net/ipv6/anycast.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      Anycast support for IPv6
   4  *      Linux INET6 implementation
   5  *
   6  *      Authors:
   7  *      David L Stevens ([email protected])
   8  *
   9  *      based heavily on net/ipv6/mcast.c
  10  */
  11
  12 #include <linux/capability.h>
  13 #include <linux/module.h>
  14 #include <linux/errno.h>
  15 #include <linux/types.h>
  16 #include <linux/random.h>
  17 #include <linux/string.h>
  18 #include <linux/socket.h>
  19 #include <linux/sockios.h>
  20 #include <linux/net.h>
  21 #include <linux/in6.h>
  22 #include <linux/netdevice.h>
  23 #include <linux/if_arp.h>
  24 #include <linux/route.h>
  25 #include <linux/init.h>
  26 #include <linux/proc_fs.h>
  27 #include <linux/seq_file.h>
  28 #include <linux/slab.h>
  29
  30 #include <net/net_namespace.h>
  31 #include <net/sock.h>
  32 #include <net/snmp.h>
  33
  34 #include <net/ipv6.h>
  35 #include <net/protocol.h>
  36 #include <net/if_inet6.h>
  37 #include <net/ndisc.h>
  38 #include <net/addrconf.h>
  39 #include <net/ip6_route.h>
  40
  41 #include <net/checksum.h>
  42
  43 #define IN6_ADDR_HSIZE_SHIFT    8
  44 #define IN6_ADDR_HSIZE          BIT(IN6_ADDR_HSIZE_SHIFT)
  45 /*      anycast address hash table
  46  */
  47 static struct hlist_head inet6_acaddr_lst[IN6_ADDR_HSIZE];
  48 static DEFINE_SPINLOCK(acaddr_hash_lock);
  49
  50 static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr);
  51
  52 static u32 inet6_acaddr_hash(struct net *net, const struct in6_addr *addr)
  53 {
  54         u32 val = ipv6_addr_hash(addr) ^ net_hash_mix(net);
  55
  56         return hash_32(val, IN6_ADDR_HSIZE_SHIFT);
  57 }
  58
  59 /*
  60  *      socket join an anycast group
  61  */
  62
  63 int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
  64 {
  65         struct ipv6_pinfo *np = inet6_sk(sk);
  66         struct net_device *dev = NULL;
  67         struct inet6_dev *idev;
  68         struct ipv6_ac_socklist *pac;
  69         struct net *net = sock_net(sk);
  70         int     ishost = !net->ipv6.devconf_all->forwarding;
  71         int     err = 0;
  72
  73         ASSERT_RTNL();
  74
  75         if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
  76                 return -EPERM;
  77         if (ipv6_addr_is_multicast(addr))
  78                 return -EINVAL;
  79
  80         if (ifindex)
  81                 dev = __dev_get_by_index(net, ifindex);
  82
  83         if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE))
  84                 return -EINVAL;
  85
  86         pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
  87         if (!pac)
  88                 return -ENOMEM;
  89         pac->acl_next = NULL;
  90         pac->acl_addr = *addr;
  91
  92         if (ifindex == 0) {
  93                 struct rt6_info *rt;
  94
  95                 rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
  96                 if (rt) {
  97                         dev = rt->dst.dev;
  98                         ip6_rt_put(rt);
  99                 } else if (ishost) {
 100                         err = -EADDRNOTAVAIL;
 101                         goto error;
 102                 } else {
 103                         /* router, no matching interface: just pick one */
 104                         dev = __dev_get_by_flags(net, IFF_UP,
 105                                                  IFF_UP | IFF_LOOPBACK);
 106                 }
 107         }
 108
 109         if (!dev) {
 110                 err = -ENODEV;
 111                 goto error;
 112         }
 113
 114         idev = __in6_dev_get(dev);
 115         if (!idev) {
 116                 if (ifindex)
 117                         err = -ENODEV;
 118                 else
 119                         err = -EADDRNOTAVAIL;
 120                 goto error;
 121         }
 122         /* reset ishost, now that we have a specific device */
 123         ishost = !idev->cnf.forwarding;
 124
 125         pac->acl_ifindex = dev->ifindex;
 126
 127         /* XXX
 128          * For hosts, allow link-local or matching prefix anycasts.
