fix(peripheral): Fix not using negotiated MTU

Author: Marco Crespi

lib/bindings/hci/gatt/local/Gatt.d.ts

@@ -7,6 +7,7 @@ export declare class HciGattLocal extends GattLocal {
     constructor(adapter: HciAdapter, hci: Hci, maxMtu?: number);
     private onAclStreamData;
     private errorResponse;
+    private getMtu;
     private handleMtuRequest;
     private handleFindInfoRequest;
     private handleFindByTypeRequest;

lib/bindings/hci/gatt/local/Gatt.js

@@ -91,6 +91,10 @@ export class HciGattLocal extends GattLocal {
 		return buf;
 	}
 
+	private getMtu(handle: number) {
+		return this.negotiatedMtus.get(handle) || 23;
+	}
+
 	private handleMtuRequest(_handle: number, _cid: number, request: Buffer) {
 		let mtu = request.readUInt16LE(1);
 
@@ -152,7 +156,7 @@ export class HciGattLocal extends GattLocal {
 			}
 
 			const lengthPerInfo = uuidSize === 2 ? 4 : 18;
-			const maxInfo = Math.floor((this._maxMtu - 2) / lengthPerInfo);
+			const maxInfo = Math.floor((this.getMtu(_handle) - 2) / lengthPerInfo);
 			numInfo = Math.min(numInfo, maxInfo);
 
 			response = Buffer.alloc(2 + numInfo * lengthPerInfo);
@@ -217,7 +221,7 @@ export class HciGattLocal extends GattLocal {
 
 		if (handles.length) {
 			const lengthPerHandle = 4;
-			const maxHandles = Math.floor((this._maxMtu - 1) / lengthPerHandle);
+			const maxHandles = Math.floor((this.getMtu(_handle) - 1) / lengthPerHandle);
 			const numHandles = Math.min(handles.length, maxHandles);
 
 			response = Buffer.alloc(1 + numHandles * lengthPerHandle);
@@ -274,7 +278,7 @@ export class HciGattLocal extends GattLocal {
 				}
 
 				const lengthPerService = uuidSize === 2 ? 6 : 20;
-				const maxServices = Math.floor((this._maxMtu - 2) / lengthPerService);
+				const maxServices = Math.floor((this.getMtu(_handle) - 2) / lengthPerService);
 				numServices = Math.min(numServices, maxServices);
 
 				response = Buffer.alloc(2 + numServices * lengthPerService);
@@ -345,7 +349,7 @@ export class HciGattLocal extends GattLocal {
 				}
 
 				const lengthPerCharacteristic = uuidSize === 2 ? 7 : 21;
-				const maxCharacteristics = Math.floor((this._maxMtu - 2) / lengthPerCharacteristic);
+				const maxCharacteristics = Math.floor((this.getMtu(_handle) - 2) / lengthPerCharacteristic);
 				numCharacteristics = Math.min(numCharacteristics, maxCharacteristics);
 
 				response = Buffer.alloc(2 + numCharacteristics * lengthPerCharacteristic);
@@ -408,7 +412,7 @@ export class HciGattLocal extends GattLocal {
 				}
 
 				if (responseStatus === CONST.ATT_ECODE_SUCCESS) {
-					const dataLength = Math.min(responseBuffer.length, this._maxMtu - 4);
+					const dataLength = Math.min(responseBuffer.length, this.getMtu(_handle) - 4);
 					response = Buffer.alloc(4 + dataLength);
 
 					response[0] = CONST.ATT_OP_READ_BY_TYPE_RESP;
@@ -485,7 +489,7 @@ export class HciGattLocal extends GattLocal {
 
 			if (result !== null) {
 				if (result === CONST.ATT_ECODE_SUCCESS) {
-					const dataLength = Math.min(data.length, this._maxMtu - 1);
+					const dataLength = Math.min(data.length, this.getMtu(_handle) - 1);
 					response = Buffer.alloc(1 + dataLength);
 
 					response[0] =

lib/bindings/hci/gatt/local/Gatt.js.map

@@ -184,6 +184,18 @@ export abstract class GattLocal extends Gatt {
 					object: newChar
 				};
 
