Adds support for the DHCP portion of the WPAD (proxy auto-discovery) protocol.

net/proxy/dhcp_proxy_script_fetcher_win.h

Index: net/proxy/dhcp_proxy_script_fetcher_win.h
diff --git a/net/proxy/dhcp_proxy_script_fetcher_win.h b/net/proxy/dhcp_proxy_script_fetcher_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..b8261495df25da6bd3a53af4175578b578ca146a
--- /dev/null
+++ b/net/proxy/dhcp_proxy_script_fetcher_win.h
@@ -0,0 +1,127 @@
+// Copyright (c) 2011 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_DHCP_PROXY_SCRIPT_FETCHER_WIN_H_
+#define NET_PROXY_DHCP_PROXY_SCRIPT_FETCHER_WIN_H_
+#pragma once
+
+#include <list>
+#include <set>
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/timer.h"
+#include "net/proxy/dhcp_proxy_script_fetcher.h"
+
+namespace net {
+
+class DhcpProxyScriptAdapterFetcher;
+class URLRequestContext;
+
+// Windows-specific implementation.
+class WindowsDhcpProxyScriptFetcher
+    : public DhcpProxyScriptFetcher,
+      public base::NonThreadSafe {
+ public:
+  // Creates a WindowsDhcpProxyScriptFetcher that issues requests through
+  // |url_request_context|. |url_request_context| must remain valid for
+  // the lifetime of WindowsDhcpProxyScriptFetcher.
+  explicit WindowsDhcpProxyScriptFetcher(
+      URLRequestContext* url_request_context);
+  virtual ~WindowsDhcpProxyScriptFetcher();
+
+  // DhcpProxyScriptFetcher implementation.
+  int Fetch(string16* utf16_text, CompletionCallback* callback) OVERRIDE;
+  void Cancel() OVERRIDE;
+  URLRequestContext* GetRequestContext() const OVERRIDE;
+  GURL GetPacURL() const OVERRIDE;
+  std::string GetFetcherName() const OVERRIDE;
+
+  // Sets |adapter_names| to contain the name of each network adapter on
+  // this machine that has DHCP enabled and is not a loop-back adapter. Returns
+  // false on error.
+  static bool GetCandidateAdapterNames(std::set<std::string>* adapter_names);
+
+ protected:
+  // Event/state transition handlers
+  void CancelImpl(bool clear_fetchers);
+  void OnFetcherDone(int result);
+  void OnWaitTimer();
+  void TransitionToDone();
+
+  // Virtual methods introduced to allow unit testing.
+  virtual DhcpProxyScriptAdapterFetcher* ImplCreateAdapterFetcher();
+  virtual bool ImplGetCandidateAdapterNames(
+      std::set<std::string>* adapter_names);
+  virtual int ImplGetMaxWaitMs();
+
+  // This is the outer state machine for fetching PAC configuration from
+  // DHCP.  It relies for sub-states on the state machine of the
+  // DhcpProxyScriptAdapterFetcher class.
+  //
+  // The goal of the implementation is to the following work in parallel
+  // for all network adapters that are using DHCP:
+  // a) Try to get the PAC URL configured in DHCP;
+  // b) If one is configured, try to fetch the PAC URL.
+  // c) Once this is done for all adapters, or a timeout has passed after
+  //    it has completed for the fastest adapter, return the PAC file
+  //    available for the most preferred network adapter, if any.
+  //
+  // The state machine goes from START->NO_RESULTS when it creates
+  // and starts an DhcpProxyScriptAdapterFetcher for each adapter.  It goes
+  // from NO_RESULTS->SOME_RESULTS when it gets the first result; at this
+  // point a wait timer is started.  It goes from SOME_RESULTS->DONE in
+  // two cases: All results are known, or the wait timer expired.  A call
+  // to Cancel() will also go straight to DONE from any state.  Any
+  // way the DONE state is entered, we will at that point cancel any
+  // outstanding work and return the best known PAC script or the empty
+  // string.
+  //
+  // The state machine is reset for each Fetch(), a call to which is
+  // only valid in states START and DONE, as only one Fetch() is
+  // allowed to be outstanding at any given time.
+  enum State {
+    STATE_START,
+    STATE_NO_RESULTS,
+    STATE_SOME_RESULTS,
+    STATE_DONE,
+  };
+
+  // Current state of this state machine.
+  State state_;
+
+  // List, in Windows' network adapter preference order, of
+  // DhcpProxyScriptAdapterFetcher objects that are or were attempting
+  // to fetch a PAC file based on DHCP configuration.
+  typedef std::list<scoped_refptr<DhcpProxyScriptAdapterFetcher>> FetcherList;

[eroman, 2011/05/13 05:03:32]

sorta surprised this works, i remember having issues with >> being tokenized as
a stream operator in the past.

[Jói, 2011/05/13 20:19:09]

I think it used to be an issue on VS 2005, and I guess we may still want to be
compatible with that so I've added a space.

+  FetcherList fetchers_;
+
+  // Callback invoked when any fetcher completes.
+  CompletionCallbackImpl<WindowsDhcpProxyScriptFetcher> fetcher_callback_;
+
+  // Number of fetchers we are waiting for.
+  int num_pending_fetchers_;
+
+  // Lets our client know we're done. Not valid in states START or DONE.
+  CompletionCallback* client_callback_;
+
+  // Pointer to string we will write results to. Not valid in states
+  // START and DONE.
+  string16* destination_string_;
+
+  // PAC URL retrieved from DHCP, if any. Valid only in state STATE_DONE.
+  GURL pac_url_;
+
+  base::OneShotTimer<WindowsDhcpProxyScriptFetcher> wait_timer_;
+
+  URLRequestContext* url_request_context_;

[eroman, 2011/05/13 05:03:32]

No hold reference?

[Jói, 2011/05/13 20:19:09]

Done.

+
+  friend class WindowsDhcpProxyScriptFetcherTestFriend;

[eroman, 2011/05/13 05:03:32]

Please use FRIEND_TEST

[Jói, 2011/05/13 20:19:09]

This wasn't even being used any more so I've removed it.  Thanks for taking
issue with it :)

I would posit though, that it should be fine to use this instead of FRIEND_TEST
in certain cases, perhaps with improved naming (start with TestFriend instead of
end with TestFriend)?  For classes that have a lot of tests that need to be
friends with it, it can be nice not to have twenty FRIEND_TEST lines in the
class, and there is nothing magical about that macro that should make it more
desirable (apart from the obvious naming, which should be achievable with the
TestFriend prefix or some other prefix).

+  DISALLOW_IMPLICIT_CONSTRUCTORS(WindowsDhcpProxyScriptFetcher);
+};
+
+}  // namespace net
+
+#endif  // NET_PROXY_DHCP_PROXY_SCRIPT_FETCHER_WIN_H_