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 rt_fibinfo_free(struct rtable __rcu **rtp)
 144 {
 145         struct rtable *rt = rcu_dereference_protected(*rtp, 1);
 146
 147         if (!rt)
 148                 return;
 149
 150         /* Not even needed : RCU_INIT_POINTER(*rtp, NULL);
 151          * because we waited an RCU grace period before calling
 152          * free_fib_info_rcu()
 153          */
 154
 155         dst_free(&rt->dst);
 156 }
 157
 158 static void free_nh_exceptions(struct fib_nh *nh)
 159 {
 160         struct fnhe_hash_bucket *hash;
 161         int i;
 162
 163         hash = rcu_dereference_protected(nh->nh_exceptions, 1);
 164         if (!hash)
 165                 return;
 166         for (i = 0; i < FNHE_HASH_SIZE; i++) {
 167                 struct fib_nh_exception *fnhe;
 168
 169                 fnhe = rcu_dereference_protected(hash[i].chain, 1);
 170                 while (fnhe) {
 171                         struct fib_nh_exception *next;
 172
 173                         next = rcu_dereference_protected(fnhe->fnhe_next, 1);
 174
 175                         rt_fibinfo_free(&fnhe->fnhe_rth_input);
 176                         rt_fibinfo_free(&fnhe->fnhe_rth_output);
 177
 178                         kfree(fnhe);
 179
 180                         fnhe = next;
 181                 }
 182         }
 183         kfree(hash);
 184 }
 185
 186 static void rt_fibinfo_free_cpus(struct rtable __rcu * __percpu *rtp)
 187 {
 188         int cpu;
 189
 190         if (!rtp)
 191                 return;
 192
 193         for_each_possible_cpu(cpu) {
 194                 struct rtable *rt;
 195
 196                 rt = rcu_dereference_protected(*per_cpu_ptr(rtp, cpu), 1);
 197                 if (rt)
 198                         dst_free(&rt->dst);
 199         }
 200         free_percpu(rtp);
 201 }
 202
 203 /* Release a nexthop info record */
 204 static void free_fib_info_rcu(struct rcu_head *head)
 205 {
 206         struct fib_info *fi = container_of(head, struct fib_info, rcu);
 207
 208         change_nexthops(fi) {
 209                 if (nexthop_nh->nh_dev)
 210                         dev_put(nexthop_nh->nh_dev);
 211                 free_nh_exceptions(nexthop_nh);
 212                 rt_fibinfo_free_cpus(nexthop_nh->nh_pcpu_rth_output);
 213                 rt_fibinfo_free(&nexthop_nh->nh_rth_input);
 214         } endfor_nexthops(fi);
 215
 216         release_net(fi->fib_net);
 217         if (fi->fib_metrics != (u32 *) dst_default_metrics)
 218                 kfree(fi->fib_metrics);
 219         kfree(fi);
 220 }
 221
 222 void free_fib_info(struct fib_info *fi)
 223 {
 224         if (fi->fib_dead == 0) {
 225                 pr_warn("Freeing alive fib_info %p\n", fi);
 226                 return;
 227         }
 228         fib_info_cnt--;
 229 #ifdef CONFIG_IP_ROUTE_CLASSID
 230         change_nexthops(fi) {
 231                 if (nexthop_nh->nh_tclassid)
 232                         fi->fib_net->ipv4.fib_num_tclassid_users--;
 233         } endfor_nexthops(fi);
 234 #endif
 235         call_rcu(&fi->rcu, free_fib_info_rcu);
 236 }
 237
 238 void fib_release_info(struct fib_info *fi)
 239 {
 240         spin_lock_bh(&fib_info_lock);
 241         if (fi && --fi->fib_treeref == 0) {
 242                 hlist_del(&fi->fib_hash);
 243                 if (fi->fib_prefsrc)
 244                         hlist_del(&fi->fib_lhash);
 245                 change_nexthops(fi) {
 246                         if (!nexthop_nh->nh_dev)
 247                                 continue;
 248                         hlist_del(&nexthop_nh->nh_hash);
 249                 } endfor_nexthops(fi)
 250                 fi->fib_dead = 1;
 251                 fib_info_put(fi);
 252         }
 253         spin_unlock_bh(&fib_info_lock);
 254 }
 255
 256 static inline int nh_comp(const struct fib_info *fi, const struct fib_info *ofi)
 257 {
 258         const struct fib_nh *onh = ofi->fib_nh;
 259
 260         for_nexthops(fi) {
 261                 if (nh->nh_oif != onh->nh_oif ||
 262                     nh->nh_gw  != onh->nh_gw ||
 263                     nh->nh_scope != onh->nh_scope ||
 264 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 265                     nh->nh_weight != onh->nh_weight ||
 266 #endif
 267 #ifdef CONFIG_IP_ROUTE_CLASSID
 268                     nh->nh_tclassid != onh->nh_tclassid ||
 269 #endif
 270                     ((nh->nh_flags ^ onh->nh_flags) & ~RTNH_F_DEAD))
 271                         return -1;
 272                 onh++;
 273         } endfor_nexthops(fi);
 274         return 0;
 275 }
 276
 277 static inline unsigned int fib_devindex_hashfn(unsigned int val)
 278 {
 279         unsigned int mask = DEVINDEX_HASHSIZE - 1;
 280
 281         return (val ^
 282                 (val >> DEVINDEX_HASHBITS) ^
 283                 (val >> (DEVINDEX_HASHBITS * 2))) & mask;
 284 }
 285
