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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 static int fib_detect_death(struct fib_info *fi, int order,
430                             struct fib_info **last_resort, int *last_idx,
431                             int dflt)
432 {
433         struct neighbour *n;
434         int state = NUD_NONE;
435 
436         n = neigh_lookup(&arp_tbl, &fi->fib_nh[0].nh_gw, fi->fib_dev);
437         if (n) {
438                 state = n->nud_state;
439                 neigh_release(n);
440         }
441         if (state == NUD_REACHABLE)
442                 return 0;
443         if ((state & NUD_VALID) && order != dflt)
444                 return 0;
445         if ((state & NUD_VALID) ||
446             (*last_idx < 0 && order > dflt)) {
447                 *last_resort = fi;
448                 *last_idx = order;
449         }
450         return 1;
451 }
452 
453 #ifdef CONFIG_IP_ROUTE_MULTIPATH
454 
455 static int fib_count_nexthops(struct rtnexthop *rtnh, int remaining)
456 {
457         int nhs = 0;
458 
459         while (rtnh_ok(rtnh, remaining)) {
460                 nhs++;
461                 rtnh = rtnh_next(rtnh, &remaining);
462         }
463 
464         /* leftover implies invalid nexthop configuration, discard it */
465         return remaining > 0 ? 0 : nhs;
466 }
467 
468 static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
469                        int remaining, struct fib_config *cfg)
470 {
471         change_nexthops(fi) {
472                 int attrlen;
473 
474                 if (!rtnh_ok(rtnh, remaining))
475                         return -EINVAL;
476 
477                 nexthop_nh->nh_flags =
478                         (cfg->fc_flags & ~0xFF) | rtnh->rtnh_flags;
479                 nexthop_nh->nh_oif = rtnh->rtnh_ifindex;
480                 nexthop_nh->nh_weight = rtnh->rtnh_hops + 1;
481 
482                 attrlen = rtnh_attrlen(rtnh);
483                 if (attrlen > 0) {
484                         struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
485 
486                         nla = nla_find(attrs, attrlen, RTA_GATEWAY);
487                         nexthop_nh->nh_gw = nla ? nla_get_be32(nla) : 0;
488 #ifdef CONFIG_IP_ROUTE_CLASSID
489                         nla = nla_find(attrs, attrlen, RTA_FLOW);
490                         nexthop_nh->nh_tclassid = nla ? nla_get_u32(nla) : 0;
491                         if (nexthop_nh->nh_tclassid)
492                                 fi->fib_net->ipv4.fib_num_tclassid_users++;
493 #endif
494                 }
495 
496                 rtnh = rtnh_next(rtnh, &remaining);
497         } endfor_nexthops(fi);
498 
499         return 0;
500 }
501 
502 #endif
503 
504 int fib_nh_match(struct fib_config *cfg, struct fib_info *fi)
505 {
506 #ifdef CONFIG_IP_ROUTE_MULTIPATH
507         struct rtnexthop *rtnh;
508         int remaining;
509 #endif
510 
511         if (cfg->fc_priority && cfg->fc_priority != fi->fib_priority)
512                 return 1;
513 
514         if (cfg->fc_oif || cfg->fc_gw) {
515                 if ((!cfg->fc_oif || cfg->fc_oif == fi->fib_nh->nh_oif) &&
516                     (!cfg->fc_gw  || cfg->fc_gw == fi->fib_nh->nh_gw))
517                         return 0;
518                 return 1;
519         }
520 
521 #ifdef CONFIG_IP_ROUTE_MULTIPATH
522         if (cfg->fc_mp == NULL)
523                 return 0;
524 
525         rtnh = cfg->fc_mp;
526         remaining = cfg->fc_mp_len;
527 
528         for_nexthops(fi) {
529                 int attrlen;
530 
531                 if (!rtnh_ok(rtnh, remaining))
532                         return -EINVAL;
533 
534                 if (rtnh->rtnh_ifindex && rtnh->rtnh_ifindex != nh->nh_oif)
535                         return 1;
536 
537                 attrlen = rtnh_attrlen(rtnh);
538                 if (attrlen > 0) {
539                         struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
540 
541                         nla = nla_find(attrs, attrlen, RTA_GATEWAY);
542                         if (nla && nla_get_be32(nla) != nh->nh_gw)
543                                 return 1;
544 #ifdef CONFIG_IP_ROUTE_CLASSID
545                         nla = nla_find(attrs, attrlen, RTA_FLOW);
546                         if (nla && nla_get_u32(nla) != nh->nh_tclassid)
547                                 return 1;
548 #endif
549                 }
550 
551                 rtnh = rtnh_next(rtnh, &remaining);
552         } endfor_nexthops(fi);
553 #endif
554         return 0;
555 }
556 
557 
558 /*
559  * Picture
560  * -------
561  *
562  * Semantics of nexthop is very messy by historical reasons.
