Linux-Clone/Clone.pm

=head1 NAME

Linux::Clone - an interface to the linux clone, unshare, setns, pivot_root and kcmp syscalls

=head1 SYNOPSIS

 use Linux::Clone;

=head1 DESCRIPTION

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

=over 4

=item $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::NEWUSER (in unshare, implies CLONE_THREAD)
   Linux::Clone::NEWPID
   Linux::Clone::NEWUTS
   Linux::Clone::NEWIPC
   Linux::Clone::NEWNET
   Linux::Clone::NEWCGROUP

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";

=item $retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, $tls, $ctid]

Clones a new process as specified via C<$flags> and calls C<$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 C<$stacksize> specifies how large a stack to allocate for the
child. If it is C<0>, then a default stack size (currently 4MB) will be
allocated. There is currently no way to free this area again in the child.

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

Since this call basically bypasses both perl and your libc (for example,
C<$$> might reflect the parent I<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 C<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::IO

Note that for practical reasons you basically must not use
C<Linux::Clone::VM> or C<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;

=item Linux::Clone::setns $fh_or_fd[, $nstype]

Calls setns(2) on the file descriptor (or file handle) C<$fh_or_fd>. If
C<$nstype> is missing, then C<0> is used.

The argument C<$nstype> can be C<0>, C<Linux::Clone::NEWIPC>,
C<Linux::Clone::NEWNET>, C<Linux::Clone::NEWUTS>, C<Linux::Clone::NEWCGROUP>,
C<Linux::Clone::NEWNS>, C<Linux::Clone::NEWPID> or C<Linux::Clone::NEWUSER>.

=item Linux::Clone::pivot_root $new_root, $old_root

Calls pivot_root(2) - refer to its manpage for details.

=item Linux::Clone::kcmp $pid1, $pid2, $type[, $idx1, $idx2]

Calls kcmp(2) - refer to its manpage for details on operations.

The following C<$type> constants are available if the kcmp syscall number
was available during compilation:

C<Linux::Clone::KCMP_FILE>, C<Linux::Clone::KCMP_VM>, C<Linux::Clone::KCMP_FILES>,
C<Linux::Clone::KCMP_FS>, C<Linux::Clone::KCMP_SIGHAND>, C<Linux::Clone::KCMP_IO> and
C<Linux::Clone::KCMP_SYSVSEM>.


=back

=cut

package Linux::Clone;

# use common::sense;

BEGIN {
   our $VERSION = '1.2';

   require XSLoader;
   XSLoader::load (__PACKAGE__, $VERSION);
}

1;

