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

net/proxy/dhcp_proxy_script_adapter_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_adapter_fetcher_win.h"
+
+#include "base/message_loop_proxy.h"
+#include "base/sys_string_conversions.h"
+#include "base/task.h"
+#include "base/threading/worker_pool.h"
+#include "base/time.h"
+#include "net/base/net_errors.h"
+#include "net/proxy/dhcpcsvc_init_win.h"
+#include "net/proxy/proxy_script_fetcher_impl.h"
+#include "net/url_request/url_request_context.h"
+
+#include <windows.h>
+#include <winsock2.h>
+#include <dhcpcsdk.h>
+#pragma comment(lib, "dhcpcsvc.lib")
+
+namespace {
+
+// Maximum amount of time to wait for response from the Win32 DHCP API.
+const int kTimeoutMs = 2000;
+
+}  // namespace
+
+namespace net {
+
+DhcpProxyScriptAdapterFetcher::DhcpProxyScriptAdapterFetcher(
+    URLRequestContext* url_request_context)
+    : state_(STATE_START),
+      result_(ERR_IO_PENDING),
+      callback_(NULL),
+      ALLOW_THIS_IN_INITIALIZER_LIST(
+          script_fetcher_callback_(
+              this, &DhcpProxyScriptAdapterFetcher::OnFetcherDone)),
+      url_request_context_(url_request_context) {
+}
+
+DhcpProxyScriptAdapterFetcher::~DhcpProxyScriptAdapterFetcher() {
+  Cancel();
+}
+
+void DhcpProxyScriptAdapterFetcher::Fetch(
+    const std::string& adapter_name, CompletionCallback* callback) {
+  DCHECK(CalledOnValidThread());
+  DCHECK_EQ(state_, STATE_START);
+  result_ = ERR_IO_PENDING;
+  pac_script_ = string16();
+  state_ = STATE_WAIT_DHCP;
+  callback_ = callback;
+
+  wait_timer_.Start(ImplGetTimeout(),
+                    this, &DhcpProxyScriptAdapterFetcher::OnTimeout);
+  worker_thread_ = ImplCreateWorkerThread(AsWeakPtr());
+  worker_thread_->Start(adapter_name);
+}
+
+void DhcpProxyScriptAdapterFetcher::Cancel() {

[eroman, 2011/05/17 04:39:39]

This is a one-shot class right? (I am guessing so, since Fetch() asserts that
state_ == STATE_START).

Just checking, since we don't explicitly cancel worker_thread_, so if we were to
call Fetch() after Cancel() might not do the right thing.

[Jói, 2011/05/17 15:38:35]

Correct, this is documented on Fetch():

  // You may only call Fetch() once on a given instance of
  // DhcpProxyScriptAdapterFetcher.

