sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003, 2006-2008, 2010, 2011 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 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
  82 static struct cached_data *
  83 make_request (int fd, pid_t pid)
  84 {
  85   struct req
  86   {
  87     struct nlmsghdr nlh;
  88     struct rtgenmsg g;
  89     /* struct rtgenmsg consists of a single byte.  This means there
  90        are three bytes of padding included in the REQ definition.
  91        We make them explicit here.  */
  92     char pad[3];
  93   } req;
  94   struct sockaddr_nl nladdr;
  95
  96   req.nlh.nlmsg_len = sizeof (req);
  97   req.nlh.nlmsg_type = RTM_GETADDR;
  98   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  99   req.nlh.nlmsg_pid = 0;
 100   req.nlh.nlmsg_seq = time (NULL);
 101   req.g.rtgen_family = AF_UNSPEC;
 102
 103   assert (sizeof (req) - offsetof (struct req, pad) == 3);
 104   memset (req.pad, '\0', sizeof (req.pad));
 105
 106   memset (&nladdr, '\0', sizeof (nladdr));
 107   nladdr.nl_family = AF_NETLINK;
 108
 109 #ifdef PAGE_SIZE
 110   /* Help the compiler optimize out the malloc call if PAGE_SIZE
 111      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
 112   const size_t buf_size = PAGE_SIZE;
 113 #else
 114   const size_t buf_size = __getpagesize ();
 115 #endif
 116   bool use_malloc = false;
 117   char *buf;
 118
 119   if (__libc_use_alloca (buf_size))
 120     buf = alloca (buf_size);
 121   else
 122     {
 123       buf = malloc (buf_size);
 124       if (buf != NULL)
 125         use_malloc = true;
 126       else
 127         goto out_fail;
 128     }
 129
 130   struct iovec iov = { buf, buf_size };
 131
 132   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
 133                                     (struct sockaddr *) &nladdr,
 134                                     sizeof (nladdr))) < 0)
 135     goto out_fail;
 136
 137   bool done = false;
 138   struct in6ailist
 139   {
 140     struct in6addrinfo info;
 141     struct in6ailist *next;
 142   } *in6ailist = NULL;
 143   size_t in6ailistlen = 0;
 144   bool seen_ipv4 = false;
 145   bool seen_ipv6 = false;
 146
 147   do
 148     {
 149       struct msghdr msg =
 150         {
 151           (void *) &nladdr, sizeof (nladdr),
 152           &iov, 1,
 153           NULL, 0,
 154           0
 155         };
 156
 157       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 158       if (read_len < 0)
 159         goto out_fail;
 160
 161       if (msg.msg_flags & MSG_TRUNC)
 162         goto out_fail;
 163
 164       struct nlmsghdr *nlmh;
 165       for (nlmh = (struct nlmsghdr *) buf;
 166            NLMSG_OK (nlmh, (size_t) read_len);
 167            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 168         {
 169           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 170               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 171             continue;
 172
 173           if (nlmh->nlmsg_type == RTM_NEWADDR)
 174             {
 175               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 176               struct rtattr *rta = IFA_RTA (ifam);
 177               size_t len = nlmh->nlmsg_len - NLMSG_LENGTH (sizeof (*ifam));
 178
 179               if (ifam->ifa_family != AF_INET
 180                   && ifam->ifa_family != AF_INET6)
 181                 continue;
 182
 183               const void *local = NULL;
 184               const void *address = NULL;
 185               while (RTA_OK (rta, len))
 186                 {
 187                   switch (rta->rta_type)
 188                     {
 189                     case IFA_LOCAL:
 190                       local = RTA_DATA (rta);
 191                       break;
 192
 193                     case IFA_ADDRESS:
 194                       address = RTA_DATA (rta);
 195                       goto out;
 196                     }
 197
 198                   rta = RTA_NEXT (rta, len);
 199                 }
 200
 201               if (local != NULL)
 202                 {
 203                   address = local;
 204                 out:
 205                   if (ifam->ifa_family == AF_INET)
 206                     {
 207                       if (*(const in_addr_t *) address
 208                           != htonl (INADDR_LOOPBACK))
 209                         seen_ipv4 = true;
 210                     }
 211                   else
 212                     {
 213                       if (!IN6_IS_ADDR_LOOPBACK (address))
 214                         seen_ipv6 = true;
 215                     }
 216                 }
 217
 218               struct in6ailist *newp = alloca (sizeof (*newp));
