Merge pull request #5947

36cba8f Alert if it is very likely we are getting a bad chain (Gavin Andresen)

1 files changed, 59 insertions, 0 deletions

diff --git a/src/main.cpp b/src/main.cpp
index d3956fafda..ac7d50ce65 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -28,6 +28,7 @@
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>
+#include <boost/math/distributions/poisson.hpp>
 #include <boost/thread.hpp>
 
 using namespace std;
@@ -1685,6 +1686,64 @@ void ThreadScriptCheck() {
     scriptcheckqueue.Thread();
 }
 
+//
+// Called periodically asynchronously; alerts if it smells like
+// we're being fed a bad chain (blocks being generated much
+// too slowly or too quickly).
+//
+void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CChain& chain, int64_t nPowTargetSpacing)
+{
+    if (initialDownloadCheck()) return;
+
+    static int64_t lastAlertTime = 0;
+    int64_t now = GetAdjustedTime();
+    if (lastAlertTime > now-60*60*24) return; // Alert at most once per day
+
+    const int SPAN_HOURS=4;
+    const int SPAN_SECONDS=SPAN_HOURS*60*60;
+    int BLOCKS_EXPECTED = SPAN_SECONDS / nPowTargetSpacing;
+
+    boost::math::poisson_distribution<double> poisson(BLOCKS_EXPECTED);
+
+    std::string strWarning;
+    int64_t startTime = GetAdjustedTime()-SPAN_SECONDS;
+
+    LOCK(cs);
+    int h = chain.Height();
+    while (h > 0 && chain[h]->GetBlockTime() >= startTime)
+        --h;
+    int nBlocks = chain.Height()-h;
+
+    // How likely is it to find that many by chance?
+    double p = boost::math::pdf(poisson, nBlocks);
+
+    LogPrint("partitioncheck", "%s : Found %d blocks in the last %d hours\n", __func__, nBlocks, SPAN_HOURS);
+    LogPrint("partitioncheck", "%s : likelihood: %g\n", __func__, p);
+
+    // Aim for one false-positive about every fifty years of normal running:
+    const int FIFTY_YEARS = 50*365*24*60*60;
+    double alertThreshold = 1.0 / (FIFTY_YEARS / SPAN_SECONDS);
+
+    if (p <= alertThreshold && nBlocks < BLOCKS_EXPECTED)
+    {
+        // Many fewer blocks than expected: alert!
+        strWarning = strprintf(_("WARNING: check your network connection, %d blocks received in the last %d hours (%d expected)"),
+                               nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
+    }
+    else if (p <= alertThreshold && nBlocks > BLOCKS_EXPECTED)
+    {
+        // Many more blocks than expected: alert!
+        strWarning = strprintf(_("WARNING: abnormally high number of blocks generated, %d blocks received in the last %d hours (%d expected)"),
+                               nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
+    }
+    if (!strWarning.empty())
+    {
+        strMiscWarning = strWarning;
+        CAlert::Notify(strWarning, true);
+        lastAlertTime = now;
+    }
+}
+
 static int64_t nTimeVerify = 0;
 static int64_t nTimeConnect = 0;
 static int64_t nTimeIndex = 0;