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 nf_hook_ops *ops)
 109 {
 110         const struct nf_queue_handler *qh;
 111         struct net *net;
 112
 113         rtnl_lock();
 114         rcu_read_lock();
 115         qh = rcu_dereference(queue_handler);
 116         if (qh) {
 117                 for_each_net(net) {
 118                         qh->nf_hook_drop(net, ops);
 119                 }
 120         }
 121         rcu_read_unlock();
 122         rtnl_unlock();
 123 }
 124
 125 /*
 126  * Any packet that leaves via this function must come back
 127  * through nf_reinject().
 128  */
 129 int nf_queue(struct sk_buff *skb,
 130              struct nf_hook_ops *elem,
 131              struct nf_hook_state *state,
 132              unsigned int queuenum)
 133 {
 134         int status = -ENOENT;
 135         struct nf_queue_entry *entry = NULL;
 136         const struct nf_afinfo *afinfo;
 137         const struct nf_queue_handler *qh;
 138
 139         /* QUEUE == DROP if no one is waiting, to be safe. */
 140         rcu_read_lock();
 141
 142         qh = rcu_dereference(queue_handler);
 143         if (!qh) {
 144                 status = -ESRCH;
 145                 goto err_unlock;
 146         }
 147
 148         afinfo = nf_get_afinfo(state->pf);
 149         if (!afinfo)
 150                 goto err_unlock;
 151
 152         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 153         if (!entry) {
 154                 status = -ENOMEM;
 155                 goto err_unlock;
 156         }
 157
 158         *entry = (struct nf_queue_entry) {
 159                 .skb    = skb,
 160                 .elem   = elem,
 161                 .state  = *state,
 162                 .size   = sizeof(*entry) + afinfo->route_key_size,
 163         };
 164
 165         if (!nf_queue_entry_get_refs(entry)) {
 166                 status = -ECANCELED;
 167                 goto err_unlock;
 168         }
 169         skb_dst_force(skb);
 170         afinfo->saveroute(skb, entry);
 171         status = qh->outfn(entry, queuenum);
 172
 173         rcu_read_unlock();
 174
 175         if (status < 0) {
 176                 nf_queue_entry_release_refs(entry);
 177                 goto err;
 178         }
 179
 180         return 0;
 181
 182 err_unlock:
 183         rcu_read_unlock();
 184 err:
 185         kfree(entry);
 186         return status;
 187 }
 188
 189 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 190 {
 191         struct sk_buff *skb = entry->skb;
 192         struct nf_hook_ops *elem = entry->elem;
 193         const struct nf_afinfo *afinfo;
 194         int err;
 195
 196         rcu_read_lock();
 197
 198         nf_queue_entry_release_refs(entry);
 199
 200         /* Continue traversal iff userspace said ok... */
 201         if (verdict == NF_REPEAT) {
 202                 elem = list_entry(elem->list.prev, struct nf_hook_ops, list);
 203                 verdict = NF_ACCEPT;
 204         }
 205
 206         if (verdict == NF_ACCEPT) {
 207                 afinfo = nf_get_afinfo(entry->state.pf);
 208                 if (!afinfo || afinfo->reroute(skb, entry) < 0)
 209                         verdict = NF_DROP;
 210         }
 211
 212         entry->state.thresh = INT_MIN;
 213
 214         if (verdict == NF_ACCEPT) {
 215         next_hook:
 216                 verdict = nf_iterate(entry->state.hook_list,
 217                                      skb, &entry->state, &elem);
 218         }
 219
 220         switch (verdict & NF_VERDICT_MASK) {
 221         case NF_ACCEPT:
 222         case NF_STOP:
 223                 local_bh_disable();
 224                 entry->state.okfn(entry->state.sk, skb);
 225                 local_bh_enable();
 226                 break;
 227         case NF_QUEUE:
 228                 err = nf_queue(skb, elem, &entry->state,
 229                                verdict >> NF_VERDICT_QBITS);
 230                 if (err < 0) {
 231                         if (err == -ECANCELED)
 232                                 goto next_hook;
 233                         if (err == -ESRCH &&
 234                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 235                                 goto next_hook;
 236                         kfree_skb(skb);
 237                 }
 238                 break;
 239         case NF_STOLEN:
 240                 break;
 241         default:
 242                 kfree_skb(skb);
 243         }
 244         rcu_read_unlock();
 245         kfree(entry);
 246 }
 247 EXPORT_SYMBOL(nf_reinject);