Implement XEP-0343: Signaling WebRTC Data Channels in Jingle. The current version of the
XEP (0.3.1) has no implementation and contains some flaws. After discussing this on xsf@,
Daniel (from Conversations) mentioned that they had a sprint with Larma (from Dino) to
work on another version and provided me with this link:
https://gist.github.com/iNPUTmice/6c56f3e948cca517c5fb129016d99e74 . I have used it for my
implementation.
This implementation reuses work done on Jingle A/V call (notably XEP-0176 and XEP-0167
plugins), with adaptations. When used, XEP-0234 will not handle the file itself as it
normally does. This is because WebRTC has several implementations (browser for web
interface, GStreamer for others), and file/data must be handled directly by the frontend.
This is particularly important for web frontends, as the file is not sent from the backend
but from the end-user's browser device.
Among the changes, there are:
- XEP-0343 implementation.
- `file_send` bridge method now use serialised dict as output.
- New `BaseTransportHandler.is_usable` method which get content data and returns a boolean
(default to `True`) to tell if this transport can actually be used in this context (when
we are initiator). Used in webRTC case to see if call data are available.
- Support of `application` media type, and everything necessary to handle data channels.
- Better confirmation message, with file name, size and description when available.
- When file is accepted in preflight, it is specified in following `action_new` signal for
actual file transfer. This way, frontend can avoid the display or 2 confirmation
messages.
- XEP-0166: when not specified, default `content` name is now its index number instead of
a UUID. This follows the behaviour of browsers.
- XEP-0353: better handling of events such as call taken by another device.
- various other updates.
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Use of `pickle` to serialise data was a technical legacy that was causing trouble to store
in database, to update (if a class was serialised, a change could break update), and to
security (pickle can lead to code execution).
This patch remove all use of Pickle in favour in JSON, notably:
- for caching data, a Pydantic model is now used instead
- for SQLAlchemy model, the LegacyPickle is replaced by JSON serialisation
- in XEP-0373 a class `PublicKeyMetadata` was serialised. New method `from_dict` and
`to_dict` method have been implemented to do serialisation.
- new methods to (de)serialise data can now be specified with Identity data types. It is
notably used to (de)serialise `path` of avatars.
A migration script has been created to convert data (for upgrade or downgrade), with
special care for XEP-0373 case. Depending of size of database, this migration script can
be long to run.
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`init_script_path` option can be used in `[DEFAULTS]` to run a script at the end of
backend initialisation. A new `init_pre_script` method is used to wait for backend to
reach this stage (designed to be used mostly by CLI frontend), then the usual `ready_get`
method is finished once the script is finished.
folloing packages refactoring, legacy pickled values could not be unpickled (due to use of
old classes). This temporary workaround fix it, but the right thing to do will be to move
from pickle to JSON at some point.
