version: 1
Date: 30 mai 2016
Author: José Bollo
The name afb-daemon stands for Application Framework Binder Daemon. That is why afb-daemon is also named the binder.
Afb-daemon is in charge to bind one instance of an application to the AGL framework and AGL system.
On the following figure, you can use a typical use of afb-daemon:
Figure: binder afb-daemon, basis
. . . . . . . . . . . . . . . . . . . . . . . . . .
. Isolated security context .
. .
. +------------------------------+ .
. | | .
. | A P P L I C A T I O N | .
. | | .
. +--------------+---------------+ .
. | .
. | .
. +-------------------+----------------------+ .
. | : | .
. | b i n d e r : | .
. | A F B - D A E M O N : PLUGINS | .
. | : | .
. +-------------------+----------------------+ .
. | .
. . . . . . . . . . . . | . . . . . . . . . . . . .
|
v
AGL SYSTEM
The application and its companion binder run in secured and isolated environment set for them. Applications are intended to access to AGL system through the binder.
The binder afb-daemon serves multiple purposes:
It acts as a gateway for the application to access the system;
It acts as an HTTP server for serving files to HTML5 applications;
It allows HTML5 applications to have native extensions subject to security enforcement for accessing hardware ressources or for speeding parts of algorithm.
This section tries to give a better understanding of the binder usage through several use cases.
One of the most interresting aspect of using the binder afb-daemon is the ability to run applications remotely. This feature is possible because the binder afb-daemon implements native web protocols.
So the figure binder, basis would become when the application is run remotely:
Figure: binder afb-daemon and remotely running application
+------------------------------+
| |
| A P P L I C A T I O N |
| |
+--------------+---------------+
|
~ ~ ~ ~ ~ ~
: NETWORK :
~ ~ ~ ~ ~ ~
|
. . . . . . . . . . . . . . | . . . . . . . . . . . . . .
. Isolated security | .
. context | .
. | .
. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . .
. . F I R E W A L L . .
. . . .
. . . . . . . . . . . . . . . . . . . . . . . . . .
. | .
. +-------------------+----------------------+ .
. | : | .
. | A F B - D A E M O N : PLUGINS | .
. | : | .
. +-------------------+----------------------+ .
. | .
. . . . . . . . . . . . . . | . . . . . . . . . . . . . .
|
v
AGL SYSTEM
Applications can provide with their packaged delivery a plugin. That plugin will be instanciated for each application instance. The methods of the plugin will be accessible by applications and will be excuted within the security context.
It is possible to run the binder afb-daemon as a daemon that provides the API of its plugins.
This will be used for:
offering common APIs
provide application’s services (services provided as application)
In that case, the figure showing the whole aspects is
Figure: binder afb-daemon for services
. . . . . . . . . . . . . . . . . . . . . .
. Isolated security context application .
. .
. +------------------------------+ .
. | | .
. | A P P L I C A T I O N | .
. | | .
. +--------------+---------------+ . . . . . . . . . . . . . . . . . . . . . . .
. | . . Isolated security context A .
. | . . .
. +-----------------+------------------+ . . +------------------------------------+ .
. | : | . . | : | .
. | b i n d e r : | . . | b i n d e r : service | .
. | A F B - D A E M O N : PLUGINS | . . | A F B - D A E M O N : PLUGINS | .
. | : | . . | : A | .
. +-----------------+------------------+ . . +-----------------+------------------+ .
. | . . | .
. . . . . . . . . . | . . . . . . . . . . . . . . . . . . . . . | . . . . . . . . . . .
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v v
================================================================================
D - B U S & C Y N A R A
================================================================================
^ ^
| |
. . . . . . . . . . | . . . . . . . . . . . . . . . . . . . . . | . . . . . . . . . . .
. | . . | .
. +-----------------+------------------+ . . +-----------------+------------------+ .
. | : | . . | : | .
