From 7bd66b01bfb62ecaf8ff02b20d14db3a77322abc Mon Sep 17 00:00:00 2001 From: stoffu Date: Fri, 15 May 2020 10:56:23 +0900 Subject: daemon: guard against rare 'difficulty drift' bug with checkpoints and recalculation On startup, it checks against the difficulty checkpoints, and if any mismatch is found, recalculates all the blocks with wrong difficulties. Additionally, once a week it recalculates difficulties of blocks after the last difficulty checkpoint. --- src/cryptonote_core/blockchain.cpp | 115 +++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) (limited to 'src/cryptonote_core/blockchain.cpp') diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp index fb2c71a3a..cad4620d2 100644 --- a/src/cryptonote_core/blockchain.cpp +++ b/src/cryptonote_core/blockchain.cpp @@ -32,6 +32,7 @@ #include #include #include +#include #include "include_base_utils.h" #include "cryptonote_basic/cryptonote_basic_impl.h" @@ -439,6 +440,15 @@ bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline m_long_term_block_weights_cache_rolling_median = epee::misc_utils::rolling_median_t(m_long_term_block_weights_window); } + bool difficulty_ok; + uint64_t difficulty_recalc_height; + std::tie(difficulty_ok, difficulty_recalc_height) = check_difficulty_checkpoints(); + if (!difficulty_ok) + { + MERROR("Difficulty drift detected!"); + recalculate_difficulties(difficulty_recalc_height); + } + { db_txn_guard txn_guard(m_db, m_db->is_read_only()); if (!update_next_cumulative_weight_limit()) @@ -888,6 +898,111 @@ difficulty_type Blockchain::get_difficulty_for_next_block() return diff; } //------------------------------------------------------------------ +std::pair Blockchain::check_difficulty_checkpoints() const +{ + uint64_t res = 0; + for (const std::pair& i : m_checkpoints.get_difficulty_points()) + { + if (i.first >= m_db->height()) + break; + if (m_db->get_block_cumulative_difficulty(i.first) != i.second) + return {false, res}; + res = i.first; + } + return {true, res}; +} +//------------------------------------------------------------------ +size_t Blockchain::recalculate_difficulties(boost::optional start_height_opt) +{ + if (m_fixed_difficulty) + { + return 0; + } + LOG_PRINT_L3("Blockchain::" << __func__); + CRITICAL_REGION_LOCAL(m_blockchain_lock); + + const uint64_t start_height = start_height_opt ? *start_height_opt : check_difficulty_checkpoints().second; + const uint64_t top_height = m_db->height() - 1; + MGINFO("Recalculating difficulties from height " << start_height << " to height " << top_height); + + std::vector timestamps; + std::vector difficulties; + timestamps.reserve(DIFFICULTY_BLOCKS_COUNT + 1); + difficulties.reserve(DIFFICULTY_BLOCKS_COUNT + 1); + if (start_height > 1) + { + for (uint64_t i = 0; i < DIFFICULTY_BLOCKS_COUNT; ++i) + { + uint64_t height = start_height - 1 - i; + if (height == 0) + break; + timestamps.insert(timestamps.begin(), m_db->get_block_timestamp(height)); + difficulties.insert(difficulties.begin(), m_db->get_block_cumulative_difficulty(height)); + } + } + difficulty_type last_cum_diff = start_height <= 1 ? start_height : difficulties.back(); + uint64_t drift_start_height = 0; + std::vector new_cumulative_difficulties; + for (uint64_t height = start_height; height <= top_height; ++height) + { + size_t target = get_ideal_hard_fork_version(height) < 2 ? DIFFICULTY_TARGET_V1 : DIFFICULTY_TARGET_V2; + difficulty_type recalculated_diff = next_difficulty(timestamps, difficulties, target); + + boost::multiprecision::uint256_t recalculated_cum_diff_256 = boost::multiprecision::uint256_t(recalculated_diff) + last_cum_diff; + CHECK_AND_ASSERT_THROW_MES(recalculated_cum_diff_256 <= std::numeric_limits::max(), "Difficulty overflow!"); + difficulty_type recalculated_cum_diff = recalculated_cum_diff_256.convert_to(); + + if (drift_start_height == 0) + { + difficulty_type existing_cum_diff = m_db->get_block_cumulative_difficulty(height); + if (recalculated_cum_diff != existing_cum_diff) + { + drift_start_height = height; + new_cumulative_difficulties.reserve(top_height + 1 - height); + LOG_ERROR("Difficulty drift found at height:" << height << ", hash:" << m_db->get_block_hash_from_height(height) << ", existing:" << existing_cum_diff << ", recalculated:" << recalculated_cum_diff); + } + } + if (drift_start_height > 0) + { + new_cumulative_difficulties.push_back(recalculated_cum_diff); + if (height % 100000 == 0) + LOG_ERROR(boost::format("%llu / %llu (%.1f%%)") % height % top_height % (100 * (height - drift_start_height) / float(top_height - drift_start_height))); + } + + if (height > 0) + { + timestamps.push_back(m_db->get_block_timestamp(height)); + difficulties.push_back(recalculated_cum_diff); + } + if (timestamps.size() > DIFFICULTY_BLOCKS_COUNT) + { + CHECK_AND_ASSERT_THROW_MES(timestamps.size() == DIFFICULTY_BLOCKS_COUNT + 1, "Wrong timestamps size: " << timestamps.size()); + timestamps.erase(timestamps.begin()); + difficulties.erase(difficulties.begin()); + } + last_cum_diff = recalculated_cum_diff; + } + + if (drift_start_height > 0) + { + LOG_ERROR("Writing to the DB..."); + try + { + m_db->correct_block_cumulative_difficulties(drift_start_height, new_cumulative_difficulties); + } + catch (const std::exception& e) + { + LOG_ERROR("Error correcting cumulative difficulties from height " << drift_start_height << ", what = " << e.what()); + } + LOG_ERROR("Corrected difficulties for " << new_cumulative_difficulties.size() << " blocks"); + // clear cache + m_difficulty_for_next_block_top_hash = crypto::null_hash; + m_timestamps_and_difficulties_height = 0; + } + + return new_cumulative_difficulties.size(); +} +//------------------------------------------------------------------ std::vector Blockchain::get_last_block_timestamps(unsigned int blocks) const { uint64_t height = m_db->height(); -- cgit v1.2.3