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e281b198 JE |
1 | /* |
2 | * "TEE" target extension for Xtables | |
3 | * Copyright © Sebastian Claßen, 2007 | |
4 | * Jan Engelhardt, 2007-2010 | |
5 | * | |
6 | * based on ipt_ROUTE.c from Cédric de Launois | |
7 | * <delaunois@info.ucl.be> | |
8 | * | |
9 | * This program is free software; you can redistribute it and/or | |
10 | * modify it under the terms of the GNU General Public License | |
11 | * version 2 or later, as published by the Free Software Foundation. | |
12 | */ | |
13 | #include <linux/ip.h> | |
14 | #include <linux/module.h> | |
cd58bcd9 | 15 | #include <linux/percpu.h> |
e281b198 JE |
16 | #include <linux/route.h> |
17 | #include <linux/skbuff.h> | |
22265a5c | 18 | #include <linux/notifier.h> |
e281b198 JE |
19 | #include <net/checksum.h> |
20 | #include <net/icmp.h> | |
21 | #include <net/ip.h> | |
22 | #include <net/ipv6.h> | |
23 | #include <net/ip6_route.h> | |
24 | #include <net/route.h> | |
25 | #include <linux/netfilter/x_tables.h> | |
26 | #include <linux/netfilter/xt_TEE.h> | |
27 | ||
28 | #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) | |
29 | # define WITH_CONNTRACK 1 | |
30 | # include <net/netfilter/nf_conntrack.h> | |
31 | #endif | |
32 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
33 | # define WITH_IPV6 1 | |
34 | #endif | |
35 | ||
22265a5c PM |
36 | struct xt_tee_priv { |
37 | struct notifier_block notifier; | |
38 | struct xt_tee_tginfo *tginfo; | |
39 | int oif; | |
40 | }; | |
41 | ||
e281b198 | 42 | static const union nf_inet_addr tee_zero_address; |
cd58bcd9 | 43 | static DEFINE_PER_CPU(bool, tee_active); |
e281b198 JE |
44 | |
45 | static struct net *pick_net(struct sk_buff *skb) | |
46 | { | |
47 | #ifdef CONFIG_NET_NS | |
48 | const struct dst_entry *dst; | |
49 | ||
50 | if (skb->dev != NULL) | |
51 | return dev_net(skb->dev); | |
52 | dst = skb_dst(skb); | |
53 | if (dst != NULL && dst->dev != NULL) | |
54 | return dev_net(dst->dev); | |
55 | #endif | |
56 | return &init_net; | |
57 | } | |
58 | ||
e281b198 JE |
59 | static bool |
60 | tee_tg_route4(struct sk_buff *skb, const struct xt_tee_tginfo *info) | |
61 | { | |
62 | const struct iphdr *iph = ip_hdr(skb); | |
63 | struct net *net = pick_net(skb); | |
64 | struct rtable *rt; | |
65 | struct flowi fl; | |
66 | ||
67 | memset(&fl, 0, sizeof(fl)); | |
22265a5c PM |
68 | if (info->priv) { |
69 | if (info->priv->oif == -1) | |
70 | return false; | |
1d28f42c | 71 | fl.flowi_oif = info->priv->oif; |
22265a5c | 72 | } |
5811662b CG |
73 | fl.fl4_dst = info->gw.ip; |
74 | fl.fl4_tos = RT_TOS(iph->tos); | |
75 | fl.fl4_scope = RT_SCOPE_UNIVERSE; | |
b23dd4fe DM |
76 | rt = ip_route_output_key(net, &fl); |
77 | if (IS_ERR(rt)) | |
e281b198 JE |
78 | return false; |
79 | ||
50636af7 | 80 | skb_dst_drop(skb); |
d8d1f30b CG |
81 | skb_dst_set(skb, &rt->dst); |
82 | skb->dev = rt->dst.dev; | |
e281b198 JE |
83 | skb->protocol = htons(ETH_P_IP); |
84 | return true; | |
85 | } | |
86 | ||
87 | static unsigned int | |
4b560b44 | 88 | tee_tg4(struct sk_buff *skb, const struct xt_action_param *par) |
e281b198 JE |
89 | { |
90 | const struct xt_tee_tginfo *info = par->targinfo; | |
91 | struct iphdr *iph; | |
92 | ||
cd58bcd9 JE |
93 | if (percpu_read(tee_active)) |
94 | return XT_CONTINUE; | |
e281b198 JE |
95 | /* |
96 | * Copy the skb, and route the copy. Will later return %XT_CONTINUE for | |
97 | * the original skb, which should continue on its way as if nothing has | |
98 | * happened. The copy should be independently delivered to the TEE | |
99 | * --gateway. | |
