sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <ifaddrs.h>
  22 #include <netdb.h>
  23 #include <stddef.h>
  24 #include <string.h>
  25 #include <time.h>
  26 #include <unistd.h>
  27 #include <stdint.h>
  28 #include <sys/socket.h>
  29
  30 #include <asm/types.h>
  31 #include <linux/netlink.h>
  32 #include <linux/rtnetlink.h>
  33
  34 #include <not-cancel.h>
  35 #include <bits/libc-lock.h>
  36 #include <atomic.h>
  37 #include <nscd/nscd-client.h>
  38
  39
  40 #ifndef IFA_F_HOMEADDRESS
  41 # define IFA_F_HOMEADDRESS 0
  42 #endif
  43 #ifndef IFA_F_OPTIMISTIC
  44 # define IFA_F_OPTIMISTIC 0
  45 #endif
  46
  47
  48 struct cached_data
  49 {
  50   uint32_t timestamp;
  51   uint32_t usecnt;
  52   bool seen_ipv4;
  53   bool seen_ipv6;
  54   size_t in6ailen;
  55   struct in6addrinfo in6ai[0];
  56 };
  57
  58 static struct cached_data noai6ai_cached =
  59   {
  60     .usecnt = 1,        /* Make sure we never try to delete this entry.  */
  61     .in6ailen = 0
  62   };
  63
  64 static struct cached_data *cache;
  65 __libc_lock_define_initialized (static, lock);
  66
  67
  68 #if IS_IN (nscd)
  69 static uint32_t nl_timestamp;
  70
  71 uint32_t
  72 __bump_nl_timestamp (void)
  73 {
  74   if (atomic_increment_val (&nl_timestamp) == 0)
  75     atomic_increment (&nl_timestamp);
  76
  77   return nl_timestamp;
  78 }
  79 #endif
  80
  81 static inline uint32_t
  82 get_nl_timestamp (void)
  83 {
  84 #if IS_IN (nscd)
  85   return nl_timestamp;
  86 #elif defined USE_NSCD
  87   return __nscd_get_nl_timestamp ();
  88 #else
  89   return 0;
  90 #endif
  91 }
  92
  93 static inline bool
  94 cache_valid_p (void)
  95 {
  96   if (cache != NULL)
  97     {
  98       uint32_t timestamp = get_nl_timestamp ();
  99       return timestamp != 0 && cache->timestamp == timestamp;
 100     }
 101   return false;
 102 }
 103
 104
 105 static struct cached_data *
 106 make_request (int fd, pid_t pid)
 107 {
 108   struct req
 109   {
 110     struct nlmsghdr nlh;
 111     struct rtgenmsg g;
 112     /* struct rtgenmsg consists of a single byte.  This means there
 113        are three bytes of padding included in the REQ definition.
 114        We make them explicit here.  */
 115     char pad[3];
 116   } req;
 117   struct sockaddr_nl nladdr;
 118
 119   req.nlh.nlmsg_len = sizeof (req);
 120   req.nlh.nlmsg_type = RTM_GETADDR;
 121   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
 122   req.nlh.nlmsg_pid = 0;
 123   req.nlh.nlmsg_seq = time (NULL);
 124   req.g.rtgen_family = AF_UNSPEC;
 125
 126   assert (sizeof (req) - offsetof (struct req, pad) == 3);
 127   memset (req.pad, '\0', sizeof (req.pad));
 128
 129   memset (&nladdr, '\0', sizeof (nladdr));
 130   nladdr.nl_family = AF_NETLINK;
 131
 132 #ifdef PAGE_SIZE
 133   /* Help the compiler optimize out the malloc call if PAGE_SIZE
 134      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
 135   const size_t buf_size = PAGE_SIZE;
 136 #else
 137   const size_t buf_size = __getpagesize ();
 138 #endif
 139   bool use_malloc = false;
 140   char *buf;
 141   size_t alloca_used = 0;
 142
 143   if (__libc_use_alloca (buf_size))
 144     buf = alloca_account (buf_size, alloca_used);
 145   else
 146     {
 147       buf = malloc (buf_size);
 148       if (buf != NULL)
 149         use_malloc = true;
 150       else
 151         goto out_fail;
 152     }
 153
 154   struct iovec iov = { buf, buf_size };
 155
 156   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
 157                                     (struct sockaddr *) &nladdr,
 158                                     sizeof (nladdr))) < 0)
 159     goto out_fail;
 160
 161   bool done = false;
 162   struct in6ailist
 163   {
 164     struct in6addrinfo info;
 165     struct in6ailist *next;
 166     bool use_malloc;
 167   } *in6ailist = NULL;
 168   size_t in6ailistlen = 0;
 169   bool seen_ipv4 = false;
 170   bool seen_ipv6 = false;
 171
 172   do
 173     {
 174       struct msghdr msg =
 175         {
 176           (void *) &nladdr, sizeof (nladdr),
 177           &iov, 1,