 286 static inline unsigned int fib_info_hashfn(const struct fib_info *fi)
 287 {
 288         unsigned int mask = (fib_info_hash_size - 1);
 289         unsigned int val = fi->fib_nhs;
 290
 291         val ^= (fi->fib_protocol << 8) | fi->fib_scope;
 292         val ^= (__force u32)fi->fib_prefsrc;
 293         val ^= fi->fib_priority;
 294         for_nexthops(fi) {
 295                 val ^= fib_devindex_hashfn(nh->nh_oif);
 296         } endfor_nexthops(fi)
 297
 298         return (val ^ (val >> 7) ^ (val >> 12)) & mask;
 299 }
 300
 301 static struct fib_info *fib_find_info(const struct fib_info *nfi)
 302 {
 303         struct hlist_head *head;
 304         struct fib_info *fi;
 305         unsigned int hash;
 306
 307         hash = fib_info_hashfn(nfi);
 308         head = &fib_info_hash[hash];
 309
 310         hlist_for_each_entry(fi, head, fib_hash) {
 311                 if (!net_eq(fi->fib_net, nfi->fib_net))
 312                         continue;
 313                 if (fi->fib_nhs != nfi->fib_nhs)
 314                         continue;
 315                 if (nfi->fib_protocol == fi->fib_protocol &&
 316                     nfi->fib_scope == fi->fib_scope &&
 317                     nfi->fib_prefsrc == fi->fib_prefsrc &&
 318                     nfi->fib_priority == fi->fib_priority &&
 319                     nfi->fib_type == fi->fib_type &&
 320                     memcmp(nfi->fib_metrics, fi->fib_metrics,
 321                            sizeof(u32) * RTAX_MAX) == 0 &&
 322                     ((nfi->fib_flags ^ fi->fib_flags) & ~RTNH_F_DEAD) == 0 &&
 323                     (nfi->fib_nhs == 0 || nh_comp(fi, nfi) == 0))
 324                         return fi;
 325         }
 326
 327         return NULL;
 328 }
 329
 330 /* Check, that the gateway is already configured.
 331  * Used only by redirect accept routine.
 332  */
 333 int ip_fib_check_default(__be32 gw, struct net_device *dev)
 334 {
 335         struct hlist_head *head;
 336         struct fib_nh *nh;
 337         unsigned int hash;
 338
 339         spin_lock(&fib_info_lock);
 340
 341         hash = fib_devindex_hashfn(dev->ifindex);
 342         head = &fib_info_devhash[hash];
 343         hlist_for_each_entry(nh, head, nh_hash) {
 344                 if (nh->nh_dev == dev &&
 345                     nh->nh_gw == gw &&
 346                     !(nh->nh_flags & RTNH_F_DEAD)) {
 347                         spin_unlock(&fib_info_lock);
 348                         return 0;
 349                 }
 350         }
 351
 352         spin_unlock(&fib_info_lock);
 353
 354         return -1;
 355 }
 356
 357 static inline size_t fib_nlmsg_size(struct fib_info *fi)
 358 {
 359         size_t payload = NLMSG_ALIGN(sizeof(struct rtmsg))
 360                          + nla_total_size(4) /* RTA_TABLE */
 361                          + nla_total_size(4) /* RTA_DST */
 362                          + nla_total_size(4) /* RTA_PRIORITY */
 363                          + nla_total_size(4); /* RTA_PREFSRC */
 364
 365         /* space for nested metrics */
 366         payload += nla_total_size((RTAX_MAX * nla_total_size(4)));
 367
 368         if (fi->fib_nhs) {
 369                 /* Also handles the special case fib_nhs == 1 */
 370
 371                 /* each nexthop is packed in an attribute */
 372                 size_t nhsize = nla_total_size(sizeof(struct rtnexthop));
 373
 374                 /* may contain flow and gateway attribute */
 375                 nhsize += 2 * nla_total_size(4);
 376
 377                 /* all nexthops are packed in a nested attribute */
 378                 payload += nla_total_size(fi->fib_nhs * nhsize);
 379         }
 380
 381         return payload;
 382 }
 383
 384 void rtmsg_fib(int event, __be32 key, struct fib_alias *fa,
 385                int dst_len, u32 tb_id, const struct nl_info *info,
 386                unsigned int nlm_flags)
 387 {
 388         struct sk_buff *skb;
 389         u32 seq = info->nlh ? info->nlh->nlmsg_seq : 0;
 390         int err = -ENOBUFS;
 391
 392         skb = nlmsg_new(fib_nlmsg_size(fa->fa_info), GFP_KERNEL);
 393         if (skb == NULL)
 394                 goto errout;
 395
 396         err = fib_dump_info(skb, info->portid, seq, event, tb_id,
 397                             fa->fa_type, key, dst_len,
 398                             fa->fa_tos, fa->fa_info, nlm_flags);
 399         if (err < 0) {
 400                 /* -EMSGSIZE implies BUG in fib_nlmsg_size() */
 401                 WARN_ON(err == -EMSGSIZE);
 402                 kfree_skb(skb);
 403                 goto errout;
 404         }
 405         rtnl_notify(skb, info->nl_net, info->portid, RTNLGRP_IPV4_ROUTE,
 406                     info->nlh, GFP_KERNEL);
 407         return;
 408 errout:
 409         if (err < 0)
 410                 rtnl_set_sk_err(info->nl_net, RTNLGRP_IPV4_ROUTE, err);
 411 }
 412
 413 /* Return the first fib alias matching TOS with
 414  * priority less than or equal to PRIO.
