-<?xml version="1.0" standalone="no"?>
+<?xml version="1.0" standalone="no" ?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
[
<article id="index">
<articleinfo>
- <title>D-BUS Specification</title>
- <releaseinfo>Version 0.11</releaseinfo>
- <date>6 February 2005</date>
+ <title>D-Bus Specification</title>
+ <releaseinfo>Version 0.14</releaseinfo>
+ <date>May 12, 2010</date>
<authorgroup>
<author>
<firstname>Havoc</firstname>
<sect1 id="introduction">
<title>Introduction</title>
<para>
- D-BUS is a system for low-latency, low-overhead, easy to use
+ D-Bus is a system for low-latency, low-overhead, easy to use
interprocess communication (IPC). In more detail:
<itemizedlist>
<listitem>
<para>
- D-BUS is <emphasis>low-latency</emphasis> because it is designed
+ D-Bus is <emphasis>low-latency</emphasis> because it is designed
to avoid round trips and allow asynchronous operation, much like
the X protocol.
</para>
</listitem>
<listitem>
<para>
- D-BUS is <emphasis>low-overhead</emphasis> because it uses a
+ D-Bus is <emphasis>low-overhead</emphasis> because it uses a
binary protocol, and does not have to convert to and from a text
- format such as XML. Because D-BUS is intended for potentially
+ format such as XML. Because D-Bus is intended for potentially
high-resolution same-machine IPC, not primarily for Internet IPC,
this is an interesting optimization.
</para>
</listitem>
<listitem>
<para>
- D-BUS is <emphasis>easy to use</emphasis> because it works in terms
+ D-Bus is <emphasis>easy to use</emphasis> because it works in terms
of <firstterm>messages</firstterm> rather than byte streams, and
- automatically handles a lot of the hard IPC issues. Also, the D-BUS
+ automatically handles a lot of the hard IPC issues. Also, the D-Bus
library is designed to be wrapped in a way that lets developers use
their framework's existing object/type system, rather than learning
a new one specifically for IPC.
</para>
<para>
- The base D-BUS protocol is a one-to-one (peer-to-peer or client-server)
+ The base D-Bus protocol is a one-to-one (peer-to-peer or client-server)
protocol, specified in <xref linkend="message-protocol"/>. That is, it is
a system for one application to talk to a single other
application. However, the primary intended application of the protocol is the
- D-BUS <firstterm>message bus</firstterm>, specified in <xref
+ D-Bus <firstterm>message bus</firstterm>, specified in <xref
linkend="message-bus"/>. The message bus is a special application that
accepts connections from multiple other applications, and forwards
messages among them.
</para>
<para>
- Uses of D-BUS include notification of system changes (notification of when
+ Uses of D-Bus include notification of system changes (notification of when
a camera is plugged in to a computer, or a new version of some software
has been installed), or desktop interoperability, for example a file
monitoring service or a configuration service.
</para>
<para>
- D-BUS is designed for two specific use cases:
+ D-Bus is designed for two specific use cases:
<itemizedlist>
<listitem>
<para>
</para>
</listitem>
</itemizedlist>
- D-BUS is not intended to be a generic IPC system for any possible
+ D-Bus is not intended to be a generic IPC system for any possible
application, and intentionally omits many features found in other
- IPC systems for this reason. D-BUS may turn out to be useful
- in unanticipated applications, but future versions of this
- spec and the reference implementation probably will not
+ IPC systems for this reason.
+ </para>
+
+ <para>
+ At the same time, the bus daemons offer a number of features not found in
+ other IPC systems, such as single-owner "bus names" (similar to X
+ selections), on-demand startup of services, and security policies.
+ In many ways, these features are the primary motivation for developing
+ D-Bus; other systems would have sufficed if IPC were the only goal.
+ </para>
+
+ <para>
+ D-Bus may turn out to be useful in unanticipated applications, but future
+ versions of this spec and the reference implementation probably will not
incorporate features that interfere with the core use cases.
</para>
document could use a serious audit to be sure it makes sense to do
so. Also, they are not capitalized.
</para>
+
+ <sect2 id="stability">
+ <title>Protocol and Specification Stability</title>
+ <para>
+ The D-Bus protocol is frozen (only compatible extensions are allowed) as
+ of November 8, 2006. However, this specification could still use a fair
+ bit of work to make interoperable reimplementation possible without
+ reference to the D-Bus reference implementation. Thus, this
+ specification is not marked 1.0. To mark it 1.0, we'd like to see
+ someone invest significant effort in clarifying the specification
+ language, and growing the specification to cover more aspects of the
+ reference implementation's behavior.
+ </para>
+ <para>
+ Until this work is complete, any attempt to reimplement D-Bus will
+ probably require looking at the reference implementation and/or asking
+ questions on the D-Bus mailing list about intended behavior.
+ Questions on the list are very welcome.
+ </para>
+ <para>
+ Nonetheless, this document should be a useful starting point and is
+ to our knowledge accurate, though incomplete.
+ </para>
+ </sect2>
</sect1>
think of a message as a package, the header is the address, and the body
contains the package contents. The message delivery system uses the header
information to figure out where to send the message and how to interpret
- it; the recipient inteprets the body of the message.
+ it; the recipient interprets the body of the message.
</para>
<para>
<title>Type Signatures</title>
<para>
- The D-BUS protocol does not include type tags in the marshaled data; a
+ The D-Bus protocol does not include type tags in the marshaled data; a
block of marshaled values must have a known <firstterm>type
signature</firstterm>. The type signature is made up of <firstterm>type
codes</firstterm>. A type code is an ASCII character representing the
</para>
<para>
- The <literal>STRUCT</literal> type code 'r' is not currently used in the D-BUS protocol,
+ The <literal>STRUCT</literal> type code 'r' is not currently used in the D-Bus protocol,
but is useful in code that implements the protocol. This type code
is specified to allow such code to interoperate in non-protocol contexts.
</para>
-
+
+ <para>
+ Empty structures are not allowed; there must be at least one
+ type code between the parentheses.
+ </para>
+
<para>
<literal>ARRAY</literal> has ASCII character 'a' as type code. The array type code must be
followed by a <firstterm>single complete type</firstterm>. The single
</para>
<para>
- The following table summarizes the D-BUS types.
+ The following table summarizes the D-Bus types.
<informaltable>
<tgroup cols="3">
<thead>
</row><row>
<entry><literal>STRING</literal></entry>
<entry>115 (ASCII 's')</entry>
- <entry>UTF-8 string (<emphasis>must</emphasis> be valid UTF-8). Must be nul terminated.</entry>
+ <entry>UTF-8 string (<emphasis>must</emphasis> be valid UTF-8). Must be nul terminated and contain no other nul bytes.</entry>
</row><row>
<entry><literal>OBJECT_PATH</literal></entry>
<entry>111 (ASCII 'o')</entry>
<entry><literal>DICT_ENTRY</literal></entry>
<entry>101 (ASCII 'e'), 123 (ASCII '{'), 125 (ASCII '}') </entry>
<entry>Entry in a dict or map (array of key-value pairs)</entry>
+ </row><row>
+ <entry><literal>UNIX_FD</literal></entry>
+ <entry>104 (ASCII 'h')</entry>
+ <entry>Unix file descriptor</entry>
</row>
</tbody>
</tgroup>
<para>
Given a type signature, a block of bytes can be converted into typed
values. This section describes the format of the block of bytes. Byte
- order and alignment issues are handled uniformly for all D-BUS types.
+ order and alignment issues are handled uniformly for all D-Bus types.
</para>
<para>
A block of bytes has an associated byte order. The byte order
- has to be discovered in some way; for D-BUS messages, the
+ has to be discovered in some way; for D-Bus messages, the
byte order is part of the message header as described in
<xref linkend="message-protocol-messages"/>. For now, assume
that the byte order is known to be either little endian or big
<entry><literal>STRING</literal></entry>
<entry>A <literal>UINT32</literal> indicating the string's
length in bytes excluding its terminating nul, followed by
- string data of the given length, followed by a terminating nul
+ non-nul string data of the given length, followed by a terminating nul
byte.
</entry>
<entry>
given in the signature.
Unlike a message signature, the variant signature
can contain only a single complete type.
- So "i" is OK, "ii" is not.
+ So "i", "ai" or "(ii)" is OK, but "ii" is not.
</entry>
<entry>
1 (alignment of the signature)
<entry>
8
</entry>
+ </row><row>
+ <entry><literal>UNIX_FD</literal></entry>
+ <entry>32-bit unsigned integer in the message's byte
+ order. The actual file descriptors need to be
+ transferred out-of-band via some platform specific
+ mechanism. On the wire, values of this type store the index to the
+ file descriptor in the array of file descriptors that
+ accompany the message.</entry>
+ <entry>4</entry>
</row>
</tbody>
</tgroup>
<para>
An object path is a name used to refer to an object instance.
