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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/base/backoff_entry.h"
#include "base/containers/span.h"
#include "base/logging.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/stringprintf.h"
#include "base/time/tick_clock.h"
#include "base/time/time.h"
#include "base/values.h"
#include "net/base/backoff_entry_serializer.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace net {
namespace {
using base::Time;
using base::TimeTicks;
const Time kParseTime = Time::FromMillisecondsSinceUnixEpoch(
1430907555111); // May 2015 for realism
BackoffEntry::Policy base_policy = {
0 /* num_errors_to_ignore */,
1000 /* initial_delay_ms */,
2.0 /* multiply_factor */,
0.0 /* jitter_factor */,
20000 /* maximum_backoff_ms */,
2000 /* entry_lifetime_ms */,
false /* always_use_initial_delay */
};
class TestTickClock : public base::TickClock {
public:
TestTickClock() = default;
TestTickClock(const TestTickClock&) = delete;
TestTickClock& operator=(const TestTickClock&) = delete;
~TestTickClock() override = default;
TimeTicks NowTicks() const override { return now_ticks_; }
void set_now(TimeTicks now) { now_ticks_ = now; }
private:
TimeTicks now_ticks_;
};
// This test exercises the code that computes the "backoff duration" and tests
// BackoffEntrySerializer::SerializeToList computes the backoff duration of a
// BackoffEntry by subtracting two base::TimeTicks values. Note that
// base::TimeTicks::operator- does not protect against overflow. Because
// SerializeToList never returns null, its resolution strategy is to default to
// a zero base::TimeDelta when the subtraction would overflow.
TEST(BackoffEntrySerializerTest, SpecialCasesOfBackoffDuration) {
const base::TimeTicks kZeroTicks;
struct TestCase {
base::TimeTicks release_time;
base::TimeTicks timeticks_now;
base::TimeDelta expected_backoff_duration;
};
TestCase test_cases[] = {
// Non-overflowing subtraction works as expected.
{
.release_time = kZeroTicks + base::Microseconds(100),
.timeticks_now = kZeroTicks + base::Microseconds(75),
.expected_backoff_duration = base::Microseconds(25),
},
{
.release_time = kZeroTicks + base::Microseconds(25),
.timeticks_now = kZeroTicks + base::Microseconds(100),
.expected_backoff_duration = base::Microseconds(-75),
},
// Defaults to zero when one of the operands is +/- infinity.
{
.release_time = base::TimeTicks::Min(),
.timeticks_now = kZeroTicks,
.expected_backoff_duration = base::TimeDelta(),
},
{
.release_time = base::TimeTicks::Max(),
.timeticks_now = kZeroTicks,
.expected_backoff_duration = base::TimeDelta(),
},
{
.release_time = kZeroTicks,
.timeticks_now = base::TimeTicks::Min(),
.expected_backoff_duration = base::TimeDelta(),
},
{
.release_time = kZeroTicks,
.timeticks_now = base::TimeTicks::Max(),
.expected_backoff_duration = base::TimeDelta(),
},
// Defaults to zero when both of the operands are +/- infinity.
{
.release_time = base::TimeTicks::Min(),
.timeticks_now = base::TimeTicks::Min(),
.expected_backoff_duration = base::TimeDelta(),
},
{
.release_time = base::TimeTicks::Min(),
.timeticks_now = base::TimeTicks::Max(),
.expected_backoff_duration = base::TimeDelta(),
},
{
.release_time = base::TimeTicks::Max(),
.timeticks_now = base::TimeTicks::Min(),
.expected_backoff_duration = base::TimeDelta(),
},
{
.release_time = base::TimeTicks::Max(),
.timeticks_now = base::TimeTicks::Max(),
.expected_backoff_duration = base::TimeDelta(),
},
// Defaults to zero when the subtraction overflows, even when neither
// operand is infinity.
{
.release_time = base::TimeTicks::Max() - base::Microseconds(1),
.timeticks_now = kZeroTicks + base::Microseconds(-1),
.expected_backoff_duration = base::TimeDelta(),
},
};
size_t test_index = 0;
for (const TestCase& test_case : test_cases) {
SCOPED_TRACE(base::StringPrintf("Running test case #%zu", test_index));
++test_index;
Time original_time = base::Time::Now();
TestTickClock original_ticks;
original_ticks.set_now(test_case.timeticks_now);
BackoffEntry original(&base_policy, &original_ticks);
// Set the custom release time.
original.SetCustomReleaseTime(test_case.release_time);
base::Value::List serialized =
BackoffEntrySerializer::SerializeToList(original, original_time);
// Check that the serialized backoff duration matches our expectation.
const std::string& serialized_backoff_duration_string =
serialized[2].GetString();
int64_t serialized_backoff_duration_us;
EXPECT_TRUE(base::StringToInt64(serialized_backoff_duration_string,
&serialized_backoff_duration_us));
base::TimeDelta serialized_backoff_duration =
base::Microseconds(serialized_backoff_duration_us);
EXPECT_EQ(serialized_backoff_duration, test_case.expected_backoff_duration);
}
}
// This test verifies that BackoffEntrySerializer::SerializeToList will not
// serialize an infinite release time.
