| 1 |
NAME |
| 2 |
Linux::Clone - an interface to the linux clone(2) and unshare(2) |
| 3 |
syscalls |
| 4 |
|
| 5 |
SYNOPSIS |
| 6 |
use Linux::Clone; |
| 7 |
|
| 8 |
DESCRIPTION |
| 9 |
This module exposes the linux clone(2) and unshare(2) syscalls to Perl. |
| 10 |
|
| 11 |
$retval = unshare $flags |
| 12 |
The following CLONE_ flag values (without CLONE_ prefix) are |
| 13 |
supported for unshare, if found, in this release. See the |
| 14 |
documentation for unshare(2) for more info on what they do: |
| 15 |
|
| 16 |
Linux::Clone::FILES |
| 17 |
Linux::Clone::FS |
| 18 |
Linux::Clone::NEWNS (in unshare, implies FS) |
| 19 |
Linux::Clone::VM (in unshare, implies SIGHAND) |
| 20 |
Linux::Clone::THREAD (in unshare, implies VM, SIGHAND) |
| 21 |
Linux::Clone::SIGHAND |
| 22 |
Linux::Clone::SYSVSEM |
| 23 |
Linux::Clone::NEWUTS |
| 24 |
Linux::Clone::NEWIPC |
| 25 |
Linux::Clone::NEWNET |
| 26 |
|
| 27 |
Example: unshare the network namespace and prove that by calling |
| 28 |
ifconfig, showing only an unconfigured lo interface. |
| 29 |
|
| 30 |
Linux::Clone::unshare Linux::Clone::NEWNET |
| 31 |
and "unshare: $!"; |
| 32 |
system "ifconfig -a"; |
| 33 |
|
| 34 |
Example: unshare the network namespace, initialise the loopback |
| 35 |
interface, create a veth interface pair, put one interface into the |
| 36 |
parent processes namespace (use ifconfig -a from another shell), |
| 37 |
configure the other interface with 192.168.99.2 -> 192.168.99.1 and |
| 38 |
start a shell. |
| 39 |
|
| 40 |
use Linux::Clone; |
| 41 |
|
| 42 |
# unshare our network namespace |
| 43 |
Linux::Clone::unshare Linux::Clone::NEWNET |
| 44 |
and "unshare: $!"; |
| 45 |
|
| 46 |
my $ppid = getppid; |
| 47 |
|
| 48 |
system " |
| 49 |
# configure loopback interface |
| 50 |
ip link set lo up |
| 51 |
ip route add 127.0.0.0/8 dev lo |
| 52 |
|
| 53 |
# create veth pair |
| 54 |
ip link add name veth_master type veth peer name veth_slave |
| 55 |
|
| 56 |
# move veth_master to our parent process' namespace |
| 57 |
ip link set veth_master netns $ppid |
| 58 |
|
| 59 |
# configure the local interface |
| 60 |
ip link set veth_slave up |
| 61 |
ip addr add 192.168.99.2/32 dev veth_slave |
| 62 |
ip route add 192.168.99.1/32 dev veth_slave |
| 63 |
"; |
| 64 |
|
| 65 |
print <<EOF; |
| 66 |
say hi to your new network namespace, use exit to return. |
| 67 |
|
| 68 |
try this from another shell to get networking up: |
| 69 |
|
| 70 |
ip link set veth_master up |
| 71 |
ip addr add 192.168.99.1/32 dev veth_master |
| 72 |
ip route add 192.168.99.2/32 dev veth_master |
| 73 |
|
| 74 |
EOF |
| 75 |
system "bash"; |
| 76 |
|
| 77 |
Example: unshare the filesystem namespace and make a confusing bind |
| 78 |
mount only visible to the current process. |
| 79 |
|
| 80 |
use Linux::Clone; |
| 81 |
|
| 82 |
Linux::Clone::unshare Linux::Clone::NEWNS |
| 83 |
and die "unshare: $!"; |
| 84 |
|
| 85 |
# now bind-mount /lib over /etc and ls -l /etc - scary |
| 86 |
system "mount -n --bind /lib /etc"; |
| 87 |
system "ls -l /etc"; |
| 88 |
|
| 89 |
$retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, |
| 90 |
$tls, $ctid] |
| 91 |
Clones a new process as specified via $flags and calls $coderef |
| 92 |
without any arguments (a closure might help you if you need to pass |
| 93 |
arguments without global variables). The return value from coderef |
| 94 |
is returned to the system. |
| 95 |
|
| 96 |
The $stacksize specifies how large a stack to allocate for the |
| 97 |
child. If it is 0, then a default stack size (currently 4MB) will be |
| 98 |
allocated. There is currently no way to free this area again in the |
| 99 |
child. |
| 100 |
|
| 101 |
$ptid, if specified, will receive the thread id, $tls, if specified, |
| 102 |
must contain a "struct user_desc" and $ctid is currently totally |
| 103 |
unsupported and must not be specified. |
| 104 |
|
| 105 |
Since this call basically bypasses both perl and your libc (for |
| 106 |
example, $$ might reflect the parent *or* child pid in the child), |
| 107 |
you need to be very careful when using this call, which means you |
| 108 |
should probably have a very good understanding of perl memory |
| 109 |
management and how fork and clone work. |
| 110 |
|
| 111 |
The following flags are supported for clone, in addition to all |
| 112 |
flags supported by "unshare", above, and a signal number. When in |
| 113 |
doubt, refer to the clone(2) manual page. |
| 114 |
|
| 115 |
Linux::Clone::PTRACE |
| 116 |
Linux::Clone::VFORK |
| 117 |
Linux::Clone::SETTLS (not yet implemented) |
| 118 |
Linux::Clone::PARENT_SETTID (not yet implemented) |
| 119 |
Linux::Clone::CHILD_SETTID (not yet implemented) |
| 120 |
Linux::Clone::CHILD_CLEARTID (not yet implemented) |
| 121 |
Linux::Clone::DETACHED |
| 122 |
Linux::Clone::UNTRACED |
| 123 |
Linux::Clone::NEWUSER |
| 124 |
Linux::Clone::NEWPID |
| 125 |
Linux::Clone::IO |
| 126 |
|
| 127 |
Note that for practical reasons you basically must not use |
| 128 |
"Linux::Clone::VM" or "Linux::Clone::VFORK", as perl is unlikely to |
| 129 |
cope with that. |
| 130 |
|
| 131 |
This is the glibc clone call, it cannot be used to emulate fork. |
| 132 |
|
| 133 |
Example: do a fork-like clone, sharing nothing, slightly confusing |
| 134 |
perl and your libc, and exit immediately. |
| 135 |
|
| 136 |
my $pid = Linux::Clone::clone sub { warn "in child"; 77 }, 0, POSIX::SIGCHLD; |
| 137 |
|
| 138 |
AUTHOR |
| 139 |
Marc Lehmann <schmorp@schmorp.de> |
| 140 |
http://home.schmorp.de/ |
| 141 |
|
