Modify PartitionCheck to be aware of pre & post Blossom target spacing.

src/init.cpp

@@ -1861,11 +1861,10 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
 
     StartNode(threadGroup, scheduler);
 
-    // Monitor the chain, and alert if we get blocks much quicker or slower than expected
-    int64_t nPowTargetSpacing = Params().GetConsensus().nPowTargetSpacing;
+    // Monitor the chain every minute, and alert if we get blocks much quicker or slower than expected.
     CScheduler::Function f = boost::bind(&PartitionCheck, &IsInitialBlockDownload,
-                                         boost::ref(cs_main), boost::cref(pindexBestHeader), nPowTargetSpacing);
-    scheduler.scheduleEvery(f, nPowTargetSpacing);
+                                         boost::ref(cs_main), boost::cref(pindexBestHeader), 0);
+    scheduler.scheduleEvery(f, 60);
 
 #ifdef ENABLE_MINING
     // Generate coins in the background

src/main.cpp

@@ -2436,6 +2436,9 @@ void ThreadScriptCheck() {
 // we're being fed a bad chain (blocks being generated much
 // too slowly or too quickly).
 //
+// When parameter nPowTargetSpacing is not set, the default value of 0
+// means use the block height of the best header to determine target spacing.
+// Setting the parameter value is useful for testing.
 void PartitionCheck(bool (*initialDownloadCheck)(const CChainParams&),
                     CCriticalSection& cs, const CBlockIndex *const &bestHeader,
                     int64_t nPowTargetSpacing)
@@ -2448,14 +2451,36 @@ void PartitionCheck(bool (*initialDownloadCheck)(const CChainParams&),
 
     const int SPAN_HOURS=4;
     const int SPAN_SECONDS=SPAN_HOURS*60*60;
+
+    LOCK(cs);
+
+    int bestHeaderHeight = bestHeader->nHeight;
+    int blossomHeight = Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
+    if (nPowTargetSpacing == 0) {
+        nPowTargetSpacing = Params().GetConsensus().PoWTargetSpacing(bestHeaderHeight);
+        blossomHeight = Params().GetConsensus().vUpgrades[Consensus::UPGRADE_BLOSSOM].nActivationHeight;
+    }
+
     int BLOCKS_EXPECTED = SPAN_SECONDS / nPowTargetSpacing;
 
+    // If the span period includes Blossom activation, adjust the number of expected blocks.
+    if (blossomHeight != Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT &&
+        bestHeaderHeight > blossomHeight)
+    {
+        int t = SPAN_SECONDS;
+        int nBlossomBlocks = bestHeaderHeight - blossomHeight;
+        t -= nBlossomBlocks * Consensus::POST_BLOSSOM_POW_TARGET_SPACING;
+        if (t > 0) {
+            int nPreBlossomBlocks = t / Consensus::PRE_BLOSSOM_POW_TARGET_SPACING;
+            BLOCKS_EXPECTED = nPreBlossomBlocks + nBlossomBlocks;
+        }
+    }
+
     boost::math::poisson_distribution<double> poisson(BLOCKS_EXPECTED);
 
     std::string strWarning;
     int64_t startTime = GetAdjustedTime()-SPAN_SECONDS;
 
-    LOCK(cs);
     const CBlockIndex* i = bestHeader;
     int nBlocks = 0;
     while (i->GetBlockTime() >= startTime) {

src/main.h

@@ -234,7 +234,7 @@ bool SendMessages(CNode* pto, bool fSendTrickle);
 /** Run an instance of the script checking thread */
 void ThreadScriptCheck();
 /** Try to detect Partition (network isolation) attacks against us */
-void PartitionCheck(bool (*initialDownloadCheck)(const CChainParams&), CCriticalSection& cs, const CBlockIndex *const &bestHeader, int64_t nPowTargetSpacing);
+void PartitionCheck(bool (*initialDownloadCheck)(const CChainParams&), CCriticalSection& cs, const CBlockIndex *const &bestHeader, int64_t nPowTargetSpacing = 0);
 /** Check whether we are doing an initial block download (synchronizing from disk or network) */
 bool IsInitialBlockDownload(const CChainParams& chainParams);
 /** Format a string that describes several potential problems detected by the core */