//
// In pseudocode, this is how absolute_release_time is computed:
// backoff_duration = release_time - now;
// absolute_release_time = backoff_duration + original_time;
//
// This test induces backoff_duration to be a nonzero duration and directly sets
// original_time as a large value, such that their addition will overflow.
TEST(BackoffEntrySerializerTest, SerializeFiniteReleaseTime) {
const TimeTicks release_time = TimeTicks() + base::Microseconds(5);
const Time original_time = Time::Max() - base::Microseconds(4);
TestTickClock original_ticks;
original_ticks.set_now(TimeTicks());
BackoffEntry original(&base_policy, &original_ticks);
original.SetCustomReleaseTime(release_time);
base::Value::List serialized =
BackoffEntrySerializer::SerializeToList(original, original_time);
// Reach into the serialization and check the string-formatted release time.
const std::string& serialized_release_time = serialized[3].GetString();
EXPECT_EQ(serialized_release_time, "0");
// Test that |DeserializeFromList| notices this zero-valued release time and
// does not take it at face value.
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(serialized, &base_policy,
&original_ticks, kParseTime);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
}
TEST(BackoffEntrySerializerTest, SerializeNoFailures) {
Time original_time = Time::Now();
TestTickClock original_ticks;
original_ticks.set_now(TimeTicks::Now());
BackoffEntry original(&base_policy, &original_ticks);
base::Value::List serialized =
BackoffEntrySerializer::SerializeToList(original, original_time);
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, &original_ticks, original_time);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.failure_count(), deserialized->failure_count());
EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
}
// Test that deserialization fails instead of producing an entry with an
// infinite release time. (Regression test for https://crbug.com/1293904)
TEST(BackoffEntrySerializerTest, DeserializeNeverInfiniteReleaseTime) {
base::Value::List serialized;
serialized.Append(2);
serialized.Append(2);
serialized.Append("-9223372036854775807");
serialized.Append("2");
TestTickClock original_ticks;
original_ticks.set_now(base::TimeTicks() + base::Microseconds(-1));
base::Time time_now =
base::Time::FromDeltaSinceWindowsEpoch(base::Microseconds(-1));
std::unique_ptr<BackoffEntry> entry =
BackoffEntrySerializer::DeserializeFromList(serialized, &base_policy,
&original_ticks, time_now);
ASSERT_FALSE(entry);
}
TEST(BackoffEntrySerializerTest, SerializeTimeOffsets) {
Time original_time = Time::FromMillisecondsSinceUnixEpoch(
1430907555111); // May 2015 for realism
TestTickClock original_ticks;
BackoffEntry original(&base_policy, &original_ticks);
// 2 errors.
original.InformOfRequest(false);
original.InformOfRequest(false);
base::Value::List serialized =
BackoffEntrySerializer::SerializeToList(original, original_time);
{
// Test that immediate deserialization round-trips.
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, &original_ticks, original_time);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.failure_count(), deserialized->failure_count());
EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
}
{
// Test deserialization when wall clock has advanced but TimeTicks::Now()
// hasn't (e.g. device was rebooted).
Time later_time = original_time + base::Days(1);
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, &original_ticks, later_time);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.failure_count(), deserialized->failure_count());
// Remaining backoff duration continues decreasing while device is off.
// Since TimeTicks::Now() has not advanced, the absolute release time ticks
// will decrease accordingly.
EXPECT_GT(original.GetTimeUntilRelease(),
deserialized->GetTimeUntilRelease());
EXPECT_EQ(original.GetReleaseTime() - base::Days(1),
deserialized->GetReleaseTime());
}
{
// Test deserialization when TimeTicks::Now() has advanced but wall clock
// hasn't (e.g. it's an hour later, but a DST change cancelled that out).
TestTickClock later_ticks;
later_ticks.set_now(TimeTicks() + base::Days(1));
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, &later_ticks, original_time);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.failure_count(), deserialized->failure_count());
// According to the wall clock, no time has passed. So remaining backoff
// duration is preserved, hence the absolute release time ticks increases.
// This isn't ideal - by also serializing the current time and time ticks,
// it would be possible to detect that time has passed but the wall clock
// went backwards, and reduce the remaining backoff duration accordingly,
// however the current implementation does not do this as the benefit would
// be somewhat marginal.
