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/seq_file.h>
  14 #include <linux/rcupdate.h>
  15 #include <net/protocol.h>
  16 #include <net/netfilter/nf_queue.h>
  17 #include <net/dst.h>
  18
  19 #include "nf_internals.h"
  20
  21 /*
  22  * Hook for nfnetlink_queue to register its queue handler.
  23  * We do this so that most of the NFQUEUE code can be modular.
  24  *
  25  * Once the queue is registered it must reinject all packets it
  26  * receives, no matter what.
  27  */
  28 static const struct nf_queue_handler __rcu *queue_handler __read_mostly;
  29
  30 /* return EBUSY when somebody else is registered, return EEXIST if the
  31  * same handler is registered, return 0 in case of success. */
  32 void nf_register_queue_handler(const struct nf_queue_handler *qh)
  33 {
  34         /* should never happen, we only have one queueing backend in kernel */
  35         WARN_ON(rcu_access_pointer(queue_handler));
  36         rcu_assign_pointer(queue_handler, qh);
  37 }
  38 EXPORT_SYMBOL(nf_register_queue_handler);
  39
  40 /* The caller must flush their queue before this */
  41 void nf_unregister_queue_handler(void)
  42 {
  43         RCU_INIT_POINTER(queue_handler, NULL);
  44         synchronize_rcu();
  45 }
  46 EXPORT_SYMBOL(nf_unregister_queue_handler);
  47
  48 void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
  49 {
  50         /* Release those devices we held, or Alexey will kill me. */
  51         if (entry->indev)
  52                 dev_put(entry->indev);
  53         if (entry->outdev)
  54                 dev_put(entry->outdev);
  55 #ifdef CONFIG_BRIDGE_NETFILTER
  56         if (entry->skb->nf_bridge) {
  57                 struct nf_bridge_info *nf_bridge = entry->skb->nf_bridge;
  58
  59                 if (nf_bridge->physindev)
  60                         dev_put(nf_bridge->physindev);
  61                 if (nf_bridge->physoutdev)
  62                         dev_put(nf_bridge->physoutdev);
  63         }
  64 #endif
  65         /* Drop reference to owner of hook which queued us. */
  66         module_put(entry->elem->owner);
  67 }
  68 EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);
  69
  70 /* Bump dev refs so they don't vanish while packet is out */
  71 bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
  72 {
  73         if (!try_module_get(entry->elem->owner))
  74                 return false;
  75
  76         if (entry->indev)
  77                 dev_hold(entry->indev);
  78         if (entry->outdev)
  79                 dev_hold(entry->outdev);
  80 #ifdef CONFIG_BRIDGE_NETFILTER
  81         if (entry->skb->nf_bridge) {
  82                 struct nf_bridge_info *nf_bridge = entry->skb->nf_bridge;
  83                 struct net_device *physdev;
  84
  85                 physdev = nf_bridge->physindev;
  86                 if (physdev)
  87                         dev_hold(physdev);
  88                 physdev = nf_bridge->physoutdev;
  89                 if (physdev)
  90                         dev_hold(physdev);
  91         }
  92 #endif
  93
  94         return true;
  95 }
  96 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
  97
  98 void nf_queue_nf_hook_drop(struct nf_hook_ops *ops)
  99 {
 100         const struct nf_queue_handler *qh;
 101         struct net *net;
 102
 103         rtnl_lock();
 104         rcu_read_lock();
 105         qh = rcu_dereference(queue_handler);
 106         if (qh) {
 107                 for_each_net(net) {
 108                         qh->nf_hook_drop(net, ops);
 109                 }
 110         }
 111         rcu_read_unlock();
 112         rtnl_unlock();
 113 }
 114
 115 /*
 116  * Any packet that leaves via this function must come back
 117  * through nf_reinject().