 415  */
 416 struct fib_alias *fib_find_alias(struct list_head *fah, u8 tos, u32 prio)
 417 {
 418         if (fah) {
 419                 struct fib_alias *fa;
 420                 list_for_each_entry(fa, fah, fa_list) {
 421                         if (fa->fa_tos > tos)
 422                                 continue;
 423                         if (fa->fa_info->fib_priority >= prio ||
 424                             fa->fa_tos < tos)
 425                                 return fa;
 426                 }
 427         }
 428         return NULL;
 429 }
 430
 431 static int fib_detect_death(struct fib_info *fi, int order,
 432                             struct fib_info **last_resort, int *last_idx,
 433                             int dflt)
 434 {
 435         struct neighbour *n;
 436         int state = NUD_NONE;
 437
 438         n = neigh_lookup(&arp_tbl, &fi->fib_nh[0].nh_gw, fi->fib_dev);
 439         if (n) {
 440                 state = n->nud_state;
 441                 neigh_release(n);
 442         }
 443         if (state == NUD_REACHABLE)
 444                 return 0;
 445         if ((state & NUD_VALID) && order != dflt)
 446                 return 0;
 447         if ((state & NUD_VALID) ||
 448             (*last_idx < 0 && order > dflt)) {
 449                 *last_resort = fi;
 450                 *last_idx = order;
 451         }
 452         return 1;
 453 }
 454
 455 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 456
 457 static int fib_count_nexthops(struct rtnexthop *rtnh, int remaining)
 458 {
 459         int nhs = 0;
 460
 461         while (rtnh_ok(rtnh, remaining)) {
 462                 nhs++;
 463                 rtnh = rtnh_next(rtnh, &remaining);
 464         }
 465
 466         /* leftover implies invalid nexthop configuration, discard it */
 467         return remaining > 0 ? 0 : nhs;
 468 }
 469
 470 static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
 471                        int remaining, struct fib_config *cfg)
 472 {
 473         change_nexthops(fi) {
 474                 int attrlen;
 475
 476                 if (!rtnh_ok(rtnh, remaining))
 477                         return -EINVAL;
 478
 479                 nexthop_nh->nh_flags =
 480                         (cfg->fc_flags & ~0xFF) | rtnh->rtnh_flags;
 481                 nexthop_nh->nh_oif = rtnh->rtnh_ifindex;
 482                 nexthop_nh->nh_weight = rtnh->rtnh_hops + 1;
 483
 484                 attrlen = rtnh_attrlen(rtnh);
 485                 if (attrlen > 0) {
 486                         struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
 487
 488                         nla = nla_find(attrs, attrlen, RTA_GATEWAY);
 489                         nexthop_nh->nh_gw = nla ? nla_get_be32(nla) : 0;
 490 #ifdef CONFIG_IP_ROUTE_CLASSID
 491                         nla = nla_find(attrs, attrlen, RTA_FLOW);
 492                         nexthop_nh->nh_tclassid = nla ? nla_get_u32(nla) : 0;
 493                         if (nexthop_nh->nh_tclassid)
 494                                 fi->fib_net->ipv4.fib_num_tclassid_users++;
 495 #endif
 496                 }
 497
 498                 rtnh = rtnh_next(rtnh, &remaining);
 499         } endfor_nexthops(fi);
 500
 501         return 0;
 502 }
 503
 504 #endif
 505
 506 int fib_nh_match(struct fib_config *cfg, struct fib_info *fi)
 507 {
 508 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 509         struct rtnexthop *rtnh;
 510         int remaining;
 511 #endif
 512
 513         if (cfg->fc_priority && cfg->fc_priority != fi->fib_priority)
 514                 return 1;
 515
 516         if (cfg->fc_oif || cfg->fc_gw) {
 517                 if ((!cfg->fc_oif || cfg->fc_oif == fi->fib_nh->nh_oif) &&
 518                     (!cfg->fc_gw  || cfg->fc_gw == fi->fib_nh->nh_gw))
 519                         return 0;
 520                 return 1;
 521         }
 522
 523 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 524         if (cfg->fc_mp == NULL)
 525                 return 0;
 526
 527         rtnh = cfg->fc_mp;
 528         remaining = cfg->fc_mp_len;
 529
 530         for_nexthops(fi) {
 531                 int attrlen;
 532
 533                 if (!rtnh_ok(rtnh, remaining))
 534                         return -EINVAL;
 535
 536                 if (rtnh->rtnh_ifindex && rtnh->rtnh_ifindex != nh->nh_oif)
 537                         return 1;
 538
 539                 attrlen = rtnh_attrlen(rtnh);
 540                 if (attrlen < 0) {
 541                         struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
 542
 543                         nla = nla_find(attrs, attrlen, RTA_GATEWAY);
 544                         if (nla && nla_get_be32(nla) != nh->nh_gw)
 545                                 return 1;
 546 #ifdef CONFIG_IP_ROUTE_CLASSID
 547                         nla = nla_find(attrs, attrlen, RTA_FLOW);
 548                         if (nla && nla_get_u32(nla) != nh->nh_tclassid)
 549                                 return 1;
 550 #endif
 551                 }
 552
 553                 rtnh = rtnh_next(rtnh, &remaining);
 554         } endfor_nexthops(fi);
 555 #endif
 556         return 0;
 557 }
 558
 559
 560 /*
 561  * Picture
 562  * -------
 563  *
 564  * Semantics of nexthop is very messy by historical reasons.
 565  * We have to take into account, that:
 566  * a) gateway can be actually local interface address,
 567  *    so that gatewayed route is direct.
 568  * b) gateway must be on-link address, possibly
 569  *    described not by an ifaddr, but also by a direct route.
 570  * c) If both gateway and interface are specified, they should not
 571  *    contradict.
 572  * d) If we use tunnel routes, gateway could be not on-link.
 573  *
 574  * Attempt to reconcile all of these (alas, self-contradictory) conditions
 575  * results in pretty ugly and hairy code with obscure logic.
 576  *
 577  * I chose to generalized it instead, so that the size
 578  * of code does not increase practically, but it becomes
 579  * much more general.
 580  * Every prefix is assigned a "scope" value: "host" is local address,
 581  * "link" is direct route,
 582  * [ ... "site" ... "interior" ... ]
 583  * and "universe" is true gateway route with global meaning.
