net/ipv4/fib_semantics.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              IPv4 Forwarding Information Base: semantics.
   7  *
   8  * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
   9  *
  10  *              This program is free software; you can redistribute it and/or
  11  *              modify it under the terms of the GNU General Public License
  12  *              as published by the Free Software Foundation; either version
  13  *              2 of the License, or (at your option) any later version.
  14  */
  15
  16 #include <asm/uaccess.h>
  17 #include <linux/bitops.h>
  18 #include <linux/types.h>
  19 #include <linux/kernel.h>
  20 #include <linux/jiffies.h>
  21 #include <linux/mm.h>
  22 #include <linux/string.h>
  23 #include <linux/socket.h>
  24 #include <linux/sockios.h>
  25 #include <linux/errno.h>
  26 #include <linux/in.h>
  27 #include <linux/inet.h>
  28 #include <linux/inetdevice.h>
  29 #include <linux/netdevice.h>
  30 #include <linux/if_arp.h>
  31 #include <linux/proc_fs.h>
  32 #include <linux/skbuff.h>
  33 #include <linux/init.h>
  34 #include <linux/slab.h>
  35
  36 #include <net/arp.h>
  37 #include <net/ip.h>
  38 #include <net/protocol.h>
  39 #include <net/route.h>
  40 #include <net/tcp.h>
  41 #include <net/sock.h>
  42 #include <net/ip_fib.h>
  43 #include <net/netlink.h>
  44 #include <net/nexthop.h>
  45
  46 #include "fib_lookup.h"
  47
  48 static DEFINE_SPINLOCK(fib_info_lock);
  49 static struct hlist_head *fib_info_hash;
  50 static struct hlist_head *fib_info_laddrhash;
  51 static unsigned int fib_info_hash_size;
  52 static unsigned int fib_info_cnt;
  53
  54 #define DEVINDEX_HASHBITS 8
  55 #define DEVINDEX_HASHSIZE (1U << DEVINDEX_HASHBITS)
  56 static struct hlist_head fib_info_devhash[DEVINDEX_HASHSIZE];
  57
  58 #ifdef CONFIG_IP_ROUTE_MULTIPATH
  59
  60 static DEFINE_SPINLOCK(fib_multipath_lock);
  61
  62 #define for_nexthops(fi) {                                              \
  63         int nhsel; const struct fib_nh *nh;                             \
  64         for (nhsel = 0, nh = (fi)->fib_nh;                              \
  65              nhsel < (fi)->fib_nhs;                                     \
  66              nh++, nhsel++)
  67
  68 #define change_nexthops(fi) {                                           \
  69         int nhsel; struct fib_nh *nexthop_nh;                           \
  70         for (nhsel = 0, nexthop_nh = (struct fib_nh *)((fi)->fib_nh);   \
  71              nhsel < (fi)->fib_nhs;                                     \
  72              nexthop_nh++, nhsel++)
  73
  74 #else /* CONFIG_IP_ROUTE_MULTIPATH */
  75
  76 /* Hope, that gcc will optimize it to get rid of dummy loop */
  77
  78 #define for_nexthops(fi) {                                              \
  79         int nhsel; const struct fib_nh *nh = (fi)->fib_nh;              \
  80         for (nhsel = 0; nhsel < 1; nhsel++)
  81
  82 #define change_nexthops(fi) {                                           \
  83         int nhsel;                                                      \
  84         struct fib_nh *nexthop_nh = (struct fib_nh *)((fi)->fib_nh);    \
  85         for (nhsel = 0; nhsel < 1; nhsel++)
  86
  87 #endif /* CONFIG_IP_ROUTE_MULTIPATH */
  88
  89 #define endfor_nexthops(fi) }
  90
  91
  92 const struct fib_prop fib_props[RTN_MAX + 1] = {
  93         [RTN_UNSPEC] = {
  94                 .error  = 0,
  95                 .scope  = RT_SCOPE_NOWHERE,
  96         },
  97         [RTN_UNICAST] = {
  98                 .error  = 0,
  99                 .scope  = RT_SCOPE_UNIVERSE,
 100         },
 101         [RTN_LOCAL] = {
 102                 .error  = 0,
 103                 .scope  = RT_SCOPE_HOST,
 104         },
 105         [RTN_BROADCAST] = {
 106                 .error  = 0,
 107                 .scope  = RT_SCOPE_LINK,
 108         },
 109         [RTN_ANYCAST] = {
 110                 .error  = 0,
 111                 .scope  = RT_SCOPE_LINK,
 112         },
 113         [RTN_MULTICAST] = {
 114                 .error  = 0,
 115                 .scope  = RT_SCOPE_UNIVERSE,
 116         },
 117         [RTN_BLACKHOLE] = {
 118                 .error  = -EINVAL,
 119                 .scope  = RT_SCOPE_UNIVERSE,
 120         },
 121         [RTN_UNREACHABLE] = {
 122                 .error  = -EHOSTUNREACH,
 123                 .scope  = RT_SCOPE_UNIVERSE,
 124         },
 125         [RTN_PROHIBIT] = {
 126                 .error  = -EACCES,
 127                 .scope  = RT_SCOPE_UNIVERSE,
 128         },
 129         [RTN_THROW] = {
 130                 .error  = -EAGAIN,
 131                 .scope  = RT_SCOPE_UNIVERSE,
 132         },
 133         [RTN_NAT] = {
 134                 .error  = -EINVAL,
 135                 .scope  = RT_SCOPE_NOWHERE,
 136         },
 137         [RTN_XRESOLVE] = {
 138                 .error  = -EINVAL,
 139                 .scope  = RT_SCOPE_NOWHERE,
 140         },
 141 };
 142
 143 static void free_nh_exceptions(struct fib_nh *nh)
 144 {
 145         struct fnhe_hash_bucket *hash = nh->nh_exceptions;
 146         int i;
 147
 148         for (i = 0; i < FNHE_HASH_SIZE; i++) {
 149                 struct fib_nh_exception *fnhe;
