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=head1 NAME |
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|
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Linux::Clone - an interface to the linux clone, unshare, setns, pivot_root and kcmp syscalls |
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|
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=head1 SYNOPSIS |
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|
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use Linux::Clone; |
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|
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=head1 DESCRIPTION |
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|
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This module exposes the linux clone(2), unshare(2) and some related |
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syscalls to Perl. |
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|
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=over 4 |
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|
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=item $retval = unshare $flags |
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|
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The following CLONE_ flag values (without CLONE_ prefix) are supported for |
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unshare, if found, in this release. See the documentation for unshare(2) |
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for more info on what they do: |
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|
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Linux::Clone::FILES |
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Linux::Clone::FS |
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Linux::Clone::NEWNS (in unshare, implies FS) |
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Linux::Clone::VM (in unshare, implies SIGHAND) |
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Linux::Clone::THREAD (in unshare, implies VM, SIGHAND) |
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Linux::Clone::SIGHAND |
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Linux::Clone::SYSVSEM |
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Linux::Clone::NEWUSER (in unshare, implies CLONE_THREAD) |
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Linux::Clone::NEWPID |
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Linux::Clone::NEWUTS |
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Linux::Clone::NEWIPC |
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Linux::Clone::NEWNET |
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Linux::Clone::NEWCGROUP |
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|
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Example: unshare the network namespace and prove that by calling ifconfig, |
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showing only the unconfigured lo interface. |
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|
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Linux::Clone::unshare Linux::Clone::NEWNET |
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and "unshare: $!"; |
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Linux::Clone::configure_loopback; |
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system "ifconfig"; |
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|
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Example: unshare the network namespace, initialise the loopback interface, |
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create a veth interface pair, put one interface into the parent processes |
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namespace (use ifconfig -a from another shell), configure the other |
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interface with 192.168.99.2 -> 192.168.99.1 and start a shell. |
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|
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use Linux::Clone; |
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|
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# unshare our network namespace |
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Linux::Clone::unshare Linux::Clone::NEWNET |
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and "unshare: $!"; |
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|
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Linux::Clone::configure_loopback; |
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|
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my $ppid = getppid; |
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|
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system " |
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# create veth pair |
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ip link add name veth_master type veth peer name veth_slave |
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|
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# move veth_master to our parent process' namespace |
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ip link set veth_master netns $ppid |
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|
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# configure the local interface |
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ip link set veth_slave up |
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ip addr add 192.168.99.2/32 dev veth_slave |
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ip route add 192.168.99.1/32 dev veth_slave |
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"; |
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print <<EOF; |
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say hi to your new network namespace, use exit to return. |
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|
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try this from another shell to get networking up: |
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|
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ip link set veth_master up |
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ip addr add 192.168.99.1/32 dev veth_master |
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ip route add 192.168.99.2/32 dev veth_master |
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|
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EOF |
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system "bash"; |
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|
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Example: unshare the filesystem namespace and make a confusing bind mount |
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only visible to the current process. |
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|
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use Linux::Clone; |
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|
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Linux::Clone::unshare Linux::Clone::NEWNS |
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and die "unshare: $!"; |
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|
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# now bind-mount /lib over /etc and ls -l /etc - looks scary |
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system "mount -n --bind /lib /etc"; |
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system "ls -l /etc"; |
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=item $retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, $tls, $ctid] |
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Clones a new process as specified via C<$flags> and calls C<$coderef> |
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without any arguments (a closure might help you if you need to pass |
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arguments without global variables). The return value from coderef is |
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returned to the system. |
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|
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The C<$stacksize> specifies how large a stack to allocate for the |
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child. If it is C<0>, then a default stack size (currently 4MB) will be |
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allocated. There is currently no way to free this area again in the child. |
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|
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C<$ptid>, if specified, will receive the thread id, C<$tls>, if specified, |
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must contain a C<struct user_desc> and C<$ctid> is currently totally |
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unsupported and must not be specified. |
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|
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Since this call basically bypasses both perl and your libc (for example, |
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C<$$> might reflect the parent I<or> child pid in the child), you need to |
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be very careful when using this call, which means you should probably have |
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a very good understanding of perl memory management and how fork and clone |
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work. |
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|
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The following flags are supported for clone, in addition to all flags |
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supported by C<unshare>, above, and a signal number. When in doubt, refer |
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to the clone(2) manual page. |
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|
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Linux::Clone::PTRACE |
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Linux::Clone::VFORK |
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Linux::Clone::SETTLS (not yet implemented) |
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Linux::Clone::PARENT_SETTID (not yet implemented) |
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Linux::Clone::CHILD_SETTID (not yet implemented) |
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Linux::Clone::CHILD_CLEARTID (not yet implemented) |
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Linux::Clone::PIDFD (not yet implemented) |
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Linux::Clone::DETACHED |
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Linux::Clone::UNTRACED |
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Linux::Clone::IO |
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Linux::Clone::CSIGNAL exit signal mask |
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|
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Note that for practical reasons you basically must not use |
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C<Linux::Clone::VM> or C<Linux::Clone::VFORK>, as perl is unlikely to cope |
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with that. |
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|
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This is the glibc clone call, it cannot be used to emulate fork. |
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Example: do a fork-like clone, sharing nothing, slightly confusing perl |
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and your libc, and exit immediately. |
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my $pid = Linux::Clone::clone sub { warn "in child"; 77 }, 0, POSIX::SIGCHLD; |
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|
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=item Linux::Clone::setns $fh_or_fd[, $nstype] |
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|
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Calls setns(2) on the file descriptor (or file handle) C<$fh_or_fd>. If |
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C<$nstype> is missing, then C<0> is used. |
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|
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The argument C<$nstype> can be C<0>, C<Linux::Clone::NEWIPC>, |
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C<Linux::Clone::NEWNET>, C<Linux::Clone::NEWUTS>, C<Linux::Clone::NEWCGROUP>, |
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C<Linux::Clone::NEWNS>, C<Linux::Clone::NEWPID> or C<Linux::Clone::NEWUSER>. |
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|
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=item Linux::Clone::pivot_root $new_root, $old_root |
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Calls pivot_root(2) - refer to its manpage for details. |
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|
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=item Linux::Clone::kcmp $pid1, $pid2, $type[, $idx1, $idx2] |
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Calls kcmp(2) - refer to its manpage for details on operations. |
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|
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The following C<$type> constants are available if the kcmp syscall number |
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was available during compilation: |
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|
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C<Linux::Clone::KCMP_FILE>, C<Linux::Clone::KCMP_VM>, C<Linux::Clone::KCMP_FILES>, |
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C<Linux::Clone::KCMP_FS>, C<Linux::Clone::KCMP_SIGHAND>, C<Linux::Clone::KCMP_IO> and |
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C<Linux::Clone::KCMP_SYSVSEM>. |
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|
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=item Linux::Clone::configure_loopback |
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Configures a working loopback interface (basically, does the equivalent of |
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"ifconfig lo up" which automatically adds ipv4/ipv6 addresses and routes), |
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which can be useful to get a network namespace going. |
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Dies on error and returns nothing. |
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=back |
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=cut |
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|
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package Linux::Clone; |
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|
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# use common::sense; |
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|
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BEGIN { |
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our $VERSION = '1.3'; |
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|
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require XSLoader; |
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XSLoader::load (__PACKAGE__, $VERSION); |
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} |
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sub configure_loopback() { |
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siocsifflags "lo" |
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and die "Linux::Clone::configure_looopback: unable to bring up loopback interface: $!\n"; |
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} |
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|
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1; |
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=head1 AUTHOR |
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|
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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|
