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