Merge remote-tracking branch 'origin/typescript' into receipt-field-separators

src/incoming-requests.ts

@@ -39,6 +39,7 @@ export class IncomingRequests {
 	private readonly session: Session;
 	private readonly smsIdFormat: SmsIdFormat;
 	private readonly systemId: string;
+	private linkGeneration = 0;
 
 	constructor(options: IncomingRequestsOptions) {
 		this.dlrMerger = options.dlrMerger;
@@ -62,8 +63,17 @@ export class IncomingRequests {
 	}
 
 	async handle(pduObj: PduObject): Promise<void> {
+		const generation = this.linkGeneration;
+
 		if (this.onRequest && await this.onRequest(this.session, pduObj)) return;
 
+		// The link it arrived on went while the hook ran, so nothing we answer now correlates.
+		if (this.linkGeneration !== generation) {
+			this.log.info('session - dropping a request whose link went', { cmdName: pduObj.cmdName });
+
+			return;
+		}
+
 		if (!this.session.bindAllows(pduObj.cmdName)) {
 			this.log.info('session - command the peer\'s bind direction does not carry', {
 				bindType: this.session.boundAs ?? '',
@@ -96,6 +106,7 @@ 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 +174,8 @@ export class IncomingRequests {
 
 		if (!first) return;
 
+		const generation = this.linkGeneration;
+
 		const sms = createSms({
 			from: paramText(first.params.source_addr),
 			message: decodeSegments(pduObjs),
@@ -170,6 +183,7 @@ export class IncomingRequests {
 			session: this.session,
 			to: paramText(first.params.destination_addr),
 		}, {
+			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/sms.ts

@@ -38,7 +38,7 @@ export type Sms = {
 	/** Answers every segment. Part of the protocol, not optional. Defaults to ESME_ROK. */
 	sendResp: (options?: SendRespOptions) => Promise<VoidResult>;
 	session: Session;
-	/** The id answered to the peer: what sendResp() was given, or a generated UUID v7. */
+	/** The id `sendResp()` was given, or a generated UUID v7. */
 	readonly smsId: string;
 	submitTime: Date;
 	to: string;
@@ -54,6 +54,7 @@ export type SmsInput = {
 
 /** What the session's incoming side gives a message so it can be answered and accounted for. */
 export type SmsHandlers = {
+	lostLink: () => boolean;
 	onAnswered: () => void;
 	send: (input: PduObjectInput) => Promise<Result<{ pduObj: PduObject }>>;
 };
@@ -76,7 +77,8 @@ export function createSms(input: SmsInput, handlers: SmsHandlers): Sms {
 		message: input.message,
 		pduObjs: input.pduObjs,
 		sendDlr: status => sendDlr(sms, handlers.send, status),
-		sendResp: options => sendResp(sms, answered, options ?? {}).finally(handlers.onAnswered),
+		sendResp: options => sendResp(sms, answered, options ?? {}, handlers.lostLink)
+			.finally(handlers.onAnswered),
 		session: input.session,
 		get smsId(): string {
 			return answered.smsId;
@@ -92,6 +94,7 @@ async function sendResp(
 	sms: Sms,
 	answered: { smsId: string },
 	options: SendRespOptions,
+	lostLink: () => boolean,
 ): Promise<VoidResult> {
 	const total = sms.pduObjs.length;
 
@@ -105,6 +108,11 @@ async function sendResp(
 
 	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') };
+	}
+
 	const results = await Promise.all(sms.pduObjs.map((pduObj, index) => sms.session.sendReturn(
 		pduObj,
 		options.status ?? 'ESME_ROK',