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package dbus
import (
"context"
"errors"
"io"
"os"
"strings"
"sync"
)
var (
systemBus *Conn
systemBusLck sync.Mutex
sessionBus *Conn
sessionBusLck sync.Mutex
)
// ErrClosed is the error returned by calls on a closed connection.
var ErrClosed = errors.New("dbus: connection closed by user")
// Conn represents a connection to a message bus (usually, the system or
// session bus).
//
// Connections are either shared or private. Shared connections
// are shared between calls to the functions that return them. As a result,
// the methods Close, Auth and Hello must not be called on them.
//
// Multiple goroutines may invoke methods on a connection simultaneously.
type Conn struct {
transport
busObj BusObject
unixFD bool
uuid string
handler Handler
signalHandler SignalHandler
serialGen SerialGenerator
inInt Interceptor
outInt Interceptor
names *nameTracker
calls *callTracker
outHandler *outputHandler
eavesdropped chan<- *Message
eavesdroppedLck sync.Mutex
}
// SessionBus returns a shared connection to the session bus, connecting to it
// if not already done.
func SessionBus() (conn *Conn, err error) {
sessionBusLck.Lock()
defer sessionBusLck.Unlock()
if sessionBus != nil {
return sessionBus, nil
}
defer func() {
if conn != nil {
sessionBus = conn
}
}()
conn, err = SessionBusPrivate()
if err != nil {
return
}
if err = conn.Auth(nil); err != nil {
conn.Close()
conn = nil
return
}
if err = conn.Hello(); err != nil {
conn.Close()
conn = nil
}
return
}
func getSessionBusAddress() (string, error) {
if address := os.Getenv("DBUS_SESSION_BUS_ADDRESS"); address != "" && address != "autolaunch:" {
return address, nil
} else if address := tryDiscoverDbusSessionBusAddress(); address != "" {
os.Setenv("DBUS_SESSION_BUS_ADDRESS", address)
return address, nil
}
return getSessionBusPlatformAddress()
}
// SessionBusPrivate returns a new private connection to the session bus.
func SessionBusPrivate(opts ...ConnOption) (*Conn, error) {
address, err := getSessionBusAddress()
if err != nil {
return nil, err
}
return Dial(address, opts...)
}
// SessionBusPrivate returns a new private connection to the session bus.
//
// Deprecated: use SessionBusPrivate with options instead.
func SessionBusPrivateHandler(handler Handler, signalHandler SignalHandler) (*Conn, error) {
return SessionBusPrivate(WithHandler(handler), WithSignalHandler(signalHandler))
}
// SystemBus returns a shared connection to the system bus, connecting to it if
// not already done.
func SystemBus() (conn *Conn, err error) {
systemBusLck.Lock()
defer systemBusLck.Unlock()
if systemBus != nil {
return systemBus, nil
}
defer func() {
if conn != nil {
systemBus = conn
}
}()
conn, err = SystemBusPrivate()
if err != nil {
return
}
if err = conn.Auth(nil); err != nil {
conn.Close()
conn = nil
return
}
if err = conn.Hello(); err != nil {
conn.Close()
conn = nil
}
return
}
// SystemBusPrivate returns a new private connection to the system bus.
// Note: this connection is not ready to use. One must perform Auth and Hello
// on the connection before it is useable.
func SystemBusPrivate(opts ...ConnOption) (*Conn, error) {
return Dial(getSystemBusPlatformAddress(), opts...)
}
// SystemBusPrivateHandler returns a new private connection to the system bus, using the provided handlers.
//
// Deprecated: use SystemBusPrivate with options instead.
func SystemBusPrivateHandler(handler Handler, signalHandler SignalHandler) (*Conn, error) {
return SystemBusPrivate(WithHandler(handler), WithSignalHandler(signalHandler))
}
// Dial establishes a new private connection to the message bus specified by address.
func Dial(address string, opts ...ConnOption) (*Conn, error) {
tr, err := getTransport(address)
if err != nil {
return nil, err
}
return newConn(tr, opts...)
}
// DialHandler establishes a new private connection to the message bus specified by address, using the supplied handlers.
