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
  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(struct net *net, 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(net->nf.queue_handler));
  36         rcu_assign_pointer(net->nf.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(struct net *net)
  42 {
  43         RCU_INIT_POINTER(net->nf.queue_handler, NULL);
  44 }
  45 EXPORT_SYMBOL(nf_unregister_queue_handler);
  46
  47 void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
  48 {
  49         struct nf_hook_state *state = &entry->state;
  50
  51         /* Release those devices we held, or Alexey will kill me. */
  52         if (state->in)
  53                 dev_put(state->in);
  54         if (state->out)
  55                 dev_put(state->out);
  56         if (state->sk)
  57                 sock_put(state->sk);
  58 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  59         if (entry->skb->nf_bridge) {
  60                 struct net_device *physdev;
  61
  62                 physdev = nf_bridge_get_physindev(entry->skb);
  63                 if (physdev)
  64                         dev_put(physdev);
  65                 physdev = nf_bridge_get_physoutdev(entry->skb);
  66                 if (physdev)
  67                         dev_put(physdev);
  68         }
  69 #endif
  70 }
  71 EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);
  72
  73 /* Bump dev refs so they don't vanish while packet is out */
  74 void nf_queue_entry_get_refs(struct nf_queue_entry *entry)
  75 {
  76         struct nf_hook_state *state = &entry->state;
  77
  78         if (state->in)
  79                 dev_hold(state->in);
  80         if (state->out)
  81                 dev_hold(state->out);
  82         if (state->sk)
  83                 sock_hold(state->sk);
  84 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  85         if (entry->skb->nf_bridge) {
  86                 struct net_device *physdev;
  87
  88                 physdev = nf_bridge_get_physindev(entry->skb);
  89                 if (physdev)
  90                         dev_hold(physdev);
  91                 physdev = nf_bridge_get_physoutdev(entry->skb);
  92                 if (physdev)
  93                         dev_hold(physdev);
  94         }
  95 #endif
  96 }
  97 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
  98
  99 void nf_queue_nf_hook_drop(struct net *net, const struct nf_hook_entry *entry)
 100 {
 101         const struct nf_queue_handler *qh;
 102
 103         rcu_read_lock();
 104         qh = rcu_dereference(net->nf.queue_handler);
 105         if (qh)
 106                 qh->nf_hook_drop(net, entry);
 107         rcu_read_unlock();
 108 }
 109
 110 static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
 111                       struct nf_hook_entry *hook_entry, unsigned int queuenum)
 112 {
 113         int status = -ENOENT;
 114         struct nf_queue_entry *entry = NULL;
 115         const struct nf_afinfo *afinfo;
 116         const struct nf_queue_handler *qh;
 117         struct net *net = state->net;
 118
 119         /* QUEUE == DROP if no one is waiting, to be safe. */
 120         qh = rcu_dereference(net->nf.queue_handler);
 121         if (!qh) {
 122                 status = -ESRCH;
 123                 goto err;
 124         }
 125
 126         afinfo = nf_get_afinfo(state->pf);
 127         if (!afinfo)
 128                 goto err;
 129
 130         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 131         if (!entry) {
 132                 status = -ENOMEM;
 133                 goto err;
 134         }
 135
 136         *entry = (struct nf_queue_entry) {
 137                 .skb    = skb,
 138                 .state  = *state,
 139                 .hook   = hook_entry,
 140                 .size   = sizeof(*entry) + afinfo->route_key_size,
 141         };
 142
 143         nf_queue_entry_get_refs(entry);
 144         skb_dst_force(skb);
 145         afinfo->saveroute(skb, entry);
 146         status = qh->outfn(entry, queuenum);
 147
 148         if (status < 0) {
 149                 nf_queue_entry_release_refs(entry);
 150                 goto err;
 151         }
 152
 153         return 0;
 154
 155 err:
 156         kfree(entry);
 157         return status;
 158 }
 159
 160 /* Packets leaving via this function must come back through nf_reinject(). */
 161 int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
 162              struct nf_hook_entry **entryp, unsigned int verdict)
 163 {
 164         struct nf_hook_entry *entry = *entryp;
 165         int ret;
 166
 167         ret = __nf_queue(skb, state, entry, verdict >> NF_VERDICT_QBITS);
 168         if (ret < 0) {
 169                 if (ret == -ESRCH &&
 170                     (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS)) {
 171                         *entryp = rcu_dereference(entry->next);
 172                         return 1;
 173                 }
 174                 kfree_skb(skb);
 175         }
 176
 177         return 0;
 178 }
 179
 180 static unsigned int nf_iterate(struct sk_buff *skb,
 181                                struct nf_hook_state *state,
 182                                struct nf_hook_entry **entryp)
 183 {
 184         unsigned int verdict;
 185
 186         do {
 187 repeat:
 188                 verdict = nf_hook_entry_hookfn((*entryp), skb, state);
 189                 if (verdict != NF_ACCEPT) {
 190                         if (verdict != NF_REPEAT)
 191                                 return verdict;
 192                         goto repeat;
 193                 }
 194                 *entryp = rcu_dereference((*entryp)->next);
 195         } while (*entryp);
 196
 197         return NF_ACCEPT;
 198 }
 199
 200 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 201 {
 202         struct nf_hook_entry *hook_entry = entry->hook;
 203         struct sk_buff *skb = entry->skb;
 204         const struct nf_afinfo *afinfo;
 205         int err;
 206
 207         nf_queue_entry_release_refs(entry);
 208
 209         /* Continue traversal iff userspace said ok... */
 210         if (verdict == NF_REPEAT)
 211                 verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);
 212
 213         if (verdict == NF_ACCEPT) {
 214                 afinfo = nf_get_afinfo(entry->state.pf);
 215                 if (!afinfo || afinfo->reroute(entry->state.net, skb, entry) < 0)
 216                         verdict = NF_DROP;
 217         }
 218
 219         if (verdict == NF_ACCEPT) {
 220                 hook_entry = rcu_dereference(hook_entry->next);
 221                 if (hook_entry)
 222 next_hook:
 223                         verdict = nf_iterate(skb, &entry->state, &hook_entry);
 224         }
 225
 226         switch (verdict & NF_VERDICT_MASK) {
 227         case NF_ACCEPT:
 228         case NF_STOP:
 229 okfn:
 230                 local_bh_disable();
 231                 entry->state.okfn(entry->state.net, entry->state.sk, skb);
 232                 local_bh_enable();
 233                 break;
 234         case NF_QUEUE:
 235                 err = nf_queue(skb, &entry->state, &hook_entry, verdict);
 236                 if (err == 1) {
 237                         if (hook_entry)
 238                                 goto next_hook;
 239                         goto okfn;
 240                 }
 241                 break;
 242         case NF_STOLEN:
 243                 break;
 244         default:
 245                 kfree_skb(skb);
 246         }
 247
 248         kfree(entry);
 249 }
 250 EXPORT_SYMBOL(nf_reinject);