| 1 |
=head1 NAME |
| 2 |
|
| 3 |
Linux::Clone - an interface to the linux clone, unshare, setns, pivot_root and kcmp syscalls |
| 4 |
|
| 5 |
=head1 SYNOPSIS |
| 6 |
|
| 7 |
use Linux::Clone; |
| 8 |
|
| 9 |
=head1 DESCRIPTION |
| 10 |
|
| 11 |
This module exposes the linux clone(2), unshare(2) and some related |
| 12 |
syscalls to 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 |
Linux::Clone::NEWUSER (in unshare, implies CLONE_THREAD) |
| 30 |
Linux::Clone::NEWPID |
| 31 |
Linux::Clone::NEWUTS |
| 32 |
Linux::Clone::NEWIPC |
| 33 |
Linux::Clone::NEWNET |
| 34 |
Linux::Clone::NEWCGROUP |
| 35 |
|
| 36 |
Example: unshare the network namespace and prove that by calling ifconfig, |
| 37 |
showing only the unconfigured lo interface. |
| 38 |
|
| 39 |
Linux::Clone::unshare Linux::Clone::NEWNET |
| 40 |
and "unshare: $!"; |
| 41 |
Linux::Clone::configure_loopback; |
| 42 |
system "ifconfig"; |
| 43 |
|
| 44 |
Example: unshare the network namespace, initialise the loopback interface, |
| 45 |
create a veth interface pair, put one interface into the parent processes |
| 46 |
namespace (use ifconfig -a from another shell), configure the other |
| 47 |
interface with 192.168.99.2 -> 192.168.99.1 and start a shell. |
| 48 |
|
| 49 |
use Linux::Clone; |
| 50 |
|
| 51 |
# unshare our network namespace |
| 52 |
Linux::Clone::unshare Linux::Clone::NEWNET |
| 53 |
and "unshare: $!"; |
| 54 |
|
| 55 |
Linux::Clone::configure_loopback; |
| 56 |
|
| 57 |
my $ppid = getppid; |
| 58 |
|
| 59 |
system " |
| 60 |
# create veth pair |
| 61 |
ip link add name veth_master type veth peer name veth_slave |
| 62 |
|
| 63 |
# move veth_master to our parent process' namespace |
| 64 |
ip link set veth_master netns $ppid |
| 65 |
|
| 66 |
# configure the local interface |
| 67 |
ip link set veth_slave up |
| 68 |
ip addr add 192.168.99.2/32 dev veth_slave |
| 69 |
ip route add 192.168.99.1/32 dev veth_slave |
| 70 |
"; |
| 71 |
|
| 72 |
print <<EOF; |
| 73 |
say hi to your new network namespace, use exit to return. |
| 74 |
|
| 75 |
try this from another shell to get networking up: |
| 76 |
|
| 77 |
ip link set veth_master up |
| 78 |
ip addr add 192.168.99.1/32 dev veth_master |
| 79 |
ip route add 192.168.99.2/32 dev veth_master |
| 80 |
|
| 81 |
EOF |
| 82 |
system "bash"; |
| 83 |
|
| 84 |
Example: unshare the filesystem namespace and make a confusing bind mount |
| 85 |
only visible to the current process. |
| 86 |
|
| 87 |
use Linux::Clone; |
| 88 |
|
| 89 |
Linux::Clone::unshare Linux::Clone::NEWNS |
| 90 |
and die "unshare: $!"; |
| 91 |
|
| 92 |
# now bind-mount /lib over /etc and ls -l /etc - looks scary |
| 93 |
system "mount -n --bind /lib /etc"; |
| 94 |
system "ls -l /etc"; |
| 95 |
|
| 96 |
=item $retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, $tls, $ctid] |
| 97 |
|
| 98 |
Clones a new process as specified via C<$flags> and calls C<$coderef> |
| 99 |
without any arguments (a closure might help you if you need to pass |
| 100 |
arguments without global variables). The return value from coderef is |
| 101 |
returned to the system. |
| 102 |
|
| 103 |
The C<$stacksize> specifies how large a stack to allocate for the |
| 104 |
child. If it is C<0>, then a default stack size (currently 4MB) will be |
| 105 |
allocated. There is currently no way to free this area again in the child. |
| 106 |
|
| 107 |
C<$ptid>, if specified, will receive the thread id, C<$tls>, if specified, |
| 108 |
must contain a C<struct user_desc> and C<$ctid> is currently totally |
| 109 |
unsupported and must not be specified. |
| 110 |
|
| 111 |
Since this call basically bypasses both perl and your libc (for example, |
| 112 |
C<$$> might reflect the parent I<or> child pid in the child), you need to |
| 113 |
