signaling.c File Reference

🎬 WebRTC SDP/ICE signaling relay implementation More...

Go to the source code of this file.

Data Structures
struct	find_client_context_t
	Context for finding client by participant_id. More...
struct	broadcast_context_t
	Context for broadcasting to session participants. More...

Functions
asciichat_error_t	signaling_relay_sdp (session_registry_t *registry, tcp_server_t *tcp_server, const acip_webrtc_sdp_t *sdp, size_t total_packet_len)
	Relay SDP offer/answer to recipient.
asciichat_error_t	signaling_relay_ice (session_registry_t *registry, tcp_server_t *tcp_server, const acip_webrtc_ice_t *ice, size_t total_packet_len)
	Relay ICE candidate to recipient.
asciichat_error_t	signaling_broadcast (session_registry_t *registry, tcp_server_t *tcp_server, const uint8_t session_id[16], packet_type_t packet_type, const void *packet, size_t packet_len)
	Broadcast packet to all session participants.

Detailed Description

🎬 WebRTC SDP/ICE signaling relay implementation

Pure relay server for WebRTC signaling - no media processing. Relays SDP offers/answers and ICE candidates between participants using participant_id → socket mapping from tcp_server client registry.

RCU Integration:

• Session lookups use RCU read-side critical sections (no locks)
• Lock-free hash table access with cds_lfht_for_each_entry

Definition in file signaling.c.

Function Documentation

signaling_broadcast()

asciichat_error_t signaling_broadcast	(	session_registry_t *	registry,
		tcp_server_t *	tcp_server,
		const uint8_t	session_id[16],
		packet_type_t	packet_type,
		const void *	packet,
		size_t	packet_len
	)

Broadcast packet to all session participants.

Sends packet to all participants in a session. Used internally by SDP/ICE relay when recipient_id is all zeros.

Parameters

registry	Session registry
tcp_server	TCP server with client registry
session_id	Session UUID
packet_type	Packet type to send
packet	Packet data to broadcast
packet_len	Packet length

Returns

ASCIICHAT_OK on success, error code otherwise

Definition at line 227 of file signaling.c.

                                                         {
  if (!registry || !tcp_server || !session_id || !packet) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "registry, tcp_server, session_id, or packet is NULL");
  }
 
  /* Find session by UUID - uses RCU lock-free iteration (no lock needed!) */
  rcu_read_lock();
 
  session_entry_t *session = NULL;
  session_entry_t *iter;
  struct cds_lfht_iter iter_ctx;
 
  /* Iterate through hash table using RCU-safe iterator */
  cds_lfht_for_each_entry(registry->sessions, &iter_ctx, iter, hash_node) {
    if (uuid_equals(iter->session_id, session_id)) {
      session = iter;
      break;
    }
  }
 
  if (!session) {
    rcu_read_unlock();
    return SET_ERRNO(ERROR_NETWORK_PROTOCOL, "Session not found for broadcast");
  }
 
  rcu_read_unlock();
 
  // Broadcast to all participants in session
  broadcast_context_t ctx = {.target_session_id = session_id,
                             .packet_type = packet_type,
                             .packet = packet,
                             .packet_len = packet_len,
                             .sent_count = 0};
 
  tcp_server_foreach_client(tcp_server, broadcast_callback, &ctx);
 
  if (ctx.sent_count == 0) {
    log_warn("Broadcast sent to 0 participants (all offline or not joined yet)");
  } else {
    log_debug("Broadcast sent to %zu participants", ctx.sent_count);
  }
 
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, ERROR_INVALID_PARAM, ERROR_NETWORK_PROTOCOL, log_debug, log_warn, broadcast_context_t::sent_count, session_entry::session_id, session_id, session_registry_t::sessions, SET_ERRNO, broadcast_context_t::target_session_id, and tcp_server_foreach_client().

Referenced by signaling_relay_ice(), and signaling_relay_sdp().

signaling_relay_ice()

asciichat_error_t signaling_relay_ice	(	session_registry_t *	registry,
		tcp_server_t *	tcp_server,
		const acip_webrtc_ice_t *	ice,
		size_t	total_packet_len
	)

Relay ICE candidate to recipient.

Relays ICE packet to specific participant or broadcasts to all participants in the session if recipient_id is all zeros.

Parameters

registry	Session registry
tcp_server	TCP server with client registry
ice	ICE packet to relay (with variable-length candidate data following struct)
total_packet_len	Total packet length including variable data

Returns

ASCIICHAT_OK on success, error code otherwise

Definition at line 170 of file signaling.c.

