Merge pull request #6534

7bd66b01b daemon: guard against rare 'difficulty drift' bug with checkpoints and recalculation (stoffu)

src/blockchain_db/lmdb/db_lmdb.cpp

@@ -2750,6 +2750,44 @@ difficulty_type BlockchainLMDB::get_block_difficulty(const uint64_t& height) con
   return diff1 - diff2;
 }
 
+void BlockchainLMDB::correct_block_cumulative_difficulties(const uint64_t& start_height, const std::vector<difficulty_type>& new_cumulative_difficulties)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+  mdb_txn_cursors *m_cursors = &m_wcursors;
+
+  int result = 0;
+  block_wtxn_start();
+  CURSOR(block_info)
+
+  const uint64_t bc_height = height();
+  if (start_height + new_cumulative_difficulties.size() != bc_height)
+  {
+    block_wtxn_abort();
+    throw0(DB_ERROR("Incorrect new_cumulative_difficulties size"));
+  }
+
+  for (uint64_t height = start_height; height < bc_height; ++height)
+  {
+    MDB_val_set(key, height);
+    result = mdb_cursor_get(m_cur_block_info, (MDB_val *)&zerokval, &key, MDB_GET_BOTH);
+    if (result)
+      throw1(BLOCK_DNE(lmdb_error("Failed to get block info: ", result).c_str()));
+
+    mdb_block_info bi = *(mdb_block_info*)key.mv_data;
+    const difficulty_type d = new_cumulative_difficulties[height - start_height];
+    bi.bi_diff_hi = ((d >> 64) & 0xffffffffffffffff).convert_to<uint64_t>();
+    bi.bi_diff_lo = (d & 0xffffffffffffffff).convert_to<uint64_t>();
+
+    MDB_val_set(key2, height);
+    MDB_val_set(val, bi);
+    result = mdb_cursor_put(m_cur_block_info, &key2, &val, MDB_CURRENT);
+    if (result)
+      throw0(DB_ERROR(lmdb_error("Failed to overwrite block info to db transaction: ", result).c_str()));
+  }
+  block_wtxn_stop();
+}
+
 uint64_t BlockchainLMDB::get_block_already_generated_coins(const uint64_t& height) const
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);

src/blockchain_db/lmdb/db_lmdb.h

@@ -229,6 +229,8 @@ public:
 
   virtual difficulty_type get_block_difficulty(const uint64_t& height) const;
 
+  virtual void correct_block_cumulative_difficulties(const uint64_t& start_height, const std::vector<difficulty_type>& new_cumulative_difficulties);
+
   virtual uint64_t get_block_already_generated_coins(const uint64_t& height) const;
 
   virtual uint64_t get_block_long_term_weight(const uint64_t& height) const;