net/core/fib_rules.c

   1 /*
   2  * net/core/fib_rules.c         Generic Routing Rules
   3  *
   4  *      This program is free software; you can redistribute it and/or
   5  *      modify it under the terms of the GNU General Public License as
   6  *      published by the Free Software Foundation, version 2.
   7  *
   8  * Authors:     Thomas Graf <tgraf@suug.ch>
   9  */
  10
  11 #include <linux/types.h>
  12 #include <linux/kernel.h>
  13 #include <linux/list.h>
  14 #include <net/net_namespace.h>
  15 #include <net/sock.h>
  16 #include <net/fib_rules.h>
  17
  18 static LIST_HEAD(rules_ops);
  19 static DEFINE_SPINLOCK(rules_mod_lock);
  20
  21 int fib_default_rule_add(struct fib_rules_ops *ops,
  22                          u32 pref, u32 table, u32 flags)
  23 {
  24         struct fib_rule *r;
  25
  26         r = kzalloc(ops->rule_size, GFP_KERNEL);
  27         if (r == NULL)
  28                 return -ENOMEM;
  29
  30         atomic_set(&r->refcnt, 1);
  31         r->action = FR_ACT_TO_TBL;
  32         r->pref = pref;
  33         r->table = table;
  34         r->flags = flags;
  35
  36         /* The lock is not required here, the list in unreacheable
  37          * at the moment this function is called */
  38         list_add_tail(&r->list, &ops->rules_list);
  39         return 0;
  40 }
  41 EXPORT_SYMBOL(fib_default_rule_add);
  42
  43 static void notify_rule_change(int event, struct fib_rule *rule,
  44                                struct fib_rules_ops *ops, struct nlmsghdr *nlh,
  45                                u32 pid);
  46
  47 static struct fib_rules_ops *lookup_rules_ops(int family)
  48 {
  49         struct fib_rules_ops *ops;
  50
  51         rcu_read_lock();
  52         list_for_each_entry_rcu(ops, &rules_ops, list) {
  53                 if (ops->family == family) {
  54                         if (!try_module_get(ops->owner))
  55                                 ops = NULL;
  56                         rcu_read_unlock();
  57                         return ops;
  58                 }
  59         }
  60         rcu_read_unlock();
  61
  62         return NULL;
  63 }
  64
  65 static void rules_ops_put(struct fib_rules_ops *ops)
  66 {
  67         if (ops)
  68                 module_put(ops->owner);
  69 }
  70
  71 static void flush_route_cache(struct fib_rules_ops *ops)
  72 {
  73         if (ops->flush_cache)
  74                 ops->flush_cache();
  75 }
  76
  77 int fib_rules_register(struct fib_rules_ops *ops)
  78 {
  79         int err = -EEXIST;
  80         struct fib_rules_ops *o;
  81
  82         if (ops->rule_size < sizeof(struct fib_rule))
  83                 return -EINVAL;
  84
  85         if (ops->match == NULL || ops->configure == NULL ||
  86             ops->compare == NULL || ops->fill == NULL ||
  87             ops->action == NULL)
  88                 return -EINVAL;
  89
  90         spin_lock(&rules_mod_lock);
  91         list_for_each_entry(o, &rules_ops, list)
  92                 if (ops->family == o->family)
  93                         goto errout;
  94
  95         list_add_tail_rcu(&ops->list, &rules_ops);
  96         err = 0;
  97 errout:
  98         spin_unlock(&rules_mod_lock);
  99
 100         return err;
 101 }
 102
 103 EXPORT_SYMBOL_GPL(fib_rules_register);
 104
 105 void fib_rules_cleanup_ops(struct fib_rules_ops *ops)
 106 {
 107         struct fib_rule *rule, *tmp;
 108
 109         list_for_each_entry_safe(rule, tmp, &ops->rules_list, list) {
 110                 list_del_rcu(&rule->list);
 111                 fib_rule_put(rule);
 112         }
 113 }
 114 EXPORT_SYMBOL_GPL(fib_rules_cleanup_ops);
