sysdeps/unix/sysv/linux/check_native.c

   1 /* Determine whether interfaces use native transport.  Linux version.
   2    Copyright (C) 2007-2014 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 <stddef.h>
  23 #include <stdint.h>
  24 #include <stdlib.h>
  25 #include <string.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 <asm/types.h>
  33 #include <linux/netlink.h>
  34 #include <linux/rtnetlink.h>
  35
  36 #include <not-cancel.h>
  37
  38
  39 void
  40 __check_native (uint32_t a1_index, int *a1_native,
  41                 uint32_t a2_index, int *a2_native)
  42 {
  43   int fd = __socket (PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  44
  45   struct sockaddr_nl nladdr;
  46   memset (&nladdr, '\0', sizeof (nladdr));
  47   nladdr.nl_family = AF_NETLINK;
  48
  49   socklen_t addr_len = sizeof (nladdr);
  50
  51   if (fd < 0
  52       || __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) != 0
  53       || __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) != 0)
  54     return;
  55
  56   pid_t pid = nladdr.nl_pid;
  57   struct req
  58   {
  59     struct nlmsghdr nlh;
  60     struct rtgenmsg g;
  61     /* struct rtgenmsg consists of a single byte.  This means there
  62        are three bytes of padding included in the REQ definition.
  63        We make them explicit here.  */
  64     char pad[3];
  65   } req;
  66
  67   req.nlh.nlmsg_len = sizeof (req);
  68   req.nlh.nlmsg_type = RTM_GETLINK;
  69   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  70   req.nlh.nlmsg_pid = 0;
  71   req.nlh.nlmsg_seq = time (NULL);
  72   req.g.rtgen_family = AF_UNSPEC;
  73
  74   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  75   memset (req.pad, '\0', sizeof (req.pad));
  76
  77   memset (&nladdr, '\0', sizeof (nladdr));
  78   nladdr.nl_family = AF_NETLINK;
  79
  80 #ifdef PAGE_SIZE
  81   /* Help the compiler optimize out the malloc call if PAGE_SIZE
  82      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
  83   const size_t buf_size = PAGE_SIZE;
  84 #else
  85   const size_t buf_size = __getpagesize ();
  86 #endif
  87   bool use_malloc = false;
  88   char *buf;
  89
  90   if (__libc_use_alloca (buf_size))
  91     buf = alloca (buf_size);
  92   else
  93     {
  94       buf = malloc (buf_size);
  95       if (buf != NULL)
  96         use_malloc = true;
  97       else
  98         goto out_fail;
  99     }
 100
 101   struct iovec iov = { buf, buf_size };
 102
 103   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
 104                                     (struct sockaddr *) &nladdr,
 105                                     sizeof (nladdr))) < 0)
 106     goto out_fail;
 107
 108   bool done = false;
 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               struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlmh);
 138               int native = (ifim->ifi_type != ARPHRD_TUNNEL6
 139                             && ifim->ifi_type != ARPHRD_TUNNEL
 140                             && ifim->ifi_type != ARPHRD_SIT);
 141
 142               if (a1_index == ifim->ifi_index)
 143                 {
 144                   *a1_native = native;
 145                   a1_index = 0xffffffffu;
 146                 }
 147               if (a2_index == ifim->ifi_index)
 148                 {
 149                   *a2_native = native;
 150                   a2_index = 0xffffffffu;
 151                 }
 152
 153               if (a1_index == 0xffffffffu
 154                   && a2_index == 0xffffffffu)
 155                 goto out;
 156             }
 157           else if (nlmh->nlmsg_type == NLMSG_DONE)
 158             /* We found the end, leave the loop.  */
 159             done = true;
 160         }
 161     }
 162   while (! done);
 163
 164  out:
 165   close_not_cancel_no_status (fd);
 166
 167   return;
 168
 169 out_fail:
 170   if (use_malloc)
 171     free (buf);
 172 }