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Linux/net/netfilter/nf_queue.c

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  1 /*
  2  * Rusty Russell (C)2000 -- This code is GPL.
  3  * Patrick McHardy (c) 2006-2012
  4  */
  5 
  6 #include <linux/kernel.h>
  7 #include <linux/slab.h>
  8 #include <linux/init.h>
  9 #include <linux/module.h>
 10 #include <linux/proc_fs.h>
 11 #include <linux/skbuff.h>
 12 #include <linux/netfilter.h>
 13 #include <linux/netfilter_ipv4.h>
 14 #include <linux/netfilter_ipv6.h>
 15 #include <linux/netfilter_bridge.h>
 16 #include <linux/seq_file.h>
 17 #include <linux/rcupdate.h>
 18 #include <net/protocol.h>
 19 #include <net/netfilter/nf_queue.h>
 20 #include <net/dst.h>
 21 
 22 #include "nf_internals.h"
 23 
 24 /*
 25  * Hook for nfnetlink_queue to register its queue handler.
 26  * We do this so that most of the NFQUEUE code can be modular.
 27  *
 28  * Once the queue is registered it must reinject all packets it
 29  * receives, no matter what.
 30  */
 31 
 32 /* return EBUSY when somebody else is registered, return EEXIST if the
 33  * same handler is registered, return 0 in case of success. */
 34 void nf_register_queue_handler(struct net *net, const struct nf_queue_handler *qh)
 35 {
 36         /* should never happen, we only have one queueing backend in kernel */
 37         WARN_ON(rcu_access_pointer(net->nf.queue_handler));
 38         rcu_assign_pointer(net->nf.queue_handler, qh);
 39 }
 40 EXPORT_SYMBOL(nf_register_queue_handler);
 41 
 42 /* The caller must flush their queue before this */
 43 void nf_unregister_queue_handler(struct net *net)
 44 {
 45         RCU_INIT_POINTER(net->nf.queue_handler, NULL);
 46 }
 47 EXPORT_SYMBOL(nf_unregister_queue_handler);
 48 
 49 static void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
 50 {
 51         struct nf_hook_state *state = &entry->state;
 52 
 53         /* Release those devices we held, or Alexey will kill me. */
 54         if (state->in)
 55                 dev_put(state->in);
 56         if (state->out)
 57                 dev_put(state->out);
 58         if (state->sk)
 59                 sock_put(state->sk);
 60 
 61 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 62         if (entry->physin)
 63                 dev_put(entry->physin);
 64         if (entry->physout)
 65                 dev_put(entry->physout);
 66 #endif
 67 }
 68 
 69 void nf_queue_entry_free(struct nf_queue_entry *entry)
 70 {
 71         nf_queue_entry_release_refs(entry);
 72         kfree(entry);
 73 }
 74 EXPORT_SYMBOL_GPL(nf_queue_entry_free);
 75 
 76 static void __nf_queue_entry_init_physdevs(struct nf_queue_entry *entry)
 77 {
 78 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 79         const struct sk_buff *skb = entry->skb;
 80         struct nf_bridge_info *nf_bridge;
 81 
 82         nf_bridge = nf_bridge_info_get(skb);
 83         if (nf_bridge) {
 84                 entry->physin = nf_bridge_get_physindev(skb);
 85                 entry->physout = nf_bridge_get_physoutdev(skb);
 86         } else {
 87                 entry->physin = NULL;
 88                 entry->physout = NULL;
 89         }
 90 #endif
 91 }
 92 
 93 /* Bump dev refs so they don't vanish while packet is out */
 94 void nf_queue_entry_get_refs(struct nf_queue_entry *entry)
 95 {
 96         struct nf_hook_state *state = &entry->state;
 97 
 98         if (state->in)
 99                 dev_hold(state->in);
100         if (state->out)
101                 dev_hold(state->out);
102         if (state->sk)
103                 sock_hold(state->sk);
104 
105 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
106         if (entry->physin)
107                 dev_hold(entry->physin);
108         if (entry->physout)
109                 dev_hold(entry->physout);
110 #endif
111 }
112 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
113 
114 void nf_queue_nf_hook_drop(struct net *net)
115 {
116         const struct nf_queue_handler *qh;
117 
118         rcu_read_lock();
119         qh = rcu_dereference(net->nf.queue_handler);
120         if (qh)
121                 qh->nf_hook_drop(net);
122         rcu_read_unlock();
123 }
124 EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop);
125 
126 static void nf_ip_saveroute(const struct sk_buff *skb,
127                             struct nf_queue_entry *entry)
128 {
129         struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
130 
131         if (entry->state.hook == NF_INET_LOCAL_OUT) {
132                 const struct iphdr *iph = ip_hdr(skb);
133 
134                 rt_info->tos = iph->tos;
135                 rt_info->daddr = iph->daddr;
136                 rt_info->saddr = iph->saddr;
137                 rt_info->mark = skb->mark;
138         }
139 }
140 
141 static void nf_ip6_saveroute(const struct sk_buff *skb,
142                              struct nf_queue_entry *entry)
143 {
144         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
145 
146         if (entry->state.hook == NF_INET_LOCAL_OUT) {
147                 const struct ipv6hdr *iph = ipv6_hdr(skb);
148 
149                 rt_info->daddr = iph->daddr;
150                 rt_info->saddr = iph->saddr;
151                 rt_info->mark = skb->mark;
152         }
153 }
154 
155 static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
156                       unsigned int index, unsigned int queuenum)
157 {
158         struct nf_queue_entry *entry = NULL;
159         const struct nf_queue_handler *qh;
160         struct net *net = state->net;
161         unsigned int route_key_size;
162         int status;
163 
164         /* QUEUE == DROP if no one is waiting, to be safe. */
165         qh = rcu_dereference(net->nf.queue_handler);
166         if (!qh)