EXPECT_EQ(original.GetTimeUntilRelease(),
deserialized->GetTimeUntilRelease());
EXPECT_EQ(original.GetReleaseTime() + base::Days(1),
deserialized->GetReleaseTime());
}
{
// Test deserialization when both wall clock and TimeTicks::Now() have
// advanced (e.g. it's just later than it used to be).
TestTickClock later_ticks;
later_ticks.set_now(TimeTicks() + base::Days(1));
Time later_time = original_time + base::Days(1);
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(serialized, &base_policy,
&later_ticks, later_time);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.failure_count(), deserialized->failure_count());
// Since both have advanced by the same amount, the absolute release time
// ticks should be preserved; the remaining backoff duration will have
// decreased of course, since time has passed.
EXPECT_GT(original.GetTimeUntilRelease(),
deserialized->GetTimeUntilRelease());
EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
}
{
// Test deserialization when wall clock has gone backwards but TimeTicks
// haven't (e.g. the system clock was fast but they fixed it).
EXPECT_LT(base::Seconds(1), original.GetTimeUntilRelease());
Time earlier_time = original_time - base::Seconds(1);
std::unique_ptr<BackoffEntry> deserialized =
BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, &original_ticks, earlier_time);
ASSERT_TRUE(deserialized.get());
EXPECT_EQ(original.failure_count(), deserialized->failure_count());
// If only the absolute wall clock time was serialized, subtracting the
// (decreased) current wall clock time from the serialized wall clock time
// could give very large (incorrect) values for remaining backoff duration.
// But instead the implementation also serializes the remaining backoff
// duration, and doesn't allow the duration to increase beyond it's previous
// value during deserialization. Hence when the wall clock goes backwards
// the remaining backoff duration will be preserved.
EXPECT_EQ(original.GetTimeUntilRelease(),
deserialized->GetTimeUntilRelease());
// Since TimeTicks::Now() hasn't changed, the absolute release time ticks
// will be equal too in this particular case.
EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
}
}
TEST(BackoffEntrySerializerTest, DeserializeUnknownVersion) {
base::Value::List serialized;
serialized.Append(0); // Format version that never existed
serialized.Append(0); // Failure count
serialized.Append(2.0); // Backoff duration
serialized.Append("1234"); // Absolute release time
auto deserialized = BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, nullptr, kParseTime);
ASSERT_FALSE(deserialized);
}
TEST(BackoffEntrySerializerTest, DeserializeVersion1) {
base::Value::List serialized;
serialized.Append(SerializationFormatVersion::kVersion1);
serialized.Append(0); // Failure count
serialized.Append(2.0); // Backoff duration in seconds as double
serialized.Append("1234"); // Absolute release time
auto deserialized = BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, nullptr, kParseTime);
ASSERT_TRUE(deserialized);
}
TEST(BackoffEntrySerializerTest, DeserializeVersion2) {
base::Value::List serialized;
serialized.Append(SerializationFormatVersion::kVersion2);
serialized.Append(0); // Failure count
serialized.Append("2000"); // Backoff duration
serialized.Append("1234"); // Absolute release time
auto deserialized = BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, nullptr, kParseTime);
ASSERT_TRUE(deserialized);
}
TEST(BackoffEntrySerializerTest, DeserializeVersion2NegativeDuration) {
base::Value::List serialized;
serialized.Append(SerializationFormatVersion::kVersion2);
serialized.Append(0); // Failure count
serialized.Append("-2000"); // Backoff duration
serialized.Append("1234"); // Absolute release time
auto deserialized = BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, nullptr, kParseTime);
ASSERT_TRUE(deserialized);
}
TEST(BackoffEntrySerializerTest, DeserializeVersion1WrongDurationType) {
base::Value::List serialized;
serialized.Append(SerializationFormatVersion::kVersion1);
serialized.Append(0); // Failure count
serialized.Append("2000"); // Backoff duration in seconds as double
serialized.Append("1234"); // Absolute release time
auto deserialized = BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, nullptr, kParseTime);
ASSERT_FALSE(deserialized);
}
TEST(BackoffEntrySerializerTest, DeserializeVersion2WrongDurationType) {
base::Value::List serialized;
serialized.Append(SerializationFormatVersion::kVersion2);
serialized.Append(0); // Failure count
serialized.Append(2.0); // Backoff duration
serialized.Append("1234"); // Absolute release time
auto deserialized = BackoffEntrySerializer::DeserializeFromList(
serialized, &base_policy, nullptr, kParseTime);
ASSERT_FALSE(deserialized);
}
} // namespace
} // namespace net
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