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