1  /* Enter a network namespace.
       2     Copyright (C) 2016-2023 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  }