//
// Deprecated: use Dial with options instead.
func DialHandler(address string, handler Handler, signalHandler SignalHandler) (*Conn, error) {
return Dial(address, WithSignalHandler(signalHandler))
}
// ConnOption is a connection option.
type ConnOption func(conn *Conn) error
// WithHandler overrides the default handler.
func WithHandler(handler Handler) ConnOption {
return func(conn *Conn) error {
conn.handler = handler
return nil
}
}
// WithSignalHandler overrides the default signal handler.
func WithSignalHandler(handler SignalHandler) ConnOption {
return func(conn *Conn) error {
conn.signalHandler = handler
return nil
}
}
// WithSerialGenerator overrides the default signals generator.
func WithSerialGenerator(gen SerialGenerator) ConnOption {
return func(conn *Conn) error {
conn.serialGen = gen
return nil
}
}
// Interceptor intercepts incoming and outgoing messages.
type Interceptor func(msg *Message)
// WithIncomingInterceptor sets the given interceptor for incoming messages.
func WithIncomingInterceptor(interceptor Interceptor) ConnOption {
return func(conn *Conn) error {
conn.inInt = interceptor
return nil
}
}
// WithOutgoingInterceptor sets the given interceptor for outgoing messages.
func WithOutgoingInterceptor(interceptor Interceptor) ConnOption {
return func(conn *Conn) error {
conn.outInt = interceptor
return nil
}
}
// NewConn creates a new private *Conn from an already established connection.
func NewConn(conn io.ReadWriteCloser, opts ...ConnOption) (*Conn, error) {
return newConn(genericTransport{conn}, opts...)
}
// NewConnHandler creates a new private *Conn from an already established connection, using the supplied handlers.
//
// Deprecated: use NewConn with options instead.
func NewConnHandler(conn io.ReadWriteCloser, handler Handler, signalHandler SignalHandler) (*Conn, error) {
return NewConn(genericTransport{conn}, WithHandler(handler), WithSignalHandler(signalHandler))
}
// newConn creates a new *Conn from a transport.
func newConn(tr transport, opts ...ConnOption) (*Conn, error) {
conn := new(Conn)
conn.transport = tr
for _, opt := range opts {
if err := opt(conn); err != nil {
return nil, err
}
}
conn.calls = newCallTracker()
if conn.handler == nil {
conn.handler = NewDefaultHandler()
}
if conn.signalHandler == nil {
conn.signalHandler = NewDefaultSignalHandler()
}
if conn.serialGen == nil {
conn.serialGen = newSerialGenerator()
}
conn.outHandler = &outputHandler{conn: conn}
conn.names = newNameTracker()
conn.busObj = conn.Object("org.freedesktop.DBus", "/org/freedesktop/DBus")
return conn, nil
}
// BusObject returns the object owned by the bus daemon which handles
// administrative requests.
func (conn *Conn) BusObject() BusObject {
return conn.busObj
}
// Close closes the connection. Any blocked operations will return with errors
// and the channels passed to Eavesdrop and Signal are closed. This method must
// not be called on shared connections.
func (conn *Conn) Close() error {
conn.outHandler.close()
if term, ok := conn.signalHandler.(Terminator); ok {
term.Terminate()
}
if term, ok := conn.handler.(Terminator); ok {
term.Terminate()
}
conn.eavesdroppedLck.Lock()
if conn.eavesdropped != nil {
close(conn.eavesdropped)
}
conn.eavesdroppedLck.Unlock()
return conn.transport.Close()
}
// Eavesdrop causes conn to send all incoming messages to the given channel
// without further processing. Method replies, errors and signals will not be
// sent to the appropriate channels and method calls will not be handled. If nil
// is passed, the normal behaviour is restored.
//
// The caller has to make sure that ch is sufficiently buffered;
// if a message arrives when a write to ch is not possible, the message is
// discarded.
func (conn *Conn) Eavesdrop(ch chan<- *Message) {
conn.eavesdroppedLck.Lock()
conn.eavesdropped = ch
conn.eavesdroppedLck.Unlock()
}
// getSerial returns an unused serial.
func (conn *Conn) getSerial() uint32 {
return conn.serialGen.GetSerial()
}
// Hello sends the initial org.freedesktop.DBus.Hello call. This method must be
// called after authentication, but before sending any other messages to the
// bus. Hello must not be called for shared connections.
