sysdeps/unix/sysv/linux/check_pf.c

   1 /* Determine protocol families for which interfaces exist.  Linux version.
   2    Copyright (C) 2003, 2006, 2007 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_TEMPORARY
  39 # define IFA_F_TEMPORARY IFA_F_SECONDARY
  40 #endif
  41 #ifndef IFA_F_HOMEADDRESS
  42 # define IFA_F_HOMEADDRESS 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
 143               switch (ifam->ifa_family)
 144                 {
 145                 case AF_INET:
 146                   *seen_ipv4 = true;
 147                   break;
 148                 case AF_INET6:
 149                   *seen_ipv6 = true;
 150
 151                   if (ifam->ifa_flags & (IFA_F_DEPRECATED
 152                                          | IFA_F_TEMPORARY
 153                                          | IFA_F_HOMEADDRESS))
 154                     {
 155                       struct rtattr *rta = IFA_RTA (ifam);
 156                       size_t len = (nlmh->nlmsg_len
 157                                     - NLMSG_LENGTH (sizeof (*ifam)));
 158                       void *local = NULL;
 159                       void *address = NULL;
 160                       while (RTA_OK (rta, len))
 161                         {
 162                           switch (rta->rta_type)
 163                             {
 164                             case IFA_LOCAL:
 165                               local = RTA_DATA (rta);
 166                               break;
 167
 168                             case IFA_ADDRESS:
 169                               address = RTA_DATA (rta);
 170                               break;
 171                             }
 172
 173                           rta = RTA_NEXT (rta, len);
 174                         }
 175
 176                       struct in6ailist *newp = alloca (sizeof (*newp));
 177                       newp->info.flags = (((ifam->ifa_flags & IFA_F_DEPRECATED)
 178                                            ? in6ai_deprecated : 0)
 179                                           | ((ifam->ifa_flags
 180                                               & IFA_F_TEMPORARY)
 181                                              ? in6ai_temporary : 0)
 182                                           | ((ifam->ifa_flags
 183                                               & IFA_F_HOMEADDRESS)
 184                                              ? in6ai_homeaddress : 0));
 185                       memcpy (newp->info.addr, address ?: local,
 186                               sizeof (newp->info.addr));
 187                       newp->next = in6ailist;
 188                       in6ailist = newp;
 189                       ++in6ailistlen;
 190                     }
 191                   break;
 192                 default:
 193                   /* Ignore.  */
 194                   break;
 195                 }
 196             }
 197           else if (nlmh->nlmsg_type == NLMSG_DONE)
 198             /* We found the end, leave the loop.  */
 199             done = true;
 200         }
 201     }
 202   while (! done);
 203
 204   close_not_cancel_no_status (fd);
 205
 206   if (in6ailist != NULL)
 207     {
 208       *in6ai = malloc (in6ailistlen * sizeof (**in6ai));
 209       if (*in6ai == NULL)
 210         goto out_fail;
 211
 212       *in6ailen = in6ailistlen;
 213
 214       do
 215         {
 216           (*in6ai)[--in6ailistlen] = in6ailist->info;
 217           in6ailist = in6ailist->next;
 218         }
 219       while (in6ailist != NULL);
 220     }
 221
 222   if (use_malloc)
 223     free (buf);
 224   return 0;
 225
 226 out_fail:
 227   if (use_malloc)
 228     free (buf);
 229   return -1;
 230 }
 231
 232
 233 /* We don't know if we have NETLINK support compiled in in our
 234    Kernel.  */
 235 #if __ASSUME_NETLINK_SUPPORT == 0
 236 /* Define in ifaddrs.h.  */
 237 extern int __no_netlink_support attribute_hidden;
 238 #else
 239 # define __no_netlink_support 0
 240 #endif
 241
 242
 243 void
 244 attribute_hidden
 245 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 246             struct in6addrinfo **in6ai, size_t *in6ailen)
 247 {
 248   *in6ai = NULL;
 249   *in6ailen = 0;
 250
 251   if (! __no_netlink_support)
 252     {
 253       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 254
 255       struct sockaddr_nl nladdr;
 256       memset (&nladdr, '\0', sizeof (nladdr));
 257       nladdr.nl_family = AF_NETLINK;
 258
 259       socklen_t addr_len = sizeof (nladdr);
 260
 261       if (fd >= 0
 262           && __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 263           && __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) == 0
 264           && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6,
 265                            in6ai, in6ailen) == 0)
 266         /* It worked.  */
 267         return;
 268
 269       if (fd >= 0)
 270         __close (fd);
 271
 272 #if __ASSUME_NETLINK_SUPPORT == 0
 273       /* Remember that there is no netlink support.  */
 274       __no_netlink_support = 1;
 275 #else
 276       /* We cannot determine what interfaces are available.  Be
 277          pessimistic.  */
 278       *seen_ipv4 = true;
 279       *seen_ipv6 = true;
 280 #endif
 281     }
 282
 283 #if __ASSUME_NETLINK_SUPPORT == 0
 284   /* No netlink.  Get the interface list via getifaddrs.  */
 285   struct ifaddrs *ifa = NULL;
 286   if (getifaddrs (&ifa) != 0)
 287     {
 288       /* We cannot determine what interfaces are available.  Be
 289          pessimistic.  */
 290       *seen_ipv4 = true;
 291       *seen_ipv6 = true;
 292       return;
 293     }
 294
 295   struct ifaddrs *runp;
 296   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 297     if (runp->ifa_addr->sa_family == PF_INET)
 298       *seen_ipv4 = true;
 299     else if (runp->ifa_addr->sa_family == PF_INET6)
 300       *seen_ipv6 = true;
 301
 302   (void) freeifaddrs (ifa);
 303 #endif
 304 }