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Diffstat (limited to 'devtools/shared/discovery/discovery.js')
| -rw-r--r-- | devtools/shared/discovery/discovery.js | 427 |
1 files changed, 427 insertions, 0 deletions
diff --git a/devtools/shared/discovery/discovery.js b/devtools/shared/discovery/discovery.js new file mode 100644 index 0000000000..f7ec5a6860 --- /dev/null +++ b/devtools/shared/discovery/discovery.js @@ -0,0 +1,427 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ +"use strict"; + +/** + * This implements a UDP mulitcast device discovery protocol that: + * * Is optimized for mobile devices + * * Doesn't require any special schema for service info + * + * To ensure it works well on mobile devices, there is no heartbeat or other + * recurring transmission. + * + * Devices are typically in one of two groups: scanning for services or + * providing services (though they may be in both groups as well). + * + * Scanning devices listen on UPDATE_PORT for UDP multicast traffic. When the + * scanning device wants to force an update of the services available, it sends + * a status packet to SCAN_PORT. + * + * Service provider devices listen on SCAN_PORT for any packets from scanning + * devices. If one is recevied, the provider device sends a status packet + * (listing the services it offers) to UPDATE_PORT. + * + * Scanning devices purge any previously known devices after REPLY_TIMEOUT ms + * from that start of a scan if no reply is received during the most recent + * scan. + * + * When a service is registered, is supplies a regular object with any details + * about itself (a port number, for example) in a service-defined format, which + * is then available to scanning devices. + */ + +const EventEmitter = require("resource://devtools/shared/event-emitter.js"); + +const UDPSocket = Components.Constructor( + "@mozilla.org/network/udp-socket;1", + "nsIUDPSocket", + "init" +); + +const SCAN_PORT = 50624; +const UPDATE_PORT = 50625; +const ADDRESS = "224.0.0.115"; +const REPLY_TIMEOUT = 5000; + +var logging = Services.prefs.getBoolPref("devtools.discovery.log"); +function log(msg) { + if (logging) { + console.log("DISCOVERY: " + msg); + } +} + +/** + * Each Transport instance owns a single UDPSocket. + * @param port integer + * The port to listen on for incoming UDP multicast packets. + */ +function Transport(port) { + EventEmitter.decorate(this); + try { + this.socket = new UDPSocket( + port, + false, + Services.scriptSecurityManager.getSystemPrincipal() + ); + this.socket.joinMulticast(ADDRESS); + this.socket.asyncListen(this); + } catch (e) { + log("Failed to start new socket: " + e); + } +} + +Transport.prototype = { + /** + * Send a object to some UDP port. + * @param object object + * Object which is the message to send + * @param port integer + * UDP port to send the message to + */ + send(object, port) { + if (logging) { + log("Send to " + port + ":\n" + JSON.stringify(object, null, 2)); + } + const message = JSON.stringify(object); + const rawMessage = Uint8Array.from(message, x => x.charCodeAt(0)); + try { + this.socket.send(ADDRESS, port, rawMessage, rawMessage.length); + } catch (e) { + log("Failed to send message: " + e); + } + }, + + destroy() { + this.socket.close(); + }, + + // nsIUDPSocketListener + + onPacketReceived(socket, message) { + const messageData = message.data; + const object = JSON.parse(messageData); + object.from = message.fromAddr.address; + const port = message.fromAddr.port; + if (port == this.socket.port) { + log("Ignoring looped message"); + return; + } + if (logging) { + log( + "Recv on " + this.socket.port + ":\n" + JSON.stringify(object, null, 2) + ); + } + this.emit("message", object); + }, + + onStopListening() {}, +}; + +/** + * Manages the local device's name. The name can be generated in serveral + * platform-specific ways (see |_generate|). The aim is for each device on the + * same local network to have a unique name. + */ +function LocalDevice() { + this._name = LocalDevice.UNKNOWN; + // Trigger |_get| to load name eagerly + this._get(); +} + +LocalDevice.UNKNOWN = "unknown"; + +LocalDevice.prototype = { + _get() { + // Without Settings API, just generate a name and stop, since the value + // can't be persisted. + this._generate(); + }, + + /** + * Generate a new device name from various platform-specific properties. + * Triggers the |name| setter to persist if needed. + */ + _generate() { + if (Services.appinfo.widgetToolkit == "android") { + // For Firefox for Android, use the device's model name. + // TODO: Bug 1180997: Find the right way to expose an editable name + this.name = Services.sysinfo.get("device"); + } else { + this.name = Services.dns.myHostName; + } + }, + + get name() { + return this._name; + }, + + set name(name) { + this._name = name; + log("Device: " + this._name); + }, +}; + +function Discovery() { + EventEmitter.decorate(this); + + this.localServices = {}; + this.remoteServices = {}; + this.device = new LocalDevice(); + this.replyTimeout = REPLY_TIMEOUT; + + // Defaulted to Transport, but can be altered by tests + this._factories = { Transport }; + + this._transports = { + scan: null, + update: null, + }; + this._expectingReplies = { + from: new Set(), + }; + + this._onRemoteScan = this._onRemoteScan.bind(this); + this._onRemoteUpdate = this._onRemoteUpdate.bind(this); + this._purgeMissingDevices = this._purgeMissingDevices.bind(this); +} + +Discovery.prototype = { + /** + * Add a new service offered by this device. + * @param service string + * Name of the service + * @param info object + * Arbitrary data about the service to announce to scanning devices + */ + addService(service, info) { + log("ADDING LOCAL SERVICE"); + if (Object.keys(this.localServices).length === 0) { + this._startListeningForScan(); + } + this.localServices[service] = info; + }, + + /** + * Remove a service offered by this device. + * @param service string + * Name of the service + */ + removeService(service) { + delete this.localServices[service]; + if (Object.keys(this.localServices).length === 0) { + this._stopListeningForScan(); + } + }, + + /** + * Scan for service updates from other devices. + */ + scan() { + this._startListeningForUpdate(); + this._waitForReplies(); + // TODO Bug 1027457: Use timer to debounce + this._sendStatusTo(SCAN_PORT); + }, + + /** + * Get a list of all remote devices currently offering some service.:w + */ + getRemoteDevices() { + const devices = new Set(); + for (const service in this.remoteServices) { + for (const device in this.remoteServices[service]) { + devices.add(device); + } + } + return [...devices]; + }, + + /** + * Get a list of all remote devices currently offering a particular service. + */ + getRemoteDevicesWithService(service) { + const devicesWithService = this.remoteServices[service] || {}; + return Object.keys(devicesWithService); + }, + + /** + * Get service info (any details registered by the remote device) for a given + * service on a device. + */ + getRemoteService(service, device) { + const devicesWithService = this.remoteServices[service] || {}; + return devicesWithService[device]; + }, + + _waitForReplies() { + clearTimeout(this._expectingReplies.timer); + this._expectingReplies.from = new Set(this.getRemoteDevices()); + this._expectingReplies.timer = setTimeout( + this._purgeMissingDevices, + this.replyTimeout + ); + }, + + get Transport() { + return this._factories.Transport; + }, + + _startListeningForScan() { + if (this._transports.scan) { + // Already listening + return; + } + log("LISTEN FOR SCAN"); + this._transports.scan = new this.Transport(SCAN_PORT); + this._transports.scan.on("message", this._onRemoteScan); + }, + + _stopListeningForScan() { + if (!this._transports.scan) { + // Not listening + return; + } + this._transports.scan.off("message", this._onRemoteScan); + this._transports.scan.destroy(); + this._transports.scan = null; + }, + + _startListeningForUpdate() { + if (this._transports.update) { + // Already listening + return; + } + log("LISTEN FOR