sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003, 2006, 2007, 2008 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <ifaddrs.h>
  23 #include <netdb.h>
  24 #include <stddef.h>
  25 #include <string.h>
  26 #include <time.h>
  27 #include <unistd.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 <kernel-features.h>
  36
  37
  38 #ifndef IFA_F_HOMEADDRESS
  39 # define IFA_F_HOMEADDRESS 0
  40 #endif
  41 #ifndef IFA_F_OPTIMISTIC
  42 # define IFA_F_OPTIMISTIC 0
  43 #endif
  44
  45
  46 static int
  47 make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
  48               struct in6addrinfo **in6ai, size_t *in6ailen)
  49 {
  50   struct req
  51   {
  52     struct nlmsghdr nlh;
  53     struct rtgenmsg g;
  54     /* struct rtgenmsg consists of a single byte.  This means there
  55        are three bytes of padding included in the REQ definition.
  56        We make them explicit here.  */
  57     char pad[3];
  58   } req;
  59   struct sockaddr_nl nladdr;
  60
  61   req.nlh.nlmsg_len = sizeof (req);
  62   req.nlh.nlmsg_type = RTM_GETADDR;
  63   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  64   req.nlh.nlmsg_pid = 0;
  65   req.nlh.nlmsg_seq = time (NULL);
  66   req.g.rtgen_family = AF_UNSPEC;
  67
  68   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  69   memset (req.pad, '\0', sizeof (req.pad));
  70
  71   memset (&nladdr, '\0', sizeof (nladdr));
  72   nladdr.nl_family = AF_NETLINK;
  73
  74 #ifdef PAGE_SIZE
  75   /* Help the compiler optimize out the malloc call if PAGE_SIZE
  76      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
  77   const size_t buf_size = PAGE_SIZE;
  78 #else
  79   const size_t buf_size = __getpagesize ();
  80 #endif
  81   bool use_malloc = false;
  82   char *buf;
  83
  84   if (__libc_use_alloca (buf_size))
  85     buf = alloca (buf_size);
  86   else
  87     {
  88       buf = malloc (buf_size);
  89       if (buf != NULL)
  90         use_malloc = true;
  91       else
  92         goto out_fail;
  93     }
  94
  95   struct iovec iov = { buf, buf_size };
  96
  97   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
  98                                     (struct sockaddr *) &nladdr,
  99                                     sizeof (nladdr))) < 0)
 100     goto out_fail;
 101
 102   *seen_ipv4 = false;
 103   *seen_ipv6 = false;
 104
 105   bool done = false;
 106   struct in6ailist
 107   {
 108     struct in6addrinfo info;
 109     struct in6ailist *next;
 110   } *in6ailist = NULL;
 111   size_t in6ailistlen = 0;
 112
 113   do
 114     {
 115       struct msghdr msg =
 116         {
 117           (void *) &nladdr, sizeof (nladdr),
 118           &iov, 1,
 119           NULL, 0,
 120           0
 121         };
 122
 123       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 124       if (read_len < 0)
 125         goto out_fail;
 126
 127       if (msg.msg_flags & MSG_TRUNC)
 128         goto out_fail;
 129
 130       struct nlmsghdr *nlmh;
 131       for (nlmh = (struct nlmsghdr *) buf;
 132            NLMSG_OK (nlmh, (size_t) read_len);
 133            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 134         {
 135           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 136               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 137             continue;
 138
 139           if (nlmh->nlmsg_type == RTM_NEWADDR)
 140             {
 141               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 142               struct rtattr *rta = IFA_RTA (ifam);
 143               size_t len = nlmh->nlmsg_len - NLMSG_LENGTH (sizeof (*ifam));
 144
 145               if (ifam->ifa_family != AF_INET
 146                   && ifam->ifa_family != AF_INET6)
 147                 continue;
 148
 149               const void *local = NULL;
 150               const void *address = NULL;
 151               while (RTA_OK (rta, len))
 152                 {
 153                   switch (rta->rta_type)
 154                     {
 155                     case IFA_LOCAL:
 156                       local = RTA_DATA (rta);
 157                       break;
 158
 159                     case IFA_ADDRESS:
 160                       address = RTA_DATA (rta);
 161                       goto out;
 162                     }
 163
 164                   rta = RTA_NEXT (rta, len);
 165                 }
 166
 167               if (local != NULL)
 168                 {
 169                   address = local;
 170                 out:
 171                   if (ifam->ifa_family == AF_INET)
 172                     {
 173                       if (*(const in_addr_t *) address