 115
 116 int fib_rules_unregister(struct fib_rules_ops *ops)
 117 {
 118         int err = 0;
 119         struct fib_rules_ops *o;
 120
 121         spin_lock(&rules_mod_lock);
 122         list_for_each_entry(o, &rules_ops, list) {
 123                 if (o == ops) {
 124                         list_del_rcu(&o->list);
 125                         fib_rules_cleanup_ops(ops);
 126                         goto out;
 127                 }
 128         }
 129
 130         err = -ENOENT;
 131 out:
 132         spin_unlock(&rules_mod_lock);
 133
 134         synchronize_rcu();
 135
 136         return err;
 137 }
 138
 139 EXPORT_SYMBOL_GPL(fib_rules_unregister);
 140
 141 static int fib_rule_match(struct fib_rule *rule, struct fib_rules_ops *ops,
 142                           struct flowi *fl, int flags)
 143 {
 144         int ret = 0;
 145
 146         if (rule->ifindex && (rule->ifindex != fl->iif))
 147                 goto out;
 148
 149         if ((rule->mark ^ fl->mark) & rule->mark_mask)
 150                 goto out;
 151
 152         ret = ops->match(rule, fl, flags);
 153 out:
 154         return (rule->flags & FIB_RULE_INVERT) ? !ret : ret;
 155 }
 156
 157 int fib_rules_lookup(struct fib_rules_ops *ops, struct flowi *fl,
 158                      int flags, struct fib_lookup_arg *arg)
 159 {
 160         struct fib_rule *rule;
 161         int err;
 162
 163         rcu_read_lock();
 164
 165         list_for_each_entry_rcu(rule, &ops->rules_list, list) {
 166 jumped:
 167                 if (!fib_rule_match(rule, ops, fl, flags))
 168                         continue;
 169
 170                 if (rule->action == FR_ACT_GOTO) {
 171                         struct fib_rule *target;
 172
 173                         target = rcu_dereference(rule->ctarget);
 174                         if (target == NULL) {
 175                                 continue;
 176                         } else {
 177                                 rule = target;
 178                                 goto jumped;
 179                         }
 180                 } else if (rule->action == FR_ACT_NOP)
 181                         continue;
 182                 else
 183                         err = ops->action(rule, fl, flags, arg);
 184
 185                 if (err != -EAGAIN) {
 186                         fib_rule_get(rule);
 187                         arg->rule = rule;
 188                         goto out;
 189                 }
 190         }
 191
 192         err = -ESRCH;
 193 out:
 194         rcu_read_unlock();
 195
 196         return err;
 197 }
 198
 199 EXPORT_SYMBOL_GPL(fib_rules_lookup);
 200
 201 static int validate_rulemsg(struct fib_rule_hdr *frh, struct nlattr **tb,
 202                             struct fib_rules_ops *ops)
 203 {
 204         int err = -EINVAL;
 205
 206         if (frh->src_len)
 207                 if (tb[FRA_SRC] == NULL ||
 208                     frh->src_len > (ops->addr_size * 8) ||
 209                     nla_len(tb[FRA_SRC]) != ops->addr_size)
 210                         goto errout;
 211
 212         if (frh->dst_len)
 213                 if (tb[FRA_DST] == NULL ||
 214                     frh->dst_len > (ops->addr_size * 8) ||
 215                     nla_len(tb[FRA_DST]) != ops->addr_size)
 216                         goto errout;
 217
 218         err = 0;
 219 errout:
 220         return err;
 221 }
 222
 223 static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 224 {
 225         struct net *net = skb->sk->sk_net;
 226         struct fib_rule_hdr *frh = nlmsg_data(nlh);
 227         struct fib_rules_ops *ops = NULL;