 129          * This obviates the need for propagating anycast routes while
 130          * still allowing some non-router anycast participation.
 131          */
 132         if (!ipv6_chk_prefix(addr, dev)) {
 133                 if (ishost)
 134                         err = -EADDRNOTAVAIL;
 135                 if (err)
 136                         goto error;
 137         }
 138
 139         err = __ipv6_dev_ac_inc(idev, addr);
 140         if (!err) {
 141                 pac->acl_next = np->ipv6_ac_list;
 142                 np->ipv6_ac_list = pac;
 143                 pac = NULL;
 144         }
 145
 146 error:
 147         if (pac)
 148                 sock_kfree_s(sk, pac, sizeof(*pac));
 149         return err;
 150 }
 151
 152 /*
 153  *      socket leave an anycast group
 154  */
 155 int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 156 {
 157         struct ipv6_pinfo *np = inet6_sk(sk);
 158         struct net_device *dev;
 159         struct ipv6_ac_socklist *pac, *prev_pac;
 160         struct net *net = sock_net(sk);
 161
 162         ASSERT_RTNL();
 163
 164         prev_pac = NULL;
 165         for (pac = np->ipv6_ac_list; pac; pac = pac->acl_next) {
 166                 if ((ifindex == 0 || pac->acl_ifindex == ifindex) &&
 167                      ipv6_addr_equal(&pac->acl_addr, addr))
 168                         break;
 169                 prev_pac = pac;
 170         }
 171         if (!pac)
 172                 return -ENOENT;
 173         if (prev_pac)
 174                 prev_pac->acl_next = pac->acl_next;
 175         else
 176                 np->ipv6_ac_list = pac->acl_next;
 177
 178         dev = __dev_get_by_index(net, pac->acl_ifindex);
 179         if (dev)
 180                 ipv6_dev_ac_dec(dev, &pac->acl_addr);
 181
 182         sock_kfree_s(sk, pac, sizeof(*pac));
 183         return 0;
 184 }
 185
 186 void __ipv6_sock_ac_close(struct sock *sk)
 187 {
 188         struct ipv6_pinfo *np = inet6_sk(sk);
 189         struct net_device *dev = NULL;
 190         struct ipv6_ac_socklist *pac;
 191         struct net *net = sock_net(sk);
 192         int     prev_index;
 193
 194         ASSERT_RTNL();
 195         pac = np->ipv6_ac_list;
 196         np->ipv6_ac_list = NULL;
 197
 198         prev_index = 0;
 199         while (pac) {
 200                 struct ipv6_ac_socklist *next = pac->acl_next;
 201
 202                 if (pac->acl_ifindex != prev_index) {
 203                         dev = __dev_get_by_index(net, pac->acl_ifindex);
 204                         prev_index = pac->acl_ifindex;
 205                 }
 206                 if (dev)
 207                         ipv6_dev_ac_dec(dev, &pac->acl_addr);
 208                 sock_kfree_s(sk, pac, sizeof(*pac));
 209                 pac = next;
 210         }
 211 }
 212
 213 void ipv6_sock_ac_close(struct sock *sk)
 214 {
 215         struct ipv6_pinfo *np = inet6_sk(sk);
 216
 217         if (!np->ipv6_ac_list)
 218                 return;
 219         rtnl_lock();
 220         __ipv6_sock_ac_close(sk);
 221         rtnl_unlock();
 222 }
 223
 224 static void ipv6_add_acaddr_hash(struct net *net, struct ifacaddr6 *aca)
