Marc Lehmann > Linux-Clone-0.01 > Linux::Clone

Download:
Linux-Clone-0.01.tar.gz

Dependencies

Annotate this POD

CPAN RT

Open  0
View/Report Bugs
Module Version: 0.01   Source  

NAME ^

Linux::Clone - an interface to the linux clone(2) and unshare(2) syscalls

SYNOPSIS ^

 use Linux::Clone;

DESCRIPTION ^

This module exposes the linux clone(2) and unshare(2) syscalls to Perl.

$retval = unshare $flags

The following CLONE_ flag values (without CLONE_ prefix) are supported for unshare, if found, in this release. See the documentation for unshare(2) for more info on what they do:

   Linux::Clone::FILES
   Linux::Clone::FS
   Linux::Clone::NEWNS   (in unshare, implies FS)
   Linux::Clone::VM      (in unshare, implies SIGHAND)
   Linux::Clone::THREAD  (in unshare, implies VM, SIGHAND)
   Linux::Clone::SIGHAND
   Linux::Clone::SYSVSEM
   Linux::Clone::NEWUTS
   Linux::Clone::NEWIPC
   Linux::Clone::NEWNET

Example: unshare the network namespace and prove that by calling ifconfig, showing only an unconfigured lo interface.

   Linux::Clone::unshare Linux::Clone::NEWNET
      and "unshare: $!";
   system "ifconfig -a";

Example: unshare the network namespace, initialise the loopback interface, create a veth interface pair, put one interface into the parent processes namespace (use ifconfig -a from another shell), configure the other interface with 192.168.99.2 -> 192.168.99.1 and start a shell.

   use Linux::Clone;

   # unshare our network namespace
   Linux::Clone::unshare Linux::Clone::NEWNET
     and "unshare: $!";

   my $ppid = getppid;

   system "
      # configure loopback interface
      ip link set lo up
      ip route add 127.0.0.0/8 dev lo

      # create veth pair
      ip link add name veth_master type veth peer name veth_slave

      # move veth_master to our parent process' namespace
      ip link set veth_master netns $ppid

      # configure the local interface
      ip link set veth_slave up
      ip addr add 192.168.99.2/32 dev veth_slave
      ip route add 192.168.99.1/32 dev veth_slave
   ";

   print <<EOF;
   say hi to your new network namespace, use exit to return.

   try this from another shell to get networking up:

   ip link set veth_master up
   ip addr add 192.168.99.1/32 dev veth_master
   ip route add 192.168.99.2/32 dev veth_master

   EOF
   system "bash";

Example: unshare the filesystem namespace and make a confusing bind mount only visible to the current process.

   use Linux::Clone;

   Linux::Clone::unshare Linux::Clone::NEWNS
      and die "unshare: $!";

   # now bind-mount /lib over /etc and ls -l /etc - scary
   system "mount -n --bind /lib /etc";
   system "ls -l /etc";
$retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, $tls, $ctid]

Clones a new process as specified via $flags and calls $coderef without any arguments (a closure might help you if you need to pass arguments without global variables). The return value from coderef is returned to the system.

The $stacksize specifies how large a stack to allocate for the child. If it is 0, then a default stack size (currently 4MB) will be allocated. There is currently no way to free this area again in the child.

$ptid, if specified, will receive the thread id, $tls, if specified, must contain a struct user_desc and $ctid is currently totally unsupported and must not be specified.

Since this call basically bypasses both perl and your libc (for example, $$ might reflect the parent or child pid in the child), you need to be very careful when using this call, which means you should probably have a very good understanding of perl memory management and how fork and clone work.

The following flags are supported for clone, in addition to all flags supported by unshare, above, and a signal number. When in doubt, refer to the clone(2) manual page.

   Linux::Clone::PTRACE
   Linux::Clone::VFORK
   Linux::Clone::SETTLS         (not yet implemented)
   Linux::Clone::PARENT_SETTID  (not yet implemented)
   Linux::Clone::CHILD_SETTID   (not yet implemented)
   Linux::Clone::CHILD_CLEARTID (not yet implemented)
   Linux::Clone::DETACHED
   Linux::Clone::UNTRACED
   Linux::Clone::NEWUSER
   Linux::Clone::NEWPID
   Linux::Clone::IO

Note that for practical reasons you basically must not use Linux::Clone::VM or Linux::Clone::VFORK, as perl is unlikely to cope with that.

This is the glibc clone call, it cannot be used to emulate fork.

Example: do a fork-like clone, sharing nothing, slightly confusing perl and your libc, and exit immediately.

   my $pid = Linux::Clone::clone sub { warn "in child"; 77 }, 0, POSIX::SIGCHLD;

AUTHOR ^

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/
syntax highlighting: