm->tuple, sizeof(m.tuple)); | |
163 | memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk)); | |
164 | memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk)); | |
165 | memcpy(dst, &m, sizeof(m)); | |
166 | } | |
167 | ||
168 | static int compat_to_user(void __user *dst, void *src) | |
169 | { | |
170 | const struct xt_conntrack_info *m = src; | |
171 | struct compat_xt_conntrack_info cm = { | |
172 | .statemask = m->statemask, | |
173 | .statusmask = m->statusmask, | |
174 | .expires_min = m->expires_min, | |
175 | .expires_max = m->expires_max, | |
176 | .flags = m->flags, | |
177 | .invflags = m->invflags, | |
178 | }; | |
179 | memcpy(cm.tuple, m->tuple, sizeof(cm.tuple)); | |
180 | memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk)); | |
181 | memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk)); | |
182 | return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0; | |
183 | } | |
184 | #endif | |
185 | ||
186 | static struct xt_match conntrack_match __read_mostly = { | |
187 | .name = "conntrack", | |
188 | .match = match, | |
189 | .checkentry = checkentry, | |
190 | .destroy = destroy, | |
191 | .matchsize = sizeof(struct xt_conntrack_info), | |
192 | #ifdef CONFIG_COMPAT | |
193 | .compatsize = sizeof(struct compat_xt_conntrack_info), | |
194 | .compat_from_user = compat_from_user, | |
195 | .compat_to_user = compat_to_user, | |
196 | #endif | |
197 | .family = AF_INET, | |
198 | .me = THIS_MODULE, | |
199 | }; | |
200 | ||
201 | static int __init xt_conntrack_init(void) | |
202 | { | |
203 | return xt_register_match(&conntrack_match); | |
204 | } | |
205 | ||
206 | static void __exit xt_conntrack_fini(void) | |
207 | { | |
208 | xt_unregister_match(&conntrack_match); | |
209 | } | |
210 | ||
211 | module_init(xt_conntrack_init); | |
212 | module_exit(xt_conntrack_fini); |