563  * We have to take into account, that:
564  * a) gateway can be actually local interface address,
565  *    so that gatewayed route is direct.
566  * b) gateway must be on-link address, possibly
567  *    described not by an ifaddr, but also by a direct route.
568  * c) If both gateway and interface are specified, they should not
569  *    contradict.
570  * d) If we use tunnel routes, gateway could be not on-link.
571  *
572  * Attempt to reconcile all of these (alas, self-contradictory) conditions
573  * results in pretty ugly and hairy code with obscure logic.
574  *
575  * I chose to generalized it instead, so that the size
576  * of code does not increase practically, but it becomes
577  * much more general.
578  * Every prefix is assigned a "scope" value: "host" is local address,
579  * "link" is direct route,
580  * [ ... "site" ... "interior" ... ]
581  * and "universe" is true gateway route with global meaning.
582  *
583  * Every prefix refers to a set of "nexthop"s (gw, oif),
584  * where gw must have narrower scope. This recursion stops
585  * when gw has LOCAL scope or if "nexthop" is declared ONLINK,
586  * which means that gw is forced to be on link.
587  *
588  * Code is still hairy, but now it is apparently logically
589  * consistent and very flexible. F.e. as by-product it allows
590  * to co-exists in peace independent exterior and interior
591  * routing processes.
592  *
593  * Normally it looks as following.
594  *
595  * {universe prefix}  -> (gw, oif) [scope link]
596  *                |
597  *                |-> {link prefix} -> (gw, oif) [scope local]
598  *                                      |
599  *                                      |-> {local prefix} (terminal node)
600  */
601 static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
602                         struct fib_nh *nh)
603 {
604         int err;
605         struct net *net;
606         struct net_device *dev;
607 
608         net = cfg->fc_nlinfo.nl_net;
609         if (nh->nh_gw) {
610                 struct fib_result res;
611 
612                 if (nh->nh_flags & RTNH_F_ONLINK) {
613 
614                         if (cfg->fc_scope >= RT_SCOPE_LINK)
615                                 return -EINVAL;
616                         if (inet_addr_type(net, nh->nh_gw) != RTN_UNICAST)
617                                 return -EINVAL;
618                         dev = __dev_get_by_index(net, nh->nh_oif);
619                         if (!dev)
620                                 return -ENODEV;
621                         if (!(dev->flags & IFF_UP))
622                                 return -ENETDOWN;
623                         nh->nh_dev = dev;
624                         dev_hold(dev);
625                         nh->nh_scope = RT_SCOPE_LINK;
626                         return 0;
627                 }
628                 rcu_read_lock();
629                 {
630                         struct flowi4 fl4 = {
631                                 .daddr = nh->nh_gw,
632                                 .flowi4_scope = cfg->fc_scope + 1,
633                                 .flowi4_oif = nh->nh_oif,
634                                 .flowi4_iif = LOOPBACK_IFINDEX,
635                         };
636 
637                         /* It is not necessary, but requires a bit of thinking */
638                         if (fl4.flowi4_scope < RT_SCOPE_LINK)
639                                 fl4.flowi4_scope = RT_SCOPE_LINK;
640                         err = fib_lookup(net, &fl4, &res);
641                         if (err) {
642                                 rcu_read_unlock();
643                                 return err;
644                         }
645                 }
646                 err = -EINVAL;
647                 if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
648                         goto out;
649                 nh->nh_scope = res.scope;
650                 nh->nh_oif = FIB_RES_OIF(res);
651                 nh->nh_dev = dev = FIB_RES_DEV(res);
652                 if (!dev)
653                         goto out;
654                 dev_hold(dev);
655                 err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