 150
 151                 fnhe = rcu_dereference_protected(hash[i].chain, 1);
 152                 while (fnhe) {
 153                         struct fib_nh_exception *next;
 154
 155                         next = rcu_dereference_protected(fnhe->fnhe_next, 1);
 156                         kfree(fnhe);
 157
 158                         fnhe = next;
 159                 }
 160         }
 161         kfree(hash);
 162 }
 163
 164 /* Release a nexthop info record */
 165 static void free_fib_info_rcu(struct rcu_head *head)
 166 {
 167         struct fib_info *fi = container_of(head, struct fib_info, rcu);
 168
 169         change_nexthops(fi) {
 170                 if (nexthop_nh->nh_dev)
 171                         dev_put(nexthop_nh->nh_dev);
 172                 if (nexthop_nh->nh_exceptions)
 173                         free_nh_exceptions(nexthop_nh);
 174         } endfor_nexthops(fi);
 175
 176         release_net(fi->fib_net);
 177         if (fi->fib_metrics != (u32 *) dst_default_metrics)
 178                 kfree(fi->fib_metrics);
 179         kfree(fi);
 180 }
 181
 182 void free_fib_info(struct fib_info *fi)
 183 {
 184         if (fi->fib_dead == 0) {
 185                 pr_warn("Freeing alive fib_info %p\n", fi);
 186                 return;
 187         }
 188         fib_info_cnt--;
 189 #ifdef CONFIG_IP_ROUTE_CLASSID
 190         change_nexthops(fi) {
 191                 if (nexthop_nh->nh_tclassid)
 192                         fi->fib_net->ipv4.fib_num_tclassid_users--;
 193         } endfor_nexthops(fi);
 194 #endif
 195         call_rcu(&fi->rcu, free_fib_info_rcu);
 196 }
 197
 198 void fib_release_info(struct fib_info *fi)
 199 {
 200         spin_lock_bh(&fib_info_lock);
 201         if (fi && --fi->fib_treeref == 0) {
 202                 hlist_del(&fi->fib_hash);
 203                 if (fi->fib_prefsrc)
 204                         hlist_del(&fi->fib_lhash);
 205                 change_nexthops(fi) {
 206                         if (!nexthop_nh->nh_dev)
 207                                 continue;
 208                         hlist_del(&nexthop_nh->nh_hash);
 209                 } endfor_nexthops(fi)
 210                 fi->fib_dead = 1;
 211                 fib_info_put(fi);
 212         }
 213         spin_unlock_bh(&fib_info_lock);
 214 }
 215
 216 static inline int nh_comp(const struct fib_info *fi, const struct fib_info *ofi)
 217 {
 218         const struct fib_nh *onh = ofi->fib_nh;
 219
 220         for_nexthops(fi) {
 221                 if (nh->nh_oif != onh->nh_oif ||
 222                     nh->nh_gw  != onh->nh_gw ||
 223                     nh->nh_scope != onh->nh_scope ||
 224 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 225                     nh->nh_weight != onh->nh_weight ||
 226 #endif
 227 #ifdef CONFIG_IP_ROUTE_CLASSID
 228                     nh->nh_tclassid != onh->nh_tclassid ||
 229 #endif
 230                     ((nh->nh_flags ^ onh->nh_flags) & ~RTNH_F_DEAD))
 231                         return -1;
 232                 onh++;
 233         } endfor_nexthops(fi);
 234         return 0;
 235 }
 236
 237 static inline unsigned int fib_devindex_hashfn(unsigned int val)
 238 {
 239         unsigned int mask = DEVINDEX_HASHSIZE - 1;
 240
 241         return (val ^
 242                 (val >> DEVINDEX_HASHBITS) ^
 243                 (val >> (DEVINDEX_HASHBITS * 2))) & mask;
 244 }
 245
 246 static inline unsigned int fib_info_hashfn(const struct fib_info *fi)
 247 {
 248         unsigned int mask = (fib_info_hash_size - 1);
 249         unsigned int val = fi->fib_nhs;
 250
 251         val ^= (fi->fib_protocol << 8) | fi->fib_scope;
 252         val ^= (__force u32)fi->fib_prefsrc;
 253         val ^= fi->fib_priority;
 254         for_nexthops(fi) {
 255                 val ^= fib_devindex_hashfn(nh->nh_oif);
 256         } endfor_nexthops(fi)
 257
 258         return (val ^ (val >> 7) ^ (val >> 12)) & mask;
 259 }
 260
 261 static struct fib_info *fib_find_info(const struct fib_info *nfi)
 262 {
 263         struct hlist_head *head;
 264         struct hlist_node *node;
 265         struct fib_info *fi;
 266         unsigned int hash;
 267
 268         hash = fib_info_hashfn(nfi);
 269         head = &fib_info_hash[hash];
 270
 271         hlist_for_each_entry(fi, node, head, fib_hash) {
 272                 if (!net_eq(fi->fib_net, nfi->fib_net))
 273                         continue;
 274                 if (fi->fib_nhs != nfi->fib_nhs)
 275                         continue;
 276                 if (nfi->fib_protocol == fi->fib_protocol &&
 277                     nfi->fib_scope == fi->fib_scope &&
 278                     nfi->fib_prefsrc == fi->fib_prefsrc &&
 279                     nfi->fib_priority == fi->fib_priority &&
 280                     memcmp(nfi->fib_metrics, fi->fib_metrics,
 281                            sizeof(u32) * RTAX_MAX) == 0 &&
 282                     ((nfi->fib_flags ^ fi->fib_flags) & ~RTNH_F_DEAD) == 0 &&
 283                     (nfi->fib_nhs == 0 || nh_comp(fi, nfi) == 0))
 284                         return fi;
 285         }
 286
 287         return NULL;
 288 }
 289
 290 /* Check, that the gateway is already configured.
 291  * Used only by redirect accept routine.
