[Feature] Support delayed event delegation for legacy JWT request (#3946)

* make `delayed_leave_event_delay_ms` and `network_error_retry_ms` mandatory

* Support delegation for legacy  jwt request

* Calculate `maximumNetworkErrorRetryCount` based on timeouts

src/config/ConfigOptions.ts

@@ -164,6 +164,14 @@ export interface ResolvedConfigOptions extends ConfigOptions {
   };
   sync_disconnect_grace_period_ms: number;
   ssla: string;
+  matrix_rtc_session: {
+    wait_for_key_rotation_ms?: number;
+    delayed_leave_event_delay_ms: number;
+    delayed_leave_event_restart_local_timeout_ms?: number;
+    delayed_leave_event_restart_ms?: number;
+    network_error_retry_ms: number;
+    membership_event_expiry_ms?: number;
+  };
 }
 
 export const DEFAULT_CONFIG: ResolvedConfigOptions = {
@@ -178,4 +186,8 @@ export const DEFAULT_CONFIG: ResolvedConfigOptions = {
   },
   sync_disconnect_grace_period_ms: 10000,
   ssla: "https://static.element.io/legal/element-software-and-services-license-agreement-uk-1.pdf",
+  matrix_rtc_session: {
+    delayed_leave_event_delay_ms: 10000,
+    network_error_retry_ms: 1000,
+  },
 };

src/livekit/openIDSFU.test.ts

@@ -84,6 +84,99 @@ describe("getSFUConfigWithOpenID", () => {
     expect.fail("Expected test to throw;");
   });
 
+  it("should retry without delay params if the JWT service legacy endpoint returns M_BAD_JSON 400", async () => {
+    let callCount = 0;
+
+    fetchMock.post(
+      "https://sfu.example.org/sfu/get",
+      (url, opts) => {
+        callCount++;
+        const body = JSON.parse(opts.body as string);
+
+        // First call: check if it has delay parts and return 400
+        if (callCount === 1) {
+          expect(body).toHaveProperty("delay_id", "mock_delay_id");
+          return {
+            status: 400,
+            body: { errcode: "M_BAD_JSON", error: "Unsupported parameters" },
+          };
+        }
+
+        // Second call: check if delay parts were stripped and return success
+        expect(body).not.toHaveProperty("delay_id");
+        expect(body).not.toHaveProperty("delay_timeout");
+        expect(body).not.toHaveProperty("delay_cs_api_url");
+
+        return {
+          status: 200,
+          body: { url: sfuUrl, jwt: testJWTToken },
+        };
+      },
+      { overwriteRoutes: true },
+    );
+
+    // Note: Assuming getSFUConfigWithOpenID eventually calls getLiveKitJWT
+    const config = await getSFUConfigWithOpenID(
+      matrixClient,
+      ownMemberMock,
+      "https://sfu.example.org",
+      "!example_room_id",
+      {
+        delayEndpointBaseUrl: "https://matrix.homeserverserver.org",
+        delayId: "mock_delay_id",
+      },
+    );
+
+    expect(config.jwt).toBe(testJWTToken);
+    expect(callCount).toBe(2);
+    void (await fetchMock.flush());
+  });
+
+  it("should successfully send delay parameters to the JWT service legacy endpoint", async () => {
+    fetchMock.post(
+      "https://sfu.example.org/sfu/get",
+      (url, opts) => {
+        const body = JSON.parse(opts.body as string);
+
+        // Verify, that the request contains the expected delay parameters
+        if (
+          body.delay_id === "mock_delay_id" &&
+          body.delay_timeout === 10000 &&
+          body.delay_cs_api_url === "https://homeserverserver.org/cs_api"
+        ) {
+          return {
+            status: 200,
+            body: { url: sfuUrl, jwt: testJWTToken },
+          };
+        }
+        return {
+          status: 400,
+          body: { error: "Missing expected delay params" },
+        };
+      },
+      { overwriteRoutes: true },
+    );
+
+    const config = await getSFUConfigWithOpenID(
+      matrixClient,
+      ownMemberMock,
+      "https://sfu.example.org",
+      "!example_room_id",
+      {
+        delayEndpointBaseUrl: "https://homeserverserver.org/cs_api",
+        delayId: "mock_delay_id",
+      },
+    );
+
+    // Prüfe das Ergebnis
+    expect(config).toMatchObject({
+      jwt: testJWTToken,
+      url: sfuUrl,
+    });
+
+    void (await fetchMock.flush());
+  });
+
   it("should try legacy and then new endpoint with delay delegation", async () => {
     fetchMock.post("https://sfu.example.org/get_token", () => {
       return {
@@ -121,7 +214,7 @@ describe("getSFUConfigWithOpenID", () => {
     expect(calls[0][0]).toStrictEqual("https://sfu.example.org/get_token");
     expect(calls[0][1]).toStrictEqual({
       // check if it uses correct delayID!
-      body: '{"room_id":"!example_room_id","slot_id":"m.call#ROOM","member":{"id":"@alice:example.org:DEVICE","claimed_user_id":"@alice:example.org","claimed_device_id":"DEVICE"},"delay_id":"mock_delay_id","delay_timeout":1000,"delay_cs_api_url":"https://matrix.homeserverserver.org"}',
+      body: '{"room_id":"!example_room_id","slot_id":"m.call#ROOM","member":{"id":"@alice:example.org:DEVICE","claimed_user_id":"@alice:example.org","claimed_device_id":"DEVICE"},"delay_id":"mock_delay_id","delay_timeout":10000,"delay_cs_api_url":"https://matrix.homeserverserver.org"}',
       method: "POST",
       headers: {
         "Content-Type": "application/json",
@@ -131,7 +224,7 @@ describe("getSFUConfigWithOpenID", () => {
     expect(calls[1][0]).toStrictEqual("https://sfu.example.org/sfu/get");
 