- Conceptually, each participant in a D-BUS message exchange may have
+ Conceptually, each participant in a D-Bus message exchange may have
any number of object instances (think of C++ or Java objects) and each
such instance will have a path. Like a filesystem, the object
instances in an application form a hierarchical tree.
<entry>Major protocol version of the sending application. If
the major protocol version of the receiving application does not
match, the applications will not be able to communicate and the
- D-BUS connection must be disconnected. The major protocol
- version for this version of the specification is 0.
- FIXME this field is stupid and pointless to put in
- every message.
+ D-Bus connection must be disconnected. The major protocol
+ version for this version of the specification is 1.
</entry>
</row>
<row>
<entry>2nd <literal>UINT32</literal></entry>
<entry>The serial of this message, used as a cookie
by the sender to identify the reply corresponding
- to this request.
+ to this request. This must not be zero.
</entry>
</row>
<row>
<entry>1</entry>
<entry><literal>OBJECT_PATH</literal></entry>
<entry><literal>METHOD_CALL</literal>, <literal>SIGNAL</literal></entry>
- <entry>The object to send a call to,
+ <entry>The object to send a call to,
or the object a signal is emitted from.
+ The special path
+ <literal>/org/freedesktop/DBus/Local</literal> is reserved;
+ implementations should not send messages with this path,
+ and the reference implementation of the bus daemon will
+ disconnect any application that attempts to do so.
</entry>
</row>
<row>
The interface to invoke a method call on, or
that a signal is emitted from. Optional for
method calls, required for signals.
+ The special interface
+ <literal>org.freedesktop.DBus.Local</literal> is reserved;
+ implementations should not send messages with this
+ interface, and the reference implementation of the bus
+ daemon will disconnect any application that attempts to
+ do so.
</entry>
</row>
<row>
If omitted, it is assumed to be the
empty signature "" (i.e. the body must be 0-length).</entry>
</row>
+ <row>
+ <entry><literal>UNIX_FDS</literal></entry>
+ <entry>9</entry>
+ <entry><literal>UINT32</literal></entry>
+ <entry>optional</entry>
+ <entry>The number of Unix file descriptors that
+ accompany the message. If omitted, it is assumed
+ that no Unix file descriptors accompany the
+ message. The actual file descriptors need to be
+ transferred via platform specific mechanism
+ out-of-band. They must be sent at the same time as
+ part of the message itself. They may not be sent
+ before the first byte of the message itself is
+ transferred or after the last byte of the message
+ itself.</entry>
+ </row>
</tbody>
</tgroup>
</informaltable>
<sect2 id="message-protocol-names">
<title>Valid Names</title>
<para>
- The various names in D-BUS messages have some restrictions.
+ The various names in D-Bus messages have some restrictions.
</para>
<para>
There is a <firstterm>maximum name length</firstterm>
additional restrictions that apply to interface names
specifically:
<itemizedlist>
- <listitem><para>They are composed of 1 or more elements separated by
+ <listitem><para>Interface names are composed of 1 or more elements separated by
a period ('.') character. All elements must contain at least
one character.
</para>
</para>
</listitem>
- <listitem><para>They must contain at least one '.' (period)
+ <listitem><para>Interface names must contain at least one '.' (period)
character (and thus at least two elements).
</para></listitem>
- <listitem><para>They must not begin with a '.' (period) character.</para></listitem>
- <listitem><para>They must not exceed the maximum name length.</para></listitem>
+ <listitem><para>Interface names must not begin with a '.' (period) character.</para></listitem>
+ <listitem><para>Interface names must not exceed the maximum name length.</para></listitem>
</itemizedlist>
</para>
</sect3>
<sect3 id="message-protocol-names-bus">
<title>Bus names</title>
<para>
- Bus names have the same restrictions as interface names, with a
- special exception for unique connection names. A unique name's first
- element must start with a colon (':') character. After the colon, any
- characters in "[A-Z][a-z][0-9]_" may appear. Elements after
- the first must follow the usual rules, except that they may start with
- a digit. Bus names not starting with a colon have none of these
- exceptions and follow the same rules as interface names.
+ Connections have one or more bus names associated with them.
+ A connection has exactly one bus name that is a unique connection
+ name. The unique connection name remains with the connection for
+ its entire lifetime.
+ A bus name is of type <literal>STRING</literal>,
+ meaning that it must be valid UTF-8. However, there are also
+ some additional restrictions that apply to bus names
+ specifically:
+ <itemizedlist>
+ <listitem><para>Bus names that start with a colon (':')
+ character are unique connection names.
+ </para>
+ </listitem>
+ <listitem><para>Bus names are composed of 1 or more elements separated by
+ a period ('.') character. All elements must contain at least
+ one character.
+ </para>
+ </listitem>
+ <listitem><para>Each element must only contain the ASCII characters
+ "[A-Z][a-z][0-9]_-". Only elements that are part of a unique
+ connection name may begin with a digit, elements in
+ other bus names must not begin with a digit.
+ </para>
+ </listitem>
+
+ <listitem><para>Bus names must contain at least one '.' (period)
+ character (and thus at least two elements).
+ </para></listitem>
+
+ <listitem><para>Bus names must not begin with a '.' (period) character.</para></listitem>
+ <listitem><para>Bus names must not exceed the maximum name length.</para></listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ Note that the hyphen ('-') character is allowed in bus names but
+ not in interface names.
</para>
</sect3>
<sect3 id="message-protocol-names-member">
<sect4 id="message-protocol-types-method-apis">
<title>Mapping method calls to native APIs</title>
<para>
- APIs for D-BUS may map method calls to a method call in a specific
+ APIs for D-Bus may map method calls to a method call in a specific
programming language, such as C++, or may map a method call written
- in an IDL to a D-BUS message.
+ in an IDL to a D-Bus message.
</para>
<para>
In APIs of this nature, arguments to a method are often termed "in"
(which implies sent in the <literal>METHOD_CALL</literal>), or "out" (which implies
returned in the <literal>METHOD_RETURN</literal>). Some APIs such as CORBA also have
"inout" arguments, which are both sent and received, i.e. the caller
- passes in a value which is modified. Mapped to D-BUS, an "inout"
+ passes in a value which is modified. Mapped to D-Bus, an "inout"
argument is equivalent to an "in" argument, followed by an "out"
argument. You can't pass things "by reference" over the wire, so
"inout" is purely an illusion of the in-process API.
exceptions.
</para>
<para>
- In converting from native APIs to D-BUS, it is perhaps nice to
- map D-BUS naming conventions ("FooBar") to native conventions
+ In converting from native APIs to D-Bus, it is perhaps nice to
+ map D-Bus naming conventions ("FooBar") to native conventions
such as "fooBar" or "foo_bar" automatically. This is OK
as long as you can say that the native API is one that
- was specifically written for D-BUS. It makes the most sense
+ was specifically written for D-Bus. It makes the most sense
when writing object implementations that will be exported
- over the bus. Object proxies used to invoke remote D-BUS
- objects probably need the ability to call any D-BUS method,
+ over the bus. Object proxies used to invoke remote D-Bus
+ objects probably need the ability to call any D-Bus method,
and thus a magic name mapping like this could be a problem.
</para>
<para>
A signal emission is simply a single message of type <literal>SIGNAL</literal>.
It must have three header fields: <literal>PATH</literal> giving the object
the signal was emitted from, plus <literal>INTERFACE</literal> and <literal>MEMBER</literal> giving
- the fully-qualified name of the signal.
+ the fully-qualified name of the signal. The <literal>INTERFACE</literal> header is required
+ for signals, though it is optional for method calls.
</para>
</sect3>
<title>Invalid Protocol and Spec Extensions</title>
<para>
- For security reasons, the D-BUS protocol should be strictly parsed and
+ For security reasons, the D-Bus protocol should be strictly parsed and
validated, with the exception of defined extension points. Any invalid
protocol or spec violations should result in immediately dropping the
connection without notice to the other end. Exceptions should be
carefully considered, e.g. an exception may be warranted for a
- well-understood idiosyncracy of a widely-deployed implementation. In
+ well-understood idiosyncrasy of a widely-deployed implementation. In
cases where the other end of a connection is 100% trusted and known to
be friendly, skipping validation for performance reasons could also make
sense in certain cases.
</para>
<para>
- The following extension points are built in to D-BUS on purpose and must
+ The following extension points are built in to D-Bus on purpose and must
not be treated as invalid protocol. The extension points are intended
for use by future versions of this spec, they are not intended for third
- parties. At the moment, the only way a third party could extend D-BUS
+ parties. At the moment, the only way a third party could extend D-Bus
without breaking interoperability would be to introduce a way to negotiate new
feature support as part of the auth protocol, using EXTENSION_-prefixed
commands. There is not yet a standard way to negotiate features.