 219               newp->info.flags = (((ifam->ifa_flags
 220                                     & (IFA_F_DEPRECATED
 221                                        | IFA_F_OPTIMISTIC))
 222                                    ? in6ai_deprecated : 0)
 223                                   | ((ifam->ifa_flags
 224                                       & IFA_F_HOMEADDRESS)
 225                                      ? in6ai_homeaddress : 0));
 226               newp->info.prefixlen = ifam->ifa_prefixlen;
 227               newp->info.index = ifam->ifa_index;
 228               if (ifam->ifa_family == AF_INET)
 229                 {
 230                   newp->info.addr[0] = 0;
 231                   newp->info.addr[1] = 0;
 232                   newp->info.addr[2] = htonl (0xffff);
 233                   newp->info.addr[3] = *(const in_addr_t *) address;
 234                 }
 235               else
 236                 memcpy (newp->info.addr, address, sizeof (newp->info.addr));
 237               newp->next = in6ailist;
 238               in6ailist = newp;
 239               ++in6ailistlen;
 240             }
 241           else if (nlmh->nlmsg_type == NLMSG_DONE)
 242             /* We found the end, leave the loop.  */
 243             done = true;
 244         }
 245     }
 246   while (! done);
 247
 248   struct cached_data *result;
 249   if (seen_ipv6 && in6ailist != NULL)
 250     {
 251       result = malloc (sizeof (*result)
 252                        + in6ailistlen * sizeof (struct in6addrinfo));
 253       if (result == NULL)
 254         goto out_fail;
 255
 256 #ifdef IS_IN_nscd
 257       result->timestamp = nl_timestamp;
 258 #else
 259       result->timestamp = __nscd_get_nl_timestamp ();
 260 #endif
 261       result->usecnt = 2;
 262       result->seen_ipv4 = seen_ipv4;
 263       result->seen_ipv6 = true;
 264       result->in6ailen = in6ailistlen;
 265
 266       do
 267         {
 268           result->in6ai[--in6ailistlen] = in6ailist->info;
 269           in6ailist = in6ailist->next;
 270         }
 271       while (in6ailist != NULL);
 272     }
 273   else
 274     {
 275       atomic_add (&noai6ai_cached.usecnt, 2);
 276       noai6ai_cached.seen_ipv4 = seen_ipv4;
 277       noai6ai_cached.seen_ipv6 = seen_ipv6;
 278       result = &noai6ai_cached;
 279     }
 280
 281   if (use_malloc)
 282     free (buf);
 283   return result;
 284
 285 out_fail:
 286   if (use_malloc)
 287     free (buf);
 288   return NULL;
 289 }
 290
 291
 292 /* We don't know if we have NETLINK support compiled into our
 293    Kernel.  */
 294 #if __ASSUME_NETLINK_SUPPORT == 0
 295 /* Define in ifaddrs.h.  */
 296 extern int __no_netlink_support attribute_hidden;
 297 #else
 298 # define __no_netlink_support 0
 299 #endif
 300
 301
 302 void
 303 attribute_hidden
 304 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 305             struct in6addrinfo **in6ai, size_t *in6ailen)
 306 {
 307   *in6ai = NULL;
 308   *in6ailen = 0;
 309
 310   if (! __no_netlink_support)
 311     {
 312       struct cached_data *olddata = NULL;
 313       struct cached_data *data = NULL;
 314
 315       __libc_lock_lock (lock);
 316
 317 #ifdef IS_IN_nscd
 318 # define cache_valid() nl_timestamp != 0 && cache->timestamp == nl_timestamp
 319 #else
 320 # define cache_valid() \
 321       ({ uint32_t val = __nscd_get_nl_timestamp ();                           \
 322          val != 0 && cache->timestamp == val; })
 323 #endif
 324       if (cache != NULL && cache_valid ())
 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 #if __ASSUME_NETLINK_SUPPORT == 0
 374       /* Remember that there is no netlink support.  */
 375       __no_netlink_support = 1;
 376 #else
 377       /* We cannot determine what interfaces are available.  Be
 378          pessimistic.  */
 379       *seen_ipv4 = true;
 380       *seen_ipv6 = true;
 381 #endif
 382     }
 383
 384 #if __ASSUME_NETLINK_SUPPORT == 0
 385   /* No netlink.  Get the interface list via getifaddrs.  */
 386   struct ifaddrs *ifa = NULL;
 387   if (getifaddrs (&ifa) != 0)
 388     {
 389       /* We cannot determine what interfaces are available.  Be
 390          pessimistic.  */
 391       *seen_ipv4 = true;
 392       *seen_ipv6 = true;
 393       return;
 394     }
 395
 396   struct ifaddrs *runp;
 397   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 398     if (runp->ifa_addr != NULL)
 399       {
 400         if (runp->ifa_addr->sa_family == PF_INET)
 401           *seen_ipv4 = true;
 402         else if (runp->ifa_addr->sa_family == PF_INET6)
 403           *seen_ipv6 = true;
 404       }
 405
 406   (void) freeifaddrs (ifa);
 407 #endif
 408 }
 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 }