detection of multiple instances using flock.

sending RAISE_WINDOW leap event if we are not
the main instance.

4 files changed, 413 insertions, 16 deletions

diff --git a/src/leap/app.py b/src/leap/app.py
index 4112b404..c9f39e98 100644
--- a/src/leap/app.py
+++ b/src/leap/app.py
@@ -17,16 +17,20 @@
 
 import logging
 import signal
+import socket
 import sys
 
 from functools import partial
+
 from PySide import QtCore, QtGui
 
-from leap.common.events import server
+from leap.common.events import server as event_server
 from leap.util import __version__ as VERSION
 from leap.util import leap_argparse
 from leap.gui import locale_rc
 from leap.gui.mainwindow import MainWindow
+from leap.platform_init import IS_MAC
+from leap.platform_init.locks import we_are_the_one_and_only
 
 import codecs
 codecs.register(lambda name: codecs.lookup('utf-8')
@@ -34,8 +38,12 @@ codecs.register(lambda name: codecs.lookup('utf-8')
 
 
 def sigint_handler(*args, **kwargs):
+    """
+    Signal handler for SIGINT
+    """
     logger = kwargs.get('logger', None)
-    logger.debug('SIGINT catched. shutting down...')
+    if logger:
+        logger.debug("SIGINT catched. shutting down...")
     mainwindow = args[0]
     mainwindow.quit()
 
@@ -44,8 +52,7 @@ def main():
     """
     Launches the main event loop
     """
-
-    server.ensure_server(port=8090)
+    event_server.ensure_server(event_server.SERVER_PORT)
 
     _, opts = leap_argparse.init_leapc_args()
     debug = opts.debug
@@ -67,6 +74,15 @@ def main():
     console.setFormatter(formatter)
     logger.addHandler(console)
 
+    if we_are_the_one_and_only():
+        event_server.ensure_server(event_server.SERVER_PORT)
+    else:
+        # leap-client is already running
+        logger.warning("Tried to launch more than one instance "
+                       "of leap-client. Raising the existing "
+                       "one instead.")
+        sys.exit(1)
+
     logger.info('~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~')
     logger.info('LEAP client version %s', VERSION)
     logger.info('~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~')
@@ -98,22 +114,19 @@ def main():
     app.setApplicationName("leap")
     app.setOrganizationDomain("leap.se")
 
-    # TODO: check if the leap-client is already running and quit
-    # gracefully in that case.
-
-    window = MainWindow(standalone)
-    window.show()
-
     # This dummy timer ensures that control is given to the outside
     # loop, so we can hook our sigint handler.
     timer = QtCore.QTimer()
     timer.start(500)
     timer.timeout.connect(lambda: None)
 
+    window = MainWindow(standalone)
+    window.show()
+
     sigint_window = partial(sigint_handler, window, logger=logger)
     signal.signal(signal.SIGINT, sigint_window)
 
-    if sys.platform == "darwin":
+    if IS_MAC:
         window.raise_()
 
     # Run main loop
diff --git a/src/leap/gui/mainwindow.py b/src/leap/gui/mainwindow.py
index 0d59e24b..e362663a 100644
--- a/src/leap/gui/mainwindow.py
+++ b/src/leap/gui/mainwindow.py
@@ -26,7 +26,10 @@ from functools import partial
 
 import keyring
 from PySide import QtCore, QtGui
+
 from leap.common.check import leap_assert
+from leap.common.events import register
+from leap.common.events import events_pb2 as proto
 from leap.config.leapsettings import LeapSettings
 from leap.config.providerconfig import ProviderConfig
 from leap.crypto.srpauth import SRPAuth
@@ -34,6 +37,7 @@ from leap.gui.wizard import Wizard
 from leap.services.eip.eipbootstrapper import EIPBootstrapper
 from leap.services.eip.eipconfig import EIPConfig
 from leap.services.eip.providerbootstrapper import ProviderBootstrapper
+from leap.platform_init import IS_WIN
 from leap.platform_init.initializers import init_platform
 from leap.services.eip.vpn import VPN
 from leap.services.eip.vpnlaunchers import (VPNLauncherException,
@@ -42,14 +46,9 @@ from leap.services.eip.vpnlaunchers import (VPNLauncherException,
                                             EIPNoPolkitAuthAgentAvailable)
 from leap.util import __version__ as VERSION
 from leap.util.checkerthread import CheckerThread
-from leap.common.events import (
-    register,
-    events_pb2 as proto,
-)
 
 from ui_mainwindow import Ui_MainWindow
 
-
 logger = logging.getLogger(__name__)
 
