net/core/netfilter.c

   1 /* netfilter.c: look after the filters for various protocols.
   2  * Heavily influenced by the old firewall.c by David Bonn and Alan Cox.
   3  *
   4  * Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
   5  * way.
   6  *
   7  * Rusty Russell (C)2000 -- This code is GPL.
   8  *
   9  * February 2000: Modified by James Morris to have 1 queue per protocol.
  10  * 15-Mar-2000:   Added NF_REPEAT --RR.
  11  */
  12 #include <linux/config.h>
  13 #include <linux/netfilter.h>
  14 #include <net/protocol.h>
  15 #include <linux/init.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/wait.h>
  18 #include <linux/module.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/if.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/inetdevice.h>
  23 #include <linux/tcp.h>
  24 #include <linux/udp.h>
  25 #include <linux/icmp.h>
  26 #include <net/sock.h>
  27 #include <net/route.h>
  28 #include <linux/ip.h>
  29
  30 #define __KERNEL_SYSCALLS__
  31 #include <linux/unistd.h>
  32
  33 /* In this code, we can be waiting indefinitely for userspace to
  34  * service a packet if a hook returns NF_QUEUE.  We could keep a count
  35  * of skbuffs queued for userspace, and not deregister a hook unless
  36  * this is zero, but that sucks.  Now, we simply check when the
  37  * packets come back: if the hook is gone, the packet is discarded. */
  38 #ifdef CONFIG_NETFILTER_DEBUG
  39 #define NFDEBUG(format, args...)  printk(format , ## args)
  40 #else
  41 #define NFDEBUG(format, args...)
  42 #endif
  43
  44 /* Sockopts only registered and called from user context, so
  45    net locking would be overkill.  Also, [gs]etsockopt calls may
  46    sleep. */
  47 static DECLARE_MUTEX(nf_sockopt_mutex);
  48
  49 struct list_head nf_hooks[NPROTO][NF_MAX_HOOKS];
  50 static LIST_HEAD(nf_sockopts);
  51 static spinlock_t nf_hook_lock = SPIN_LOCK_UNLOCKED;
  52
  53 /*
  54  * A queue handler may be registered for each protocol.  Each is protected by
  55  * long term mutex.  The handler must provide an an outfn() to accept packets
  56  * for queueing and must reinject all packets it receives, no matter what.
  57  */
  58 static struct nf_queue_handler_t {
  59         nf_queue_outfn_t outfn;
  60         void *data;
  61 } queue_handler[NPROTO];
  62 static rwlock_t queue_handler_lock = RW_LOCK_UNLOCKED;
  63
  64 int nf_register_hook(struct nf_hook_ops *reg)
  65 {
  66         struct list_head *i;
  67
  68         spin_lock_bh(&nf_hook_lock);
  69         list_for_each(i, &nf_hooks[reg->pf][reg->hooknum]) {
  70                 if (reg->priority < ((struct nf_hook_ops *)i)->priority)
  71                         break;
  72         }
  73         list_add_rcu(&reg->list, i->prev);
  74         spin_unlock_bh(&nf_hook_lock);
  75
  76         synchronize_net();
  77         return 0;
  78 }
  79
  80 void nf_unregister_hook(struct nf_hook_ops *reg)
  81 {
  82         spin_lock_bh(&nf_hook_lock);
  83         list_del_rcu(&reg->list);
  84         spin_unlock_bh(&nf_hook_lock);
  85
  86         synchronize_net();
  87 }
  88
  89 /* Do exclusive ranges overlap? */
  90 static inline int overlap(int min1, int max1, int min2, int max2)
  91 {
  92         return max1 > min2 && min1 < max2;
  93 }
  94
  95 /* Functions to register sockopt ranges (exclusive). */
  96 int nf_register_sockopt(struct nf_sockopt_ops *reg)
  97 {
  98         struct list_head *i;
  99         int ret = 0;
 100
 101         if (down_interruptible(&nf_sockopt_mutex) != 0)
 102                 return -EINTR;
 103
 104         for (i = nf_sockopts.next; i != &nf_sockopts; i = i->next) {
 105                 struct nf_sockopt_ops *ops = (struct nf_sockopt_ops *)i;
 106                 if (ops->pf == reg->pf
 107                     && (overlap(ops->set_optmin, ops->set_optmax,
 108                                 reg->set_optmin, reg->set_optmax)
 109                         || overlap(ops->get_optmin, ops->get_optmax,
 110                                    reg->get_optmin, reg->get_optmax))) {
 111                         NFDEBUG("nf_sock overlap: %u-%u/%u-%u v %u-%u/%u-%u\n",
 112                                 ops->set_optmin, ops->set_optmax,