+  DCHECK(CalledOnValidThread());
+  callback_ = NULL;
+  wait_timer_.Stop();
+  script_fetcher_.reset();
+
+  switch (state_) {
+    case STATE_WAIT_DHCP:
+      // Nothing to do here, we let the worker thread run to completion,
+      // the task it posts back when it completes will check the state.
+      break;
+    case STATE_WAIT_URL:
+      break;
+    case STATE_START:
+    case STATE_FINISH:
+    case STATE_CANCEL:
+      break;
+  }
+
+  if (state_ != STATE_FINISH) {
+    result_ = ERR_ABORTED;
+    state_ = STATE_CANCEL;
+  }
+}
+
+bool DhcpProxyScriptAdapterFetcher::DidFinish() const {
+  DCHECK(CalledOnValidThread());
+  return state_ == STATE_FINISH;
+}
+
+int DhcpProxyScriptAdapterFetcher::GetResult() const {
+  DCHECK(CalledOnValidThread());
+  return result_;
+}
+
+string16 DhcpProxyScriptAdapterFetcher::GetPacScript() const {
+  DCHECK(CalledOnValidThread());
+  return pac_script_;
+}
+
+GURL DhcpProxyScriptAdapterFetcher::GetPacURL() const {
+  DCHECK(CalledOnValidThread());
+  return pac_url_;
+}
+
+DhcpProxyScriptAdapterFetcher::WorkerThread::WorkerThread(
+    const base::WeakPtr<DhcpProxyScriptAdapterFetcher>& owner)
+        : owner_(owner),
+          origin_loop_(base::MessageLoopProxy::CreateForCurrentThread()) {
+}
+
+void DhcpProxyScriptAdapterFetcher::WorkerThread::Start(
+    const std::string& adapter_name) {
+  bool succeeded = base::WorkerPool::PostTask(
+      FROM_HERE,
+      NewRunnableMethod(
+          this,
+          &DhcpProxyScriptAdapterFetcher::WorkerThread::ThreadFunc,
+          adapter_name),
+      true);
+  DCHECK(succeeded);
+}
+
+void DhcpProxyScriptAdapterFetcher::WorkerThread::ThreadFunc(
+    const std::string& adapter_name) {
+  std::string url = ImplGetPacURLFromDhcp(adapter_name);
+
+  bool succeeded = origin_loop_->PostTask(
+      FROM_HERE,
+      NewRunnableMethod(
+          this,
+          &DhcpProxyScriptAdapterFetcher::WorkerThread::OnThreadDone,
+          url));
+  DCHECK(succeeded);
+}
+
+void DhcpProxyScriptAdapterFetcher::WorkerThread::OnThreadDone(
+    const std::string& url) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (owner_)
+    owner_->OnQueryDhcpDone(url);
+}
+
+std::string
+    DhcpProxyScriptAdapterFetcher::WorkerThread::ImplGetPacURLFromDhcp(
+        const std::string& adapter_name) {
+  return DhcpProxyScriptAdapterFetcher::GetPacURLFromDhcp(adapter_name);
+}
+
+void DhcpProxyScriptAdapterFetcher::OnQueryDhcpDone(
+    const std::string& url) {
+  DCHECK(CalledOnValidThread());
+  // Because we can't cancel the call to the Win32 API, we can expect
+  // it to finish while we are in a few different states.  The expected
+  // one is WAIT_DHCP, but it could be in CANCEL if Cancel() was called,
+  // or FINISH if timeout occurred.
+  DCHECK(state_ == STATE_WAIT_DHCP || state_ == STATE_CANCEL ||
+         state_ == STATE_FINISH);
+  if (state_ != STATE_WAIT_DHCP)
+    return;
+
+  wait_timer_.Stop();
+
+  pac_url_ = GURL(url);
+  if (pac_url_.is_empty() || !pac_url_.is_valid()) {
+    result_ = ERR_PAC_NOT_IN_DHCP;
+    TransitionToFinish();
+  } else {
+    state_ = STATE_WAIT_URL;
+    script_fetcher_.reset(ImplCreateScriptFetcher());
+    script_fetcher_->Fetch(pac_url_, &pac_script_, &script_fetcher_callback_);
+  }
+}
+
+void DhcpProxyScriptAdapterFetcher::OnTimeout() {
+  DCHECK_EQ(state_, STATE_WAIT_DHCP);
+  result_ = ERR_TIMED_OUT;
+  TransitionToFinish();
+}
+
+void DhcpProxyScriptAdapterFetcher::OnFetcherDone(int result) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(state_ == STATE_WAIT_URL || state_ == STATE_CANCEL);
+  if (state_ == STATE_CANCEL)
+    return;
+
