webrtc.h File Reference

WebRTC P2P signaling for discovery mode failover. More...

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Functions
webrtc_signaling_callbacks_t	discovery_webrtc_get_direct_signaling_callbacks (acip_transport_t *tcp_transport, const uint8_t session_id[16], const uint8_t participant_id[16])
	Create signaling callbacks for direct peer-to-peer connection during failover.
void	discovery_webrtc_set_tcp_transport (acip_transport_t *transport)
	Set the TCP transport for direct peer-to-peer signaling.
void	discovery_webrtc_set_session_context (const uint8_t session_id[16], const uint8_t participant_id[16])
	Set session and participant IDs for direct signaling.
void	discovery_webrtc_cleanup_transport (void)
	Cleanup and release the direct peer-to-peer transport.

Detailed Description

WebRTC P2P signaling for discovery mode failover.

Provides WebRTC peer connection management for discovery mode failover scenarios. When a host dies and participants need to connect to the pre-elected future host, they establish P2P connections using WebRTC DataChannels.

Key Difference from Client Mode:

• Client mode: SDP/ICE exchanged through ACDS relay (client connected to host for media)
• Discovery failover: SDP/ICE exchanged directly over TCP to new host (P2P connection)
• Both use the same WebRTC library (libdatachannel) but with different signaling paths

Architecture

During migration:

1. Participant detects host disconnect
2. Participant knows new host's address from pre-election (FUTURE_HOST_ELECTED)
3. Participant connects TCP to new host
4. Participant sends SDP OFFER directly over TCP (not through ACDS)
5. New host sends SDP ANSWER directly over TCP
6. Both exchange ICE candidates directly
7. WebRTC P2P connection established
8. Media flows peer-to-peer (or through TURN)

Author

Zachary Fogg me@zf.nosp@m.o.gg

Date

January 2026

Definition in file discovery/webrtc.h.

Function Documentation

discovery_webrtc_cleanup_transport()

void discovery_webrtc_cleanup_transport

(

void

)

Cleanup and release the direct peer-to-peer transport.

Clears the TCP transport used for direct signaling. Called on migration completion or when the P2P connection is torn down.

Note

Actual transport cleanup (closing connections, freeing resources) should be done by caller before calling this.

Thread-safe.

Definition at line 291 of file src/discovery/webrtc.c.

                                              {
  ensure_mutex_initialized();
  mutex_lock(&g_webrtc_mutex);
 
  g_tcp_transport = NULL;
  g_session_context.is_set = false;
 
  mutex_unlock(&g_webrtc_mutex);
}

discovery_webrtc_get_direct_signaling_callbacks()

webrtc_signaling_callbacks_t discovery_webrtc_get_direct_signaling_callbacks	(	acip_transport_t *	tcp_transport,
		const uint8_t	session_id[16],
		const uint8_t	participant_id[16]
	)

Create signaling callbacks for direct peer-to-peer connection during failover.

Returns callbacks that send SDP/ICE directly over TCP to the peer (not through ACDS). Used when participants reconnect to a new host after migration.

Parameters

tcp_transport	TCP transport connected to the new host
session_id	Session UUID (16 bytes, copied)
participant_id	Local participant UUID (16 bytes, copied)

Returns

Signaling callbacks for use with peer manager

Note

The returned structure points to static callbacks and is valid for program lifetime.

TCP transport must be connected and valid when callbacks are invoked.

Set tcp_transport to NULL to disable the callbacks.

Definition at line 244 of file src/discovery/webrtc.c.

                                                                                                               {
  ensure_mutex_initialized();
  mutex_lock(&g_webrtc_mutex);
 
  g_tcp_transport = tcp_transport;
 
  if (session_id && participant_id) {
    memcpy(g_session_context.session_id, session_id, 16);
    memcpy(g_session_context.participant_id, participant_id, 16);
    g_session_context.is_set = true;
  }
 
  mutex_unlock(&g_webrtc_mutex);
 
  webrtc_signaling_callbacks_t callbacks = {
      .send_sdp = discovery_send_sdp,
      .send_ice = discovery_send_ice,
      .user_data = NULL, // Unused - we use global state
  };
 
  return callbacks;
}

References participant_id, and session_id.

discovery_webrtc_set_session_context()

void discovery_webrtc_set_session_context	(	const uint8_t	session_id[16],
		const uint8_t	participant_id[16]
	)

Set session and participant IDs for direct signaling.

Configures the session context used when sending SDP/ICE messages directly. Must be called before peer manager generates any local descriptions.

Parameters

session_id	Session UUID (16 bytes, copied)
participant_id	Local participant UUID (16 bytes, copied)

Note

Callbacks will fail with ERROR_INVALID_STATE if IDs are not set.

Definition at line 276 of file src/discovery/webrtc.c.

                                                                                                          {
  ensure_mutex_initialized();
  mutex_lock(&g_webrtc_mutex);
 
  if (session_id && participant_id) {
    memcpy(g_session_context.session_id, session_id, 16);
    memcpy(g_session_context.participant_id, participant_id, 16);
    g_session_context.is_set = true;
  } else {
    g_session_context.is_set = false;
  }
 
  mutex_unlock(&g_webrtc_mutex);
}

References participant_id, and session_id.

discovery_webrtc_set_tcp_transport()

void discovery_webrtc_set_tcp_transport

(

acip_transport_t *

transport

)

Set the TCP transport for direct peer-to-peer signaling.

Configures the transport that will be used to send SDP/ICE messages directly to the peer (bypassing ACDS). Must be called before peer manager generates any local descriptions.

Parameters

transport

TCP transport to new host (NULL to disable)

Note

This is separate from the ACDS transport used in client mode.

Callbacks will fail with ERROR_INVALID_STATE if transport is NULL.

Definition at line 269 of file src/discovery/webrtc.c.

                                                                     {
  ensure_mutex_initialized();
  mutex_lock(&g_webrtc_mutex);
  g_tcp_transport = transport;
  mutex_unlock(&g_webrtc_mutex);
}