     expect(calls[1][1]).toStrictEqual({
-      body: '{"room":"!example_room_id","device_id":"DEVICE"}',
+      body: '{"room":"!example_room_id","device_id":"DEVICE","delay_id":"mock_delay_id","delay_timeout":10000,"delay_cs_api_url":"https://matrix.homeserverserver.org"}',
       headers: {
         "Content-Type": "application/json",
       },
@@ -176,7 +269,7 @@ describe("getSFUConfigWithOpenID", () => {
     expect(calls[0][0]).toStrictEqual("https://sfu.example.org/get_token");
     expect(calls[0][1]).toStrictEqual({
       // check if it uses correct delayID!
-      body: '{"room_id":"!example_room_id","slot_id":"m.call#ROOM","member":{"id":"@alice:example.org:DEVICE","claimed_user_id":"@alice:example.org","claimed_device_id":"DEVICE"},"delay_id":"mock_delay_id","delay_timeout":1000,"delay_cs_api_url":"https://matrix.homeserverserver.org"}',
+      body: '{"room_id":"!example_room_id","slot_id":"m.call#ROOM","member":{"id":"@alice:example.org:DEVICE","claimed_user_id":"@alice:example.org","claimed_device_id":"DEVICE"},"delay_id":"mock_delay_id","delay_timeout":10000,"delay_cs_api_url":"https://matrix.homeserverserver.org"}',
       method: "POST",
       headers: {
         "Content-Type": "application/json",

