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 static void nf_queue_sock_put(struct sock *sk)
  48 {
  49 #ifdef CONFIG_INET
  50         sock_gen_put(sk);
  51 #else
  52         sock_put(sk);
  53 #endif
  54 }
  55
  56 void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
  57 {
  58         struct nf_hook_state *state = &entry->state;
  59
  60         /* Release those devices we held, or Alexey will kill me. */
  61         if (state->in)
  62                 dev_put(state->in);
  63         if (state->out)
  64                 dev_put(state->out);
  65         if (state->sk)
  66                 nf_queue_sock_put(state->sk);
  67 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  68         if (entry->skb->nf_bridge) {
  69                 struct net_device *physdev;
  70
  71                 physdev = nf_bridge_get_physindev(entry->skb);
  72                 if (physdev)
  73                         dev_put(physdev);
  74                 physdev = nf_bridge_get_physoutdev(entry->skb);
  75                 if (physdev)
  76                         dev_put(physdev);
  77         }
  78 #endif
  79 }
  80 EXPORT_SYMBOL_GPL(nf_queue_entry_release_refs);
  81
  82 /* Bump dev refs so they don't vanish while packet is out */
  83 bool nf_queue_entry_get_refs(struct nf_queue_entry *entry)
  84 {
  85         struct nf_hook_state *state = &entry->state;
  86
  87         if (state->sk && !refcount_inc_not_zero(&state->sk->sk_refcnt))
  88                 return false;
  89
  90         if (state->in)
  91                 dev_hold(state->in);
  92         if (state->out)
  93                 dev_hold(state->out);
  94 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
  95         if (entry->skb->nf_bridge) {
  96                 struct net_device *physdev;
  97
  98                 physdev = nf_bridge_get_physindev(entry->skb);
  99                 if (physdev)
 100                         dev_hold(physdev);
 101                 physdev = nf_bridge_get_physoutdev(entry->skb);
 102                 if (physdev)
 103                         dev_hold(physdev);
 104         }
 105 #endif
 106         return true;
 107 }
 108 EXPORT_SYMBOL_GPL(nf_queue_entry_get_refs);
 109
 110 unsigned int nf_queue_nf_hook_drop(struct net *net)
 111 {
 112         const struct nf_queue_handler *qh;
 113         unsigned int count = 0;
 114
 115         rcu_read_lock();
 116         qh = rcu_dereference(net->nf.queue_handler);
 117         if (qh)
 118                 count = qh->nf_hook_drop(net);
 119         rcu_read_unlock();
 120
 121         return count;
 122 }
 123 EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop);
 124
 125 static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
 126                       const struct nf_hook_entries *entries,
 127                       unsigned int index, unsigned int queuenum)
 128 {
 129         int status = -ENOENT;
 130         struct nf_queue_entry *entry = NULL;
 131         const struct nf_afinfo *afinfo;
 132         const struct nf_queue_handler *qh;
 133         struct net *net = state->net;
 134
 135         /* QUEUE == DROP if no one is waiting, to be safe. */
 136         qh = rcu_dereference(net->nf.queue_handler);
 137         if (!qh) {
 138                 status = -ESRCH;
 139                 goto err;
 140         }
 141
 142         afinfo = nf_get_afinfo(state->pf);
 143         if (!afinfo)
 144                 goto err;
 145
 146         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 147         if (!entry) {
 148                 status = -ENOMEM;
 149                 goto err;
 150         }
 151
 152         if (skb_dst(skb) && !skb_dst_force(skb)) {
 153                 status = -ENETDOWN;
 154                 goto err;
 155         }
 156
 157         *entry = (struct nf_queue_entry) {
 158                 .skb    = skb,
 159                 .state  = *state,
 160                 .hook_index = index,
 161                 .size   = sizeof(*entry) + afinfo->route_key_size,
 162         };
 163
 164         if (!nf_queue_entry_get_refs(entry)) {
 165                 kfree(entry);
 166                 return -ENOTCONN;