656         } else {
657                 struct in_device *in_dev;
658 
659                 if (nh->nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK))
660                         return -EINVAL;
661 
662                 rcu_read_lock();
663                 err = -ENODEV;
664                 in_dev = inetdev_by_index(net, nh->nh_oif);
665                 if (in_dev == NULL)
666                         goto out;
667                 err = -ENETDOWN;
668                 if (!(in_dev->dev->flags & IFF_UP))
669                         goto out;
670                 nh->nh_dev = in_dev->dev;
671                 dev_hold(nh->nh_dev);
672                 nh->nh_scope = RT_SCOPE_HOST;
673                 err = 0;
674         }
675 out:
676         rcu_read_unlock();
677         return err;
678 }
679 
680 static inline unsigned int fib_laddr_hashfn(__be32 val)
681 {
682         unsigned int mask = (fib_info_hash_size - 1);
683 
684         return ((__force u32)val ^
685                 ((__force u32)val >> 7) ^
686                 ((__force u32)val >> 14)) & mask;
687 }
688 
689 static struct hlist_head *fib_info_hash_alloc(int bytes)
690 {
691         if (bytes <= PAGE_SIZE)
692                 return kzalloc(bytes, GFP_KERNEL);
693         else
694                 return (struct hlist_head *)
695                         __get_free_pages(GFP_KERNEL | __GFP_ZERO,
696                                          get_order(bytes));
697 }
698 
699 static void fib_info_hash_free(struct hlist_head *hash, int bytes)
700 {
701         if (!hash)
702                 return;
703 
704         if (bytes <= PAGE_SIZE)
705                 kfree(hash);
706         else
707                 free_pages((unsigned long) hash, get_order(bytes));
708 }
709 
710 static void fib_info_hash_move(struct hlist_head *new_info_hash,
711                                struct hlist_head *new_laddrhash,
712                                unsigned int new_size)
713 {
714         struct hlist_head *old_info_hash, *old_laddrhash;
715         unsigned int old_size = fib_info_hash_size;
716         unsigned int i, bytes;
717 
718         spin_lock_bh(&fib_info_lock);
719         old_info_hash = fib_info_hash;
720         old_laddrhash = fib_info_laddrhash;
721         fib_info_hash_size = new_size;
722 
723         for (i = 0; i < old_size; i++) {
724                 struct hlist_head *head = &fib_info_hash[i];
725                 struct hlist_node *n;
726                 struct fib_info *fi;
727 
728                 hlist_for_each_entry_safe(fi, n, head, fib_hash) {
729                         struct hlist_head *dest;
730                         unsigned int new_hash;
731 
732                         hlist_del(&fi->fib_hash);
733 
734                         new_hash = fib_info_hashfn(fi);
735                         dest = &new_info_hash[new_hash];
736                         hlist_add_head(&fi->fib_hash, dest);
737                 }
738         }
739         fib_info_hash = new_info_hash;
740 
741         for (i = 0; i < old_size; i++) {
742                 struct hlist_head *lhead = &fib_info_laddrhash[i];
743                 struct hlist_node *n;
744                 struct fib_info *fi;
745 
746                 hlist_for_each_entry_safe(fi, n, lhead, fib_lhash) {
747                         struct hlist_head *ldest;
748                         unsigned int new_hash;
749 
750                         hlist_del(&fi->fib_lhash);
751 
752                         new_hash = fib_laddr_hashfn(fi->fib_prefsrc);
753                         ldest = &new_laddrhash[new_hash];
754                         hlist_add_head(&fi->fib_lhash, ldest);
755                 }
756         }
757         fib_info_laddrhash = new_laddrhash;
758 
759         spin_unlock_bh(&fib_info_lock);
760 
761         bytes = old_size * sizeof(struct hlist_head *);
762         fib_info_hash_free(old_info_hash, bytes);
763         fib_info_hash_free(old_laddrhash, bytes);
764 }
765 
766 __be32 fib_info_update_nh_saddr(struct net *net, struct fib_nh *nh)
767 {
768         nh->nh_saddr = inet_select_addr(nh->nh_dev,
769                                         nh->nh_gw,