. | b i n d e r : service | . . | b i n d e r : service | .
. | A F B - D A E M O N : PLUGINS | . . | A F B - D A E M O N : PLUGINS | .
. | : B | . . | : C | .
. +------------------------------------+ . . +------------------------------------+ .
. . . .
. Isolated security context B . . Isolated security context C .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
For this case, the binder afb-daemon takes care to attribute one single session context to each client instance. It allows plugins to store and retrieve data associated to each of its client.
The binder can instanciate plugins. The primary use of plugins is to add native methods that can be accessed by applications written with any language through web technologies ala JSON RPC.
This simple idea is declined to serves multiple purposes:
add native feature to applications
add common API available by any applications
provide customers services
A specific document explains how to write an afb-daemon binder plugin: HOWTO WRITE a PLUGIN for AFB-DAEMON
The launch options for binder afb-daemon are:
--help
Prints help with available options
--version
Display version and copyright
--verbose
Increases the verbosity, can be repeated
--port=xxxx
HTTP listening TCP port [default 1234]
--rootdir=xxxx
HTTP Root Directory [default $AFBDIR or else $HOME/.AFB]
--rootbase=xxxx
Angular Base Root URL [default /opa]
This is used for any application of kind OPA (one page application).
When set, any missing document whose url has the form /opa/zzz
is translated to /opa/#!zzz
--rootapi=xxxx
HTML Root API URL [default /api]
The plugins are available within that url.
--alias=xxxx
Maps a path located anywhere in the file system to the
a subdirectory. The syntax for mapping a PATH to the
subdirectory NAME is: --alias=/NAME:PATH.
Example: --alias=/icons:/usr/share/icons maps the
content of /usr/share/icons within the subpath /icons.
This option can be repeated.
--apitimeout=xxxx
Plugin API timeout in seconds [default 20]
Defines how many seconds maximum a method is allowed to run.
0 means no limit.
--cntxtimeout=xxxx
Client Session Timeout in seconds [default 3600]
--cache-eol=xxxx
Client cache end of live [default 100000 that is 27,7 hours]
--sessiondir=xxxx
Sessions file path [default rootdir/sessions]
--session-max=xxxx
Maximum count of simultaneous sessions [default 10]
--ldpaths=xxxx
Load Plugins from given paths separated by colons
as for dir1:dir2:plugin1.so:... [default = $libdir/afb]
You can mix path to directories and to plugins.
The sub-directories of the given directories are searched
recursively.
The plugins are the files terminated by '.so' (the extension
so denotes shared object) that contain the public entry symbol.
--plugin=xxxx
Load the plugin of given path.
--token=xxxx
Initial Secret token to authenticate.
If not set, no client can authenticate.
If set to the empty string, then any initial token is accepted.
--mode=xxxx
Set the mode: either local, remote or global.
The mode indicate if the application is run locally on the host
or remotely through network.
--readyfd=xxxx
Set the #fd to signal when ready
If set, the binder afb-daemon will write "READY=1\n" on the file
descriptor whose number if given (/proc/self/fd/xxx).
--dbus-client=xxxx
Transparent binding to a binder afb-daemon service through dbus.
It creates an API of name xxxx that is implemented remotely
and queried via DBUS.
--dbus-server=xxxx
Provides a binder afb-daemon service through dbus.
The name xxxx must be the name of an API defined by a plugin.
This API is exported through DBUS.
--foreground
Get all in foreground mode (default)
--daemon
Get all in background mode
The binder afb-daemon would launch the applications directly.
The current setting of mode (local/remote/global) might be reworked to a mechanism for querying configuration variables.
Implements “one-shot” initial token. It means that after its first authenticated use, the initial token is removed and no client can connect anymore.
Creates some intrinsic APIs.
Make the service connection using WebSocket not DBUS.
Management of targetted events.
Securisation of LOA.
Integration of the protocol JSON-RPC for the websockets.