support/support_enter_network_namespace.c

   1 /* Enter a network namespace.
   2    Copyright (C) 2016-2022 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <support/namespace.h>
  20
  21 #include <net/if.h>
  22 #include <sched.h>
  23 #include <stdio.h>
  24 #include <string.h>
  25 #include <support/check.h>
  26 #include <support/xsocket.h>
  27 #include <support/xunistd.h>
  28 #include <sys/ioctl.h>
  29 #include <unistd.h>
  30
  31 static bool in_uts_namespace;
  32
  33 bool
  34 support_enter_network_namespace (void)
  35 {
  36 #ifdef CLONE_NEWUTS
  37   if (unshare (CLONE_NEWUTS) == 0)
  38     in_uts_namespace = true;
  39   else
  40     printf ("warning: unshare (CLONE_NEWUTS) failed: %m\n");
  41 #endif
  42
  43 #ifdef CLONE_NEWNET
  44   if (unshare (CLONE_NEWNET) == 0)
  45     {
  46       /* Bring up the loopback interface.  */
  47       int fd = xsocket (AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  48       struct ifreq req;
  49       strcpy (req.ifr_name, "lo");
  50       TEST_VERIFY_EXIT (ioctl (fd, SIOCGIFFLAGS, &req) == 0);
  51       bool already_up = req.ifr_flags & IFF_UP;
  52       if (already_up)
  53         /* This means that we likely have not achieved isolation from
  54            the parent namespace.  */
  55         printf ("warning: loopback interface already exists"
  56                 " in new network namespace\n");
  57       else
  58         {
  59           req.ifr_flags |= IFF_UP | IFF_RUNNING;
  60           TEST_VERIFY_EXIT (ioctl (fd, SIOCSIFFLAGS, &req) == 0);
  61         }
  62       xclose (fd);
  63
  64       return !already_up;
  65     }
  66 #endif
  67   printf ("warning: could not enter network namespace\n");
  68   return false;
  69 }
  70
  71 bool
  72 support_in_uts_namespace (void)
  73 {
  74   return in_uts_namespace;
  75 }