 228         struct fib_rule *rule, *r, *last = NULL;
 229         struct nlattr *tb[FRA_MAX+1];
 230         int err = -EINVAL, unresolved = 0;
 231
 232         if (net != &init_net)
 233                 return -EINVAL;
 234
 235         if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh)))
 236                 goto errout;
 237
 238         ops = lookup_rules_ops(frh->family);
 239         if (ops == NULL) {
 240                 err = EAFNOSUPPORT;
 241                 goto errout;
 242         }
 243
 244         err = nlmsg_parse(nlh, sizeof(*frh), tb, FRA_MAX, ops->policy);
 245         if (err < 0)
 246                 goto errout;
 247
 248         err = validate_rulemsg(frh, tb, ops);
 249         if (err < 0)
 250                 goto errout;
 251
 252         rule = kzalloc(ops->rule_size, GFP_KERNEL);
 253         if (rule == NULL) {
 254                 err = -ENOMEM;
 255                 goto errout;
 256         }
 257
 258         if (tb[FRA_PRIORITY])
 259                 rule->pref = nla_get_u32(tb[FRA_PRIORITY]);
 260
 261         if (tb[FRA_IFNAME]) {
 262                 struct net_device *dev;
 263
 264                 rule->ifindex = -1;
 265                 nla_strlcpy(rule->ifname, tb[FRA_IFNAME], IFNAMSIZ);
 266                 dev = __dev_get_by_name(net, rule->ifname);
 267                 if (dev)
 268                         rule->ifindex = dev->ifindex;
 269         }
 270
 271         if (tb[FRA_FWMARK]) {
 272                 rule->mark = nla_get_u32(tb[FRA_FWMARK]);
 273                 if (rule->mark)
 274                         /* compatibility: if the mark value is non-zero all bits
 275                          * are compared unless a mask is explicitly specified.
 276                          */
 277                         rule->mark_mask = 0xFFFFFFFF;
 278         }
 279
 280         if (tb[FRA_FWMASK])
 281                 rule->mark_mask = nla_get_u32(tb[FRA_FWMASK]);
 282
 283         rule->action = frh->action;
 284         rule->flags = frh->flags;
 285         rule->table = frh_get_table(frh, tb);
 286
 287         if (!rule->pref && ops->default_pref)
 288                 rule->pref = ops->default_pref();
 289
 290         err = -EINVAL;
 291         if (tb[FRA_GOTO]) {
 292                 if (rule->action != FR_ACT_GOTO)
 293                         goto errout_free;
 294
 295                 rule->target = nla_get_u32(tb[FRA_GOTO]);
 296                 /* Backward jumps are prohibited to avoid endless loops */
 297                 if (rule->target <= rule->pref)
 298                         goto errout_free;
 299
 300                 list_for_each_entry(r, &ops->rules_list, list) {
 301                         if (r->pref == rule->target) {
 302                                 rule->ctarget = r;
 303                                 break;
 304                         }
 305                 }
 306
 307                 if (rule->ctarget == NULL)
 308                         unresolved = 1;
 309         } else if (rule->action == FR_ACT_GOTO)
 310                 goto errout_free;
 311
 312         err = ops->configure(rule, skb, nlh, frh, tb);
 313         if (err < 0)
 314                 goto errout_free;
 315
 316         list_for_each_entry(r, &ops->rules_list, list) {
 317                 if (r->pref > rule->pref)
 318                         break;
 319                 last = r;
 320         }
 321
 322         fib_rule_get(rule);
 323
 324         if (ops->unresolved_rules) {
 325                 /*
 326                  * There are unresolved goto rules in the list, check if
 327                  * any of them are pointing to this new rule.