 113                                 ops->get_optmin, ops->get_optmax,
 114                                 reg->set_optmin, reg->set_optmax,
 115                                 reg->get_optmin, reg->get_optmax);
 116                         ret = -EBUSY;
 117                         goto out;
 118                 }
 119         }
 120
 121         list_add(&reg->list, &nf_sockopts);
 122 out:
 123         up(&nf_sockopt_mutex);
 124         return ret;
 125 }
 126
 127 void nf_unregister_sockopt(struct nf_sockopt_ops *reg)
 128 {
 129         /* No point being interruptible: we're probably in cleanup_module() */
 130  restart:
 131         down(&nf_sockopt_mutex);
 132         if (reg->use != 0) {
 133                 /* To be woken by nf_sockopt call... */
 134                 /* FIXME: Stuart Young's name appears gratuitously. */
 135                 set_current_state(TASK_UNINTERRUPTIBLE);
 136                 reg->cleanup_task = current;
 137                 up(&nf_sockopt_mutex);
 138                 schedule();
 139                 goto restart;
 140         }
 141         list_del(&reg->list);
 142         up(&nf_sockopt_mutex);
 143 }
 144
 145 #ifdef CONFIG_NETFILTER_DEBUG
 146 #include <net/ip.h>
 147 #include <net/tcp.h>
 148 #include <linux/netfilter_ipv4.h>
 149
 150 static void debug_print_hooks_ip(unsigned int nf_debug)
 151 {
 152         if (nf_debug & (1 << NF_IP_PRE_ROUTING)) {
 153                 printk("PRE_ROUTING ");
 154                 nf_debug ^= (1 << NF_IP_PRE_ROUTING);
 155         }
 156         if (nf_debug & (1 << NF_IP_LOCAL_IN)) {
 157                 printk("LOCAL_IN ");
 158                 nf_debug ^= (1 << NF_IP_LOCAL_IN);
 159         }
 160         if (nf_debug & (1 << NF_IP_FORWARD)) {
 161                 printk("FORWARD ");
 162                 nf_debug ^= (1 << NF_IP_FORWARD);
 163         }
 164         if (nf_debug & (1 << NF_IP_LOCAL_OUT)) {
 165                 printk("LOCAL_OUT ");
 166                 nf_debug ^= (1 << NF_IP_LOCAL_OUT);
 167         }
 168         if (nf_debug & (1 << NF_IP_POST_ROUTING)) {
 169                 printk("POST_ROUTING ");
 170                 nf_debug ^= (1 << NF_IP_POST_ROUTING);
 171         }
 172         if (nf_debug)
 173                 printk("Crap bits: 0x%04X", nf_debug);
 174         printk("\n");
 175 }
 176
 177 void nf_dump_skb(int pf, struct sk_buff *skb)
 178 {
 179         printk("skb: pf=%i %s dev=%s len=%u\n",
 180                pf,
 181                skb->sk ? "(owned)" : "(unowned)",
 182                skb->dev ? skb->dev->name : "(no dev)",
 183                skb->len);
 184         switch (pf) {
 185         case PF_INET: {
 186                 const struct iphdr *ip = skb->nh.iph;
 187                 __u32 *opt = (__u32 *) (ip + 1);
 188                 int opti;
 189                 __u16 src_port = 0, dst_port = 0;
 190
 191                 if (ip->protocol == IPPROTO_TCP
 192                     || ip->protocol == IPPROTO_UDP) {
 193                         struct tcphdr *tcp=(struct tcphdr *)((__u32 *)ip+ip->ihl);
 194                         src_port = ntohs(tcp->source);
 195                         dst_port = ntohs(tcp->dest);
 196                 }
 197
 198                 printk("PROTO=%d %u.%u.%u.%u:%hu %u.%u.%u.%u:%hu"
 199                        " L=%hu S=0x%2.2hX I=%hu F=0x%4.4hX T=%hu",
 200                        ip->protocol, NIPQUAD(ip->saddr),
 201                        src_port, NIPQUAD(ip->daddr),
 202                        dst_port,
 203                        ntohs(ip->tot_len), ip->tos, ntohs(ip->id),
 204                        ntohs(ip->frag_off), ip->ttl);
 205
 206                 for (opti = 0; opti < (ip->ihl - sizeof(struct iphdr) / 4); opti++)
 207                         printk(" O=0x%8.8X", *opt++);
 208                 printk("\n");
 209         }
 210         }
 211 }
 212
 213 void nf_debug_ip_local_deliver(struct sk_buff *skb)
 214 {
 215         /* If it's a loopback packet, it must have come through
 216          * NF_IP_LOCAL_OUT, NF_IP_RAW_INPUT, NF_IP_PRE_ROUTING and
 217          * NF_IP_LOCAL_IN.  Otherwise, must have gone through