UPDATE"); + this._transports.update = new this.Transport(UPDATE_PORT); + this._transports.update.on("message", this._onRemoteUpdate); + }, + + _stopListeningForUpdate() { + if (!this._transports.update) { + // Not listening + return; + } + this._transports.update.off("message", this._onRemoteUpdate); + this._transports.update.destroy(); + this._transports.update = null; + }, + + _restartListening() { + if (this._transports.scan) { + this._stopListeningForScan(); + this._startListeningForScan(); + } + if (this._transports.update) { + this._stopListeningForUpdate(); + this._startListeningForUpdate(); + } + }, + + /** + * When sending message, we can use either transport, so just pick the first + * one currently alive. + */ + get _outgoingTransport() { + if (this._transports.scan) { + return this._transports.scan; + } + if (this._transports.update) { + return this._transports.update; + } + return null; + }, + + _sendStatusTo(port) { + const status = { + device: this.device.name, + services: this.localServices, + }; + this._outgoingTransport.send(status, port); + }, + + _onRemoteScan() { + // Send my own status in response + log("GOT SCAN REQUEST"); + this._sendStatusTo(UPDATE_PORT); + }, + + _onRemoteUpdate(update) { + log("GOT REMOTE UPDATE"); + + const remoteDevice = update.device; + const remoteHost = update.from; + + // Record the reply as received so it won't be purged as missing + this._expectingReplies.from.delete(remoteDevice); + + // First, loop over the known services + for (const service in this.remoteServices) { + const devicesWithService = this.remoteServices[service]; + const hadServiceForDevice = !!devicesWithService[remoteDevice]; + const haveServiceForDevice = service in update.services; + // If the remote device used to have service, but doesn't any longer, then + // it was deleted, so we remove it here. + if (hadServiceForDevice && !haveServiceForDevice) { + delete devicesWithService[remoteDevice]; + log("REMOVED " + service + ", DEVICE " + remoteDevice); + this.emit(service + "-device-removed", remoteDevice); + } + } + + // Second, loop over the services in the received update + for (const service in update.services) { + // Detect if this is a new device for this service + const newDevice = + !this.remoteServices[service] || + !this.remoteServices[service][remoteDevice]; + + // Look up the service info we may have received previously from the same + // remote device + const devicesWithService = this.remoteServices[service] || {}; + const oldDeviceInfo = devicesWithService[remoteDevice]; + + // Store the service info from the remote device + const newDeviceInfo = Cu.cloneInto(update.services[service], {}); + newDeviceInfo.host = remoteHost; + devicesWithService[remoteDevice] = newDeviceInfo; + this.remoteServices[service] = devicesWithService; + + // If this is a new service for the remote device, announce the addition + if (newDevice) { + log("ADDED " + service + ", DEVICE " + remoteDevice); + this.emit(service + "-device-added", remoteDevice, newDeviceInfo); + } + + // If we've seen this service from the remote device, but the details have + // changed, announce the update + if ( + !newDevice && + JSON.stringify(oldDeviceInfo) != JSON.stringify(newDeviceInfo) + ) { + log("UPDATED " + service + ", DEVICE " + remoteDevice); + this.emit(service + "-device-updated", remoteDevice, newDeviceInfo); + } + } + }, + + _purgeMissingDevices() { + log("PURGING MISSING DEVICES"); + for (const service in this.remoteServices) { + const devicesWithService = this.remoteServices[service]; + for (const remoteDevice in devicesWithService) { + // If we're still expecting a reply from a remote device when it's time + // to purge, then the service is removed. + if (this._expectingReplies.from.has(remoteDevice)) { + delete devicesWithService[remoteDevice]; + log("REMOVED " + service + ", DEVICE " + remoteDevice); + this.emit(service + "-device-removed", remoteDevice); + } + } + } + }, +}; + +var discovery = new Discovery(); + +module.exports = discovery; |