 584  *
 585  * Every prefix refers to a set of "nexthop"s (gw, oif),
 586  * where gw must have narrower scope. This recursion stops
 587  * when gw has LOCAL scope or if "nexthop" is declared ONLINK,
 588  * which means that gw is forced to be on link.
 589  *
 590  * Code is still hairy, but now it is apparently logically
 591  * consistent and very flexible. F.e. as by-product it allows
 592  * to co-exists in peace independent exterior and interior
 593  * routing processes.
 594  *
 595  * Normally it looks as following.
 596  *
 597  * {universe prefix}  -> (gw, oif) [scope link]
 598  *                |
 599  *                |-> {link prefix} -> (gw, oif) [scope local]
 600  *                                      |
 601  *                                      |-> {local prefix} (terminal node)
 602  */
 603 static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
 604                         struct fib_nh *nh)
 605 {
 606         int err;
 607         struct net *net;
 608         struct net_device *dev;
 609
 610         net = cfg->fc_nlinfo.nl_net;
 611         if (nh->nh_gw) {
 612                 struct fib_result res;
 613
 614                 if (nh->nh_flags & RTNH_F_ONLINK) {
 615
 616                         if (cfg->fc_scope >= RT_SCOPE_LINK)
 617                                 return -EINVAL;
 618                         if (inet_addr_type(net, nh->nh_gw) != RTN_UNICAST)
 619                                 return -EINVAL;
 620                         dev = __dev_get_by_index(net, nh->nh_oif);
 621                         if (!dev)
 622                                 return -ENODEV;
 623                         if (!(dev->flags & IFF_UP))
 624                                 return -ENETDOWN;
 625                         nh->nh_dev = dev;
 626                         dev_hold(dev);
 627                         nh->nh_scope = RT_SCOPE_LINK;
 628                         return 0;
 629                 }
 630                 rcu_read_lock();
 631                 {
 632                         struct flowi4 fl4 = {
 633                                 .daddr = nh->nh_gw,
 634                                 .flowi4_scope = cfg->fc_scope + 1,
 635                                 .flowi4_oif = nh->nh_oif,
 636                                 .flowi4_iif = LOOPBACK_IFINDEX,
 637                         };
 638
 639                         /* It is not necessary, but requires a bit of thinking */
 640                         if (fl4.flowi4_scope < RT_SCOPE_LINK)
 641                                 fl4.flowi4_scope = RT_SCOPE_LINK;
 642                         err = fib_lookup(net, &fl4, &res);
 643                         if (err) {
 644                                 rcu_read_unlock();
 645                                 return err;
 646                         }
 647                 }
 648                 err = -EINVAL;
 649                 if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
 650                         goto out;
 651                 nh->nh_scope = res.scope;
 652                 nh->nh_oif = FIB_RES_OIF(res);
 653                 nh->nh_dev = dev = FIB_RES_DEV(res);
 654                 if (!dev)
 655                         goto out;
 656                 dev_hold(dev);
 657                 err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
 658         } else {
 659                 struct in_device *in_dev;
 660
 661                 if (nh->nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK))
 662                         return -EINVAL;
 663
 664                 rcu_read_lock();
 665                 err = -ENODEV;
 666                 in_dev = inetdev_by_index(net, nh->nh_oif);
 667                 if (in_dev == NULL)
 668                         goto out;
 669                 err = -ENETDOWN;
 670                 if (!(in_dev->dev->flags & IFF_UP))
 671                         goto out;
 672                 nh->nh_dev = in_dev->dev;
 673                 dev_hold(nh->nh_dev);
 674                 nh->nh_scope = RT_SCOPE_HOST;
 675                 err = 0;
 676         }
 677 out:
 678         rcu_read_unlock();
 679         return err;
 680 }
 681
 682 static inline unsigned int fib_laddr_hashfn(__be32 val)
 683 {
 684         unsigned int mask = (fib_info_hash_size - 1);
 685
 686         return ((__force u32)val ^
 687                 ((__force u32)val >> 7) ^
 688                 ((__force u32)val >> 14)) & mask;
 689 }
 690
 691 static struct hlist_head *fib_info_hash_alloc(int bytes)
 692 {
 693         if (bytes <= PAGE_SIZE)
 694                 return kzalloc(bytes, GFP_KERNEL);
 695         else
 696                 return (struct hlist_head *)
 697                         __get_free_pages(GFP_KERNEL | __GFP_ZERO,
 698                                          get_order(bytes));
 699 }
 700
 701 static void fib_info_hash_free(struct hlist_head *hash, int bytes)
 702 {
 703         if (!hash)
 704                 return;
 705
 706         if (bytes <= PAGE_SIZE)
 707                 kfree(hash);
 708         else
 709                 free_pages((unsigned long) hash, get_order(bytes));
 710 }
 711
 712 static void fib_info_hash_move(struct hlist_head *new_info_hash,
 713                                struct hlist_head *new_laddrhash,
 714                                unsigned int new_size)
 715 {
 716         struct hlist_head *old_info_hash, *old_laddrhash;
 717         unsigned int old_size = fib_info_hash_size;
 718         unsigned int i, bytes;
 719
 720         spin_lock_bh(&fib_info_lock);
 721         old_info_hash = fib_info_hash;
 722         old_laddrhash = fib_info_laddrhash;
 723         fib_info_hash_size = new_size;
 724
 725         for (i = 0; i < old_size; i++) {
 726                 struct hlist_head *head = &fib_info_hash[i];
 727                 struct hlist_node *n;
 728                 struct fib_info *fi;
 729