 218          * NF_IP_RAW_INPUT and NF_IP_PRE_ROUTING.  */
 219         if (!skb->dev) {
 220                 printk("ip_local_deliver: skb->dev is NULL.\n");
 221         }
 222         else if (strcmp(skb->dev->name, "lo") == 0) {
 223                 if (skb->nf_debug != ((1 << NF_IP_LOCAL_OUT)
 224                                       | (1 << NF_IP_POST_ROUTING)
 225                                       | (1 << NF_IP_PRE_ROUTING)
 226                                       | (1 << NF_IP_LOCAL_IN))) {
 227                         printk("ip_local_deliver: bad loopback skb: ");
 228                         debug_print_hooks_ip(skb->nf_debug);
 229                         nf_dump_skb(PF_INET, skb);
 230                 }
 231         }
 232         else {
 233                 if (skb->nf_debug != ((1<<NF_IP_PRE_ROUTING)
 234                                       | (1<<NF_IP_LOCAL_IN))) {
 235                         printk("ip_local_deliver: bad non-lo skb: ");
 236                         debug_print_hooks_ip(skb->nf_debug);
 237                         nf_dump_skb(PF_INET, skb);
 238                 }
 239         }
 240 }
 241
 242 void nf_debug_ip_loopback_xmit(struct sk_buff *newskb)
 243 {
 244         if (newskb->nf_debug != ((1 << NF_IP_LOCAL_OUT)
 245                                  | (1 << NF_IP_POST_ROUTING))) {
 246                 printk("ip_dev_loopback_xmit: bad owned skb = %p: ",
 247                        newskb);
 248                 debug_print_hooks_ip(newskb->nf_debug);
 249                 nf_dump_skb(PF_INET, newskb);
 250         }
 251         /* Clear to avoid confusing input check */
 252         newskb->nf_debug = 0;
 253 }
 254
 255 void nf_debug_ip_finish_output2(struct sk_buff *skb)
 256 {
 257         /* If it's owned, it must have gone through the
 258          * NF_IP_LOCAL_OUT and NF_IP_POST_ROUTING.
 259          * Otherwise, must have gone through
 260          * NF_IP_PRE_ROUTING, NF_IP_FORWARD and NF_IP_POST_ROUTING.
 261          */
 262         if (skb->sk) {
 263                 if (skb->nf_debug != ((1 << NF_IP_LOCAL_OUT)
 264                                       | (1 << NF_IP_POST_ROUTING))) {
 265                         printk("ip_finish_output: bad owned skb = %p: ", skb);
 266                         debug_print_hooks_ip(skb->nf_debug);
 267                         nf_dump_skb(PF_INET, skb);
 268                 }
 269         } else {
 270                 if (skb->nf_debug != ((1 << NF_IP_PRE_ROUTING)
 271                                       | (1 << NF_IP_FORWARD)
 272                                       | (1 << NF_IP_POST_ROUTING))) {
 273                         /* Fragments, entunnelled packets, TCP RSTs
 274                            generated by ipt_REJECT will have no
 275                            owners, but still may be local */
 276                         if (skb->nf_debug != ((1 << NF_IP_LOCAL_OUT)
 277                                               | (1 << NF_IP_POST_ROUTING))){
 278                                 printk("ip_finish_output:"
 279                                        " bad unowned skb = %p: ",skb);
 280                                 debug_print_hooks_ip(skb->nf_debug);
 281                                 nf_dump_skb(PF_INET, skb);
 282                         }
 283                 }
 284         }
 285 }
 286 #endif /*CONFIG_NETFILTER_DEBUG*/
 287
 288 /* Call get/setsockopt() */
 289 static int nf_sockopt(struct sock *sk, int pf, int val,
 290                       char *opt, int *len, int get)
 291 {
 292         struct list_head *i;
 293         struct nf_sockopt_ops *ops;
 294         int ret;
 295
 296         if (down_interruptible(&nf_sockopt_mutex) != 0)
 297                 return -EINTR;
 298
 299         for (i = nf_sockopts.next; i != &nf_sockopts; i = i->next) {
 300                 ops = (struct nf_sockopt_ops *)i;
 301                 if (ops->pf == pf) {
 302                         if (get) {
 303                                 if (val >= ops->get_optmin
 304                                     && val < ops->get_optmax) {
 305                                         ops->use++;
