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Performance optimization for bloom filters.

This reduces a peer's ability to attack network resources by
 using a full bloom filter, but without reducing the usability
 of bloom filters.  It sets a default match everything filter
 for peers and it generalizes a prior optimization to
 cover more cases.
tags/v0.15.1
Gregory Maxwell 7 years ago
parent
commit
37c6389c5a
4 changed files with 33 additions and 7 deletions
  1. 24
    2
      src/bloom.cpp
  2. 6
    3
      src/bloom.h
  3. 2
    1
      src/main.cpp
  4. 1
    1
      src/net.h

+ 24
- 2
src/bloom.cpp View File

@@ -23,6 +23,8 @@ vData(min((unsigned int)(-1 / LN2SQUARED * nElements * log(nFPRate)), MAX_BLOOM
// The ideal number of hash functions is filter size * ln(2) / number of elements
// Again, we ignore filter parameters which will create a bloom filter with more hash functions than the protocol limits
// See http://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas
isFull(false),
isEmpty(false),
nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS)),
nTweak(nTweakIn),
nFlags(nFlagsIn)
@@ -37,7 +39,7 @@ inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<

void CBloomFilter::insert(const vector<unsigned char>& vKey)
{
if (vData.size() == 1 && vData[0] == 0xff)
if (isFull)
return;
for (unsigned int i = 0; i < nHashFuncs; i++)
{
@@ -45,6 +47,7 @@ void CBloomFilter::insert(const vector<unsigned char>& vKey)
// Sets bit nIndex of vData
vData[nIndex >> 3] |= bit_mask[7 & nIndex];
}
isEmpty = false;
}

void CBloomFilter::insert(const COutPoint& outpoint)
@@ -63,8 +66,10 @@ void CBloomFilter::insert(const uint256& hash)

bool CBloomFilter::contains(const vector<unsigned char>& vKey) const
{
if (vData.size() == 1 && vData[0] == 0xff)
if (isFull)
return true;
if (isEmpty)
return false;
for (unsigned int i = 0; i < nHashFuncs; i++)
{
unsigned int nIndex = Hash(i, vKey);
@@ -99,6 +104,10 @@ bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx, const uint256& ha
bool fFound = false;
// Match if the filter contains the hash of tx
// for finding tx when they appear in a block
if (isFull)
return true;
if (isEmpty)
return false;
if (contains(hash))
fFound = true;

@@ -158,3 +167,16 @@ bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx, const uint256& ha

return false;
}

void CBloomFilter::UpdateEmptyFull()
{
bool full = true;
bool empty = true;
for (unsigned int i = 0; i < vData.size(); i++)
{
full &= vData[i] == 0xff;
empty &= vData[i] == 0;
}
isFull = full;
isEmpty = empty;
}

+ 6
- 3
src/bloom.h View File

@@ -42,6 +42,8 @@ class CBloomFilter
{
private:
std::vector<unsigned char> vData;
bool isFull;
bool isEmpty;
unsigned int nHashFuncs;
unsigned int nTweak;
unsigned char nFlags;
@@ -57,9 +59,7 @@ public:
// It should generally always be a random value (and is largely only exposed for unit testing)
// nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK)
CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn);
// Using a filter initialized with this results in undefined behavior
// Should only be used for deserialization
CBloomFilter() {}
CBloomFilter() : isFull(true) {}

IMPLEMENT_SERIALIZE
(
@@ -83,6 +83,9 @@ public:

// Also adds any outputs which match the filter to the filter (to match their spending txes)
bool IsRelevantAndUpdate(const CTransaction& tx, const uint256& hash);

// Checks for empty and full filters to avoid wasting cpu
void UpdateEmptyFull();
};

#endif /* BITCOIN_BLOOM_H */

+ 2
- 1
src/main.cpp View File

@@ -3893,6 +3893,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
LOCK(pfrom->cs_filter);
delete pfrom->pfilter;
pfrom->pfilter = new CBloomFilter(filter);
filter.UpdateEmptyFull();
}
pfrom->fRelayTxes = true;
}
@@ -3922,7 +3923,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
{
LOCK(pfrom->cs_filter);
delete pfrom->pfilter;
pfrom->pfilter = NULL;
pfrom->pfilter = new CBloomFilter();
pfrom->fRelayTxes = true;
}


+ 1
- 1
src/net.h View File

@@ -267,7 +267,7 @@ public:
nMisbehavior = 0;
fRelayTxes = false;
setInventoryKnown.max_size(SendBufferSize() / 1000);
pfilter = NULL;
pfilter = new CBloomFilter();

// Be shy and don't send version until we hear
if (hSocket != INVALID_SOCKET && !fInbound)

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