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 #if IS_ENABLED(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 #if IS_ENABLED(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 /*
  99  * Any packet that leaves via this function must come back
 100  * through nf_reinject().
 101  */
 102 int nf_queue(struct sk_buff *skb,
 103                       struct nf_hook_ops *elem,
 104                       u_int8_t pf, unsigned int hook,
 105                       struct net_device *indev,
 106                       struct net_device *outdev,
 107                       int (*okfn)(struct sk_buff *),
 108                       unsigned int queuenum)
 109 {
 110         int status = -ENOENT;
 111         struct nf_queue_entry *entry = NULL;
 112         const struct nf_afinfo *afinfo;
 113         const struct nf_queue_handler *qh;
 114
 115         /* QUEUE == DROP if no one is waiting, to be safe. */
 116         rcu_read_lock();
 117
 118         qh = rcu_dereference(queue_handler);
 119         if (!qh) {
 120                 status = -ESRCH;
 121                 goto err_unlock;
 122         }
 123
 124         afinfo = nf_get_afinfo(pf);
 125         if (!afinfo)
 126                 goto err_unlock;
 127
 128         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 129         if (!entry) {
 130                 status = -ENOMEM;
 131                 goto err_unlock;
 132         }
 133
 134         *entry = (struct nf_queue_entry) {
 135                 .skb    = skb,
 136                 .elem   = elem,
 137                 .pf     = pf,
 138                 .hook   = hook,
 139                 .indev  = indev,
 140                 .outdev = outdev,
 141                 .okfn   = okfn,
 142                 .size   = sizeof(*entry) + afinfo->route_key_size,
 143         };
 144
 145         if (!nf_queue_entry_get_refs(entry)) {
 146                 status = -ECANCELED;
 147                 goto err_unlock;
 148         }
 149         skb_dst_force(skb);
 150         afinfo->saveroute(skb, entry);
 151         status = qh->outfn(entry, queuenum);
 152
 153         rcu_read_unlock();
 154
 155         if (status < 0) {
 156                 nf_queue_entry_release_refs(entry);
 157                 goto err;
 158         }
 159
 160         return 0;
 161
 162 err_unlock:
 163         rcu_read_unlock();
 164 err:
 165         kfree(entry);
 166         return status;
 167 }
 168
 169 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 170 {
 171         struct sk_buff *skb = entry->skb;
 172         struct nf_hook_ops *elem = entry->elem;
 173         const struct nf_afinfo *afinfo;
 174         int err;
 175
 176         rcu_read_lock();
 177
 178         nf_queue_entry_release_refs(entry);
 179
 180         /* Continue traversal iff userspace said ok... */
 181         if (verdict == NF_REPEAT) {
 182                 elem = list_entry(elem->list.prev, struct nf_hook_ops, list);
 183                 verdict = NF_ACCEPT;
 184         }
 185
 186         if (verdict == NF_ACCEPT) {
 187                 afinfo = nf_get_afinfo(entry->pf);
 188                 if (!afinfo || afinfo->reroute(skb, entry) < 0)
 189                         verdict = NF_DROP;
 190         }
 191
 192         if (verdict == NF_ACCEPT) {
 193         next_hook:
 194                 verdict = nf_iterate(&nf_hooks[entry->pf][entry->hook],
 195                                      skb, entry->hook,
 196                                      entry->indev, entry->outdev, &elem,
 197                                      entry->okfn, INT_MIN);
 198         }
 199
 200         switch (verdict & NF_VERDICT_MASK) {
 201         case NF_ACCEPT:
 202         case NF_STOP:
 203                 local_bh_disable();
 204                 entry->okfn(skb);
 205                 local_bh_enable();
 206                 break;
 207         case NF_QUEUE:
 208                 err = nf_queue(skb, elem, entry->pf, entry->hook,
 209                                 entry->indev, entry->outdev, entry->okfn,
 210                                 verdict >> NF_VERDICT_QBITS);
 211                 if (err < 0) {
 212                         if (err == -ECANCELED)
 213                                 goto next_hook;
 214                         if (err == -ESRCH &&
 215                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 216                                 goto next_hook;
 217                         kfree_skb(skb);
 218                 }
 219                 break;
 220         case NF_STOLEN:
 221                 break;
 222         default:
 223                 kfree_skb(skb);
 224         }
 225         rcu_read_unlock();
 226         kfree(entry);
 227 }
 228 EXPORT_SYMBOL(nf_reinject);