 306                                         up(&nf_sockopt_mutex);
 307                                         ret = ops->get(sk, val, opt, len);
 308                                         goto out;
 309                                 }
 310                         } else {
 311                                 if (val >= ops->set_optmin
 312                                     && val < ops->set_optmax) {
 313                                         ops->use++;
 314                                         up(&nf_sockopt_mutex);
 315                                         ret = ops->set(sk, val, opt, *len);
 316                                         goto out;
 317                                 }
 318                         }
 319                 }
 320         }
 321         up(&nf_sockopt_mutex);
 322         return -ENOPROTOOPT;
 323
 324  out:
 325         down(&nf_sockopt_mutex);
 326         ops->use--;
 327         if (ops->cleanup_task)
 328                 wake_up_process(ops->cleanup_task);
 329         up(&nf_sockopt_mutex);
 330         return ret;
 331 }
 332
 333 int nf_setsockopt(struct sock *sk, int pf, int val, char *opt,
 334                   int len)
 335 {
 336         return nf_sockopt(sk, pf, val, opt, &len, 0);
 337 }
 338
 339 int nf_getsockopt(struct sock *sk, int pf, int val, char *opt, int *len)
 340 {
 341         return nf_sockopt(sk, pf, val, opt, len, 1);
 342 }
 343
 344 static unsigned int nf_iterate(struct list_head *head,
 345                                struct sk_buff **skb,
 346                                int hook,
 347                                const struct net_device *indev,
 348                                const struct net_device *outdev,
 349                                struct list_head **i,
 350                                int (*okfn)(struct sk_buff *),
 351                                int hook_thresh)
 352 {
 353         /*
 354          * The caller must not block between calls to this
 355          * function because of risk of continuing from deleted element.
 356          */
 357         list_for_each_continue_rcu(*i, head) {
 358                 struct nf_hook_ops *elem = (struct nf_hook_ops *)*i;
 359
 360                 if (hook_thresh > elem->priority)
 361                         continue;
 362
 363                 /* Optimization: we don't need to hold module
 364                    reference here, since function can't sleep. --RR */
 365                 switch (elem->hook(hook, skb, indev, outdev, okfn)) {
 366                 case NF_QUEUE:
 367                         return NF_QUEUE;
 368
 369                 case NF_STOLEN:
 370                         return NF_STOLEN;
 371
 372                 case NF_DROP:
 373                         return NF_DROP;
 374
 375                 case NF_REPEAT:
 376                         *i = (*i)->prev;
 377                         break;
 378
 379 #ifdef CONFIG_NETFILTER_DEBUG
 380                 case NF_ACCEPT:
 381                         break;
 382
 383                 default:
 384                         NFDEBUG("Evil return from %p(%u).\n",
 385                                 elem->hook, hook);
 386 #endif
 387                 }
 388         }
 389         return NF_ACCEPT;
 390 }
 391
 392 int nf_register_queue_handler(int pf, nf_queue_outfn_t outfn, void *data)
 393 {
 394         int ret;
 395
 396         write_lock_bh(&queue_handler_lock);
 397         if (queue_handler[pf].outfn)
 398                 ret = -EBUSY;
 399         else {
 400                 queue_handler[pf].outfn = outfn;
 401                 queue_handler[pf].data = data;
 402                 ret = 0;
 403         }
 404         write_unlock_bh(&queue_handler_lock);
 405
 406         return ret;
 407 }
 408
 409 /* The caller must flush their queue before this */
 410 int nf_unregister_queue_handler(int pf)
 411 {
 412         write_lock_bh(&queue_handler_lock);
 413         queue_handler[pf].outfn = NULL;
 414         queue_handler[pf].data = NULL;
 415         write_unlock_bh(&queue_handler_lock);
 416
 417         return 0;
 418 }
 419
 420 /*
 421  * Any packet that leaves via this function must come back
 422  * through nf_reinject().