 178           NULL, 0,
 179           0
 180         };
 181
 182       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 183       if (read_len <= 0)
 184         goto out_fail2;
 185
 186       if (msg.msg_flags & MSG_TRUNC)
 187         goto out_fail2;
 188
 189       struct nlmsghdr *nlmh;
 190       for (nlmh = (struct nlmsghdr *) buf;
 191            NLMSG_OK (nlmh, (size_t) read_len);
 192            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 193         {
 194           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 195               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 196             continue;
 197
 198           if (nlmh->nlmsg_type == RTM_NEWADDR)
 199             {
 200               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 201               struct rtattr *rta = IFA_RTA (ifam);
 202               size_t len = nlmh->nlmsg_len - NLMSG_LENGTH (sizeof (*ifam));
 203
 204               if (ifam->ifa_family != AF_INET
 205                   && ifam->ifa_family != AF_INET6)
 206                 continue;
 207
 208               const void *local = NULL;
 209               const void *address = NULL;
 210               while (RTA_OK (rta, len))
 211                 {
 212                   switch (rta->rta_type)
 213                     {
 214                     case IFA_LOCAL:
 215                       local = RTA_DATA (rta);
 216                       break;
 217
 218                     case IFA_ADDRESS:
 219                       address = RTA_DATA (rta);
 220                       goto out;
 221                     }
 222
 223                   rta = RTA_NEXT (rta, len);
 224                 }
 225
 226               if (local != NULL)
 227                 {
 228                   address = local;
 229                 out:
 230                   if (ifam->ifa_family == AF_INET)
 231                     {
 232                       if (*(const in_addr_t *) address
 233                           != htonl (INADDR_LOOPBACK))
 234                         seen_ipv4 = true;
 235                     }
 236                   else
 237                     {
 238                       if (!IN6_IS_ADDR_LOOPBACK (address))
 239                         seen_ipv6 = true;
 240                     }
 241                 }
 242
 243               struct in6ailist *newp;
 244               if (__libc_use_alloca (alloca_used + sizeof (*newp)))
 245                 {
 246                   newp = alloca_account (sizeof (*newp), alloca_used);
 247                   newp->use_malloc = false;
 248                 }
 249               else
 250                 {
 251                   newp = malloc (sizeof (*newp));
 252                   if (newp == NULL)
 253                     goto out_fail2;
 254                   newp->use_malloc = true;
 255                 }
 256               newp->info.flags = (((ifam->ifa_flags
 257                                     & (IFA_F_DEPRECATED
 258                                        | IFA_F_OPTIMISTIC))
 259                                    ? in6ai_deprecated : 0)
 260                                   | ((ifam->ifa_flags
 261                                       & IFA_F_HOMEADDRESS)
 262                                      ? in6ai_homeaddress : 0));
 263               newp->info.prefixlen = ifam->ifa_prefixlen;
 264               newp->info.index = ifam->ifa_index;
 265               if (ifam->ifa_family == AF_INET)
 266                 {
 267                   newp->info.addr[0] = 0;
 268                   newp->info.addr[1] = 0;
 269                   newp->info.addr[2] = htonl (0xffff);
 270                   newp->info.addr[3] = *(const in_addr_t *) address;
 271                 }
 272               else
 273                 memcpy (newp->info.addr, address, sizeof (newp->info.addr));
 274               newp->next = in6ailist;
 275               in6ailist = newp;
 276               ++in6ailistlen;
 277             }
 278           else if (nlmh->nlmsg_type == NLMSG_DONE)
 279             /* We found the end, leave the loop.  */