+				if (char.properties.includes('indicate') || char.properties.includes('notify')) {
+					// notify or indicate: add client characteristic configuration descriptor
+					const newDescr = new GattDescriptorLocal(newChar, '2902', Buffer.from([0x00, 0x00]));
+
+					const clientCharacteristicConfigurationDescriptorHandle = handle++;
+					handles[clientCharacteristicConfigurationDescriptorHandle] = {
+						type: 'descriptor',
+						object: newDescr,
+						value: clientCharacteristicConfigurationDescriptorHandle
+					};
+				}
+
 				if (char.descriptors) {
 					for (const descr of char.descriptors) {
 						const newDescr = new GattDescriptorLocal(newChar, descr.uuid, descr.value);

lib/models/gatt/local/Gatt.js

@@ -38,14 +38,29 @@ const main = async () => {
 	const gatt = await adapter.setupGatt();
 	gatt.setData(NAME, [
 		{
-			uuid: '48ee0000bf49460ca3d77ec7a512a4cd',
+			uuid: '48ee0000bf49460ca3d77ec7a512a4ce',
 			characteristics: [
 				{
-					uuid: '48ee0001bf49460ca3d77ec7a512a4cd',
-					properties: ['read', 'write', 'write-without-response'],
+					uuid: '48ee0001bf49460ca3d77ec7a512a4ce',
+					properties: ['read'],
+					secure: [],
+					descriptors: [],
+					value: Buffer.from('test', 'utf-8')
+				},
+				{
+					uuid: '48ee0002bf49460ca3d77ec7a512a4ce',
+					properties: ['read'],
+					secure: [],
+					descriptors: [],
+					onRead: async (offset) => {
+						return [0, Buffer.from('other', 'utf-8').slice(offset)];
+					}
+				},
+				{
+					uuid: '48ee0003bf49460ca3d77ec7a512a4cd',
+					properties: ['write', 'write-without-response'],
 					secure: [],
 					descriptors: [],
-					value: Buffer.from('1337'),
 					onWrite: (offset, data, withoutResponse) => {
 						console.log('writing', offset, data, withoutResponse);
 					}

lib/models/gatt/local/Gatt.js.map

@@ -0,0 +1,52 @@
+var bleno = require('@abandonware/bleno');
+
+const ADVERTISING_NAME = 'modum.io Gateway';
+const SERVICE_ID = '48ee0000bf49460ca3d77ec7a512a4ce';
+const OVERVIEW_CHAR_ID = '48ee0001bf49460ca3d77ec7a512a4ce';
+const TEST_CHAR_ID = '48ee0002bf49460ca3d77ec7a512a4ce';
+
+bleno.on('stateChange', (state) => {
+	console.log('state', state);
+
+	bleno.setServices(
+		[
+			new bleno.PrimaryService({
+				uuid: SERVICE_ID,
+				characteristics: [
+					// Overview
+					new bleno.Characteristic({
+						uuid: OVERVIEW_CHAR_ID,
+						properties: ['read'],
+						secure: [],
+						descriptors: [],
+						onReadRequest: async (offset, callback) => {
+							callback(bleno.Characteristic.RESULT_SUCCESS, Buffer.from('test', 'utf-8').slice(offset));
+						}
+					}),
+					// Other
+					new bleno.Characteristic({
+						uuid: TEST_CHAR_ID,
+						properties: ['read'],
+						secure: [],
+						descriptors: [],
+						onReadRequest: async (offset, callback) => {
+							if (offset === 0) {
+								dataBuff = Buffer.from(data, 'utf-8');
+							}
+
+							callback(bleno.Characteristic.RESULT_SUCCESS, Buffer.from('other', 'utf-8').slice(offset));
+						}
+					})
+				]
+			})
+		],
+		(err) => console.log('services', err)
+	);
+
+	bleno.startAdvertising(ADVERTISING_NAME, [SERVICE_ID]);
+});
+bleno.on('advertisingStart', () => console.log('Advertising started'));
+bleno.on('advertisingStop', () => console.log('Advertising stopped'));
+bleno.on('accept', (clientAddress) => console.log('Connected', clientAddress));
+bleno.on('disconnect', (clientAddress) => console.log('Disonnected', clientAddress));
+bleno.on('error', (err) => console.error(err));