sysdeps/unix/sysv/linux/check_native.c

   1 /* Determine whether interfaces use native transport.  Linux version.
   2    Copyright (C) 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 <stddef.h>
  24 #include <stdint.h>
  25 #include <stdlib.h>
  26 #include <time.h>
  27 #include <unistd.h>
  28 #include <net/if.h>
  29 #include <net/if_arp.h>
  30 #include <sys/ioctl.h>
  31
  32 #include <linux/netlink.h>
  33 #include <linux/rtnetlink.h>
  34
  35 #include <not-cancel.h>
  36
  37
  38 void
  39 __check_native (uint32_t a1_index, int *a1_native,
  40                 uint32_t a2_index, int *a2_native)
  41 {
  42   int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  43
  44   struct sockaddr_nl nladdr;
  45   memset (&nladdr, '\0', sizeof (nladdr));
  46   nladdr.nl_family = AF_NETLINK;
  47
  48   socklen_t addr_len = sizeof (nladdr);
  49
  50   if (fd < 0
  51       || __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) != 0
  52       || __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) != 0)
  53     return;
  54
  55   pid_t pid = nladdr.nl_pid;
  56   struct req
  57   {
  58     struct nlmsghdr nlh;
  59     struct rtgenmsg g;
  60     /* struct rtgenmsg consists of a single byte.  This means there
  61        are three bytes of padding included in the REQ definition.
  62        We make them explicit here.  */
  63     char pad[3];
  64   } req;
  65
  66   req.nlh.nlmsg_len = sizeof (req);
  67   req.nlh.nlmsg_type = RTM_GETLINK;
  68   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  69   req.nlh.nlmsg_pid = 0;
  70   req.nlh.nlmsg_seq = time (NULL);
  71   req.g.rtgen_family = AF_UNSPEC;
  72
  73   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  74   memset (req.pad, '\0', sizeof (req.pad));
  75
  76   memset (&nladdr, '\0', sizeof (nladdr));
  77   nladdr.nl_family = AF_NETLINK;
  78
  79 #ifdef PAGE_SIZE
  80   /* Help the compiler optimize out the malloc call if PAGE_SIZE
  81      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
  82   const size_t buf_size = PAGE_SIZE;
  83 #else
  84   const size_t buf_size = __getpagesize ();
  85 #endif
  86   bool use_malloc = false;
  87   char *buf;
  88
  89   if (__libc_use_alloca (buf_size))
  90     buf = alloca (buf_size);
  91   else
  92     {
  93       buf = malloc (buf_size);
  94       if (buf != NULL)
  95         use_malloc = true;
  96       else
  97         goto out_fail;
  98     }
  99
 100   struct iovec iov = { buf, buf_size };
 101
 102   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
 103                                     (struct sockaddr *) &nladdr,
 104                                     sizeof (nladdr))) < 0)
 105     goto out_fail;
 106
 107   bool done = false;
 108   int v4fd = -1;
 109   do
 110     {
 111       struct msghdr msg =
 112         {
 113           (void *) &nladdr, sizeof (nladdr),
 114           &iov, 1,
 115           NULL, 0,
 116           0
 117         };
 118
 119       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 120       if (read_len < 0)
 121         goto out_fail;
 122
 123       if (msg.msg_flags & MSG_TRUNC)
 124         goto out_fail;
 125
 126       struct nlmsghdr *nlmh;
 127       for (nlmh = (struct nlmsghdr *) buf;
 128            NLMSG_OK (nlmh, (size_t) read_len);
 129            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 130         {
 131           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 132               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 133             continue;
 134
 135           if (nlmh->nlmsg_type == RTM_NEWLINK)
 136             {
 137               /* A RTM_NEWLINK message can have IFLA_STATS data. We need to
 138                  know the size before creating the list to allocate enough
 139                  memory.  */
 140               struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlmh);
 141               struct rtattr *rta = IFLA_RTA (ifim);
 142               size_t rtasize = IFLA_PAYLOAD (nlmh);
 143               int index = ifim->ifi_index;
 144
 145               if (a1_index == index || a2_index == index)
 146                 while (RTA_OK (rta, rtasize))
 147                   {
 148                     char *rta_data = RTA_DATA (rta);
 149                     size_t rta_payload = RTA_PAYLOAD (rta);
 150
 151                     if (rta->rta_type == IFLA_IFNAME)
 152                       {
 153                         struct ifreq ifr;
 154                         *((char *) mempcpy (ifr.ifr_name, rta_data,
 155                                             rta_payload))= '\0';
 156
 157                         if (v4fd == -1)
 158                           {
 159                             v4fd = __socket (AF_INET, SOCK_DGRAM, 0);
 160                             if (v4fd == -1)
 161                               return;
 162                           }
 163
 164                         if (__ioctl (v4fd, SIOCGIFHWADDR, &ifr) >= 0)
 165                           {
 166                             int native
 167                               = (ifr.ifr_hwaddr.sa_family != ARPHRD_TUNNEL6
 168                                  && ifr.ifr_hwaddr.sa_family != ARPHRD_TUNNEL
 169                                  && ifr.ifr_hwaddr.sa_family != ARPHRD_SIT);
 170
 171                             if (a1_index == index)
 172                               {
 173                                 *a1_native = native;
 174                                 a1_index = 0xffffffffu;
 175                               }
 176                             if (a2_index == index)
 177                               {
 178                                 *a2_native = native;
 179                                 a2_index = 0xffffffffu;
 180                               }
 181
 182                             if (a1_index == 0xffffffffu
 183                                 && a2_index == 0xffffffffu)
 184                               goto out;
 185                           }
 186                         break;
 187                       }
 188
 189                     rta = RTA_NEXT (rta, rtasize);
 190                   }
 191             }
 192           else if (nlmh->nlmsg_type == NLMSG_DONE)
 193             /* We found the end, leave the loop.  */
 194             done = true;
 195         }
 196     }
 197   while (! done);
 198
 199  out:
 200   close_not_cancel_no_status (fd);
 201   if (v4fd != -1)
 202     close_not_cancel_no_status (v4fd);
 203
 204   return;
 205
 206 out_fail:
 207   if (use_malloc)
 208     free (buf);
 209 }