linux/net/ipv4/fib_semantics.c
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   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
  48static DEFINE_SPINLOCK(fib_info_lock);
  49static struct hlist_head *fib_info_hash;
  50static struct hlist_head *fib_info_laddrhash;
  51static unsigned int fib_info_hash_size;
  52static unsigned int fib_info_cnt;
  53
  54#define DEVINDEX_HASHBITS 8
  55#define DEVINDEX_HASHSIZE (1U << DEVINDEX_HASHBITS)
  56static struct hlist_head fib_info_devhash[DEVINDEX_HASHSIZE];
  57
  58#ifdef CONFIG_IP_ROUTE_MULTIPATH
  59
  60static 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
  92const 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
 143static 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
 158static 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
 182static 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 */
 200static 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
 219void 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
 235void 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
 253static 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
 274static 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
 283static 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
 298static struct fib_info *fib_find_info(const struct fib_info *nfi)
 299{
 300        struct hlist_head *head;
 301        struct hlist_node *node;
 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, node, 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 */
 331int ip_fib_check_default(__be32 gw, struct net_device *dev)
 332{
 333        struct hlist_head *head;
 334        struct hlist_node *node;
 335        struct fib_nh *nh;
 336        unsigned int hash;
 337
 338        spin_lock(&fib_info_lock);
 339
 340        hash = fib_devindex_hashfn(dev->ifindex);
 341        head = &fib_info_devhash[hash];
 342        hlist_for_each_entry(nh, node, head, nh_hash) {
 343                if (nh->nh_dev == dev &&
 344                    nh->nh_gw == gw &&
 345                    !(nh->nh_flags & RTNH_F_DEAD)) {
 346                        spin_unlock(&fib_info_lock);
 347                        return 0;
 348                }
 349        }
 350
 351        spin_unlock(&fib_info_lock);
 352
 353        return -1;
 354}
 355
 356static inline size_t fib_nlmsg_size(struct fib_info *fi)
 357{
 358        size_t payload = NLMSG_ALIGN(sizeof(struct rtmsg))
 359                         + nla_total_size(4) /* RTA_TABLE */
 360                         + nla_total_size(4) /* RTA_DST */
 361                         + nla_total_size(4) /* RTA_PRIORITY */
 362                         + nla_total_size(4); /* RTA_PREFSRC */
 363
 364        /* space for nested metrics */
 365        payload += nla_total_size((RTAX_MAX * nla_total_size(4)));
 366
 367        if (fi->fib_nhs) {
 368                /* Also handles the special case fib_nhs == 1 */
 369
 370                /* each nexthop is packed in an attribute */
 371                size_t nhsize = nla_total_size(sizeof(struct rtnexthop));
 372
 373                /* may contain flow and gateway attribute */
 374                nhsize += 2 * nla_total_size(4);
 375
 376                /* all nexthops are packed in a nested attribute */
 377                payload += nla_total_size(fi->fib_nhs * nhsize);
 378        }
 379
 380        return payload;
 381}
 382
 383void rtmsg_fib(int event, __be32 key, struct fib_alias *fa,
 384               int dst_len, u32 tb_id, struct nl_info *info,
 385               unsigned int nlm_flags)
 386{
 387        struct sk_buff *skb;
 388        u32 seq = info->nlh ? info->nlh->nlmsg_seq : 0;
 389        int err = -ENOBUFS;
 390
 391        skb = nlmsg_new(fib_nlmsg_size(fa->fa_info), GFP_KERNEL);
 392        if (skb == NULL)
 393                goto errout;
 394
 395        err = fib_dump_info(skb, info->portid, seq, event, tb_id,
 396                            fa->fa_type, key, dst_len,
 397                            fa->fa_tos, fa->fa_info, nlm_flags);
 398        if (err < 0) {
 399                /* -EMSGSIZE implies BUG in fib_nlmsg_size() */
 400                WARN_ON(err == -EMSGSIZE);
 401                kfree_skb(skb);
 402                goto errout;
 403        }
 404        rtnl_notify(skb, info->nl_net, info->portid, RTNLGRP_IPV4_ROUTE,
 405                    info->nlh, GFP_KERNEL);
 406        return;
 407errout:
 408        if (err < 0)
 409                rtnl_set_sk_err(info->nl_net, RTNLGRP_IPV4_ROUTE, err);
 410}
 411
 412/* Return the first fib alias matching TOS with
 413 * priority less than or equal to PRIO.
