From 6eed52e05b697547105e7f6ab2419a3b1bf50189 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Mon, 27 Jul 2015 18:58:00 +0200
Subject: [PATCH] Only use randomly created nonces in CRollingBloomFilter.

(cherry picked from commit d741371d7d27e228aa64c618c50b23fb5449c3e1)
---
 src/bloom.cpp            | 13 ++++++-------
 src/bloom.h              |  8 +++++---
 src/test/bloom_tests.cpp |  6 +++---
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/bloom.cpp b/src/bloom.cpp
index 89959d732..de8720659 100644
--- a/src/bloom.cpp
+++ b/src/bloom.cpp
@@ -216,16 +216,17 @@ void CBloomFilter::UpdateEmptyFull()
     isEmpty = empty;
 }
 
-CRollingBloomFilter::CRollingBloomFilter(unsigned int nElements, double fpRate, unsigned int nTweak) :
-    b1(nElements * 2, fpRate, nTweak), b2(nElements * 2, fpRate, nTweak)
+CRollingBloomFilter::CRollingBloomFilter(unsigned int nElements, double fpRate) :
+    b1(nElements * 2, fpRate, 0), b2(nElements * 2, fpRate, 0)
 {
     // Implemented using two bloom filters of 2 * nElements each.
     // We fill them up, and clear them, staggered, every nElements
     // inserted, so at least one always contains the last nElements
     // inserted.
+    nInsertions = 0;
     nBloomSize = nElements * 2;
 
-    reset(nTweak);
+    reset();
 }
 
 void CRollingBloomFilter::insert(const std::vector<unsigned char>& vKey)
@@ -262,11 +263,9 @@ bool CRollingBloomFilter::contains(const uint256& hash) const
     return contains(data);
 }
 
-void CRollingBloomFilter::reset(unsigned int nNewTweak)
+void CRollingBloomFilter::reset()
 {
-    if (!nNewTweak)
-        nNewTweak = GetRand(std::numeric_limits<unsigned int>::max());
-
+    unsigned int nNewTweak = GetRand(std::numeric_limits<unsigned int>::max());
     b1.reset(nNewTweak);
     b2.reset(nNewTweak);
     nInsertions = 0;
diff --git a/src/bloom.h b/src/bloom.h
index 12bf6d99a..a4dba8cb4 100644
--- a/src/bloom.h
+++ b/src/bloom.h
@@ -116,15 +116,17 @@ public:
 class CRollingBloomFilter
 {
 public:
-    CRollingBloomFilter(unsigned int nElements, double nFPRate,
-                        unsigned int nTweak = 0);
+    // A random bloom filter calls GetRand() at creation time.
+    // Don't create global CRollingBloomFilter objects, as they may be
+    // constructed before the randomizer is properly initialized.
+    CRollingBloomFilter(unsigned int nElements, double nFPRate);
 
     void insert(const std::vector<unsigned char>& vKey);
     void insert(const uint256& hash);
     bool contains(const std::vector<unsigned char>& vKey) const;
     bool contains(const uint256& hash) const;
 
-    void reset(unsigned int nNewTweak = 0);
+    void reset();
 
 private:
     unsigned int nBloomSize;
diff --git a/src/test/bloom_tests.cpp b/src/test/bloom_tests.cpp
index d927be6b8..6b30d6aa8 100644
--- a/src/test/bloom_tests.cpp
+++ b/src/test/bloom_tests.cpp
@@ -469,7 +469,7 @@ static std::vector<unsigned char> RandomData()
 BOOST_AUTO_TEST_CASE(rolling_bloom)
 {
     // last-100-entry, 1% false positive:
-    CRollingBloomFilter rb1(100, 0.01, 1);
+    CRollingBloomFilter rb1(100, 0.01);
 
     // Overfill:
     static const int DATASIZE=399;
@@ -500,7 +500,7 @@ BOOST_AUTO_TEST_CASE(rolling_bloom)
     BOOST_CHECK(nHits < 175);
 
     BOOST_CHECK(rb1.contains(data[DATASIZE-1]));
-    rb1.reset(1);
+    rb1.reset();
     BOOST_CHECK(!rb1.contains(data[DATASIZE-1]));
 
     // Now roll through data, make sure last 100 entries
@@ -527,7 +527,7 @@ BOOST_AUTO_TEST_CASE(rolling_bloom)
     BOOST_CHECK(nHits < 100);
 
     // last-1000-entry, 0.01% false positive:
-    CRollingBloomFilter rb2(1000, 0.001, 1);
+    CRollingBloomFilter rb2(1000, 0.001);
     for (int i = 0; i < DATASIZE; i++) {
         rb2.insert(data[i]);
     }