net/netfilter/nf_queue.c

   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_bridge.h>
  14 #include <linux/seq_file.h>
  15 #include <linux/rcupdate.h>
  16 #include <net/protocol.h>
  17 #include <net/netfilter/nf_queue.h>
  18 #include <net/dst.h>
  19
  20 #include "nf_internals.h"
  21
  22 /*
  23  * Hook for nfnetlink_queue to register its queue handler.
  24  * We do this so that most of the NFQUEUE code can be modular.
  25  *
  26  * Once the queue is registered it must reinject all packets it
  27  * receives, no matter what.
  28  */
  29 static const struct nf_queue_handler __rcu *queue_handler __read_mostly;
  30
  31 /* return EBUSY when somebody else is registered, return EEXIST if the
  32  * same handler is registered, return 0 in case of success. */
  33 void nf_register_queue_handler(const struct nf_queue_handler *qh)
  34 {
  35         /* should never happen, we only have one queueing backend in kernel */
  36         WARN_ON(rcu_access_pointer(queue_handler));
  37         rcu_assign_pointer(queue_handler, qh);
  38 }
  39 EXPORT_SYMBOL(nf_register_queue_handler);
  40
  41 /* The caller must flush their queue before this */
  42 void nf_unregister_queue_handler(void)
  43 {
  44         RCU_INIT_POINTER(queue_handler, NULL);
  45         synchronize_rcu();
  46 }
  47 EXPORT_SYMBOL(nf_unregister_queue_handler);
  48
  49 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 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  61         if (entry->skb->nf_bridge) {
  62                 struct net_device *physdev;
  63
  64                 physdev = nf_bridge_get_physindev(entry->skb);
  65                 if (physdev)
  66                         dev_put(physdev);
  67                 physdev = nf_bridge_get_physoutdev(entry->skb);
  68                 if (physdev)
  69                         dev_put(physdev);
  70         }
  71 #endif
  72         /* Drop reference to owner of hook which queued us. */
  73         module_put(entry->elem->owner);
  74 }
  75 EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);
  76
  77 /* Bump dev refs so they don't vanish while packet is out */
  78 bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
  79 {
  80         struct nf_hook_state *state = &entry->state;
  81
  82         if (!try_module_get(entry->elem->owner))
  83                 return false;
  84
  85         if (state->in)
  86                 dev_hold(state->in);
  87         if (state->out)
  88                 dev_hold(state->out);
  89         if (state->sk)
  90                 sock_hold(state->sk);
  91 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  92         if (entry->skb->nf_bridge) {
  93                 struct net_device *physdev;
  94
  95                 physdev = nf_bridge_get_physindev(entry->skb);
  96                 if (physdev)
  97                         dev_hold(physdev);
  98                 physdev = nf_bridge_get_physoutdev(entry->skb);
  99                 if (physdev)
 100                         dev_hold(physdev);
 101         }
 102 #endif
 103
 104         return true;
 105 }
 106 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
 107
 108 void nf_queue_nf_hook_drop(struct net *net, struct nf_hook_ops *ops)
 109 {
 110         const struct nf_queue_handler *qh;
 111
 112         rcu_read_lock();
 113         qh = rcu_dereference(queue_handler);
 114         if (qh)
 115                 qh->nf_hook_drop(net, ops);
 116         rcu_read_unlock();
 117 }
 118
 119 /*
 120  * Any packet that leaves via this function must come back
 121  * through nf_reinject().
 122  */
 123 int nf_queue(struct sk_buff *skb,
 124              struct nf_hook_ops *elem,
 125              struct nf_hook_state *state,
 126              unsigned int queuenum)
 127 {
 128         int status = -ENOENT;
 129         struct nf_queue_entry *entry = NULL;
 130         const struct nf_afinfo *afinfo;
 131         const struct nf_queue_handler *qh;
 132
 133         /* QUEUE == DROP if no one is waiting, to be safe. */
 134         rcu_read_lock();
 135
 136         qh = rcu_dereference(queue_handler);
 137         if (!qh) {
 138                 status = -ESRCH;
 139                 goto err_unlock;
 140         }
 141
 142         afinfo = nf_get_afinfo(state->pf);
 143         if (!afinfo)
 144                 goto err_unlock;
 145
 146         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 147         if (!entry) {
 148                 status = -ENOMEM;
 149                 goto err_unlock;
 150         }
 151
 152         *entry = (struct nf_queue_entry) {
 153                 .skb    = skb,
 154                 .elem   = elem,
 155                 .state  = *state,
 156                 .size   = sizeof(*entry) + afinfo->route_key_size,
 157         };
 158
 159         if (!nf_queue_entry_get_refs(entry)) {
 160                 status = -ECANCELED;
 161                 goto err_unlock;
 162         }
 163         skb_dst_force(skb);
 164         afinfo->saveroute(skb, entry);
 165         status = qh->outfn(entry, queuenum);
 166
 167         rcu_read_unlock();
 168
 169         if (status < 0) {
 170                 nf_queue_entry_release_refs(entry);
 171                 goto err;
 172         }
 173
 174         return 0;
 175
 176 err_unlock:
 177         rcu_read_unlock();
 178 err:
 179         kfree(entry);
 180         return status;
 181 }
 182
 183 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 184 {
 185         struct sk_buff *skb = entry->skb;
 186         struct nf_hook_ops *elem = entry->elem;
 187         const struct nf_afinfo *afinfo;
 188         int err;
 189
 190         rcu_read_lock();
 191
 192         nf_queue_entry_release_refs(entry);
 193
 194         /* Continue traversal iff userspace said ok... */
 195         if (verdict == NF_REPEAT) {
 196                 elem = list_entry(elem->list.prev, struct nf_hook_ops, list);
 197                 verdict = NF_ACCEPT;
 198         }
 199
 200         if (verdict == NF_ACCEPT) {
 201                 afinfo = nf_get_afinfo(entry->state.pf);
 202                 if (!afinfo || afinfo->reroute(skb, entry) < 0)
 203                         verdict = NF_DROP;
 204         }
 205
 206         entry->state.thresh = INT_MIN;
 207
 208         if (verdict == NF_ACCEPT) {
 209         next_hook:
 210                 verdict = nf_iterate(entry->state.hook_list,
 211                                      skb, &entry->state, &elem);
 212         }
 213
 214         switch (verdict & NF_VERDICT_MASK) {
 215         case NF_ACCEPT:
 216         case NF_STOP:
 217                 local_bh_disable();
 218                 entry->state.okfn(entry->state.sk, skb);
 219                 local_bh_enable();
 220                 break;
 221         case NF_QUEUE:
 222                 err = nf_queue(skb, elem, &entry->state,
 223                                verdict >> NF_VERDICT_QBITS);
 224                 if (err < 0) {
 225                         if (err == -ECANCELED)
 226                                 goto next_hook;
 227                         if (err == -ESRCH &&
 228                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 229                                 goto next_hook;
 230                         kfree_skb(skb);
 231                 }
 232                 break;
 233         case NF_STOLEN:
 234                 break;
 235         default:
 236                 kfree_skb(skb);
 237         }
 238         rcu_read_unlock();
 239         kfree(entry);
 240 }
 241 EXPORT_SYMBOL(nf_reinject);