1 files changed, 47 insertions, 0 deletions
diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index 2fec6b613..735309aa9 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -1494,6 +1494,7 @@ namespace cryptonote
     m_txpool_auto_relayer.do_call(boost::bind(&core::relay_txpool_transactions, this));
     m_check_updates_interval.do_call(boost::bind(&core::check_updates, this));
     m_check_disk_space_interval.do_call(boost::bind(&core::check_disk_space, this));
+    m_block_rate_interval.do_call(boost::bind(&core::check_block_rate, this));
     m_miner.on_idle();
     m_mempool.on_idle();
     return true;
@@ -1682,6 +1683,52 @@ namespace cryptonote
     return true;
   }
   //-----------------------------------------------------------------------------------------------
+  double factorial(unsigned int n)
+  {
+    if (n <= 1)
+      return 1.0;
+    double f = n;
+    while (n-- > 1)
+      f *= n;
+    return f;
+  }
+  //-----------------------------------------------------------------------------------------------
+  static double probability(unsigned int blocks, unsigned int expected)
+  {
+    // https://www.umass.edu/wsp/resources/poisson/#computing
+    return pow(expected, blocks) / (factorial(blocks) * exp(expected));
+  }
+  //-----------------------------------------------------------------------------------------------
+  bool core::check_block_rate()
+  {
+    if (m_offline || m_target_blockchain_height > get_current_blockchain_height())
+    {
+      MDEBUG("Not checking block rate, offline or syncing");
+      return true;
+    }
+
+    static constexpr double threshold = 1. / (864000 / DIFFICULTY_TARGET_V2); // one false positive every 10 days
+
+    const time_t now = time(NULL);
+    const std::vector<time_t> timestamps = m_blockchain_storage.get_last_block_timestamps(60);
+
+    static const unsigned int seconds[] = { 5400, 1800, 600 };
+    for (size_t n = 0; n < sizeof(seconds)/sizeof(seconds[0]); ++n)
+    {
+      unsigned int b = 0;
+      for (time_t ts: timestamps) b += ts >= now - seconds[n];
+      const double p = probability(b, seconds[n] / DIFFICULTY_TARGET_V2);
+      MDEBUG("blocks in the last " << seconds[n] / 60 << " minutes: " << b << " (probability " << p << ")");
+      if (p < threshold)
+      {
+        MWARNING("There were " << b << " blocks in the last " << seconds[n] / 60 << " minutes, there might be large hash rate changes, or we might be partitioned, cut off from the Monero network or under attack. Or it could be just sheer bad luck.");
+        break; // no need to look further
+      }
+    }
+
+    return true;
+  }
+  //-----------------------------------------------------------------------------------------------
   void core::set_target_blockchain_height(uint64_t target_blockchain_height)
   {
     m_target_blockchain_height = target_blockchain_height;