 225 {
 226         unsigned int hash = inet6_acaddr_hash(net, &aca->aca_addr);
 227
 228         spin_lock(&acaddr_hash_lock);
 229         hlist_add_head_rcu(&aca->aca_addr_lst, &inet6_acaddr_lst[hash]);
 230         spin_unlock(&acaddr_hash_lock);
 231 }
 232
 233 static void ipv6_del_acaddr_hash(struct ifacaddr6 *aca)
 234 {
 235         spin_lock(&acaddr_hash_lock);
 236         hlist_del_init_rcu(&aca->aca_addr_lst);
 237         spin_unlock(&acaddr_hash_lock);
 238 }
 239
 240 static void aca_get(struct ifacaddr6 *aca)
 241 {
 242         refcount_inc(&aca->aca_refcnt);
 243 }
 244
 245 static void aca_free_rcu(struct rcu_head *h)
 246 {
 247         struct ifacaddr6 *aca = container_of(h, struct ifacaddr6, rcu);
 248
 249         fib6_info_release(aca->aca_rt);
 250         kfree(aca);
 251 }
 252
 253 static void aca_put(struct ifacaddr6 *ac)
 254 {
 255         if (refcount_dec_and_test(&ac->aca_refcnt)) {
 256                 call_rcu(&ac->rcu, aca_free_rcu);
 257         }
 258 }
 259
 260 static struct ifacaddr6 *aca_alloc(struct fib6_info *f6i,
 261                                    const struct in6_addr *addr)
 262 {
 263         struct ifacaddr6 *aca;
 264
 265         aca = kzalloc(sizeof(*aca), GFP_ATOMIC);
 266         if (!aca)
 267                 return NULL;
 268
 269         aca->aca_addr = *addr;
 270         fib6_info_hold(f6i);
 271         aca->aca_rt = f6i;
 272         INIT_HLIST_NODE(&aca->aca_addr_lst);
 273         aca->aca_users = 1;
 274         /* aca_tstamp should be updated upon changes */
 275         aca->aca_cstamp = aca->aca_tstamp = jiffies;
 276         refcount_set(&aca->aca_refcnt, 1);
 277
 278         return aca;
 279 }
 280
 281 /*
 282  *      device anycast group inc (add if not found)
 283  */
 284 int __ipv6_dev_ac_inc(struct inet6_dev *idev, const struct in6_addr *addr)
 285 {
 286         struct ifacaddr6 *aca;
 287         struct fib6_info *f6i;
 288         struct net *net;
 289         int err;
 290
 291         ASSERT_RTNL();
 292
 293         write_lock_bh(&idev->lock);
 294         if (idev->dead) {
 295                 err = -ENODEV;
 296                 goto out;
 297         }
 298
 299         for (aca = rtnl_dereference(idev->ac_list); aca;
 300              aca = rtnl_dereference(aca->aca_next)) {
 301                 if (ipv6_addr_equal(&aca->aca_addr, addr)) {
 302                         aca->aca_users++;
 303                         err = 0;
 304                         goto out;
 305                 }
 306         }
 307
 308         net = dev_net(idev->dev);
 309         f6i = addrconf_f6i_alloc(net, idev, addr, true, GFP_ATOMIC, NULL);
 310         if (IS_ERR(f6i)) {
 311                 err = PTR_ERR(f6i);
 312                 goto out;
 313         }
 314         aca = aca_alloc(f6i, addr);
 315         if (!aca) {
 316                 fib6_info_release(f6i);
 317                 err = -ENOMEM;
 318                 goto out;
 319         }
 320
 321         /* Hold this for addrconf_join_solict() below before we unlock,
 322          * it is already exposed via idev->ac_list.
