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

net/proxy/dhcp_proxy_script_fetcher_win.cc

+// 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.
+
+#include "net/proxy/dhcp_proxy_script_fetcher_win.h"
+
+#include "net/base/net_errors.h"
+#include "net/proxy/dhcp_proxy_script_adapter_fetcher_win.h"
+
+#include <winsock2.h>
+#include <iphlpapi.h>
+#pragma comment(lib, "iphlpapi.lib")
+
+namespace {
+
+// How long to wait at maximum after we get results (a PAC file or
+// knowledge that no PAC file is configured) from whichever network
+// adapter finishes first.
+const int kMaxWaitAfterFirstResultMs = 400;
+
+}  // namespace
+
+namespace net {
+
+WindowsDhcpProxyScriptFetcher::WindowsDhcpProxyScriptFetcher(
+    URLRequestContext* url_request_context)
+    : state_(STATE_START),
+      ALLOW_THIS_IN_INITIALIZER_LIST(fetcher_callback_(
+          this, &WindowsDhcpProxyScriptFetcher::OnFetcherDone)),
+      num_pending_fetchers_(0),
+      url_request_context_(url_request_context) {
+  DCHECK(url_request_context_);
+}
+
+WindowsDhcpProxyScriptFetcher::~WindowsDhcpProxyScriptFetcher() {
+  Cancel();
+}
+
+int WindowsDhcpProxyScriptFetcher::Fetch(string16* utf16_text,
+                                         CompletionCallback* callback) {
+  DCHECK(CalledOnValidThread());
+  if (state_ != STATE_START && state_ != STATE_DONE) {
+    NOTREACHED();
+    return ERR_UNEXPECTED;
+  }
+
+  std::set<std::string> adapter_names;
+  if (!ImplGetCandidateAdapterNames(&adapter_names)) {

[eroman, 2011/04/21 05:22:48]

Is this a fast operation? (in other words, is it OK to be enumerating the
adapter names on the IO thread).

[Jói, 2011/04/21 15:57:38]

I believe so.  It calls the GetAdaptersAddresses Win32 API, which I don't
believe does any I/O.  I did a quick search online and I can't find any
information about "slow" or "hangs" or such related to the function.  If you
want me to make sure, I could add a UMA timer around use of the function.

In Chrome code, it is already used on the UI thread, via
content/browser/renderer_host/p2p/socket_dispatcher_host.cc (which calls
net::GetNetworkList()).  So if you think there might be a problem it would need
to be fixed there too.

+    return ERR_UNEXPECTED;
+  }
+  if (adapter_names.empty()) {
+    *utf16_text = L"";

[eroman, 2011/04/21 05:22:48]

no need to set this.

[Jói, 2011/05/03 21:20:59]

Done.

+    return ERR_PAC_NOT_IN_DHCP;
+  }
+
+  state_ = STATE_NO_RESULTS;
+
+  client_callback_ = callback;
+  destination_string_ = utf16_text;
+
+  for (std::set<std::string>::iterator it = adapter_names.begin();
+       it != adapter_names.end();
+       ++it) {
+    scoped_refptr<DhcpProxyScriptAdapterFetcher> fetcher(
+        ImplCreateAdapterFetcher());
+    fetcher->Fetch(*it, &fetcher_callback_);
+    fetchers_.push_back(fetcher.get());
+  }
+  num_pending_fetchers_ = fetchers_.size();
+
+  return ERR_IO_PENDING;
+}
+
+void WindowsDhcpProxyScriptFetcher::Cancel() {
+  DCHECK(CalledOnValidThread());
+  CancelImpl(true);
+}
+
+URLRequestContext* WindowsDhcpProxyScriptFetcher::GetRequestContext() const {
+  DCHECK(CalledOnValidThread());
+  return url_request_context_;
+}
+
+std::string WindowsDhcpProxyScriptFetcher::GetFetcherName() const {
+  DCHECK(CalledOnValidThread());
+  return "win";
+}
+
+GURL WindowsDhcpProxyScriptFetcher::GetPacURL() const {
+  DCHECK(CalledOnValidThread());
+  DCHECK(state_ == STATE_DONE);
+
+  return pac_url_;
+}
+
+void WindowsDhcpProxyScriptFetcher::CancelImpl(bool clear_fetchers) {
+  if (state_ != STATE_DONE) {
+    wait_timer_.Stop();
+    state_ = STATE_DONE;
+
+    for (FetcherList::iterator it = fetchers_.begin();
+         it != fetchers_.end();
+         ++it) {
+      (*it)->Cancel();
+    }
+
+    if (clear_fetchers) {
+      fetchers_.clear();
+    }
+  }
+}
+
+void WindowsDhcpProxyScriptFetcher::OnFetcherDone(int result) {
+  DCHECK(state_ == STATE_NO_RESULTS || state_ == STATE_SOME_RESULTS);
+
+  if (--num_pending_fetchers_ == 0) {
+    TransitionToDone();
+    return;
+  }
+
+  // If the only pending adapters are those less preferred than one
+  // with a valid PAC script, we do not need to wait any longer.
+  for (FetcherList::iterator it = fetchers_.begin();
+       it != fetchers_.end();
+       ++it) {
+    bool did_finish = (*it)->DidFinish();
+    int result = (*it)->result();
+    if (did_finish && result == OK) {
+      TransitionToDone();
+      return;
+    }
+    if (!did_finish || result != ERR_PAC_NOT_IN_DHCP) {
+      break;
+    }
+  }
+
+  // Once we have a single result, we set a maximum on how long to wait
+  // for the rest of the results.
+  if (state_ == STATE_NO_RESULTS) {
+    state_ = STATE_SOME_RESULTS;
+    wait_timer_.Start(

[eroman, 2011/04/21 05:22:48]

isn't there another timer already?