770                                         nh->nh_parent->fib_scope);
771         nh->nh_saddr_genid = atomic_read(&net->ipv4.dev_addr_genid);
772 
773         return nh->nh_saddr;
774 }
775 
776 struct fib_info *fib_create_info(struct fib_config *cfg)
777 {
778         int err;
779         struct fib_info *fi = NULL;
780         struct fib_info *ofi;
781         int nhs = 1;
782         struct net *net = cfg->fc_nlinfo.nl_net;
783 
784         if (cfg->fc_type > RTN_MAX)
785                 goto err_inval;
786 
787         /* Fast check to catch the most weird cases */
788         if (fib_props[cfg->fc_type].scope > cfg->fc_scope)
789                 goto err_inval;
790 
791 #ifdef CONFIG_IP_ROUTE_MULTIPATH
792         if (cfg->fc_mp) {
793                 nhs = fib_count_nexthops(cfg->fc_mp, cfg->fc_mp_len);
794                 if (nhs == 0)
795                         goto err_inval;
796         }
797 #endif
798 
799         err = -ENOBUFS;
800         if (fib_info_cnt >= fib_info_hash_size) {
801                 unsigned int new_size = fib_info_hash_size << 1;
802                 struct hlist_head *new_info_hash;
803                 struct hlist_head *new_laddrhash;
804                 unsigned int bytes;
805 
806                 if (!new_size)
807                         new_size = 16;
808                 bytes = new_size * sizeof(struct hlist_head *);
809                 new_info_hash = fib_info_hash_alloc(bytes);
810                 new_laddrhash = fib_info_hash_alloc(bytes);
811                 if (!new_info_hash || !new_laddrhash) {
812                         fib_info_hash_free(new_info_hash, bytes);
813                         fib_info_hash_free(new_laddrhash, bytes);
814                 } else
815                         fib_info_hash_move(new_info_hash, new_laddrhash, new_size);
816 
817                 if (!fib_info_hash_size)
818                         goto failure;
819         }
820 
821         fi = kzalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL);
822         if (fi == NULL)
823                 goto failure;
824         fib_info_cnt++;
825         if (cfg->fc_mx) {
826                 fi->fib_metrics = kzalloc(sizeof(u32) * RTAX_MAX, GFP_KERNEL);
827                 if (!fi->fib_metrics)
828                         goto failure;
829         } else
830                 fi->fib_metrics = (u32 *) dst_default_metrics;
831 
832         fi->fib_net = hold_net(net);
833         fi->fib_protocol = cfg->fc_protocol;
834         fi->fib_scope = cfg->fc_scope;
835         fi->fib_flags = cfg->fc_flags;
836         fi->fib_priority = cfg->fc_priority;
837         fi->fib_prefsrc = cfg->fc_prefsrc;
838         fi->fib_type = cfg->fc_type;
839 
840         fi->fib_nhs = nhs;
841         change_nexthops(fi) {
842                 nexthop_nh->nh_parent = fi;
843                 nexthop_nh->nh_pcpu_rth_output = alloc_percpu(struct rtable __rcu *);
844                 if (!nexthop_nh->nh_pcpu_rth_output)
845                         goto failure;
846         } endfor_nexthops(fi)
847 
848         if (cfg->fc_mx) {
849                 struct nlattr *nla;
850                 int remaining;
851 
852                 nla_for_each_attr(nla, cfg->fc_mx, cfg->fc_mx_len, remaining) {
853                         int type = nla_type(nla);
854 
855                         if (type) {
856                                 u32 val;
857 
858                                 if (type > RTAX_MAX)
859                                         goto err_inval;
860                                 val = nla_get_u32(nla);
861                                 if (type == RTAX_ADVMSS && val > 65535 - 40)
862                                         val = 65535 - 40;
863                                 if (type == RTAX_MTU && val > 65535 - 15)
864                                         val = 65535 - 15;
865                                 fi->fib_metrics[type - 1] = val;
866                         }
867                 }
868         }
869 
870         if (cfg->fc_mp) {
871 #ifdef CONFIG_IP_ROUTE_MULTIPATH
872                 err = fib_get_nhs(fi, cfg->fc_mp, cfg->fc_mp_len, cfg);
873                 if (err != 0)
874                         goto failure;