func (conn *Conn) Hello() error {
var s string
err := conn.busObj.Call("org.freedesktop.DBus.Hello", 0).Store(&s)
if err != nil {
return err
}
conn.names.acquireUniqueConnectionName(s)
return nil
}
// inWorker runs in an own goroutine, reading incoming messages from the
// transport and dispatching them appropiately.
func (conn *Conn) inWorker() {
for {
msg, err := conn.ReadMessage()
if err != nil {
if _, ok := err.(InvalidMessageError); !ok {
// Some read error occurred (usually EOF); we can't really do
// anything but to shut down all stuff and returns errors to all
// pending replies.
conn.Close()
conn.calls.finalizeAllWithError(err)
return
}
// invalid messages are ignored
continue
}
conn.eavesdroppedLck.Lock()
if conn.eavesdropped != nil {
select {
case conn.eavesdropped <- msg:
default:
}
conn.eavesdroppedLck.Unlock()
continue
}
conn.eavesdroppedLck.Unlock()
dest, _ := msg.Headers[FieldDestination].value.(string)
found := dest == "" ||
!conn.names.uniqueNameIsKnown() ||
conn.names.isKnownName(dest)
if !found {
// Eavesdropped a message, but no channel for it is registered.
// Ignore it.
continue
}
if conn.inInt != nil {
conn.inInt(msg)
}
switch msg.Type {
case TypeError:
conn.serialGen.RetireSerial(conn.calls.handleDBusError(msg))
case TypeMethodReply:
conn.serialGen.RetireSerial(conn.calls.handleReply(msg))
case TypeSignal:
conn.handleSignal(msg)
case TypeMethodCall:
go conn.handleCall(msg)
}
}
}
func (conn *Conn) handleSignal(msg *Message) {
iface := msg.Headers[FieldInterface].value.(string)
member := msg.Headers[FieldMember].value.(string)
// as per http://dbus.freedesktop.org/doc/dbus-specification.html ,
// sender is optional for signals.
sender, _ := msg.Headers[FieldSender].value.(string)
if iface == "org.freedesktop.DBus" && sender == "org.freedesktop.DBus" {
if member == "NameLost" {
// If we lost the name on the bus, remove it from our
// tracking list.
name, ok := msg.Body[0].(string)
if !ok {
panic("Unable to read the lost name")
}
conn.names.loseName(name)
} else if member == "NameAcquired" {
// If we acquired the name on the bus, add it to our
// tracking list.
name, ok := msg.Body[0].(string)
if !ok {
panic("Unable to read the acquired name")
}
conn.names.acquireName(name)
}
}
signal := &Signal{
Sender: sender,
Path: msg.Headers[FieldPath].value.(ObjectPath),
Name: iface + "." + member,
Body: msg.Body,
}
conn.signalHandler.DeliverSignal(iface, member, signal)
}
// Names returns the list of all names that are currently owned by this
// connection. The slice is always at least one element long, the first element
// being the unique name of the connection.
func (conn *Conn) Names() []string {
return conn.names.listKnownNames()
}
// Object returns the object identified by the given destination name and path.
func (conn *Conn) Object(dest string, path ObjectPath) BusObject {
return &Object{conn, dest, path}
}
func (conn *Conn) sendMessageAndIfClosed(msg *Message, ifClosed func()) {
if conn.outInt != nil {
conn.outInt(msg)
}
err := conn.outHandler.sendAndIfClosed(msg, ifClosed)
conn.calls.handleSendError(msg, err)
if err != nil {
conn.serialGen.RetireSerial(msg.serial)
} else if msg.Type != TypeMethodCall {
conn.serialGen.RetireSerial(msg.serial)
}
}
// Send sends the given message to the message bus. You usually don't need to
// use this; use the higher-level equivalents (Call / Go, Emit and Export)
// instead. If msg is a method call and NoReplyExpected is not set, a non-nil
// call is returned and the same value is sent to ch (which must be buffered)
// once the call is complete. Otherwise, ch is ignored and a Call structure is
// returned of which only the Err member is valid.