100 | */ | |
101 | skb = pskb_copy(skb, GFP_ATOMIC); | |
102 | if (skb == NULL) | |
103 | return XT_CONTINUE; | |
104 | ||
105 | #ifdef WITH_CONNTRACK | |
106 | /* Avoid counting cloned packets towards the original connection. */ | |
107 | nf_conntrack_put(skb->nfct); | |
5bfddbd4 | 108 | skb->nfct = &nf_ct_untracked_get()->ct_general; |
e281b198 JE |
109 | skb->nfctinfo = IP_CT_NEW; |
110 | nf_conntrack_get(skb->nfct); | |
111 | #endif | |
112 | /* | |
113 | * If we are in PREROUTING/INPUT, the checksum must be recalculated | |
114 | * since the length could have changed as a result of defragmentation. | |
115 | * | |
116 | * We also decrease the TTL to mitigate potential TEE loops | |
117 | * between two hosts. | |
118 | * | |
119 | * Set %IP_DF so that the original source is notified of a potentially | |
120 | * decreased MTU on the clone route. IPv6 does this too. | |
121 | */ | |
122 | iph = ip_hdr(skb); | |
123 | iph->frag_off |= htons(IP_DF); | |
124 | if (par->hooknum == NF_INET_PRE_ROUTING || | |
125 | par->hooknum == NF_INET_LOCAL_IN) | |
126 | --iph->ttl; | |
127 | ip_send_check(iph); | |
128 | ||
cd58bcd9 JE |
129 | if (tee_tg_route4(skb, info)) { |
130 | percpu_write(tee_active, true); | |
131 | ip_local_out(skb); | |
132 | percpu_write(tee_active, false); | |
133 | } else { | |
e281b198 | 134 | kfree_skb(skb); |
cd58bcd9 | 135 | } |
e281b198 JE |
136 | return XT_CONTINUE; |
137 | } | |
138 | ||
139 | #ifdef WITH_IPV6 | |
140 | static bool | |
141 | tee_tg_route6(struct sk_buff *skb, const struct xt_tee_tginfo *info) | |
142 | { | |
143 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
144 | struct net *net = pick_net(skb); | |
145 | struct dst_entry *dst; | |
146 | struct flowi fl; | |
147 | ||
148 | memset(&fl, 0, sizeof(fl)); | |
22265a5c PM |
149 | if (info->priv) { |
150 | if (info->priv->oif == -1) | |
151 | return false; | |
1d28f42c | 152 | fl.flowi_oif = info->priv->oif; |
22265a5c | 153 | } |
5811662b CG |
154 | fl.fl6_dst = info->gw.in6; |
155 | fl.fl6_flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) | | |
156 | (iph->flow_lbl[1] << 8) | iph->flow_lbl[2]; | |
e281b198 JE |
157 | dst = ip6_route_output(net, NULL, &fl); |
158 | if (dst == NULL) | |
159 | return false; | |
160 | ||
50636af7 | 161 | skb_dst_drop(skb); |
e281b198 JE |
162 | skb_dst_set(skb, dst); |
163 | skb->dev = dst->dev; | |
164 | skb->protocol = htons(ETH_P_IPV6); | |
165 | return true; | |
166 | } | |
167 | ||
168 | static unsigned int | |
4b560b44 | 169 | tee_tg6(struct sk_buff *skb, const struct xt_action_param *par) |
e281b198 JE |
170 | { |
171 | const struct xt_tee_tginfo *info = par->targinfo; | |
172 | ||
cd58bcd9 JE |
173 | if (percpu_read(tee_active)) |
174 | return XT_CONTINUE; | |
e281b198 JE |
175 | skb = pskb_copy(skb, GFP_ATOMIC); |
176 | if (skb == NULL) | |
177 | return XT_CONTINUE; | |
178 | ||
179 | #ifdef WITH_CONNTRACK | |
180 | nf_conntrack_put(skb->nfct); | |
5bfddbd4 | 181 | skb->nfct = &nf_ct_untracked_get()->ct_general; |
e281b198 JE |
182 | skb->nfctinfo = IP_CT_NEW; |
183 | nf_conntrack_get(skb->nfct); | |
184 | #endif | |
185 | if (par->hooknum == NF_INET_PRE_ROUTING || | |
186 | par->hooknum == NF_INET_LOCAL_IN) { | |
187 | struct ipv6hdr *iph = ipv6_hdr(skb); | |
188 | --iph->hop_limit; | |
189 | } | |
cd58bcd9 JE |
190 | if (tee_tg_route6(skb, info)) { |
191 | percpu_write(tee_active, true); | |
192 | ip6_local_out(skb); | |
193 | percpu_write(tee_active, false); | |
194 | } else { | |
e281b198 | 195 | kfree_skb(skb); |
cd58bcd9 | 196 | } |
e281b198 JE |
197 | return XT_CONTINUE; |
198 | } | |
