src/livekit/auth now fronts two flows. For a transport with a LiveKit SFU
`url`, tokens come from our own homeserver's MSC4195 get_token endpoint
and delayed leaves are delegated through delegate_delayed_leave, both via
the js-sdk's unstable client methods. Transports with only a
livekit_service_url keep using the OpenID flow against the JWT service.
A transport advertising both shapes lets a subscriber fall back to the
OpenID flow when the homeserver answers get_token with a 404 (Synapse
reports M_UNRECOGNIZED for unknown routes rather than M_NOT_FOUND), so a
client can still join calls hosted on servers that have not deployed
MSC4195 yet. Publishers never fall back: a homeserver that advertises a
`url` but does not implement the endpoints is misconfigured and the
admin should hear about it, so they get NoMatrix2AuthorizationService.
Delegation uses the same flow as the token so that the participant
identity the service computes matches.
The local member only probes a transport's delegate_delayed_leave
endpoint when it has a service URL. The developer settings tab validates
a custom service URL through the same facade.
A transport with only a LiveKit SFU `url` has to be authenticated through
our own homeserver, which needs to know the name of the server owning the
SFU. Carry that name alongside the transport as a TransportLocator,
derived from the member's user ID for remote transports and from the
client's domain for our own, and key the connection map on the SFU URL,
the service URL and the server name together so that `url`, service URL
and combined transport shapes are deduplicated consistently.
getLocalTransport no longer authenticates with the SFU up front and hands
the resulting config to the connection. Instead the ConnectionManager tags
the connection whose transport equals the local one as the publisher, and
every Connection fetches its own SFU config for its role.
The local member now only joins the MatrixRTC session once its connection
is authenticated, so that the LiveKit room exists before remote members
try to get a subscriber token for it. Subscribers authenticating with the
OpenID flow lack permission to create the room and would otherwise fail
without retrying, causing a cascade of leaves and rejoins at the start of
a call.
The OpenID flow moves to src/livekit/auth/openID.ts with the SFU config
types in a sibling file, takes an options object, and replaces the
MatrixRTC mode with the role we take on the transport plus the session's
slot ID instead of a hard-coded m.call#ROOM.
This changes behaviour: publishers on a livekit_service_url transport
always use the legacy /sfu/get endpoint, so that subscribers can predict
their user:device participant identity, and subscribers always use the
default /get_token endpoint. The MatrixRTC mode no longer influences which
endpoint is used.
As of the removal of 'Legacy' mode, there can no longer be a difference between the transport you advertise in your membership and the transport you publish media on, so the local transport code can be simplified considerably. For instance, the function which gets the local transport can simply return a promise rather than being reactive.
I kept the local transport as an Observable in other modules so that they could easily be tested with existing marble tests.
Since we removed the extra 'legacy' mode, meaning there's nothing simplified anymore by translating things over to a JWT service version.
(Also, simplify some things by making the mode static for the duration of a call.)
This approach is more flexible in that it allows even the local participant to share their screen in CallViewModel tests, and more rigorous in that it ensures that application code is reacting specifically to track publications.
While looking into what had regressed https://github.com/element-hq/element-call/issues/3588, I found that 28047217b8 had filled in a couple of behaviors with non-reactive default values, the "natural window mode" behavior being among them. This meant that the app would no longer determine the correct window mode upon joining a call, instead always guessing "normal" as the value. This change restores its reactivity.
Johannes Marbach