 414 */
 415struct fib_alias *fib_find_alias(struct list_head *fah, u8 tos, u32 prio)
 416{
 417        if (fah) {
 418                struct fib_alias *fa;
 419                list_for_each_entry(fa, fah, fa_list) {
 420                        if (fa->fa_tos > tos)
 421                                continue;
 422                        if (fa->fa_info->fib_priority >= prio ||
 423                            fa->fa_tos < tos)
 424                                return fa;
 425                }
 426        }
 427        return NULL;
 428}
 429
 430int fib_detect_death(struct fib_info *fi, int order,
 431                     struct fib_info **last_resort, int *last_idx, 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
 455static 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
 468static 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
 504int 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 */
 601static 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                        };
 635
 636                        /* It is not necessary, but requires a bit of thinking */
 637                        if (fl4.flowi4_scope < RT_SCOPE_LINK)
 638                                fl4.flowi4_scope = RT_SCOPE_LINK;
 639                        err = fib_lookup(net, &fl4, &res);
 640                        if (err) {
 641                                rcu_read_unlock();
 642                                return err;
 643                        }
 644                }
 645                err = -EINVAL;
 646                if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
 647                        goto out;
 648                nh->nh_scope = res.scope;
 649                nh->nh_oif = FIB_RES_OIF(res);
 650                nh->nh_dev = dev = FIB_RES_DEV(res);
 651                if (!dev)
 652                        goto out;
 653                dev_hold(dev);
 654                err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
 655        } else {
 656                struct in_device *in_dev;
 657
 658                if (nh->nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK))
 659                        return -EINVAL;
 660
 661                rcu_read_lock();
 662                err = -ENODEV;
 663                in_dev = inetdev_by_index(net, nh->nh_oif);
 664                if (in_dev == NULL)
 665                        goto out;
 666                err = -ENETDOWN;
 667                if (!(in_dev->dev->flags & IFF_UP))
 668                        goto out;
 669                nh->nh_dev = in_dev->dev;
 670                dev_hold(nh->nh_dev);
 671                nh->nh_scope = RT_SCOPE_HOST;
 672                err = 0;
 673        }
 674out:
 675        rcu_read_unlock();
 676        return err;
 677}
 678
 679static inline unsigned int fib_laddr_hashfn(__be32 val)
 680{
 681        unsigned int mask = (fib_info_hash_size - 1);
 682
 683        return ((__force u32)val ^
 684                ((__force u32)val >> 7) ^
 685                ((__force u32)val >> 14)) & mask;
 686}
 687
 688static struct hlist_head *fib_info_hash_alloc(int bytes)
 689{
 690        if (bytes <= PAGE_SIZE)
 691                return kzalloc(bytes, GFP_KERNEL);
 692        else
 693                return (struct hlist_head *)
 694                        __get_free_pages(GFP_KERNEL | __GFP_ZERO,
 695                                         get_order(bytes));
 696}
 697
 698static void fib_info_hash_free(struct hlist_head *hash, int bytes)
 699{
 700        if (!hash)
 701                return;
 702
 703        if (bytes <= PAGE_SIZE)
 704                kfree(hash);
 705        else
 706                free_pages((unsigned long) hash, get_order(bytes));
