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NAME |
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Linux::Clone - an interface to the linux clone(2) and unshare(2) |
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syscalls |
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SYNOPSIS |
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use Linux::Clone; |
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DESCRIPTION |
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This module exposes the linux clone(2) and unshare(2) syscalls to Perl. |
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$retval = unshare $flags |
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The following CLONE_ flag values (without CLONE_ prefix) are |
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supported for unshare, if found, in this release. See the |
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documentation for unshare(2) for more info on what they do: |
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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::NEWUTS |
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Linux::Clone::NEWIPC |
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Linux::Clone::NEWNET |
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Example: unshare the network namespace and prove that by calling |
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ifconfig, showing only an unconfigured lo interface. |
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Linux::Clone::unshare Linux::Clone::NEWNET |
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and "unshare: $!"; |
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system "ifconfig -a"; |
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Example: unshare the network namespace, initialise the loopback |
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interface, create a veth interface pair, put one interface into the |
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parent processes namespace (use ifconfig -a from another shell), |
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configure the other interface with 192.168.99.2 -> 192.168.99.1 and |
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start a shell. |
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use Linux::Clone; |
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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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my $ppid = getppid; |
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system " |
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# configure loopback interface |
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ip link set lo up |
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ip route add 127.0.0.0/8 dev lo |
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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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# move veth_master to our parent process' namespace |
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ip link set veth_master netns $ppid |
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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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try this from another shell to get networking up: |
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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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EOF |
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system "bash"; |
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Example: unshare the filesystem namespace and make a confusing bind |
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mount only visible to the current process. |
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use Linux::Clone; |
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Linux::Clone::unshare Linux::Clone::NEWNS |
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and die "unshare: $!"; |
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# now bind-mount /lib over /etc and ls -l /etc - scary |
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system "mount -n --bind /lib /etc"; |
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system "ls -l /etc"; |
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$retval = Linux::Clone::clone $coderef, $stacksize, $flags[, $ptid, |
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$tls, $ctid] |
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Clones a new process as specified via $flags and calls $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 |
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is returned to the system. |
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The $stacksize specifies how large a stack to allocate for the |
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child. If it is 0, then a default stack size (currently 4MB) will be |
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allocated. There is currently no way to free this area again in the |
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child. |
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$ptid, if specified, will receive the thread id, $tls, if specified, |
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must contain a "struct user_desc" and $ctid is currently totally |
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unsupported and must not be specified. |
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Since this call basically bypasses both perl and your libc (for |
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example, $$ might reflect the parent *or* child pid in the child), |
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you need to be very careful when using this call, which means you |
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should probably have a very good understanding of perl memory |
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management and how fork and clone work. |
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The following flags are supported for clone, in addition to all |
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flags supported by "unshare", above, and a signal number. When in |
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doubt, refer to the clone(2) manual page. |
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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::DETACHED |
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Linux::Clone::UNTRACED |
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Linux::Clone::NEWUSER |
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Linux::Clone::NEWPID |
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Linux::Clone::IO |
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Note that for practical reasons you basically must not use |
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"Linux::Clone::VM" or "Linux::Clone::VFORK", as perl is unlikely to |
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cope with that. |
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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 |
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perl 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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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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