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