 292  */
 293 int ip_fib_check_default(__be32 gw, struct net_device *dev)
 294 {
 295         struct hlist_head *head;
 296         struct hlist_node *node;
 297         struct fib_nh *nh;
 298         unsigned int hash;
 299
 300         spin_lock(&fib_info_lock);
 301
 302         hash = fib_devindex_hashfn(dev->ifindex);
 303         head = &fib_info_devhash[hash];
 304         hlist_for_each_entry(nh, node, head, nh_hash) {
 305                 if (nh->nh_dev == dev &&
 306                     nh->nh_gw == gw &&
 307                     !(nh->nh_flags & RTNH_F_DEAD)) {
 308                         spin_unlock(&fib_info_lock);
 309                         return 0;
 310                 }
 311         }
 312
 313         spin_unlock(&fib_info_lock);
 314
 315         return -1;
 316 }
 317
 318 static inline size_t fib_nlmsg_size(struct fib_info *fi)
 319 {
 320         size_t payload = NLMSG_ALIGN(sizeof(struct rtmsg))
 321                          + nla_total_size(4) /* RTA_TABLE */
 322                          + nla_total_size(4) /* RTA_DST */
 323                          + nla_total_size(4) /* RTA_PRIORITY */
 324                          + nla_total_size(4); /* RTA_PREFSRC */
 325
 326         /* space for nested metrics */
 327         payload += nla_total_size((RTAX_MAX * nla_total_size(4)));
 328
 329         if (fi->fib_nhs) {
 330                 /* Also handles the special case fib_nhs == 1 */
 331
 332                 /* each nexthop is packed in an attribute */
 333                 size_t nhsize = nla_total_size(sizeof(struct rtnexthop));
 334
 335                 /* may contain flow and gateway attribute */
 336                 nhsize += 2 * nla_total_size(4);
 337
 338                 /* all nexthops are packed in a nested attribute */
 339                 payload += nla_total_size(fi->fib_nhs * nhsize);
 340         }
 341
 342         return payload;
 343 }
 344
 345 void rtmsg_fib(int event, __be32 key, struct fib_alias *fa,
 346                int dst_len, u32 tb_id, struct nl_info *info,
 347                unsigned int nlm_flags)
 348 {
 349         struct sk_buff *skb;
 350         u32 seq = info->nlh ? info->nlh->nlmsg_seq : 0;
 351         int err = -ENOBUFS;
 352
 353         skb = nlmsg_new(fib_nlmsg_size(fa->fa_info), GFP_KERNEL);
 354         if (skb == NULL)
 355                 goto errout;
 356
 357         err = fib_dump_info(skb, info->pid, seq, event, tb_id,
 358                             fa->fa_type, key, dst_len,
 359                             fa->fa_tos, fa->fa_info, nlm_flags);
 360         if (err < 0) {
 361                 /* -EMSGSIZE implies BUG in fib_nlmsg_size() */
 362                 WARN_ON(err == -EMSGSIZE);
 363                 kfree_skb(skb);
 364                 goto errout;
 365         }
 366         rtnl_notify(skb, info->nl_net, info->pid, RTNLGRP_IPV4_ROUTE,
 367                     info->nlh, GFP_KERNEL);
 368         return;
 369 errout:
 370         if (err < 0)
 371                 rtnl_set_sk_err(info->nl_net, RTNLGRP_IPV4_ROUTE, err);
 372 }
 373
 374 /* Return the first fib alias matching TOS with
 375  * priority less than or equal to PRIO.
 376  */
 377 struct fib_alias *fib_find_alias(struct list_head *fah, u8 tos, u32 prio)
 378 {
 379         if (fah) {
 380                 struct fib_alias *fa;
 381                 list_for_each_entry(fa, fah, fa_list) {
 382                         if (fa->fa_tos > tos)
 383                                 continue;
 384                         if (fa->fa_info->fib_priority >= prio ||
 385                             fa->fa_tos < tos)
 386                                 return fa;
 387                 }
 388         }
 389         return NULL;
 390 }
 391
 392 int fib_detect_death(struct fib_info *fi, int order,
 393                      struct fib_info **last_resort, int *last_idx, int dflt)
 394 {
 395         struct neighbour *n;
 396         int state = NUD_NONE;
 397
 398         n = neigh_lookup(&arp_tbl, &fi->fib_nh[0].nh_gw, fi->fib_dev);
 399         if (n) {
 400                 state = n->nud_state;
 401                 neigh_release(n);
 402         }
 403         if (state == NUD_REACHABLE)
 404                 return 0;
 405         if ((state & NUD_VALID) && order != dflt)
 406                 return 0;
 407         if ((state & NUD_VALID) ||
 408             (*last_idx < 0 && order > dflt)) {
 409                 *last_resort = fi;
 410                 *last_idx = order;
 411         }
 412         return 1;
 413 }
 414
 415 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 416
 417 static int fib_count_nexthops(struct rtnexthop *rtnh, int remaining)
 418 {
 419         int nhs = 0;
 420
 421         while (rtnh_ok(rtnh, remaining)) {
 422                 nhs++;
 423                 rtnh = rtnh_next(rtnh, &remaining);
 424         }
 425
 426         /* leftover implies invalid nexthop configuration, discard it */
 427         return remaining > 0 ? 0 : nhs;
 428 }
 429
 430 static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 431                        int remaining, struct fib_config *cfg)
 432 {
 433         change_nexthops(fi) {
 434                 int attrlen;
 435
 436                 if (!rtnh_ok(rtnh, remaining))
 437                         return -EINVAL;
 438
 439                 nexthop_nh->nh_flags =
 440                         (cfg->fc_flags & ~0xFF) | rtnh->rtnh_flags;
 441                 nexthop_nh->nh_oif = rtnh->rtnh_ifindex;
 442                 nexthop_nh->nh_weight = rtnh->rtnh_hops + 1;
 443
 444                 attrlen = rtnh_attrlen(rtnh);
 445                 if (attrlen > 0) {
 446                         struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
 447
 448                         nla = nla_find(attrs, attrlen, RTA_GATEWAY);
 449                         nexthop_nh->nh_gw = nla ? nla_get_be32(nla) : 0;
 450 #ifdef CONFIG_IP_ROUTE_CLASSID
 451                         nla = nla_find(attrs, attrlen, RTA_FLOW);
 452                         nexthop_nh->nh_tclassid = nla ? nla_get_u32(nla) : 0;
 453                         if (nexthop_nh->nh_tclassid)
 454                                 fi->fib_net->ipv4.fib_num_tclassid_users++;
 455 #endif
 456                 }
 457
 458                 rtnh = rtnh_next(rtnh, &remaining);
 459         } endfor_nexthops(fi);
 460
 461         return 0;
 462 }
 463
 464 #endif
 465
 466 int fib_nh_match(struct fib_config *cfg, struct fib_info *fi)
 467 {
 468 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 469         struct rtnexthop *rtnh;
 470         int remaining;
 471 #endif
 472
 473         if (cfg->fc_priority && cfg->fc_priority != fi->fib_priority)
 474                 return 1;
 475
 476         if (cfg->fc_oif || cfg->fc_gw) {
 477                 if ((!cfg->fc_oif || cfg->fc_oif == fi->fib_nh->nh_oif) &&
 478                     (!cfg->fc_gw  || cfg->fc_gw == fi->fib_nh->nh_gw))
 479                         return 0;
 480                 return 1;
 481         }
 482
 483 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 484         if (cfg->fc_mp == NULL)
 485                 return 0;
 486
 487         rtnh = cfg->fc_mp;
 488         remaining = cfg->fc_mp_len;
 489
 490         for_nexthops(fi) {
 491                 int attrlen;
 492
 493                 if (!rtnh_ok(rtnh, remaining))
 494                         return -EINVAL;
 495
 496                 if (rtnh->rtnh_ifindex && rtnh->rtnh_ifindex != nh->nh_oif)
 497                         return 1;
 498
 499                 attrlen = rtnh_attrlen(rtnh);
 500                 if (attrlen < 0) {
 501                         struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
 502
 503                         nla = nla_find(attrs, attrlen, RTA_GATEWAY);
 504                         if (nla && nla_get_be32(nla) != nh->nh_gw)
 505                                 return 1;
 506 #ifdef CONFIG_IP_ROUTE_CLASSID
 507                         nla = nla_find(attrs, attrlen, RTA_FLOW);
 508                         if (nla && nla_get_u32(nla) != nh->nh_tclassid)
 509                                 return 1;
 510 #endif
 511                 }
 512
 513                 rtnh = rtnh_next(rtnh, &remaining);
 514         } endfor_nexthops(fi);
 515 #endif
 516         return 0;
 517 }
 518
 519
 520 /*
 521  * Picture
 522  * -------
 523  *
 524  * Semantics of nexthop is very messy by historical reasons.
