blob: 65279d57804aa133fda45a72c2437f737109100c [file] [log] [blame]
// 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/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/macros.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/message_loop/message_loop.h"
#include "base/single_thread_task_runner.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/utf_string_conversions.h"
#include "base/time/time.h"
#include "base/values.h"
#include "build/build_config.h"
#include "net/base/net_errors.h"
#include "net/http/http_response_headers.h"
#include "net/log/net_log.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"
#include "url/gurl.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
using base::UTF16ToUTF8;
namespace {
// base::TimeTicks::Now() is documented to have a resolution of
// ~1-15ms.
const int64_t kTicksResolutionMs = 15;
// For the sources that are supported (HTTP date headers, TLS
// handshake), the resolution of the server time is 1 second.
const int64_t kServerTimeResolutionMs = 1000;
// Assume base::Time::Now() has the same resolution as
// base::TimeTicks::Now().
//
// TODO(akalin): Figure out the real resolution.
const int64_t kTimeResolutionMs = kTicksResolutionMs;
// Simply quits the current message loop when finished. Used to make
// URLFetcher synchronous.
class QuitDelegate : public net::URLFetcherDelegate {
public:
QuitDelegate() {}
~QuitDelegate() override {}
// net::URLFetcherDelegate implementation.
void OnURLFetchComplete(const net::URLFetcher* source) override {
base::MessageLoop::current()->QuitWhenIdle();
}
void OnURLFetchDownloadProgress(const net::URLFetcher* source,
int64_t current,
int64_t total) override {
NOTREACHED();
}
void OnURLFetchUploadProgress(const net::URLFetcher* source,
int64_t current,
int64_t total) override {
NOTREACHED();
}
private:
DISALLOW_COPY_AND_ASSIGN(QuitDelegate);
};
// NetLog::ThreadSafeObserver implementation that simply prints events
// to the logs.
class PrintingLogObserver : public net::NetLog::ThreadSafeObserver {
public:
PrintingLogObserver() {}
~PrintingLogObserver() override {
// This is guaranteed to be safe as this program is single threaded.
net_log()->DeprecatedRemoveObserver(this);
}
// NetLog::ThreadSafeObserver implementation:
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, &params_str);
params_str.insert(0, ": ");
}
VLOG(1) << source_type << "(" << entry.source().id << "): "
<< event_type << ": " << event_phase << params_str;
}
private:
DISALLOW_COPY_AND_ASSIGN(PrintingLogObserver);
};
// Builds a URLRequestContext assuming there's only a single loop.
scoped_ptr<net::URLRequestContext>
BuildURLRequestContext(net::NetLog* net_log) {
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(
make_scoped_ptr(new net::ProxyConfigServiceFixed(net::ProxyConfig())));
#endif
scoped_ptr<net::URLRequestContext> context(builder.Build());
context->set_net_log(net_log);
return context;
}
// 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;
base::CommandLine::Init(argc, argv);
logging::LoggingSettings settings;
settings.logging_dest = logging::LOG_TO_SYSTEM_DEBUG_LOG;
logging::InitLogging(settings);
const base::CommandLine& parsed_command_line =
*base::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;
}
base::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.
// The declaration order for net_log and printing_log_observer is
// important. The destructor of PrintingLogObserver removes itself
// from net_log, so net_log must be available for entire lifetime of
// printing_log_observer.
net::NetLog net_log;
PrintingLogObserver printing_log_observer;
net_log.DeprecatedAddObserver(&printing_log_observer,
net::NetLogCaptureMode::IncludeSocketBytes());
QuitDelegate delegate;
scoped_ptr<net::URLFetcher> fetcher =
net::URLFetcher::Create(url, net::URLFetcher::HEAD, &delegate);
scoped_ptr<net::URLRequestContext> url_request_context(
BuildURLRequestContext(&net_log));
fetcher->SetRequestContext(
// Since there's only a single thread, there's no need to worry
// about when the URLRequestContext gets created.
// The URLFetcher will take a reference on the object, and hence
// implicitly take ownership.
new net::TrivialURLRequestContextGetter(url_request_context.get(),
main_loop.task_runner()));
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_t 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;
}
size_t iter = 0;
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;
}