version: 1
Date: 30 mai 2016
Author: José Bollo
This document describes application framework user daemon fundamentals. FCF (Fully Conform to Specification) implementation is still under development. It may happen that current implementation somehow diverges with specifications.
The daemon afm-user-daemon is in charge of handling applications on behalf of a user. Its main tasks are:
enumerate applications that end user can run and keep this list available on demand
start applications on behalf of end user, set user running environment, set user security context
list current runnable or running applications
stop (aka pause), continue (aka resume), terminate a running instance of a given application
transfer requests for installation/uninstallation of applications to the corresponding system daemon afm-system-daemon
The afm-user-daemon takes its orders from the session instance of D-Bus.
The figure below summarizes the situation of afm-user-daemon in the system.
+------------------------------------------------------------+
| User |
| +---------------------+ |
| +---------------------+ | Smack isolated | |
| | D-Bus session + | APPLICATIONS | |
| +----------+----------+ +---------+-----------+ |
| | | |
| | | |
| +----------+--------------------------+-----------+ |
| | | |
| | afm-user-daemon | |
| | | |
| +----------+----------------------+----------+----+ |
| | | : |
| | | : |
:================|======================|==========:=========:
| | | : |
| +----------+----------+ +-----+-----+ : |
| | D-Bus system +-----+ CYNARA | : |
| +----------+----------+ +-----+-----+ : |
| | | : |
| +----------+---------+ +-------+----------+----+ |
| | afm-system-daemon +----+ SECURITY-MANAGER | |
| +--------------------+ +-----------------------+ |
| |
| System |
+------------------------------------------------------------+
At start afm-user-daemon scans the directories containing applications and load in memory a list of avaliable applications accessible by current user.
When afm-system-daemon installs or removes an application. On success it sends the signal org.AGL.afm.system.changed. When receiving such a signal, afm-user-daemon rebuilds its applications list.
afm-user-daemon provides the data it collects about applications to its clients. Clients may either request the full list of avaliable applications or a more specific information about a given application.
afm-user-daemon launches application. Its builds a secure environment for the application before starting it within a secured environment.
Different kind of applications can be launched.
This is set using a configuration file that describes how to launch an application of a given kind within a given mode.
There is two launching modes: local or remote.
Launching an application locally means that the application and its binder are launched together.
Launching application remotely translates in only launching the application binder. The UI by itself has to be activated remotely by the requested (ie: HTML5 homescreen in a browser)
Once launched, running instances of application receive a runid that identify them.
afm-user-daemon manages the list of applications that it launched.
When owning the right permissions, a client can get the list of running instances and details about a specific running instance. It can also terminates, stops or continues a given application.
If the client own the right permissions, afm-user-daemon delegates that task to afm-system-daemon.
afm-user-daemon is launched as a systemd service attached to user sessions. Normally, the service file is located at /usr/lib/systemd/user/afm-user-daemon.service.
The options for launching afm-user-daemon are:
-a
--application directory
Includes the given application directory to
the database base of applications.
Can be repeated.
-r
--root directory
Includes root application directory or directories when
passing multiple rootdir to
applications database.
Note that default root directory for
applications is always added. In current version
/usr/share/afm/applications is used as default.
-m
--mode (local|remote)
Set the default launch mode.
The default value is 'local'
-d
--daemon
Daemonizes the process. It is not needed by sytemd.
-q
--quiet
Reduces the verbosity (can be repeated).
-v
--verbose
Increases the verbosity (can be repeated).
-h
--help
Prints a short help.
It contains rules for launching applications. When afm-user-daemon has to launch an application, it looks for launch mode (local or remote), as well as for the type of application describe in config.xml widget configuration file.
This tuple mode+type allows to select the adequate rule.
Configuration file is /etc/afm/afm-launch.conf.
It contains sections and rules. It can also contain comments and empty lines to improve readability.
The separators are space and tabulation, any other character should have a meaning.
The format is line oriented. The new line character separate the lines.
Lines having only separators are blank lines and ignored. Line having character #(sharp) at first position are comment lines and ignored.
Lines not starting with a separator are different from lines starting with a separator character.