 525  * We have to take into account, that:
 526  * a) gateway can be actually local interface address,
 527  *    so that gatewayed route is direct.
 528  * b) gateway must be on-link address, possibly
 529  *    described not by an ifaddr, but also by a direct route.
 530  * c) If both gateway and interface are specified, they should not
 531  *    contradict.
 532  * d) If we use tunnel routes, gateway could be not on-link.
 533  *
 534  * Attempt to reconcile all of these (alas, self-contradictory) conditions
 535  * results in pretty ugly and hairy code with obscure logic.
 536  *
 537  * I chose to generalized it instead, so that the size
 538  * of code does not increase practically, but it becomes
 539  * much more general.
 540  * Every prefix is assigned a "scope" value: "host" is local address,
 541  * "link" is direct route,
 542  * [ ... "site" ... "interior" ... ]
 543  * and "universe" is true gateway route with global meaning.
 544  *
 545  * Every prefix refers to a set of "nexthop"s (gw, oif),
 546  * where gw must have narrower scope. This recursion stops
 547  * when gw has LOCAL scope or if "nexthop" is declared ONLINK,
 548  * which means that gw is forced to be on link.
 549  *
 550  * Code is still hairy, but now it is apparently logically
 551  * consistent and very flexible. F.e. as by-product it allows
 552  * to co-exists in peace independent exterior and interior
 553  * routing processes.
 554  *
 555  * Normally it looks as following.
 556  *
 557  * {universe prefix}  -> (gw, oif) [scope link]
 558  *                |
 559  *                |-> {link prefix} -> (gw, oif) [scope local]
 560  *                                      |
 561  *                                      |-> {local prefix} (terminal node)
 562  */
 563 static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
 564                         struct fib_nh *nh)
 565 {
 566         int err;
 567         struct net *net;
 568         struct net_device *dev;
 569
 570         net = cfg->fc_nlinfo.nl_net;
 571         if (nh->nh_gw) {
 572                 struct fib_result res;
 573
 574                 if (nh->nh_flags & RTNH_F_ONLINK) {
 575
 576                         if (cfg->fc_scope >= RT_SCOPE_LINK)
 577                                 return -EINVAL;
 578                         if (inet_addr_type(net, nh->nh_gw) != RTN_UNICAST)
 579                                 return -EINVAL;
 580                         dev = __dev_get_by_index(net, nh->nh_oif);
 581                         if (!dev)
 582                                 return -ENODEV;
 583                         if (!(dev->flags & IFF_UP))
 584                                 return -ENETDOWN;
 585                         nh->nh_dev = dev;
 586                         dev_hold(dev);
 587                         nh->nh_scope = RT_SCOPE_LINK;
 588                         return 0;
 589                 }
 590                 rcu_read_lock();
 591                 {
 592                         struct flowi4 fl4 = {
 593                                 .daddr = nh->nh_gw,
 594                                 .flowi4_scope = cfg->fc_scope + 1,
 595                                 .flowi4_oif = nh->nh_oif,
 596                         };
 597
 598                         /* It is not necessary, but requires a bit of thinking */
 599                         if (fl4.flowi4_scope < RT_SCOPE_LINK)
 600                                 fl4.flowi4_scope = RT_SCOPE_LINK;
 601                         err = fib_lookup(net, &fl4, &res);
 602                         if (err) {
 603                                 rcu_read_unlock();
 604                                 return err;
 605                         }
 606                 }
 607                 err = -EINVAL;
 608                 if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
 609                         goto out;
 610                 nh->nh_scope = res.scope;
 611                 nh->nh_oif = FIB_RES_OIF(res);
 612                 nh->nh_dev = dev = FIB_RES_DEV(res);
 613                 if (!dev)
 614                         goto out;
 615                 dev_hold(dev);
 616                 err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
 617         } else {
 618                 struct in_device *in_dev;
 619
 620                 if (nh->nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK))
 621                         return -EINVAL;
 622
 623                 rcu_read_lock();
 624                 err = -ENODEV;
 625                 in_dev = inetdev_by_index(net, nh->nh_oif);
 626                 if (in_dev == NULL)
 627                         goto out;
 628                 err = -ENETDOWN;
 629                 if (!(in_dev->dev->flags & IFF_UP))
 630                         goto out;
 631                 nh->nh_dev = in_dev->dev;
 632                 dev_hold(nh->nh_dev);
 633                 nh->nh_scope = RT_SCOPE_HOST;
 634                 err = 0;
 635         }
 636 out:
 637         rcu_read_unlock();
 638         return err;
 639 }
 640
 641 static inline unsigned int fib_laddr_hashfn(__be32 val)
 642 {
 643         unsigned int mask = (fib_info_hash_size - 1);
 644
 645         return ((__force u32)val ^
 646                 ((__force u32)val >> 7) ^
 647                 ((__force u32)val >> 14)) & mask;
 648 }
 649
 650 static struct hlist_head *fib_info_hash_alloc(int bytes)
 651 {
 652         if (bytes <= PAGE_SIZE)
 653                 return kzalloc(bytes, GFP_KERNEL);
 654         else
 655                 return (struct hlist_head *)
 656                         __get_free_pages(GFP_KERNEL | __GFP_ZERO,
 657                                          get_order(bytes));
 658 }
 659
 660 static void fib_info_hash_free(struct hlist_head *hash, int bytes)
 661 {
 662         if (!hash)
 663                 return;
 664
 665         if (bytes <= PAGE_SIZE)
 666                 kfree(hash);
 667         else
 668                 free_pages((unsigned long) hash, get_order(bytes));
 669 }
 670
 671 static void fib_info_hash_move(struct hlist_head *new_info_hash,