 118  */
 119 int nf_queue(struct sk_buff *skb,
 120                       struct nf_hook_ops *elem,
 121                       u_int8_t pf, unsigned int hook,
 122                       struct net_device *indev,
 123                       struct net_device *outdev,
 124                       int (*okfn)(struct sk_buff *),
 125                       unsigned int queuenum)
 126 {
 127         int status = -ENOENT;
 128         struct nf_queue_entry *entry = NULL;
 129         const struct nf_afinfo *afinfo;
 130         const struct nf_queue_handler *qh;
 131
 132         /* QUEUE == DROP if no one is waiting, to be safe. */
 133         rcu_read_lock();
 134
 135         qh = rcu_dereference(queue_handler);
 136         if (!qh) {
 137                 status = -ESRCH;
 138                 goto err_unlock;
 139         }
 140
 141         afinfo = nf_get_afinfo(pf);
 142         if (!afinfo)
 143                 goto err_unlock;
 144
 145         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 146         if (!entry) {
 147                 status = -ENOMEM;
 148                 goto err_unlock;
 149         }
 150
 151         *entry = (struct nf_queue_entry) {
 152                 .skb    = skb,
 153                 .elem   = elem,
 154                 .pf     = pf,
 155                 .hook   = hook,
 156                 .indev  = indev,
 157                 .outdev = outdev,
 158                 .okfn   = okfn,
 159                 .size   = sizeof(*entry) + afinfo->route_key_size,
 160         };
 161
 162         if (!nf_queue_entry_get_refs(entry)) {
 163                 status = -ECANCELED;
 164                 goto err_unlock;
 165         }
 166         skb_dst_force(skb);
 167         afinfo->saveroute(skb, entry);
 168         status = qh->outfn(entry, queuenum);
 169
 170         rcu_read_unlock();
 171
 172         if (status < 0) {
 173                 nf_queue_entry_release_refs(entry);
 174                 goto err;
 175         }
 176
 177         return 0;
 178
 179 err_unlock:
 180         rcu_read_unlock();
 181 err:
 182         kfree(entry);
 183         return status;
 184 }
 185
 186 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 187 {
 188         struct sk_buff *skb = entry->skb;
 189         struct nf_hook_ops *elem = entry->elem;
 190         const struct nf_afinfo *afinfo;
 191         int err;
 192
 193         rcu_read_lock();
 194
 195         nf_queue_entry_release_refs(entry);
 196
 197         /* Continue traversal iff userspace said ok... */
 198         if (verdict == NF_REPEAT) {
 199                 elem = list_entry(elem->list.prev, struct nf_hook_ops, list);
 200                 verdict = NF_ACCEPT;
 201         }
 202
 203         if (verdict == NF_ACCEPT) {
 204                 afinfo = nf_get_afinfo(entry->pf);
 205                 if (!afinfo || afinfo->reroute(skb, entry) < 0)
 206                         verdict = NF_DROP;
 207         }
 208
 209         if (verdict == NF_ACCEPT) {
 210         next_hook:
 211                 verdict = nf_iterate(&nf_hooks[entry->pf][entry->hook],
 212                                      skb, entry->hook,
 213                                      entry->indev, entry->outdev, &elem,
 214                                      entry->okfn, INT_MIN);
 215         }
 216
 217         switch (verdict & NF_VERDICT_MASK) {
 218         case NF_ACCEPT:
 219         case NF_STOP:
 220                 local_bh_disable();
 221                 entry->okfn(skb);
 222                 local_bh_enable();
 223                 break;
 224         case NF_QUEUE:
 225                 err = nf_queue(skb, elem, entry->pf, entry->hook,
 226                                 entry->indev, entry->outdev, entry->okfn,
 227                                 verdict >> NF_VERDICT_QBITS);
 228                 if (err < 0) {
 229                         if (err == -ECANCELED)
 230                                 goto next_hook;
 231                         if (err == -ESRCH &&
 232                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 233                                 goto next_hook;
 234                         kfree_skb(skb);
 235                 }
 236                 break;
 237         case NF_STOLEN:
 238                 break;
 239         default:
 240                 kfree_skb(skb);
 241         }
 242         rcu_read_unlock();
 243         kfree(entry);
 244 }
 245 EXPORT_SYMBOL(nf_reinject);