net/netfilter/nf_queue.c

   1 #include <linux/kernel.h>
   2 #include <linux/slab.h>
   3 #include <linux/init.h>
   4 #include <linux/module.h>
   5 #include <linux/proc_fs.h>
   6 #include <linux/skbuff.h>
   7 #include <linux/netfilter.h>
   8 #include <linux/seq_file.h>
   9 #include <linux/rcupdate.h>
  10 #include <net/protocol.h>
  11 #include <net/netfilter/nf_queue.h>
  12 #include <net/dst.h>
  13
  14 #include "nf_internals.h"
  15
  16 /*
  17  * A queue handler may be registered for each protocol.  Each is protected by
  18  * long term mutex.  The handler must provide an an outfn() to accept packets
  19  * for queueing and must reinject all packets it receives, no matter what.
  20  */
  21 static const struct nf_queue_handler __rcu *queue_handler[NFPROTO_NUMPROTO] __read_mostly;
  22
  23 static DEFINE_MUTEX(queue_handler_mutex);
  24
  25 /* return EBUSY when somebody else is registered, return EEXIST if the
  26  * same handler is registered, return 0 in case of success. */
  27 int nf_register_queue_handler(u_int8_t pf, const struct nf_queue_handler *qh)
  28 {
  29         int ret;
  30         const struct nf_queue_handler *old;
  31
  32         if (pf >= ARRAY_SIZE(queue_handler))
  33                 return -EINVAL;
  34
  35         mutex_lock(&queue_handler_mutex);
  36         old = rcu_dereference_protected(queue_handler[pf],
  37                                         lockdep_is_held(&queue_handler_mutex));
  38         if (old == qh)
  39                 ret = -EEXIST;
  40         else if (old)
  41                 ret = -EBUSY;
  42         else {
  43                 rcu_assign_pointer(queue_handler[pf], qh);
  44                 ret = 0;
  45         }
  46         mutex_unlock(&queue_handler_mutex);
  47
  48         return ret;
  49 }
  50 EXPORT_SYMBOL(nf_register_queue_handler);
  51
  52 /* The caller must flush their queue before this */
  53 int nf_unregister_queue_handler(u_int8_t pf, const struct nf_queue_handler *qh)
  54 {
  55         const struct nf_queue_handler *old;
  56
  57         if (pf >= ARRAY_SIZE(queue_handler))
  58                 return -EINVAL;
  59
  60         mutex_lock(&queue_handler_mutex);
  61         old = rcu_dereference_protected(queue_handler[pf],
  62                                         lockdep_is_held(&queue_handler_mutex));
  63         if (old && old != qh) {
  64                 mutex_unlock(&queue_handler_mutex);
  65                 return -EINVAL;
  66         }
  67
  68         rcu_assign_pointer(queue_handler[pf], NULL);
  69         mutex_unlock(&queue_handler_mutex);
  70
  71         synchronize_rcu();
  72
  73         return 0;
  74 }
  75 EXPORT_SYMBOL(nf_unregister_queue_handler);
  76
  77 void nf_unregister_queue_handlers(const struct nf_queue_handler *qh)
  78 {
  79         u_int8_t pf;
  80
  81         mutex_lock(&queue_handler_mutex);
  82         for (pf = 0; pf < ARRAY_SIZE(queue_handler); pf++)  {
  83                 if (rcu_dereference_protected(
  84                                 queue_handler[pf],
  85                                 lockdep_is_held(&queue_handler_mutex)
  86                                 ) == qh)
  87                         rcu_assign_pointer(queue_handler[pf], NULL);
  88         }
  89         mutex_unlock(&queue_handler_mutex);
  90
  91         synchronize_rcu();
  92 }
  93 EXPORT_SYMBOL_GPL(nf_unregister_queue_handlers);
  94
  95 static void nf_queue_entry_release_refs(struct nf_queue_entry *entry)
  96 {
  97         /* Release those devices we held, or Alexey will kill me. */
  98         if (entry->indev)
  99                 dev_put(entry->indev);
 100         if (entry->outdev)
 101                 dev_put(entry->outdev);
 102 #ifdef CONFIG_BRIDGE_NETFILTER
 103         if (entry->skb->nf_bridge) {
 104                 struct nf_bridge_info *nf_bridge = entry->skb->nf_bridge;
 105
 106                 if (nf_bridge->physindev)
 107                         dev_put(nf_bridge->physindev);
 108                 if (nf_bridge->physoutdev)
 109                         dev_put(nf_bridge->physoutdev);
 110         }
 111 #endif
 112         /* Drop reference to owner of hook which queued us. */
 113         module_put(entry->elem->owner);
 114 }
 115
 116 /*
 117  * Any packet that leaves via this function must come back
 118  * through nf_reinject().