 672                                struct hlist_head *new_laddrhash,
 673                                unsigned int new_size)
 674 {
 675         struct hlist_head *old_info_hash, *old_laddrhash;
 676         unsigned int old_size = fib_info_hash_size;
 677         unsigned int i, bytes;
 678
 679         spin_lock_bh(&fib_info_lock);
 680         old_info_hash = fib_info_hash;
 681         old_laddrhash = fib_info_laddrhash;
 682         fib_info_hash_size = new_size;
 683
 684         for (i = 0; i < old_size; i++) {
 685                 struct hlist_head *head = &fib_info_hash[i];
 686                 struct hlist_node *node, *n;
 687                 struct fib_info *fi;
 688
 689                 hlist_for_each_entry_safe(fi, node, n, head, fib_hash) {
 690                         struct hlist_head *dest;
 691                         unsigned int new_hash;
 692
 693                         hlist_del(&fi->fib_hash);
 694
 695                         new_hash = fib_info_hashfn(fi);
 696                         dest = &new_info_hash[new_hash];
 697                         hlist_add_head(&fi->fib_hash, dest);
 698                 }
 699         }
 700         fib_info_hash = new_info_hash;
 701
 702         for (i = 0; i < old_size; i++) {
 703                 struct hlist_head *lhead = &fib_info_laddrhash[i];
 704                 struct hlist_node *node, *n;
 705                 struct fib_info *fi;
 706
 707                 hlist_for_each_entry_safe(fi, node, n, lhead, fib_lhash) {
 708                         struct hlist_head *ldest;
 709                         unsigned int new_hash;
 710
 711                         hlist_del(&fi->fib_lhash);
 712
 713                         new_hash = fib_laddr_hashfn(fi->fib_prefsrc);
 714                         ldest = &new_laddrhash[new_hash];
 715                         hlist_add_head(&fi->fib_lhash, ldest);
 716                 }
 717         }
 718         fib_info_laddrhash = new_laddrhash;
 719
 720         spin_unlock_bh(&fib_info_lock);
 721
 722         bytes = old_size * sizeof(struct hlist_head *);
 723         fib_info_hash_free(old_info_hash, bytes);
 724         fib_info_hash_free(old_laddrhash, bytes);
 725 }
 726
 727 __be32 fib_info_update_nh_saddr(struct net *net, struct fib_nh *nh)
 728 {
 729         nh->nh_saddr = inet_select_addr(nh->nh_dev,
 730                                         nh->nh_gw,
 731                                         nh->nh_parent->fib_scope);
 732         nh->nh_saddr_genid = atomic_read(&net->ipv4.dev_addr_genid);
 733
 734         return nh->nh_saddr;
 735 }
 736
 737 struct fib_info *fib_create_info(struct fib_config *cfg)
 738 {
 739         int err;
 740         struct fib_info *fi = NULL;
 741         struct fib_info *ofi;
 742         int nhs = 1;
 743         struct net *net = cfg->fc_nlinfo.nl_net;
 744
 745         if (cfg->fc_type > RTN_MAX)
 746                 goto err_inval;
 747
 748         /* Fast check to catch the most weird cases */
 749         if (fib_props[cfg->fc_type].scope > cfg->fc_scope)
 750                 goto err_inval;
 751
 752 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 753         if (cfg->fc_mp) {
 754                 nhs = fib_count_nexthops(cfg->fc_mp, cfg->fc_mp_len);
 755                 if (nhs == 0)
 756                         goto err_inval;
 757         }
 758 #endif
 759
 760         err = -ENOBUFS;
 761         if (fib_info_cnt >= fib_info_hash_size) {
 762                 unsigned int new_size = fib_info_hash_size << 1;
 763                 struct hlist_head *new_info_hash;
 764                 struct hlist_head *new_laddrhash;
 765                 unsigned int bytes;
 766
 767                 if (!new_size)
 768                         new_size = 1;
 769                 bytes = new_size * sizeof(struct hlist_head *);
 770                 new_info_hash = fib_info_hash_alloc(bytes);
 771                 new_laddrhash = fib_info_hash_alloc(bytes);
 772                 if (!new_info_hash || !new_laddrhash) {
 773                         fib_info_hash_free(new_info_hash, bytes);
 774                         fib_info_hash_free(new_laddrhash, bytes);
 775                 } else
 776                         fib_info_hash_move(new_info_hash, new_laddrhash, new_size);
 777
 778                 if (!fib_info_hash_size)
 779                         goto failure;
 780         }
 781
 782         fi = kzalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL);
 783         if (fi == NULL)
 784                 goto failure;
 785         if (cfg->fc_mx) {
 786                 fi->fib_metrics = kzalloc(sizeof(u32) * RTAX_MAX, GFP_KERNEL);
 787                 if (!fi->fib_metrics)
 788                         goto failure;
 789         } else
 790                 fi->fib_metrics = (u32 *) dst_default_metrics;
 791         fib_info_cnt++;
 792
 793         fi->fib_net = hold_net(net);
 794         fi->fib_protocol = cfg->fc_protocol;
 795         fi->fib_scope = cfg->fc_scope;
 796         fi->fib_flags = cfg->fc_flags;
 797         fi->fib_priority = cfg->fc_priority;
 798         fi->fib_prefsrc = cfg->fc_prefsrc;
 799
 800         fi->fib_nhs = nhs;
 801         change_nexthops(fi) {
 802                 nexthop_nh->nh_parent = fi;
 803         } endfor_nexthops(fi)
 804
 805         if (cfg->fc_mx) {
 806                 struct nlattr *nla;
 807                 int remaining;
 808
 809                 nla_for_each_attr(nla, cfg->fc_mx, cfg->fc_mx_len, remaining) {
 810                         int type = nla_type(nla);
 811
 812                         if (type) {
 813                                 u32 val;
 814
 815                                 if (type > RTAX_MAX)
 816                                         goto err_inval;
 817                                 val = nla_get_u32(nla);
 818                                 if (type == RTAX_ADVMSS && val > 65535 - 40)
 819                                         val = 65535 - 40;
 820                                 if (type == RTAX_MTU && val > 65535 - 15)
