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_INIT_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_INIT_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 = -ENOENT;
 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 no one is waiting, to be safe. */
 138         rcu_read_lock();
 139
 140         qh = rcu_dereference(queue_handler[pf]);
 141         if (!qh) {
 142                 status = -ESRCH;
 143                 goto err_unlock;
 144         }
 145
 146         afinfo = nf_get_afinfo(pf);
 147         if (!afinfo)
 148                 goto err_unlock;
 149
 150         entry = kmalloc(sizeof(*entry) + afinfo->route_key_size, GFP_ATOMIC);
 151         if (!entry) {
 152                 status = -ENOMEM;
 153                 goto err_unlock;
 154         }
 155
 156         *entry = (struct nf_queue_entry) {
 157                 .skb    = skb,
 158                 .elem   = list_entry(elem, struct nf_hook_ops, list),
 159                 .pf     = pf,
 160                 .hook   = hook,
 161                 .indev  = indev,
 162                 .outdev = outdev,
 163                 .okfn   = okfn,
 164         };
 165
 166         /* If it's going away, ignore hook. */
 167         if (!try_module_get(entry->elem->owner)) {
 168                 status = -ECANCELED;
 169                 goto err_unlock;
 170         }
 171         /* Bump dev refs so they don't vanish while packet is out */
 172         if (indev)
 173                 dev_hold(indev);
 174         if (outdev)
 175                 dev_hold(outdev);
 176 #ifdef CONFIG_BRIDGE_NETFILTER
 177         if (skb->nf_bridge) {
 178                 physindev = skb->nf_bridge->physindev;
 179                 if (physindev)
 180                         dev_hold(physindev);
 181                 physoutdev = skb->nf_bridge->physoutdev;
 182                 if (physoutdev)
 183                         dev_hold(physoutdev);
 184         }
 185 #endif
 186         skb_dst_force(skb);
 187         afinfo->saveroute(skb, entry);
 188         status = qh->outfn(entry, queuenum);
 189
 190         rcu_read_unlock();
 191
 192         if (status < 0) {
 193                 nf_queue_entry_release_refs(entry);
 194                 goto err;
 195         }
 196
 197         return 0;
 198
 199 err_unlock:
 200         rcu_read_unlock();
 201 err:
 202         kfree(entry);
 203         return status;
 204 }
 205
 206 #ifdef CONFIG_BRIDGE_NETFILTER
 207 /* When called from bridge netfilter, skb->data must point to MAC header
 208  * before calling skb_gso_segment(). Else, original MAC header is lost
 209  * and segmented skbs will be sent to wrong destination.
 210  */
 211 static void nf_bridge_adjust_skb_data(struct sk_buff *skb)
 212 {
 213         if (skb->nf_bridge)
 214                 __skb_push(skb, skb->network_header - skb->mac_header);
 215 }
 216
 217 static void nf_bridge_adjust_segmented_data(struct sk_buff *skb)
 218 {
 219         if (skb->nf_bridge)
 220                 __skb_pull(skb, skb->network_header - skb->mac_header);
 221 }
 222 #else
 223 #define nf_bridge_adjust_skb_data(s) do {} while (0)
 224 #define nf_bridge_adjust_segmented_data(s) do {} while (0)
 225 #endif
 226
 227 int nf_queue(struct sk_buff *skb,
 228              struct list_head *elem,
 229              u_int8_t pf, unsigned int hook,
 230              struct net_device *indev,
 231              struct net_device *outdev,
 232              int (*okfn)(struct sk_buff *),
 233              unsigned int queuenum)
 234 {
 235         struct sk_buff *segs;
 236         int err = -EINVAL;
 237         unsigned int queued;
 238
 239         if (!skb_is_gso(skb))
 240                 return __nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
 241                                   queuenum);
 242
 243         switch (pf) {
 244         case NFPROTO_IPV4:
 245                 skb->protocol = htons(ETH_P_IP);
 246                 break;
 247         case NFPROTO_IPV6:
 248                 skb->protocol = htons(ETH_P_IPV6);
 249                 break;
 250         }
 251
 252         nf_bridge_adjust_skb_data(skb);
 253         segs = skb_gso_segment(skb, 0);
 254         /* Does not use PTR_ERR to limit the number of error codes that can be
 255          * returned by nf_queue.  For instance, callers rely on -ECANCELED to mean
 256          * 'ignore this hook'.