 730                 hlist_for_each_entry_safe(fi, n, head, fib_hash) {
 731                         struct hlist_head *dest;
 732                         unsigned int new_hash;
 733
 734                         hlist_del(&fi->fib_hash);
 735
 736                         new_hash = fib_info_hashfn(fi);
 737                         dest = &new_info_hash[new_hash];
 738                         hlist_add_head(&fi->fib_hash, dest);
 739                 }
 740         }
 741         fib_info_hash = new_info_hash;
 742
 743         for (i = 0; i < old_size; i++) {
 744                 struct hlist_head *lhead = &fib_info_laddrhash[i];
 745                 struct hlist_node *n;
 746                 struct fib_info *fi;
 747
 748                 hlist_for_each_entry_safe(fi, n, lhead, fib_lhash) {
 749                         struct hlist_head *ldest;
 750                         unsigned int new_hash;
 751
 752                         hlist_del(&fi->fib_lhash);
 753
 754                         new_hash = fib_laddr_hashfn(fi->fib_prefsrc);
 755                         ldest = &new_laddrhash[new_hash];
 756                         hlist_add_head(&fi->fib_lhash, ldest);
 757                 }
 758         }
 759         fib_info_laddrhash = new_laddrhash;
 760
 761         spin_unlock_bh(&fib_info_lock);
 762
 763         bytes = old_size * sizeof(struct hlist_head *);
 764         fib_info_hash_free(old_info_hash, bytes);
 765         fib_info_hash_free(old_laddrhash, bytes);
 766 }
 767
 768 __be32 fib_info_update_nh_saddr(struct net *net, struct fib_nh *nh)
 769 {
 770         nh->nh_saddr = inet_select_addr(nh->nh_dev,
 771                                         nh->nh_gw,
 772                                         nh->nh_parent->fib_scope);
 773         nh->nh_saddr_genid = atomic_read(&net->ipv4.dev_addr_genid);
 774
 775         return nh->nh_saddr;
 776 }
 777
 778 struct fib_info *fib_create_info(struct fib_config *cfg)
 779 {
 780         int err;
 781         struct fib_info *fi = NULL;
 782         struct fib_info *ofi;
 783         int nhs = 1;
 784         struct net *net = cfg->fc_nlinfo.nl_net;
 785
 786         if (cfg->fc_type > RTN_MAX)
 787                 goto err_inval;
 788
 789         /* Fast check to catch the most weird cases */
 790         if (fib_props[cfg->fc_type].scope > cfg->fc_scope)
 791                 goto err_inval;
 792
 793 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 794         if (cfg->fc_mp) {
 795                 nhs = fib_count_nexthops(cfg->fc_mp, cfg->fc_mp_len);
 796                 if (nhs == 0)
 797                         goto err_inval;
 798         }
 799 #endif
 800
 801         err = -ENOBUFS;
 802         if (fib_info_cnt >= fib_info_hash_size) {
 803                 unsigned int new_size = fib_info_hash_size << 1;
 804                 struct hlist_head *new_info_hash;
 805                 struct hlist_head *new_laddrhash;
 806                 unsigned int bytes;
 807
 808                 if (!new_size)
 809                         new_size = 16;
 810                 bytes = new_size * sizeof(struct hlist_head *);
 811                 new_info_hash = fib_info_hash_alloc(bytes);
 812                 new_laddrhash = fib_info_hash_alloc(bytes);
 813                 if (!new_info_hash || !new_laddrhash) {
 814                         fib_info_hash_free(new_info_hash, bytes);
 815                         fib_info_hash_free(new_laddrhash, bytes);
 816                 } else
 817                         fib_info_hash_move(new_info_hash, new_laddrhash, new_size);
 818
 819                 if (!fib_info_hash_size)
 820                         goto failure;
 821         }
 822
 823         fi = kzalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL);
 824         if (fi == NULL)
 825                 goto failure;
 826         fib_info_cnt++;
 827         if (cfg->fc_mx) {
 828                 fi->fib_metrics = kzalloc(sizeof(u32) * RTAX_MAX, GFP_KERNEL);
 829                 if (!fi->fib_metrics)
 830                         goto failure;
 831         } else
 832                 fi->fib_metrics = (u32 *) dst_default_metrics;
 833
 834         fi->fib_net = hold_net(net);
 835         fi->fib_protocol = cfg->fc_protocol;
 836         fi->fib_scope = cfg->fc_scope;
 837         fi->fib_flags = cfg->fc_flags;
 838         fi->fib_priority = cfg->fc_priority;
 839         fi->fib_prefsrc = cfg->fc_prefsrc;
 840         fi->fib_type = cfg->fc_type;
 841
 842         fi->fib_nhs = nhs;
 843         change_nexthops(fi) {
 844                 nexthop_nh->nh_parent = fi;
 845                 nexthop_nh->nh_pcpu_rth_output = alloc_percpu(struct rtable __rcu *);
 846                 if (!nexthop_nh->nh_pcpu_rth_output)
 847                         goto failure;
 848         } endfor_nexthops(fi)
 849
 850         if (cfg->fc_mx) {
 851                 struct nlattr *nla;
 852                 int remaining;
 853
 854                 nla_for_each_attr(nla, cfg->fc_mx, cfg->fc_mx_len, remaining) {
 855                         int type = nla_type(nla);
 856
 857                         if (type) {
 858                                 u32 val;
 859
 860                                 if (type > RTAX_MAX)
 861                                         goto err_inval;
 862                                 val = nla_get_u32(nla);
 863                                 if (type == RTAX_ADVMSS && val > 65535 - 40)
 864                                         val = 65535 - 40;
 865                                 if (type == RTAX_MTU && val > 65535 - 15)
 866                                         val = 65535 - 15;
 867                                 fi->fib_metrics[type - 1] = val;
 868                         }
 869                 }
 870         }
 871
 872         if (cfg->fc_mp) {
 873 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 874                 err = fib_get_nhs(fi, cfg->fc_mp, cfg->fc_mp_len, cfg);