 167         }
 168
 169         afinfo->saveroute(skb, entry);
 170         status = qh->outfn(entry, queuenum);
 171
 172         if (status < 0) {
 173                 nf_queue_entry_release_refs(entry);
 174                 goto err;
 175         }
 176
 177         return 0;
 178
 179 err:
 180         kfree(entry);
 181         return status;
 182 }
 183
 184 /* Packets leaving via this function must come back through nf_reinject(). */
 185 int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
 186              const struct nf_hook_entries *entries, unsigned int index,
 187              unsigned int verdict)
 188 {
 189         int ret;
 190
 191         ret = __nf_queue(skb, state, entries, index, verdict >> NF_VERDICT_QBITS);
 192         if (ret < 0) {
 193                 if (ret == -ESRCH &&
 194                     (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 195                         return 1;
 196                 kfree_skb(skb);
 197         }
 198
 199         return 0;
 200 }
 201
 202 static unsigned int nf_iterate(struct sk_buff *skb,
 203                                struct nf_hook_state *state,
 204                                const struct nf_hook_entries *hooks,
 205                                unsigned int *index)
 206 {
 207         const struct nf_hook_entry *hook;
 208         unsigned int verdict, i = *index;
 209
 210         while (i < hooks->num_hook_entries) {
 211                 hook = &hooks->hooks[i];
 212 repeat:
 213                 verdict = nf_hook_entry_hookfn(hook, skb, state);
 214                 if (verdict != NF_ACCEPT) {
 215                         *index = i;
 216                         if (verdict != NF_REPEAT)
 217                                 return verdict;
 218                         goto repeat;
 219                 }
 220                 i++;
 221         }
 222
 223         *index = i;
 224         return NF_ACCEPT;
 225 }
 226
 227 /* Caller must hold rcu read-side lock */
 228 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 229 {
 230         const struct nf_hook_entry *hook_entry;
 231         const struct nf_hook_entries *hooks;
 232         struct sk_buff *skb = entry->skb;
 233         const struct nf_afinfo *afinfo;
 234         const struct net *net;
 235         unsigned int i;
 236         int err;
 237         u8 pf;
 238
 239         net = entry->state.net;
 240         pf = entry->state.pf;
 241
 242         hooks = rcu_dereference(net->nf.hooks[pf][entry->state.hook]);
 243
 244         nf_queue_entry_release_refs(entry);
 245
 246         i = entry->hook_index;
 247         if (WARN_ON_ONCE(i >= hooks->num_hook_entries)) {
 248                 kfree_skb(skb);
 249                 kfree(entry);
 250                 return;
 251         }
 252
 253         hook_entry = &hooks->hooks[i];
 254
 255         /* Continue traversal iff userspace said ok... */
 256         if (verdict == NF_REPEAT)
 257                 verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);
 258
 259         if (verdict == NF_ACCEPT) {
 260                 afinfo = nf_get_afinfo(entry->state.pf);
 261                 if (!afinfo || afinfo->reroute(entry->state.net, skb, entry) < 0)
 262                         verdict = NF_DROP;
 263         }
 264
 265         if (verdict == NF_ACCEPT) {
 266 next_hook:
 267                 ++i;
 268                 verdict = nf_iterate(skb, &entry->state, hooks, &i);
 269         }
 270
 271         switch (verdict & NF_VERDICT_MASK) {
 272         case NF_ACCEPT:
 273         case NF_STOP:
 274                 local_bh_disable();
 275                 entry->state.okfn(entry->state.net, entry->state.sk, skb);
 276                 local_bh_enable();
 277                 break;
 278         case NF_QUEUE:
 279                 err = nf_queue(skb, &entry->state, hooks, i, verdict);
 280                 if (err == 1)
 281                         goto next_hook;
 282                 break;
 283         case NF_STOLEN:
 284                 break;
 285         default:
 286                 kfree_skb(skb);
 287         }
 288
 289         kfree(entry);
 290 }
 291 EXPORT_SYMBOL(nf_reinject);