From 35d862ebd3e198e1ac2a02a5ed268f82890c9980 Mon Sep 17 00:00:00 2001
From: Andrew Ferrazzutti <andrewf@element.io>
Date: Mon, 11 Nov 2024 15:48:53 -0500
Subject: [PATCH] Handle M_MAX_DELAY_EXCEEDED errors (#4511)

* Handle M_MAX_DELAY_EXCEEDED errors

Use a lower delay time if the server rejects a delay as too long.

* Add test

* Lint test

* Update src/matrixrtc/MatrixRTCSession.ts

Co-authored-by: Robin <robin@robin.town>

* Test computed expiry timeout value

---------

Co-authored-by: Robin <robin@robin.town>
---
 spec/unit/matrixrtc/MatrixRTCSession.spec.ts | 22 ++++++++++++++++-
 src/matrixrtc/MatrixRTCSession.ts            | 26 +++++++++++++++++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/spec/unit/matrixrtc/MatrixRTCSession.spec.ts b/spec/unit/matrixrtc/MatrixRTCSession.spec.ts
index 6b45a93025..fb62a669c7 100644
--- a/spec/unit/matrixrtc/MatrixRTCSession.spec.ts
+++ b/spec/unit/matrixrtc/MatrixRTCSession.spec.ts
@@ -508,6 +508,19 @@ describe("MatrixRTCSession", () => {
 
                 jest.useFakeTimers();
 
+                // preparing the delayed disconnect should handle the delay being too long
+                const sendDelayedStateExceedAttempt = new Promise<void>((resolve) => {
+                    const error = new MatrixError({
+                        "errcode": "M_UNKNOWN",
+                        "org.matrix.msc4140.errcode": "M_MAX_DELAY_EXCEEDED",
+                        "org.matrix.msc4140.max_delay": 7500,
+                    });
+                    sendDelayedStateMock.mockImplementationOnce(() => {
+                        resolve();
+                        return Promise.reject(error);
+                    });
+                });
+
                 // preparing the delayed disconnect should handle ratelimiting
                 const sendDelayedStateAttempt = new Promise<void>((resolve) => {
                     const error = new MatrixError({ errcode: "M_LIMIT_EXCEEDED" });
@@ -541,7 +554,14 @@ describe("MatrixRTCSession", () => {
                     });
                 });
 
-                sess!.joinRoomSession([activeFocusConfig], activeFocus, { useLegacyMemberEvents: false });
+                sess!.joinRoomSession([activeFocusConfig], activeFocus, {
+                    useLegacyMemberEvents: false,
+                    membershipServerSideExpiryTimeout: 9000,
+                });
+
+                expect(sess).toHaveProperty("membershipServerSideExpiryTimeout", 9000);
+                await sendDelayedStateExceedAttempt.then(); // needed to resolve after the send attempt catches
+                expect(sess).toHaveProperty("membershipServerSideExpiryTimeout", 7500);
 
                 await sendDelayedStateAttempt;
                 jest.advanceTimersByTime(5000);
diff --git a/src/matrixrtc/MatrixRTCSession.ts b/src/matrixrtc/MatrixRTCSession.ts
index 5d4d90ea58..046591ede1 100644
--- a/src/matrixrtc/MatrixRTCSession.ts
+++ b/src/matrixrtc/MatrixRTCSession.ts
@@ -184,8 +184,18 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         return this.joinConfig?.useKeyDelay ?? 5_000;
     }
 
+    /**
+     * If the server disallows the configured {@link membershipServerSideExpiryTimeout},
+     * this stores a delay that the server does allow.
+     */
+    private membershipServerSideExpiryTimeoutOverride?: number;
+
     private get membershipServerSideExpiryTimeout(): number {
-        return this.joinConfig?.membershipServerSideExpiryTimeout ?? 8_000;
+        return (
+            this.membershipServerSideExpiryTimeoutOverride ??
+            this.joinConfig?.membershipServerSideExpiryTimeout ??
+            8_000
+        );
     }
 
     private get membershipKeepAlivePeriod(): number {
@@ -1141,6 +1151,20 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
                         );
                         this.disconnectDelayId = res.delay_id;
                     } catch (e) {
+                        if (
+                            e instanceof MatrixError &&
+                            e.errcode === "M_UNKNOWN" &&
+                            e.data["org.matrix.msc4140.errcode"] === "M_MAX_DELAY_EXCEEDED"
+                        ) {
+                            const maxDelayAllowed = e.data["org.matrix.msc4140.max_delay"];
+                            if (
+                                typeof maxDelayAllowed === "number" &&
+                                this.membershipServerSideExpiryTimeout > maxDelayAllowed
+                            ) {
+                                this.membershipServerSideExpiryTimeoutOverride = maxDelayAllowed;
+                                return prepareDelayedDisconnection();
+                            }
+                        }
                         logger.error("Failed to prepare delayed disconnection event:", e);
                     }
                 };