 328                  */
 329                 list_for_each_entry(r, &ops->rules_list, list) {
 330                         if (r->action == FR_ACT_GOTO &&
 331                             r->target == rule->pref) {
 332                                 BUG_ON(r->ctarget != NULL);
 333                                 rcu_assign_pointer(r->ctarget, rule);
 334                                 if (--ops->unresolved_rules == 0)
 335                                         break;
 336                         }
 337                 }
 338         }
 339
 340         if (rule->action == FR_ACT_GOTO)
 341                 ops->nr_goto_rules++;
 342
 343         if (unresolved)
 344                 ops->unresolved_rules++;
 345
 346         if (last)
 347                 list_add_rcu(&rule->list, &last->list);
 348         else
 349                 list_add_rcu(&rule->list, &ops->rules_list);
 350
 351         notify_rule_change(RTM_NEWRULE, rule, ops, nlh, NETLINK_CB(skb).pid);
 352         flush_route_cache(ops);
 353         rules_ops_put(ops);
 354         return 0;
 355
 356 errout_free:
 357         kfree(rule);
 358 errout:
 359         rules_ops_put(ops);
 360         return err;
 361 }
 362
 363 static int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 364 {
 365         struct net *net = skb->sk->sk_net;
 366         struct fib_rule_hdr *frh = nlmsg_data(nlh);
 367         struct fib_rules_ops *ops = NULL;
 368         struct fib_rule *rule, *tmp;
 369         struct nlattr *tb[FRA_MAX+1];
 370         int err = -EINVAL;
 371
 372         if (net != &init_net)
 373                 return -EINVAL;
 374
 375         if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh)))
 376                 goto errout;
 377
 378         ops = lookup_rules_ops(frh->family);
 379         if (ops == NULL) {
 380                 err = EAFNOSUPPORT;
 381                 goto errout;
 382         }
 383
 384         err = nlmsg_parse(nlh, sizeof(*frh), tb, FRA_MAX, ops->policy);
 385         if (err < 0)
 386                 goto errout;
 387
 388         err = validate_rulemsg(frh, tb, ops);
 389         if (err < 0)
 390                 goto errout;
 391
 392         list_for_each_entry(rule, &ops->rules_list, list) {
 393                 if (frh->action && (frh->action != rule->action))
 394                         continue;
 395
 396                 if (frh->table && (frh_get_table(frh, tb) != rule->table))
 397                         continue;
 398
 399                 if (tb[FRA_PRIORITY] &&
 400                     (rule->pref != nla_get_u32(tb[FRA_PRIORITY])))
 401                         continue;
 402
 403                 if (tb[FRA_IFNAME] &&
 404                     nla_strcmp(tb[FRA_IFNAME], rule->ifname))
 405                         continue;
 406
 407                 if (tb[FRA_FWMARK] &&
 408                     (rule->mark != nla_get_u32(tb[FRA_FWMARK])))
 409                         continue;
 410
 411                 if (tb[FRA_FWMASK] &&
 412                     (rule->mark_mask != nla_get_u32(tb[FRA_FWMASK])))
 413                         continue;
 414
 415                 if (!ops->compare(rule, frh, tb))
 416                         continue;
 417
 418                 if (rule->flags & FIB_RULE_PERMANENT) {
 419                         err = -EPERM;
 420                         goto errout;
 421                 }
 422
 423                 list_del_rcu(&rule->list);
 424
 425                 if (rule->action == FR_ACT_GOTO)
 426                         ops->nr_goto_rules--;
 427
 428                 /*
 429                  * Check if this rule is a target to any of them. If so,
 430                  * disable them. As this operation is eventually very
 431                  * expensive, it is only performed if goto rules have
 432                  * actually been added.
