--- /dev/null
+# LXC monitor socket
+
+package PVE::LXC::Monitor;
+
+use strict;
+use warnings;
+
+use IO::Socket::UNIX;
+use Socket qw(SOCK_STREAM);
+use POSIX qw(NAME_MAX);
+
+use constant {
+ STATE_STOPPED => 0,
+ STATE_STARTING => 1,
+ STATE_RUNNING => 2,
+ STATE_STOPPING => 3,
+ STATE_ABORTING => 4,
+ STATE_FREEZING => 5,
+ STATE_FROZEN => 6,
+ STATE_THAWED => 7,
+ MAX_STATE => 8,
+};
+
+my $LXC_MSG_SIZE = length(pack('I! Z'.(NAME_MAX+1).' x![I] I', 0, "", 0));
+# Unpack an lxc_msg struct.
+my sub _unpack_lxc_msg($) {
+ my ($packet) = @_;
+
+ # struct lxc_msg {
+ # lxc_msg_type_t type;
+ # char name[NAME_MAX+1];
+ # int value;
+ # };
+
+ my ($type, $name, $value) = unpack('I!Z'.(NAME_MAX+1).'I!', $packet);
+
+ if ($type == 0) {
+ $type = 'STATE';
+ } elsif ($type == 1) {
+ $type = 'PRIORITY';
+ } elsif ($type == 2) {
+ $type = 'EXITCODE';
+ } else {
+ warn "unsupported lxc message type $type received\n";
+ $type = undef;
+ }
+
+ return ($type, $name, $value);
+}
+
+# Opens the monitor socket
+#
+# Dies on errors
+sub get_monitor_socket {
+ my $socket = IO::Socket::UNIX->new(
+ Type => SOCK_STREAM(),
+ # assumes that lxcpath is '/var/lib/lxc', the hex part is a hash of the lxcpath
+ Peer => "\0lxc/ad055575fe28ddd5//var/lib/lxc",
+ );
+ if (!defined($socket)) {
+ die "failed to connect to monitor socket: $!\n";
+ }
+
+ return $socket;
+}
+
+# Read an lxc message from a socket.
+#
+# Returns undef on EOF
+# Otherwise returns a (type, vmid, value) tuple.
+#
+# The returned 'type' currently can be 'STATE', 'PRIORITY' or 'EXITSTATUS'.
+sub read_lxc_message($) {
+ my ($socket) = @_;
+
+ my $msg;
+ my $got = recv($socket, $msg, $LXC_MSG_SIZE, 0)
+ // die "failed to read from state socket: $!\n";
+
+ if (length($msg) == 0) {
+ return undef;
+ }
+
+ die "short read on state socket ($LXC_MSG_SIZE != ".length($msg).")\n"
+ if length($msg) != $LXC_MSG_SIZE;
+
+ my ($type, $name, $value) = _unpack_lxc_msg($msg);
+
+ return ($type, $name, $value);
+}
+
+1;