<listitem><para>BEGIN</para></listitem>
<listitem><para>DATA <data in hex encoding></para></listitem>
<listitem><para>ERROR [human-readable error explanation]</para></listitem>
+ <listitem><para>NEGOTIATE_UNIX_FD</para></listitem>
</itemizedlist>
From server to client are as follows:
<itemizedlist>
<listitem><para>REJECTED <space-separated list of mechanism names></para></listitem>
- <listitem><para>OK</para></listitem>
+ <listitem><para>OK <GUID in hex></para></listitem>
<listitem><para>DATA <data in hex encoding></para></listitem>
<listitem><para>ERROR</para></listitem>
+ <listitem><para>AGREE_UNIX_FD</para></listitem>
</itemizedlist>
</para>
<para>
an OK command must be sent to the client.
</para>
<para>
- The first octet received by the client after the \r\n of the OK
- command must be the first octet of the authenticated/encrypted
- stream of D-BUS messages.
- </para>
- <para>
The first octet received by the server after the \r\n of the BEGIN
command from the client must be the first octet of the
- authenticated/encrypted stream of D-BUS messages.
+ authenticated/encrypted stream of D-Bus messages.
+ </para>
+ <para>
+ If BEGIN is received by the server, the first octet received
+ by the client after the \r\n of the OK command must be the
+ first octet of the authenticated/encrypted stream of D-Bus
+ messages.
</para>
</sect2>
<sect2 id="auth-command-cancel">
<para>
The first octet received by the server after the \r\n of the BEGIN
command from the client must be the first octet of the
- authenticated/encrypted stream of D-BUS messages.
+ authenticated/encrypted stream of D-Bus messages.
</para>
</sect2>
<sect2 id="auth-command-rejected">
<sect2 id="auth-command-ok">
<title>OK Command</title>
<para>
- The OK command indicates that the client has been authenticated,
- and that further communication will be a stream of D-BUS messages
- (optionally encrypted, as negotiated) rather than this protocol.
+ The OK command indicates that the client has been
+ authenticated. The client may now proceed with negotiating
+ Unix file descriptor passing. To do that it shall send
+ NEGOTIATE_UNIX_FD to the server.
</para>
<para>
- The first octet received by the client after the \r\n of the OK
- command must be the first octet of the authenticated/encrypted
- stream of D-BUS messages.
+ Otherwise, the client must respond to the OK command by
+ sending a BEGIN command, followed by its stream of messages,
+ or by disconnecting. The server must not accept additional
+ commands using this protocol after the BEGIN command has been
+ received. Further communication will be a stream of D-Bus
+ messages (optionally encrypted, as negotiated) rather than
+ this protocol.
</para>
<para>
- The client must respond to the OK command by sending a BEGIN
- command, followed by its stream of messages, or by disconnecting.
- The server must not accept additional commands using this protocol
- after the OK command has been sent.
+ If a client sends BEGIN the first octet received by the client
+ after the \r\n of the OK command must be the first octet of
+ the authenticated/encrypted stream of D-Bus messages.
+ </para>
+ <para>
+ The OK command has one argument, which is the GUID of the server.
+ See <xref linkend="addresses"/> for more on server GUIDs.
</para>
</sect2>
<sect2 id="auth-command-error">
if only canceling/rejecting the authentication.
</para>
<para>
- If the D-BUS protocol changes incompatibly at some future time,
+ If the D-Bus protocol changes incompatibly at some future time,
applications implementing the new protocol would probably be able to
check for support of the new protocol by sending a new command and
receiving an ERROR from applications that don't understand it. Thus the
ERROR feature of the auth protocol is an escape hatch that lets us
- negotiate extensions or changes to the D-BUS protocol in the future.
+ negotiate extensions or changes to the D-Bus protocol in the future.
+ </para>
+ </sect2>
+ <sect2 id="auth-command-negotiate-unix-fd">
+ <title>NEGOTIATE_UNIX_FD Command</title>
+ <para>
+ The NEGOTIATE_UNIX_FD command indicates that the client
+ supports Unix file descriptor passing. This command may only
+ be sent after the connection is authenticated, i.e. after OK
+ was received by the client. This command may only be sent on
+ transports that support Unix file descriptor passing.
+ </para>
+ <para>
+ On receiving NEGOTIATE_UNIX_FD the server must respond with
+ either AGREE_UNIX_FD or ERROR. It shall respond the former if
+ the transport chosen supports Unix file descriptor passing and
+ the server supports this feature. It shall respond the latter
+ if the transport does not support Unix file descriptor
+ passing, the server does not support this feature, or the
+ server decides not to enable file descriptor passing due to
+ security or other reasons.
+ </para>
+ </sect2>
+ <sect2 id="auth-command-agree-unix-fd">
+ <title>AGREE_UNIX_FD Command</title>
+ <para>
+ The AGREE_UNIX_FD command indicates that the server supports
+ Unix file descriptor passing. This command may only be sent
+ after the connection is authenticated, and the client sent
+ NEGOTIATE_UNIX_FD to enable Unix file descriptor passing. This
+ command may only be sent on transports that support Unix file
+ descriptor passing.
+ </para>
+ <para>
+ On receiving AGREE_UNIX_FD the client must respond with BEGIN,
+ followed by its stream of messages, or by disconnecting. The
+ server must not accept additional commands using this protocol
+ after the BEGIN command has been received. Further
+ communication will be a stream of D-Bus messages (optionally
+ encrypted, as negotiated) rather than this protocol.
+ </para>
+ </sect2>
+ <sect2 id="auth-command-future">
+ <title>Future Extensions</title>
+ <para>
+ Future extensions to the authentication and negotiation
+ protocol are possible. For that new commands may be
+ introduced. If a client or server receives an unknown command
+ it shall respond with ERROR and not consider this fatal. New
+ commands may be introduced both before, and after
+ authentication, i.e. both before and after the OK command.
</para>
</sect2>
<sect2 id="auth-examples">
(MAGIC_COOKIE is a made up mechanism)
C: AUTH MAGIC_COOKIE 3138363935333137393635383634
- S: OK
+ S: OK 1234deadbeef
C: BEGIN
</programlisting>
</figure>
C: AUTH SKEY 7ab83f32ee
S: DATA 8799cabb2ea93e
C: DATA 8ac876e8f68ee9809bfa876e6f9876g8fa8e76e98f
- S: OK
+ S: OK 1234deadbeef
C: BEGIN
</programlisting>
</figure>
C: FOOBAR
S: ERROR
C: AUTH MAGIC_COOKIE 3736343435313230333039
- S: OK
+ S: OK 1234deadbeef
C: BEGIN
</programlisting>
</figure>
C: AUTH SKEY 7ab83f32ee
S: DATA 8799cabb2ea93e
C: DATA 8ac876e8f68ee9809bfa876e6f9876g8fa8e76e98f
- S: OK
+ S: OK 1234deadbeef
C: BEGIN
</programlisting>
</figure>
C: AUTH SKEY 7ab83f32ee
S: DATA 8799cabb2ea93e
C: DATA 8ac876e8f68ee9809bfa876e6f9876g8fa8e76e98f
- S: OK
+ S: OK 1234deadbeef
C: BEGIN
</programlisting>
</figure>
C: AUTH SKEY 7ab83f32ee
S: DATA 8799cabb2ea93e
C: DATA 8ac876e8f68ee9809bfa876e6f9876g8fa8e76e98f
- S: OK
+ S: OK 1234deadbeef
+ C: BEGIN
+ </programlisting>
+ </figure>
+ <figure>
+ <title>Example of successful magic cookie authentication with successful negotiation of Unix FD passing</title>
+ <programlisting>
+ (MAGIC_COOKIE is a made up mechanism)
+
+ C: AUTH MAGIC_COOKIE 3138363935333137393635383634
+ S: OK 1234deadbeef
+ C: NEGOTIATE_UNIX_FD
+ S: AGREE_UNIX_FD
+ C: BEGIN
+ </programlisting>
+ </figure>
+ <figure>
+ <title>Example of successful magic cookie authentication with unsuccessful negotiation of Unix FD passing</title>
+ <programlisting>
+ (MAGIC_COOKIE is a made up mechanism)
+
+ C: AUTH MAGIC_COOKIE 3138363935333137393635383634
+ S: OK 1234deadbeef
+ C: NEGOTIATE_UNIX_FD
+ S: ERROR
C: BEGIN
</programlisting>
</figure>
<title>Authentication mechanisms</title>
<para>
This section describes some new authentication mechanisms.
- D-BUS also allows any standard SASL mechanism of course.
+ D-Bus also allows any standard SASL mechanism of course.
</para>
<sect3 id="auth-mechanisms-sha">
<title>DBUS_COOKIE_SHA1</title>
directory.
</para>
<para>
+ Throughout this description, "hex encoding" must output the digits
+ from a to f in lower-case; the digits A to F must not be used
+ in the DBUS_COOKIE_SHA1 mechanism.
+ </para>
+ <para>
Authentication proceeds as follows:
<itemizedlist>
<listitem>
<para>
The client sends the username it would like to authenticate
- as.
+ as, hex-encoded.
