1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_NET_DNS_PROBE_SERVICE_H_
6#define CHROME_BROWSER_NET_DNS_PROBE_SERVICE_H_
7
8#include <vector>
9
10#include "base/basictypes.h"
11#include "base/bind.h"
12#include "base/memory/scoped_ptr.h"
13#include "base/time/time.h"
14#include "chrome/browser/net/dns_probe_runner.h"
15#include "chrome/common/net/net_error_info.h"
16#include "net/base/network_change_notifier.h"
17
18namespace net {
19class DnsClient;
20struct DnsConfig;
21}
22
23namespace chrome_browser_net {
24
25// Probes the system and public DNS servers to determine the (probable) cause
26// of a recent DNS-related page load error.  Coalesces multiple probe requests
27// (perhaps from multiple tabs) and caches the results.
28//
29// Uses a single DNS attempt per config, and doesn't randomize source ports.
30class DnsProbeService : public net::NetworkChangeNotifier::DNSObserver {
31 public:
32  typedef base::Callback<void(chrome_common_net::DnsProbeStatus result)>
33      ProbeCallback;
34
35  DnsProbeService();
36  virtual ~DnsProbeService();
37
38  virtual void ProbeDns(const ProbeCallback& callback);
39
40  // NetworkChangeNotifier::DNSObserver implementation:
41  virtual void OnDNSChanged() OVERRIDE;
42
43  void SetSystemClientForTesting(scoped_ptr<net::DnsClient> system_client);
44  void SetPublicClientForTesting(scoped_ptr<net::DnsClient> public_client);
45  void ClearCachedResultForTesting();
46
47 private:
48  enum State {
49    STATE_NO_RESULT,
50    STATE_PROBE_RUNNING,
51    STATE_RESULT_CACHED,
52  };
53
54  void SetSystemClientToCurrentConfig();
55  void SetPublicClientToGooglePublicDns();
56
57  // Starts a probe (runs system and public probes).
58  void StartProbes();
59  void OnProbeComplete();
60  // Calls all |pending_callbacks_| with the |cached_result_|.
61  void CallCallbacks();
62  // Clears a cached probe result.
63  void ClearCachedResult();
64
65  bool CachedResultIsExpired() const;
66
67  State state_;
68  std::vector<ProbeCallback> pending_callbacks_;
69  base::Time probe_start_time_;
70  chrome_common_net::DnsProbeStatus cached_result_;
71
72  // DnsProbeRunners for the system DNS configuration and a public DNS server.
73  DnsProbeRunner system_runner_;
74  DnsProbeRunner public_runner_;
75
76  DISALLOW_COPY_AND_ASSIGN(DnsProbeService);
77};
78
79}  // namespace chrome_browser_net
80
81#endif  // CHROME_BROWSER_NET_DNS_PROBE_SERVICE_H_
82