 280             done = true;
 281         }
 282     }
 283   while (! done);
 284
 285   struct cached_data *result;
 286   if (seen_ipv6 && in6ailist != NULL)
 287     {
 288       result = malloc (sizeof (*result)
 289                        + in6ailistlen * sizeof (struct in6addrinfo));
 290       if (result == NULL)
 291         goto out_fail2;
 292
 293       result->timestamp = get_nl_timestamp ();
 294       result->usecnt = 2;
 295       result->seen_ipv4 = seen_ipv4;
 296       result->seen_ipv6 = true;
 297       result->in6ailen = in6ailistlen;
 298
 299       do
 300         {
 301           result->in6ai[--in6ailistlen] = in6ailist->info;
 302           struct in6ailist *next = in6ailist->next;
 303           if (in6ailist->use_malloc)
 304             free (in6ailist);
 305           in6ailist = next;
 306         }
 307       while (in6ailist != NULL);
 308     }
 309   else
 310     {
 311       atomic_add (&noai6ai_cached.usecnt, 2);
 312       noai6ai_cached.seen_ipv4 = seen_ipv4;
 313       noai6ai_cached.seen_ipv6 = seen_ipv6;
 314       result = &noai6ai_cached;
 315     }
 316
 317   if (use_malloc)
 318     free (buf);
 319   return result;
 320
 321  out_fail2:
 322   while (in6ailist != NULL)
 323     {
 324       struct in6ailist *next = in6ailist->next;
 325       if (in6ailist->use_malloc)
 326         free (in6ailist);
 327       in6ailist = next;
 328     }
 329  out_fail:
 330   if (use_malloc)
 331     free (buf);
 332   return NULL;
 333 }
 334
 335
 336 void
 337 attribute_hidden
 338 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 339             struct in6addrinfo **in6ai, size_t *in6ailen)
 340 {
 341   *in6ai = NULL;
 342   *in6ailen = 0;
 343
 344   struct cached_data *olddata = NULL;
 345   struct cached_data *data = NULL;
 346
 347   __libc_lock_lock (lock);
 348
 349   if (cache_valid_p ())
 350     {
 351       data = cache;
 352       atomic_increment (&cache->usecnt);
 353     }
 354   else
 355     {
 356       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 357
 358       if (__glibc_likely (fd >= 0))
 359         {
 360           struct sockaddr_nl nladdr;
 361           memset (&nladdr, '\0', sizeof (nladdr));
 362           nladdr.nl_family = AF_NETLINK;
 363
 364           socklen_t addr_len = sizeof (nladdr);
 365
 366           if (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 367               && __getsockname (fd, (struct sockaddr *) &nladdr,
 368                                 &addr_len) == 0)
 369             data = make_request (fd, nladdr.nl_pid);
 370
 371           close_not_cancel_no_status (fd);
 372         }
 373
 374       if (data != NULL)
 375         {
 376           olddata = cache;
 377           cache = data;
 378         }
 379     }
 380
 381   __libc_lock_unlock (lock);
 382
 383   if (data != NULL)
 384     {
 385       /* It worked.  */
 386       *seen_ipv4 = data->seen_ipv4;
 387       *seen_ipv6 = data->seen_ipv6;
 388       *in6ailen = data->in6ailen;
 389       *in6ai = data->in6ai;
 390
 391       if (olddata != NULL && olddata->usecnt > 0
 392           && atomic_add_zero (&olddata->usecnt, -1))
 393         free (olddata);
 394
 395       return;
 396     }
 397
 398   /* We cannot determine what interfaces are available.  Be
 399      pessimistic.  */
 400   *seen_ipv4 = true;
 401   *seen_ipv6 = true;
 402 }
 403
 404 /* Free the cache if it has been allocated.  */
 405 libc_freeres_fn (freecache)
 406 {
 407   if (cache)
 408     __free_in6ai (cache->in6ai);
 409 }
 410
 411 void
 412 __free_in6ai (struct in6addrinfo *ai)
 413 {
 414   if (ai != NULL)
 415     {
 416       struct cached_data *data =
 417         (struct cached_data *) ((char *) ai
 418                                 - offsetof (struct cached_data, in6ai));
 419
 420       if (atomic_add_zero (&data->usecnt, -1))
 421         {
 422           __libc_lock_lock (lock);
 423
 424           if (data->usecnt == 0)
 425             /* Still unused.  */
 426             free (data);
 427
 428           __libc_lock_unlock (lock);
 429         }
 430     }
 431 }