                                                                                             {
  if (!registry || !tcp_server || !ice) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "registry, tcp_server, or ice is NULL");
  }
 
  /* Find session by UUID - uses RCU lock-free iteration (no lock needed!) */
  rcu_read_lock();
 
  session_entry_t *session = NULL;
  session_entry_t *iter;
  struct cds_lfht_iter iter_ctx;
 
  /* Iterate through hash table using RCU-safe iterator */
  cds_lfht_for_each_entry(registry->sessions, &iter_ctx, iter, hash_node) {
    if (uuid_equals(iter->session_id, ice->session_id)) {
      session = iter;
      break;
    }
  }
 
  if (!session) {
    rcu_read_unlock();
    return SET_ERRNO(ERROR_NETWORK_PROTOCOL, "Session not found for ICE relay");
  }
 
  rcu_read_unlock();
 
  // Check if broadcast (recipient_id all zeros) or unicast
  if (is_broadcast_uuid(ice->recipient_id)) {
    // Broadcast to all participants in session
    log_debug("Broadcasting ICE candidate to all participants in session");
    return signaling_broadcast(registry, tcp_server, ice->session_id, PACKET_TYPE_ACIP_WEBRTC_ICE, ice,
                               total_packet_len);
  } else {
    // Unicast to specific recipient
    find_client_context_t ctx = {
        .target_participant_id = ice->recipient_id, .found_socket = INVALID_SOCKET_VALUE, .found = false};
 
    tcp_server_foreach_client(tcp_server, find_participant_callback, &ctx);
 
    if (!ctx.found) {
      return SET_ERRNO(ERROR_NETWORK_PROTOCOL, "Recipient participant not found (may be offline)");
    }
 
    // Send ICE packet to recipient
    int result = send_packet(ctx.found_socket, PACKET_TYPE_ACIP_WEBRTC_ICE, ice, total_packet_len);
    if (result != 0) {
      return SET_ERRNO(ERROR_NETWORK, "Failed to send ICE packet to recipient");
    }
 
    log_debug("Relayed ICE candidate from sender to recipient (socket=%d)", ctx.found_socket);
  }
 
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, ERROR_INVALID_PARAM, ERROR_NETWORK, ERROR_NETWORK_PROTOCOL, find_client_context_t::found, find_client_context_t::found_socket, INVALID_SOCKET_VALUE, log_debug, PACKET_TYPE_ACIP_WEBRTC_ICE, send_packet(), session_entry::session_id, session_registry_t::sessions, SET_ERRNO, signaling_broadcast(), and tcp_server_foreach_client().

signaling_relay_sdp()

asciichat_error_t signaling_relay_sdp	(	session_registry_t *	registry,
		tcp_server_t *	tcp_server,
		const acip_webrtc_sdp_t *	sdp,
		size_t	total_packet_len
	)

Relay SDP offer/answer to recipient.

Relays SDP packet to specific participant or broadcasts to all participants in the session if recipient_id is all zeros.

Parameters

registry	Session registry
tcp_server	TCP server with client registry
sdp	SDP packet to relay (with variable-length SDP data following struct)
total_packet_len	Total packet length including variable data

Returns

ASCIICHAT_OK on success, error code otherwise

Definition at line 113 of file signaling.c.

                                                                                             {
  if (!registry || !tcp_server || !sdp) {
    return SET_ERRNO(ERROR_INVALID_PARAM, "registry, tcp_server, or sdp is NULL");
  }
 
  /* Find session by UUID - uses RCU lock-free iteration (no lock needed!) */
  rcu_read_lock();
 
  session_entry_t *session = NULL;
  session_entry_t *iter;
  struct cds_lfht_iter iter_ctx;
 
  /* Iterate through hash table using RCU-safe iterator */
  cds_lfht_for_each_entry(registry->sessions, &iter_ctx, iter, hash_node) {
    if (uuid_equals(iter->session_id, sdp->session_id)) {
      session = iter;
      break;
    }
  }
 
  if (!session) {
    rcu_read_unlock();
    return SET_ERRNO(ERROR_NETWORK_PROTOCOL, "Session not found for SDP relay");
  }
 
  rcu_read_unlock();
 
  // Check if broadcast (recipient_id all zeros) or unicast
  if (is_broadcast_uuid(sdp->recipient_id)) {
    // Broadcast to all participants in session
    log_debug("Broadcasting SDP to all participants in session");
    return signaling_broadcast(registry, tcp_server, sdp->session_id, PACKET_TYPE_ACIP_WEBRTC_SDP, sdp,
                               total_packet_len);
  } else {
    // Unicast to specific recipient
    find_client_context_t ctx = {
        .target_participant_id = sdp->recipient_id, .found_socket = INVALID_SOCKET_VALUE, .found = false};
 
    tcp_server_foreach_client(tcp_server, find_participant_callback, &ctx);
 
    if (!ctx.found) {
      return SET_ERRNO(ERROR_NETWORK_PROTOCOL, "Recipient participant not found (may be offline)");
    }
 
    // Send SDP packet to recipient
    int result = send_packet(ctx.found_socket, PACKET_TYPE_ACIP_WEBRTC_SDP, sdp, total_packet_len);
    if (result != 0) {
      return SET_ERRNO(ERROR_NETWORK, "Failed to send SDP packet to recipient");
    }
 
    log_debug("Relayed SDP from sender to recipient (socket=%d)", ctx.found_socket);
  }
 
  return ASCIICHAT_OK;
}

References ASCIICHAT_OK, ERROR_INVALID_PARAM, ERROR_NETWORK, ERROR_NETWORK_PROTOCOL, find_client_context_t::found, find_client_context_t::found_socket, INVALID_SOCKET_VALUE, log_debug, PACKET_TYPE_ACIP_WEBRTC_SDP, send_packet(), session_entry::session_id, session_registry_t::sessions, SET_ERRNO, signaling_broadcast(), and tcp_server_foreach_client().