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