 707}
 708
 709static void fib_info_hash_move(struct hlist_head *new_info_hash,
 710                               struct hlist_head *new_laddrhash,
 711                               unsigned int new_size)
 712{
 713        struct hlist_head *old_info_hash, *old_laddrhash;
 714        unsigned int old_size = fib_info_hash_size;
 715        unsigned int i, bytes;
 716
 717        spin_lock_bh(&fib_info_lock);
 718        old_info_hash = fib_info_hash;
 719        old_laddrhash = fib_info_laddrhash;
 720        fib_info_hash_size = new_size;
 721
 722        for (i = 0; i < old_size; i++) {
 723                struct hlist_head *head = &fib_info_hash[i];
 724                struct hlist_node *node, *n;
 725                struct fib_info *fi;
 726
 727                hlist_for_each_entry_safe(fi, node, n, head, fib_hash) {
 728                        struct hlist_head *dest;
 729                        unsigned int new_hash;
 730
 731                        hlist_del(&fi->fib_hash);
 732
 733                        new_hash = fib_info_hashfn(fi);
 734                        dest = &new_info_hash[new_hash];
 735                        hlist_add_head(&fi->fib_hash, dest);
 736                }
 737        }
 738        fib_info_hash = new_info_hash;
 739
 740        for (i = 0; i < old_size; i++) {
 741                struct hlist_head *lhead = &fib_info_laddrhash[i];
 742                struct hlist_node *node, *n;
 743                struct fib_info *fi;
 744
 745                hlist_for_each_entry_safe(fi, node, n, lhead, fib_lhash) {
 746                        struct hlist_head *ldest;
 747                        unsigned int new_hash;
 748
 749                        hlist_del(&fi->fib_lhash);
 750
 751                        new_hash = fib_laddr_hashfn(fi->fib_prefsrc);
 752                        ldest = &new_laddrhash[new_hash];
 753                        hlist_add_head(&fi->fib_lhash, ldest);
 754                }
 755        }
 756        fib_info_laddrhash = new_laddrhash;
 757
 758        spin_unlock_bh(&fib_info_lock);
 759
 760        bytes = old_size * sizeof(struct hlist_head *);
 761        fib_info_hash_free(old_info_hash, bytes);
 762        fib_info_hash_free(old_laddrhash, bytes);
 763}
 764
 765__be32 fib_info_update_nh_saddr(struct net *net, struct fib_nh *nh)
 766{
 767        nh->nh_saddr = inet_select_addr(nh->nh_dev,
 768                                        nh->nh_gw,
 769                                        nh->nh_parent->fib_scope);
 770        nh->nh_saddr_genid = atomic_read(&net->ipv4.dev_addr_genid);
 771
 772        return nh->nh_saddr;
 773}
 774
 775struct fib_info *fib_create_info(struct fib_config *cfg)
 776{
 777        int err;
 778        struct fib_info *fi = NULL;
 779        struct fib_info *ofi;
 780        int nhs = 1;
 781        struct net *net = cfg->fc_nlinfo.nl_net;
 782
 783        if (cfg->fc_type > RTN_MAX)
 784                goto err_inval;
 785
 786        /* Fast check to catch the most weird cases */
 787        if (fib_props[cfg->fc_type].scope > cfg->fc_scope)
 788                goto err_inval;
 789
 790#ifdef CONFIG_IP_ROUTE_MULTIPATH
 791        if (cfg->fc_mp) {
 792                nhs = fib_count_nexthops(cfg->fc_mp, cfg->fc_mp_len);
 793                if (nhs == 0)
 794                        goto err_inval;
 795        }
 796#endif
 797
 798        err = -ENOBUFS;
 799        if (fib_info_cnt >= fib_info_hash_size) {
 800                unsigned int new_size = fib_info_hash_size << 1;
 801                struct hlist_head *new_info_hash;
 802                struct hlist_head *new_laddrhash;
 803                unsigned int bytes;
 804
 805                if (!new_size)
 806                        new_size = 1;
