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