blockchain: pop top if block version disagrees with the ideal fork version

src/cryptonote_core/blockchain.cpp

@@ -415,6 +415,53 @@ bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline
   MINFO("Blockchain initialized. last block: " << m_db->height() - 1 << ", " << epee::misc_utils::get_time_interval_string(timestamp_diff) << " time ago, current difficulty: " << get_difficulty_for_next_block());
   m_db->block_txn_stop();
 
+  uint64_t num_popped_blocks = 0;
+  while (true)
+  {
+    const uint64_t top_height = m_db->height() - 1;
+    const crypto::hash top_id = m_db->top_block_hash();
+    const block top_block = m_db->get_top_block();
+    const uint8_t ideal_hf_version = get_ideal_hard_fork_version(top_height);
+    if (ideal_hf_version <= 1 || ideal_hf_version == top_block.major_version)
+    {
+      if (num_popped_blocks > 0)
+        MGINFO("Initial popping done, top block: " << top_id << ", top height: " << top_height << ", block version: " << (uint64_t)top_block.major_version);
+      break;
+    }
+    else
+    {
+      if (num_popped_blocks == 0)
+        MGINFO("Current top block " << top_id << " at height " << top_height << " has version " << (uint64_t)top_block.major_version << " which disagrees with the ideal version " << (uint64_t)ideal_hf_version);
+      if (num_popped_blocks % 100 == 0)
+        MGINFO("Popping blocks... " << top_height);
+      ++num_popped_blocks;
+      block popped_block;
+      std::vector<transaction> popped_txs;
+      try
+      {
+        m_db->pop_block(popped_block, popped_txs);
+      }
+      // anything that could cause this to throw is likely catastrophic,
+      // so we re-throw
+      catch (const std::exception& e)
+      {
+        MERROR("Error popping block from blockchain: " << e.what());
+        throw;
+      }
+      catch (...)
+      {
+        MERROR("Error popping block from blockchain, throwing!");
+        throw;
+      }
+    }
+  }
+  if (num_popped_blocks > 0)
+  {
+    m_timestamps_and_difficulties_height = 0;
+    m_hardfork->reorganize_from_chain_height(get_current_blockchain_height());
+    m_tx_pool.on_blockchain_dec(m_db->height()-1, get_tail_id());
+  }
+
   update_next_cumulative_size_limit();
   return true;
 }