 807                bytes = new_size * sizeof(struct hlist_head *);
 808                new_info_hash = fib_info_hash_alloc(bytes);
 809                new_laddrhash = fib_info_hash_alloc(bytes);
 810                if (!new_info_hash || !new_laddrhash) {
 811                        fib_info_hash_free(new_info_hash, bytes);
 812                        fib_info_hash_free(new_laddrhash, bytes);
 813                } else
 814                        fib_info_hash_move(new_info_hash, new_laddrhash, new_size);
 815
 816                if (!fib_info_hash_size)
 817                        goto failure;
 818        }
 819
 820        fi = kzalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL);
 821        if (fi == NULL)
 822                goto failure;
 823        if (cfg->fc_mx) {
 824                fi->fib_metrics = kzalloc(sizeof(u32) * RTAX_MAX, GFP_KERNEL);
 825                if (!fi->fib_metrics)
 826                        goto failure;
 827        } else
 828                fi->fib_metrics = (u32 *) dst_default_metrics;
 829        fib_info_cnt++;
 830
 831        fi->fib_net = hold_net(net);
 832        fi->fib_protocol = cfg->fc_protocol;
 833        fi->fib_scope = cfg->fc_scope;
 834        fi->fib_flags = cfg->fc_flags;
 835        fi->fib_priority = cfg->fc_priority;
 836        fi->fib_prefsrc = cfg->fc_prefsrc;
 837        fi->fib_type = cfg->fc_type;
 838
 839        fi->fib_nhs = nhs;
 840        change_nexthops(fi) {
 841                nexthop_nh->nh_parent = fi;
 842                nexthop_nh->nh_pcpu_rth_output = alloc_percpu(struct rtable __rcu *);
 843                if (!nexthop_nh->nh_pcpu_rth_output)
 844                        goto failure;
 845        } endfor_nexthops(fi)
 846
 847        if (cfg->fc_mx) {
 848                struct nlattr *nla;
 849                int remaining;
 850
 851                nla_for_each_attr(nla, cfg->fc_mx, cfg->fc_mx_len, remaining) {
 852                        int type = nla_type(nla);
 853
 854                        if (type) {
 855                                u32 val;
 856
 857                                if (type > RTAX_MAX)
 858                                        goto err_inval;
 859                                val = nla_get_u32(nla);
 860                                if (type == RTAX_ADVMSS && val > 65535 - 40)
 861                                        val = 65535 - 40;
 862                                if (type == RTAX_MTU && val > 65535 - 15)
 863                                        val = 65535 - 15;
 864                                fi->fib_metrics[type - 1] = val;
 865                        }
 866                }
 867        }
 868
 869        if (cfg->fc_mp) {
 870#ifdef CONFIG_IP_ROUTE_MULTIPATH
 871                err = fib_get_nhs(fi, cfg->fc_mp, cfg->fc_mp_len, cfg);
 872                if (err != 0)
 873                        goto failure;
 874                if (cfg->fc_oif && fi->fib_nh->nh_oif != cfg->fc_oif)
 875                        goto err_inval;
 876                if (cfg->fc_gw && fi->fib_nh->nh_gw != cfg->fc_gw)
 877                        goto err_inval;
 878#ifdef CONFIG_IP_ROUTE_CLASSID
 879                if (cfg->fc_flow && fi->fib_nh->nh_tclassid != cfg->fc_flow)
 880                        goto err_inval;
 881#endif
 882#else
 883                goto err_inval;
 884#endif
 885        } else {
 886                struct fib_nh *nh = fi->fib_nh;
 887
 888                nh->nh_oif = cfg->fc_oif;
 889                nh->nh_gw = cfg->fc_gw;
 890                nh->nh_flags = cfg->fc_flags;
 891#ifdef CONFIG_IP_ROUTE_CLASSID
 892                nh->nh_tclassid = cfg->fc_flow;
 893                if (nh->nh_tclassid)
