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