func (conn *Conn) Send(msg *Message, ch chan *Call) *Call {
return conn.send(context.Background(), msg, ch)
}
// SendWithContext acts like Send but takes a context
func (conn *Conn) SendWithContext(ctx context.Context, msg *Message, ch chan *Call) *Call {
return conn.send(ctx, msg, ch)
}
func (conn *Conn) send(ctx context.Context, msg *Message, ch chan *Call) *Call {
if ctx == nil {
panic("nil context")
}
var call *Call
ctx, canceler := context.WithCancel(ctx)
msg.serial = conn.getSerial()
if msg.Type == TypeMethodCall && msg.Flags&FlagNoReplyExpected == 0 {
if ch == nil {
ch = make(chan *Call, 5)
} else if cap(ch) == 0 {
panic("dbus: unbuffered channel passed to (*Conn).Send")
}
call = new(Call)
call.Destination, _ = msg.Headers[FieldDestination].value.(string)
call.Path, _ = msg.Headers[FieldPath].value.(ObjectPath)
iface, _ := msg.Headers[FieldInterface].value.(string)
member, _ := msg.Headers[FieldMember].value.(string)
call.Method = iface + "." + member
call.Args = msg.Body
call.Done = ch
call.ctx = ctx
call.ctxCanceler = canceler
conn.calls.track(msg.serial, call)
go func() {
<-ctx.Done()
conn.calls.handleSendError(msg, ctx.Err())
}()
conn.sendMessageAndIfClosed(msg, func() {
conn.calls.handleSendError(msg, ErrClosed)
canceler()
})
} else {
canceler()
call = &Call{Err: nil}
conn.sendMessageAndIfClosed(msg, func() {
call = &Call{Err: ErrClosed}
})
}
return call
}
// sendError creates an error message corresponding to the parameters and sends
// it to conn.out.
func (conn *Conn) sendError(err error, dest string, serial uint32) {
var e *Error
switch em := err.(type) {
case Error:
e = &em
case *Error:
e = em
case DBusError:
name, body := em.DBusError()
e = NewError(name, body)
default:
e = MakeFailedError(err)
}
msg := new(Message)
msg.Type = TypeError
msg.serial = conn.getSerial()
msg.Headers = make(map[HeaderField]Variant)
if dest != "" {
msg.Headers[FieldDestination] = MakeVariant(dest)
}
msg.Headers[FieldErrorName] = MakeVariant(e.Name)
msg.Headers[FieldReplySerial] = MakeVariant(serial)
msg.Body = e.Body
if len(e.Body) > 0 {
msg.Headers[FieldSignature] = MakeVariant(SignatureOf(e.Body...))
}
conn.sendMessageAndIfClosed(msg, nil)
}
// sendReply creates a method reply message corresponding to the parameters and
// sends it to conn.out.
func (conn *Conn) sendReply(dest string, serial uint32, values ...interface{}) {
msg := new(Message)
msg.Type = TypeMethodReply
msg.serial = conn.getSerial()
msg.Headers = make(map[HeaderField]Variant)
if dest != "" {
msg.Headers[FieldDestination] = MakeVariant(dest)
}
msg.Headers[FieldReplySerial] = MakeVariant(serial)
msg.Body = values
if len(values) > 0 {
msg.Headers[FieldSignature] = MakeVariant(SignatureOf(values...))
}
conn.sendMessageAndIfClosed(msg, nil)
}
// AddMatchSignal registers the given match rule to receive broadcast
// signals based on their contents.
func (conn *Conn) AddMatchSignal(options ...MatchOption) error {
options = append([]MatchOption{withMatchType("signal")}, options...)
return conn.busObj.Call(
"org.freedesktop.DBus.AddMatch", 0,
formatMatchOptions(options),
).Store()
}
// RemoveMatchSignal removes the first rule that matches previously registered with AddMatchSignal.
func (conn *Conn) RemoveMatchSignal(options ...MatchOption) error {
options = append([]MatchOption{withMatchType("signal")}, options...)
return conn.busObj.Call(
"org.freedesktop.DBus.RemoveMatch", 0,
formatMatchOptions(options),
).Store()
}
// Signal registers the given channel to be passed all received signal messages.
//
// Multiple of these channels can be registered at the same time.
//
// These channels are "overwritten" by Eavesdrop; i.e., if there currently is a
// channel for eavesdropped messages, this channel receives all signals, and
// none of the channels passed to Signal will receive any signals.