875                 if (cfg->fc_oif && fi->fib_nh->nh_oif != cfg->fc_oif)
876                         goto err_inval;
877                 if (cfg->fc_gw && fi->fib_nh->nh_gw != cfg->fc_gw)
878                         goto err_inval;
879 #ifdef CONFIG_IP_ROUTE_CLASSID
880                 if (cfg->fc_flow && fi->fib_nh->nh_tclassid != cfg->fc_flow)
881                         goto err_inval;
882 #endif
883 #else
884                 goto err_inval;
885 #endif
886         } else {
887                 struct fib_nh *nh = fi->fib_nh;
888 
889                 nh->nh_oif = cfg->fc_oif;
890                 nh->nh_gw = cfg->fc_gw;
891                 nh->nh_flags = cfg->fc_flags;
892 #ifdef CONFIG_IP_ROUTE_CLASSID
893                 nh->nh_tclassid = cfg->fc_flow;
894                 if (nh->nh_tclassid)
895                         fi->fib_net->ipv4.fib_num_tclassid_users++;
896 #endif
897 #ifdef CONFIG_IP_ROUTE_MULTIPATH
898                 nh->nh_weight = 1;
899 #endif
900         }
901 
902         if (fib_props[cfg->fc_type].error) {
903                 if (cfg->fc_gw || cfg->fc_oif || cfg->fc_mp)
904                         goto err_inval;
905                 goto link_it;
906         } else {
907                 switch (cfg->fc_type) {
908                 case RTN_UNICAST:
909                 case RTN_LOCAL:
910                 case RTN_BROADCAST:
911                 case RTN_ANYCAST:
912                 case RTN_MULTICAST:
913                         break;
914                 default:
915                         goto err_inval;
916                 }
917         }
918 
919         if (cfg->fc_scope > RT_SCOPE_HOST)
920                 goto err_inval;
921 
922         if (cfg->fc_scope == RT_SCOPE_HOST) {
923                 struct fib_nh *nh = fi->fib_nh;
924 
925                 /* Local address is added. */
926                 if (nhs != 1 || nh->nh_gw)
927                         goto err_inval;
928                 nh->nh_scope = RT_SCOPE_NOWHERE;
929                 nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
930                 err = -ENODEV;
931                 if (nh->nh_dev == NULL)
932                         goto failure;
933         } else {
934                 change_nexthops(fi) {
935                         err = fib_check_nh(cfg, fi, nexthop_nh);
936                         if (err != 0)
937                                 goto failure;
938                 } endfor_nexthops(fi)
939         }
940 
941         if (fi->fib_prefsrc) {
942                 if (cfg->fc_type != RTN_LOCAL || !cfg->fc_dst ||
943                     fi->fib_prefsrc != cfg->fc_dst)
944                         if (inet_addr_type(net, fi->fib_prefsrc) != RTN_LOCAL)
945                                 goto err_inval;
946         }
947 
948         change_nexthops(fi) {
949                 fib_info_update_nh_saddr(net, nexthop_nh);
950         } endfor_nexthops(fi)
951 
952 link_it:
953         ofi = fib_find_info(fi);
954         if (ofi) {
955                 fi->fib_dead = 1;
956                 free_fib_info(fi);
957                 ofi->fib_treeref++;
958                 return ofi;
959         }
960 
961         fi->fib_treeref++;
962         atomic_inc(&fi->fib_clntref);
963         spin_lock_bh(&fib_info_lock);
964         hlist_add_head(&fi->fib_hash,
965                        &fib_info_hash[fib_info_hashfn(fi)]);
966         if (fi->fib_prefsrc) {
967                 struct hlist_head *head;
968 
969                 head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)];
970                 hlist_add_head(&fi->fib_lhash, head);
971         }
972         change_nexthops(fi) {
973                 struct hlist_head *head;
974                 unsigned int hash;
975 
976                 if (!nexthop_nh->nh_dev)
977                         continue;
978                 hash = fib_devindex_hashfn(nexthop_nh->nh_dev->ifindex);
979                 head = &fib_info_devhash[hash];
980                 hlist_add_head(&nexthop_nh->nh_hash, head);
981         } endfor_nexthops(fi)
982         spin_unlock_bh(&fib_info_lock);
983         return fi;
984 
985 err_inval:
986         err = -EINVAL;
987 
988 failure:
989         if (fi) {
