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authorGregory Maxwell <greg@xiph.org>2013-08-18 20:21:06 -0700
committerGregory Maxwell <greg@xiph.org>2013-08-20 02:27:26 -0700
commit37c6389c5a0ca63ae3573440ecdfe95d28ad8f07 (patch)
tree51ef4367b16dc75bd60d4de0da261b65cebf4f2d
parent4bc9a192696273c88966c39debf8d17f16ebe471 (diff)
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.
-rw-r--r--src/bloom.cpp26
-rw-r--r--src/bloom.h9
-rw-r--r--src/main.cpp3
-rw-r--r--src/net.h2
4 files changed, 33 insertions, 7 deletions
diff --git a/src/bloom.cpp b/src/bloom.cpp
index b6799e143d..8e8d8fa06b 100644
--- a/src/bloom.cpp
+++ b/src/bloom.cpp
@@ -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;
+}
diff --git a/src/bloom.h b/src/bloom.h
index 389ae748e6..f482bfcc10 100644
--- a/src/bloom.h
+++ b/src/bloom.h
@@ -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 */
diff --git a/src/main.cpp b/src/main.cpp
index 2ccd5131d1..b62f107b4c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -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;
}
diff --git a/src/net.h b/src/net.h
index e75fe48f64..686861fbeb 100644
--- a/src/net.h
+++ b/src/net.h
@@ -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)