The grammar of the configuration file is defined below:
CONF: *COMMENT *SECTION
SECTION: MODE *RULE
RULE: +TYPE VECTOR ?VECTOR
MODE: 'mode' +SEP ('local' | 'remote') *SEP EOL
TYPE: DATA *SEP EOL
VECTOR: +SEP DATA *(+SEP NDATA) *SEP EOL
DATA: CHAR *NCHAR
NDATA: +NCHAR
EOL: NL *COMMENT
COMMENT: *SEP CMT *(SEP | NCHAR) NL
NL: '\x0a'
SEP: '\x20' | '\x09'
CMT: '#'
CHAR: '\x00'..'\x08' | '\x0b'..'\x1f' | '\x21' | '\x22' | '\x24'..'\xff'
NCHAR: CMT | CHAR
Here is a sample of configuration file for defining how to launch an application of types application/x-executable, text/x-shellscript and text/html in local mode:
mode local
application/x-executable
text/x-shellscript
%r/%c
text/html
/usr/bin/afb-daemon --mode=local --readyfd=%R --alias=/icons:%I --port=%P --rootdir=%r --token=%S --sessiondir=%D/.afb-daemon
/usr/bin/web-runtime http://localhost:%P/%c?token=%S
This shows that:
Within this mode, the launchers have either one or two description vectors. All of those vectors are treated as programs and are executed with ‘execve’ system call.
The first vector is the leader vector and it defines the process group. The second vector (if any) is attached to the group defined by this first vector.
Within this mode, the launchers have either one or two vectors describing them.
The first vector is process as a program and is executed with system call ‘execve’.
The second vector (if any) defines a text that is returned to the caller. This mechanism can be used to return a uri for remote UI to connect on the newly launched application.
The daemon afm-user-daemon allocates a port for each new remote application. The current implementation port allocation is incremental. A smarter (cacheable and discoverable) allocation should be defined.
Vectors can include sequences of 2 characters that have a special meaning. These sequences are named %substitution because their first character is the percent sign (%) and because each occurrence of the sequence is replaced, at launch time, by the value associated to sequences.
Here is the list of %substitutions:
%%: %.
This simply emits the percent sign %
%a: appid
Holds application Id of launched application.
Defined by the attribute id of the element
%c: content
The file within the widget directory that is the entry point.
For HTML applications, it represents the relative path to main page (aka index.html).
Defined by attribute src of the element
%D: datadir
Path of the directory where the application runs (cwd) and stores its data.
It is equal to %h/%a.
%H: height
Requested height for the widget.
Defined by the attribute height of the element
%h: homedir
Path of the home directory for all applications.
It is generally equal to $HOME/app-data
%I: icondir
Path of the directory were the icons of the applications can be found.
%m: mime-type
Mime type of the launched application.
Defined by the attribute type of the element
%n: name
Name of the application as defined by the content of the
element
%p: plugins
In the future should represent the list of plugins and plugins directory separated by ‘,’. Warning: not supported in current version.
%P: port
A port to use. It is currently a kind of random port. The precise model is to be defined later.
%R: readyfd
Number of file descriptor to use for signaling readiness of launched process.
%r: rootdir
Path of directory containing the widget and its data.
%S: secret
An hexadecimal number that can be used to initialize pairing of client and application binder.
%W: width
Requested width for the widget.
Defined by the attribute width of the element
afm-user-daemon takes its orders from the session instance of D-Bus. D-Bus is nice to use in this context because it allows discovery and signaling.
The dbus session is by default addressed by environment variable DBUS_SESSION_BUS_ADDRESS. Using systemd variable DBUS_SESSION_BUS_ADDRESS is automatically set for user sessions.
The afm-user-daemon is listening on destination name org.AGL.afm.user at object path /org/AGL/afm/user on interface org.AGL.afm.user for following members: runnables, detail, start, terminate, stop, continue, runners, state, install and uninstall.
D-Bus is mainly used for signaling and discovery. Its optimized typed protocol is not used except for transmission of standalone strings.
Clients and Services are using JSON serialisation to exchange data.
The D-Bus interface is defined by:
DESTINATION: org.AGL.afm.user
PATH: /org/AGL/afm/user
INTERFACE: org.AGL.afm.user
The signature of any member of the interface is string -> string for JSON -> JSON.
This is the normal case. In case of error, the current implementation returns a dbus error as a string.