</para>
</listitem>
<listitem>
The server sends the name of its "cookie context" (see below); a
space character; the integer ID of the secret cookie the client
must demonstrate knowledge of; a space character; then a
- hex-encoded randomly-generated challenge string.
+ randomly-generated challenge string, all of this hex-encoded into
+ one, single string.
</para>
</listitem>
<listitem>
<para>
- The client locates the cookie, and generates its own hex-encoded
- randomly-generated challenge string. The client then
- concatentates the server's hex-encoded challenge, a ":"
- character, its own hex-encoded challenge, another ":" character,
- and the hex-encoded cookie. It computes the SHA-1 hash of this
- composite string. It sends back to the server the client's
- hex-encoded challenge string, a space character, and the SHA-1
- hash.
+ The client locates the cookie and generates its own
+ randomly-generated challenge string. The client then concatenates
+ the server's decoded challenge, a ":" character, its own challenge,
+ another ":" character, and the cookie. It computes the SHA-1 hash
+ of this composite string as a hex digest. It concatenates the
+ client's challenge string, a space character, and the SHA-1 hex
+ digest, hex-encodes the result and sends it back to the server.
</para>
</listitem>
<listitem>
The set of optionally-escaped bytes is intended to preserve address
readability and convenience.
</para>
+
+ <para>
+ A server may specify a key-value pair with the key <literal>guid</literal>
+ and the value a hex-encoded 16-byte sequence. <xref linkend="uuids"/>
+ describes the format of the <literal>guid</literal> field. If present,
+ this UUID may be used to distinguish one server address from another. A
+ server should use a different UUID for each address it listens on. For
+ example, if a message bus daemon offers both UNIX domain socket and TCP
+ connections, but treats clients the same regardless of how they connect,
+ those two connections are equivalent post-connection but should have
+ distinct UUIDs to distinguish the kinds of connection.
+ </para>
+
+ <para>
+ The intent of the address UUID feature is to allow a client to avoid
+ opening multiple identical connections to the same server, by allowing the
+ client to check whether an address corresponds to an already-existing
+ connection. Comparing two addresses is insufficient, because addresses
+ can be recycled by distinct servers, and equivalent addresses may look
+ different if simply compared as strings (for example, the host in a TCP
+ address can be given as an IP address or as a hostname).
+ </para>
+
+ <para>
+ Note that the address key is <literal>guid</literal> even though the
+ rest of the API and documentation says "UUID," for historical reasons.
+ </para>
+
<para>
[FIXME clarify if attempting to connect to each is a requirement
or just a suggestion]
the next one specified, and so forth. For example
<programlisting>unix:path=/tmp/dbus-test;unix:path=/tmp/dbus-test2</programlisting>
</para>
+
+ </sect1>
+
+ <sect1 id="transports">
+ <title>Transports</title>
<para>
[FIXME we need to specify in detail each transport and its possible arguments]
+
Current transports include: unix domain sockets (including
abstract namespace on linux), TCP/IP, and a debug/testing transport using
in-process pipes. Future possible transports include one that
tunnels over X11 protocol.
</para>
+
+ <sect2 id="transports-unix-domain-sockets">
+ <title>Unix Domain Sockets</title>
+ <para>
+ Unix domain sockets can be either paths in the file system or on Linux
+ kernels, they can be abstract which are similar to paths but
+ do not show up in the file system.
+ </para>
+
+ <para>
+ When a socket is opened by the D-Bus library it truncates the path
+ name right before the first trailing Nul byte. This is true for both
+ normal paths and abstract paths. Note that this is a departure from
+ previous versions of D-Bus that would create sockets with a fixed
+ length path name. Names which were shorter than the fixed length
+ would be padded by Nul bytes.
+ </para>
+ <para>
+ Unix domain sockets are not available on windows.
+ </para>
+ <sect3 id="transports-unix-domain-sockets-addresses">
+ <title>Server Address Format</title>
+ <para>
+ Unix domain socket addresses are identified by the "unix:" prefix
+ and support the following key/value pairs:
+ </para>
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Values</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>path</entry>
+ <entry>(path)</entry>
+ <entry>path of the unix domain socket. If set, the "tmpdir" and "abstract" key must not be set.</entry>
+ </row>
+ <row>
+ <entry>tmpdir</entry>
+ <entry>(path)</entry>
+ <entry>temporary directory in which a socket file with a random file name starting with 'dbus-' will be created by the server. This key can only be used in server addresses, not in client addresses. If set, the "path" and "abstract" key must not be set.</entry>
+ </row>
+ <row>
+ <entry>abstract</entry>
+ <entry>(string)</entry>
+ <entry>unique string (path) in the abstract namespace. If set, the "path" or "tempdir" key must not be set.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </sect3>
+ </sect2>
+ <sect2 id="transports-tcp-sockets">
+ <title>TCP Sockets</title>
+ <para>
+ The tcp transport provides TCP/IP based connections between clients
+ located on the same or different hosts.
+ </para>
+ <para>
+ Using tcp transport without any additional secure authentification mechanismus
+ over a network is unsecure.
+ </para>
+ <para>
+ Windows notes: Because of the tcp stack on windows does not provide sending
+ credentials over a tcp connection, the EXTERNAL authentification
+ mechanismus does not work.
+ </para>
+ <sect3 id="transports-tcp-sockets-addresses">
+ <title>Server Address Format</title>
+ <para>
+ TCP/IP socket addresses are identified by the "tcp:" prefix
+ and support the following key/value pairs:
+ </para>
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Values</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>host</entry>
+ <entry>(string)</entry>
+ <entry>dns name or ip address</entry>
+ </row>
+ <row>
+ <entry>port</entry>
+ <entry>(number)</entry>
+ <entry>The tcp port the server will open. A zero value let the server
+ choose a free port provided from the underlaying operating system.
+ libdbus is able to retrieve the real used port from the server.
+ </entry>
+ </row>
+ <row>
+ <entry>family</entry>
+ <entry>(string)</entry>
+ <entry>If set, provide the type of socket family either "ipv4" or "ipv6". If unset, the family is unspecified.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </sect3>
+ </sect2>
+ <sect2 id="transports-nonce-tcp-sockets">
+ <title>Nonce-secured TCP Sockets</title>
+ <para>
+ The nonce-tcp transport provides a secured TCP transport, using a
+ simple authentication mechanism to ensure that only clients with read
+ access to a certain location in the filesystem can connect to the server.
+ The server writes a secret, the nonce, to a file and an incoming client
+ connection is only accepted if the client sends the nonce right after
+ the connect. The nonce mechanism requires no setup and is orthogonal to
+ the higher-level authentication mechanisms described in the
+ Authentication section.
+ </para>
+
+ <para>
+ On start, the server generates a random 16 byte nonce and writes it
+ to a file in the user's temporary directory. The nonce file location
+ is published as part of the server's D-Bus address using the
+ "noncefile" key-value pair.
+
+ After an accept, the server reads 16 bytes from the socket. If the
+ read bytes do not match the nonce stored in the nonce file, the
+ server MUST immediately drop the connection.
+ If the nonce match the received byte sequence, the client is accepted
+ and the transport behaves like an unsecured tcp transport.
+ </para>
+ <para>
+ After a successful connect to the server socket, the client MUST read
+ the nonce from the file published by the server via the noncefile=
+ key-value pair and send it over the socket. After that, the
+ transport behaves like an unsecured tcp transport.
+ </para>
+ <sect3 id="transports-nonce-tcp-sockets-addresses">
+ <title>Server Address Format</title>
+ <para>
+ Nonce TCP/IP socket addresses uses the "nonce-tcp:" prefix
+ and support the following key/value pairs:
+ </para>
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Values</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>host</entry>
+ <entry>(string)</entry>
+ <entry>dns name or ip address</entry>
+ </row>
+ <row>
+ <entry>port</entry>
+ <entry>(number)</entry>
+ <entry>The tcp port the server will open. A zero value let the server
+ choose a free port provided from the underlaying operating system.
+ libdbus is able to retrieve the real used port from the server.
+ </entry>
+ </row>
+ <row>
+ <entry>family</entry>
+ <entry>(string)</entry>
+ <entry>If set, provide the type of socket family either "ipv4" or "ipv6". If unset, the family is unspecified.</entry>
+ </row>
+ <row>
+ <entry>noncefile</entry>
+ <entry>(path)</entry>
+ <entry>file location containing the secret</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </sect3>
+ </sect2>
+
</sect1>
<sect1 id="naming-conventions">
<title>Naming Conventions</title>
<para>
- D-BUS namespaces are all lowercase and correspond to reversed domain
+ D-Bus namespaces are all lowercase and correspond to reversed domain
names, as with Java. e.g. "org.freedesktop"
</para>
<para>
hyphens.
</para>
</sect1>
+
+ <sect1 id="uuids">
+ <title>UUIDs</title>
+ <para>
+ A working D-Bus implementation uses universally-unique IDs in two places.