199 | #endif /* WITH_IPV6 */ | |
200 | ||
22265a5c PM |
201 | static int tee_netdev_event(struct notifier_block *this, unsigned long event, |
202 | void *ptr) | |
203 | { | |
204 | struct net_device *dev = ptr; | |
205 | struct xt_tee_priv *priv; | |
206 | ||
207 | priv = container_of(this, struct xt_tee_priv, notifier); | |
208 | switch (event) { | |
209 | case NETDEV_REGISTER: | |
210 | if (!strcmp(dev->name, priv->tginfo->oif)) | |
211 | priv->oif = dev->ifindex; | |
212 | break; | |
213 | case NETDEV_UNREGISTER: | |
214 | if (dev->ifindex == priv->oif) | |
215 | priv->oif = -1; | |
216 | break; | |
217 | case NETDEV_CHANGENAME: | |
218 | if (!strcmp(dev->name, priv->tginfo->oif)) | |
219 | priv->oif = dev->ifindex; | |
220 | else if (dev->ifindex == priv->oif) | |
221 | priv->oif = -1; | |
222 | break; | |
223 | } | |
224 | ||
225 | return NOTIFY_DONE; | |
226 | } | |
227 | ||
e281b198 JE |
228 | static int tee_tg_check(const struct xt_tgchk_param *par) |
229 | { | |
22265a5c PM |
230 | struct xt_tee_tginfo *info = par->targinfo; |
231 | struct xt_tee_priv *priv; | |
e281b198 | 232 | |
e281b198 | 233 | /* 0.0.0.0 and :: not allowed */ |
22265a5c PM |
234 | if (memcmp(&info->gw, &tee_zero_address, |
235 | sizeof(tee_zero_address)) == 0) | |
236 | return -EINVAL; | |
237 | ||
238 | if (info->oif[0]) { | |
239 | if (info->oif[sizeof(info->oif)-1] != '\0') | |
240 | return -EINVAL; | |
241 | ||
242 | priv = kzalloc(sizeof(*priv), GFP_KERNEL); | |
243 | if (priv == NULL) | |
244 | return -ENOMEM; | |
245 | ||
246 | priv->tginfo = info; | |
247 | priv->oif = -1; | |
248 | priv->notifier.notifier_call = tee_netdev_event; | |
249 | info->priv = priv; | |
250 | ||
251 | register_netdevice_notifier(&priv->notifier); | |
252 | } else | |
253 | info->priv = NULL; | |
254 | ||
255 | return 0; | |
256 | } | |
257 | ||
258 | static void tee_tg_destroy(const struct xt_tgdtor_param *par) | |
259 | { | |
260 | struct xt_tee_tginfo *info = par->targinfo; | |
261 | ||
262 | if (info->priv) { | |
263 | unregister_netdevice_notifier(&info->priv->notifier); | |
264 | kfree(info->priv); | |
265 | } | |
e281b198 JE |
266 | } |
267 | ||
268 | static struct xt_target tee_tg_reg[] __read_mostly = { | |
269 | { | |
270 | .name = "TEE", | |
271 | .revision = 1, | |
272 | .family = NFPROTO_IPV4, | |
273 | .target = tee_tg4, | |
274 | .targetsize = sizeof(struct xt_tee_tginfo), | |
275 | .checkentry = tee_tg_check, | |
22265a5c | 276 | .destroy = tee_tg_destroy, |
e281b198 JE |
277 | .me = THIS_MODULE, |
278 | }, | |
279 | #ifdef WITH_IPV6 | |
280 | { | |
281 | .name = "TEE", | |
282 | .revision = 1, | |
283 | .family = NFPROTO_IPV6, | |
284 | .target = tee_tg6, | |
285 | .targetsize = sizeof(struct xt_tee_tginfo), | |
286 | .checkentry = tee_tg_check, | |
22265a5c | 287 | .destroy = tee_tg_destroy, |
e281b198 JE |
288 | .me = THIS_MODULE, |
289 | }, | |
290 | #endif | |
291 | }; | |
292 | ||
293 | static int __init tee_tg_init(void) | |
294 | { | |
295 | return xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg)); | |
296 | } | |
297 | ||
298 | static void __exit tee_tg_exit(void) | |
299 | { | |
300 | xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg)); | |
301 | } | |
302 | ||
303 | module_init(tee_tg_init); | |
304 | module_exit(tee_tg_exit); | |
305 | MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>"); | |
306 | MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); | |
307 | MODULE_DESCRIPTION("Xtables: Reroute packet copy"); | |
308 | MODULE_LICENSE("GPL"); | |
309 | MODULE_ALIAS("ipt_TEE"); | |
310 | MODULE_ALIAS("ip6t_TEE"); |