 423  */
 424 static int nf_queue(struct sk_buff *skb,
 425                     struct list_head *elem,
 426                     int pf, unsigned int hook,
 427                     struct net_device *indev,
 428                     struct net_device *outdev,
 429                     int (*okfn)(struct sk_buff *))
 430 {
 431         int status;
 432         struct nf_info *info;
 433 #if defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE)
 434         struct net_device *physindev = NULL;
 435         struct net_device *physoutdev = NULL;
 436 #endif
 437
 438         /* QUEUE == DROP if noone is waiting, to be safe. */
 439         read_lock(&queue_handler_lock);
 440         if (!queue_handler[pf].outfn) {
 441                 read_unlock(&queue_handler_lock);
 442                 kfree_skb(skb);
 443                 return 1;
 444         }
 445
 446         info = kmalloc(sizeof(*info), GFP_ATOMIC);
 447         if (!info) {
 448                 if (net_ratelimit())
 449                         printk(KERN_ERR "OOM queueing packet %p\n",
 450                                skb);
 451                 read_unlock(&queue_handler_lock);
 452                 kfree_skb(skb);
 453                 return 1;
 454         }
 455
 456         *info = (struct nf_info) {
 457                 (struct nf_hook_ops *)elem, pf, hook, indev, outdev, okfn };
 458
 459         /* If it's going away, ignore hook. */
 460         if (!try_module_get(info->elem->owner)) {
 461                 read_unlock(&queue_handler_lock);
 462                 kfree(info);
 463                 return 0;
 464         }
 465
 466         /* Bump dev refs so they don't vanish while packet is out */
 467         if (indev) dev_hold(indev);
 468         if (outdev) dev_hold(outdev);
 469
 470 #if defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE)
 471         if (skb->nf_bridge) {
 472                 physindev = skb->nf_bridge->physindev;
 473                 if (physindev) dev_hold(physindev);
 474                 physoutdev = skb->nf_bridge->physoutdev;
 475                 if (physoutdev) dev_hold(physoutdev);
 476         }
 477 #endif
 478
 479         status = queue_handler[pf].outfn(skb, info, queue_handler[pf].data);
 480         read_unlock(&queue_handler_lock);
 481
 482         if (status < 0) {
 483                 /* James M doesn't say fuck enough. */
 484                 if (indev) dev_put(indev);
 485                 if (outdev) dev_put(outdev);
 486 #if defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE)
 487                 if (physindev) dev_put(physindev);
 488                 if (physoutdev) dev_put(physoutdev);
 489 #endif
 490                 module_put(info->elem->owner);
 491                 kfree(info);
 492                 kfree_skb(skb);
 493                 return 1;
 494         }
 495         return 1;
 496 }
 497
 498 int nf_hook_slow(int pf, unsigned int hook, struct sk_buff *skb,
 499                  struct net_device *indev,
 500                  struct net_device *outdev,
 501                  int (*okfn)(struct sk_buff *),
 502                  int hook_thresh)
 503 {
 504         struct list_head *elem;
 505         unsigned int verdict;
 506         int ret = 0;
 507
 508         if (skb->ip_summed == CHECKSUM_HW) {
 509                 if (outdev == NULL) {
 510                         skb->ip_summed = CHECKSUM_NONE;
 511                 } else {
 512                         skb_checksum_help(skb);
 513                 }
 514         }
 515
 516         /* We may already have this, but read-locks nest anyway */
 517         rcu_read_lock();
 518
 519 #ifdef CONFIG_NETFILTER_DEBUG
 520         if (skb->nf_debug & (1 << hook)) {
 521                 printk("nf_hook: hook %i already set.\n", hook);
 522                 nf_dump_skb(pf, skb);
 523         }
