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