text: /* Enter a network namespace.
     Copyright (C) 2016-2020 Free Software Foundation, Inc.
     This file is part of the GNU C Library.
  
     The GNU C Library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.
  
     The GNU C Library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public
     License along with the GNU C Library; if not, see
     <https://www.gnu.org/licenses/>.  */
  
  #include <support/namespace.h>
  
  #include <net/if.h>
  #include <sched.h>
  #include <stdio.h>
  #include <string.h>
  #include <support/check.h>
  #include <support/xsocket.h>
  #include <support/xunistd.h>
  #include <sys/ioctl.h>
  #include <unistd.h>
  
  static bool in_uts_namespace;
  
  bool
  support_enter_network_namespace (void)
  {
  #ifdef CLONE_NEWUTS
    if (unshare (CLONE_NEWUTS) == 0)
      in_uts_namespace = true;
    else
      printf ("warning: unshare (CLONE_NEWUTS) failed: %m\n");
  #endif
  
  #ifdef CLONE_NEWNET
    if (unshare (CLONE_NEWNET) == 0)
      {
        /* Bring up the loopback interface.  */
        int fd = xsocket (AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
        struct ifreq req;
        strcpy (req.ifr_name, "lo");
        TEST_VERIFY_EXIT (ioctl (fd, SIOCGIFFLAGS, &req) == 0);
        bool already_up = req.ifr_flags & IFF_UP;
        if (already_up)
          /* This means that we likely have not achieved isolation from
             the parent namespace.  */
          printf ("warning: loopback interface already exists"
                  " in new network namespace\n");
        else
          {
            req.ifr_flags |= IFF_UP | IFF_RUNNING;
            TEST_VERIFY_EXIT (ioctl (fd, SIOCSIFFLAGS, &req) == 0);
          }
        xclose (fd);
  
        return !already_up;
      }
  #endif
    printf ("warning: could not enter network namespace\n");
    return false;
  }
  
  bool
  support_in_uts_namespace (void)
  {
    return in_uts_namespace;
  }
  