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      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 
     18 namespace net {
     19 class DnsClient;
     20 struct DnsConfig;
     21 }
     22 
     23 namespace 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.
     30 class 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