mac80211: fix another race in aggregation start
[linux-2.6.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 flowi4 fl4;
66
67         memset(&fl4, 0, sizeof(fl4));
68         if (info->priv) {
69                 if (info->priv->oif == -1)
70                         return false;
71                 fl4.flowi4_oif = info->priv->oif;
72         }
73         fl4.daddr = info->gw.ip;
74         fl4.flowi4_tos = RT_TOS(iph->tos);
75         fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
76         rt = ip_route_output_key(net, &fl4);
77         if (IS_ERR(rt))
78                 return false;
79
80         skb_dst_drop(skb);
81         skb_dst_set(skb, &rt->dst);
82         skb->dev      = rt->dst.dev;
83         skb->protocol = htons(ETH_P_IP);
84         return true;
85 }
86
87 static unsigned int
88 tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
89 {
90         const struct xt_tee_tginfo *info = par->targinfo;
91         struct iphdr *iph;
92
93         if (percpu_read(tee_active))
94                 return XT_CONTINUE;
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);
108         skb->nfct     = &nf_ct_untracked_get()->ct_general;
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
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 {
134                 kfree_skb(skb);
135         }
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 flowi6 fl6;
147
148         memset(&fl6, 0, sizeof(fl6));
149         if (info->priv) {
150                 if (info->priv->oif == -1)
151                         return false;
152                 fl6.flowi6_oif = info->priv->oif;
153         }
154         fl6.daddr = info->gw.in6;
155         fl6.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) |
156                            (iph->flow_lbl[1] << 8) | iph->flow_lbl[2];
157         dst = ip6_route_output(net, NULL, &fl6);
158         if (dst == NULL)
159                 return false;
160
161         skb_dst_drop(skb);
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
169 tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
170 {
171         const struct xt_tee_tginfo *info = par->targinfo;
172
173         if (percpu_read(tee_active))
174                 return XT_CONTINUE;
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);
181         skb->nfct     = &nf_ct_untracked_get()->ct_general;
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         }
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 {
195                 kfree_skb(skb);
196         }
197         return XT_CONTINUE;
198 }
199 #endif /* WITH_IPV6 */
200
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
228 static int tee_tg_check(const struct xt_tgchk_param *par)
229 {
230         struct xt_tee_tginfo *info = par->targinfo;
231         struct xt_tee_priv *priv;
232
233         /* 0.0.0.0 and :: not allowed */
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         }
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,
276                 .destroy    = tee_tg_destroy,
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,
287                 .destroy    = tee_tg_destroy,
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");