Add get_server_time utility

get_server_time makes a request to an HTTP/HTTPS server and snarfs
the server time from the HTTP headers.

The code here will eventually be adapted to track "sane time" (see
design document linked from the bug).

Also update usage comments of URLFetcher to note that a request
context has to be set.

BUG=146090


Review URL: https://chromiumcodereview.appspot.com/10907039

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@154868 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 374 insertions, 0 deletions

diff --git a/net/tools/get_server_time/get_server_time.cc b/net/tools/get_server_time/get_server_time.cc
new file mode 100644
index 0000000..3bbe271
--- /dev/null
+++ b/net/tools/get_server_time/get_server_time.cc
@@ -0,0 +1,374 @@
+// 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.
+
+// This is a small utility that snarfs the server time from the
+// response headers of an http/https HEAD request and compares it to
+// the local time.
+//
+// TODO(akalin): Also snarf the server time from the TLS handshake, if
+// any (http://crbug.com/146090).
+
+#include <cstdio>
+#include <cstdlib>
+#include <string>
+
+#include "base/at_exit.h"
+#include "base/basictypes.h"
+#include "base/command_line.h"
+#include "base/compiler_specific.h"
+#include "base/format_macros.h"
+#include "base/i18n/time_formatting.h"
+#include "base/json/json_writer.h"
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop.h"
+#include "base/single_thread_task_runner.h"
+#include "base/string_number_conversions.h"
+#include "base/time.h"
+#include "base/utf_string_conversions.h"
+#include "base/values.h"
+#include "build/build_config.h"
+#include "googleurl/src/gurl.h"
+#include "net/base/net_errors.h"
+#include "net/base/net_log.h"
+#include "net/http/http_response_headers.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_request_context.h"
+#include "net/url_request/url_request_context_builder.h"
+#include "net/url_request/url_request_context_getter.h"
+#include "net/url_request/url_request_status.h"
+
+#if defined(OS_MACOSX)
+#include "base/mac/scoped_nsautorelease_pool.h"
+#elif defined(OS_LINUX)
+#include "net/proxy/proxy_config.h"
+#include "net/proxy/proxy_config_service_fixed.h"
+#endif
+
+namespace {
+
+// base::TimeTicks::Now() is documented to have a resolution of
+// ~1-15ms.
+const int64 kTicksResolutionMs = 15;
+
+// For the sources that are supported (HTTP date headers, TLS
+// handshake), the resolution of the server time is 1 second.
+const int64 kServerTimeResolutionMs = 1000;
+
+// Assume base::Time::Now() has the same resolution as
+// base::TimeTicks::Now().
+//
+// TODO(akalin): Figure out the real resolution.
+const int64 kTimeResolutionMs = kTicksResolutionMs;
+
+// Simply quits the current message loop when finished.  Used to make
+// URLFetcher synchronous.
+class QuitDelegate : public net::URLFetcherDelegate {
+ public:
+  QuitDelegate() {}
+
+  virtual ~QuitDelegate() {}
+
+  // net::URLFetcherDelegate implementation.
+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE {
+    MessageLoop::current()->Quit();
+  }
+
+  virtual void OnURLFetchDownloadProgress(
+      const net::URLFetcher* source,
+      int64 current, int64 total) OVERRIDE {
+    NOTREACHED();
+  }
+
+  virtual void OnURLFetchDownloadData(
+      const net::URLFetcher* source,
+      scoped_ptr<std::string> download_data) OVERRIDE{
+    NOTREACHED();
+  }
+
+  virtual bool ShouldSendDownloadData() OVERRIDE {
+    NOTREACHED();
+    return false;
+  }
+
+  virtual void OnURLFetchUploadProgress(const net::URLFetcher* source,
+                                        int64 current, int64 total) OVERRIDE {
+    NOTREACHED();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(QuitDelegate);
+};
+
+// NetLog implementation that simply prints events to the logs.
+class PrintingLog : public net::NetLog {
+ public:
+  PrintingLog() : next_id_(1) {}
+
+  virtual ~PrintingLog() {}
+
+  // NetLog implementation:
+  virtual void OnAddEntry(const net::NetLog::Entry& entry) OVERRIDE {
+    // The log level of the entry is unknown, so just assume it maps
+    // to VLOG(1).
+    if (!VLOG_IS_ON(1))
+      return;
+
+    const char* const source_type =
+        net::NetLog::SourceTypeToString(entry.source().type);
+    const char* const event_type =
+        net::NetLog::EventTypeToString(entry.type());
+    const char* const event_phase =