 821                                         val = 65535 - 15;
 822                                 fi->fib_metrics[type - 1] = val;
 823                         }
 824                 }
 825         }
 826
 827         if (cfg->fc_mp) {
 828 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 829                 err = fib_get_nhs(fi, cfg->fc_mp, cfg->fc_mp_len, cfg);
 830                 if (err != 0)
 831                         goto failure;
 832                 if (cfg->fc_oif && fi->fib_nh->nh_oif != cfg->fc_oif)
 833                         goto err_inval;
 834                 if (cfg->fc_gw && fi->fib_nh->nh_gw != cfg->fc_gw)
 835                         goto err_inval;
 836 #ifdef CONFIG_IP_ROUTE_CLASSID
 837                 if (cfg->fc_flow && fi->fib_nh->nh_tclassid != cfg->fc_flow)
 838                         goto err_inval;
 839 #endif
 840 #else
 841                 goto err_inval;
 842 #endif
 843         } else {
 844                 struct fib_nh *nh = fi->fib_nh;
 845
 846                 nh->nh_oif = cfg->fc_oif;
 847                 nh->nh_gw = cfg->fc_gw;
 848                 nh->nh_flags = cfg->fc_flags;
 849 #ifdef CONFIG_IP_ROUTE_CLASSID
 850                 nh->nh_tclassid = cfg->fc_flow;
 851                 if (nh->nh_tclassid)
 852                         fi->fib_net->ipv4.fib_num_tclassid_users++;
 853 #endif
 854 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 855                 nh->nh_weight = 1;
 856 #endif
 857         }
 858
 859         if (fib_props[cfg->fc_type].error) {
 860                 if (cfg->fc_gw || cfg->fc_oif || cfg->fc_mp)
 861                         goto err_inval;
 862                 goto link_it;
 863         } else {
 864                 switch (cfg->fc_type) {
 865                 case RTN_UNICAST:
 866                 case RTN_LOCAL:
 867                 case RTN_BROADCAST:
 868                 case RTN_ANYCAST:
 869                 case RTN_MULTICAST:
 870                         break;
 871                 default:
 872                         goto err_inval;
 873                 }
 874         }
 875
 876         if (cfg->fc_scope > RT_SCOPE_HOST)
 877                 goto err_inval;
 878
 879         if (cfg->fc_scope == RT_SCOPE_HOST) {
 880                 struct fib_nh *nh = fi->fib_nh;
 881
 882                 /* Local address is added. */
 883                 if (nhs != 1 || nh->nh_gw)
 884                         goto err_inval;
 885                 nh->nh_scope = RT_SCOPE_NOWHERE;
 886                 nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
 887                 err = -ENODEV;
 888                 if (nh->nh_dev == NULL)
 889                         goto failure;
 890         } else {
 891                 change_nexthops(fi) {
 892                         err = fib_check_nh(cfg, fi, nexthop_nh);
 893                         if (err != 0)
 894                                 goto failure;
 895                 } endfor_nexthops(fi)
 896         }
 897
 898         if (fi->fib_prefsrc) {
 899                 if (cfg->fc_type != RTN_LOCAL || !cfg->fc_dst ||
 900                     fi->fib_prefsrc != cfg->fc_dst)
 901                         if (inet_addr_type(net, fi->fib_prefsrc) != RTN_LOCAL)
 902                                 goto err_inval;
 903         }
 904
 905         change_nexthops(fi) {
 906                 fib_info_update_nh_saddr(net, nexthop_nh);
 907         } endfor_nexthops(fi)
 908
 909 link_it:
 910         ofi = fib_find_info(fi);
 911         if (ofi) {
 912                 fi->fib_dead = 1;
 913                 free_fib_info(fi);
 914                 ofi->fib_treeref++;
 915                 return ofi;
 916         }
 917
 918         fi->fib_treeref++;
 919         atomic_inc(&fi->fib_clntref);
 920         spin_lock_bh(&fib_info_lock);
 921         hlist_add_head(&fi->fib_hash,
 922                        &fib_info_hash[fib_info_hashfn(fi)]);
 923         if (fi->fib_prefsrc) {
 924                 struct hlist_head *head;
 925
 926                 head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)];
 927                 hlist_add_head(&fi->fib_lhash, head);
 928         }
 929         change_nexthops(fi) {
 930                 struct hlist_head *head;
 931                 unsigned int hash;
 932
 933                 if (!nexthop_nh->nh_dev)
 934                         continue;
 935                 hash = fib_devindex_hashfn(nexthop_nh->nh_dev->ifindex);
 936                 head = &fib_info_devhash[hash];
 937                 hlist_add_head(&nexthop_nh->nh_hash, head);
 938         } endfor_nexthops(fi)
 939         spin_unlock_bh(&fib_info_lock);
 940         return fi;
 941
 942 err_inval:
 943         err = -EINVAL;
 944
 945 failure:
 946         if (fi) {
 947                 fi->fib_dead = 1;
 948                 free_fib_info(fi);
 949         }
 950
 951         return ERR_PTR(err);
 952 }
 953
 954 int fib_dump_info(struct sk_buff *skb, u32 pid, u32 seq, int event,
 955                   u32 tb_id, u8 type, __be32 dst, int dst_len, u8 tos,
 956                   struct fib_info *fi, unsigned int flags)
 957 {
 958         struct nlmsghdr *nlh;
 959         struct rtmsg *rtm;
 960
 961         nlh = nlmsg_put(skb, pid, seq, event, sizeof(*rtm), flags);
 962         if (nlh == NULL)
 963                 return -EMSGSIZE;
 964
 965         rtm = nlmsg_data(nlh);
 966         rtm->rtm_family = AF_INET;
 967         rtm->rtm_dst_len = dst_len;
 968         rtm->rtm_src_len = 0;
 969         rtm->rtm_tos = tos;
 970         if (tb_id < 256)
 971                 rtm->rtm_table = tb_id;
 972         else
 973                 rtm->rtm_table = RT_TABLE_COMPAT;
 974         if (nla_put_u32(skb, RTA_TABLE, tb_id))
 975                 goto nla_put_failure;
 976         rtm->rtm_type = type;
 977         rtm->rtm_flags = fi->fib_flags;
 978         rtm->rtm_scope = fi->fib_scope;
 979         rtm->rtm_protocol = fi->fib_protocol;
 980
 981         if (rtm->rtm_dst_len &&
 982             nla_put_be32(skb, RTA_DST, dst))
 983                 goto nla_put_failure;
 984         if (fi->fib_priority &&