 119  */
 120 static int __nf_queue(struct sk_buff *skb,
 121                       struct list_head *elem,
 122                       u_int8_t pf, unsigned int hook,
 123                       struct net_device *indev,
 124                       struct net_device *outdev,
 125                       int (*okfn)(struct sk_buff *),
 126                       unsigned int queuenum)
 127 {
 128         int status;
 129         struct nf_queue_entry *entry = NULL;
 130 #ifdef CONFIG_BRIDGE_NETFILTER
 131         struct net_device *physindev;
 132         struct net_device *physoutdev;
 133 #endif
 134         const struct nf_afinfo *afinfo;
 135         const struct nf_queue_handler *qh;
 136
 137         /* QUEUE == DROP if noone is waiting, to be safe. */
 138         rcu_read_lock();
 139
 140         qh = rcu_dereference(queue_handler[pf]);
 141         if (!qh)
 142                 goto err_unlock;
 143
 144         afinfo = nf_get_afinfo(pf);
 145         if (!afinfo)
 146                 goto err_unlock;
 147
 148         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 149         if (!entry)
 150                 goto err_unlock;
 151
 152         *entry = (struct nf_queue_entry) {
 153                 .skb    = skb,
 154                 .elem   = list_entry(elem, struct nf_hook_ops, list),
 155                 .pf     = pf,
 156                 .hook   = hook,
 157                 .indev  = indev,
 158                 .outdev = outdev,
 159                 .okfn   = okfn,
 160         };
 161
 162         /* If it's going away, ignore hook. */
 163         if (!try_module_get(entry->elem->owner)) {
 164                 rcu_read_unlock();
 165                 kfree(entry);
 166                 return 0;
 167         }
 168
 169         /* Bump dev refs so they don't vanish while packet is out */
 170         if (indev)
 171                 dev_hold(indev);
 172         if (outdev)
 173                 dev_hold(outdev);
 174 #ifdef CONFIG_BRIDGE_NETFILTER
 175         if (skb->nf_bridge) {
 176                 physindev = skb->nf_bridge->physindev;
 177                 if (physindev)
 178                         dev_hold(physindev);
 179                 physoutdev = skb->nf_bridge->physoutdev;
 180                 if (physoutdev)
 181                         dev_hold(physoutdev);
 182         }
 183 #endif
 184         skb_dst_force(skb);
 185         afinfo->saveroute(skb, entry);
 186         status = qh->outfn(entry, queuenum);
 187
 188         rcu_read_unlock();
 189
 190         if (status < 0) {
 191                 nf_queue_entry_release_refs(entry);
 192                 goto err;
 193         }
 194
 195         return 1;
 196
 197 err_unlock:
 198         rcu_read_unlock();
 199 err:
 200         kfree_skb(skb);
 201         kfree(entry);
 202         return 1;
 203 }
 204
 205 int nf_queue(struct sk_buff *skb,
 206              struct list_head *elem,
 207              u_int8_t pf, unsigned int hook,
 208              struct net_device *indev,
 209              struct net_device *outdev,
 210              int (*okfn)(struct sk_buff *),
 211              unsigned int queuenum)
 212 {
 213         struct sk_buff *segs;
 214
 215         if (!skb_is_gso(skb))
 216                 return __nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
 217                                   queuenum);
 218
 219         switch (pf) {
 220         case NFPROTO_IPV4:
 221                 skb->protocol = htons(ETH_P_IP);
 222                 break;
 223         case NFPROTO_IPV6:
 224                 skb->protocol = htons(ETH_P_IPV6);
 225                 break;
 226         }
 227
 228         segs = skb_gso_segment(skb, 0);
 229         kfree_skb(skb);
 230         if (IS_ERR(segs))
 231                 return 1;
 232
 233         do {
 234                 struct sk_buff *nskb = segs->next;
 235
 236                 segs->next = NULL;
 237                 if (!__nf_queue(segs, elem, pf, hook, indev, outdev, okfn,