 524         skb->nf_debug |= (1 << hook);
 525 #endif
 526
 527         elem = &nf_hooks[pf][hook];
 528  next_hook:
 529         verdict = nf_iterate(&nf_hooks[pf][hook], &skb, hook, indev,
 530                              outdev, &elem, okfn, hook_thresh);
 531         if (verdict == NF_QUEUE) {
 532                 NFDEBUG("nf_hook: Verdict = QUEUE.\n");
 533                 if (!nf_queue(skb, elem, pf, hook, indev, outdev, okfn))
 534                         goto next_hook;
 535         }
 536
 537         switch (verdict) {
 538         case NF_ACCEPT:
 539                 ret = okfn(skb);
 540                 break;
 541
 542         case NF_DROP:
 543                 kfree_skb(skb);
 544                 ret = -EPERM;
 545                 break;
 546         }
 547
 548         rcu_read_unlock();
 549         return ret;
 550 }
 551
 552 void nf_reinject(struct sk_buff *skb, struct nf_info *info,
 553                  unsigned int verdict)
 554 {
 555         struct list_head *elem = &info->elem->list;
 556         struct list_head *i;
 557
 558         rcu_read_lock();
 559
 560         /* Drop reference to owner of hook which queued us. */
 561         module_put(info->elem->owner);
 562
 563         list_for_each_rcu(i, &nf_hooks[info->pf][info->hook]) {
 564                 if (i == elem)
 565                         break;
 566         }
 567
 568         if (elem == &nf_hooks[info->pf][info->hook]) {
 569                 /* The module which sent it to userspace is gone. */
 570                 NFDEBUG("%s: module disappeared, dropping packet.\n",
 571                         __FUNCTION__);
 572                 verdict = NF_DROP;
 573         }
 574
 575         /* Continue traversal iff userspace said ok... */
 576         if (verdict == NF_REPEAT) {
 577                 elem = elem->prev;
 578                 verdict = NF_ACCEPT;
 579         }
 580
 581         if (verdict == NF_ACCEPT) {
 582         next_hook:
 583                 verdict = nf_iterate(&nf_hooks[info->pf][info->hook],
 584                                      &skb, info->hook,
 585                                      info->indev, info->outdev, &elem,
 586                                      info->okfn, INT_MIN);
 587         }
 588
 589         switch (verdict) {
 590         case NF_ACCEPT:
 591                 info->okfn(skb);
 592                 break;
 593
 594         case NF_QUEUE:
 595                 if (!nf_queue(skb, elem, info->pf, info->hook,
 596                               info->indev, info->outdev, info->okfn))
 597                         goto next_hook;
 598                 break;
 599         }
 600         rcu_read_unlock();
 601
 602         /* Release those devices we held, or Alexey will kill me. */
 603         if (info->indev) dev_put(info->indev);
 604         if (info->outdev) dev_put(info->outdev);
 605 #if defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE)
 606         if (skb->nf_bridge) {
 607                 if (skb->nf_bridge->physindev)
 608                         dev_put(skb->nf_bridge->physindev);
 609                 if (skb->nf_bridge->physoutdev)
 610                         dev_put(skb->nf_bridge->physoutdev);
 611         }
 612 #endif
 613
 614
 615         if (verdict == NF_DROP)
 616                 kfree_skb(skb);
 617
 618         kfree(info);
 619         return;
 620 }
 621
 622 #ifdef CONFIG_INET
 623 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
 624 int ip_route_me_harder(struct sk_buff **pskb)
 625 {
 626         struct iphdr *iph = (*pskb)->nh.iph;
 627         struct rtable *rt;
 628         struct flowi fl = {};
 629         struct dst_entry *odst;
 630         unsigned int hh_len;
 631
 632         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
 633          * packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook.
