use median filter for peer-reported reported number of blocks

- fixes problem that one misconfigured or malicious node can mess up progress bar
- implementation in src/util.h
- testcase in src/test/util_tests.cpp
This commit is contained in:
Wladimir J. van der Laan 2011-09-28 21:35:58 +02:00
parent 5902040874
commit a8b95ce6ed
3 changed files with 85 additions and 11 deletions

View file

@ -32,7 +32,6 @@ uint256 hashGenesisBlock("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3
static CBigNum bnProofOfWorkLimit(~uint256(0) >> 32);
const int nTotalBlocksEstimate = 140700; // Conservative estimate of total nr of blocks on main chain
const int nInitialBlockThreshold = 120; // Regard blocks up until N-threshold as "initial download"
int nMaxBlocksOfPeers = 0; // Amount of blocks that other nodes claim to have
CBlockIndex* pindexGenesisBlock = NULL;
int nBestHeight = -1;
CBigNum bnBestChainWork = 0;
@ -41,6 +40,8 @@ uint256 hashBestChain = 0;
CBlockIndex* pindexBest = NULL;
int64 nTimeBestReceived = 0;
CMedianFilter<int> cPeerBlockCounts(5, 0); // Amount of blocks that other nodes claim to have
map<uint256, CBlock*> mapOrphanBlocks;
multimap<uint256, CBlock*> mapOrphanBlocksByPrev;
@ -65,11 +66,6 @@ int fUseUPnP = false;
#endif
//////////////////////////////////////////////////////////////////////////////
//
// dispatching functions
@ -730,7 +726,7 @@ int GetTotalBlocksEstimate()
// Return maximum amount of blocks that other nodes claim to have
int GetNumBlocksOfPeers()
{
return std::max(nMaxBlocksOfPeers, GetTotalBlocksEstimate());
return std::max(cPeerBlockCounts.median(), GetTotalBlocksEstimate());
}
bool IsInitialBlockDownload()
@ -1847,10 +1843,8 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
pfrom->fSuccessfullyConnected = true;
printf("version message: version %d, blocks=%d\n", pfrom->nVersion, pfrom->nStartingHeight);
if(pfrom->nStartingHeight > nMaxBlocksOfPeers)
{
nMaxBlocksOfPeers = pfrom->nStartingHeight;
}
cPeerBlockCounts.input(pfrom->nStartingHeight);
}

36
src/test/util_tests.cpp Normal file
View file

@ -0,0 +1,36 @@
#include <vector>
#include <boost/test/unit_test.hpp>
#include <boost/foreach.hpp>
#include "../util.h"
using namespace std;
BOOST_AUTO_TEST_SUITE(util_tests)
BOOST_AUTO_TEST_CASE(util_MedianFilter)
{
CMedianFilter<int> filter(5, 15);
BOOST_CHECK(filter.median() == 15);
filter.input(20); // [15 20]
BOOST_CHECK(filter.median() == 17);
filter.input(30); // [15 20 30]
BOOST_CHECK(filter.median() == 20);
filter.input(3); // [3 15 20 30]
BOOST_CHECK(filter.median() == 17);
filter.input(7); // [3 7 15 20 30]
BOOST_CHECK(filter.median() == 15);
filter.input(18); // [3 7 18 20 30]
BOOST_CHECK(filter.median() == 18);
filter.input(0); // [0 3 7 18 30]
BOOST_CHECK(filter.median() == 7);
}
BOOST_AUTO_TEST_SUITE_END()

View file

@ -565,6 +565,50 @@ inline uint160 Hash160(const std::vector<unsigned char>& vch)
}
// Median filter over a stream of values
// Returns the median of the last N numbers
template <typename T> class CMedianFilter
{
private:
std::vector<T> vValues;
std::vector<T> vSorted;
int nSize;
public:
CMedianFilter(int size, T initial_value):
nSize(size)
{
vValues.reserve(size);
vValues.push_back(initial_value);
vSorted = vValues;
}
void input(T value)
{
if(vValues.size() == nSize)
{
vValues.erase(vValues.begin());
}
vValues.push_back(value);
vSorted.resize(vValues.size());
std::copy(vValues.begin(), vValues.end(), vSorted.begin());
std::sort(vSorted.begin(), vSorted.end());
}
T median() const
{
int size = vSorted.size();
if(size & 1) // Odd number of elements
{
return vSorted[size/2];
}
else // Even number of elements
{
return (vSorted[size/2-1] + vSorted[size/2]) / 2;
}
}
};