 894                        fi->fib_net->ipv4.fib_num_tclassid_users++;
 895#endif
 896#ifdef CONFIG_IP_ROUTE_MULTIPATH
 897                nh->nh_weight = 1;
 898#endif
 899        }
 900
 901        if (fib_props[cfg->fc_type].error) {
 902                if (cfg->fc_gw || cfg->fc_oif || cfg->fc_mp)
 903                        goto err_inval;
 904                goto link_it;
 905        } else {
 906                switch (cfg->fc_type) {
 907                case RTN_UNICAST:
 908                case RTN_LOCAL:
 909                case RTN_BROADCAST:
 910                case RTN_ANYCAST:
 911                case RTN_MULTICAST:
 912                        break;
 913                default:
 914                        goto err_inval;
 915                }
 916        }
 917
 918        if (cfg->fc_scope > RT_SCOPE_HOST)
 919                goto err_inval;
 920
 921        if (cfg->fc_scope == RT_SCOPE_HOST) {
 922                struct fib_nh *nh = fi->fib_nh;
 923
 924                /* Local address is added. */
 925                if (nhs != 1 || nh->nh_gw)
 926                        goto err_inval;
 927                nh->nh_scope = RT_SCOPE_NOWHERE;
 928                nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
 929                err = -ENODEV;
 930                if (nh->nh_dev == NULL)
 931                        goto failure;
 932        } else {
 933                change_nexthops(fi) {
 934                        err = fib_check_nh(cfg, fi, nexthop_nh);
 935                        if (err != 0)
 936                                goto failure;
 937                } endfor_nexthops(fi)
 938        }
 939
 940        if (fi->fib_prefsrc) {
 941                if (cfg->fc_type != RTN_LOCAL || !cfg->fc_dst ||
 942                    fi->fib_prefsrc != cfg->fc_dst)
 943                        if (inet_addr_type(net, fi->fib_prefsrc) != RTN_LOCAL)
 944                                goto err_inval;
 945        }
 946
 947        change_nexthops(fi) {
 948                fib_info_update_nh_saddr(net, nexthop_nh);
 949        } endfor_nexthops(fi)
 950
 951link_it:
 952        ofi = fib_find_info(fi);
 953        if (ofi) {
 954                fi->fib_dead = 1;
 955                free_fib_info(fi);
 956                ofi->fib_treeref++;
 957                return ofi;
 958        }
 959
 960        fi->fib_treeref++;
 961        atomic_inc(&fi->fib_clntref);
 962        spin_lock_bh(&fib_info_lock);
 963        hlist_add_head(&fi->fib_hash,
 964                       &fib_info_hash[fib_info_hashfn(fi)]);
 965        if (fi->fib_prefsrc) {
 966                struct hlist_head *head;
 967
 968                head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)];
 969                hlist_add_head(&fi->fib_lhash, head);
 970        }
 971        change_nexthops(fi) {
 972                struct hlist_head *head;
 973                unsigned int hash;
 974
 975                if (!nexthop_nh->nh_dev)
 976                        continue;
 977                hash = fib_devindex_hashfn(nexthop_nh->nh_dev->ifindex);
 978                head = &fib_info_devhash[hash];
 979                hlist_add_head(&nexthop_nh->nh_hash, head);
 980        } endfor_nexthops(fi)
 981        spin_unlock_bh(&fib_info_lock);
 982        return fi;
 983
 984err_inval:
 985        err = -EINVAL;
 986
 987failure:
 988        if (fi) {
 989                fi->fib_dead = 1;
 990                free_fib_info(fi);
 991        }
 992
 993        return ERR_PTR(err);
 994}
 995
 996int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event,
 997                  u32 tb_id, u8 type, __be32 dst, int dst_len, u8 tos,
 998                  struct fib_info *fi, unsigned int flags)
