Closes #3134 - Least Authority Issue E

CTxMemPool::check() does nothing when turned on, due to overflow.

src/test/mempool_tests.cpp

@@ -212,4 +212,14 @@ BOOST_AUTO_TEST_CASE(RemoveWithoutBranchId) {
     BOOST_CHECK_EQUAL(pool.size(), 0);
 }
 
+// Test that nCheckFrequency is set correctly when calling setSanityCheck().
+// https://github.com/zcash/zcash/issues/3134
+BOOST_AUTO_TEST_CASE(SetSanityCheck) {
+    CTxMemPool pool(CFeeRate(0));
+    pool.setSanityCheck(1.0);
+    BOOST_CHECK_EQUAL(pool.GetCheckFrequency(), 4294967295);
+    pool.setSanityCheck(0);
+    BOOST_CHECK_EQUAL(pool.GetCheckFrequency(), 0);
+}
+
 BOOST_AUTO_TEST_SUITE_END()

src/txmempool.h

@@ -161,7 +161,7 @@ public:
      * check does nothing.
      */
     void check(const CCoinsViewCache *pcoins) const;
-    void setSanityCheck(double dFrequency = 1.0) { nCheckFrequency = dFrequency * 4294967296.0; }
+    void setSanityCheck(double dFrequency = 1.0) { nCheckFrequency = static_cast<uint32_t>(dFrequency * 4294967295.0); }
 
     bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, bool fCurrentEstimate = true);
     void remove(const CTransaction &tx, std::list<CTransaction>& removed, bool fRecursive = false);
@@ -219,6 +219,11 @@ public:
     bool ReadFeeEstimates(CAutoFile& filein);
 
     size_t DynamicMemoryUsage() const;
+
+    /** Return nCheckFrequency */
+    uint32_t GetCheckFrequency() const {
+        return nCheckFrequency;
+    }
 };
 
 /**