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 <not-cancel.h>
  31 #include <kernel-features.h>
  32
  33 #include "netlinkaccess.h"
  34
  35 #ifndef IFA_F_HOMEADDRESS
  36 # define IFA_F_HOMEADDRESS 0
  37 #endif
  38 #ifndef IFA_F_OPTIMISTIC
  39 # define IFA_F_OPTIMISTIC 0
  40 #endif
  41
  42
  43 static int
  44 make_request (int fd, pid_t pid, bool *seen_ipv4, bool *seen_ipv6,
  45               struct in6addrinfo **in6ai, size_t *in6ailen)
  46 {
  47   struct req
  48   {
  49     struct nlmsghdr nlh;
  50     struct rtgenmsg g;
  51     /* struct rtgenmsg consists of a single byte.  This means there
  52        are three bytes of padding included in the REQ definition.
  53        We make them explicit here.  */
  54     char pad[3];
  55   } req;
  56   struct sockaddr_nl nladdr;
  57
  58   req.nlh.nlmsg_len = sizeof (req);
  59   req.nlh.nlmsg_type = RTM_GETADDR;
  60   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  61   req.nlh.nlmsg_pid = 0;
  62   req.nlh.nlmsg_seq = time (NULL);
  63   req.g.rtgen_family = AF_UNSPEC;
  64
  65   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  66   memset (req.pad, '\0', sizeof (req.pad));
  67
  68   memset (&nladdr, '\0', sizeof (nladdr));
  69   nladdr.nl_family = AF_NETLINK;
  70
  71 #ifdef PAGE_SIZE
  72   /* Help the compiler optimize out the malloc call if PAGE_SIZE
  73      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
  74   const size_t buf_size = PAGE_SIZE;
  75 #else
  76   const size_t buf_size = __getpagesize ();
  77 #endif
  78   bool use_malloc = false;
  79   char *buf;
  80
  81   if (__libc_use_alloca (buf_size))
  82     buf = alloca (buf_size);
  83   else
  84     {
  85       buf = malloc (buf_size);
  86       if (buf != NULL)
  87         use_malloc = true;
  88       else
  89         goto out_fail;
  90     }
  91
  92   struct iovec iov = { buf, buf_size };
  93
  94   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
  95                                     (struct sockaddr *) &nladdr,
  96                                     sizeof (nladdr))) < 0)
  97     goto out_fail;
  98
  99   *seen_ipv4 = false;
 100   *seen_ipv6 = false;
 101
 102   bool done = false;
 103   struct in6ailist
 104   {
 105     struct in6addrinfo info;
 106     struct in6ailist *next;
 107   } *in6ailist = NULL;
 108   size_t in6ailistlen = 0;
 109
 110   do
 111     {
 112       struct msghdr msg =
 113         {
 114           (void *) &nladdr, sizeof (nladdr),
 115           &iov, 1,
 116           NULL, 0,
 117           0
 118         };
 119
 120       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 121       if (read_len < 0)
 122         goto out_fail;
 123
 124       if (msg.msg_flags & MSG_TRUNC)
 125         goto out_fail;
 126
 127       struct nlmsghdr *nlmh;
 128       for (nlmh = (struct nlmsghdr *) buf;
 129            NLMSG_OK (nlmh, (size_t) read_len);
 130            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 131         {
 132           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 133               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 134             continue;
 135
 136           if (nlmh->nlmsg_type == RTM_NEWADDR)
 137             {
 138               struct ifaddrmsg *ifam = (struct ifaddrmsg *) NLMSG_DATA (nlmh);
 139               struct rtattr *rta = IFA_RTA (ifam);
 140               size_t len = nlmh->nlmsg_len - NLMSG_LENGTH (sizeof (*ifam));
 141
 142               if (ifam->ifa_family != AF_INET
 143                   && ifam->ifa_family != AF_INET6)
 144                 continue;
 145
 146               const void *local = NULL;
 147               const void *address = NULL;
 148               while (RTA_OK (rta, len))
 149                 {
 150                   switch (rta->rta_type)
 151                     {
 152                     case IFA_LOCAL:
 153                       local = RTA_DATA (rta);
 154                       break;
 155
 156                     case IFA_ADDRESS:
 157                       address = RTA_DATA (rta);
 158                       goto out;
 159                     }
 160
 161                   rta = RTA_NEXT (rta, len);
 162                 }
 163
 164               if (local != NULL)
 165                 {
 166                   address = local;
 167                 out:
 168                   if (ifam->ifa_family != AF_INET)
 169                     {
 170                       if (*(const in_addr_t *) address
 171                           != htonl (INADDR_LOOPBACK))