+ First, each server address has a UUID identifying the address,
+ as described in <xref linkend="addresses"/>. Second, each operating
+ system kernel instance running a D-Bus client or server has a UUID
+ identifying that kernel, retrieved by invoking the method
+ org.freedesktop.DBus.Peer.GetMachineId() (see <xref
+ linkend="standard-interfaces-peer"/>).
+ </para>
+ <para>
+ The term "UUID" in this document is intended literally, i.e. an
+ identifier that is universally unique. It is not intended to refer to
+ RFC4122, and in fact the D-Bus UUID is not compatible with that RFC.
+ </para>
+ <para>
+ The UUID must contain 128 bits of data and be hex-encoded. The
+ hex-encoded string may not contain hyphens or other non-hex-digit
+ characters, and it must be exactly 32 characters long. To generate a
+ UUID, the current reference implementation concatenates 96 bits of random
+ data followed by the 32-bit time in seconds since the UNIX epoch (in big
+ endian byte order).
+ </para>
+ <para>
+ It would also be acceptable and probably better to simply generate 128
+ bits of random data, as long as the random number generator is of high
+ quality. The timestamp could conceivably help if the random bits are not
+ very random. With a quality random number generator, collisions are
+ extremely unlikely even with only 96 bits, so it's somewhat academic.
+ </para>
+ <para>
+ Implementations should, however, stick to random data for the first 96 bits
+ of the UUID.
+ </para>
+ </sect1>
<sect1 id="standard-interfaces">
<title>Standard Interfaces</title>
<para>
See <xref linkend="message-protocol-types-notation"/> for details on
the notation used in this section. There are some standard interfaces
- that may be useful across various D-BUS applications.
+ that may be useful across various D-Bus applications.
</para>
<sect2 id="standard-interfaces-peer">
- <title><literal>org.freedesktop.Peer</literal></title>
+ <title><literal>org.freedesktop.DBus.Peer</literal></title>
<para>
- The <literal>org.freedesktop.Peer</literal> interface
- has one method:
+ The <literal>org.freedesktop.DBus.Peer</literal> interface
+ has two methods:
<programlisting>
- org.freedesktop.Peer.Ping ()
+ org.freedesktop.DBus.Peer.Ping ()
+ org.freedesktop.DBus.Peer.GetMachineId (out STRING machine_uuid)
</programlisting>
</para>
<para>
On receipt of the <literal>METHOD_CALL</literal> message
- <literal>org.freedesktop.Peer.Ping</literal>, an application should do
+ <literal>org.freedesktop.DBus.Peer.Ping</literal>, an application should do
nothing other than reply with a <literal>METHOD_RETURN</literal> as
usual. It does not matter which object path a ping is sent to. The
- reference implementation should simply handle this method on behalf of
- all objects, though it doesn't yet. (The point is, you're really pinging
- the peer process, not a specific object.)
+ reference implementation handles this method automatically.
+ </para>
+ <para>
+ On receipt of the <literal>METHOD_CALL</literal> message
+ <literal>org.freedesktop.DBus.Peer.GetMachineId</literal>, an application should
+ reply with a <literal>METHOD_RETURN</literal> containing a hex-encoded
+ UUID representing the identity of the machine the process is running on.
+ This UUID must be the same for all processes on a single system at least
+ until that system next reboots. It should be the same across reboots
+ if possible, but this is not always possible to implement and is not
+ guaranteed.
+ It does not matter which object path a GetMachineId is sent to. The
+ reference implementation handles this method automatically.
+ </para>
+ <para>
+ The UUID is intended to be per-instance-of-the-operating-system, so may represent
+ a virtual machine running on a hypervisor, rather than a physical machine.
+ Basically if two processes see the same UUID, they should also see the same
+ shared memory, UNIX domain sockets, process IDs, and other features that require
+ a running OS kernel in common between the processes.
+ </para>
+ <para>
+ The UUID is often used where other programs might use a hostname. Hostnames
+ can change without rebooting, however, or just be "localhost" - so the UUID
+ is more robust.
+ </para>
+ <para>
+ <xref linkend="uuids"/> explains the format of the UUID.
</para>
</sect2>
<sect2 id="standard-interfaces-introspectable">
- <title><literal>org.freedesktop.Introspectable</literal></title>
+ <title><literal>org.freedesktop.DBus.Introspectable</literal></title>
<para>
This interface has one method:
<programlisting>
- org.freedesktop.Introspectable.Introspect (out STRING xml_data)
+ org.freedesktop.DBus.Introspectable.Introspect (out STRING xml_data)
</programlisting>
</para>
<para>
</para>
</sect2>
<sect2 id="standard-interfaces-properties">
- <title><literal>org.freedesktop.Properties</literal></title>
+ <title><literal>org.freedesktop.DBus.Properties</literal></title>
<para>
Many native APIs will have a concept of object <firstterm>properties</firstterm>
or <firstterm>attributes</firstterm>. These can be exposed via the
- <literal>org.freedesktop.Properties</literal> interface.
+ <literal>org.freedesktop.DBus.Properties</literal> interface.
</para>
<para>
<programlisting>
- org.freedesktop.Properties.Get (in STRING interface_name,
- in STRING property_name,
- out VARIANT value);
- org.freedesktop.Properties.Set (in STRING interface_name,
- in STRING property_name,
- in VARIANT value);
+ org.freedesktop.DBus.Properties.Get (in STRING interface_name,
+ in STRING property_name,
+ out VARIANT value);
+ org.freedesktop.DBus.Properties.Set (in STRING interface_name,
+ in STRING property_name,
+ in VARIANT value);
+ org.freedesktop.DBus.Properties.GetAll (in STRING interface_name,
+ out DICT<STRING,VARIANT> props);
</programlisting>
</para>
<para>
The available properties and whether they are writable can be determined
- by calling <literal>org.freedesktop.Introspectable.Introspect</literal>,
+ by calling <literal>org.freedesktop.DBus.Introspectable.Introspect</literal>,
see <xref linkend="standard-interfaces-introspectable"/>.
</para>
<para>
deterministic rule, or returning an error, are the reasonable
possibilities).
</para>
+ <para>
+ If one or more properties change on an object, the
+ <literal>org.freedesktop.DBus.Properties.PropertiesChanged</literal>
+ signal may be emitted (this signal was added in 0.14):
+ </para>
+ <para>
+ <programlisting>
+ org.freedesktop.DBus.Properties.PropertiesChanged (STRING interface_name,
+ DICT<STRING,VARIANT> changed_properties,
+ ARRAY<STRING> invalidated_properties);
+ </programlisting>
+ </para>
+ <para>
+ where <literal>changed_properties</literal> is a dictionary
+ containing the changed properties with the new values and
+ <literal>invalidated_properties</literal> is an array of
+ properties that changed but the value is not conveyed.
+ </para>
+ <para>
+ Whether the <literal>PropertiesChanged</literal> signal is
+ supported can be determined by calling
+ <literal>org.freedesktop.DBus.Introspectable.Introspect</literal>. Note
+ that the signal may be supported for an object but it may
+ differ how whether and how it is used on a per-property basis
+ (for e.g. performance or security reasons). Each property (or
+ the parent interface) must be annotated with the
+ <literal>org.freedesktop.DBus.Property.EmitsChangedSignal</literal>
+ annotation to convey this (usually the default value
+ <literal>true</literal> is sufficient meaning that the
+ annotation does not need to be used). See <xref
+ linkend="introspection-format"/> for details on this
+ annotation.
+ </para>
</sect2>
</sect1>
<node name="/org/freedesktop/sample_object">
<interface name="org.freedesktop.SampleInterface">
<method name="Frobate">
- <arg name="foo" type="int32" direction="in"/>
- <arg name="bar" type="string" direction="out"/>
+ <arg name="foo" type="i" direction="in"/>
+ <arg name="bar" type="s" direction="out"/>
+ <arg name="baz" type="a{us}" direction="out"/>
+ <annotation name="org.freedesktop.DBus.Deprecated" value="true"/>
+ </method>
+ <method name="Bazify">
+ <arg name="bar" type="(iiu)" direction="in"/>
+ <arg name="bar" type="v" direction="out"/>
+ </method>
+ <method name="Mogrify">
+ <arg name="bar" type="(iiav)" direction="in"/>
</method>
<signal name="Changed">
- <arg name="new_value" type="boolean"/>
+ <arg name="new_value" type="b"/>
</signal>
- <property name="Bar" type="byte" access="readwrite"/>
+ <property name="Bar" type="y" access="readwrite"/>
</interface>
<node name="child_of_sample_object"/>
<node name="another_child_of_sample_object"/>
</listitem>
<listitem>
<para>
- The current type="uint32" stuff is totally broken,
- instead we have to do full signatures.
- However, then this format will suck for human readability.
- So, some thinking to do here.
- </para>
- </listitem>
- <listitem>
- <para>
Multiple interfaces can of course be listed for
one <node>.
</para>
</listitem>
<listitem>
<para>
- The method, interface, property, and signal elements may have
- an attribute deprecated="yes|no". If the attribute is not
- present, the default value for an interface is "no", and
- the default value for methods, properties, and signals is
- the deprecation status of the interface.
