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fix(sync): harden canonical recovery

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This commit is contained in:
Timo
2026-08-25 21:21:18 +02:00
parent a65fe2f576
commit def5e1a380
10 changed files with 363 additions and 46 deletions
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server/index.js
+38 -3
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@@ -4,7 +4,7 @@ import { fileURLToPath } from 'url';
import { Server } from 'socket.io';
import crypto from 'crypto';
import dotenv from 'dotenv';
import { EVENTS, ERROR_CODES, OFFICIAL_SERVER_TOKEN, PROTOCOL_VERSION, CONTROL_MODES, CAPABILITIES, FORCE_SYNC_TIMEOUT, MAX_MEDIA_TIME } from '../shared/constants.js';
import { EVENTS, ERROR_CODES, OFFICIAL_SERVER_TOKEN, PROTOCOL_VERSION, CONTROL_MODES, CAPABILITIES, FORCE_SYNC_TARGET_TTL, MAX_MEDIA_TIME } from '../shared/constants.js';
import { createChatEnvelope } from './chat.js';
import {
commitForceSyncMediaState,
@@ -176,6 +176,18 @@ const HOST_ONLY_GATED_EVENTS = new Set([
EVENTS.EPISODE_LOBBY_CANCEL
]);
// Current clients sequence room-moving media commands. The relay mirrors the
// receiver-side stale guard so a frame ignored by live peers cannot become the
// canonical snapshot shown to a later joiner. Legacy clients omit seq entirely
// and retain their pre-feature behavior.
const SEQUENCED_ROOM_EVENTS = new Set([
EVENTS.PLAY,
EVENTS.PAUSE,
EVENTS.SEEK,
EVENTS.FORCE_SYNC_PREPARE,
EVENTS.FORCE_SYNC_EXECUTE
]);
// Features this relay supports, advertised to clients in ROOM_DATA so they can
// enable matching UI/behavior only when the server actually backs it. Append a
// flag here when a new server-gated feature ships (e.g. co-host promotion).
@@ -615,6 +627,29 @@ io.on('connection', (socket) => {
const validState = (val) => (val === 'playing' || val === 'paused') ? val : undefined;
const validBool = (val) => typeof val === 'boolean' ? val : undefined;
const hasSequenceField = data.seq !== undefined;
const sequence = Number.isSafeInteger(data.seq) && data.seq >= 0
? data.seq
: undefined;
if (SEQUENCED_ROOM_EVENTS.has(eventName)) {
if (hasSequenceField && sequence === undefined) {
log('ROOM', `Dropped ${eventName} with invalid seq from ${mapping.peerId}`);
return;
}
if (sequence !== undefined) {
if (socket.data.mediaSequencePeerId !== mapping.peerId) {
socket.data.mediaSequencePeerId = mapping.peerId;
socket.data.lastMediaSequence = null;
}
if (Number.isSafeInteger(socket.data.lastMediaSequence)
&& sequence <= socket.data.lastMediaSequence) {
log('ROOM', `Dropped stale ${eventName} from ${mapping.peerId} (seq ${sequence} <= ${socket.data.lastMediaSequence})`);
return;
}
socket.data.lastMediaSequence = sequence;
}
}
const existing = room.peerData.get(socket.id) || { peerId: mapping.peerId };
room.peerData.set(socket.id, {
...existing,
@@ -632,7 +667,7 @@ io.on('connection', (socket) => {
// --- S-3: Construct clean relay payload — never forward raw client data ---
const relayPayload = {
senderId: mapping.peerId,
seq: clampNum(data.seq, 0, Number.MAX_SAFE_INTEGER),
seq: sequence,
currentTime: data.currentTime === null ? null : clampNum(data.currentTime, 0, MAX_MEDIA_TIME),
targetTime: clampNum(data.targetTime, 0, MAX_MEDIA_TIME),
playbackState: validState(data.playbackState),
@@ -656,7 +691,7 @@ io.on('connection', (socket) => {
const forceSyncTarget = room.forceSyncTarget;
const targetExpired = forceSyncTarget
&& (!Number.isFinite(forceSyncTarget.preparedAt)
|| mediaStateNow - forceSyncTarget.preparedAt > FORCE_SYNC_TIMEOUT);
|| mediaStateNow - forceSyncTarget.preparedAt > FORCE_SYNC_TARGET_TTL);
if (!forceSyncTarget || targetExpired) {
log('ROOM', `Dropped force_sync_execute ${targetExpired ? 'with an expired target' : 'without a prepared target'} from ${mapping.peerId}`);
room.forceSyncInitiator = null;