//
// Panics if the signal handler is not a `SignalRegistrar`.
func (conn *Conn) Signal(ch chan<- *Signal) {
handler, ok := conn.signalHandler.(SignalRegistrar)
if !ok {
panic("cannot use this method with a non SignalRegistrar handler")
}
handler.AddSignal(ch)
}
// RemoveSignal removes the given channel from the list of the registered channels.
//
// Panics if the signal handler is not a `SignalRegistrar`.
func (conn *Conn) RemoveSignal(ch chan<- *Signal) {
handler, ok := conn.signalHandler.(SignalRegistrar)
if !ok {
panic("cannot use this method with a non SignalRegistrar handler")
}
handler.RemoveSignal(ch)
}
// SupportsUnixFDs returns whether the underlying transport supports passing of
// unix file descriptors. If this is false, method calls containing unix file
// descriptors will return an error and emitted signals containing them will
// not be sent.
func (conn *Conn) SupportsUnixFDs() bool {
return conn.unixFD
}
// Error represents a D-Bus message of type Error.
type Error struct {
Name string
Body []interface{}
}
func NewError(name string, body []interface{}) *Error {
return &Error{name, body}
}
func (e Error) Error() string {
if len(e.Body) >= 1 {
s, ok := e.Body[0].(string)
if ok {
return s
}
}
return e.Name
}
// Signal represents a D-Bus message of type Signal. The name member is given in
// "interface.member" notation, e.g. org.freedesktop.D-Bus.NameLost.
type Signal struct {
Sender string
Path ObjectPath
Name string
Body []interface{}
}
// transport is a D-Bus transport.
type transport interface {
// Read and Write raw data (for example, for the authentication protocol).
io.ReadWriteCloser
// Send the initial null byte used for the EXTERNAL mechanism.
SendNullByte() error
// Returns whether this transport supports passing Unix FDs.
SupportsUnixFDs() bool
// Signal the transport that Unix FD passing is enabled for this connection.
EnableUnixFDs()
// Read / send a message, handling things like Unix FDs.
ReadMessage() (*Message, error)
SendMessage(*Message) error
}
var (
transports = make(map[string]func(string) (transport, error))
)
func getTransport(address string) (transport, error) {
var err error
var t transport
addresses := strings.Split(address, ";")
for _, v := range addresses {
i := strings.IndexRune(v, ':')
if i == -1 {
err = errors.New("dbus: invalid bus address (no transport)")
continue
}
f := transports[v[:i]]
if f == nil {
err = errors.New("dbus: invalid bus address (invalid or unsupported transport)")
continue
}
t, err = f(v[i+1:])
if err == nil {
return t, nil
}
}
return nil, err
}
// getKey gets a key from a the list of keys. Returns "" on error / not found...
func getKey(s, key string) string {
for _, keyEqualsValue := range strings.Split(s, ",") {
keyValue := strings.SplitN(keyEqualsValue, "=", 2)
if len(keyValue) == 2 && keyValue[0] == key {
return keyValue[1]
}
}
return ""
}
type outputHandler struct {
conn *Conn
sendLck sync.Mutex
closed struct {
isClosed bool
lck sync.RWMutex
}
}
func (h *outputHandler) sendAndIfClosed(msg *Message, ifClosed func()) error {
h.closed.lck.RLock()
defer h.closed.lck.RUnlock()
if h.closed.isClosed {
if ifClosed != nil {
ifClosed()
}
return nil
}
h.sendLck.Lock()
defer h.sendLck.Unlock()
return h.conn.SendMessage(msg)
}
func (h *outputHandler) close() {
h.closed.lck.Lock()
defer h.closed.lck.Unlock()
h.closed.isClosed = true
}
type serialGenerator struct {
lck sync.Mutex
nextSerial uint32
serialUsed map[uint32]bool
}
func newSerialGenerator() *serialGenerator {
return &serialGenerator{
serialUsed: map[uint32]bool{0: true},
nextSerial: 1,
}
}