 
@@ -65,7 +64,9 @@ class MainWindow(QtGui.QMainWindow):
     # Keyring
     KEYRING_KEY = "leap_client"
 
+    # Signals
     new_updates = QtCore.Signal(object)
+    raise_window = QtCore.Signal([])
 
     def __init__(self, standalone=False):
         """
@@ -77,8 +78,12 @@ class MainWindow(QtGui.QMainWindow):
         """
         QtGui.QMainWindow.__init__(self)
 
+        # register leap events
         register(signal=proto.UPDATER_NEW_UPDATES,
                  callback=self._new_updates_available)
+        register(signal=proto.RAISE_WINDOW,
+                 callback=self._on_raise_window_event)
+
         self._updates_content = ""
 
         self.CONNECTING_ICON = QtGui.QPixmap(":/images/conn_connecting.png")
@@ -110,6 +115,7 @@ class MainWindow(QtGui.QMainWindow):
         self._standalone = standalone
         self._provider_config = ProviderConfig()
         self._eip_config = EIPConfig()
+
         # This is created once we have a valid provider config
         self._srp_auth = None
 
@@ -166,6 +172,10 @@ class MainWindow(QtGui.QMainWindow):
             QtCore.QCoreApplication.instance(),
             QtCore.SIGNAL("aboutToQuit()"),
             self._checker_thread.wait)
+        QtCore.QCoreApplication.instance().connect(
+            QtCore.QCoreApplication.instance(),
+            QtCore.SIGNAL("aboutToQuit()"),
+            self._cleanup_pidfiles)
 
         self.ui.chkRemember.stateChanged.connect(
             self._remember_state_changed)
@@ -176,6 +186,7 @@ class MainWindow(QtGui.QMainWindow):
         self.ui.action_about_leap.triggered.connect(self._about)
         self.ui.action_quit.triggered.connect(self.quit)
         self.ui.action_wizard.triggered.connect(self._launch_wizard)
+        self.raise_window.connect(self._do_raise_mainwindow)
 
         # Used to differentiate between real quits and close to tray
         self._really_quit = False
@@ -920,6 +931,39 @@ class MainWindow(QtGui.QMainWindow):
         logger.debug("Finished VPN with exitCode %s" % (exitCode,))
         self._stop_eip()
 
+    def _on_raise_window_event(self, req):
+        """
+        Callback for the raise window event
+        """
+        self.raise_window.emit()
+
+    def _do_raise_mainwindow(self):
+        """
+        SLOT
+        TRIGGERS:
+            self._on_raise_window_event
+
+        Triggered when we receive a RAISE_WINDOW event.
+        """
+        TOPFLAG = QtCore.Qt.WindowStaysOnTopHint
+        self.setWindowFlags(self.windowFlags() | TOPFLAG)
+        self.show()
+        self.setWindowFlags(self.windowFlags() & ~TOPFLAG)
+        self.show()
+
+    def _cleanup_pidfiles(self):
+        """
+        SLOT
+        TRIGGERS:
+            self.aboutToQuit
+
+        Triggered on about to quit signal, removes lockfiles on a clean
+        shutdown
+        """
+        if IS_WIN:
+            lockfile = WindowsLock()
+            lockfile.release_lock()
+
 if __name__ == "__main__":
     import signal
 