 174                           != htonl (INADDR_LOOPBACK))
 175                         *seen_ipv4 = true;
 176                     }
 177                   else
 178                     {
 179                       if (!IN6_IS_ADDR_LOOPBACK (address))
 180                         *seen_ipv6 = true;
 181                     }
 182                 }
 183
 184               struct in6ailist *newp = alloca (sizeof (*newp));
 185               newp->info.flags = (((ifam->ifa_flags
 186                                     & (IFA_F_DEPRECATED
 187                                        | IFA_F_OPTIMISTIC))
 188                                    ? in6ai_deprecated : 0)
 189                                   | ((ifam->ifa_flags
 190                                       & IFA_F_HOMEADDRESS)
 191                                      ? in6ai_homeaddress : 0));
 192               newp->info.prefixlen = ifam->ifa_prefixlen;
 193               newp->info.index = ifam->ifa_index;
 194               if (ifam->ifa_family == AF_INET)
 195                 {
 196                   newp->info.addr[0] = 0;
 197                   newp->info.addr[1] = 0;
 198                   newp->info.addr[2] = htonl (0xffff);
 199                   newp->info.addr[3] = *(const in_addr_t *) address;
 200                 }
 201               else
 202                 memcpy (newp->info.addr, address, sizeof (newp->info.addr));
 203               newp->next = in6ailist;
 204               in6ailist = newp;
 205               ++in6ailistlen;
 206             }
 207           else if (nlmh->nlmsg_type == NLMSG_DONE)
 208             /* We found the end, leave the loop.  */
 209             done = true;
 210         }
 211     }
 212   while (! done);
 213
 214   close_not_cancel_no_status (fd);
 215
 216   if (*seen_ipv6 && in6ailist != NULL)
 217     {
 218       *in6ai = malloc (in6ailistlen * sizeof (**in6ai));
 219       if (*in6ai == NULL)
 220         goto out_fail;
 221
 222       *in6ailen = in6ailistlen;
 223
 224       do
 225         {
 226           (*in6ai)[--in6ailistlen] = in6ailist->info;
 227           in6ailist = in6ailist->next;
 228         }
 229       while (in6ailist != NULL);
 230     }
 231
 232   if (use_malloc)
 233     free (buf);
 234   return 0;
 235
 236 out_fail:
 237   if (use_malloc)
 238     free (buf);
 239   return -1;
 240 }
 241
 242
 243 /* We don't know if we have NETLINK support compiled in in our
 244    Kernel.  */
 245 #if __ASSUME_NETLINK_SUPPORT == 0
 246 /* Define in ifaddrs.h.  */
 247 extern int __no_netlink_support attribute_hidden;
 248 #else
 249 # define __no_netlink_support 0
 250 #endif
 251
 252
 253 void
 254 attribute_hidden
 255 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 256             struct in6addrinfo **in6ai, size_t *in6ailen)
 257 {
 258   *in6ai = NULL;
 259   *in6ailen = 0;
 260
 261   if (! __no_netlink_support)
 262     {
 263       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 264
 265       struct sockaddr_nl nladdr;
 266       memset (&nladdr, '\0', sizeof (nladdr));
 267       nladdr.nl_family = AF_NETLINK;
 268
 269       socklen_t addr_len = sizeof (nladdr);
 270
 271       if (fd >= 0
 272           && __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 273           && __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) == 0
 274           && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6,
 275                            in6ai, in6ailen) == 0)
 276         /* It worked.  */
 277         return;
 278
 279       if (fd >= 0)
 280         __close (fd);
 281
 282 #if __ASSUME_NETLINK_SUPPORT == 0
 283       /* Remember that there is no netlink support.  */
 284       __no_netlink_support = 1;
 285 #else
 286       /* We cannot determine what interfaces are available.  Be
 287          pessimistic.  */
 288       *seen_ipv4 = true;
 289       *seen_ipv6 = true;
 290 #endif
 291     }
 292
 293 #if __ASSUME_NETLINK_SUPPORT == 0
 294   /* No netlink.  Get the interface list via getifaddrs.  */
 295   struct ifaddrs *ifa = NULL;
 296   if (getifaddrs (&ifa) != 0)
 297     {
 298       /* We cannot determine what interfaces are available.  Be
 299          pessimistic.  */
 300       *seen_ipv4 = true;
 301       *seen_ipv6 = true;
 302       return;
 303     }
 304
 305   struct ifaddrs *runp;
 306   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 307     if (runp->ifa_addr->sa_family == PF_INET)
 308       *seen_ipv4 = true;
 309     else if (runp->ifa_addr->sa_family == PF_INET6)
 310       *seen_ipv6 = true;
 311
 312   (void) freeifaddrs (ifa);
 313 #endif
 314 }