Re: [PATCH] doc: unshare: document CLONE_NEWNET

[Lucian Adrian Grijincu <lucian.grijincu@xxxxxxxxx>]

On Mon, Oct 18, 2010 at 6:20 PM, Randy Dunlap <rdunlap@xxxxxxxxxxxx> wrote:
> Check with file originator (Janak) and man-pages (hi Michael).


I already sent a patch to man-pages:
   http://thread.gmane.org/gmane.linux.man/1724


This functionality was added at some point but no one cared enough to
update the documentation.

If you want to check that this does work, check this simple program
I've attached. It launches /bin/bash in either the current or another
network namespace. Run "ifconfig -a" in each instance. In the new
namespace you should only see a loopback device with no IP associated
(it's different from your original loopback device).

-- 
Â.
..: Lucian

#include <stdio.h>
#include <net/if.h>
#define _GNU_SOURCE
#include <sched.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

static void print_usage_exit()
{
  printf("Usage: newnetbash [-s|shared|-n|new]\n");
  printf("       -s|shared   launch bash in the same network namespace\n");
  printf("       -n|newnet   launch bash in a new network namespace\n");
  exit(1);
}

int main(int argc, char *argv[])
{
  /*
   * Unshare the network namespace.
   */

  int create_new_net = 0;

  if (argc != 2)
    print_usage_exit();

  
  if ((strcmp(argv[1], "shared") == 0) || (strcmp(argv[1], "-s") == 0))
    create_new_net = 0;
  else if ((strcmp(argv[1], "newnet") == 0) || (strcmp(argv[1], "-n") == 0))
    create_new_net = 1;
  else
    print_usage_exit();

  if (create_new_net) {
    if (unshare(CLONE_NEWNET)) {
      perror("unshare");
      return -1;
    }
  }

  execl("/bin/bash", "/bin/bash", NULL);
  return 0;
}