 634          */
 635         if (inet_addr_type(iph->saddr) == RTN_LOCAL) {
 636                 fl.nl_u.ip4_u.daddr = iph->daddr;
 637                 fl.nl_u.ip4_u.saddr = iph->saddr;
 638                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
 639                 fl.oif = (*pskb)->sk ? (*pskb)->sk->sk_bound_dev_if : 0;
 640 #ifdef CONFIG_IP_ROUTE_FWMARK
 641                 fl.nl_u.ip4_u.fwmark = (*pskb)->nfmark;
 642 #endif
 643                 if (ip_route_output_key(&rt, &fl) != 0)
 644                         return -1;
 645
 646                 /* Drop old route. */
 647                 dst_release((*pskb)->dst);
 648                 (*pskb)->dst = &rt->u.dst;
 649         } else {
 650                 /* non-local src, find valid iif to satisfy
 651                  * rp-filter when calling ip_route_input. */
 652                 fl.nl_u.ip4_u.daddr = iph->saddr;
 653                 if (ip_route_output_key(&rt, &fl) != 0)
 654                         return -1;
 655
 656                 odst = (*pskb)->dst;
 657                 if (ip_route_input(*pskb, iph->daddr, iph->saddr,
 658                                    RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
 659                         dst_release(&rt->u.dst);
 660                         return -1;
 661                 }
 662                 dst_release(&rt->u.dst);
 663                 dst_release(odst);
 664         }
 665
 666         if ((*pskb)->dst->error)
 667                 return -1;
 668
 669         /* Change in oif may mean change in hh_len. */
 670         hh_len = (*pskb)->dst->dev->hard_header_len;
 671         if (skb_headroom(*pskb) < hh_len) {
 672                 struct sk_buff *nskb;
 673
 674                 nskb = skb_realloc_headroom(*pskb, hh_len);
 675                 if (!nskb)
 676                         return -1;
 677                 if ((*pskb)->sk)
 678                         skb_set_owner_w(nskb, (*pskb)->sk);
 679                 kfree_skb(*pskb);
 680                 *pskb = nskb;
 681         }
 682
 683         return 0;
 684 }
 685
 686 int skb_ip_make_writable(struct sk_buff **pskb, unsigned int writable_len)
 687 {
 688         struct sk_buff *nskb;
 689         unsigned int iplen;
 690
 691         if (writable_len > (*pskb)->len)
 692                 return 0;
 693
 694         /* Not exclusive use of packet?  Must copy. */
 695         if (skb_shared(*pskb) || skb_cloned(*pskb))
 696                 goto copy_skb;
 697
 698         /* Alexey says IP hdr is always modifiable and linear, so ok. */
 699         if (writable_len <= (*pskb)->nh.iph->ihl*4)
 700                 return 1;
 701
 702         iplen = writable_len - (*pskb)->nh.iph->ihl*4;
 703
 704         /* DaveM says protocol headers are also modifiable. */
 705         switch ((*pskb)->nh.iph->protocol) {
 706         case IPPROTO_TCP: {
 707                 struct tcphdr hdr;
 708                 if (skb_copy_bits(*pskb, (*pskb)->nh.iph->ihl*4,
 709                                   &hdr, sizeof(hdr)) != 0)
 710                         goto copy_skb;
 711                 if (writable_len <= (*pskb)->nh.iph->ihl*4 + hdr.doff*4)
 712                         goto pull_skb;
 713                 goto copy_skb;
 714         }
 715         case IPPROTO_UDP:
 716                 if (writable_len<=(*pskb)->nh.iph->ihl*4+sizeof(struct udphdr))
 717                         goto pull_skb;
 718                 goto copy_skb;
 719         case IPPROTO_ICMP:
 720                 if (writable_len
 721                     <= (*pskb)->nh.iph->ihl*4 + sizeof(struct icmphdr))
 722                         goto pull_skb;
 723                 goto copy_skb;
 724         /* Insert other cases here as desired */
 725         }
 726
 727 copy_skb:
 728         nskb = skb_copy(*pskb, GFP_ATOMIC);
 729         if (!nskb)
 730                 return 0;
 731         BUG_ON(skb_is_nonlinear(nskb));
 732
 733         /* Rest of kernel will get very unhappy if we pass it a
 734            suddenly-orphaned skbuff */
 735         if ((*pskb)->sk)
 736                 skb_set_owner_w(nskb, (*pskb)->sk);
 737         kfree_skb(*pskb);
 738         *pskb = nskb;
 739         return 1;
 740
 741 pull_skb:
 742         return pskb_may_pull(*pskb, writable_len);
 743 }
 744 EXPORT_SYMBOL(skb_ip_make_writable);
 745 #endif /*CONFIG_INET*/
 746
 747
 748 /* This does not belong here, but ipt_REJECT needs it if connection
 749    tracking in use: without this, connection may not be in hash table,
 750    and hence manufactured ICMP or RST packets will not be associated
 751    with it. */
 752 void (*ip_ct_attach)(struct sk_buff *, struct nf_ct_info *);
 753
 754 void __init netfilter_init(void)
 755 {
 756         int i, h;
 757
 758         for (i = 0; i < NPROTO; i++) {
 759                 for (h = 0; h < NF_MAX_HOOKS; h++)
 760                         INIT_LIST_HEAD(&nf_hooks[i][h]);
 761         }
 762 }