timedata_tests.cpp

// Copyright (c) 2011-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
//

#include <netaddress.h>
#include <noui.h>
#include <util/string.h>
#include <test/util/logging.h>
#include <test/util/setup_common.h>
#include <timedata.h>
#include <warnings.h>

#include <string>

#include <boost/test/unit_test.hpp>

BOOST_FIXTURE_TEST_SUITE(timedata_tests, BasicTestingSetup)

BOOST_AUTO_TEST_CASE(util_MedianFilter)
{
    CMedianFilter<int> filter(5, 15);

    BOOST_CHECK_EQUAL(filter.median(), 15);

    filter.input(20); // [15 20]
    BOOST_CHECK_EQUAL(filter.median(), 17);

    filter.input(30); // [15 20 30]
    BOOST_CHECK_EQUAL(filter.median(), 20);

    filter.input(3); // [3 15 20 30]
    BOOST_CHECK_EQUAL(filter.median(), 17);

    filter.input(7); // [3 7 15 20 30]
    BOOST_CHECK_EQUAL(filter.median(), 15);

    filter.input(18); // [3 7 18 20 30]
    BOOST_CHECK_EQUAL(filter.median(), 18);

    filter.input(0); // [0 3 7 18 30]
    BOOST_CHECK_EQUAL(filter.median(), 7);
}

static void MultiAddTimeData(int n, int64_t offset)
{
    static int cnt = 0;
    for (int i = 0; i < n; ++i) {
        CNetAddr addr;
        addr.SetInternal(ToString(++cnt));
        AddTimeData(addr, offset);
    }
}


BOOST_AUTO_TEST_CASE(addtimedata)
{
    BOOST_CHECK_EQUAL(GetTimeOffset(), 0);

    //Part 1: Add large offsets to test a warning message that our clock may be wrong.
    MultiAddTimeData(3, DEFAULT_MAX_TIME_ADJUSTMENT + 1);
    // Filter size is 1 + 3 = 4: It is always initialized with a single element (offset 0)

    {
        ASSERT_DEBUG_LOG("Please check that your computer's date and time are correct!");
        MultiAddTimeData(1, DEFAULT_MAX_TIME_ADJUSTMENT + 1); //filter size 5
    }

    BOOST_CHECK(GetWarnings(true).find("clock is wrong") != std::string::npos);

    // nTimeOffset is not changed if the median of offsets exceeds DEFAULT_MAX_TIME_ADJUSTMENT
    BOOST_CHECK_EQUAL(GetTimeOffset(), 0);

    // Part 2: Test positive and negative medians by adding more offsets
    MultiAddTimeData(4, 100); // filter size 9
    BOOST_CHECK_EQUAL(GetTimeOffset(), 100);
    MultiAddTimeData(10, -100); //filter size 19
    BOOST_CHECK_EQUAL(GetTimeOffset(), -100);

    // Part 3: Test behaviour when filter has reached maximum number of offsets
    const int MAX_SAMPLES = 200;
    int nfill = (MAX_SAMPLES - 3 - 19) / 2; //89
    MultiAddTimeData(nfill, 100);
    MultiAddTimeData(nfill, -100); //filter size MAX_SAMPLES - 3
    BOOST_CHECK_EQUAL(GetTimeOffset(), -100);

    MultiAddTimeData(2, 100);
    //filter size MAX_SAMPLES -1, median is the initial 0 offset
    //since we added same number of positive/negative offsets

    BOOST_CHECK_EQUAL(GetTimeOffset(), 0);

    // After the number of offsets has reached MAX_SAMPLES -1 (=199), nTimeOffset will never change
    // because it is only updated when the number of elements in the filter becomes odd. It was decided
    // not to fix this because it prevents possible attacks. See the comment in AddTimeData() or issue #4521
    // for a more detailed explanation.
    MultiAddTimeData(2, 100); // filter median is 100 now, but nTimeOffset will not change
    BOOST_CHECK_EQUAL(GetTimeOffset(), 0);

    // We want this test to end with nTimeOffset==0, otherwise subsequent tests of the suite will fail.
}

BOOST_AUTO_TEST_SUITE_END()