 433                  */
 434                 if (ops->nr_goto_rules > 0) {
 435                         list_for_each_entry(tmp, &ops->rules_list, list) {
 436                                 if (tmp->ctarget == rule) {
 437                                         rcu_assign_pointer(tmp->ctarget, NULL);
 438                                         ops->unresolved_rules++;
 439                                 }
 440                         }
 441                 }
 442
 443                 synchronize_rcu();
 444                 notify_rule_change(RTM_DELRULE, rule, ops, nlh,
 445                                    NETLINK_CB(skb).pid);
 446                 fib_rule_put(rule);
 447                 flush_route_cache(ops);
 448                 rules_ops_put(ops);
 449                 return 0;
 450         }
 451
 452         err = -ENOENT;
 453 errout:
 454         rules_ops_put(ops);
 455         return err;
 456 }
 457
 458 static inline size_t fib_rule_nlmsg_size(struct fib_rules_ops *ops,
 459                                          struct fib_rule *rule)
 460 {
 461         size_t payload = NLMSG_ALIGN(sizeof(struct fib_rule_hdr))
 462                          + nla_total_size(IFNAMSIZ) /* FRA_IFNAME */
 463                          + nla_total_size(4) /* FRA_PRIORITY */
 464                          + nla_total_size(4) /* FRA_TABLE */
 465                          + nla_total_size(4) /* FRA_FWMARK */
 466                          + nla_total_size(4); /* FRA_FWMASK */
 467
 468         if (ops->nlmsg_payload)
 469                 payload += ops->nlmsg_payload(rule);
 470
 471         return payload;
 472 }
 473
 474 static int fib_nl_fill_rule(struct sk_buff *skb, struct fib_rule *rule,
 475                             u32 pid, u32 seq, int type, int flags,
 476                             struct fib_rules_ops *ops)
 477 {
 478         struct nlmsghdr *nlh;
 479         struct fib_rule_hdr *frh;
 480
 481         nlh = nlmsg_put(skb, pid, seq, type, sizeof(*frh), flags);
 482         if (nlh == NULL)
 483                 return -EMSGSIZE;
 484
 485         frh = nlmsg_data(nlh);
 486         frh->table = rule->table;
 487         NLA_PUT_U32(skb, FRA_TABLE, rule->table);
 488         frh->res1 = 0;
 489         frh->res2 = 0;
 490         frh->action = rule->action;
 491         frh->flags = rule->flags;
 492
 493         if (rule->action == FR_ACT_GOTO && rule->ctarget == NULL)
 494                 frh->flags |= FIB_RULE_UNRESOLVED;
 495
 496         if (rule->ifname[0]) {
 497                 NLA_PUT_STRING(skb, FRA_IFNAME, rule->ifname);
 498
 499                 if (rule->ifindex == -1)
 500                         frh->flags |= FIB_RULE_DEV_DETACHED;
 501         }
 502
 503         if (rule->pref)
 504                 NLA_PUT_U32(skb, FRA_PRIORITY, rule->pref);
 505
 506         if (rule->mark)
 507                 NLA_PUT_U32(skb, FRA_FWMARK, rule->mark);
 508
 509         if (rule->mark_mask || rule->mark)
 510                 NLA_PUT_U32(skb, FRA_FWMASK, rule->mark_mask);
 511
 512         if (rule->target)
 513                 NLA_PUT_U32(skb, FRA_GOTO, rule->target);
 514
 515         if (ops->fill(rule, skb, nlh, frh) < 0)
 516                 goto nla_put_failure;
 517
 518         return nlmsg_end(skb, nlh);
 519
 520 nla_put_failure:
 521         nlmsg_cancel(skb, nlh);
 522         return -EMSGSIZE;
 523 }
 524
 525 static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb,
 526                       struct fib_rules_ops *ops)
 527 {
 528         int idx = 0;
 529         struct fib_rule *rule;
 530
 531         list_for_each_entry(rule, &ops->rules_list, list) {
 532                 if (idx < cb->args[1])
 533                         goto skip;
 534
 535                 if (fib_nl_fill_rule(skb, rule, NETLINK_CB(cb->skb).pid,
 536                                      cb->nlh->nlmsg_seq, RTM_NEWRULE,
 537                                      NLM_F_MULTI, ops) < 0)
 538                         break;
 539 skip:
 540                 idx++;
 541         }
 542         cb->args[1] = idx;
 543         rules_ops_put(ops);
 544
 545         return skb->len;
 546 }
 547