990                 fi->fib_dead = 1;
991                 free_fib_info(fi);
992         }
993 
994         return ERR_PTR(err);
995 }
996 
997 int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event,
998                   u32 tb_id, u8 type, __be32 dst, int dst_len, u8 tos,
999                   struct fib_info *fi, unsigned int flags)
1000 {
1001         struct nlmsghdr *nlh;
1002         struct rtmsg *rtm;
1003 
1004         nlh = nlmsg_put(skb, portid, seq, event, sizeof(*rtm), flags);
1005         if (nlh == NULL)
1006                 return -EMSGSIZE;
1007 
1008         rtm = nlmsg_data(nlh);
1009         rtm->rtm_family = AF_INET;
1010         rtm->rtm_dst_len = dst_len;
1011         rtm->rtm_src_len = 0;
1012         rtm->rtm_tos = tos;
1013         if (tb_id < 256)
1014                 rtm->rtm_table = tb_id;
1015         else
1016                 rtm->rtm_table = RT_TABLE_COMPAT;
1017         if (nla_put_u32(skb, RTA_TABLE, tb_id))
1018                 goto nla_put_failure;
1019         rtm->rtm_type = type;
1020         rtm->rtm_flags = fi->fib_flags;
1021         rtm->rtm_scope = fi->fib_scope;
1022         rtm->rtm_protocol = fi->fib_protocol;
1023 
1024         if (rtm->rtm_dst_len &&
1025             nla_put_be32(skb, RTA_DST, dst))
1026                 goto nla_put_failure;
1027         if (fi->fib_priority &&
1028             nla_put_u32(skb, RTA_PRIORITY, fi->fib_priority))
1029                 goto nla_put_failure;
1030         if (rtnetlink_put_metrics(skb, fi->fib_metrics) < 0)
1031                 goto nla_put_failure;
1032 
1033         if (fi->fib_prefsrc &&
1034             nla_put_be32(skb, RTA_PREFSRC, fi->fib_prefsrc))
1035                 goto nla_put_failure;
1036         if (fi->fib_nhs == 1) {
1037                 if (fi->fib_nh->nh_gw &&
1038                     nla_put_be32(skb, RTA_GATEWAY, fi->fib_nh->nh_gw))
1039                         goto nla_put_failure;
1040                 if (fi->fib_nh->nh_oif &&
1041                     nla_put_u32(skb, RTA_OIF, fi->fib_nh->nh_oif))
1042                         goto nla_put_failure;
1043 #ifdef CONFIG_IP_ROUTE_CLASSID
1044                 if (fi->fib_nh[0].nh_tclassid &&
1045                     nla_put_u32(skb, RTA_FLOW, fi->fib_nh[0].nh_tclassid))
1046                         goto nla_put_failure;
1047 #endif
1048         }
1049 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1050         if (fi->fib_nhs > 1) {
1051                 struct rtnexthop *rtnh;
1052                 struct nlattr *mp;
1053 
1054                 mp = nla_nest_start(skb, RTA_MULTIPATH);
1055                 if (mp == NULL)
1056                         goto nla_put_failure;
1057 
1058                 for_nexthops(fi) {
1059                         rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));
1060                         if (rtnh == NULL)
1061                                 goto nla_put_failure;
1062 
1063                         rtnh->rtnh_flags = nh->nh_flags & 0xFF;
1064                         rtnh->rtnh_hops = nh->nh_weight - 1;
1065                         rtnh->rtnh_ifindex = nh->nh_oif;
1066 
1067                         if (nh->nh_gw &&
1068                             nla_put_be32(skb, RTA_GATEWAY, nh->nh_gw))
1069                                 goto nla_put_failure;
1070 #ifdef CONFIG_IP_ROUTE_CLASSID
1071                         if (nh->nh_tclassid &&
1072                             nla_put_u32(skb, RTA_FLOW, nh->nh_tclassid))
1073                                 goto nla_put_failure;
1074 #endif
1075                         /* length of rtnetlink header + attributes */
1076                         rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *) rtnh;
1077                 } endfor_nexthops(fi);
1078 
1079                 nla_nest_end(skb, mp);
1080         }
1081 #endif
1082         return nlmsg_end(skb, nlh);
1083 
1084 nla_put_failure:
1085         nlmsg_cancel(skb, nlh);
1086         return -EMSGSIZE;
1087 }
1088 
1089 /*
1090  * Update FIB if:
1091  * - local address disappeared -> we must delete all the entries
1092  *   referring to it.
1093  * - device went down -> we must shutdown all nexthops going via it.