diff --git a/src/leap/platform_init/__init__.py b/src/leap/platform_init/__init__.py
index e69de29b..2a262a30 100644
--- a/src/leap/platform_init/__init__.py
+++ b/src/leap/platform_init/__init__.py
@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+# __init__.py
+# Copyright (C) 2013 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+System constants
+"""
+import platform
+
+_system = platform.system()
+
+IS_WIN = True if _system == "Windows" else False
+IS_MAC = True if _system == "Darwin" else False
+IS_LINUX = True if _system == "Linux" else False
+IS_UNIX = IS_MAC or IS_LINUX
diff --git a/src/leap/platform_init/locks.py b/src/leap/platform_init/locks.py
new file mode 100644
index 00000000..2cdee3d9
--- /dev/null
+++ b/src/leap/platform_init/locks.py
@@ -0,0 +1,312 @@
+# -*- coding: utf-8 -*-
+# locks.py
+# Copyright (C) 2013 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+Utilities for handling multi-platform file locking mechanisms
+"""
+import commands
+import logging
+import os
+import platform
+
+from leap.common.events import signal as signal_event
+from leap.common.events import events_pb2 as proto
+from leap import platform_init
+
+if platform_init.IS_UNIX:
+    from fcntl import flock, LOCK_EX, LOCK_NB
+else:
+    import errno
+    import glob
+    import shutil
+    import socket
+
+    from tempfile import gettempdir
+
+logger = logging.getLogger(__name__)
+
+if platform_init.IS_UNIX:
+
+    class UnixLock(object):
+        """
+        Uses flock to get an exclusive lock over a file.
+        See man 2 flock
+        """
+
+        def __init__(self, path):
+            """
+            iniializes t he UnixLock with the path of the
+            desired lockfile
+            """
+
+            self._fd = None
+            self.path = path
+
+        def get_lock(self):
+            """
+            Tries to get a lock, and writes the running pid there if successful
+            """
+            gotit, pid = self._get_lock_and_pid()
+            return gotit
+
+        def get_pid(self):
+            """
+            Returns the pid of the locking process
+            """
+            gotit, pid = self._get_lock_and_pid()
+            return pid
+
+        def _get_lock(self):
+            """
+            Tries to get a lock, returning True if successful
+
+            @rtype: bool
+            """
+            self._fd = os.open(self.path, os.O_CREAT | os.O_RDWR)
+
+            try:
+                flock(self._fd, LOCK_EX | LOCK_NB)
+            except IOError as exc:
+                # could not get the lock
+                if exc.args[0] == 11:
+                    # Resource temporarily unavailable
+                    return False
+                else:
+                    raise
+            return True
+
+        @property
+        def locked_by_us(self):
+            """
+            Returns True if the pid in the pidfile
+            is ours.
+
+            @rtype: bool
+            """
+            gotit, pid = self._get_lock_and_pid()
+            return pid == os.getpid()
+
+        def _get_lock_and_pid(self):
+            """
+            Tries to get a lock over the file.
+            Returns (locked, pid) tuple.
+
+            @rtype: tuple
+            """
+
+            if self._get_lock():
+                self._write_to_pidfile()
+                return True, None
+
+            return False, self._read_from_pidfile()
+
+        def _read_from_pidfile(self):
+            """
+            Tries to read pid from the pidfile,
+            returns False if no content found.
+            """
+
+            pidfile = os.read(
+                self._fd, 16)
+            if not pidfile:
+                return False
+
+            try:
+                return int(pidfile.strip())
+            except Exception as exc:
+                exc.args += (pidfile, self.lock_file)
+                raise
+
+        def _write_to_pidfile(self):
+            """
+            Writes the pid of the running process
+            to the pidfile
+            """
+            fd = self._fd
+            os.ftruncate(fd, 0)
+            os.write(fd, '%d\n' % os.getpid())
+            os.fsync(fd)
+
+
+if platform_init.IS_WIN:
+
+    class WindowsLock(object):
+        """
+        Creates a lock based on the atomic nature of mkdir on Windows
+        system calls.
+        """
+        LOCKBASE = os.path.join(gettempdir(), "leap-client-lock")
+
+        def __init__(self):
+            """
+            Initializes the lock.
+            Sets the lock name to basename plus the process pid.
+            """
+            self._fd = None
+            pid = os.getpid()
+            self.name = "%s-%s" % (self.LOCKBASE, pid)
+            self.pid = pid
+
+        def get_lock(self):
+            """
+            Tries to get a lock, and writes the running pid there if successful