 875                 if (err != 0)
 876                         goto failure;
 877                 if (cfg->fc_oif && fi->fib_nh->nh_oif != cfg->fc_oif)
 878                         goto err_inval;
 879                 if (cfg->fc_gw && fi->fib_nh->nh_gw != cfg->fc_gw)
 880                         goto err_inval;
 881 #ifdef CONFIG_IP_ROUTE_CLASSID
 882                 if (cfg->fc_flow && fi->fib_nh->nh_tclassid != cfg->fc_flow)
 883                         goto err_inval;
 884 #endif
 885 #else
 886                 goto err_inval;
 887 #endif
 888         } else {
 889                 struct fib_nh *nh = fi->fib_nh;
 890
 891                 nh->nh_oif = cfg->fc_oif;
 892                 nh->nh_gw = cfg->fc_gw;
 893                 nh->nh_flags = cfg->fc_flags;
 894 #ifdef CONFIG_IP_ROUTE_CLASSID
 895                 nh->nh_tclassid = cfg->fc_flow;
 896                 if (nh->nh_tclassid)
 897                         fi->fib_net->ipv4.fib_num_tclassid_users++;
 898 #endif
 899 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 900                 nh->nh_weight = 1;
 901 #endif
 902         }
 903
 904         if (fib_props[cfg->fc_type].error) {
 905                 if (cfg->fc_gw || cfg->fc_oif || cfg->fc_mp)
 906                         goto err_inval;
 907                 goto link_it;
 908         } else {
 909                 switch (cfg->fc_type) {
 910                 case RTN_UNICAST:
 911                 case RTN_LOCAL:
 912                 case RTN_BROADCAST:
 913                 case RTN_ANYCAST:
 914                 case RTN_MULTICAST:
 915                         break;
 916                 default:
 917                         goto err_inval;
 918                 }
 919         }
 920
 921         if (cfg->fc_scope > RT_SCOPE_HOST)
 922                 goto err_inval;
 923
 924         if (cfg->fc_scope == RT_SCOPE_HOST) {
 925                 struct fib_nh *nh = fi->fib_nh;
 926
 927                 /* Local address is added. */
 928                 if (nhs != 1 || nh->nh_gw)
 929                         goto err_inval;
 930                 nh->nh_scope = RT_SCOPE_NOWHERE;
 931                 nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
 932                 err = -ENODEV;
 933                 if (nh->nh_dev == NULL)
 934                         goto failure;
 935         } else {
 936                 change_nexthops(fi) {
 937                         err = fib_check_nh(cfg, fi, nexthop_nh);
 938                         if (err != 0)
 939                                 goto failure;
 940                 } endfor_nexthops(fi)
 941         }
 942
 943         if (fi->fib_prefsrc) {
 944                 if (cfg->fc_type != RTN_LOCAL || !cfg->fc_dst ||
 945                     fi->fib_prefsrc != cfg->fc_dst)
 946                         if (inet_addr_type(net, fi->fib_prefsrc) != RTN_LOCAL)
 947                                 goto err_inval;
 948         }
 949
 950         change_nexthops(fi) {
 951                 fib_info_update_nh_saddr(net, nexthop_nh);
 952         } endfor_nexthops(fi)
 953
 954 link_it:
 955         ofi = fib_find_info(fi);
 956         if (ofi) {
 957                 fi->fib_dead = 1;
 958                 free_fib_info(fi);
 959                 ofi->fib_treeref++;
 960                 return ofi;
 961         }
 962
 963         fi->fib_treeref++;
 964         atomic_inc(&fi->fib_clntref);
 965         spin_lock_bh(&fib_info_lock);
 966         hlist_add_head(&fi->fib_hash,
 967                        &fib_info_hash[fib_info_hashfn(fi)]);
 968         if (fi->fib_prefsrc) {
 969                 struct hlist_head *head;
 970
 971                 head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)];
 972                 hlist_add_head(&fi->fib_lhash, head);
 973         }
 974         change_nexthops(fi) {
 975                 struct hlist_head *head;
 976                 unsigned int hash;
 977
 978                 if (!nexthop_nh->nh_dev)
 979                         continue;
 980                 hash = fib_devindex_hashfn(nexthop_nh->nh_dev->ifindex);
 981                 head = &fib_info_devhash[hash];
 982                 hlist_add_head(&nexthop_nh->nh_hash, head);
 983         } endfor_nexthops(fi)
 984         spin_unlock_bh(&fib_info_lock);
 985         return fi;
 986
 987 err_inval:
 988         err = -EINVAL;
 989
 990 failure:
 991         if (fi) {
 992                 fi->fib_dead = 1;
 993                 free_fib_info(fi);
 994         }
 995
 996         return ERR_PTR(err);
 997 }
 998
 999 int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event,
1000                   u32 tb_id, u8 type, __be32 dst, int dst_len, u8 tos,
1001                   struct fib_info *fi, unsigned int flags)
1002 {
1003         struct nlmsghdr *nlh;
1004         struct rtmsg *rtm;
1005
1006         nlh = nlmsg_put(skb, portid, seq, event, sizeof(*rtm), flags);
1007         if (nlh == NULL)
1008                 return -EMSGSIZE;
1009
1010         rtm = nlmsg_data(nlh);
1011         rtm->rtm_family = AF_INET;
1012         rtm->rtm_dst_len = dst_len;
1013         rtm->rtm_src_len = 0;
1014         rtm->rtm_tos = tos;
1015         if (tb_id < 256)
1016                 rtm->rtm_table = tb_id;
1017         else
1018                 rtm->rtm_table = RT_TABLE_COMPAT;
1019         if (nla_put_u32(skb, RTA_TABLE, tb_id))
1020                 goto nla_put_failure;
1021         rtm->rtm_type = type;
1022         rtm->rtm_flags = fi->fib_flags;
1023         rtm->rtm_scope = fi->fib_scope;
1024         rtm->rtm_protocol = fi->fib_protocol;
1025
1026         if (rtm->rtm_dst_len &&
1027             nla_put_be32(skb, RTA_DST, dst))
1028                 goto nla_put_failure;
1029         if (fi->fib_priority &&
1030             nla_put_u32(skb, RTA_PRIORITY, fi->fib_priority))
1031                 goto nla_put_failure;
1032         if (rtnetlink_put_metrics(skb, fi->fib_metrics) < 0)
