118 lines
3.8 KiB
C++
118 lines
3.8 KiB
C++
// Copyright (c) 2014-2016 The Bitcoin Core developers
|
|
// Distributed under the MIT software license, see the accompanying
|
|
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
|
|
|
|
#if defined(HAVE_CONFIG_H)
|
|
#include "config/bitcoin-config.h"
|
|
#endif
|
|
|
|
#include "timedata.h"
|
|
|
|
#include "netaddress.h"
|
|
#include "sync.h"
|
|
#include "ui_interface.h"
|
|
#include "util.h"
|
|
#include "utilstrencodings.h"
|
|
#include "warnings.h"
|
|
|
|
#include <boost/foreach.hpp>
|
|
|
|
static CCriticalSection cs_nTimeOffset;
|
|
static int64_t nTimeOffset = 0;
|
|
|
|
/**
|
|
* "Never go to sea with two chronometers; take one or three."
|
|
* Our three time sources are:
|
|
* - System clock
|
|
* - Median of other nodes clocks
|
|
* - The user (asking the user to fix the system clock if the first two disagree)
|
|
*/
|
|
int64_t GetTimeOffset()
|
|
{
|
|
LOCK(cs_nTimeOffset);
|
|
return nTimeOffset;
|
|
}
|
|
|
|
int64_t GetAdjustedTime()
|
|
{
|
|
return GetTime() + GetTimeOffset();
|
|
}
|
|
|
|
static int64_t abs64(int64_t n)
|
|
{
|
|
return (n >= 0 ? n : -n);
|
|
}
|
|
|
|
#define BITCOIN_TIMEDATA_MAX_SAMPLES 200
|
|
|
|
void AddTimeData(const CNetAddr& ip, int64_t nOffsetSample)
|
|
{
|
|
LOCK(cs_nTimeOffset);
|
|
// Ignore duplicates
|
|
static std::set<CNetAddr> setKnown;
|
|
if (setKnown.size() == BITCOIN_TIMEDATA_MAX_SAMPLES)
|
|
return;
|
|
if (!setKnown.insert(ip).second)
|
|
return;
|
|
|
|
// Add data
|
|
static CMedianFilter<int64_t> vTimeOffsets(BITCOIN_TIMEDATA_MAX_SAMPLES, 0);
|
|
vTimeOffsets.input(nOffsetSample);
|
|
LogPrint("net","added time data, samples %d, offset %+d (%+d minutes)\n", vTimeOffsets.size(), nOffsetSample, nOffsetSample/60);
|
|
|
|
// There is a known issue here (see issue #4521):
|
|
//
|
|
// - The structure vTimeOffsets contains up to 200 elements, after which
|
|
// any new element added to it will not increase its size, replacing the
|
|
// oldest element.
|
|
//
|
|
// - The condition to update nTimeOffset includes checking whether the
|
|
// number of elements in vTimeOffsets is odd, which will never happen after
|
|
// there are 200 elements.
|
|
//
|
|
// But in this case the 'bug' is protective against some attacks, and may
|
|
// actually explain why we've never seen attacks which manipulate the
|
|
// clock offset.
|
|
//
|
|
// So we should hold off on fixing this and clean it up as part of
|
|
// a timing cleanup that strengthens it in a number of other ways.
|
|
//
|
|
if (vTimeOffsets.size() >= 5 && vTimeOffsets.size() % 2 == 1)
|
|
{
|
|
int64_t nMedian = vTimeOffsets.median();
|
|
std::vector<int64_t> vSorted = vTimeOffsets.sorted();
|
|
// Only let other nodes change our time by so much
|
|
if (abs64(nMedian) <= std::max<int64_t>(0, GetArg("-maxtimeadjustment", DEFAULT_MAX_TIME_ADJUSTMENT)))
|
|
{
|
|
nTimeOffset = nMedian;
|
|
}
|
|
else
|
|
{
|
|
nTimeOffset = 0;
|
|
|
|
static bool fDone;
|
|
if (!fDone)
|
|
{
|
|
// If nobody has a time different than ours but within 5 minutes of ours, give a warning
|
|
bool fMatch = false;
|
|
BOOST_FOREACH(int64_t nOffset, vSorted)
|
|
if (nOffset != 0 && abs64(nOffset) < 5 * 60)
|
|
fMatch = true;
|
|
|
|
if (!fMatch)
|
|
{
|
|
fDone = true;
|
|
std::string strMessage = strprintf(_("Please check that your computer's date and time are correct! If your clock is wrong, %s will not work properly."), _(PACKAGE_NAME));
|
|
SetMiscWarning(strMessage);
|
|
uiInterface.ThreadSafeMessageBox(strMessage, "", CClientUIInterface::MSG_WARNING);
|
|
}
|
|
}
|
|
}
|
|
|
|
BOOST_FOREACH(int64_t n, vSorted)
|
|
LogPrint("net", "%+d ", n);
|
|
LogPrint("net", "| ");
|
|
|
|
LogPrint("net", "nTimeOffset = %+d (%+d minutes)\n", nTimeOffset, nTimeOffset/60);
|
|
}
|
|
}
|