 172                         *seen_ipv4 = true;
 173                     }
 174                   else
 175                     {
 176                       if (!IN6_IS_ADDR_LOOPBACK (address))
 177                         *seen_ipv6 = true;
 178                     }
 179                 }
 180
 181               struct in6ailist *newp = alloca (sizeof (*newp));
 182               newp->info.flags = (((ifam->ifa_flags
 183                                     & (IFA_F_DEPRECATED
 184                                        | IFA_F_OPTIMISTIC))
 185                                    ? in6ai_deprecated : 0)
 186                                   | ((ifam->ifa_flags
 187                                       & IFA_F_HOMEADDRESS)
 188                                      ? in6ai_homeaddress : 0));
 189               newp->info.prefixlen = ifam->ifa_prefixlen;
 190               newp->info.index = ifam->ifa_index;
 191               if (ifam->ifa_family == AF_INET)
 192                 {
 193                   newp->info.addr[0] = 0;
 194                   newp->info.addr[1] = 0;
 195                   newp->info.addr[2] = htonl (0xffff);
 196                   newp->info.addr[3] = *(const in_addr_t *) address;
 197                 }
 198               else
 199                 memcpy (newp->info.addr, address, sizeof (newp->info.addr));
 200               newp->next = in6ailist;
 201               in6ailist = newp;
 202               ++in6ailistlen;
 203             }
 204           else if (nlmh->nlmsg_type == NLMSG_DONE)
 205             /* We found the end, leave the loop.  */
 206             done = true;
 207         }
 208     }
 209   while (! done);
 210
 211   close_not_cancel_no_status (fd);
 212
 213   if (*seen_ipv6 && in6ailist != NULL)
 214     {
 215       *in6ai = malloc (in6ailistlen * sizeof (**in6ai));
 216       if (*in6ai == NULL)
 217         goto out_fail;
 218
 219       *in6ailen = in6ailistlen;
 220
 221       do
 222         {
 223           (*in6ai)[--in6ailistlen] = in6ailist->info;
 224           in6ailist = in6ailist->next;
 225         }
 226       while (in6ailist != NULL);
 227     }
 228
 229   if (use_malloc)
 230     free (buf);
 231   return 0;
 232
 233 out_fail:
 234   if (use_malloc)
 235     free (buf);
 236   return -1;
 237 }
 238
 239
 240 /* We don't know if we have NETLINK support compiled in in our
 241    Kernel.  */
 242 #if __ASSUME_NETLINK_SUPPORT == 0
 243 /* Define in ifaddrs.h.  */
 244 extern int __no_netlink_support attribute_hidden;
 245 #else
 246 # define __no_netlink_support 0
 247 #endif
 248
 249
 250 void
 251 attribute_hidden
 252 __check_pf (bool *seen_ipv4, bool *seen_ipv6,
 253             struct in6addrinfo **in6ai, size_t *in6ailen)
 254 {
 255   *in6ai = NULL;
 256   *in6ailen = 0;
 257
 258   if (! __no_netlink_support)
 259     {
 260       int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 261
 262       struct sockaddr_nl nladdr;
 263       memset (&nladdr, '\0', sizeof (nladdr));
 264       nladdr.nl_family = AF_NETLINK;
 265
 266       socklen_t addr_len = sizeof (nladdr);
 267
 268       if (fd >= 0
 269           && __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) == 0
 270           && __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) == 0
 271           && make_request (fd, nladdr.nl_pid, seen_ipv4, seen_ipv6,
 272                            in6ai, in6ailen) == 0)
 273         /* It worked.  */
 274         return;
 275
 276       if (fd >= 0)
 277         __close (fd);
 278
 279 #if __ASSUME_NETLINK_SUPPORT == 0
 280       /* Remember that there is no netlink support.  */
 281       __no_netlink_support = 1;
 282 #else
 283       /* We cannot determine what interfaces are available.  Be
 284          pessimistic.  */
 285       *seen_ipv4 = true;
 286       *seen_ipv6 = true;
 287 #endif
 288     }
 289
 290 #if __ASSUME_NETLINK_SUPPORT == 0
 291   /* No netlink.  Get the interface list via getifaddrs.  */
 292   struct ifaddrs *ifa = NULL;
 293   if (getifaddrs (&ifa) != 0)
 294     {
 295       /* We cannot determine what interfaces are available.  Be
 296          pessimistic.  */
 297       *seen_ipv4 = true;
 298       *seen_ipv6 = true;
 299       return;
 300     }
 301
 302   struct ifaddrs *runp;
 303   for (runp = ifa; runp != NULL; runp = runp->ifa_next)
 304     if (runp->ifa_addr->sa_family == PF_INET)
 305       *seen_ipv4 = true;
 306     else if (runp->ifa_addr->sa_family == PF_INET6)
 307       *seen_ipv6 = true;
 308
 309   (void) freeifaddrs (ifa);
 310 #endif
 311 }