Tie the refusal to the link, not to the hold, so a released message is refused too

src/dlr-merger.ts

@@ -120,8 +120,8 @@ export class DlrMerger {
 	}
 
 	clear(): void {
-		this.groups.takeAll();
-		this.spent.takeAll();
+		this.groups.clear();
+		this.spent.clear();
 	}
 
 	/** Drops every group past its deadline. Runs before each collect and on its own timer. */

src/expiring-groups.ts

@@ -58,14 +58,9 @@ export class ExpiringGroups<T> {
 		this.idle();
 	}
 
-	/** Removes every group and hands them over. */
-	takeAll(): [string, T][] {
-		const taken: [string, T][] = [...this.entries].map(([key, entry]) => [key, entry.group]);
-
+	clear(): void {
 		this.entries.clear();
 		this.idle();
-
-		return taken;
 	}
 
 	/** Removes every group past its deadline and hands them over. */

src/held-messages.ts

@@ -20,7 +20,6 @@ function keyOf(pduObjs: PduObject[]): string | undefined {
 
 /** The messages handed to the application that it has not answered yet, held by their segments. */
 export class HeldMessages {
-	private readonly droppedWithLink = new WeakSet<PduObject[]>();
 	private readonly held: ExpiringGroups<PduObject[]>;
 	private readonly idleWaiters = new IdleWaiters();
 	private readonly log: SmppLog;
@@ -65,11 +64,6 @@ export class HeldMessages {
 		return key !== undefined && this.held.get(key) === pduObjs;
 	}
 
-	/** Whether this message's link went before it was answered, so no answer of ours correlates. */
-	lostLink(pduObjs: PduObject[]): boolean {
-		return this.droppedWithLink.has(pduObjs);
-	}
-
 	release(pduObjs: PduObject[]): void {
 		const key = keyOf(pduObjs);
 
@@ -82,10 +76,7 @@ export class HeldMessages {
 
 	/** Drops every message: their segments went with the link, so no answer of ours correlates now. */
 	clear(): void {
-		for (const [, pduObjs] of this.held.takeAll()) {
-			this.droppedWithLink.add(pduObjs);
-		}
-
+		this.held.clear();
 		this.idleWaiters.settle();
 	}
 

src/incoming-requests.ts

@@ -39,6 +39,8 @@ export class IncomingRequests {
 	private readonly session: Session;
 	private readonly smsIdFormat: SmsIdFormat;
 	private readonly systemId: string;
+	/** Bumped when a link goes, so a message from an earlier one knows its answer cannot correlate. */
+	private linkGeneration = 0;
 
 	constructor(options: IncomingRequestsOptions) {
 		this.dlrMerger = options.dlrMerger;
@@ -96,6 +98,7 @@ export class IncomingRequests {
 
 	/** Drops the segments of every message that never became whole, and of every one still held. */
 	clear(): void {
+		this.linkGeneration++;
 		this.held.clear();
 		this.reassembler.clear();
 	}
@@ -163,6 +166,8 @@ export class IncomingRequests {
 
 		if (!first) return;
 
+		const generation = this.linkGeneration;
+
 		const sms = createSms({
 			from: paramText(first.params.source_addr),
 			message: decodeSegments(pduObjs),
@@ -170,7 +175,7 @@ export class IncomingRequests {
 			session: this.session,
 			to: paramText(first.params.destination_addr),
 		}, {
-			lostLink: () => this.held.lostLink(pduObjs),
+			lostLink: () => this.linkGeneration !== generation,
 			// A turn later, so a listener sending its receipt straight after the response still holds.
 			onAnswered: () => { setImmediate(() => { this.held.release(pduObjs); }); },
 			// Past the refusal only while a drain is still waiting for this message; an ordinary send after.

src/reassembly.ts

@@ -163,7 +163,7 @@ export class Reassembler {
 	}
 
 	clear(): void {
-		this.groups.takeAll();
+		this.groups.clear();
 		this.octets = 0;
 	}
 

src/sms.ts

@@ -54,7 +54,6 @@ export type SmsInput = {
 
 /** What the session's incoming side gives a message so it can be answered and accounted for. */
 export type SmsHandlers = {
-	/** Whether the link this message arrived on is gone, so no answer of ours correlates. */
 	lostLink: () => boolean;
 	onAnswered: () => void;
 	send: (input: PduObjectInput) => Promise<Result<{ pduObj: PduObject }>>;
@@ -107,13 +106,13 @@ async function sendResp(
 		return { err: new Error('smsId must not be empty') };
 	}
 
+	if (options.smsId !== undefined) answered.smsId = options.smsId;
+
 	// A response carries the sequence number it was asked on, which the next link knows nothing about.
 	if (lostLink()) {
 		return { err: new Error('The link this message arrived on is gone, so nothing would correlate the response') };
 	}
 
-	if (options.smsId !== undefined) answered.smsId = options.smsId;
-
 	const results = await Promise.all(sms.pduObjs.map((pduObj, index) => sms.session.sendReturn(
 		pduObj,
 		options.status ?? 'ESME_ROK',