22a2d421e7ebc5172761d51caea4298d47d7ebfb
[linux-3.10.git] / net / netfilter / xt_TEE.c
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>
15 #include <linux/percpu.h>
16 #include <linux/route.h>
17 #include <linux/skbuff.h>
18 #include <linux/notifier.h>
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
36 struct xt_tee_priv {
37         struct notifier_block   notifier;
38         struct xt_tee_tginfo    *tginfo;
39         int                     oif;
40 };
41
42 static const union nf_inet_addr tee_zero_address;
43 static DEFINE_PER_CPU(bool, tee_active);
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
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));
68         if (info->priv) {
69                 if (info->priv->oif == -1)
70                         return false;
71                 fl.oif = info->priv->oif;
72         }
73         fl.nl_u.ip4_u.daddr = info->gw.ip;
74         fl.nl_u.ip4_u.tos   = RT_TOS(iph->tos);
75         fl.nl_u.ip4_u.scope = RT_SCOPE_UNIVERSE;
76         if (ip_route_output_key(net, &rt, &fl) != 0)
77                 return false;
78
79         skb_dst_drop(skb);
80         skb_dst_set(skb, &rt->dst);
81         skb->dev      = rt->dst.dev;
82         skb->protocol = htons(ETH_P_IP);
83         return true;
84 }
85
86 static unsigned int
87 tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
88 {
89         const struct xt_tee_tginfo *info = par->targinfo;
90         struct iphdr *iph;
91
92         if (percpu_read(tee_active))
93                 return XT_CONTINUE;
94         /*
95          * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
96          * the original skb, which should continue on its way as if nothing has
97          * happened. The copy should be independently delivered to the TEE
98          * --gateway.
99          */
100         skb = pskb_copy(skb, GFP_ATOMIC);
101         if (skb == NULL)
102                 return XT_CONTINUE;
103
104 #ifdef WITH_CONNTRACK
105         /* Avoid counting cloned packets towards the original connection. */
106         nf_conntrack_put(skb->nfct);
107         skb->nfct     = &nf_ct_untracked_get()->ct_general;
108         skb->nfctinfo = IP_CT_NEW;
109         nf_conntrack_get(skb->nfct);
110 #endif
111         /*
112          * If we are in PREROUTING/INPUT, the checksum must be recalculated
113          * since the length could have changed as a result of defragmentation.
114          *
115          * We also decrease the TTL to mitigate potential TEE loops
116          * between two hosts.
117          *
118          * Set %IP_DF so that the original source is notified of a potentially
119          * decreased MTU on the clone route. IPv6 does this too.
120          */
121         iph = ip_hdr(skb);
122         iph->frag_off |= htons(IP_DF);
123         if (par->hooknum == NF_INET_PRE_ROUTING ||
124             par->hooknum == NF_INET_LOCAL_IN)
125                 --iph->ttl;
126         ip_send_check(iph);
127
128         if (tee_tg_route4(skb, info)) {
129                 percpu_write(tee_active, true);
130                 ip_local_out(skb);
131                 percpu_write(tee_active, false);
132         } else {
133                 kfree_skb(skb);
134         }
135         return XT_CONTINUE;
136 }
137
138 #ifdef WITH_IPV6
139 static bool
140 tee_tg_route6(struct sk_buff *skb, const struct xt_tee_tginfo *info)
141 {
142         const struct ipv6hdr *iph = ipv6_hdr(skb);
143         struct net *net = pick_net(skb);
144         struct dst_entry *dst;
145         struct flowi fl;
146
147         memset(&fl, 0, sizeof(fl));
148         if (info->priv) {
149                 if (info->priv->oif == -1)
150                         return false;
151                 fl.oif = info->priv->oif;
152         }
153         fl.nl_u.ip6_u.daddr = info->gw.in6;
154         fl.nl_u.ip6_u.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) |
155                                   (iph->flow_lbl[1] << 8) | iph->flow_lbl[2];
156         dst = ip6_route_output(net, NULL, &fl);
157         if (dst == NULL)
158                 return false;
159
160         skb_dst_drop(skb);
161         skb_dst_set(skb, dst);
162         skb->dev      = dst->dev;
163         skb->protocol = htons(ETH_P_IPV6);
164         return true;
165 }
166
167 static unsigned int
168 tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
169 {
170         const struct xt_tee_tginfo *info = par->targinfo;
171
172         if (percpu_read(tee_active))
173                 return XT_CONTINUE;
174         skb = pskb_copy(skb, GFP_ATOMIC);
175         if (skb == NULL)
