sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003-2013 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 <sys/socket.h>
  28
  29 #include <asm/types.h>
  30 #include <linux/netlink.h>
  31 #include <linux/rtnetlink.h>
  32
  33 #include <not-cancel.h>
  34 #include <kernel-features.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 libc_freeres_ptr (static struct cached_data *cache);
  65 __libc_lock_define_initialized (static, lock);
  66
  67
  68 #ifdef 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 #ifdef 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
 142   if (__libc_use_alloca (buf_size))
 143     buf = alloca (buf_size);
 144   else
 145     {
 146       buf = malloc (buf_size);
 147       if (buf != NULL)
 148         use_malloc = true;
 149       else
 150         goto out_fail;
 151     }
 152
 153   struct iovec iov = { buf, buf_size };
 154
 155   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
 156                                     (struct sockaddr *) &nladdr,
 157                                     sizeof (nladdr))) < 0)
 158     goto out_fail;
 159
 160   bool done = false;
 161   struct in6ailist
 162   {
 163     struct in6addrinfo info;
 164     struct in6ailist *next;
 165   } *in6ailist = NULL;
 166   size_t in6ailistlen = 0;
 167   bool seen_ipv4 = false;
 168   bool seen_ipv6 = false;
 169
 170   do
 171     {
 172       struct msghdr msg =
 173         {
 174           (void *) &nladdr, sizeof (nladdr),
 175           &iov, 1,
 176           NULL, 0,
 177           0
 178         };
 179
 180       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 181       if (read_len < 0)
 182         goto out_fail;
 183
 184       if (msg.msg_flags & MSG_TRUNC)
 185         goto out_fail;
 186
 187       struct nlmsghdr *nlmh;
 188       for (nlmh = (struct nlmsghdr *) buf;
 189            NLMSG_OK (nlmh, (size_t) read_len);
 190            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 191         {
 192           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 193               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 194             continue;
 195
 196           if (nlmh->nlmsg_type == RTM_NEWADDR)
 197             {
 198               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 199               struct rtattr *rta = IFA_RTA (ifam);
 200               size_t len = nlmh->nlmsg_len - NLMSG_LENGTH (sizeof (*ifam));
 201
 202               if (ifam->ifa_family != AF_INET
 203                   && ifam->ifa_family != AF_INET6)
 204                 continue;
 205
 206               const void *local = NULL;
 207               const void *address = NULL;
 208               while (RTA_OK (rta, len))
 209                 {
 210                   switch (rta->rta_type)
 211                     {
 212                     case IFA_LOCAL:
 213                       local = RTA_DATA (rta);
 214                       break;
 215
 216                     case IFA_ADDRESS:
 217                       address = RTA_DATA (rta);
 218                       goto out;
 219                     }
 220
 221                   rta = RTA_NEXT (rta, len);
 222                 }
 223
 224               if (local != NULL)
 225                 {
 226                   address = local;
 227                 out:
 228                   if (ifam->ifa_family == AF_INET)
 229                     {
 230                       if (*(const in_addr_t *) address
 231                           != htonl (INADDR_LOOPBACK))
 232                         seen_ipv4 = true;
 233                     }
 234                   else
 235                     {
 236                       if (!IN6_IS_ADDR_LOOPBACK (address))
 237                         seen_ipv6 = true;
 238                     }
 239                 }
 240
 241               struct in6ailist *newp = alloca (sizeof (*newp));
 242               newp->info.flags = (((ifam->ifa_flags
 243                                     & (IFA_F_DEPRECATED
 244                                        | IFA_F_OPTIMISTIC))
 245                                    ? in6ai_deprecated : 0)
 246                                   | ((ifam->ifa_flags
 247                                       & IFA_F_HOMEADDRESS)
 248                                      ? in6ai_homeaddress : 0));
 249               newp->info.prefixlen = ifam->ifa_prefixlen;
