Add DiscoveryNetworkMonitor implementation

chrome/browser/media/router/discovery/discovery_network_monitor.h

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DISCOVERY_NETWORK_MONITOR_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DISCOVERY_NETWORK_MONITOR_H_
+
+#include <string>
+#include <vector>
+
+#include "base/bind.h"
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "base/observer_list_threadsafe.h"
+#include "base/synchronization/lock.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/base/ip_address.h"
+#include "net/base/network_change_notifier.h"
+
+// Represents a single network interface that can be used for discovery.

[mark a. foltz, 2017/05/04 23:16:44]

...for local discovery

[btolsch, 2017/05/23 08:55:03]

Done.

+struct NetworkInfo {
+ public:
+  NetworkInfo();
+  NetworkInfo(uint32_t index,
+              net::NetworkChangeNotifier::ConnectionType connection_type,
+              std::string name,
+              std::string network_id);
+  ~NetworkInfo() = default;
+
+  NetworkInfo(const NetworkInfo&);
+  NetworkInfo& operator=(const NetworkInfo&);
+
+  bool operator==(const NetworkInfo&) const;
+  bool operator!=(const NetworkInfo&) const;
+
+  // The index of the network interface.
+  uint32_t index = 0;
+  // The connection type.  Must be CONNECTION_ETHERNET or CONNECTION_WIFI.
+  net::NetworkChangeNotifier::ConnectionType connection_type =
+      net::NetworkChangeNotifier::ConnectionType::CONNECTION_UNKNOWN;
+  // The name of the network interface.
+  std::string name;
+  // A unique identifier for the network interface.

[mark a. foltz, 2017/05/04 23:16:43]

network interface and its connected network.

[btolsch, 2017/05/23 08:55:03]

Done.

+  // For WiFi networks, this is the SSID.
+  // For Ethernet networks, this is the MAC address.
+  std::string network_id;
+};
+
+// Tracks the set of active network interfaces that can be used for local
+// discovery.  If the list of interfaces changes, then
+// DiscoveryNetworkMonitor::Observer is called with the instance of the manager.

[mark a. foltz, 2017/05/04 23:16:44]

s/manager/monitor/ here and elsewhere

[btolsch, 2017/05/23 08:55:03]

Done.

+// Only one instance of this should be created per browser process.

[mark a. foltz, 2017/05/04 23:16:44]

Please document threading assumptions for this class.

[btolsch, 2017/05/23 08:55:03]

Done.

+class DiscoveryNetworkMonitor
+    : public net::NetworkChangeNotifier::NetworkChangeObserver {
+ public:
+  using NetworkInfoCallback = base::Callback<std::vector<NetworkInfo>()>;
+  using NetworkRefreshCompleteCallback = base::Callback<void()>;
+  class Observer {
+   public:
+    // Called when the list of connected interfaces has changed.
+    virtual void OnNetworksChanged(const DiscoveryNetworkMonitor& manager) = 0;
+
+   protected:
+    ~Observer() = default;
+  };
+
+  static DiscoveryNetworkMonitor* GetInstance();
+  static DiscoveryNetworkMonitor* GetInstanceForTest(NetworkInfoCallback);
+
+  void RebindNetworkChangeObserverForTest();
+
+  void AddObserver(Observer* const observer);
+  void RemoveObserver(Observer* const observer);
+
+  // Forces a query of the network state to recompute |network_id_| and
+  // |networks_|.  |callback| will be called after the refresh.

[mark a. foltz, 2017/05/04 23:16:43]

Is the point to trigger OnNetworksChanged if there has been a change in the set
of connected networks?  Updating the internal state is an implementation detail.

[btolsch, 2017/05/23 08:55:03]

The internal state update and observer calls could happen as a result of this
call, but the point is really to have a polling-type interface for the
chrome.dial API (no longer part of this patch, but will probably be added
later).  I updated the comment but I could also remove this until the
chrome.dial API is added.

+  void Refresh(NetworkRefreshCompleteCallback callback);
+
+  // Computes a stable string identifier from the list of connected interfaces.
+  // Returns "disconnected" if there are no connected interfaces or "unknown" if

[mark a. foltz, 2017/05/04 23:16:43]

s/"disconnected"/kNetworkIdDisconnected/ etc

[btolsch, 2017/05/23 08:55:03]

Done.

+  // the identifier could not be computed.
+  const std::string GetNetworkId() const {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+    return network_id_;

[mark a. foltz, 2017/05/04 23:16:43]

I think the DCHECK() disqualifies this from inlining, but I don't feel strongly.

[btolsch, 2017/05/23 08:55:03]

Done.

+  }
+
+  // net::NetworkChangeNotifier::NetworkChangeObserver
+  void OnNetworkChanged(
+      net::NetworkChangeNotifier::ConnectionType type) override;

[mark a. foltz, 2017/05/04 23:16:42]

Can this be private?

[btolsch, 2017/05/23 08:55:03]

Done.

+
+  // Constants for the special states of network Id.
+  static const char kNetworkIdDisconnected[];
+  static const char kNetworkIdUnknown[];
+
+ private:
+  friend struct base::LazyInstanceTraitsBase<DiscoveryNetworkMonitor>;
+
+  DiscoveryNetworkMonitor();
+  ~DiscoveryNetworkMonitor() override;
+
+  std::string ComputeNetworkId(
+      const std::vector<NetworkInfo>& network_info_list);
+  void UpdateNetworkInfo(const NetworkRefreshCompleteCallback& callback);
+
+  std::string network_id_;
+  std::vector<NetworkInfo> networks_;
+  scoped_refptr<base::ObserverListThreadSafe<Observer>> observers_;
+  NetworkInfoCallback network_info_callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(DiscoveryNetworkMonitor);
+};
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DISCOVERY_NETWORK_MONITOR_H_