- </para>
- </listitem>
- <listitem>
- <para>
The "name" attribute on arguments is optional.
</para>
</listitem>
</itemizedlist>
</para>
-
+ <para>
+ Method, interface, property, and signal elements may have
+ "annotations", which are generic key/value pairs of metadata.
+ They are similar conceptually to Java's annotations and C# attributes.
+ Well-known annotations:
+ </para>
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Values (separated by ,)</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>org.freedesktop.DBus.Deprecated</entry>
+ <entry>true,false</entry>
+ <entry>Whether or not the entity is deprecated; defaults to false</entry>
+ </row>
+ <row>
+ <entry>org.freedesktop.DBus.GLib.CSymbol</entry>
+ <entry>(string)</entry>
+ <entry>The C symbol; may be used for methods and interfaces</entry>
+ </row>
+ <row>
+ <entry>org.freedesktop.DBus.Method.NoReply</entry>
+ <entry>true,false</entry>
+ <entry>If set, don't expect a reply to the method call; defaults to false.</entry>
+ </row>
+ <row>
+ <entry>org.freedesktop.DBus.Property.EmitsChangedSignal</entry>
+ <entry>true,invalidates,false</entry>
+ <entry>
+ <para>
+ If set to <literal>false</literal>, the
+ <literal>org.freedesktop.DBus.Properties.PropertiesChanged</literal>
+ signal, see <xref
+ linkend="standard-interfaces-properties"/> is not
+ guaranteed to be emitted if the property changes.
+ </para>
+ <para>
+ If set to <literal>invalidates</literal> the signal
+ is emitted but the value is not included in the
+ signal.
+ </para>
+ <para>
+ If set to <literal>true</literal> the signal is
+ emitted with the value included.
+ </para>
+ <para>
+ The value for the annotation defaults to
+ <literal>true</literal> if the enclosing interface
+ element does not specify the annotation. Otherwise it
+ defaults to the value specified in the enclosing
+ interface element.
+ </para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
</sect1>
-
<sect1 id="message-bus">
<title>Message Bus Specification</title>
<sect2 id="message-bus-overview">
<literal>DESTINATION</literal> field is absent, the call is taken to be
a standard one-to-one message and interpreted by the message bus
itself. For example, sending an
- <literal>org.freedesktop.Peer.Ping</literal> message with no
+ <literal>org.freedesktop.DBus.Peer.Ping</literal> message with no
<literal>DESTINATION</literal> will cause the message bus itself to
reply to the ping immediately; the message bus will not make this
message visible to other applications.
</para>
<para>
- Continuing the <literal>org.freedesktop.Peer.Ping</literal> example, if
+ Continuing the <literal>org.freedesktop.DBus.Peer.Ping</literal> example, if
the ping message were sent with a <literal>DESTINATION</literal> name of
<literal>com.yoyodyne.Screensaver</literal>, then the ping would be
forwarded, and the Yoyodyne Corporation screensaver application would be
A connection can request additional names to be associated with it using
the <literal>org.freedesktop.DBus.RequestName</literal> message. <xref
linkend="message-protocol-names-bus"/> describes the format of a valid
- name.
+ name. These names can be released again using the
+ <literal>org.freedesktop.DBus.ReleaseName</literal> message.
</para>
<sect3 id="bus-messages-request-name">
<para>
This method call should be sent to
<literal>org.freedesktop.DBus</literal> and asks the message bus to
- assign the given name to the method caller. The flags argument
- contains any of the following values logically ORed together:
+ assign the given name to the method caller. Each name maintains a
+ queue of possible owners, where the head of the queue is the primary
+ or current owner of the name. Each potential owner in the queue
+ maintains the DBUS_NAME_FLAG_ALLOW_REPLACEMENT and
+ DBUS_NAME_FLAG_DO_NOT_QUEUE settings from its latest RequestName
+ call. When RequestName is invoked the following occurs:
+ <itemizedlist>
+ <listitem>
+ <para>
+ If the method caller is currently the primary owner of the name,
+ the DBUS_NAME_FLAG_ALLOW_REPLACEMENT and DBUS_NAME_FLAG_DO_NOT_QUEUE
+ values are updated with the values from the new RequestName call,
+ and nothing further happens.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ If the current primary owner (head of the queue) has
+ DBUS_NAME_FLAG_ALLOW_REPLACEMENT set, and the RequestName
+ invocation has the DBUS_NAME_FLAG_REPLACE_EXISTING flag, then
+ the caller of RequestName replaces the current primary owner at
+ the head of the queue and the current primary owner moves to the
+ second position in the queue. If the caller of RequestName was
+ in the queue previously its flags are updated with the values from
+ the new RequestName in addition to moving it to the head of the queue.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ If replacement is not possible, and the method caller is
+ currently in the queue but not the primary owner, its flags are
+ updated with the values from the new RequestName call.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ If replacement is not possible, and the method caller is
+ currently not in the queue, the method caller is appended to the
+ queue.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ If any connection in the queue has DBUS_NAME_FLAG_DO_NOT_QUEUE
+ set and is not the primary owner, it is removed from the
+ queue. This can apply to the previous primary owner (if it
+ was replaced) or the method caller (if it updated the
+ DBUS_NAME_FLAG_DO_NOT_QUEUE flag while still stuck in the
+ queue, or if it was just added to the queue with that flag set).
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ Note that DBUS_NAME_FLAG_REPLACE_EXISTING results in "jumping the
+ queue," even if another application already in the queue had specified
+ DBUS_NAME_FLAG_REPLACE_EXISTING. This comes up if a primary owner
+ that does not allow replacement goes away, and the next primary owner
+ does allow replacement. In this case, queued items that specified
+ DBUS_NAME_FLAG_REPLACE_EXISTING <emphasis>do not</emphasis>
+ automatically replace the new primary owner. In other words,
+ DBUS_NAME_FLAG_REPLACE_EXISTING is not saved, it is only used at the
+ time RequestName is called. This is deliberate to avoid an infinite loop
+ anytime two applications are both DBUS_NAME_FLAG_ALLOW_REPLACEMENT
+ and DBUS_NAME_FLAG_REPLACE_EXISTING.
+ </para>
+ <para>
+ The flags argument contains any of the following values logically ORed
+ together:
<informaltable>
<tgroup cols="3">
</thead>
<tbody>
<row>
- <entry>DBUS_NAME_FLAG_PROHIBIT_REPLACEMENT</entry>
+ <entry>DBUS_NAME_FLAG_ALLOW_REPLACEMENT</entry>
<entry>0x1</entry>
<entry>
- If the application succeeds in becoming the owner of the specified name,
- then ownership of the name can't be transferred until the application
- disconnects. If this flag is not set, then any application trying to become
- the owner of the name will succeed and the previous owner will be
- sent a <literal>org.freedesktop.DBus.NameLost</literal> signal.
+
+ If an application A specifies this flag and succeeds in
+ becoming the owner of the name, and another application B
+ later calls RequestName with the
+ DBUS_NAME_FLAG_REPLACE_EXISTING flag, then application A
+ will lose ownership and receive a
+ <literal>org.freedesktop.DBus.NameLost</literal> signal, and
+ application B will become the new owner. If DBUS_NAME_FLAG_ALLOW_REPLACEMENT
+ is not specified by application A, or DBUS_NAME_FLAG_REPLACE_EXISTING
+ is not specified by application B, then application B will not replace
+ application A as the owner.
+
</entry>
</row>
<row>
<entry>DBUS_NAME_FLAG_REPLACE_EXISTING</entry>
<entry>0x2</entry>
<entry>
+
Try to replace the current owner if there is one. If this
flag is not set the application will only become the owner of
- the name if there is no current owner.
+ the name if there is no current owner. If this flag is set,
+ the application will replace the current owner if
+ the current owner specified DBUS_NAME_FLAG_ALLOW_REPLACEMENT.
+
+ </entry>
+ </row>
+ <row>
+ <entry>DBUS_NAME_FLAG_DO_NOT_QUEUE</entry>
+ <entry>0x4</entry>
+ <entry>
+
+ Without this flag, if an application requests a name that is
+ already owned, the application will be placed in a queue to
+ own the name when the current owner gives it up. If this
+ flag is given, the application will not be placed in the
+ queue, the request for the name will simply fail. This flag
+ also affects behavior when an application is replaced as
+ name owner; by default the application moves back into the
+ waiting queue, unless this flag was provided when the application
+ became the name owner.