 999{
1000        struct nlmsghdr *nlh;
1001        struct rtmsg *rtm;
1002
1003        nlh = nlmsg_put(skb, portid, seq, event, sizeof(*rtm), flags);
1004        if (nlh == NULL)
1005                return -EMSGSIZE;
1006
1007        rtm = nlmsg_data(nlh);
1008        rtm->rtm_family = AF_INET;
1009        rtm->rtm_dst_len = dst_len;
1010        rtm->rtm_src_len = 0;
1011        rtm->rtm_tos = tos;
1012        if (tb_id < 256)
1013                rtm->rtm_table = tb_id;
1014        else
1015                rtm->rtm_table = RT_TABLE_COMPAT;
1016        if (nla_put_u32(skb, RTA_TABLE, tb_id))
1017                goto nla_put_failure;
1018        rtm->rtm_type = type;
1019        rtm->rtm_flags = fi->fib_flags;
1020        rtm->rtm_scope = fi->fib_scope;
1021        rtm->rtm_protocol = fi->fib_protocol;
1022
1023        if (rtm->rtm_dst_len &&
1024            nla_put_be32(skb, RTA_DST, dst))
1025                goto nla_put_failure;
1026        if (fi->fib_priority &&
1027            nla_put_u32(skb, RTA_PRIORITY, fi->fib_priority))
1028                goto nla_put_failure;
1029        if (rtnetlink_put_metrics(skb, fi->fib_metrics) < 0)
1030                goto nla_put_failure;
1031
1032        if (fi->fib_prefsrc &&
1033            nla_put_be32(skb, RTA_PREFSRC, fi->fib_prefsrc))
1034                goto nla_put_failure;
1035        if (fi->fib_nhs == 1) {
1036                if (fi->fib_nh->nh_gw &&
1037                    nla_put_be32(skb, RTA_GATEWAY, fi->fib_nh->nh_gw))
1038                        goto nla_put_failure;
1039                if (fi->fib_nh->nh_oif &&
1040                    nla_put_u32(skb, RTA_OIF, fi->fib_nh->nh_oif))
1041                        goto nla_put_failure;
1042#ifdef CONFIG_IP_ROUTE_CLASSID
1043                if (fi->fib_nh[0].nh_tclassid &&
1044                    nla_put_u32(skb, RTA_FLOW, fi->fib_nh[0].nh_tclassid))
1045                        goto nla_put_failure;
1046#endif
1047        }
1048#ifdef CONFIG_IP_ROUTE_MULTIPATH
1049        if (fi->fib_nhs > 1) {
1050                struct rtnexthop *rtnh;
1051                struct nlattr *mp;
1052
1053                mp = nla_nest_start(skb, RTA_MULTIPATH);
1054                if (mp == NULL)
1055                        goto nla_put_failure;
1056
1057                for_nexthops(fi) {
1058                        rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));
1059                        if (rtnh == NULL)
1060                                goto nla_put_failure;
1061
1062                        rtnh->rtnh_flags = nh->nh_flags & 0xFF;
1063                        rtnh->rtnh_hops = nh->nh_weight - 1;
1064                        rtnh->rtnh_ifindex = nh->nh_oif;
1065
1066                        if (nh->nh_gw &&
1067                            nla_put_be32(skb, RTA_GATEWAY, nh->nh_gw))
1068                                goto nla_put_failure;
1069#ifdef CONFIG_IP_ROUTE_CLASSID
1070                        if (nh->nh_tclassid &&
1071                            nla_put_u32(skb, RTA_FLOW, nh->nh_tclassid))
1072                                goto nla_put_failure;
1073#endif
1074                        /* length of rtnetlink header + attributes */
1075                        rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *) rtnh;
1076                } endfor_nexthops(fi);
1077
1078                nla_nest_end(skb, mp);
1079        }
1080#endif
1081        return nlmsg_end(skb, nlh);
1082
1083nla_put_failure:
1084        nlmsg_cancel(skb, nlh);
1085        return -EMSGSIZE;
1086}
1087
1088/*
1089 * Update FIB if:
1090 * - local address disappeared -> we must delete all the entries
1091 *   referring to it.
1092 * - device went down -> we must shutdown all nexthops going via it.
