1 files changed, 496 insertions, 0 deletions
diff --git a/devtools/shared/discovery/discovery.js b/devtools/shared/discovery/discovery.js
new file mode 100644
index 000000000..d0b49f129
--- /dev/null
+++ b/devtools/shared/discovery/discovery.js
@@ -0,0 +1,496 @@
+/* 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 { Cu, CC, Cc, Ci } = require("chrome");
+const EventEmitter = require("devtools/shared/event-emitter");
+const Services = require("Services");
+
+const UDPSocket = CC("@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;
+
+const { XPCOMUtils } = Cu.import("resource://gre/modules/XPCOMUtils.jsm", {});
+
+XPCOMUtils.defineLazyGetter(this, "converter", () => {
+  let conv = Cc["@mozilla.org/intl/scriptableunicodeconverter"].
+             createInstance(Ci.nsIScriptableUnicodeConverter);
+  conv.charset = "utf8";
+  return conv;
+});
+
+XPCOMUtils.defineLazyGetter(this, "sysInfo", () => {
+  return Cc["@mozilla.org/system-info;1"].getService(Ci.nsIPropertyBag2);
+});
+
+XPCOMUtils.defineLazyGetter(this, "libcutils", function () {
+  let { libcutils } = Cu.import("resource://gre/modules/systemlibs.js", {});
+  return libcutils;
+});
+
+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: function (object, port) {
+    if (logging) {
+      log("Send to " + port + ":\n" + JSON.stringify(object, null, 2));
+    }
+    let message = JSON.stringify(object);
+    let rawMessage = converter.convertToByteArray(message);
+    try {
+      this.socket.send(ADDRESS, port, rawMessage, rawMessage.length);
+    } catch (e) {
+      log("Failed to send message: " + e);
+    }
+  },
+
+  destroy: function () {
+    this.socket.close();
+  },
+
+  // nsIUDPSocketListener
+
+  onPacketReceived: function (socket, message) {
+    let messageData = message.data;
+    let object = JSON.parse(messageData);
+    object.from = message.fromAddr.address;
+    let 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: function () {}
+
+};
+
+/**
+ * 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.  If the Settings API is available,
+ * the name is saved there to persist across reboots.
+ */
+function LocalDevice() {
+  this._name = LocalDevice.UNKNOWN;
+  if ("@mozilla.org/settingsService;1" in Cc) {
+    this._settings =
+      Cc["@mozilla.org/settingsService;1"].getService(Ci.nsISettingsService);
+    Services.obs.addObserver(this, "mozsettings-changed", false);
+  }
+  this._get(); // Trigger |_get| to load name eagerly
+}
+
+LocalDevice.SETTING = "devtools.discovery.device";
+LocalDevice.UNKNOWN = "unknown";
+
+LocalDevice.prototype = {
+
+  _get: function () {
+    if (!this._settings) {
+      // Without Settings API, just generate a name and stop, since the value
+      // can't be persisted.
+      this._generate();
+      return;
+    }
+    // Initial read of setting value
+    this._settings.createLock().get(LocalDevice.SETTING, {
+      handle: (_, name) => {
+        if (name && name !== LocalDevice.UNKNOWN) {
+          this._name = name;
+          log("Device: " + this._name);
+          return;
+        }
+        // No existing name saved, so generate one.
+        this._generate();
+      },
+      handleError: () => log("Failed to get device name setting")
+    });
+  },
+
+  /**
+   * Generate a new device name from various platform-specific properties.
+   * Triggers the |name| setter to persist if needed.
+   */
+  _generate: function () {
+    if (Services.appinfo.widgetToolkit == "gonk") {
+      // For Firefox OS devices, create one from the device name plus a little
+      // randomness.  The goal is just to distinguish devices in an office
+      // environment where many people may have the same device model for
+      // testing purposes (which would otherwise all report the same name).