+  // At this point, pac_script_ has already been written to.
+  script_fetcher_.reset();
+  result_ = result;
+  TransitionToFinish();
+}
+
+void DhcpProxyScriptAdapterFetcher::TransitionToFinish() {
+  DCHECK(state_ == STATE_WAIT_DHCP || state_ == STATE_WAIT_URL);
+  state_ = STATE_FINISH;
+  callback_->Run(result_);
+  callback_ = NULL;
+}
+
+ProxyScriptFetcher* DhcpProxyScriptAdapterFetcher::ImplCreateScriptFetcher() {
+  return new ProxyScriptFetcherImpl(url_request_context_);
+}
+
+DhcpProxyScriptAdapterFetcher::WorkerThread*
+    DhcpProxyScriptAdapterFetcher::ImplCreateWorkerThread(
+        const base::WeakPtr<DhcpProxyScriptAdapterFetcher>& owner) {
+  return new WorkerThread(owner);
+}
+
+base::TimeDelta DhcpProxyScriptAdapterFetcher::ImplGetTimeout() const {
+  return base::TimeDelta::FromMilliseconds(kTimeoutMs);
+}
+
+// static
+std::string DhcpProxyScriptAdapterFetcher::GetPacURLFromDhcp(
+    const std::string& adapter_name) {
+  EnsureDhcpcsvcInit();
+
+  std::wstring adapter_name_wide = base::SysMultiByteToWide(adapter_name,
+                                                            CP_ACP);
+
+  DHCPCAPI_PARAMS_ARRAY send_params = { 0, NULL };
+
+  BYTE option_data[] = { 1, 252 };
+  DHCPCAPI_PARAMS wpad_params = { 0 };
+  wpad_params.OptionId = 252;
+  wpad_params.IsVendor = FALSE;  // Surprising, but intentional.
+
+  DHCPCAPI_PARAMS_ARRAY request_params = { 0 };
+  request_params.nParams = 1;
+  request_params.Params = &wpad_params;
+
+  // The maximum message size is typically 4096 bytes on Windows per
+  // http://support.microsoft.com/kb/321592
+  DWORD result_buffer_size = 4096;
+  scoped_ptr_malloc<BYTE> result_buffer;
+  int retry_count = 0;
+  DWORD res = NO_ERROR;
+  do {
+    result_buffer.reset(reinterpret_cast<BYTE*>(malloc(result_buffer_size)));
+
+    // Note that while the DHCPCAPI_REQUEST_SYNCHRONOUS flag seems to indicate
+    // there might be an asynchronous mode, there seems to be (at least in
+    // terms of well-documented use of this API) only a synchronous mode, with
+    // an optional "async notifications later if the option changes" mode.
+    // Even IE9, which we hope to emulate as IE is the most widely deployed
+    // previous implementation of the DHCP aspect of WPAD and the only one
+    // on Windows (Konqueror is the other, on Linux), uses this API with the
+    // synchronous flag.  There seem to be several Microsoft Knowledge Base
+    // articles about calls to this function failing when other flags are used
+    // (e.g. http://support.microsoft.com/kb/885270) so we won't take any
+    // chances on non-standard, poorly documented usage.
+    res = ::DhcpRequestParams(DHCPCAPI_REQUEST_SYNCHRONOUS,
+                              NULL,
+                              const_cast<LPWSTR>(adapter_name_wide.c_str()),
+                              NULL,
+                              send_params, request_params,
+                              result_buffer.get(), &result_buffer_size,
+                              NULL);
+    ++retry_count;
+  } while (res == ERROR_MORE_DATA && retry_count <= 3);
+
+  if (res != NO_ERROR) {
+    NOTREACHED();
+  } else if (wpad_params.nBytesData) {
+    // The result should be ASCII, not wide character.
+    DCHECK_EQ(strlen(reinterpret_cast<const char*>(wpad_params.Data)) + 1,
+              wpad_params.nBytesData);
+    // Return only up to the first null in case of embedded NULLs; if the
+    // server is giving us back a buffer with embedded NULLs, something is
+    // broken anyway.
+    return std::string(reinterpret_cast<const char *>(wpad_params.Data));
+  }
+
+  return "";
+}
+
+}  // namespace net