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 related syscalls to |
12 |
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 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 |
=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<$nstype> is missing, then C<0> is used. |
147 |
|
148 |
The argument C<$nstype> can be C<0>, C<Linux::Clone::NEWIPC>, |
149 |
C<Linux::Clone::NEWNET>, C<Linux::Clone::NEUTS>, C<Linux::Clone::NEWCGROUP>, |
150 |
C<Linux::Clone::NEWNS>, C<Linux::Clone::NEWPID> or C<Linux::Clone::NEWUSER>. |
151 |
|
152 |
=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 |
=back |
169 |
|
170 |
=cut |
171 |
|
172 |
package Linux::Clone; |
173 |
|
174 |
# use common::sense; |
175 |
|
176 |
BEGIN { |
177 |
our $VERSION = '1.2'; |
178 |
|
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 |
|