 257          */
 258         if (IS_ERR(segs))
 259                 goto out_err;
 260         queued = 0;
 261         err = 0;
 262         do {
 263                 struct sk_buff *nskb = segs->next;
 264
 265                 segs->next = NULL;
 266                 if (err == 0) {
 267                         nf_bridge_adjust_segmented_data(segs);
 268                         err = __nf_queue(segs, elem, pf, hook, indev,
 269                                            outdev, okfn, queuenum);
 270                 }
 271                 if (err == 0)
 272                         queued++;
 273                 else
 274                         kfree_skb(segs);
 275                 segs = nskb;
 276         } while (segs);
 277
 278         if (queued) {
 279                 kfree_skb(skb);
 280                 return 0;
 281         }
 282   out_err:
 283         nf_bridge_adjust_segmented_data(skb);
 284         return err;
 285 }
 286
 287 void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 288 {
 289         struct sk_buff *skb = entry->skb;
 290         struct list_head *elem = &entry->elem->list;
 291         const struct nf_afinfo *afinfo;
 292         int err;
 293
 294         rcu_read_lock();
 295
 296         nf_queue_entry_release_refs(entry);
 297
 298         /* Continue traversal iff userspace said ok... */
 299         if (verdict == NF_REPEAT) {
 300                 elem = elem->prev;
 301                 verdict = NF_ACCEPT;
 302         }
 303
 304         if (verdict == NF_ACCEPT) {
 305                 afinfo = nf_get_afinfo(entry->pf);
 306                 if (!afinfo || afinfo->reroute(skb, entry) < 0)
 307                         verdict = NF_DROP;
 308         }
 309
 310         if (verdict == NF_ACCEPT) {
 311         next_hook:
 312                 verdict = nf_iterate(&nf_hooks[entry->pf][entry->hook],
 313                                      skb, entry->hook,
 314                                      entry->indev, entry->outdev, &elem,
 315                                      entry->okfn, INT_MIN);
 316         }
 317
 318         switch (verdict & NF_VERDICT_MASK) {
 319         case NF_ACCEPT:
 320         case NF_STOP:
 321                 local_bh_disable();
 322                 entry->okfn(skb);
 323                 local_bh_enable();
 324                 break;
 325         case NF_QUEUE:
 326                 err = __nf_queue(skb, elem, entry->pf, entry->hook,
 327                                  entry->indev, entry->outdev, entry->okfn,
 328                                  verdict >> NF_VERDICT_QBITS);
 329                 if (err < 0) {
 330                         if (err == -ECANCELED)
 331                                 goto next_hook;
 332                         if (err == -ESRCH &&
 333                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 334                                 goto next_hook;
 335                         kfree_skb(skb);
 336                 }
 337                 break;
 338         case NF_STOLEN:
 339                 break;
 340         default:
 341                 kfree_skb(skb);
 342         }
 343         rcu_read_unlock();
 344         kfree(entry);
 345 }
 346 EXPORT_SYMBOL(nf_reinject);
 347
 348 #ifdef CONFIG_PROC_FS
 349 static void *seq_start(struct seq_file *seq, loff_t *pos)
 350 {
 351         if (*pos >= ARRAY_SIZE(queue_handler))
 352                 return NULL;
 353
 354         return pos;
 355 }
 356
 357 static void *seq_next(struct seq_file *s, void *v, loff_t *pos)
 358 {
 359         (*pos)++;
 360
 361         if (*pos >= ARRAY_SIZE(queue_handler))
 362                 return NULL;
 363
 364         return pos;
 365 }
 366
 367 static void seq_stop(struct seq_file *s, void *v)
 368 {
 369
 370 }
 371
 372 static int seq_show(struct seq_file *s, void *v)
 373 {
 374         int ret;
 375         loff_t *pos = v;
 376         const struct nf_queue_handler *qh;
 377
 378         rcu_read_lock();
 379         qh = rcu_dereference(queue_handler[*pos]);
 380         if (!qh)
 381                 ret = seq_printf(s, "%2lld NONE\n", *pos);
 382         else
 383                 ret = seq_printf(s, "%2lld %s\n", *pos, qh->name);
 384         rcu_read_unlock();
 385
 386         return ret;
 387 }
 388
 389 static const struct seq_operations nfqueue_seq_ops = {
 390         .start  = seq_start,
 391         .next   = seq_next,
 392         .stop   = seq_stop,
 393         .show   = seq_show,
 394 };
 395
 396 static int nfqueue_open(struct inode *inode, struct file *file)
 397 {
 398         return seq_open(file, &nfqueue_seq_ops);
 399 }
 400
 401 static const struct file_operations nfqueue_file_ops = {
 402         .owner   = THIS_MODULE,
 403         .open    = nfqueue_open,
 404         .read    = seq_read,
 405         .llseek  = seq_lseek,
 406         .release = seq_release,
 407 };
 408 #endif /* PROC_FS */
 409
 410
 411 int __init netfilter_queue_init(void)
 412 {
 413 #ifdef CONFIG_PROC_FS
 414         if (!proc_create("nf_queue", S_IRUGO,
 415                          proc_net_netfilter, &nfqueue_file_ops))
 416                 return -1;
 417 #endif
 418         return 0;
 419 }
 420