1033                 goto nla_put_failure;
1034
1035         if (fi->fib_prefsrc &&
1036             nla_put_be32(skb, RTA_PREFSRC, fi->fib_prefsrc))
1037                 goto nla_put_failure;
1038         if (fi->fib_nhs == 1) {
1039                 if (fi->fib_nh->nh_gw &&
1040                     nla_put_be32(skb, RTA_GATEWAY, fi->fib_nh->nh_gw))
1041                         goto nla_put_failure;
1042                 if (fi->fib_nh->nh_oif &&
1043                     nla_put_u32(skb, RTA_OIF, fi->fib_nh->nh_oif))
1044                         goto nla_put_failure;
1045 #ifdef CONFIG_IP_ROUTE_CLASSID
1046                 if (fi->fib_nh[0].nh_tclassid &&
1047                     nla_put_u32(skb, RTA_FLOW, fi->fib_nh[0].nh_tclassid))
1048                         goto nla_put_failure;
1049 #endif
1050         }
1051 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1052         if (fi->fib_nhs > 1) {
1053                 struct rtnexthop *rtnh;
1054                 struct nlattr *mp;
1055
1056                 mp = nla_nest_start(skb, RTA_MULTIPATH);
1057                 if (mp == NULL)
1058                         goto nla_put_failure;
1059
1060                 for_nexthops(fi) {
1061                         rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));
1062                         if (rtnh == NULL)
1063                                 goto nla_put_failure;
1064
1065                         rtnh->rtnh_flags = nh->nh_flags & 0xFF;
1066                         rtnh->rtnh_hops = nh->nh_weight - 1;
1067                         rtnh->rtnh_ifindex = nh->nh_oif;
1068
1069                         if (nh->nh_gw &&
1070                             nla_put_be32(skb, RTA_GATEWAY, nh->nh_gw))
1071                                 goto nla_put_failure;
1072 #ifdef CONFIG_IP_ROUTE_CLASSID
1073                         if (nh->nh_tclassid &&
1074                             nla_put_u32(skb, RTA_FLOW, nh->nh_tclassid))
1075                                 goto nla_put_failure;
1076 #endif
1077                         /* length of rtnetlink header + attributes */
1078                         rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *) rtnh;
1079                 } endfor_nexthops(fi);
1080
1081                 nla_nest_end(skb, mp);
1082         }
1083 #endif
1084         return nlmsg_end(skb, nlh);
1085
1086 nla_put_failure:
1087         nlmsg_cancel(skb, nlh);
1088         return -EMSGSIZE;
1089 }
1090
1091 /*
1092  * Update FIB if:
1093  * - local address disappeared -> we must delete all the entries
1094  *   referring to it.
1095  * - device went down -> we must shutdown all nexthops going via it.
1096  */
1097 int fib_sync_down_addr(struct net *net, __be32 local)
1098 {
1099         int ret = 0;
1100         unsigned int hash = fib_laddr_hashfn(local);
1101         struct hlist_head *head = &fib_info_laddrhash[hash];
1102         struct fib_info *fi;
1103
1104         if (fib_info_laddrhash == NULL || local == 0)
1105                 return 0;
1106
1107         hlist_for_each_entry(fi, head, fib_lhash) {
1108                 if (!net_eq(fi->fib_net, net))
1109                         continue;
1110                 if (fi->fib_prefsrc == local) {
1111                         fi->fib_flags |= RTNH_F_DEAD;
1112                         ret++;
1113                 }
1114         }
1115         return ret;
1116 }
1117
1118 int fib_sync_down_dev(struct net_device *dev, int force)
1119 {
1120         int ret = 0;
1121         int scope = RT_SCOPE_NOWHERE;
1122         struct fib_info *prev_fi = NULL;
1123         unsigned int hash = fib_devindex_hashfn(dev->ifindex);
1124         struct hlist_head *head = &fib_info_devhash[hash];
1125         struct fib_nh *nh;
1126
1127         if (force)
1128                 scope = -1;
1129
1130         hlist_for_each_entry(nh, head, nh_hash) {
1131                 struct fib_info *fi = nh->nh_parent;
1132                 int dead;
1133
1134                 BUG_ON(!fi->fib_nhs);
1135                 if (nh->nh_dev != dev || fi == prev_fi)
1136                         continue;
1137                 prev_fi = fi;
1138                 dead = 0;
1139                 change_nexthops(fi) {
1140                         if (nexthop_nh->nh_flags & RTNH_F_DEAD)
1141                                 dead++;
1142                         else if (nexthop_nh->nh_dev == dev &&
1143                                  nexthop_nh->nh_scope != scope) {
1144                                 nexthop_nh->nh_flags |= RTNH_F_DEAD;
1145 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1146                                 spin_lock_bh(&fib_multipath_lock);
1147                                 fi->fib_power -= nexthop_nh->nh_power;
1148                                 nexthop_nh->nh_power = 0;
1149                                 spin_unlock_bh(&fib_multipath_lock);
1150 #endif
1151                                 dead++;
1152                         }
1153 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1154                         if (force > 1 && nexthop_nh->nh_dev == dev) {
1155                                 dead = fi->fib_nhs;
1156                                 break;
1157                         }
1158 #endif
1159                 } endfor_nexthops(fi)
1160                 if (dead == fi->fib_nhs) {
1161                         fi->fib_flags |= RTNH_F_DEAD;
1162                         ret++;
1163                 }
1164         }
1165
1166         return ret;
1167 }
1168
1169 /* Must be invoked inside of an RCU protected region.  */
1170 void fib_select_default(struct fib_result *res)
1171 {
1172         struct fib_info *fi = NULL, *last_resort = NULL;
1173         struct list_head *fa_head = res->fa_head;
1174         struct fib_table *tb = res->table;
1175         int order = -1, last_idx = -1;
1176         struct fib_alias *fa;
1177
1178         list_for_each_entry_rcu(fa, fa_head, fa_list) {
