gecko-dev/remote/RemoteAgent.jsm

/* 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";

var EXPORTED_SYMBOLS = ["RemoteAgent", "RemoteAgentFactory"];

const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
const { XPCOMUtils } = ChromeUtils.import(
  "resource://gre/modules/XPCOMUtils.jsm"
);

XPCOMUtils.defineLazyModuleGetters(this, {
  HttpServer: "chrome://remote/content/server/HTTPD.jsm",
  JSONHandler: "chrome://remote/content/JSONHandler.jsm",
  Log: "chrome://remote/content/Log.jsm",
  Preferences: "resource://gre/modules/Preferences.jsm",
  RecommendedPreferences: "chrome://remote/content/RecommendedPreferences.jsm",
  Targets: "chrome://remote/content/targets/Targets.jsm",
});
XPCOMUtils.defineLazyGetter(this, "log", Log.get);

const ENABLED = "remote.enabled";
const FORCE_LOCAL = "remote.force-local";

const LOOPBACKS = ["localhost", "127.0.0.1", "[::1]"];

class RemoteAgentClass {
  get listening() {
    return !!this.server && !this.server.isStopped();
  }

  async listen(url) {
    if (!Preferences.get(ENABLED, false)) {
      throw new Error("Remote agent is disabled by preference");
    }
    if (Services.appinfo.processType != Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT) {
      throw new Error(
        "Remote agent can only be instantiated from the parent process"
      );
    }

    if (!(url instanceof Ci.nsIURI)) {
      url = Services.io.newURI(url);
    }

    let { host, port } = url;
    if (Preferences.get(FORCE_LOCAL) && !LOOPBACKS.includes(host)) {
      throw new Error("Restricted to loopback devices");
    }

    // nsIServerSocket uses -1 for atomic port allocation
    if (port === 0) {
      port = -1;
    }

    if (this.listening) {
      return;
    }

    Preferences.set(RecommendedPreferences);

    this.server = new HttpServer();
    this.server.registerPrefixHandler("/json/", new JSONHandler(this));

    this.targets = new Targets();
    this.targets.on("target-created", (eventName, target) => {
      if (!target.path) {
        throw new Error(`Target is missing 'path' attribute: ${target}`);
      }
      this.server.registerPathHandler(target.path, target);
    });
    this.targets.on("target-destroyed", (eventName, target) => {
      // TODO: removes the entry added by registerPathHandler,
      // but we should instead have nsIHttpServer.unregisterPathHandler
      delete this.server._handler._overridePaths[target.path];
    });

    try {
      await this.targets.watchForTargets();

      // Immediatly instantiate the main process target in order
      // to be accessible via HTTP endpoint on startup
      const mainTarget = this.targets.getMainProcessTarget();

      this.server._start(port, host);
      Services.obs.notifyObservers(
        null,
        "remote-listening",
        mainTarget.wsDebuggerURL
      );
    } catch (e) {
      await this.close();
      throw new Error(`Unable to start remote agent: ${e.message}`, e);
    }
  }

  async close() {
    try {
      // if called early at startup, preferences may not be available
      try {
        Preferences.reset(Object.keys(RecommendedPreferences));
      } catch (e) {}

      // destroy targets before stopping server,
      // otherwise the HTTP will fail to stop
      if (this.targets) {
        this.targets.destructor();
      }

      if (this.listening) {
        await this.server.stop();
      }
    } catch (e) {
      // this function must never fail
      log.error("unable to stop listener", e);
    } finally {
      this.server = null;
      this.targets = null;
    }
  }

  get scheme() {
    if (!this.server) {
      return null;
    }
    return this.server.identity.primaryScheme;
  }

  get host() {
    if (!this.server) {
      return null;
    }
    return this.server.identity.primaryHost;
  }

  get port() {
    if (!this.server) {
      return null;
    }
    return this.server.identity.primaryPort;
  }

  // XPCOM

  get QueryInterface() {
    return ChromeUtils.generateQI([Ci.nsIRemoteAgent]);
  }
}

var RemoteAgent = new RemoteAgentClass();

// This is used by the XPCOM codepath which expects a constructor
var RemoteAgentFactory = function() {
  return RemoteAgent;
};