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