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 unsigned int nf_queue_nf_hook_drop(struct net *net)
 100 {
 101         const struct nf_queue_handler *qh;
 102         unsigned int count = 0;
 103
 104         rcu_read_lock();
 105         qh = rcu_dereference(net->nf.queue_handler);
 106         if (qh)
 107                 count = qh->nf_hook_drop(net);
 108         rcu_read_unlock();
 109
 110         return count;
 111 }
 112 EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop);
 113
 114 static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
 115                       const struct nf_hook_entries *entries,
 116                       unsigned int index, unsigned int queuenum)
 117 {
 118         int status = -ENOENT;
 119         struct nf_queue_entry *entry = NULL;
 120         const struct nf_afinfo *afinfo;
 121         const struct nf_queue_handler *qh;
 122         struct net *net = state->net;
 123
 124         /* QUEUE == DROP if no one is waiting, to be safe. */
 125         qh = rcu_dereference(net->nf.queue_handler);
 126         if (!qh) {
 127                 status = -ESRCH;
 128                 goto err;
 129         }
 130
 131         afinfo = nf_get_afinfo(state->pf);
 132         if (!afinfo)
 133                 goto err;
 134
 135         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 136         if (!entry) {
 137                 status = -ENOMEM;
 138                 goto err;
 139         }
 140
 141         if (skb_dst(skb) && !skb_dst_force(skb)) {
 142                 status = -ENETDOWN;
 143                 goto err;
 144         }
 145
 146         *entry = (struct nf_queue_entry) {
 147                 .skb    = skb,
 148                 .state  = *state,
 149                 .hook_index = index,
 150                 .size   = sizeof(*entry) + afinfo->route_key_size,
 151         };
 152
 153         nf_queue_entry_get_refs(entry);
 154         afinfo->saveroute(skb, entry);
 155         status = qh->outfn(entry, queuenum);
 156
 157         if (status < 0) {
 158                 nf_queue_entry_release_refs(entry);
 159                 goto err;
 160         }
 161
 162         return 0;
 163
 164 err:
 165         kfree(entry);
 166         return status;
 167 }
 168
 169 /* Packets leaving via this function must come back through nf_reinject(). */
 170 int nf_queue(struct sk_buff *skb, struct nf_hook_state *state,
 171              const struct nf_hook_entries *entries, unsigned int index,
 172              unsigned int verdict)
 173 {
 174         int ret;
 175
 176         ret = __nf_queue(skb, state, entries, index, verdict >> NF_VERDICT_QBITS);
 177         if (ret < 0) {
 178                 if (ret == -ESRCH &&
 179                     (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 180                         return 1;
 181                 kfree_skb(skb);
 182         }
 183
 184         return 0;
 185 }
 186
 187 static unsigned int nf_iterate(struct sk_buff *skb,
 188                                struct nf_hook_state *state,
 189                                const struct nf_hook_entries *hooks,
 190                                unsigned int *index)
 191 {
 192         const struct nf_hook_entry *hook;
 193         unsigned int verdict, i = *index;
 194
 195         while (i < hooks->num_hook_entries) {
 196                 hook = &hooks->hooks[i];
 197 repeat:
 198                 verdict = nf_hook_entry_hookfn(hook, skb, state);
 199                 if (verdict != NF_ACCEPT) {
 200                         *index = i;
 201                         if (verdict != NF_REPEAT)
 202                                 return verdict;
 203                         goto repeat;
 204                 }
 205                 i++;
 206         }
 207
 208         *index = i;
 209         return NF_ACCEPT;
 210 }
 211
 212 /* Caller must hold rcu read-side lock */
 213 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 214 {
 215         const struct nf_hook_entry *hook_entry;
 216         const struct nf_hook_entries *hooks;
 217         struct sk_buff *skb = entry->skb;
 218         const struct nf_afinfo *afinfo;
 219         const struct net *net;
 220         unsigned int i;
 221         int err;
 222         u8 pf;
 223
 224         net = entry->state.net;
 225         pf = entry->state.pf;
 226
 227         hooks = rcu_dereference(net->nf.hooks[pf][entry->state.hook]);
 228
 229         nf_queue_entry_release_refs(entry);
 230
 231         i = entry->hook_index;
 232         if (WARN_ON_ONCE(i >= hooks->num_hook_entries)) {
 233                 kfree_skb(skb);
 234                 kfree(entry);
 235                 return;
 236         }
 237
 238         hook_entry = &hooks->hooks[i];
 239
 240         /* Continue traversal iff userspace said ok... */
 241         if (verdict == NF_REPEAT)
 242                 verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);
 243
 244         if (verdict == NF_ACCEPT) {
 245                 afinfo = nf_get_afinfo(entry->state.pf);
 246                 if (!afinfo || afinfo->reroute(entry->state.net, skb, entry) < 0)
 247                         verdict = NF_DROP;
 248         }
 249
 250         if (verdict == NF_ACCEPT) {
 251 next_hook:
 252                 ++i;
 253                 verdict = nf_iterate(skb, &entry->state, hooks, &i);
 254         }
 255
 256         switch (verdict & NF_VERDICT_MASK) {
 257         case NF_ACCEPT:
 258         case NF_STOP:
 259                 local_bh_disable();
 260                 entry->state.okfn(entry->state.net, entry->state.sk, skb);
 261                 local_bh_enable();
 262                 break;
 263         case NF_QUEUE:
 264                 err = nf_queue(skb, &entry->state, hooks, i, verdict);
 265                 if (err == 1)
 266                         goto next_hook;
 267                 break;
 268         case NF_STOLEN:
 269                 break;
 270         default:
 271                 kfree_skb(skb);
 272         }
 273
 274         kfree(entry);
 275 }
 276 EXPORT_SYMBOL(nf_reinject);