+            """
+            gotit = self._get_lock()
+            return gotit
+
+        def _get_lock(self):
+            """
+            Tries to write to a file with the current pid as part of the name
+            """
+            try:
+                self._fd = os.makedirs(self.name)
+            except WindowsError as exc:
+                # could not create the dir
+                if exc.args[0] == 183:
+                    logger.debug('cannot create dir')
+                    # cannot create dir with existing name
+                    return False
+                else:
+                    raise
+            return self._is_one_pidfile()[0]
+
+        def _is_one_pidfile(self):
+            """
+            Returns True, pid if there is only one pidfile with the expected
+            base path
+
+            @rtype: tuple
+            """
+            pidfiles = glob.glob(self.LOCKBASE + '-*')
+            if len(pidfiles) == 1:
+                pid = pidfiles[0].split('-')[-1]
+                return True, int(pid)
+            else:
+                return False, None
+
+        def get_pid(self):
+            """
+            Returns the pid of the locking process
+
+            @rtype: int
+            """
+            # XXX assert there is only one?
+            _, pid = self._is_one_pidfile()
+            return pid
+
+        def release_lock(self):
+            """
+            Releases the pidfile dir for this process, by removing it.
+            """
+            try:
+                shutil.rmtree(self.name)
+                return True
+
+            except WindowsError as exc:
+                if exc.errno in (errno.EPIPE, errno.ENOENT,
+                                 errno.ESRCH, errno.EACCES):
+                    logger.warning(
+                        'exception while trying to remove the lockfile dir')
+                    logger.warning('errno %s: %s' % (exc.errno, exc.args[1]))
+                    # path does not exist
+                    return False
+                else:
+                    logger.debug('errno = %s' % (exc.errno,))
+                    # we did not foresee this error, better add it explicitely
+                    raise
+
+        @property
+        def locked_by_us(self):
+            """
+            Returns True if the pid in the pidfile
+            is ours.
+
+            @rtype: bool
+            """
+            _, pid = self._is_one_pidfile()
+            return pid == self.pid
+
+        def write_port(self, port):
+            """
+            Writes the port for windows control to the pidfile folder
+            Returns True if successful.
+
+            @rtype: bool
+            """
+            if not self.locked_by_us:
+                logger.warning("Tried to write control port to a "
+                               "non-unique pidfile folder")
+                return False
+            port_file = os.path.join(self.name, "port")
+            with open(port_file, 'w') as f:
+                f.write("%s" % port)
+            return True
+
+        def get_control_port(self):
+            """
+            Reads control port of the main instance from the port file
+            in the pidfile dir
+
+            @rtype: int
+            """
+            pid = self.get_pid()
+            port_file = os.path.join(self.LOCKBASE + "-%s" % pid, "port")
+            port = None
+            try:
+                with open(port_file) as f:
+                    port_str = f.read()
+                    port = int(port_str.strip())
+            except IOError as exc:
+                if exc.errno == errno.ENOENT:
+                    logger.error("Tried to read port from non-existent file")
+                else:
+                    # we did not know explicitely about this error
+                    raise
+            return port
+
+
+def we_are_the_one_and_only():
+    """
+    Returns True if we are the only instance running, False otherwise.
+    If we came later, send a raise signal to the main instance of the
+    application
+
+    @rtype: bool
+    """
+    _sys = platform.system()
+
+    if _sys in ("Linux", "Darwin"):
+        locker = UnixLock('/tmp/leap-client.lock')
+        locker.get_lock()
+        we_are_the_one = locker.locked_by_us
+        if not we_are_the_one:
+            signal_event(proto.RAISE_WINDOW)
+        return we_are_the_one
+
+    elif _sys == "Windows":
+        locker = WindowsLock()
+        locker.get_lock()
+        we_are_the_one = locker.locked_by_us
+        if not we_are_the_one:
+            locker.release_lock()
+            signal_event(proto.RAISE_WINDOW)
+        return we_are_the_one
+
+    else:
+        logger.warning("Multi-instance checker "
+                       "not implemented for %s" % (_sys))
+        # lies, lies, lies...
+        return True