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

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