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 }
  73 EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);
  74
  75 /* Bump dev refs so they don't vanish while packet is out */
  76 void nf_queue_entry_get_refs(struct nf_queue_entry *entry)
  77 {
  78         struct nf_hook_state *state = &entry->state;
  79
  80         if (state->in)
  81                 dev_hold(state->in);
  82         if (state->out)
  83                 dev_hold(state->out);
  84         if (state->sk)
  85                 sock_hold(state->sk);
  86 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  87         if (entry->skb->nf_bridge) {
  88                 struct net_device *physdev;
  89
  90                 physdev = nf_bridge_get_physindev(entry->skb);
  91                 if (physdev)
  92                         dev_hold(physdev);
  93                 physdev = nf_bridge_get_physoutdev(entry->skb);
  94                 if (physdev)
  95                         dev_hold(physdev);
  96         }
  97 #endif
  98 }
  99 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
 100
 101 void nf_queue_nf_hook_drop(struct net *net, struct nf_hook_ops *ops)
 102 {
 103         const struct nf_queue_handler *qh;
 104
 105         rcu_read_lock();
 106         qh = rcu_dereference(queue_handler);
 107         if (qh)
 108                 qh->nf_hook_drop(net, ops);
 109         rcu_read_unlock();
 110 }
 111
 112 /*
 113  * Any packet that leaves via this function must come back
 114  * through nf_reinject().
 115  */
 116 int nf_queue(struct sk_buff *skb,
 117              struct nf_hook_ops *elem,
 118              struct nf_hook_state *state,
 119              unsigned int queuenum)
 120 {
 121         int status = -ENOENT;
 122         struct nf_queue_entry *entry = NULL;
 123         const struct nf_afinfo *afinfo;
 124         const struct nf_queue_handler *qh;
 125
 126         /* QUEUE == DROP if no one is waiting, to be safe. */
 127         qh = rcu_dereference(queue_handler);
 128         if (!qh) {
 129                 status = -ESRCH;
 130                 goto err;
 131         }
 132
 133         afinfo = nf_get_afinfo(state->pf);
 134         if (!afinfo)
 135                 goto err;
 136
 137         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 138         if (!entry) {
 139                 status = -ENOMEM;
 140                 goto err;
 141         }
 142
 143         *entry = (struct nf_queue_entry) {
 144                 .skb    = skb,
 145                 .elem   = elem,
 146                 .state  = *state,
 147                 .size   = sizeof(*entry) + afinfo->route_key_size,
 148         };
 149
 150         nf_queue_entry_get_refs(entry);
 151         skb_dst_force(skb);
 152         afinfo->saveroute(skb, entry);
 153         status = qh->outfn(entry, queuenum);
 154
 155         if (status < 0) {
 156                 nf_queue_entry_release_refs(entry);
 157                 goto err;
 158         }
 159
 160         return 0;
 161
 162 err:
 163         kfree(entry);
 164         return status;
 165 }
 166
 167 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 168 {
 169         struct sk_buff *skb = entry->skb;
 170         struct nf_hook_ops *elem = entry->elem;
 171         const struct nf_afinfo *afinfo;
 172         int err;
 173
 174         nf_queue_entry_release_refs(entry);
 175
 176         /* Continue traversal iff userspace said ok... */
 177         if (verdict == NF_REPEAT)
 178                 verdict = elem->hook(elem->priv, skb, &entry->state);
 179
 180         if (verdict == NF_ACCEPT) {
 181                 afinfo = nf_get_afinfo(entry->state.pf);
 182                 if (!afinfo || afinfo->reroute(entry->state.net, skb, entry) < 0)
 183                         verdict = NF_DROP;
 184         }
 185
 186         entry->state.thresh = INT_MIN;
 187
 188         if (verdict == NF_ACCEPT) {
 189         next_hook:
 190                 verdict = nf_iterate(entry->state.hook_list,
 191                                      skb, &entry->state, &elem);
 192         }
 193
 194         switch (verdict & NF_VERDICT_MASK) {
 195         case NF_ACCEPT:
 196         case NF_STOP:
 197                 local_bh_disable();
 198                 entry->state.okfn(entry->state.net, entry->state.sk, skb);
 199                 local_bh_enable();
 200                 break;
 201         case NF_QUEUE:
 202                 err = nf_queue(skb, elem, &entry->state,
 203                                verdict >> NF_VERDICT_QBITS);
 204                 if (err < 0) {
 205                         if (err == -ESRCH &&
 206                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 207                                 goto next_hook;
 208                         kfree_skb(skb);
 209                 }
 210                 break;
 211         case NF_STOLEN:
 212                 break;
 213         default:
 214                 kfree_skb(skb);
 215         }
 216
 217         kfree(entry);
 218 }
 219 EXPORT_SYMBOL(nf_reinject);