176                 return XT_CONTINUE;
177
178 #ifdef WITH_CONNTRACK
179         nf_conntrack_put(skb->nfct);
180         skb->nfct     = &nf_ct_untracked_get()->ct_general;
181         skb->nfctinfo = IP_CT_NEW;
182         nf_conntrack_get(skb->nfct);
183 #endif
184         if (par->hooknum == NF_INET_PRE_ROUTING ||
185             par->hooknum == NF_INET_LOCAL_IN) {
186                 struct ipv6hdr *iph = ipv6_hdr(skb);
187                 --iph->hop_limit;
188         }
189         if (tee_tg_route6(skb, info)) {
190                 percpu_write(tee_active, true);
191                 ip6_local_out(skb);
192                 percpu_write(tee_active, false);
193         } else {
194                 kfree_skb(skb);
195         }
196         return XT_CONTINUE;
197 }
198 #endif /* WITH_IPV6 */
199
200 static int tee_netdev_event(struct notifier_block *this, unsigned long event,
201                             void *ptr)
202 {
203         struct net_device *dev = ptr;
204         struct xt_tee_priv *priv;
205
206         priv = container_of(this, struct xt_tee_priv, notifier);
207         switch (event) {
208         case NETDEV_REGISTER:
209                 if (!strcmp(dev->name, priv->tginfo->oif))
210                         priv->oif = dev->ifindex;
211                 break;
212         case NETDEV_UNREGISTER:
213                 if (dev->ifindex == priv->oif)
214                         priv->oif = -1;
215                 break;
216         case NETDEV_CHANGENAME:
217                 if (!strcmp(dev->name, priv->tginfo->oif))
218                         priv->oif = dev->ifindex;
219                 else if (dev->ifindex == priv->oif)
220                         priv->oif = -1;
221                 break;
222         }
223
224         return NOTIFY_DONE;
225 }
226
227 static int tee_tg_check(const struct xt_tgchk_param *par)
228 {
229         struct xt_tee_tginfo *info = par->targinfo;
230         struct xt_tee_priv *priv;
231
232         /* 0.0.0.0 and :: not allowed */
233         if (memcmp(&info->gw, &tee_zero_address,
234                    sizeof(tee_zero_address)) == 0)
235                 return -EINVAL;
236
237         if (info->oif[0]) {
238                 if (info->oif[sizeof(info->oif)-1] != '\0')
239                         return -EINVAL;
240
241                 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
242                 if (priv == NULL)
243                         return -ENOMEM;
244
245                 priv->tginfo  = info;
246                 priv->oif     = -1;
247                 priv->notifier.notifier_call = tee_netdev_event;
248                 info->priv    = priv;
249
250                 register_netdevice_notifier(&priv->notifier);
251         } else
252                 info->priv = NULL;
253
254         return 0;
255 }
256
257 static void tee_tg_destroy(const struct xt_tgdtor_param *par)
258 {
259         struct xt_tee_tginfo *info = par->targinfo;
260
261         if (info->priv) {
262                 unregister_netdevice_notifier(&info->priv->notifier);
263                 kfree(info->priv);
264         }
265 }
266
267 static struct xt_target tee_tg_reg[] __read_mostly = {
268         {
269                 .name       = "TEE",
270                 .revision   = 1,
271                 .family     = NFPROTO_IPV4,
272                 .target     = tee_tg4,
273                 .targetsize = sizeof(struct xt_tee_tginfo),
274                 .checkentry = tee_tg_check,
275                 .destroy    = tee_tg_destroy,
276                 .me         = THIS_MODULE,
277         },
278 #ifdef WITH_IPV6
279         {
280                 .name       = "TEE",
281                 .revision   = 1,
282                 .family     = NFPROTO_IPV6,
283                 .target     = tee_tg6,
284                 .targetsize = sizeof(struct xt_tee_tginfo),
285                 .checkentry = tee_tg_check,
286                 .destroy    = tee_tg_destroy,
287                 .me         = THIS_MODULE,
288         },
289 #endif
290 };
291
292 static int __init tee_tg_init(void)
293 {
294         return xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
295 }
296
297 static void __exit tee_tg_exit(void)
298 {
299         xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
300 }
301
302 module_init(tee_tg_init);
303 module_exit(tee_tg_exit);
304 MODULE_AUTHOR("Sebastian Claßen <sebastian.classen@freenet.ag>");
305 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
306 MODULE_DESCRIPTION("Xtables: Reroute packet copy");
307 MODULE_LICENSE("GPL");
308 MODULE_ALIAS("ipt_TEE");
309 MODULE_ALIAS("ip6t_TEE");