1179                 struct fib_info *next_fi = fa->fa_info;
1180
1181                 if (next_fi->fib_scope != res->scope ||
1182                     fa->fa_type != RTN_UNICAST)
1183                         continue;
1184
1185                 if (next_fi->fib_priority > res->fi->fib_priority)
1186                         break;
1187                 if (!next_fi->fib_nh[0].nh_gw ||
1188                     next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
1189                         continue;
1190
1191                 fib_alias_accessed(fa);
1192
1193                 if (fi == NULL) {
1194                         if (next_fi != res->fi)
1195                                 break;
1196                 } else if (!fib_detect_death(fi, order, &last_resort,
1197                                              &last_idx, tb->tb_default)) {
1198                         fib_result_assign(res, fi);
1199                         tb->tb_default = order;
1200                         goto out;
1201                 }
1202                 fi = next_fi;
1203                 order++;
1204         }
1205
1206         if (order <= 0 || fi == NULL) {
1207                 tb->tb_default = -1;
1208                 goto out;
1209         }
1210
1211         if (!fib_detect_death(fi, order, &last_resort, &last_idx,
1212                                 tb->tb_default)) {
1213                 fib_result_assign(res, fi);
1214                 tb->tb_default = order;
1215                 goto out;
1216         }
1217
1218         if (last_idx >= 0)
1219                 fib_result_assign(res, last_resort);
1220         tb->tb_default = last_idx;
1221 out:
1222         return;
1223 }
1224
1225 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1226
1227 /*
1228  * Dead device goes up. We wake up dead nexthops.
1229  * It takes sense only on multipath routes.
1230  */
1231 int fib_sync_up(struct net_device *dev)
1232 {
1233         struct fib_info *prev_fi;
1234         unsigned int hash;
1235         struct hlist_head *head;
1236         struct fib_nh *nh;
1237         int ret;
1238
1239         if (!(dev->flags & IFF_UP))
1240                 return 0;
1241
1242         prev_fi = NULL;
1243         hash = fib_devindex_hashfn(dev->ifindex);
1244         head = &fib_info_devhash[hash];
1245         ret = 0;
1246
1247         hlist_for_each_entry(nh, head, nh_hash) {
1248                 struct fib_info *fi = nh->nh_parent;
1249                 int alive;
1250
1251                 BUG_ON(!fi->fib_nhs);
1252                 if (nh->nh_dev != dev || fi == prev_fi)
1253                         continue;
1254
1255                 prev_fi = fi;
1256                 alive = 0;
1257                 change_nexthops(fi) {
1258                         if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1259                                 alive++;
1260                                 continue;
1261                         }
1262                         if (nexthop_nh->nh_dev == NULL ||
1263                             !(nexthop_nh->nh_dev->flags & IFF_UP))
1264                                 continue;
1265                         if (nexthop_nh->nh_dev != dev ||
1266                             !__in_dev_get_rtnl(dev))
1267                                 continue;
1268                         alive++;
1269                         spin_lock_bh(&fib_multipath_lock);
1270                         nexthop_nh->nh_power = 0;
1271                         nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
1272                         spin_unlock_bh(&fib_multipath_lock);
1273                 } endfor_nexthops(fi)
1274
1275                 if (alive > 0) {
1276                         fi->fib_flags &= ~RTNH_F_DEAD;
1277                         ret++;
1278                 }
1279         }
1280
1281         return ret;
1282 }
1283
1284 /*
1285  * The algorithm is suboptimal, but it provides really
1286  * fair weighted route distribution.
1287  */
1288 void fib_select_multipath(struct fib_result *res)
1289 {
1290         struct fib_info *fi = res->fi;
1291         int w;
1292
1293         spin_lock_bh(&fib_multipath_lock);
1294         if (fi->fib_power <= 0) {
1295                 int power = 0;
1296                 change_nexthops(fi) {
1297                         if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1298                                 power += nexthop_nh->nh_weight;
1299                                 nexthop_nh->nh_power = nexthop_nh->nh_weight;
1300                         }
1301                 } endfor_nexthops(fi);
1302                 fi->fib_power = power;
1303                 if (power <= 0) {
1304                         spin_unlock_bh(&fib_multipath_lock);
1305                         /* Race condition: route has just become dead. */
1306                         res->nh_sel = 0;
1307                         return;
1308                 }
1309         }
1310
1311
1312         /* w should be random number [0..fi->fib_power-1],
1313          * it is pretty bad approximation.
1314          */
1315
1316         w = jiffies % fi->fib_power;
1317
1318         change_nexthops(fi) {
1319                 if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
1320                     nexthop_nh->nh_power) {
1321                         w -= nexthop_nh->nh_power;
1322                         if (w <= 0) {
1323                                 nexthop_nh->nh_power--;
1324                                 fi->fib_power--;
1325                                 res->nh_sel = nhsel;
1326                                 spin_unlock_bh(&fib_multipath_lock);
1327                                 return;
1328                         }
1329                 }
1330         } endfor_nexthops(fi);
1331
1332         /* Race condition: route has just become dead. */
1333         res->nh_sel = 0;
1334         spin_unlock_bh(&fib_multipath_lock);
1335 }
1336 #endif