func (gen *serialGenerator) GetSerial() uint32 {
gen.lck.Lock()
defer gen.lck.Unlock()
n := gen.nextSerial
for gen.serialUsed[n] {
n++
}
gen.serialUsed[n] = true
gen.nextSerial = n + 1
return n
}
func (gen *serialGenerator) RetireSerial(serial uint32) {
gen.lck.Lock()
defer gen.lck.Unlock()
delete(gen.serialUsed, serial)
}
type nameTracker struct {
lck sync.RWMutex
unique string
names map[string]struct{}
}
func newNameTracker() *nameTracker {
return &nameTracker{names: map[string]struct{}{}}
}
func (tracker *nameTracker) acquireUniqueConnectionName(name string) {
tracker.lck.Lock()
defer tracker.lck.Unlock()
tracker.unique = name
}
func (tracker *nameTracker) acquireName(name string) {
tracker.lck.Lock()
defer tracker.lck.Unlock()
tracker.names[name] = struct{}{}
}
func (tracker *nameTracker) loseName(name string) {
tracker.lck.Lock()
defer tracker.lck.Unlock()
delete(tracker.names, name)
}
func (tracker *nameTracker) uniqueNameIsKnown() bool {
tracker.lck.RLock()
defer tracker.lck.RUnlock()
return tracker.unique != ""
}
func (tracker *nameTracker) isKnownName(name string) bool {
tracker.lck.RLock()
defer tracker.lck.RUnlock()
_, ok := tracker.names[name]
return ok || name == tracker.unique
}
func (tracker *nameTracker) listKnownNames() []string {
tracker.lck.RLock()
defer tracker.lck.RUnlock()
out := make([]string, 0, len(tracker.names)+1)
out = append(out, tracker.unique)
for k := range tracker.names {
out = append(out, k)
}
return out
}
type callTracker struct {
calls map[uint32]*Call
lck sync.RWMutex
}
func newCallTracker() *callTracker {
return &callTracker{calls: map[uint32]*Call{}}
}
func (tracker *callTracker) track(sn uint32, call *Call) {
tracker.lck.Lock()
tracker.calls[sn] = call
tracker.lck.Unlock()
}
func (tracker *callTracker) handleReply(msg *Message) uint32 {
serial := msg.Headers[FieldReplySerial].value.(uint32)
tracker.lck.RLock()
_, ok := tracker.calls[serial]
tracker.lck.RUnlock()
if ok {
tracker.finalizeWithBody(serial, msg.Body)
}
return serial
}
func (tracker *callTracker) handleDBusError(msg *Message) uint32 {
serial := msg.Headers[FieldReplySerial].value.(uint32)
tracker.lck.RLock()
_, ok := tracker.calls[serial]
tracker.lck.RUnlock()
if ok {
name, _ := msg.Headers[FieldErrorName].value.(string)
tracker.finalizeWithError(serial, Error{name, msg.Body})
}
return serial
}
func (tracker *callTracker) handleSendError(msg *Message, err error) {
if err == nil {
return
}
tracker.lck.RLock()
_, ok := tracker.calls[msg.serial]
tracker.lck.RUnlock()
if ok {
tracker.finalizeWithError(msg.serial, err)
}
}
// finalize was the only func that did not strobe Done
func (tracker *callTracker) finalize(sn uint32) {
tracker.lck.Lock()
defer tracker.lck.Unlock()
c, ok := tracker.calls[sn]
if ok {
delete(tracker.calls, sn)
c.ContextCancel()
}
}
func (tracker *callTracker) finalizeWithBody(sn uint32, body []interface{}) {
tracker.lck.Lock()
c, ok := tracker.calls[sn]
if ok {
delete(tracker.calls, sn)
}
tracker.lck.Unlock()
if ok {
c.Body = body
c.done()
}
}
func (tracker *callTracker) finalizeWithError(sn uint32, err error) {
tracker.lck.Lock()
c, ok := tracker.calls[sn]
if ok {
delete(tracker.calls, sn)
}
tracker.lck.Unlock()
if ok {
c.Err = err
c.done()
}
}
func (tracker *callTracker) finalizeAllWithError(err error) {
tracker.lck.Lock()
closedCalls := make([]*Call, 0, len(tracker.calls))
for sn := range tracker.calls {
closedCalls = append(closedCalls, tracker.calls[sn])
}
tracker.calls = map[uint32]*Call{}
tracker.lck.Unlock()
for _, call := range closedCalls {
call.Err = err
call.done()
}
}
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