+        net::NetLog::EventPhaseToString(entry.phase());
+    scoped_ptr<base::Value> params(entry.ParametersToValue());
+    std::string params_str;
+    if (params.get()) {
+      base::JSONWriter::Write(params.get(), &params_str);
+      params_str.insert(0, ": ");
+    }
+
+    VLOG(1) << source_type << "(" << entry.source().id << "): "
+            << event_type << ": " << event_phase << params_str;
+  }
+
+  virtual uint32 NextID() OVERRIDE {
+    return next_id_++;
+  }
+
+  virtual LogLevel GetLogLevel() const OVERRIDE {
+    const int vlog_level = logging::GetVlogLevel(__FILE__);
+    if (vlog_level <= 0) {
+      return LOG_BASIC;
+    }
+    if (vlog_level == 1) {
+      return LOG_ALL_BUT_BYTES;
+    }
+    return LOG_ALL;
+  }
+
+  virtual void AddThreadSafeObserver(ThreadSafeObserver* observer,
+                                     LogLevel log_level) OVERRIDE {
+    NOTIMPLEMENTED();
+  }
+
+  virtual void SetObserverLogLevel(ThreadSafeObserver* observer,
+                                   LogLevel log_level) OVERRIDE {
+    NOTIMPLEMENTED();
+  }
+
+  virtual void RemoveThreadSafeObserver(ThreadSafeObserver* observer) OVERRIDE {
+    NOTIMPLEMENTED();
+  }
+
+ private:
+  uint32 next_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrintingLog);
+};
+
+// Builds a URLRequestContext assuming there's only a single loop.
+scoped_ptr<net::URLRequestContext> BuildURLRequestContext() {
+  net::URLRequestContextBuilder builder;
+#if defined(OS_LINUX)
+  // On Linux, use a fixed ProxyConfigService, since the default one
+  // depends on glib.
+  //
+  // TODO(akalin): Remove this once http://crbug.com/146421 is fixed.
+  builder.set_proxy_config_service(
+      new net::ProxyConfigServiceFixed(net::ProxyConfig()));
+#endif
+  scoped_ptr<net::URLRequestContext> context(builder.Build());
+  context->set_net_log(new PrintingLog());
+  return context.Pass();
+}
+
+class SingleThreadRequestContextGetter : public net::URLRequestContextGetter {
+ public:
+  // Since there's only a single thread, there's no need to worry
+  // about when |context_| gets created.
+  explicit SingleThreadRequestContextGetter(
+      const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner)
+      : context_(BuildURLRequestContext()),
+        main_task_runner_(main_task_runner) {}
+
+  virtual net::URLRequestContext* GetURLRequestContext() OVERRIDE {
+    return context_.get();
+  }
+
+  virtual scoped_refptr<base::SingleThreadTaskRunner>
+  GetNetworkTaskRunner() const OVERRIDE {
+    return main_task_runner_;
+  }
+
+ private:
+  virtual ~SingleThreadRequestContextGetter() {}
+
+  const scoped_ptr<net::URLRequestContext> context_;
+  const scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
+};
+
+// Assuming that the time |server_time| was received from a server,
+// that the request for the server was started on |start_ticks|, and
+// that it ended on |end_ticks|, fills |server_now| with an estimate
+// of the current time and |server_now_uncertainty| with a
+// conservative estimate of the uncertainty.
+void EstimateServerTimeNow(base::Time server_time,
+                           base::TimeTicks start_ticks,
+                           base::TimeTicks end_ticks,
+                           base::Time* server_now,
+                           base::TimeDelta* server_now_uncertainty) {
+  const base::TimeDelta delta_ticks = end_ticks - start_ticks;
+  const base::TimeTicks mid_ticks = start_ticks + delta_ticks / 2;
+  const base::TimeDelta estimated_elapsed = base::TimeTicks::Now() - mid_ticks;
+
+  *server_now = server_time + estimated_elapsed;
+
+  *server_now_uncertainty =
+      base::TimeDelta::FromMilliseconds(kServerTimeResolutionMs) +
+      delta_ticks + 3 * base::TimeDelta::FromMilliseconds(kTicksResolutionMs);
+}
+
+// Assuming that the time of the server is |server_now| with
+// uncertainty |server_now_uncertainty| and that the local time is
+// |now|, fills |skew| with the skew of the local clock (i.e., add
+// |*skew| to a client time to get a server time) and
+// |skew_uncertainty| with a conservative estimate of the uncertainty.
+void EstimateSkew(base::Time server_now,
+                  base::TimeDelta server_now_uncertainty,
+                  base::Time now,
+                  base::TimeDelta now_uncertainty,
+                  base::TimeDelta* skew,
+                  base::TimeDelta* skew_uncertainty) {
+  *skew = server_now - now;
+  *skew_uncertainty = server_now_uncertainty + now_uncertainty;