1094  */
1095 int fib_sync_down_addr(struct net *net, __be32 local)
1096 {
1097         int ret = 0;
1098         unsigned int hash = fib_laddr_hashfn(local);
1099         struct hlist_head *head = &fib_info_laddrhash[hash];
1100         struct fib_info *fi;
1101 
1102         if (fib_info_laddrhash == NULL || local == 0)
1103                 return 0;
1104 
1105         hlist_for_each_entry(fi, head, fib_lhash) {
1106                 if (!net_eq(fi->fib_net, net))
1107                         continue;
1108                 if (fi->fib_prefsrc == local) {
1109                         fi->fib_flags |= RTNH_F_DEAD;
1110                         ret++;
1111                 }
1112         }
1113         return ret;
1114 }
1115 
1116 int fib_sync_down_dev(struct net_device *dev, int force)
1117 {
1118         int ret = 0;
1119         int scope = RT_SCOPE_NOWHERE;
1120         struct fib_info *prev_fi = NULL;
1121         unsigned int hash = fib_devindex_hashfn(dev->ifindex);
1122         struct hlist_head *head = &fib_info_devhash[hash];
1123         struct fib_nh *nh;
1124 
1125         if (force)
1126                 scope = -1;
1127 
1128         hlist_for_each_entry(nh, head, nh_hash) {
1129                 struct fib_info *fi = nh->nh_parent;
1130                 int dead;
1131 
1132                 BUG_ON(!fi->fib_nhs);
1133                 if (nh->nh_dev != dev || fi == prev_fi)
1134                         continue;
1135                 prev_fi = fi;
1136                 dead = 0;
1137                 change_nexthops(fi) {
1138                         if (nexthop_nh->nh_flags & RTNH_F_DEAD)
1139                                 dead++;
1140                         else if (nexthop_nh->nh_dev == dev &&
1141                                  nexthop_nh->nh_scope != scope) {
1142                                 nexthop_nh->nh_flags |= RTNH_F_DEAD;
1143 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1144                                 spin_lock_bh(&fib_multipath_lock);
1145                                 fi->fib_power -= nexthop_nh->nh_power;
1146                                 nexthop_nh->nh_power = 0;
1147                                 spin_unlock_bh(&fib_multipath_lock);
1148 #endif
1149                                 dead++;
1150                         }
1151 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1152                         if (force > 1 && nexthop_nh->nh_dev == dev) {
1153                                 dead = fi->fib_nhs;
1154                                 break;
1155                         }
1156 #endif
1157                 } endfor_nexthops(fi)
1158                 if (dead == fi->fib_nhs) {
1159                         fi->fib_flags |= RTNH_F_DEAD;
1160                         ret++;
1161                 }
1162         }
1163 
1164         return ret;
1165 }
1166 
1167 /* Must be invoked inside of an RCU protected region.  */
1168 void fib_select_default(struct fib_result *res)
1169 {
1170         struct fib_info *fi = NULL, *last_resort = NULL;
1171         struct list_head *fa_head = res->fa_head;
1172         struct fib_table *tb = res->table;
1173         int order = -1, last_idx = -1;
1174         struct fib_alias *fa;
1175 
1176         list_for_each_entry_rcu(fa, fa_head, fa_list) {
1177                 struct fib_info *next_fi = fa->fa_info;
1178 
1179                 if (next_fi->fib_scope != res->scope ||
1180                     fa->fa_type != RTN_UNICAST)
1181                         continue;
1182 
1183                 if (next_fi->fib_priority > res->fi->fib_priority)
1184                         break;
1185                 if (!next_fi->fib_nh[0].nh_gw ||
1186                     next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
1187                         continue;
1188 
1189                 fib_alias_accessed(fa);
1190 
1191                 if (fi == NULL) {
1192                         if (next_fi != res->fi)
1193                                 break;
1194                 } else if (!fib_detect_death(fi, order, &last_resort,
1195                                              &last_idx, tb->tb_default)) {
1196                         fib_result_assign(res, fi);
1197                         tb->tb_default = order;
1198                         goto out;
1199                 }
1200                 fi = next_fi;
1201                 order++;
1202         }
1203 
1204         if (order <= 0 || fi == NULL) {
1205                 tb->tb_default = -1;
1206                 goto out;
1207         }
1208 
1209         if (!fib_detect_death(fi, order, &last_resort, &last_idx,
1210                                 tb->tb_default)) {
1211                 fib_result_assign(res, fi);
1212                 tb->tb_default = order;
1213                 goto out;
1214         }
1215 
1216         if (last_idx >= 0)
1217                 fib_result_assign(res, last_resort);
1218         tb->tb_default = last_idx;
1219 out:
1220         return;
1221 }
1222 
1223 #ifdef CONFIG_IP_ROUTE_MULTIPATH
1224 
1225 /*
1226  * Dead device goes up. We wake up dead nexthops.