src/livekit/openIDSFU.ts

@@ -155,6 +155,8 @@ export async function getSFUConfigWithOpenID(
       serviceUrl,
       roomId,
       openIdToken,
+      opts?.delayEndpointBaseUrl,
+      opts?.delayId,
     );
     logger?.info(`Got JWT from call's active focus URL.`);
     return extractFullConfigFromToken(sfuConfig);
@@ -187,20 +189,62 @@ async function getLiveKitJWT(
   livekitServiceURL: string,
   matrixRoomId: string,
   openIDToken: IOpenIDToken,
+  delayEndpointBaseUrl?: string,
+  delayId?: string,
 ): Promise<{ url: string; jwt: string }> {
-  const res = await doNetworkOperationWithRetry(async () => {
+  interface IDelayParams {
+    delay_id?: string;
+    delay_timeout?: number;
+    delay_cs_api_url?: string;
+  }
+  let bodyDalayParts: IDelayParams = {};
+  // Also check for empty string
+  if (delayId && delayEndpointBaseUrl) {
+    const delayTimeoutMs =
+      Config.get().matrix_rtc_session?.delayed_leave_event_delay_ms;
+    bodyDalayParts = {
+      delay_id: delayId,
+      delay_timeout: delayTimeoutMs,
+      delay_cs_api_url: delayEndpointBaseUrl,
+    };
+  }
+
+  const makeRequest = async (delayParts: IDelayParams): Promise<Response> => {
     return await fetch(livekitServiceURL + "/sfu/get", {
       method: "POST",
       headers: {
         "Content-Type": "application/json",
       },
       body: JSON.stringify({
-        // This is the actual livekit room alias. For the legacy jwt endpoint simply the room id was used.
+        // The legacy JWT endpoint uses only the matrix room id to calculate the livekit room alias.
+        // However, the livekit room alias is provided as part of the JWT payload.
         room: matrixRoomId,
         openid_token: openIDToken,
         device_id: deviceId,
+        ...delayParts,
       }),
     });
+  };
+
+  const res = await doNetworkOperationWithRetry(async () => {
+    let response = await makeRequest(bodyDalayParts);
+
+    // Old service compatibility check
+    const oldServiceDoesNotSupportDelayParts =
+      response.status === 400 && Object.keys(bodyDalayParts).length > 0;
+    // If http status 400 with M_BAD_JSON and we sent delay parts, retry without them
+    if (oldServiceDoesNotSupportDelayParts) {
+      try {
+        const errorBody = await response.json();
+        if (errorBody.errcode === "M_BAD_JSON") {
+          response = await makeRequest({});
+        }
+      } catch {
+        // If we can't parse the error, treat as real error
+      }
+    }
+
+    return response;
   });
 
   if (!res.ok) {
@@ -241,7 +285,7 @@ export async function getLiveKitJWTWithDelayDelegation(
   // Also check for empty string
   if (delayId && delayEndpointBaseUrl) {
     const delayTimeoutMs =
-      Config.get().matrix_rtc_session?.delayed_leave_event_delay_ms ?? 1000;
+      Config.get().matrix_rtc_session?.delayed_leave_event_delay_ms;
     bodyDalayParts = {
       delay_id: delayId,
       delay_timeout: delayTimeoutMs,

src/state/CallViewModel/localMember/LocalMember.ts

@@ -778,6 +778,19 @@ export function enterRTCSession(
     };
   }
 
+  // Calculates `maximumNetworkErrorRetryCount`. The connection is failed if EITHER:
+  // - The /sync loop is unresponsive for > `gracePeriod` ms, or
+  // - A delayed leave event is emitted (after `leaveDelay` ms period).
+  // Note: Use leaveDelay >> gracePeriod for delegated leave events.
+  const gracePeriod = Config.get().sync_disconnect_grace_period_ms;
+  const leaveDelay = matrixRtcSessionConfig?.delayed_leave_event_delay_ms;
+  const retryInterval = matrixRtcSessionConfig?.network_error_retry_ms;
+
+  // Math.min is used to account for the respective worst case: /sync not available or leave event emitted.
+  const maxWaitTime = Math.min(gracePeriod, leaveDelay);
+  const maximumNetworkErrorRetryCount =
+    Math.ceil(maxWaitTime / retryInterval) + 1;
+
   // Multi-sfu does not need a preferred foci list. just the focus that is actually used.
   // TODO where/how do we track errors originating from the ongoing rtcSession?
 
@@ -803,6 +816,7 @@ export function enterRTCSession(
       membershipEventExpiryMs:
         matrixRtcSessionConfig?.membership_event_expiry_ms,
       unstableSendStickyEvents: matrixRTCMode === MatrixRTCMode.Matrix_2_0,
+      maximumNetworkErrorRetryCount: maximumNetworkErrorRetryCount,
     },
   );
 }