sysdeps/unix/sysv/linux/check_native.c

   1 /* Determine whether interfaces use native transport.  Linux version.
   2    Copyright (C) 2007-2017 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 #include "netlinkaccess.h"
  39
  40 void
  41 __check_native (uint32_t a1_index, int *a1_native,
  42                 uint32_t a2_index, int *a2_native)
  43 {
  44   int fd = __socket (PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  45
  46   struct sockaddr_nl nladdr;
  47   memset (&nladdr, '\0', sizeof (nladdr));
  48   nladdr.nl_family = AF_NETLINK;
  49
  50   socklen_t addr_len = sizeof (nladdr);
  51
  52   if (fd < 0
  53       || __bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) != 0
  54       || __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) != 0)
  55     return;
  56
  57   pid_t pid = nladdr.nl_pid;
  58   struct req
  59   {
  60     struct nlmsghdr nlh;
  61     struct rtgenmsg g;
  62     /* struct rtgenmsg consists of a single byte.  This means there
  63        are three bytes of padding included in the REQ definition.
  64        We make them explicit here.  */
  65     char pad[3];
  66   } req;
  67
  68   req.nlh.nlmsg_len = sizeof (req);
  69   req.nlh.nlmsg_type = RTM_GETLINK;
  70   req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
  71   req.nlh.nlmsg_pid = 0;
  72   req.nlh.nlmsg_seq = time (NULL);
  73   req.g.rtgen_family = AF_UNSPEC;
  74
  75   assert (sizeof (req) - offsetof (struct req, pad) == 3);
  76   memset (req.pad, '\0', sizeof (req.pad));
  77
  78   memset (&nladdr, '\0', sizeof (nladdr));
  79   nladdr.nl_family = AF_NETLINK;
  80
  81 #ifdef PAGE_SIZE
  82   /* Help the compiler optimize out the malloc call if PAGE_SIZE
  83      is constant and smaller or equal to PTHREAD_STACK_MIN/4.  */
  84   const size_t buf_size = PAGE_SIZE;
  85 #else
  86   const size_t buf_size = __getpagesize ();
  87 #endif
  88   bool use_malloc = false;
  89   char *buf;
  90
  91   if (__libc_use_alloca (buf_size))
  92     buf = alloca (buf_size);
  93   else
  94     {
  95       buf = malloc (buf_size);
  96       if (buf != NULL)
  97         use_malloc = true;
  98       else
  99         goto out_fail;
 100     }
 101
 102   struct iovec iov = { buf, buf_size };
 103
 104   if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
 105                                     (struct sockaddr *) &nladdr,
 106                                     sizeof (nladdr))) < 0)
 107     goto out_fail;
 108
 109   bool done = false;
 110   do
 111     {
 112       struct msghdr msg =
 113         {
 114           .msg_name = (void *) &nladdr,
 115           .msg_namelen =  sizeof (nladdr),
 116           .msg_iov = &iov,
 117           .msg_iovlen = 1,
 118           .msg_control = NULL,
 119           .msg_controllen = 0,
 120           .msg_flags = 0
 121         };
 122
 123       ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
 124       __netlink_assert_response (fd, read_len);
 125       if (read_len < 0)
 126         goto out_fail;
 127
 128       if (msg.msg_flags & MSG_TRUNC)
 129         goto out_fail;
 130
 131       struct nlmsghdr *nlmh;
 132       for (nlmh = (struct nlmsghdr *) buf;
 133            NLMSG_OK (nlmh, (size_t) read_len);
 134            nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
 135         {
 136           if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
 137               || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
 138             continue;
 139
 140           if (nlmh->nlmsg_type == RTM_NEWLINK)
 141             {
 142               struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlmh);
 143               int native = (ifim->ifi_type != ARPHRD_TUNNEL6
 144                             && ifim->ifi_type != ARPHRD_TUNNEL
 145                             && ifim->ifi_type != ARPHRD_SIT);
 146
 147               if (a1_index == ifim->ifi_index)
 148                 {
 149                   *a1_native = native;
 150                   a1_index = 0xffffffffu;
 151                 }
 152               if (a2_index == ifim->ifi_index)
 153                 {
 154                   *a2_native = native;
 155                   a2_index = 0xffffffffu;
 156                 }
 157
 158               if (a1_index == 0xffffffffu
 159                   && a2_index == 0xffffffffu)
 160                 goto out;
 161             }
 162           else if (nlmh->nlmsg_type == NLMSG_DONE)
 163             /* We found the end, leave the loop.  */
 164             done = true;
 165         }
 166     }
 167   while (! done);
 168
 169  out:
 170   close_not_cancel_no_status (fd);
 171
 172   return;
 173
 174 out_fail:
 175   if (use_malloc)
 176     free (buf);
 177 }