 323          */
 324         aca_get(aca);
 325         aca->aca_next = idev->ac_list;
 326         rcu_assign_pointer(idev->ac_list, aca);
 327
 328         write_unlock_bh(&idev->lock);
 329
 330         ipv6_add_acaddr_hash(net, aca);
 331
 332         ip6_ins_rt(net, f6i);
 333
 334         addrconf_join_solict(idev->dev, &aca->aca_addr);
 335
 336         aca_put(aca);
 337         return 0;
 338 out:
 339         write_unlock_bh(&idev->lock);
 340         return err;
 341 }
 342
 343 /*
 344  *      device anycast group decrement
 345  */
 346 int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
 347 {
 348         struct ifacaddr6 *aca, *prev_aca;
 349
 350         ASSERT_RTNL();
 351
 352         write_lock_bh(&idev->lock);
 353         prev_aca = NULL;
 354         for (aca = rtnl_dereference(idev->ac_list); aca;
 355              aca = rtnl_dereference(aca->aca_next)) {
 356                 if (ipv6_addr_equal(&aca->aca_addr, addr))
 357                         break;
 358                 prev_aca = aca;
 359         }
 360         if (!aca) {
 361                 write_unlock_bh(&idev->lock);
 362                 return -ENOENT;
 363         }
 364         if (--aca->aca_users > 0) {
 365                 write_unlock_bh(&idev->lock);
 366                 return 0;
 367         }
 368         if (prev_aca)
 369                 rcu_assign_pointer(prev_aca->aca_next, aca->aca_next);
 370         else
 371                 rcu_assign_pointer(idev->ac_list, aca->aca_next);
 372         write_unlock_bh(&idev->lock);
 373         ipv6_del_acaddr_hash(aca);
 374         addrconf_leave_solict(idev, &aca->aca_addr);
 375
 376         ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
 377
 378         aca_put(aca);
 379         return 0;
 380 }
 381
 382 /* called with rtnl_lock() */
 383 static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
 384 {
 385         struct inet6_dev *idev = __in6_dev_get(dev);
 386
 387         if (!idev)
 388                 return -ENODEV;
 389         return __ipv6_dev_ac_dec(idev, addr);
 390 }
 391
 392 void ipv6_ac_destroy_dev(struct inet6_dev *idev)
 393 {
 394         struct ifacaddr6 *aca;
 395
 396         write_lock_bh(&idev->lock);
 397         while ((aca = rtnl_dereference(idev->ac_list)) != NULL) {
 398                 rcu_assign_pointer(idev->ac_list, aca->aca_next);
 399                 write_unlock_bh(&idev->lock);
 400
 401                 ipv6_del_acaddr_hash(aca);
 402
 403                 addrconf_leave_solict(idev, &aca->aca_addr);
 404
 405                 ip6_del_rt(dev_net(idev->dev), aca->aca_rt, false);
 406
 407                 aca_put(aca);
 408
 409                 write_lock_bh(&idev->lock);
 410         }
 411         write_unlock_bh(&idev->lock);
 412 }
 413
 414 /*
 415  *      check if the interface has this anycast address
 416  *      called with rcu_read_lock()
 417  */
 418 static bool ipv6_chk_acast_dev(struct net_device *dev, const struct in6_addr *addr)
 419 {
 420         struct inet6_dev *idev;
 421         struct ifacaddr6 *aca;
 422
 423         idev = __in6_dev_get(dev);
 424         if (idev) {
 425                 for (aca = rcu_dereference(idev->ac_list); aca;
 426                      aca = rcu_dereference(aca->aca_next))
 427                         if (ipv6_addr_equal(&aca->aca_addr, addr))
 428                                 break;
 429                 return aca != NULL;
 430         }
 431         return false;
 432 }
 433
 434 /*
 435  *      check if given interface (or any, if dev==0) has this anycast address
 436  */
 437 bool ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
 438                          const struct in6_addr *addr)
 439 {
 440         struct net_device *nh_dev;
 441         struct ifacaddr6 *aca;
 442         bool found = false;
 443
 444         rcu_read_lock();
 445         if (dev)
 446                 found = ipv6_chk_acast_dev(dev, addr);
 447         else {
 448                 unsigned int hash = inet6_acaddr_hash(net, addr);
 449
 450                 hlist_for_each_entry_rcu(aca, &inet6_acaddr_lst[hash],
 451                                          aca_addr_lst) {
 452                         nh_dev = fib6_info_nh_dev(aca->aca_rt);
 453                         if (!nh_dev || !net_eq(dev_net(nh_dev), net))
 454                                 continue;
 455                         if (ipv6_addr_equal(&aca->aca_addr, addr)) {
 456                                 found = true;
 457                                 break;
 458                         }
 459                 }
 460         }
 461         rcu_read_unlock();
 462         return found;
 463 }
 464
 465 /*      check if this anycast address is link-local on given interface or
 466  *      is global
 467  */
 468 bool ipv6_chk_acast_addr_src(struct net *net, struct net_device *dev,
 469                              const struct in6_addr *addr)
 470 {
 471         return ipv6_chk_acast_addr(net,
 472                                    (ipv6_addr_type(addr) & IPV6_ADDR_LINKLOCAL ?