+
</entry>
</row>
</tbody>
<entry>1</entry> <entry>The caller is now the primary owner of
the name, replacing any previous owner. Either the name had no
owner before, or the caller specified
- DBUS_NAME_FLAG_REPLACE_EXISTING and the current owner did not
- specify DBUS_NAME_FLAG_PROHIBIT_REPLACEMENT.</entry>
+ DBUS_NAME_FLAG_REPLACE_EXISTING and the current owner specified
+ DBUS_NAME_FLAG_ALLOW_REPLACEMENT.</entry>
</row>
<row>
<entry>DBUS_REQUEST_NAME_REPLY_IN_QUEUE</entry>
<entry>2</entry>
- <entry>The name already had an owner, DBUS_NAME_FLAG_REPLACE_EXISTING was not specified, and the current owner specified DBUS_NAME_FLAG_PROHIBIT_REPLACEMENT.</entry>
+
+ <entry>The name already had an owner,
+ DBUS_NAME_FLAG_DO_NOT_QUEUE was not specified, and either
+ the current owner did not specify
+ DBUS_NAME_FLAG_ALLOW_REPLACEMENT or the requesting
+ application did not specify DBUS_NAME_FLAG_REPLACE_EXISTING.
+ </entry>
</row>
<row>
- <entry>DBUS_REQUEST_NAME_REPLY_EXISTS</entry>
- <entry>3</entry>
- <entry>The name already has an owner, and DBUS_NAME_FLAG_REPLACE_EXISTING was not specified.</entry>
+ <entry>DBUS_REQUEST_NAME_REPLY_EXISTS</entry> <entry>3</entry>
+ <entry>The name already has an owner,
+ DBUS_NAME_FLAG_DO_NOT_QUEUE was specified, and either
+ DBUS_NAME_FLAG_ALLOW_REPLACEMENT was not specified by the
+ current owner, or DBUS_NAME_FLAG_REPLACE_EXISTING was not
+ specified by the requesting application.</entry>
</row>
<row>
<entry>DBUS_REQUEST_NAME_REPLY_ALREADY_OWNER</entry>
</tgroup>
</informaltable>
</para>
- </sect3>
- </sect2>
+ </sect3>
- <sect2 id="message-bus-routing">
- <title>Message Bus Message Routing</title>
- <para>
- FIXME
- </para>
- </sect2>
- <sect2 id="message-bus-starting-services">
- <title>Message Bus Starting Services</title>
- <para>
- The message bus can start applications on behalf of other applications.
- In CORBA terms, this would be called <firstterm>activation</firstterm>.
- An application that can be started in this way is called a
- <firstterm>service</firstterm>.
- </para>
- <para>
- With D-BUS, starting a service is normally done by name. That is,
- applications ask the message bus to start some program that will own a
- well-known name, such as <literal>org.freedesktop.TextEditor</literal>.
- This implies a contract documented along with the name
- <literal>org.freedesktop.TextEditor</literal> for which objects
- the owner of that name will provide, and what interfaces those
- objects will have.
- </para>
- <para>
- To find an executable corresponding to a particular name, the bus daemon
- looks for <firstterm>service description files</firstterm>. Service
- description files define a mapping from names to executables. Different
- kinds of message bus will look for these files in different places, see
- <xref linkend="message-bus-types"/>.
- </para>
- <para>
- [FIXME the file format should be much better specified than "similar to
- .desktop entries" esp. since desktop entries are already
- badly-specified. ;-)] Service description files have the ".service" file
- extension. The message bus will only load service description files
- ending with .service; all other files will be ignored. The file format
- is similar to that of <ulink
- url="http://www.freedesktop.org/standards/desktop-entry-spec/desktop-entry-spec.html">desktop
- entries</ulink>. All service description files must be in UTF-8
- encoding. To ensure that there will be no name collisions, service files
- must be namespaced using the same mechanism as messages and service
- names.
+ <sect3 id="bus-messages-release-name">
+ <title><literal>org.freedesktop.DBus.ReleaseName</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ UINT32 ReleaseName (in STRING name)
+ </programlisting>
+ Message arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>STRING</entry>
+ <entry>Name to release</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Reply arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>UINT32</entry>
+ <entry>Return value</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ <para>
+ This method call should be sent to
+ <literal>org.freedesktop.DBus</literal> and asks the message bus to
+ release the method caller's claim to the given name. If the caller is
+ the primary owner, a new primary owner will be selected from the
+ queue if any other owners are waiting. If the caller is waiting in
+ the queue for the name, the caller will removed from the queue and
+ will not be made an owner of the name if it later becomes available.
+ If there are no other owners in the queue for the name, it will be
+ removed from the bus entirely.
+
+ The return code can be one of the following values:
+
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Conventional Name</entry>
+ <entry>Value</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>DBUS_RELEASE_NAME_REPLY_RELEASED</entry>
+ <entry>1</entry> <entry>The caller has released his claim on
+ the given name. Either the caller was the primary owner of
+ the name, and the name is now unused or taken by somebody
+ waiting in the queue for the name, or the caller was waiting
+ in the queue for the name and has now been removed from the
+ queue.</entry>
+ </row>
+ <row>
+ <entry>DBUS_RELEASE_NAME_REPLY_NON_EXISTENT</entry>
+ <entry>2</entry>
+ <entry>The given name does not exist on this bus.</entry>
+ </row>
+ <row>
+ <entry>DBUS_RELEASE_NAME_REPLY_NOT_OWNER</entry>
+ <entry>3</entry>
+ <entry>The caller was not the primary owner of this name,
+ and was also not waiting in the queue to own this name.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </sect3>
+
+ <sect3 id="bus-messages-list-queued-owners">
+ <title><literal>org.freedesktop.DBus.ListQueuedOwners</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ ARRAY of STRING ListQueuedOwners (in STRING name)
+ </programlisting>
+ Message arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>STRING</entry>
+ <entry>The well-known bus name to query, such as
+ <literal>com.example.cappuccino</literal></entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Reply arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>ARRAY of STRING</entry>
+ <entry>The unique bus names of connections currently queued
+ for the name</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ <para>
+ This method call should be sent to
+ <literal>org.freedesktop.DBus</literal> and lists the connections
+ currently queued for a bus name (see
+ <xref linkend="term-queued-owner"/>).
+ </para>
+ </sect3>
+ </sect2>
+
+ <sect2 id="message-bus-routing">
+ <title>Message Bus Message Routing</title>
+ <para>
+ FIXME
+ </para>
+ <sect3 id="message-bus-routing-match-rules">
+ <title>Match Rules</title>
+ <para>
+ An important part of the message bus routing protocol is match
+ rules. Match rules describe what messages can be sent to a client
+ based on the contents of the message. When a message is routed
+ through the bus it is compared to clients' match rules. If any
+ of the rules match, the message is dispatched to the client.
+ If none of the rules match the message never leaves the bus. This
+ is an effective way to control traffic over the bus and to make sure
+ only relevant message need to be processed by the client.
+ </para>
+ <para>
+ Match rules are added using the AddMatch bus method
+ (see <xref linkend="bus-messages-add-match"/>). Rules are
+ specified as a string of comma separated key/value pairs.
+ Excluding a key from the rule indicates a wildcard match.
+ For instance excluding the the member from a match rule but
+ adding a sender would let all messages from that sender through.
+ An example of a complete rule would be
+ "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='Foo',path='/bar/foo',destination=':452345.34',arg2='bar'"
+ </para>
+ <para>
+ The following table describes the keys that can be used to create
+ a match rule:
+ The following table summarizes the D-Bus types.
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Key</entry>
+ <entry>Possible Values</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><literal>type</literal></entry>
+ <entry>'signal', 'method_call', 'method_return', 'error'</entry>
+ <entry>Match on the message type. An example of a type match is type='signal'</entry>
+ </row>
+ <row>
+ <entry><literal>sender</literal></entry>
+ <entry>A bus or unique name (see <xref linkend="term-bus-name"/>
+ and <xref linkend="term-unique-name"/> respectively)
+ </entry>
+ <entry>Match messages sent by a particular sender. An example of a sender match
+ is sender='org.freedesktop.Hal'</entry>
+ </row>
+ <row>
+ <entry><literal>interface</literal></entry>
+ <entry>An interface name (see <xref linkend="message-protocol-names-interface"/>)</entry>
+ <entry>Match messages sent over or to a particular interface. An example of an
+ interface match is interface='org.freedesktop.Hal.Manager'.