[Jói, 2011/05/03 21:20:59]

There is a separate timer in the AdapterFetcher.  This timer is from when the
first AdapterFetcher returns, if the timer fires we stop waiting for slower
AdapterFetcher instances.

+        base::TimeDelta::FromMilliseconds(ImplGetMaxWaitMs()),
+        this, &WindowsDhcpProxyScriptFetcher::OnWaitTimer);
+  }
+}
+
+void WindowsDhcpProxyScriptFetcher::OnWaitTimer() {
+  DCHECK(state_ == STATE_SOME_RESULTS);
+  TransitionToDone();
+}
+
+void WindowsDhcpProxyScriptFetcher::TransitionToDone() {
+  DCHECK(state_ == STATE_NO_RESULTS || state_ == STATE_SOME_RESULTS);
+
+  // This does not alter state for fetchers that are already done.
+  CancelImpl(false);
+
+  // Should have returned immediately at Fetch() if no adapters to check.
+  DCHECK(!fetchers_.empty());
+
+  // Scan twice for the result; once through the whole list for success,
+  // then if no success, return result for most preferred network adapter,
+  // preferring "real" network errors to the ERR_PAC_NOT_IN_DHCP error.
+  // Default to ERR_ABORTED if no fetcher completed.
+  int result = ERR_ABORTED;
+  for (FetcherList::iterator it = fetchers_.begin();
+       it != fetchers_.end();
+       ++it) {
+    if ((*it)->DidFinish() && (*it)->result() == OK) {
+      result = OK;
+      *destination_string_ = (*it)->pac_script();
+      pac_url_ = (*it)->pac_url();
+      break;
+    }
+  }
+  if (result != OK) {
+    destination_string_->clear();
+    for (FetcherList::iterator it = fetchers_.begin();
+         it != fetchers_.end();
+         ++it) {
+      if ((*it)->DidFinish()) {
+        result = (*it)->result();
+        if (result != ERR_PAC_NOT_IN_DHCP) {
+          break;
+        }
+      }
+    }
+  }
+
+  client_callback_->Run(result);
+  fetchers_.clear();
+  state_ = STATE_DONE;
+}
+
+DhcpProxyScriptAdapterFetcher*
+    WindowsDhcpProxyScriptFetcher::ImplCreateAdapterFetcher() {
+  return new DhcpProxyScriptAdapterFetcher(url_request_context_);
+}
+
+bool WindowsDhcpProxyScriptFetcher::ImplGetCandidateAdapterNames(
+    std::set<std::string>* adapter_names) {
+  return GetCandidateAdapterNames(adapter_names);
+}
+
+int WindowsDhcpProxyScriptFetcher::ImplGetMaxWaitMs() {
+  return kMaxWaitAfterFirstResultMs;
+}
+
+
+bool WindowsDhcpProxyScriptFetcher::GetCandidateAdapterNames(
+    std::set<std::string>* adapter_names) {
+  DCHECK(adapter_names);
+
+  // The GetAdaptersAddresses MSDN page recommends using a size of 15000 to
+  // avoid reallocation.
+  ULONG adapters_size = 15000;
+  scoped_ptr_malloc<IP_ADAPTER_ADDRESSES> adapters;
+  ULONG error = ERROR_SUCCESS;
+  int num_tries = 0;
+  do {
+    adapters.reset(
+        reinterpret_cast<IP_ADAPTER_ADDRESSES*>(malloc(adapters_size)));
+    // Return only unicast addresses, and skip information we do not need.
+    error = GetAdaptersAddresses(AF_UNSPEC,
+                                 GAA_FLAG_SKIP_ANYCAST |
+                                 GAA_FLAG_SKIP_MULTICAST |
+                                 GAA_FLAG_SKIP_DNS_SERVER |
+                                 GAA_FLAG_SKIP_FRIENDLY_NAME,
+                                 NULL,
+                                 adapters.get(),
+                                 &adapters_size);
+    ++num_tries;
+  } while (error == ERROR_BUFFER_OVERFLOW && num_tries <= 3);
+
+  if (error == ERROR_NO_DATA) {
+    // There are no adapters that we care about.
+    return true;
+  }
+
+  if (error != ERROR_SUCCESS) {
+    NOTREACHED();
+    return false;
+  }
+
+  IP_ADAPTER_ADDRESSES* adapter = NULL;
+  for (adapter = adapters.get(); adapter; adapter = adapter->Next) {
+    if (adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK)
+      continue;
+    if ((adapter->Flags & IP_ADAPTER_DHCP_ENABLED) == 0)
+      continue;
+
+    DCHECK(adapter->AdapterName);
+    adapter_names->insert(adapter->AdapterName);
+  }
+
+  return true;
+}
+
+}  // namespace net