167                 return -ESRCH;
168 
169         switch (state->pf) {
170         case AF_INET:
171                 route_key_size = sizeof(struct ip_rt_info);
172                 break;
173         case AF_INET6:
174                 route_key_size = sizeof(struct ip6_rt_info);
175                 break;
176         default:
177                 route_key_size = 0;
178                 break;
179         }
180 
181         entry = kmalloc(sizeof(*entry) + route_key_size, GFP_ATOMIC);
182         if (!entry)
183                 return -ENOMEM;
184 
185         if (skb_dst(skb) && !skb_dst_force(skb)) {
186                 kfree(entry);
187                 return -ENETDOWN;
188         }
189 
190         *entry = (struct nf_queue_entry) {
191                 .skb    = skb,
192                 .state  = *state,
193                 .hook_index = index,
194                 .size   = sizeof(*entry) + route_key_size,
195         };
196 
197         __nf_queue_entry_init_physdevs(entry);
198 
199         nf_queue_entry_get_refs(entry);
200 
201         switch (entry->state.pf) {
202         case AF_INET:
203                 nf_ip_saveroute(skb, entry);
204                 break;
205         case AF_INET6:
206                 nf_ip6_saveroute(skb, entry);
207                 break;
208         }
209 
210         status = qh->outfn(entry, queuenum);
211         if (status < 0) {
212                 nf_queue_entry_free(entry);
213                 return status;
214         }
215 
216         return 0;
217 }
218 
219 /* Packets leaving via this function must come back through nf_reinject(). */
220 int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
221              unsigned int index, unsigned int verdict)
222 {
223         int ret;
224 
225         ret = __nf_queue(skb, state, index, verdict >> NF_VERDICT_QBITS);
226         if (ret < 0) {
227                 if (ret == -ESRCH &&
228                     (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
229                         return 1;
230                 kfree_skb(skb);
231         }
232 
233         return 0;
234 }
235 EXPORT_SYMBOL_GPL(nf_queue);
236 
237 static unsigned int nf_iterate(struct sk_buff *skb,
238                                struct nf_hook_state *state,
239                                const struct nf_hook_entries *hooks,
240                                unsigned int *index)
241 {
242         const struct nf_hook_entry *hook;
243         unsigned int verdict, i = *index;
244 
245         while (i < hooks->num_hook_entries) {
246                 hook = &hooks->hooks[i];
247 repeat:
248                 verdict = nf_hook_entry_hookfn(hook, skb, state);
249                 if (verdict != NF_ACCEPT) {
250                         *index = i;
251                         if (verdict != NF_REPEAT)
252                                 return verdict;
253                         goto repeat;
254                 }
255                 i++;
256         }
257 
258         *index = i;
259         return NF_ACCEPT;
260 }
261 
262 static struct nf_hook_entries *nf_hook_entries_head(const struct net *net, u8 pf, u8 hooknum)
263 {
264         switch (pf) {
265 #ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
266         case NFPROTO_BRIDGE:
267                 return rcu_dereference(net->nf.hooks_bridge[hooknum]);
268 #endif
269         case NFPROTO_IPV4:
270                 return rcu_dereference(net->nf.hooks_ipv4[hooknum]);
271         case NFPROTO_IPV6:
272                 return rcu_dereference(net->nf.hooks_ipv6[hooknum]);
273         default:
274                 WARN_ON_ONCE(1);
275                 return NULL;
276         }
277 
278         return NULL;
279 }
280 
281 /* Caller must hold rcu read-side lock */
282 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
283 {
284         const struct nf_hook_entry *hook_entry;
285         const struct nf_hook_entries *hooks;
286         struct sk_buff *skb = entry->skb;
287         const struct net *net;
288         unsigned int i;
289         int err;
290         u8 pf;
291 
292         net = entry->state.net;
293         pf = entry->state.pf;
294 
295         hooks = nf_hook_entries_head(net, pf, entry->state.hook);
296 
297         i = entry->hook_index;
298         if (WARN_ON_ONCE(!hooks || i >= hooks->num_hook_entries)) {
299                 kfree_skb(skb);
300                 nf_queue_entry_free(entry);
301                 return;
302         }
303 
304         hook_entry = &hooks->hooks[i];
305 
306         /* Continue traversal iff userspace said ok... */
307         if (verdict == NF_REPEAT)
308                 verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);
309 
310         if (verdict == NF_ACCEPT) {
311                 if (nf_reroute(skb, entry) < 0)
312                         verdict = NF_DROP;
313         }
314 
315         if (verdict == NF_ACCEPT) {
316 next_hook:
317                 ++i;
318                 verdict = nf_iterate(skb, &entry->state, hooks, &i);
319         }
320 
321         switch (verdict & NF_VERDICT_MASK) {
322         case NF_ACCEPT:
323         case NF_STOP:
324                 local_bh_disable();
325                 entry->state.okfn(entry->state.net, entry->state.sk, skb);
326                 local_bh_enable();
327                 break;
328         case NF_QUEUE:
329                 err = nf_queue(skb, &entry->state, i, verdict);
330                 if (err == 1)
331                         goto next_hook;
332                 break;
333         case NF_STOLEN:
334                 break;
335         default:
336                 kfree_skb(skb);
337         }
338 
339         nf_queue_entry_free(entry);
340 }
341 EXPORT_SYMBOL(nf_reinject);
342 

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