Add membershipID to call memberships (#3745)

* Add membershipID to call memberships

This allows us to recognise easily when a membership is from some
previous sessions rather than our own and therefore ignore it
(see comment for more).

This was causing us to see existing, expired membership events and
bump the expiry on them rather than send a new membership. This might
have been okay if we bumped them enough to actually make them un-expired,
but it's a fresh session so semanticly we want to post a fresh membership
rather than resurrecting a previous, expired membership.

* Fix test types

* Fix tests

* Make test coverage happy

---------

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

spec/unit/matrixrtc/CallMembership.spec.ts

@@ -23,6 +23,7 @@ const membershipTemplate: CallMembershipData = {
     application: "m.call",
     device_id: "AAAAAAA",
     expires: 5000,
+    membershipID: "bloop",
 };
 
 function makeMockEvent(originTs = 0): MatrixEvent {

spec/unit/matrixrtc/MatrixRTCSession.spec.ts

@@ -26,6 +26,7 @@ const membershipTemplate: CallMembershipData = {
     application: "m.call",
     device_id: "AAAAAAA",
     expires: 60 * 60 * 1000,
+    membershipID: "bloop",
 };
 
 const mockFocus = { type: "mock" };
@@ -56,6 +57,7 @@ describe("MatrixRTCSession", () => {
         expect(sess?.memberships[0].scope).toEqual("m.room");
         expect(sess?.memberships[0].application).toEqual("m.call");
         expect(sess?.memberships[0].deviceId).toEqual("AAAAAAA");
+        expect(sess?.memberships[0].membershipID).toEqual("bloop");
         expect(sess?.memberships[0].isExpired()).toEqual(false);
     });
 
@@ -219,6 +221,7 @@ describe("MatrixRTCSession", () => {
                             device_id: "AAAAAAA",
                             expires: 3600000,
                             foci_active: [{ type: "mock" }],
+                            membershipID: expect.stringMatching(".*"),
                         },
                     ],
                 },
@@ -286,6 +289,7 @@ describe("MatrixRTCSession", () => {
                                 expires: 3600000 * 2,
                                 foci_active: [{ type: "mock" }],
                                 created_ts: 1000,
+                                membershipID: expect.stringMatching(".*"),
                             },
                         ],
                     },
@@ -357,6 +361,7 @@ describe("MatrixRTCSession", () => {
                         device_id: "AAAAAAA",
                         expires: 3600000,
                         foci_active: [mockFocus],
+                        membershipID: expect.stringMatching(".*"),
                     },
                 ],
             },
@@ -388,6 +393,7 @@ describe("MatrixRTCSession", () => {
                         device_id: "OTHERDEVICE",
                         expires: 3600000,
                         created_ts: 1000,
+                        membershipID: expect.stringMatching(".*"),
                     },
                     {
                         application: "m.call",
@@ -396,6 +402,7 @@ describe("MatrixRTCSession", () => {
                         device_id: "AAAAAAA",
                         expires: 3600000,
                         foci_active: [mockFocus],
+                        membershipID: expect.stringMatching(".*"),
                     },
                 ],
             },

spec/unit/matrixrtc/MatrixRTCSessionManager.spec.ts

@@ -26,6 +26,7 @@ const membershipTemplate: CallMembershipData = {
     application: "m.call",
     device_id: "AAAAAAA",
     expires: 60 * 60 * 1000,
+    membershipID: "bloop",
 };
 
 describe("MatrixRTCSessionManager", () => {

src/matrixrtc/CallMembership.ts

@@ -29,6 +29,7 @@ export interface CallMembershipData {
     created_ts?: number;
     expires: number;
     foci_active?: Focus[];
+    membershipID: string;
 }
 
 export class CallMembership {
@@ -64,6 +65,10 @@ export class CallMembership {
         return this.data.scope;
     }
 
+    public get membershipID(): string {
+        return this.data.membershipID;
+    }
+
     public createdTs(): number {
         return this.data.created_ts ?? this.parentEvent.getTs();
     }

src/matrixrtc/MatrixRTCSession.ts

@@ -23,6 +23,7 @@ import { EventType } from "../@types/event";
 import { CallMembership, CallMembershipData } from "./CallMembership";
 import { Focus } from "./focus";
 import { MatrixEvent } from "../matrix";
+import { randomString } from "../randomstring";
 
 const MEMBERSHIP_EXPIRY_TIME = 60 * 60 * 1000;
 const MEMBER_EVENT_CHECK_PERIOD = 2 * 60 * 1000; // How often we check to see if we need to re-send our member event
@@ -54,6 +55,14 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
     // if we're not yet joined
     private relativeExpiry: number | undefined;
 
+    // An identifier for our membership of the call. This will allow us to easily recognise
+    // whether a membership was sent by this session or is stale from some other time.
+    // It also forces our membership events to be unique, because otherwise we could try
+    // to overwrite a membership from a previous session but it would do nothing because the
+    // event content would be identical. We need the origin_server_ts to update though, so
+    // forcing unique content fixes this.
+    private membershipId: string | undefined;
+
     private memberEventTimeout?: ReturnType<typeof setTimeout>;
     private expiryTimeout?: ReturnType<typeof setTimeout>;
 
@@ -174,6 +183,7 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         logger.info(`Joining call session in room ${this.room.roomId}`);
         this.activeFoci = activeFoci;
         this.relativeExpiry = MEMBERSHIP_EXPIRY_TIME;
+        this.membershipId = randomString(5);
         this.emit(MatrixRTCSessionEvent.JoinStateChanged, true);
         // We don't wait for this, mostly because it may fail and schedule a retry, so this
         // function returning doesn't really mean anything at all.
@@ -195,6 +205,7 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         logger.info(`Leaving call session in room ${this.room.roomId}`);
         this.relativeExpiry = undefined;
         this.activeFoci = undefined;
+        this.membershipId = undefined;
         this.emit(MatrixRTCSessionEvent.JoinStateChanged, false);
         this.triggerCallMembershipEventUpdate();
     }
@@ -249,6 +260,9 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         if (this.relativeExpiry === undefined) {
             throw new Error("Tried to create our own membership event when we're not joined!");
         }
+        if (this.membershipId === undefined) {
+            throw new Error("Tried to create our own membership event when we have no membership ID!");
+        }
 
         const m: CallMembershipData = {
             call_id: "",
@@ -257,6 +271,7 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
             device_id: this.client.getDeviceId()!,
             expires: this.relativeExpiry,
             foci_active: this.activeFoci,
+            membershipID: this.membershipId,
         };
 
         if (prevMembership) m.created_ts = prevMembership.createdTs();
@@ -373,7 +388,7 @@ export class MatrixRTCSession extends TypedEventEmitter<MatrixRTCSessionEvent, M
         const myPrevMembershipData = memberships.find((m) => m.device_id === localDeviceId);
         let myPrevMembership;
         try {
-            if (myCallMemberEvent && myPrevMembershipData) {
+            if (myCallMemberEvent && myPrevMembershipData && myPrevMembershipData.membershipID === this.membershipId) {
                 myPrevMembership = new CallMembership(myCallMemberEvent, myPrevMembershipData);
             }
         } catch (e) {