 250               newp->info.index = ifam->ifa_index;
 251               if (ifam->ifa_family == AF_INET)
 252                 {
 253                   newp->info.addr[0] = 0;
 254                   newp->info.addr[1] = 0;
 255                   newp->info.addr[2] = htonl (0xffff);
 256                   newp->info.addr[3] = *(const in_addr_t *) address;
 257                 }
 258               else
 259                 memcpy (newp->info.addr, address, sizeof (newp->info.addr));
 260               newp->next = in6ailist;
 261               in6ailist = newp;
 262               ++in6ailistlen;
 263             }
 264           else if (nlmh->nlmsg_type == NLMSG_DONE)
 265             /* We found the end, leave the loop.  */
 266             done = true;
 267         }
 268     }
 269   while (! done);
 270
 271   struct cached_data *result;
 272   if (seen_ipv6 && in6ailist != NULL)
 273     {
 274       result = malloc (sizeof (*result)
 275                        + in6ailistlen * sizeof (struct in6addrinfo));
 276       if (result == NULL)
 277         goto out_fail;
 278
 279       result->timestamp = get_nl_timestamp ();
 280       result->usecnt = 2;
 281       result->seen_ipv4 = seen_ipv4;
 282       result->seen_ipv6 = true;
 283       result->in6ailen = in6ailistlen;
 284
 285       do
 286         {
 287           result->in6ai[--in6ailistlen] = in6ailist->info;
 288           in6ailist = in6ailist->next;
 289         }
 290       while (in6ailist != NULL);
 291     }
 292   else
 293     {
 294       atomic_add (&noai6ai_cached.usecnt, 2);
 295       noai6ai_cached.seen_ipv4 = seen_ipv4;
 296       noai6ai_cached.seen_ipv6 = seen_ipv6;
 297       result = &noai6ai_cached;
 298     }
 299
 300   if (use_malloc)
 301     free (buf);
 302   return result;
 303
 304 out_fail:
 305   if (use_malloc)
 306     free (buf);
 307   return NULL;
 308 }
 309
 310
 311 void
 312 attribute_hidden
 313 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 314             struct in6addrinfo **in6ai, size_t *in6ailen)
 315 {
 316   *in6ai = NULL;
 317   *in6ailen = 0;
 318
 319   struct cached_data *olddata = NULL;
 320   struct cached_data *data = NULL;
 321
 322   __libc_lock_lock (lock);
 323
 324   if (cache_valid_p ())
 325     {
 326       data = cache;
 327       atomic_increment (&cache->usecnt);
 328     }
 329   else
 330     {
 331       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 332
 333       if (__builtin_expect (fd >= 0, 1))
 334         {
 335           struct sockaddr_nl nladdr;
 336           memset (&nladdr, '\0', sizeof (nladdr));
 337           nladdr.nl_family = AF_NETLINK;
 338
 339           socklen_t addr_len = sizeof (nladdr);
 340
 341           if (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 342               && __getsockname (fd, (struct sockaddr *) &nladdr,
 343                                 &addr_len) == 0)
 344             data = make_request (fd, nladdr.nl_pid);
 345
 346           close_not_cancel_no_status (fd);
 347         }
 348
 349       if (data != NULL)
 350         {
 351           olddata = cache;
 352           cache = data;
 353         }
 354     }
 355
 356   __libc_lock_unlock (lock);
 357
 358   if (data != NULL)
 359     {
 360       /* It worked.  */
 361       *seen_ipv4 = data->seen_ipv4;
 362       *seen_ipv6 = data->seen_ipv6;
 363       *in6ailen = data->in6ailen;
 364       *in6ai = data->in6ai;
 365
 366       if (olddata != NULL && olddata->usecnt > 0
 367           && atomic_add_zero (&olddata->usecnt, -1))
 368         free (olddata);
 369
 370       return;
 371     }
 372
 373   /* We cannot determine what interfaces are available.  Be
 374      pessimistic.  */
 375   *seen_ipv4 = true;
 376   *seen_ipv6 = true;
 377 }
 378
 379
 380 void
 381 __free_in6ai (struct in6addrinfo *ai)
 382 {
 383   if (ai != NULL)
 384     {
 385       struct cached_data *data =
 386         (struct cached_data *) ((char *) ai
 387                                 - offsetof (struct cached_data, in6ai));
 388
 389       if (atomic_add_zero (&data->usecnt, -1))
 390         {
 391           __libc_lock_lock (lock);
 392
 393           if (data->usecnt == 0)
 394             /* Still unused.  */
 395             free (data);
 396
 397           __libc_lock_unlock (lock);
 398         }
 399     }
 400 }