+      let name = libcutils.property_get("ro.product.device");
+      // Pick a random number from [0, 2^32)
+      let randomID = Math.floor(Math.random() * Math.pow(2, 32));
+      // To hex and zero pad
+      randomID = ("00000000" + randomID.toString(16)).slice(-8);
+      this.name = name + "-" + randomID;
+    } else 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 = sysInfo.get("device");
+    } else {
+      this.name = sysInfo.get("host");
+    }
+  },
+
+  /**
+   * Observe any changes that might be made via the Settings app
+   */
+  observe: function (subject, topic, data) {
+    if (topic !== "mozsettings-changed") {
+      return;
+    }
+    if ("wrappedJSObject" in subject) {
+      subject = subject.wrappedJSObject;
+    }
+    if (subject.key !== LocalDevice.SETTING) {
+      return;
+    }
+    this._name = subject.value;
+    log("Device: " + this._name);
+  },
+
+  get name() {
+    return this._name;
+  },
+
+  set name(name) {
+    if (!this._settings) {
+      this._name = name;
+      log("Device: " + this._name);
+      return;
+    }
+    // Persist to Settings API
+    // The new value will be seen and stored by the observer above
+    this._settings.createLock().set(LocalDevice.SETTING, name, {
+      handle: () => {},
+      handleError: () => log("Failed to set device name setting")
+    });
+  }
+
+};
+
+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: 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: function (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: function (service) {
+    delete this.localServices[service];
+    if (Object.keys(this.localServices).length === 0) {
+      this._stopListeningForScan();
+    }
+  },
+
+  /**
+   * Scan for service updates from other devices.
+   */
+  scan: function () {
+    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: function () {
+    let devices = new Set();
+    for (let service in this.remoteServices) {
+      for (let device in this.remoteServices[service]) {
+        devices.add(device);
+      }
+    }
+    return [...devices];
+  },
+
+  /**
+   * Get a list of all remote devices currently offering a particular service.
+   */
+  getRemoteDevicesWithService: function (service) {
+    let 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: function (service, device) {
+    let devicesWithService = this.remoteServices[service] || {};
+    return devicesWithService[device];
+  },
+
+  _waitForReplies: function () {
+    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: function () {
+    if (this._transports.scan) {
+      return; // Already listening
+    }
+    log("LISTEN FOR SCAN");
+    this._transports.scan = new this.Transport(SCAN_PORT);
+    this._transports.scan.on("message", this._onRemoteScan);
+  },
+
+  _stopListeningForScan: function () {
+    if (!this._transports.scan) {
+      return; // Not listening
+    }
+    this._transports.scan.off("message", this._onRemoteScan);
+    this._transports.scan.destroy();
+    this._transports.scan = null;
+  },
+
+  _startListeningForUpdate: function () {
+    if (this._transports.update) {
+      return; // Already listening
+    }
+    log("LISTEN FOR UPDATE");
+    this._transports.update = new this.Transport(UPDATE_PORT);
+    this._transports.update.on("message", this._onRemoteUpdate);
+  },
+
+  _stopListeningForUpdate: function () {
+    if (!this._transports.update) {
+      return; // Not listening
+    }
+    this._transports.update.off("message", this._onRemoteUpdate);
+    this._transports.update.destroy();
+    this._transports.update = null;
+  },
+
+  _restartListening: function () {
+    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: function (port) {
+    let status = {
+      device: this.device.name,
+      services: this.localServices
+    };
+    this._outgoingTransport.send(status, port);
+  },
+
+  _onRemoteScan: function () {
+    // Send my own status in response
+    log("GOT SCAN REQUEST");
+    this._sendStatusTo(UPDATE_PORT);
+  },
+
+  _onRemoteUpdate: function (e, update) {
+    log("GOT REMOTE UPDATE");
+
+    let remoteDevice = update.device;
+    let 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 (let service in this.remoteServices) {
+      let devicesWithService = this.remoteServices[service];
+      let hadServiceForDevice = !!devicesWithService[remoteDevice];
+      let 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 (let service in update.services) {
+      // Detect if this is a new device for this service
+      let newDevice = !this.remoteServices[service] ||
+                      !this.remoteServices[service][remoteDevice];
+
+      // Look up the service info we may have received previously from the same
+      // remote device
+      let devicesWithService = this.remoteServices[service] || {};
+      let oldDeviceInfo = devicesWithService[remoteDevice];
+
+      // Store the service info from the remote device
+      let 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: function () {
+    log("PURGING MISSING DEVICES");
+    for (let service in this.remoteServices) {
+      let devicesWithService = this.remoteServices[service];
+      for (let 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;