Call signaling, from the WASM¶

signaling documents the <call> stanza family as seen on the wire (websocket-capture). This page is the WASM-side view: what the Web calling engine's own code reveals about how it builds and parses those stanzas. Because it is a different technique over the same protocol, where the two agree a fact is corroborated toward confirmed; where the WASM shows something the wire captures have not, it is a new probable lead.

Confidence. probable (one static technique). Provenance: module wa.wasm SHA-1 3638a50...; technique wasm-analysis · tool warden · contributor purpshell · source: commit history. Evidence here is the engine's own log and parse-error strings, which name operations and attributes literally; the stanza tags themselves are WABinary tokens, not strings, so this recovers the vocabulary and logic, not raw tag bytes.

The call control is Rust¶

The call-control core is Rust (call_control::ffi, call_control::ffi_utils), compiled into the module and heavily inlined. That is why the signaling handlers do not appear as clean, separately-named functions (they collapse into a few mega-functions alongside the C++ WAWapWriter.cpp serializer and wa_call_xml_utils.cc); the readable surface is the strings. The C++ side handles WABinary serialization; the Rust side owns the call state machine.

Signaling operations (recovered)¶

The engine's strings name the handlers for each phase of a call:

Offer. parse_xmpp_offer (fill_common_header), handle_incoming_xmpp_offer, preprocess_offer (with a "caller has been timeout already / sending call missed event" path), pending-offer buffering (can_buffer_as_pending_call_offer, handle_pending_call_offer), and an offer v2 path (make_v2_offer_for_invite, enable_offer_v2_upgrade, fast_call_setup_callee_v2).
Ack / nack. handle_offer_ack (de-dupes "duplicate call offer ack"), handle_offer_nack (creates a device jid).
Preaccept. handle_preaccept (looks up device info).
Accept. handle_accept -> call_update_participant_keys.
Rekey. handle_enc_rekey (e.g. "Rekey master sent enc_rekey for bot removal, scheduling E2EE restore timer") - the keying rotation path.
Relay / transport msgs. handle_incoming_relay_msg, parse_bwe_info_from_relay_latency_msg (the relaylatency stanza), relay rebinding and latency probes.
Summary / teardown. fill_call_summary parses the terminal node.

Stanza attributes (recovered)¶

Parse-error strings reveal real attribute names the engine reads off <call> child nodes:

attribute	seen in	note
`call-creator`	offer, call summary, waiting room	the initiator
`call_id`	throughout	per-call id
`call_duration`	call summary	terminal stat
`user_pn`	call summary user	participant phone number
`state`	call summary user	per-user state
`media`	waiting room	media type
`link-token`	waiting room	call-link join token
`jid`	waiting room user, devices	participant/device jid

Call state machine¶

The engine runs an explicit state machine via change_call_state, with named states - one captured verbatim is ConnectedLonely ("call is ConnectedLonely, ignore the request to set call state to %s"). Reconnection logic is visible too ("entering reconnecting while e2e signaling probe works", "... while relay e2e bind probe works"), as is device-switch handling (handle_device_switch_stream_recreation: skipping in call_state=%s). Enumerating all states is open.

Group calls, call links, and waiting rooms¶

Beyond 1:1 (wacrg's current scope), the binary shows the group surface:

Group updates arrive as XMPP MESSAGE GroupUpdate (with call_id, transaction_id, media_type), parsed by convert_xmpp_group_info_to_group_info.
Call links / waiting rooms: is_call_link / is_from_call_link, invited, a link-token attribute, and a waiting-room admission flow (handle_waiting_room, serialize_waiting_room_admit, update_call_group_with_waiting_room_user).

These corroborate that the same <call> machinery scales from 1:1 to group/link calls, and mark where a 1:1-scoped spec stops.

Corroboration vs. new¶

Corroborates the wire spec: the offer/preaccept/accept/terminate phases and the relaylatency and call-creator facts now have a second technique behind them (static wasm-analysis alongside websocket-capture) - candidates to promote toward confirmed.
New leads (WASM-only so far): the offer v2 upgrade path, the explicit call state machine (ConnectedLonely, reconnect probes), precall E2E bind, the waiting-room / call-link flow, and the fill_call_summary attribute set (call_duration, user_pn, state).

Open questions¶

The raw WABinary tag tokens for each <call> child (offer, accept, and the rest), which are tokenized, not string-literal, in the binary.
The full call-state enum and its transitions (owned by the Rust core).
The exact offer v1 vs v2 structural difference.
How precall_e2e_bind sequences relative to the SRTP/SFrame keying.