Here an example using dbus-send to query data on installed applications.
dbus-send --session --print-reply \
--dest=org.AGL.afm.user \
/org/AGL/afm/user \
org.AGL.afm.user.runnables string:true
The command line tool afm-util uses dbus-send to send orders to afm-user-daemon. This small scripts allows to send command to afm-user-daemon either interactively at shell prompt or scriptically.
The syntax is simple: it accept a command and when requires attached arguments.
Here is the summary of afm-util:
afm-util runnables :
list the runnable widgets installed
afm-util install wgt :
install the wgt file
afm-util uninstall id :
remove the installed widget of id
afm-util detail id :
print detail about the installed widget of id
afm-util runners :
list the running instance
afm-util start id :
start an instance of the widget of id
afm-util terminate rid :
terminate the running instance rid
afm-util stop rid :
stop the running instance rid
afm-util continue rid :
continue the previously rid
afm-util state rid :
get status of the running instance rid
Here is how to list applications using afm-util:
afm-util runnables
Recall:
DESTINATION: org.AGL.afm.user
PATH: /org/AGL/afm/user
INTERFACE: org.AGL.afm.user
Description: Get details about an application from its id.
Input: the id of the application as below.
Either just a string:
"appli@x.y"
Or an object having the field “id” of type string:
{"id":"appli@x.y"}
Output: A JSON object describing the application containing the fields described below.
{
"id": string, the application id (id@version)
"version": string, the version of the application
"width": integer, requested width of the application
"height": integer, resqueted height of the application
"name": string, the name of the application
"description": string, the description of the application
"shortname": string, the short name of the application
"author": string, the author of the application
}
Description: Get the list of applications that can be run.
Input: any valid json entry, can be anything except null.
output: An array of description of the runnable applications. Each item of the array contains an object containing the detail of an application as described above for the method org.AGL.afm.user.detail.
Description: Install an application from its widget file.
If an application of the same id and version exists, it is not reinstalled except when force=true.
Applications are installed in the subdirectories of the common directory reserved for applications. If root is specified, the application is installed under sub-directories of defined root.
Note that this methods is a simple accessor to the method org.AGL.afm.system.install of afm-system-daemon.
After the installation and before returning to the sender, afm-user-daemon sends the signal org.AGL.afm.user.changed.
Input: The path of widget file to be installed. Optionally, a flag to force reinstallation and/or a root directory.
Simple form a simple string containing the absolute widget path:
"/a/path/driving/to/the/widget"
Or an object:
{
"wgt": "/a/path/to/the/widget",
"force": false,
"root": "/a/path/to/the/root"
}
“wgt” and “root” MUST be absolute paths.
output: An object containing field “added” to use as application ID.
{"added":"appli@x.y"}
Description: Uninstall an application from its id.
Note that this methods is a simple accessor to org.AGL.afm.system.uninstall method from afm-system-daemon.
After the uninstallation and before returning to the sender, afm-user-daemon sends the signal org.AGL.afm.user.changed.
Input: the id of the application and, optionally, the path to application root.
Either a string:
"appli@x.y"
Or an object:
{
"id": "appli@x.y",
"root": "/a/path/to/the/root"
}
output: the value ‘true’.
Description:
Input: the id of the application and, optionally, the start mode as below.
Either just a string:
"appli@x.y"
Or an object containing field “id” of type string and optionally a field mode:
{"id":"appli@x.y","mode":"local"}
The field “mode” is a string equal to either “local” or “remote”.
output: The runid of the application launched. runid is an integer.
Description: Terminates the application attached to runid.
Input: The runid (an integer) of running instance to terminate.
output: the value ‘true’.
Description: Stops the application attached to runid until terminate or continue.
Input: The runid (integer) of the running instance to stop.
output: the value ‘true’.
Description: Continues the application attached to runid previously stopped.
Input: The runid (integer) of the running instance to continue.
output: the value ‘true’.
Description: Get informations about a running instance of runid.
Input: The runid (integer) of the running instance inspected.
output: An object describing instance state. It contains: the runid (integer), the id of the running application (string), the state of the application (string either: “starting”, “running”, “stopped”).
Example of returned state:
{
"runid": 2,
"state": "running",
"id": "appli@x.y"
}
Description: Get the list of currently running instances.
Input: anything.
output: An array of states, one per running instance, as returned by the methodd org.AGL.afm.user.state.