 473                                     dev : NULL),
 474                                    addr);
 475 }
 476
 477 #ifdef CONFIG_PROC_FS
 478 struct ac6_iter_state {
 479         struct seq_net_private p;
 480         struct net_device *dev;
 481 };
 482
 483 #define ac6_seq_private(seq)    ((struct ac6_iter_state *)(seq)->private)
 484
 485 static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
 486 {
 487         struct ac6_iter_state *state = ac6_seq_private(seq);
 488         struct net *net = seq_file_net(seq);
 489         struct ifacaddr6 *im = NULL;
 490
 491         for_each_netdev_rcu(net, state->dev) {
 492                 struct inet6_dev *idev;
 493
 494                 idev = __in6_dev_get(state->dev);
 495                 if (!idev)
 496                         continue;
 497                 im = rcu_dereference(idev->ac_list);
 498                 if (im)
 499                         break;
 500         }
 501         return im;
 502 }
 503
 504 static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im)
 505 {
 506         struct ac6_iter_state *state = ac6_seq_private(seq);
 507         struct inet6_dev *idev;
 508
 509         im = rcu_dereference(im->aca_next);
 510         while (!im) {
 511                 state->dev = next_net_device_rcu(state->dev);
 512                 if (!state->dev)
 513                         break;
 514                 idev = __in6_dev_get(state->dev);
 515                 if (!idev)
 516                         continue;
 517                 im = rcu_dereference(idev->ac_list);
 518         }
 519         return im;
 520 }
 521
 522 static struct ifacaddr6 *ac6_get_idx(struct seq_file *seq, loff_t pos)
 523 {
 524         struct ifacaddr6 *im = ac6_get_first(seq);
 525         if (im)
 526                 while (pos && (im = ac6_get_next(seq, im)) != NULL)
 527                         --pos;
 528         return pos ? NULL : im;
 529 }
 530
 531 static void *ac6_seq_start(struct seq_file *seq, loff_t *pos)
 532         __acquires(RCU)
 533 {
 534         rcu_read_lock();
 535         return ac6_get_idx(seq, *pos);
 536 }
 537
 538 static void *ac6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 539 {
 540         struct ifacaddr6 *im = ac6_get_next(seq, v);
 541
 542         ++*pos;
 543         return im;
 544 }
 545
 546 static void ac6_seq_stop(struct seq_file *seq, void *v)
 547         __releases(RCU)
 548 {
 549         rcu_read_unlock();
 550 }
 551
 552 static int ac6_seq_show(struct seq_file *seq, void *v)
 553 {
 554         struct ifacaddr6 *im = (struct ifacaddr6 *)v;
 555         struct ac6_iter_state *state = ac6_seq_private(seq);
 556
 557         seq_printf(seq, "%-4d %-15s %pi6 %5d\n",
 558                    state->dev->ifindex, state->dev->name,
 559                    &im->aca_addr, im->aca_users);
 560         return 0;
 561 }
 562
 563 static const struct seq_operations ac6_seq_ops = {
 564         .start  =       ac6_seq_start,
 565         .next   =       ac6_seq_next,
 566         .stop   =       ac6_seq_stop,
 567         .show   =       ac6_seq_show,
 568 };
 569
 570 int __net_init ac6_proc_init(struct net *net)
 571 {
 572         if (!proc_create_net("anycast6", 0444, net->proc_net, &ac6_seq_ops,
 573                         sizeof(struct ac6_iter_state)))
 574                 return -ENOMEM;
 575
 576         return 0;
 577 }
 578
 579 void ac6_proc_exit(struct net *net)
 580 {
 581         remove_proc_entry("anycast6", net->proc_net);
 582 }
 583 #endif
 584
 585 /*      Init / cleanup code
 586  */
 587 int __init ipv6_anycast_init(void)
 588 {
 589         int i;
 590
 591         for (i = 0; i < IN6_ADDR_HSIZE; i++)
 592                 INIT_HLIST_HEAD(&inet6_acaddr_lst[i]);
 593         return 0;
 594 }
 595
 596 void ipv6_anycast_cleanup(void)
 597 {
 598         int i;
 599
 600         spin_lock(&acaddr_hash_lock);
 601         for (i = 0; i < IN6_ADDR_HSIZE; i++)
 602                 WARN_ON(!hlist_empty(&inet6_acaddr_lst[i]));
 603         spin_unlock(&acaddr_hash_lock);
 604 }