1093 */
1094int fib_sync_down_addr(struct net *net, __be32 local)
1095{
1096        int ret = 0;
1097        unsigned int hash = fib_laddr_hashfn(local);
1098        struct hlist_head *head = &fib_info_laddrhash[hash];
1099        struct hlist_node *node;
1100        struct fib_info *fi;
1101
1102        if (fib_info_laddrhash == NULL || local == 0)
1103                return 0;
1104
1105        hlist_for_each_entry(fi, node, 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
1116int 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 hlist_node *node;
1124        struct fib_nh *nh;
1125
1126        if (force)
1127                scope = -1;
1128
1129        hlist_for_each_entry(nh, node, head, nh_hash) {
1130                struct fib_info *fi = nh->nh_parent;
1131                int dead;
1132
1133                BUG_ON(!fi->fib_nhs);
1134                if (nh->nh_dev != dev || fi == prev_fi)
1135                        continue;
1136                prev_fi = fi;
1137                dead = 0;
1138                change_nexthops(fi) {
1139                        if (nexthop_nh->nh_flags & RTNH_F_DEAD)
1140                                dead++;
1141                        else if (nexthop_nh->nh_dev == dev &&
1142                                 nexthop_nh->nh_scope != scope) {
1143                                nexthop_nh->nh_flags |= RTNH_F_DEAD;
1144#ifdef CONFIG_IP_ROUTE_MULTIPATH
1145                                spin_lock_bh(&fib_multipath_lock);
1146                                fi->fib_power -= nexthop_nh->nh_power;
1147                                nexthop_nh->nh_power = 0;
1148                                spin_unlock_bh(&fib_multipath_lock);
1149#endif
1150                                dead++;
1151                        }
1152#ifdef CONFIG_IP_ROUTE_MULTIPATH
1153                        if (force > 1 && nexthop_nh->nh_dev == dev) {
1154                                dead = fi->fib_nhs;
1155                                break;
1156                        }
1157#endif
1158                } endfor_nexthops(fi)
1159                if (dead == fi->fib_nhs) {
1160                        fi->fib_flags |= RTNH_F_DEAD;
1161                        ret++;
1162                }
1163        }
1164
1165        return ret;
1166}
1167
1168/* Must be invoked inside of an RCU protected region.  */
1169void fib_select_default(struct fib_result *res)
1170{
1171        struct fib_info *fi = NULL, *last_resort = NULL;
1172        struct list_head *fa_head = res->fa_head;
1173        struct fib_table *tb = res->table;
1174        int order = -1, last_idx = -1;
1175        struct fib_alias *fa;
1176
1177        list_for_each_entry_rcu(fa, fa_head, fa_list) {
1178                struct fib_info *next_fi = fa->fa_info;
1179
1180                if (next_fi->fib_scope != res->scope ||
1181                    fa->fa_type != RTN_UNICAST)
1182                        continue;
1183
1184                if (next_fi->fib_priority > res->fi->fib_priority)
1185                        break;
1186                if (!next_fi->fib_nh[0].nh_gw ||
1187                    next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
1188                        continue;
1189
1190                fib_alias_accessed(fa);
1191
1192                if (fi == NULL) {
1193                        if (next_fi != res->fi)
1194                                break;
1195                } else if (!fib_detect_death(fi, order, &last_resort,
1196                                             &last_idx, tb->tb_default)) {
1197                        fib_result_assign(res, fi);
1198                        tb->tb_default = order;
1199                        goto out;
1200                }
1201                fi = next_fi;
1202                order++;
1203        }
1204
1205        if (order <= 0 || fi == NULL) {
1206                tb->tb_default = -1;
1207                goto out;
1208        }
1209
1210        if (!fib_detect_death(fi, order, &last_resort, &last_idx,
1211                                tb->tb_default)) {
1212                fib_result_assign(res, fi);
1213                tb->tb_default = order;
1214                goto out;
1215        }
1216
1217        if (last_idx >= 0)
1218                fib_result_assign(res, last_resort);
1219        tb->tb_default = last_idx;
1220out:
1221        return;
1222}
1223
1224#ifdef CONFIG_IP_ROUTE_MULTIPATH
1225
1226/*
1227 * Dead device goes up. We wake up dead nexthops.
