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/