 985             nla_put_u32(skb, RTA_PRIORITY, fi->fib_priority))
 986                 goto nla_put_failure;
 987         if (rtnetlink_put_metrics(skb, fi->fib_metrics) < 0)
 988                 goto nla_put_failure;
 989
 990         if (fi->fib_prefsrc &&
 991             nla_put_be32(skb, RTA_PREFSRC, fi->fib_prefsrc))
 992                 goto nla_put_failure;
 993         if (fi->fib_nhs == 1) {
 994                 if (fi->fib_nh->nh_gw &&
 995                     nla_put_be32(skb, RTA_GATEWAY, fi->fib_nh->nh_gw))
 996                         goto nla_put_failure;
 997                 if (fi->fib_nh->nh_oif &&
 998                     nla_put_u32(skb, RTA_OIF, fi->fib_nh->nh_oif))
 999                         goto nla_put_failure;
1000 #ifdef CONFIG_IP_ROUTE_CLASSID
1001                 if (fi->fib_nh[0].nh_tclassid &&
1002                     nla_put_u32(skb, RTA_FLOW, fi->fib_nh[0].nh_tclassid))
1003                         goto nla_put_failure;
1004 #endif
1005         }
1006 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1007         if (fi->fib_nhs > 1) {
1008                 struct rtnexthop *rtnh;
1009                 struct nlattr *mp;
1010
1011                 mp = nla_nest_start(skb, RTA_MULTIPATH);
1012                 if (mp == NULL)
1013                         goto nla_put_failure;
1014
1015                 for_nexthops(fi) {
1016                         rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));
1017                         if (rtnh == NULL)
1018                                 goto nla_put_failure;
1019
1020                         rtnh->rtnh_flags = nh->nh_flags & 0xFF;
1021                         rtnh->rtnh_hops = nh->nh_weight - 1;
1022                         rtnh->rtnh_ifindex = nh->nh_oif;
1023
1024                         if (nh->nh_gw &&
1025                             nla_put_be32(skb, RTA_GATEWAY, nh->nh_gw))
1026                                 goto nla_put_failure;
1027 #ifdef CONFIG_IP_ROUTE_CLASSID
1028                         if (nh->nh_tclassid &&
1029                             nla_put_u32(skb, RTA_FLOW, nh->nh_tclassid))
1030                                 goto nla_put_failure;
1031 #endif
1032                         /* length of rtnetlink header + attributes */
1033                         rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *) rtnh;
1034                 } endfor_nexthops(fi);
1035
1036                 nla_nest_end(skb, mp);
1037         }
1038 #endif
1039         return nlmsg_end(skb, nlh);
1040
1041 nla_put_failure:
1042         nlmsg_cancel(skb, nlh);
1043         return -EMSGSIZE;
1044 }
1045
1046 /*
1047  * Update FIB if:
1048  * - local address disappeared -> we must delete all the entries
1049  *   referring to it.
1050  * - device went down -> we must shutdown all nexthops going via it.
1051  */
1052 int fib_sync_down_addr(struct net *net, __be32 local)
1053 {
1054         int ret = 0;
1055         unsigned int hash = fib_laddr_hashfn(local);
1056         struct hlist_head *head = &fib_info_laddrhash[hash];
1057         struct hlist_node *node;
1058         struct fib_info *fi;
1059
1060         if (fib_info_laddrhash == NULL || local == 0)
1061                 return 0;
1062
1063         hlist_for_each_entry(fi, node, head, fib_lhash) {
1064                 if (!net_eq(fi->fib_net, net))
1065                         continue;
1066                 if (fi->fib_prefsrc == local) {
1067                         fi->fib_flags |= RTNH_F_DEAD;
1068                         ret++;
1069                 }
1070         }
1071         return ret;
1072 }
1073
1074 int fib_sync_down_dev(struct net_device *dev, int force)
1075 {
1076         int ret = 0;
1077         int scope = RT_SCOPE_NOWHERE;
1078         struct fib_info *prev_fi = NULL;
1079         unsigned int hash = fib_devindex_hashfn(dev->ifindex);
1080         struct hlist_head *head = &fib_info_devhash[hash];
1081         struct hlist_node *node;
1082         struct fib_nh *nh;
1083
1084         if (force)
1085                 scope = -1;
1086
1087         hlist_for_each_entry(nh, node, head, nh_hash) {
1088                 struct fib_info *fi = nh->nh_parent;
1089                 int dead;
1090
1091                 BUG_ON(!fi->fib_nhs);
1092                 if (nh->nh_dev != dev || fi == prev_fi)
1093                         continue;
1094                 prev_fi = fi;
1095                 dead = 0;
1096                 change_nexthops(fi) {
1097                         if (nexthop_nh->nh_flags & RTNH_F_DEAD)
1098                                 dead++;
1099                         else if (nexthop_nh->nh_dev == dev &&
1100                                  nexthop_nh->nh_scope != scope) {
1101                                 nexthop_nh->nh_flags |= RTNH_F_DEAD;
1102 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1103                                 spin_lock_bh(&fib_multipath_lock);
1104                                 fi->fib_power -= nexthop_nh->nh_power;
1105                                 nexthop_nh->nh_power = 0;
1106                                 spin_unlock_bh(&fib_multipath_lock);
1107 #endif
1108                                 dead++;
1109                         }
1110 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1111                         if (force > 1 && nexthop_nh->nh_dev == dev) {
1112                                 dead = fi->fib_nhs;
1113                                 break;
1114                         }
1115 #endif
1116                 } endfor_nexthops(fi)
1117                 if (dead == fi->fib_nhs) {
1118                         fi->fib_flags |= RTNH_F_DEAD;
1119                         ret++;
1120                 }
1121         }
1122
1123         return ret;
1124 }
1125
1126 /* Must be invoked inside of an RCU protected region.  */
1127 void fib_select_default(struct fib_result *res)
1128 {
1129         struct fib_info *fi = NULL, *last_resort = NULL;
1130         struct list_head *fa_head = res->fa_head;
1131         struct fib_table *tb = res->table;
1132         int order = -1, last_idx = -1;
1133         struct fib_alias *fa;
1134
1135         list_for_each_entry_rcu(fa, fa_head, fa_list) {
1136                 struct fib_info *next_fi = fa->fa_info;
1137
1138                 if (next_fi->fib_scope != res->scope ||
1139                     fa->fa_type != RTN_UNICAST)
1140                         continue;
1141
1142                 if (next_fi->fib_priority > res->fi->fib_priority)
1143                         break;
1144                 if (!next_fi->fib_nh[0].nh_gw ||
1145                     next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
1146                         continue;
1147
1148                 fib_alias_accessed(fa);
1149
1150                 if (fi == NULL) {
1151                         if (next_fi != res->fi)
1152                                 break;
1153                 } else if (!fib_detect_death(fi, order, &last_resort,
1154                                              &last_idx, tb->tb_default)) {
1155                         fib_result_assign(res, fi);
1156                         tb->tb_default = order;
1157                         goto out;
1158                 }
1159                 fi = next_fi;
1160                 order++;
1161         }
1162
1163         if (order <= 0 || fi == NULL) {
1164                 tb->tb_default = -1;
1165                 goto out;
1166         }
1167
1168         if (!fib_detect_death(fi, order, &last_resort, &last_idx,
1169                                 tb->tb_default)) {
1170                 fib_result_assign(res, fi);
1171                 tb->tb_default = order;
1172                 goto out;
1173         }
1174
1175         if (last_idx >= 0)
1176                 fib_result_assign(res, last_resort);
1177         tb->tb_default = last_idx;
1178 out:
1179         return;
1180 }
1181
1182 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1183
1184 /*
1185  * Dead device goes up. We wake up dead nexthops.
1186  * It takes sense only on multipath routes.
1187  */
1188 int fib_sync_up(struct net_device *dev)
1189 {
1190         struct fib_info *prev_fi;
1191         unsigned int hash;
1192         struct hlist_head *head;
1193         struct hlist_node *node;
1194         struct fib_nh *nh;
1195         int ret;
1196
1197         if (!(dev->flags & IFF_UP))
1198                 return 0;
1199
1200         prev_fi = NULL;
1201         hash = fib_devindex_hashfn(dev->ifindex);
1202         head = &fib_info_devhash[hash];
1203         ret = 0;
1204
1205         hlist_for_each_entry(nh, node, head, nh_hash) {
1206                 struct fib_info *fi = nh->nh_parent;
1207                 int alive;
1208
1209                 BUG_ON(!fi->fib_nhs);
1210                 if (nh->nh_dev != dev || fi == prev_fi)
1211                         continue;
1212
1213                 prev_fi = fi;
1214                 alive = 0;
1215                 change_nexthops(fi) {
1216                         if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1217                                 alive++;
1218                                 continue;
1219                         }
1220                         if (nexthop_nh->nh_dev == NULL ||
1221                             !(nexthop_nh->nh_dev->flags & IFF_UP))
1222                                 continue;
1223                         if (nexthop_nh->nh_dev != dev ||
1224                             !__in_dev_get_rtnl(dev))
1225                                 continue;
1226                         alive++;
1227                         spin_lock_bh(&fib_multipath_lock);
1228                         nexthop_nh->nh_power = 0;
1229                         nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
1230                         spin_unlock_bh(&fib_multipath_lock);
1231                 } endfor_nexthops(fi)
1232
1233                 if (alive > 0) {
1234                         fi->fib_flags &= ~RTNH_F_DEAD;
1235                         ret++;
1236                 }
1237         }
1238
1239         return ret;
1240 }
1241
1242 /*
1243  * The algorithm is suboptimal, but it provides really
1244  * fair weighted route distribution.
1245  */
1246 void fib_select_multipath(struct fib_result *res)
1247 {
1248         struct fib_info *fi = res->fi;
1249         int w;
1250
1251         spin_lock_bh(&fib_multipath_lock);
1252         if (fi->fib_power <= 0) {
1253                 int power = 0;
1254                 change_nexthops(fi) {
1255                         if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1256                                 power += nexthop_nh->nh_weight;
1257                                 nexthop_nh->nh_power = nexthop_nh->nh_weight;
1258                         }
1259                 } endfor_nexthops(fi);
1260                 fi->fib_power = power;
1261                 if (power <= 0) {
1262                         spin_unlock_bh(&fib_multipath_lock);
1263                         /* Race condition: route has just become dead. */
1264                         res->nh_sel = 0;
1265                         return;
1266                 }
1267         }
1268
1269
1270         /* w should be random number [0..fi->fib_power-1],
1271          * it is pretty bad approximation.
1272          */
1273
1274         w = jiffies % fi->fib_power;
1275
1276         change_nexthops(fi) {
1277                 if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
1278                     nexthop_nh->nh_power) {
1279                         w -= nexthop_nh->nh_power;
1280                         if (w <= 0) {
1281                                 nexthop_nh->nh_power--;
1282                                 fi->fib_power--;
1283                                 res->nh_sel = nhsel;
1284                                 spin_unlock_bh(&fib_multipath_lock);
1285                                 return;
1286                         }
1287                 }
1288         } endfor_nexthops(fi);
1289
1290         /* Race condition: route has just become dead. */
1291         res->nh_sel = 0;
1292         spin_unlock_bh(&fib_multipath_lock);
1293 }
1294 #endif