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+#if defined(OS_MACOSX)
+  base::mac::ScopedNSAutoreleasePool pool;
+#endif
+
+  base::AtExitManager exit_manager;
+  CommandLine::Init(argc, argv);
+  logging::InitLogging(
+      NULL,
+      logging::LOG_ONLY_TO_SYSTEM_DEBUG_LOG,
+      logging::LOCK_LOG_FILE,
+      logging::DELETE_OLD_LOG_FILE,
+      logging::DISABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS);
+
+  const CommandLine& parsed_command_line = *CommandLine::ForCurrentProcess();
+  GURL url(parsed_command_line.GetSwitchValueASCII("url"));
+  if (!url.is_valid() ||
+      (url.scheme() != "http" && url.scheme() != "https")) {
+    std::fprintf(
+        stderr,
+        "Usage: %s --url=[http|https]://www.example.com [--v=[1|2]]\n",
+        argv[0]);
+    return EXIT_FAILURE;
+  }
+
+  MessageLoopForIO main_loop;
+
+  // NOTE: A NetworkChangeNotifier could be instantiated here, but
+  // that interferes with the request that will be sent; some
+  // implementations always send out an OnIPAddressChanged() message,
+  // which causes the DNS resolution to abort.  It's simpler to just
+  // not instantiate one, since only a single request is sent anyway.
+
+  scoped_refptr<SingleThreadRequestContextGetter> context_getter(
+      new SingleThreadRequestContextGetter(main_loop.message_loop_proxy()));
+
+  QuitDelegate delegate;
+  scoped_ptr<net::URLFetcher> fetcher(
+      net::URLFetcher::Create(url, net::URLFetcher::HEAD, &delegate));
+  fetcher->SetRequestContext(context_getter.get());
+
+  const base::Time start_time = base::Time::Now();
+  const base::TimeTicks start_ticks = base::TimeTicks::Now();
+
+  fetcher->Start();
+  std::printf(
+      "Request started at %s (ticks = %"PRId64")\n",
+      UTF16ToUTF8(base::TimeFormatFriendlyDateAndTime(start_time)).c_str(),
+      start_ticks.ToInternalValue());
+
+  // |delegate| quits |main_loop| when the request is done.
+  main_loop.Run();
+
+  const base::Time end_time = base::Time::Now();
+  const base::TimeTicks end_ticks = base::TimeTicks::Now();
+
+  std::printf(
+      "Request ended at %s (ticks = %"PRId64")\n",
+      UTF16ToUTF8(base::TimeFormatFriendlyDateAndTime(end_time)).c_str(),
+      end_ticks.ToInternalValue());
+
+  const int64 delta_ticks_internal =
+      end_ticks.ToInternalValue() - start_ticks.ToInternalValue();
+  const base::TimeDelta delta_ticks = end_ticks - start_ticks;
+
+  std::printf(
+      "Request took %"PRId64" ticks (%.2f ms)\n",
+      delta_ticks_internal, delta_ticks.InMillisecondsF());
+
+  const net::URLRequestStatus status = fetcher->GetStatus();
+  if (status.status() != net::URLRequestStatus::SUCCESS) {
+    LOG(ERROR) << "Request failed with error code: "
+               << net::ErrorToString(status.error());
+    return EXIT_FAILURE;
+  }
+
+  const net::HttpResponseHeaders* const headers =
+      fetcher->GetResponseHeaders();
+  if (!headers) {
+    LOG(ERROR) << "Response does not have any headers";
+    return EXIT_FAILURE;
+  }
+
+  void* iter = NULL;
+  std::string date_header;
+  while (headers->EnumerateHeader(&iter, "Date", &date_header)) {
+    std::printf("Got date header: %s\n", date_header.c_str());
+  }
+
+  base::Time server_time;
+  if (!headers->GetDateValue(&server_time)) {
+    LOG(ERROR) << "Could not parse time from server response headers";
+    return EXIT_FAILURE;
+  }
+
+  std::printf(
+      "Got time %s from server\n",
+      UTF16ToUTF8(base::TimeFormatFriendlyDateAndTime(server_time)).c_str());
+
+  base::Time server_now;
+  base::TimeDelta server_now_uncertainty;
+  EstimateServerTimeNow(server_time, start_ticks, end_ticks,
+                        &server_now, &server_now_uncertainty);
+  base::Time now = base::Time::Now();
+
+  std::printf(
+      "According to the server, it is now %s with uncertainty %.2f ms\n",
+      UTF16ToUTF8(base::TimeFormatFriendlyDateAndTime(server_now)).c_str(),
+      server_now_uncertainty.InMillisecondsF());
+
+  base::TimeDelta skew;
+  base::TimeDelta skew_uncertainty;
+  EstimateSkew(server_now, server_now_uncertainty, now,
+               base::TimeDelta::FromMilliseconds(kTimeResolutionMs),
+               &skew, &skew_uncertainty);
+
+  std::printf(
+      "An estimate for the local clock skew is %.2f ms with "
+      "uncertainty %.2f ms\n",
+      skew.InMillisecondsF(),
+      skew_uncertainty.InMillisecondsF());
+
+  return EXIT_SUCCESS;
+}