=head1 AUTHOR

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

=cut

Revision:	1.5
Committed:	Mon Jul 25 10:59:29 2022 UTC (2 years, 4 months ago) by root
Branch:	MAIN
Changes since 1.4:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.3	Linux::Clone - an interface to the linux clone, unshare, setns, pivot_root and kcmp syscalls
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Linux::Clone;
8
9			=head1 DESCRIPTION
10
11	root	1.2	This module exposes the linux clone(2), unshare(2) and related syscalls to
12	root	1.1	Perl.
13
14			=over 4
15
16			=item $retval = unshare $flags
17
18			The following CLONE_ flag values (without CLONE_ prefix) are supported for
19			unshare, if found, in this release. See the documentation for unshare(2)
20			for more info on what they do:
21
22			Linux::Clone::FILES
23			Linux::Clone::FS
24			Linux::Clone::NEWNS (in unshare, implies FS)
25			Linux::Clone::VM (in unshare, implies SIGHAND)
26			Linux::Clone::THREAD (in unshare, implies VM, SIGHAND)
27			Linux::Clone::SIGHAND
28			Linux::Clone::SYSVSEM
29	root	1.2	Linux::Clone::NEWUSER (in unshare, implies CLONE_THREAD)
30			Linux::Clone::NEWPID
31	root	1.1	Linux::Clone::NEWUTS
32			Linux::Clone::NEWIPC
33			Linux::Clone::NEWNET
34	root	1.2	Linux::Clone::NEWCGROUP
35	root	1.1
36			Example: unshare the network namespace and prove that by calling ifconfig,
37			showing only an unconfigured lo interface.
38
39			Linux::Clone::unshare Linux::Clone::NEWNET
40			and "unshare: $!";
41			system "ifconfig -a";
42
43			Example: unshare the network namespace, initialise the loopback interface,
44			create a veth interface pair, put one interface into the parent processes
45			namespace (use ifconfig -a from another shell), configure the other
46			interface with 192.168.99.2 -> 192.168.99.1 and start a shell.
47
48			use Linux::Clone;
49
50			# unshare our network namespace
51			Linux::Clone::unshare Linux::Clone::NEWNET
52			and "unshare: $!";
53
54			my $ppid = getppid;
55
56			system "
57			# configure loopback interface
58			ip link set lo up
59			ip route add 127.0.0.0/8 dev lo
60
61			# create veth pair
62			ip link add name veth_master type veth peer name veth_slave
63
64			# move veth_master to our parent process' namespace
65			ip link set veth_master netns $ppid
66
67			# configure the local interface
68			ip link set veth_slave up
69			ip addr add 192.168.99.2/32 dev veth_slave
70			ip route add 192.168.99.1/32 dev veth_slave
71			";
72
73			print <<EOF;
74			say hi to your new network namespace, use exit to return.
75
76			try this from another shell to get networking up:
77
78			ip link set veth_master up
79			ip addr add 192.168.99.1/32 dev veth_master
80			ip route add 192.168.99.2/32 dev veth_master
81
82			EOF
83			system "bash";
84
85			Example: unshare the filesystem namespace and make a confusing bind mount
86			only visible to the current process.
87
88			use Linux::Clone;
89
90			Linux::Clone::unshare Linux::Clone::NEWNS
91			and die "unshare: $!";
92
93			# now bind-mount /lib over /etc and ls -l /etc - scary
94			system "mount -n --bind /lib /etc";
95			system "ls -l /etc";
96
97			=item $retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, $tls, $ctid]
98
99			Clones a new process as specified via C<$flags> and calls C<$coderef>
100			without any arguments (a closure might help you if you need to pass
101			arguments without global variables). The return value from coderef is
102			returned to the system.
103
104			The C<$stacksize> specifies how large a stack to allocate for the
105			child. If it is C<0>, then a default stack size (currently 4MB) will be
106			allocated. There is currently no way to free this area again in the child.
107
108			C<$ptid>, if specified, will receive the thread id, C<$tls>, if specified,
109			must contain a C<struct user_desc> and C<$ctid> is currently totally
110			unsupported and must not be specified.
111
112			Since this call basically bypasses both perl and your libc (for example,
113			C<$$> might reflect the parent I<or> child pid in the child), you need to
114			be very careful when using this call, which means you should probably have
115			a very good understanding of perl memory management and how fork and clone
116			work.
117
118			The following flags are supported for clone, in addition to all flags
119			supported by C<unshare>, above, and a signal number. When in doubt, refer
120			to the clone(2) manual page.
121
122			Linux::Clone::PTRACE
123			Linux::Clone::VFORK
124			Linux::Clone::SETTLS (not yet implemented)
125			Linux::Clone::PARENT_SETTID (not yet implemented)
126			Linux::Clone::CHILD_SETTID (not yet implemented)
127			Linux::Clone::CHILD_CLEARTID (not yet implemented)
128			Linux::Clone::DETACHED
129			Linux::Clone::UNTRACED
130			Linux::Clone::IO
131
132			Note that for practical reasons you basically must not use
133			C<Linux::Clone::VM> or C<Linux::Clone::VFORK>, as perl is unlikely to cope
134			with that.
135
136			This is the glibc clone call, it cannot be used to emulate fork.
137
138			Example: do a fork-like clone, sharing nothing, slightly confusing perl
139			and your libc, and exit immediately.
140
141			my $pid = Linux::Clone::clone sub { warn "in child"; 77 }, 0, POSIX::SIGCHLD;
142
143	root	1.2	=item Linux::Clone::setns $fh_or_fd[, $nstype]
144
145			Calls setns(2) on the file descriptor (or file handle) C<$fh_or_fd>. If
146			C<$nstype> is missing, then C<0> is used.
147
148	root	1.3	The argument C<$nstype> can be C<0>, C<Linux::Clone::NEWIPC>,
149	root	1.5	C<Linux::Clone::NEWNET>, C<Linux::Clone::NEWUTS>, C<Linux::Clone::NEWCGROUP>,
150	root	1.2	C<Linux::Clone::NEWNS>, C<Linux::Clone::NEWPID> or C<Linux::Clone::NEWUSER>.
151
152	root	1.3	=item Linux::Clone::pivot_root $new_root, $old_root
153
154			Calls pivot_root(2) - refer to its manpage for details.
155
156			=item Linux::Clone::kcmp $pid1, $pid2, $type[, $idx1, $idx2]
157
158			Calls kcmp(2) - refer to its manpage for details on operations.
159
160			The following C<$type> constants are available if the kcmp syscall number
161			was available during compilation:
162
163			C<Linux::Clone::KCMP_FILE>, C<Linux::Clone::KCMP_VM>, C<Linux::Clone::KCMP_FILES>,
164			C<Linux::Clone::KCMP_FS>, C<Linux::Clone::KCMP_SIGHAND>, C<Linux::Clone::KCMP_IO> and
165			C<Linux::Clone::KCMP_SYSVSEM>.
166
167
168	root	1.1	=back
169
170			=cut
171
172			package Linux::Clone;
173
174			# use common::sense;
175
176			BEGIN {
177	root	1.4	our $VERSION = '1.2';
178	root	1.1
179			require XSLoader;
180			XSLoader::load (__PACKAGE__, $VERSION);
181			}
182
183			1;
184
185			=head1 AUTHOR
186
187			Marc Lehmann <schmorp@schmorp.de>
188			http://home.schmorp.de/
189
190			=cut
191