1228 * It takes sense only on multipath routes.
1229 */
1230int fib_sync_up(struct net_device *dev)
1231{
1232        struct fib_info *prev_fi;
1233        unsigned int hash;
1234        struct hlist_head *head;
1235        struct hlist_node *node;
1236        struct fib_nh *nh;
1237        int ret;
1238
1239        if (!(dev->flags & IFF_UP))
1240                return 0;
1241
1242        prev_fi = NULL;
1243        hash = fib_devindex_hashfn(dev->ifindex);
1244        head = &fib_info_devhash[hash];
1245        ret = 0;
1246
1247        hlist_for_each_entry(nh, node, head, nh_hash) {
1248                struct fib_info *fi = nh->nh_parent;
1249                int alive;
1250
1251                BUG_ON(!fi->fib_nhs);
1252                if (nh->nh_dev != dev || fi == prev_fi)
1253                        continue;
1254
1255                prev_fi = fi;
1256                alive = 0;
1257                change_nexthops(fi) {
1258                        if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1259                                alive++;
1260                                continue;
1261                        }
1262                        if (nexthop_nh->nh_dev == NULL ||
1263                            !(nexthop_nh->nh_dev->flags & IFF_UP))
1264                                continue;
1265                        if (nexthop_nh->nh_dev != dev ||
1266                            !__in_dev_get_rtnl(dev))
1267                                continue;
1268                        alive++;
1269                        spin_lock_bh(&fib_multipath_lock);
1270                        nexthop_nh->nh_power = 0;
1271                        nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
1272                        spin_unlock_bh(&fib_multipath_lock);
1273                } endfor_nexthops(fi)
1274
1275                if (alive > 0) {
1276                        fi->fib_flags &= ~RTNH_F_DEAD;
1277                        ret++;
1278                }
1279        }
1280
1281        return ret;
1282}
1283
1284/*
1285 * The algorithm is suboptimal, but it provides really
1286 * fair weighted route distribution.
1287 */
1288void fib_select_multipath(struct fib_result *res)
1289{
1290        struct fib_info *fi = res->fi;
1291        int w;
1292
1293        spin_lock_bh(&fib_multipath_lock);
1294        if (fi->fib_power <= 0) {
1295                int power = 0;
1296                change_nexthops(fi) {
1297                        if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1298                                power += nexthop_nh->nh_weight;
1299                                nexthop_nh->nh_power = nexthop_nh->nh_weight;
1300                        }
1301                } endfor_nexthops(fi);
1302                fi->fib_power = power;
1303                if (power <= 0) {
1304                        spin_unlock_bh(&fib_multipath_lock);
1305                        /* Race condition: route has just become dead. */
1306                        res->nh_sel = 0;
1307                        return;
1308                }
1309        }
1310
1311
1312        /* w should be random number [0..fi->fib_power-1],
1313         * it is pretty bad approximation.
1314         */
1315
1316        w = jiffies % fi->fib_power;
1317
1318        change_nexthops(fi) {
1319                if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
1320                    nexthop_nh->nh_power) {
1321                        w -= nexthop_nh->nh_power;
1322                        if (w <= 0) {
1323                                nexthop_nh->nh_power--;
1324                                fi->fib_power--;
1325                                res->nh_sel = nhsel;
1326                                spin_unlock_bh(&fib_multipath_lock);
1327                                return;
1328                        }
1329                }
1330        } endfor_nexthops(fi);
1331
1332        /* Race condition: route has just become dead. */
1333        res->nh_sel = 0;
1334        spin_unlock_bh(&fib_multipath_lock);
1335}
1336#endif
1337
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