 238                                 queuenum))
 239                         kfree_skb(segs);
 240                 segs = nskb;
 241         } while (segs);
 242         return 1;
 243 }
 244
 245 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 246 {
 247         struct sk_buff *skb = entry->skb;
 248         struct list_head *elem = &entry->elem->list;
 249         const struct nf_afinfo *afinfo;
 250
 251         rcu_read_lock();
 252
 253         nf_queue_entry_release_refs(entry);
 254
 255         /* Continue traversal iff userspace said ok... */
 256         if (verdict == NF_REPEAT) {
 257                 elem = elem->prev;
 258                 verdict = NF_ACCEPT;
 259         }
 260
 261         if (verdict == NF_ACCEPT) {
 262                 afinfo = nf_get_afinfo(entry->pf);
 263                 if (!afinfo || afinfo->reroute(skb, entry) < 0)
 264                         verdict = NF_DROP;
 265         }
 266
 267         if (verdict == NF_ACCEPT) {
 268         next_hook:
 269                 verdict = nf_iterate(&nf_hooks[entry->pf][entry->hook],
 270                                      skb, entry->hook,
 271                                      entry->indev, entry->outdev, &elem,
 272                                      entry->okfn, INT_MIN);
 273         }
 274
 275         switch (verdict & NF_VERDICT_MASK) {
 276         case NF_ACCEPT:
 277         case NF_STOP:
 278                 local_bh_disable();
 279                 entry->okfn(skb);
 280                 local_bh_enable();
 281                 break;
 282         case NF_QUEUE:
 283                 if (!__nf_queue(skb, elem, entry->pf, entry->hook,
 284                                 entry->indev, entry->outdev, entry->okfn,
 285                                 verdict >> NF_VERDICT_BITS))
 286                         goto next_hook;
 287                 break;
 288         case NF_STOLEN:
 289         default:
 290                 kfree_skb(skb);
 291         }
 292         rcu_read_unlock();
 293         kfree(entry);
 294 }
 295 EXPORT_SYMBOL(nf_reinject);
 296
 297 #ifdef CONFIG_PROC_FS
 298 static void *seq_start(struct seq_file *seq, loff_t *pos)
 299 {
 300         if (*pos >= ARRAY_SIZE(queue_handler))
 301                 return NULL;
 302
 303         return pos;
 304 }
 305
 306 static void *seq_next(struct seq_file *s, void *v, loff_t *pos)
 307 {
 308         (*pos)++;
 309
 310         if (*pos >= ARRAY_SIZE(queue_handler))
 311                 return NULL;
 312
 313         return pos;
 314 }
 315
 316 static void seq_stop(struct seq_file *s, void *v)
 317 {
 318
 319 }
 320
 321 static int seq_show(struct seq_file *s, void *v)
 322 {
 323         int ret;
 324         loff_t *pos = v;
 325         const struct nf_queue_handler *qh;
 326
 327         rcu_read_lock();
 328         qh = rcu_dereference(queue_handler[*pos]);
 329         if (!qh)
 330                 ret = seq_printf(s, "%2lld NONE\n", *pos);
 331         else
 332                 ret = seq_printf(s, "%2lld %s\n", *pos, qh->name);
 333         rcu_read_unlock();
 334
 335         return ret;
 336 }
 337
 338 static const struct seq_operations nfqueue_seq_ops = {
 339         .start  = seq_start,
 340         .next   = seq_next,
 341         .stop   = seq_stop,
 342         .show   = seq_show,
 343 };
 344
 345 static int nfqueue_open(struct inode *inode, struct file *file)
 346 {
 347         return seq_open(file, &nfqueue_seq_ops);
 348 }
 349
 350 static const struct file_operations nfqueue_file_ops = {
 351         .owner   = THIS_MODULE,
 352         .open    = nfqueue_open,
 353         .read    = seq_read,
 354         .llseek  = seq_lseek,
 355         .release = seq_release,
 356 };
 357 #endif /* PROC_FS */
 358
 359
 360 int __init netfilter_queue_init(void)
 361 {
 362 #ifdef CONFIG_PROC_FS
 363         if (!proc_create("nf_queue", S_IRUGO,
 364                          proc_net_netfilter, &nfqueue_file_ops))
 365                 return -1;
 366 #endif
 367         return 0;
 368 }
 369