be very careful when using this call, which means you should probably have |
| 114 |
a very good understanding of perl memory management and how fork and clone |
| 115 |
work. |
| 116 |
|
| 117 |
The following flags are supported for clone, in addition to all flags |
| 118 |
supported by C<unshare>, above, and a signal number. When in doubt, refer |
| 119 |
to the clone(2) manual page. |
| 120 |
|
| 121 |
Linux::Clone::PTRACE |
| 122 |
Linux::Clone::VFORK |
| 123 |
Linux::Clone::SETTLS (not yet implemented) |
| 124 |
Linux::Clone::PARENT_SETTID (not yet implemented) |
| 125 |
Linux::Clone::CHILD_SETTID (not yet implemented) |
| 126 |
Linux::Clone::CHILD_CLEARTID (not yet implemented) |
| 127 |
Linux::Clone::PIDFD (not yet implemented) |
| 128 |
Linux::Clone::DETACHED |
| 129 |
Linux::Clone::UNTRACED |
| 130 |
Linux::Clone::IO |
| 131 |
Linux::Clone::CSIGNAL exit signal mask |
| 132 |
|
| 133 |
Note that for practical reasons you basically must not use |
| 134 |
C<Linux::Clone::VM> or C<Linux::Clone::VFORK>, as perl is unlikely to cope |
| 135 |
with that. |
| 136 |
|
| 137 |
This is the glibc clone call, it cannot be used to emulate fork. |
| 138 |
|
| 139 |
Example: do a fork-like clone, sharing nothing, slightly confusing perl |
| 140 |
and your libc, and exit immediately. |
| 141 |
|
| 142 |
my $pid = Linux::Clone::clone sub { warn "in child"; 77 }, 0, POSIX::SIGCHLD; |
| 143 |
|
| 144 |
=item Linux::Clone::setns $fh_or_fd[, $nstype] |
| 145 |
|
| 146 |
Calls setns(2) on the file descriptor (or file handle) C<$fh_or_fd>. If |
| 147 |
C<$nstype> is missing, then C<0> is used. |
| 148 |
|
| 149 |
The argument C<$nstype> can be C<0>, C<Linux::Clone::NEWIPC>, |
| 150 |
C<Linux::Clone::NEWNET>, C<Linux::Clone::NEWUTS>, C<Linux::Clone::NEWCGROUP>, |
| 151 |
C<Linux::Clone::NEWNS>, C<Linux::Clone::NEWPID> or C<Linux::Clone::NEWUSER>. |
| 152 |
|
| 153 |
=item Linux::Clone::pivot_root $new_root, $old_root |
| 154 |
|
| 155 |
Calls pivot_root(2) - refer to its manpage for details. |
| 156 |
|
| 157 |
=item Linux::Clone::kcmp $pid1, $pid2, $type[, $idx1, $idx2] |
| 158 |
|
| 159 |
Calls kcmp(2) - refer to its manpage for details on operations. |
| 160 |
|
| 161 |
The following C<$type> constants are available if the kcmp syscall number |
| 162 |
was available during compilation: |
| 163 |
|
| 164 |
C<Linux::Clone::KCMP_FILE>, C<Linux::Clone::KCMP_VM>, C<Linux::Clone::KCMP_FILES>, |
| 165 |
C<Linux::Clone::KCMP_FS>, C<Linux::Clone::KCMP_SIGHAND>, C<Linux::Clone::KCMP_IO> and |
| 166 |
C<Linux::Clone::KCMP_SYSVSEM>. |
| 167 |
|
| 168 |
=item Linux::Clone::configure_loopback |
| 169 |
|
| 170 |
Configures a working loopback interface (basically, does the equivalent of |
| 171 |
"ifconfig lo up" which automatically adds ipv4/ipv6 addresses and routes), |
| 172 |
which can be useful to get a network namespace going. |
| 173 |
|
| 174 |
Dies on error and returns nothing. |
| 175 |
|
| 176 |
=back |
| 177 |
|
| 178 |
=cut |
| 179 |
|
| 180 |
package Linux::Clone; |
| 181 |
|
| 182 |
# use common::sense; |
| 183 |
|
| 184 |
BEGIN { |
| 185 |
our $VERSION = '1.3'; |
| 186 |
|
| 187 |
require XSLoader; |
| 188 |
XSLoader::load (__PACKAGE__, $VERSION); |
| 189 |
} |
| 190 |
|
| 191 |
sub configure_loopback() { |
| 192 |
siocsifflags "lo" |
| 193 |
and die "Linux::Clone::configure_looopback: unable to bring up loopback interface: $!\n"; |
| 194 |
} |
| 195 |
|
| 196 |
1; |
| 197 |
|
| 198 |
=head1 SEE ALSO |
| 199 |
|
| 200 |
L<IO::AIO> has some related functions, such as C<pidfd_send_signal>, and |
| 201 |
some unrelated fucntions that might be useful. |
| 202 |
|
| 203 |
=head1 AUTHOR |
| 204 |
|
| 205 |
Marc Lehmann <schmorp@schmorp.de> |
| 206 |
http://home.schmorp.de/ |
| 207 |
|
| 208 |
=cut |
| 209 |
|
