juice_set_local_description usage order clarification

[tmathews]

Per discussion here paullouisageneau/libdatachannel#536 (comment), it sounds like the order of usage for juice_set_local_description and juice_set_remote_description matters to resolve ICE Role conflict (both controlling) errors.

I currently run into this warning, yet still get successful connections established. I would like clarity if this order is required to be correct even upon successful connections.

Many thanks for any advice. Cheers.

[paullouisageneau]

The warning means both peers think they are the initiator of the connection. It can be recovered at the price of an added round-trip, but it indicates a more fundamental issue in the way signaling is done.

ICE is designed around an initiating agent and responding agent. libjuice handles it automatically: the initiator calls juice_get_local_description() to send its description to the responder, the responder first sets the initiator's description with juice_set_remote_description(), then calls juice_get_local_description() to send its description back to the initiator which sets it with juice_set_remote_description().

This ensures proper parameter negotiation and role selection. The collision if both agents initiate the connection at the same time is handled as an ICE conflict.

[tmathews]

Thank you for the detailed answer.