1227  * It takes sense only on multipath routes.
1228  */
1229 int fib_sync_up(struct net_device *dev)
1230 {
1231         struct fib_info *prev_fi;
1232         unsigned int hash;
1233         struct hlist_head *head;
1234         struct fib_nh *nh;
1235         int ret;
1236 
1237         if (!(dev->flags & IFF_UP))
1238                 return 0;
1239 
1240         prev_fi = NULL;
1241         hash = fib_devindex_hashfn(dev->ifindex);
1242         head = &fib_info_devhash[hash];
1243         ret = 0;
1244 
1245         hlist_for_each_entry(nh, head, nh_hash) {
1246                 struct fib_info *fi = nh->nh_parent;
1247                 int alive;
1248 
1249                 BUG_ON(!fi->fib_nhs);
1250                 if (nh->nh_dev != dev || fi == prev_fi)
1251                         continue;
1252 
1253                 prev_fi = fi;
1254                 alive = 0;
1255                 change_nexthops(fi) {
1256                         if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1257                                 alive++;
1258                                 continue;
1259                         }
1260                         if (nexthop_nh->nh_dev == NULL ||
1261                             !(nexthop_nh->nh_dev->flags & IFF_UP))
1262                                 continue;
1263                         if (nexthop_nh->nh_dev != dev ||
1264                             !__in_dev_get_rtnl(dev))
1265                                 continue;
1266                         alive++;
1267                         spin_lock_bh(&fib_multipath_lock);
1268                         nexthop_nh->nh_power = 0;
1269                         nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
1270                         spin_unlock_bh(&fib_multipath_lock);
1271                 } endfor_nexthops(fi)
1272 
1273                 if (alive > 0) {
1274                         fi->fib_flags &= ~RTNH_F_DEAD;
1275                         ret++;
1276                 }
1277         }
1278 
1279         return ret;
1280 }
1281 
1282 /*
1283  * The algorithm is suboptimal, but it provides really
1284  * fair weighted route distribution.
1285  */
1286 void fib_select_multipath(struct fib_result *res)
1287 {
1288         struct fib_info *fi = res->fi;
1289         int w;
1290 
1291         spin_lock_bh(&fib_multipath_lock);
1292         if (fi->fib_power <= 0) {
1293                 int power = 0;
1294                 change_nexthops(fi) {
1295                         if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
1296                                 power += nexthop_nh->nh_weight;
1297                                 nexthop_nh->nh_power = nexthop_nh->nh_weight;
1298                         }
1299                 } endfor_nexthops(fi);
1300                 fi->fib_power = power;
1301                 if (power <= 0) {
1302                         spin_unlock_bh(&fib_multipath_lock);
1303                         /* Race condition: route has just become dead. */
1304                         res->nh_sel = 0;
1305                         return;
1306                 }
1307         }
1308 
1309 
1310         /* w should be random number [0..fi->fib_power-1],
1311          * it is pretty bad approximation.
1312          */
1313 
1314         w = jiffies % fi->fib_power;
1315 
1316         change_nexthops(fi) {
1317                 if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
1318                     nexthop_nh->nh_power) {
1319                         w -= nexthop_nh->nh_power;
1320                         if (w <= 0) {
1321                                 nexthop_nh->nh_power--;
1322                                 fi->fib_power--;
1323                                 res->nh_sel = nhsel;
1324                                 spin_unlock_bh(&fib_multipath_lock);
1325                                 return;
1326                         }
1327                 }
1328         } endfor_nexthops(fi);
1329 
1330         /* Race condition: route has just become dead. */
1331         res->nh_sel = 0;
1332         spin_unlock_bh(&fib_multipath_lock);
1333 }
1334 #endif
1335 

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