Fast-fail WPAD detection.

net/proxy/proxy_script_decider.h

 // Copyright (c) 2012 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 NET_PROXY_PROXY_SCRIPT_DECIDER_H_
 #define NET_PROXY_PROXY_SCRIPT_DECIDER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
+#include "net/base/address_list.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_export.h"
 #include "net/base/net_log.h"
+#include "net/dns/host_resolver.h"
 #include "net/proxy/proxy_config.h"
 #include "net/proxy/proxy_resolver.h"
 #include "url/gurl.h"
 
 namespace net {
 
 class DhcpProxyScriptFetcher;
 class NetLogParameter;
 class ProxyResolver;
 class ProxyScriptFetcher;
@@ skipping 68 matching lines @@
                                 NetLog::LogLevel log_level) const;
 
     Type type;
     GURL url;  // Empty unless |type == PAC_SOURCE_CUSTOM|.
   };
 
   typedef std::vector<PacSource> PacSourceList;
 
   enum State {
     STATE_NONE,
+    STATE_QUICK_CHECK,
+    STATE_QUICK_CHECK_COMPLETE,
     STATE_WAIT,
     STATE_WAIT_COMPLETE,
     STATE_FETCH_PAC_SCRIPT,
     STATE_FETCH_PAC_SCRIPT_COMPLETE,
     STATE_VERIFY_PAC_SCRIPT,
     STATE_VERIFY_PAC_SCRIPT_COMPLETE,
+    STATE_FAILED,
   };
 
   // Returns ordered list of PAC urls to try for |config|.
   PacSourceList BuildPacSourcesFallbackList(const ProxyConfig& config) const;
 
   void OnIOCompletion(int result);
   int DoLoop(int result);
   void DoCallback(int result);
 
+  int DoQuickCheck();
+  int DoQuickCheckComplete();
+  void OnQuickCheckComplete(int result);
+
   int DoWait();
   int DoWaitComplete(int result);
 
   int DoFetchPacScript();
   int DoFetchPacScriptComplete(int result);
 
   int DoVerifyPacScript();
   int DoVerifyPacScriptComplete(int result);
 
   // Tries restarting using the next fallback PAC URL:
   // |pac_sources_[++current_pac_source_index]|.
   // Returns OK and rewinds the state machine when there
   // is something to try, otherwise returns |error|.
   int TryToFallbackPacSource(int error);
 
   // Gets the initial state (we skip fetching when the
   // ProxyResolver doesn't |expect_pac_bytes()|.
   State GetStartState() const;
 
   void DetermineURL(const PacSource& pac_source, GURL* effective_pac_url);
 
   // Returns the current PAC URL we are fetching/testing.
   const PacSource& current_pac_source() const;
 
+  void OnQuickCheckTimerFired();
   void OnWaitTimerFired();
   void DidComplete();
   void Cancel();
 
   ProxyResolver* resolver_;
   ProxyScriptFetcher* proxy_script_fetcher_;
   DhcpProxyScriptFetcher* dhcp_proxy_script_fetcher_;
 
   net::CompletionCallback callback_;
 
@@ skipping 13 matching lines @@
 
   bool fetch_pac_bytes_;
 
   base::TimeDelta wait_delay_;
   base::OneShotTimer<ProxyScriptDecider> wait_timer_;
 
   // Results.
   ProxyConfig effective_config_;
   scoped_refptr<ProxyResolverScriptData> script_data_;
 
+  scoped_ptr<HostResolver> host_resolver_;
+  AddressList wpad_addrs_;
+  HostResolver::RequestHandle wpad_req_;
+  base::TimeDelta quick_check_delay_;

[szym, 2013/08/21 19:11:21]

Do you anticipate changing this value? If not, declare const int
kQuickCheckDelaySeconds in an anonymous namespace (in .cc) and construct
TimeDelta where you need it.

+  base::OneShotTimer<ProxyScriptDecider> quick_check_timer_;
+  base::Time quick_check_started_;

[szym, 2013/08/21 19:11:21]

Instead of storing it here, bind it into the Callback passed to the
|quick_check_timer_|.

[szym, 2013/08/21 19:21:09]

Both the timer and HostResolver::Request.

CompletionCallback callback = base::Bind(&...::OnQuickCheckComplete,
base::Unretained(this), base::Time::Now());

Resolve(..., callback);

timer_.Start(FROM_HERE, delay, base::Bind(callback, ERR_NAME_NOT_RESOLVED));

...::OnQuickCheckComplete(base::Time start_time, int result) {
  // compute TimeDelta, UMA result, OnIOComplete(result)
}

For this to work timer_ needs to be base::Timer(false, false).

 
   DISALLOW_COPY_AND_ASSIGN(ProxyScriptDecider);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_SCRIPT_DECIDER_H_