Refuse a bind bound() cannot record, and document it for a 0.4.0 consumer

src/client.ts

@@ -174,7 +174,10 @@ async function bind(session: Session, options: ClientOptions): Promise<VoidResul
 		return { err: new Error(`Remote host refused login: ${sent.pduObj.cmdStatus ?? 'unknown'}`) };
 	}
 
-	session.bound(bindType, sent.pduObj.tlvs.sc_interface_version?.tagValue);
+	const recorded = session.bound(bindType, sent.pduObj.tlvs.sc_interface_version?.tagValue);
+
+	if (recorded.err) return recorded;
+
 	session.log.info('client - bound', { bindType, systemId });
 
 	return {};

src/server.ts

@@ -177,9 +177,9 @@ async function acceptBind(
 	options: ServerOptions,
 	identity: Record<string, string>,
 ): Promise<void> {
-	session.bound(bindType, pduObj.params.interface_version);
+	const recorded = session.bound(bindType, pduObj.params.interface_version);
 
-	await session.sendReturn(pduObj, 'ESME_ROK', identity, bindRespTlvs(session, options));
+	await session.sendReturn(pduObj, recorded.err ? 'ESME_RBINDFAIL' : 'ESME_ROK', identity, bindRespTlvs(session, options));
 }
 
 async function onBind(

src/session-options.ts

@@ -121,6 +121,29 @@ export const defaultSystemId = '';
 /** SMPP 3.4: a peer that declares no version at all is one from before optional parameters. */
 export const undeclaredInterfaceVersion = 0x00;
 
+export type SessionBind = { as: BindType; peerVersion: number };
+
+const bindTypes: readonly string[] = ['receiver', 'transceiver', 'transmitter'];
+
+function isBindType(value: unknown): value is BindType {
+	return typeof value === 'string' && bindTypes.includes(value);
+}
+
+/** A bind as `Session.bound()` records it: undefined declares no version, which is pre-3.4. */
+export function checkedBind(bindType: unknown, declaredVersion: unknown): Result<{ bind: SessionBind }> {
+	if (!isBindType(bindType)) {
+		return { err: new Error(`bindType must be ${bindTypes.join(', ')}, got ${namedValue(bindType)}`) };
+	}
+
+	if (declaredVersion === undefined) return { bind: { as: bindType, peerVersion: undeclaredInterfaceVersion } };
+
+	if (typeof declaredVersion !== 'number' || !Number.isInteger(declaredVersion) || declaredVersion < 0 || declaredVersion > 0xFF) {
+		return { err: new Error(`declaredVersion must be 0-255, or undefined where the peer declared none, got ${namedValue(declaredVersion)}`) };
+	}
+
+	return { bind: { as: bindType, peerVersion: declaredVersion } };
+}
+
 export const defaults = {
 	/** Receipts of a multipart message can be a working day apart, so the cap does the bounding. */
 	dlrMergeTimeout: 86_400_000,

src/session.ts

@@ -4,7 +4,7 @@ import type { MessageDlr } from './dlr-merger.ts';
 import type { ParamValue } from './defs/types.ts';
 import type { PduObject, PduObjectInput, TlvInputs } from './pdu.ts';
 import type { PduRefusedError } from './pdu-refusal.ts';
-import type { BindType, CloseOptions, LinkEnd, OnRequest, ReconnectOptions, SendOptions, SessionEvents, SessionOptions } from './session-options.ts';
+import type { BindType, CloseOptions, LinkEnd, OnRequest, ReconnectOptions, SendOptions, SessionBind, SessionEvents, SessionOptions } from './session-options.ts';
 import type { Result, VoidResult } from './result.ts';
 import type { SendSmsOptions, SendSmsResult } from './send-sms.ts';
 import type { SmppLog } from './log.ts';
@@ -19,7 +19,7 @@ import { ReconnectLoop } from './reconnect-loop.ts';
 import { leftOf } from './idle-waiters.ts';
 import { errorFrom } from './error-from.ts';
 import { optionalParamsMinVersion } from './defs/constants.ts';
-import { bindCarries, bindCommands, defaultSystemId, defaults, undeclaredInterfaceVersion } from './session-options.ts';
+import { bindCarries, bindCommands, checkedBind, defaultSystemId, defaults } from './session-options.ts';
 import { isResp, objToPdu, pduReturn } from './pdu.ts';
 import { refusalAnswer } from './pdu-refusal.ts';
 import { guardedLog } from './log.ts';
@@ -58,7 +58,7 @@ export class Session extends EventEmitter<SessionEvents> {
 	linkEnd: LinkEnd = 'esme';
 	userData: unknown = undefined;
 
-	private bind: { as: BindType; peerVersion: number } | undefined = undefined;
+	private bind: SessionBind | undefined = undefined;
 
 	private readonly concatReference = new ConcatReference();
 	private readonly dlrMerger: DlrMerger;
@@ -161,11 +161,13 @@ export class Session extends EventEmitter<SessionEvents> {
 		return this.bind?.peerVersion;
 	}
 
-	/** Records a bind this link accepted or had accepted, until the next one. A version that is not a number is none. */
-	bound(bindType: BindType, declaredVersion: unknown): void {
-		const peerVersion = typeof declaredVersion === 'number' ? declaredVersion : undeclaredInterfaceVersion;
+	/** Records a bind this link accepted or had accepted, until the next one. */
+	bound(bindType: BindType, declaredVersion: unknown): VoidResult {
+		const checked = checkedBind(bindType, declaredVersion);
 
-		this.bind = { as: bindType, peerVersion };
+		if (!checked.err) this.bind = checked.bind;
+
+		return checked.err ? { err: checked.err } : {};
 	}
 
 	/** Whether this session's bind direction carries a command. Consulted by the library's senders. */
@@ -175,8 +177,7 @@ export class Session extends EventEmitter<SessionEvents> {
 
 	/** SMPP 3.4 forbids sending optional parameters to a peer that declared an older version. */
 	acceptsOptionalParams(): boolean {
-		return this.peerInterfaceVersion === undefined
-			|| this.peerInterfaceVersion >= optionalParamsMinVersion;
+		return this.peerInterfaceVersion === undefined || this.peerInterfaceVersion >= optionalParamsMinVersion;
 	}
 
 	/** Sends a request and resolves with the peer's response. */