 548 static int fib_nl_dumprule(struct sk_buff *skb, struct netlink_callback *cb)
 549 {
 550         struct net *net = skb->sk->sk_net;
 551         struct fib_rules_ops *ops;
 552         int idx = 0, family;
 553
 554         if (net != &init_net)
 555                 return -EINVAL;
 556
 557         family = rtnl_msg_family(cb->nlh);
 558         if (family != AF_UNSPEC) {
 559                 /* Protocol specific dump request */
 560                 ops = lookup_rules_ops(family);
 561                 if (ops == NULL)
 562                         return -EAFNOSUPPORT;
 563
 564                 return dump_rules(skb, cb, ops);
 565         }
 566
 567         rcu_read_lock();
 568         list_for_each_entry_rcu(ops, &rules_ops, list) {
 569                 if (idx < cb->args[0] || !try_module_get(ops->owner))
 570                         goto skip;
 571
 572                 if (dump_rules(skb, cb, ops) < 0)
 573                         break;
 574
 575                 cb->args[1] = 0;
 576         skip:
 577                 idx++;
 578         }
 579         rcu_read_unlock();
 580         cb->args[0] = idx;
 581
 582         return skb->len;
 583 }
 584
 585 static void notify_rule_change(int event, struct fib_rule *rule,
 586                                struct fib_rules_ops *ops, struct nlmsghdr *nlh,
 587                                u32 pid)
 588 {
 589         struct sk_buff *skb;
 590         int err = -ENOBUFS;
 591
 592         skb = nlmsg_new(fib_rule_nlmsg_size(ops, rule), GFP_KERNEL);
 593         if (skb == NULL)
 594                 goto errout;
 595
 596         err = fib_nl_fill_rule(skb, rule, pid, nlh->nlmsg_seq, event, 0, ops);
 597         if (err < 0) {
 598                 /* -EMSGSIZE implies BUG in fib_rule_nlmsg_size() */
 599                 WARN_ON(err == -EMSGSIZE);
 600                 kfree_skb(skb);
 601                 goto errout;
 602         }
 603         err = rtnl_notify(skb, &init_net, pid, ops->nlgroup, nlh, GFP_KERNEL);
 604 errout:
 605         if (err < 0)
 606                 rtnl_set_sk_err(&init_net, ops->nlgroup, err);
 607 }
 608
 609 static void attach_rules(struct list_head *rules, struct net_device *dev)
 610 {
 611         struct fib_rule *rule;
 612
 613         list_for_each_entry(rule, rules, list) {
 614                 if (rule->ifindex == -1 &&
 615                     strcmp(dev->name, rule->ifname) == 0)
 616                         rule->ifindex = dev->ifindex;
 617         }
 618 }
 619
 620 static void detach_rules(struct list_head *rules, struct net_device *dev)
 621 {
 622         struct fib_rule *rule;
 623
 624         list_for_each_entry(rule, rules, list)
 625                 if (rule->ifindex == dev->ifindex)
 626                         rule->ifindex = -1;
 627 }
 628
 629
 630 static int fib_rules_event(struct notifier_block *this, unsigned long event,
 631                             void *ptr)
 632 {
 633         struct net_device *dev = ptr;
 634         struct fib_rules_ops *ops;
 635
 636         if (dev->nd_net != &init_net)
 637                 return NOTIFY_DONE;
 638
 639         ASSERT_RTNL();
 640         rcu_read_lock();
 641
 642         switch (event) {
 643         case NETDEV_REGISTER:
 644                 list_for_each_entry(ops, &rules_ops, list)
 645                         attach_rules(&ops->rules_list, dev);
 646                 break;
 647
 648         case NETDEV_UNREGISTER:
 649                 list_for_each_entry(ops, &rules_ops, list)
 650                         detach_rules(&ops->rules_list, dev);
 651                 break;
 652         }
 653
 654         rcu_read_unlock();
 655
 656         return NOTIFY_DONE;
 657 }
 658
 659 static struct notifier_block fib_rules_notifier = {
 660         .notifier_call = fib_rules_event,
 661 };
 662
 663 static int __init fib_rules_init(void)
 664 {
 665         rtnl_register(PF_UNSPEC, RTM_NEWRULE, fib_nl_newrule, NULL);
 666         rtnl_register(PF_UNSPEC, RTM_DELRULE, fib_nl_delrule, NULL);
 667         rtnl_register(PF_UNSPEC, RTM_GETRULE, NULL, fib_nl_dumprule);
 668
 669         return register_netdevice_notifier(&fib_rules_notifier);
 670 }
 671
 672 subsys_initcall(fib_rules_init);