+ If a message omits the interface header, it must not match any rule
+ that specifies this key.</entry>
+ </row>
+ <row>
+ <entry><literal>member</literal></entry>
+ <entry>Any valid method or signal name</entry>
+ <entry>Matches messages which have the give method or signal name. An example of
+ a member match is member='NameOwnerChanged'</entry>
+ </row>
+ <row>
+ <entry><literal>path</literal></entry>
+ <entry>An object path (see <xref linkend="message-protocol-marshaling-object-path"/>)</entry>
+ <entry>Matches messages which are sent from or to the given object. An example of a
+ path match is path='/org/freedesktop/Hal/Manager'</entry>
+ </row>
+ <row>
+ <entry><literal>destination</literal></entry>
+ <entry>A unique name (see <xref linkend="term-unique-name"/>)</entry>
+ <entry>Matches messages which are being sent to the given unique name. An
+ example of a destination match is destination=':1.0'</entry>
+ </row>
+ <row>
+ <entry><literal>arg[0, 1, 2, 3, ...]</literal></entry>
+ <entry>Any string</entry>
+ <entry>Arg matches are special and are used for further restricting the
+ match based on the arguments in the body of a message. As of this time
+ only string arguments can be matched. An example of an argument match
+ would be arg3='Foo'. Only argument indexes from 0 to 63 should be
+ accepted.</entry>
+ </row>
+ <row>
+ <entry><literal>arg[0, 1, 2, 3, ...]path</literal></entry>
+ <entry>Any string</entry>
+ <entry>Argument path matches provide a specialised form of wildcard
+ matching for path-like namespaces. As with normal argument matches,
+ if the argument is exactly equal to the string given in the match
+ rule then the rule is satisfied. Additionally, there is also a
+ match when either the string given in the match rule or the
+ appropriate message argument ends with '/' and is a prefix of the
+ other. An example argument path match is arg0path='/aa/bb/'. This
+ would match messages with first arguments of '/', '/aa/',
+ '/aa/bb/', '/aa/bb/cc/' and '/aa/bb/cc'. It would not match
+ messages with first arguments of '/aa/b', '/aa' or even '/aa/bb'.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </sect3>
+ </sect2>
+ <sect2 id="message-bus-starting-services">
+ <title>Message Bus Starting Services</title>
+ <para>
+ The message bus can start applications on behalf of other applications.
+ In CORBA terms, this would be called <firstterm>activation</firstterm>.
+ An application that can be started in this way is called a
+ <firstterm>service</firstterm>.
+ </para>
+ <para>
+ With D-Bus, starting a service is normally done by name. That is,
+ applications ask the message bus to start some program that will own a
+ well-known name, such as <literal>org.freedesktop.TextEditor</literal>.
+ This implies a contract documented along with the name
+ <literal>org.freedesktop.TextEditor</literal> for which objects
+ the owner of that name will provide, and what interfaces those
+ objects will have.
+ </para>
+ <para>
+ To find an executable corresponding to a particular name, the bus daemon
+ looks for <firstterm>service description files</firstterm>. Service
+ description files define a mapping from names to executables. Different
+ kinds of message bus will look for these files in different places, see
+ <xref linkend="message-bus-types"/>.
+ </para>
+ <para>
+ [FIXME the file format should be much better specified than "similar to
+ .desktop entries" esp. since desktop entries are already
+ badly-specified. ;-)] Service description files have the ".service" file
+ extension. The message bus will only load service description files
+ ending with .service; all other files will be ignored. The file format
+ is similar to that of <ulink
+ url="http://www.freedesktop.org/standards/desktop-entry-spec/desktop-entry-spec.html">desktop
+ entries</ulink>. All service description files must be in UTF-8
+ encoding. To ensure that there will be no name collisions, service files
+ must be namespaced using the same mechanism as messages and service
+ names.
<figure>
<title>Example service description file</title>
<literal>unix:path=/var/run/dbus/system_bus_socket</literal>.
<footnote>
<para>
- The D-BUS reference implementation actually honors the
+ The D-Bus reference implementation actually honors the
<literal>$(localstatedir)</literal> configure option
for this address, on both client and server side.
</para>
Returns a list of all currently-owned names on the bus.
</para>
</sect3>
+ <sect3 id="bus-messages-list-activatable-names">
+ <title><literal>org.freedesktop.DBus.ListActivatableNames</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ ARRAY of STRING ListActivatableNames ()
+ </programlisting>
+ Reply arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>ARRAY of STRING</entry>
+ <entry>Array of strings where each string is a bus name</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ <para>
+ Returns a list of all names that can be activated on the bus.
+ </para>
+ </sect3>
<sect3 id="bus-messages-name-exists">
<title><literal>org.freedesktop.DBus.NameHasOwner</literal></title>
<para>
</sect3>
+ <sect3 id="bus-messages-update-activation-environment">
+ <title><literal>org.freedesktop.DBus.UpdateActivationEnvironment</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ UpdateActivationEnvironment (in ARRAY of DICT<STRING,STRING> environment)
+ </programlisting>
+ Message arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>ARRAY of DICT<STRING,STRING></entry>
+ <entry>Environment to add or update</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Normally, session bus activated services inherit the environment of the bus daemon. This method adds to or modifies that environment when activating services.
+ </para>
+ <para>
+ Some bus instances, such as the standard system bus, may disable access to this method for some or all callers.
+ </para>
+ <para>
+ Note, both the environment variable names and values must be valid UTF-8. There's no way to update the activation environment with data that is invalid UTF-8.
+ </para>
+
+ </sect3>
+
<sect3 id="bus-messages-get-name-owner">
<title><literal>org.freedesktop.DBus.GetNameOwner</literal></title>
<para>
</para>
</sect3>
+ <sect3 id="bus-messages-get-connection-unix-process-id">
+ <title><literal>org.freedesktop.DBus.GetConnectionUnixProcessID</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ UINT32 GetConnectionUnixProcessID (in STRING bus_name)
+ </programlisting>
+ Message arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>STRING</entry>
+ <entry>Unique or well-known bus name of the connection to
+ query, such as <literal>:12.34</literal> or
+ <literal>com.example.tea</literal></entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Reply arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>UINT32</entry>
+ <entry>Unix process id</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Returns the Unix process ID of the process connected to the server. If
+ unable to determine it (for instance, because the process is not on the
+ same machine as the bus daemon), an error is returned.
+ </para>
+ </sect3>
+
+ <sect3 id="bus-messages-add-match">
+ <title><literal>org.freedesktop.DBus.AddMatch</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ AddMatch (in STRING rule)
+ </programlisting>
+ Message arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>STRING</entry>
+ <entry>Match rule to add to the connection</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Adds a match rule to match messages going through the message bus (see <xref linkend='message-bus-routing-match-rules'/>).
+ If the bus does not have enough resources the <literal>org.freedesktop.DBus.Error.OOM</literal>
+ error is returned.
+ </para>
+ </sect3>
+ <sect3 id="bus-messages-remove-match">
+ <title><literal>org.freedesktop.DBus.RemoveMatch</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ RemoveMatch (in STRING rule)
+ </programlisting>
+ Message arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>STRING</entry>
+ <entry>Match rule to remove from the connection</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Removes the first rule that matches (see <xref linkend='message-bus-routing-match-rules'/>).
+ If the rule is not found the <literal>org.freedesktop.DBus.Error.MatchRuleNotFound</literal>
+ error is returned.
+ </para>
+ </sect3>
+
+ <sect3 id="bus-messages-get-id">
+ <title><literal>org.freedesktop.DBus.GetId</literal></title>
+ <para>
+ As a method:
+ <programlisting>
+ GetId (out STRING id)
+ </programlisting>
+ Reply arguments:
+ <informaltable>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Argument</entry>
+ <entry>Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0</entry>
+ <entry>STRING</entry>
+ <entry>Unique ID identifying the bus daemon</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ Gets the unique ID of the bus. The unique ID here is shared among all addresses the
+ bus daemon is listening on (TCP, UNIX domain socket, etc.) and its format is described in
+ <xref linkend="uuids"/>. Each address the bus is listening on also has its own unique
+ ID, as described in <xref linkend="addresses"/>. The per-bus and per-address IDs are not related.
+ There is also a per-machine ID, described in <xref linkend="standard-interfaces-peer"/> and returned
+ by org.freedesktop.DBus.Peer.GetMachineId().
+ For a desktop session bus, the bus ID can be used as a way to uniquely identify a user's session.
+ </para>
+ </sect3>
+
</sect2>
</sect1>
<glossentry id="term-message"><glossterm>Message</glossterm>
<glossdef>
<para>
- A message is the atomic unit of communication via the D-BUS
+ A message is the atomic unit of communication via the D-Bus
protocol. It consists of a <firstterm>header</firstterm> and a
<firstterm>body</firstterm>; the body is made up of
<firstterm>arguments</firstterm>.
<para>
See <xref linkend="term-bus-name"/>. "Name" may
also be used to refer to some of the other names
- in D-BUS, such as interface names.
+ in D-Bus, such as interface names.
</para>
</glossdef>
</glossentry>
<para>
An application talking directly to another application, without going
through a message bus. One-to-one connections may be "peer to peer" or
- "client to server." The D-BUS protocol has no concept of client
+ "client to server." The D-Bus protocol has no concept of client
vs. server after a connection has authenticated; the flow of messages
is symmetrical (full duplex).
</para>
<glossentry id="term-path"><glossterm>Path</glossterm>
<glossdef>
<para>
- Object references (object names) in D-BUS are organized into a
+ Object references (object names) in D-Bus are organized into a
filesystem-style hierarchy, so each object is named by a path. As in
LDAP, there's no difference between "files" and "directories"; a path
can refer to an object, while still having child objects below it.
</glossary>
</article>
-
projects / platform / upstream / dbus.git / blobdiff