github.com/meulengracht/snapd@v0.0.0-20210719210640-8bde69bcc84e/usersession/userd/userd.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2017 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package userd
    21  
    22  import (
    23  	"fmt"
    24  
    25  	"github.com/godbus/dbus"
    26  	"github.com/godbus/dbus/introspect"
    27  	"gopkg.in/tomb.v2"
    28  
    29  	"github.com/snapcore/snapd/dbusutil"
    30  	"github.com/snapcore/snapd/logger"
    31  )
    32  
    33  type dbusInterface interface {
    34  	Interface() string
    35  	ObjectPath() dbus.ObjectPath
    36  	IntrospectionData() string
    37  }
    38  
    39  type Userd struct {
    40  	tomb       tomb.Tomb
    41  	conn       *dbus.Conn
    42  	dbusIfaces []dbusInterface
    43  }
    44  
    45  // userdBusNames contains the list of bus names userd will acquire on
    46  // the session bus.  It is unnecessary (and undesirable) to add more
    47  // names here when adding new interfaces to the daemon.
    48  var userdBusNames = []string{
    49  	"io.snapcraft.Launcher",
    50  	"io.snapcraft.Settings",
    51  }
    52  
    53  func (ud *Userd) Init() error {
    54  	var err error
    55  
    56  	ud.conn, err = dbusutil.SessionBusPrivate()
    57  	if err != nil {
    58  		return err
    59  	}
    60  
    61  	ud.dbusIfaces = []dbusInterface{
    62  		&Launcher{ud.conn},
    63  		&PrivilegedDesktopLauncher{ud.conn},
    64  		&Settings{ud.conn},
    65  	}
    66  	for _, iface := range ud.dbusIfaces {
    67  		// export the interfaces at the godbus API level first to avoid
    68  		// the race between being able to handle a call to an interface
    69  		// at the object level and the actual well-known object name
    70  		// becoming available on the bus
    71  		xml := "<node>" + iface.IntrospectionData() + introspect.IntrospectDataString + "</node>"
    72  		ud.conn.Export(iface, iface.ObjectPath(), iface.Interface())
    73  		ud.conn.Export(introspect.Introspectable(xml), iface.ObjectPath(), "org.freedesktop.DBus.Introspectable")
    74  
    75  	}
    76  
    77  	for _, name := range userdBusNames {
    78  		// beyond this point the name is available and all handlers must
    79  		// have been set up
    80  		reply, err := ud.conn.RequestName(name, dbus.NameFlagDoNotQueue)
    81  		if err != nil {
    82  			return err
    83  		}
    84  
    85  		if reply != dbus.RequestNameReplyPrimaryOwner {
    86  			return fmt.Errorf("cannot obtain bus name '%s'", name)
    87  		}
    88  	}
    89  	return nil
    90  }
    91  
    92  func (ud *Userd) Start() {
    93  	logger.Noticef("Starting snap userd")
    94  
    95  	ud.tomb.Go(func() error {
    96  		// Listen to keep our thread up and running. All DBus bits
    97  		// are running in the background
    98  		<-ud.tomb.Dying()
    99  		ud.conn.Close()
   100  
   101  		err := ud.tomb.Err()
   102  		if err != nil && err != tomb.ErrStillAlive {
   103  			return err
   104  		}
   105  		return nil
   106  	})
   107  }
   108  
   109  func (ud *Userd) Stop() error {
   110  	ud.tomb.Kill(nil)
   111  	return ud.tomb.Wait()
   112  }
   113  
   114  func (ud *Userd) Dying() <-chan struct{} {
   115  	return ud.tomb.Dying()
   116  }