Method ValidateAndStoreRedownloadedHeader

src/headerssync.cpp:215–278

}

bool HeadersSyncState::ValidateAndStoreRedownloadedHeader(const CBlockHeader& header)
{
    Assume(m_download_state == State::REDOWNLOAD);
    if (m_download_state != State::REDOWNLOAD) return false;

    int64_t next_height = m_redownload_buffer_last_height + 1;

    // Ensure that we're working on a header that connects to the chain we're
    // downloading.
    if (header.hashPrevBlock != m_redownload_buffer_last_hash) {
        LogDebug(BCLog::NET, "Initial headers sync aborted with peer=%d: non-continuous headers at height=%i (redownload phase)\n", m_id, next_height);
        return false;
    }

    // Check that the difficulty adjustments are within our tolerance:
    uint32_t previous_nBits{0};
    if (!m_redownloaded_headers.empty()) {
        previous_nBits = m_redownloaded_headers.back().nBits;
    } else {
        previous_nBits = m_chain_start.nBits;
    }

    if (!PermittedDifficultyTransition(m_consensus_params, next_height,
                previous_nBits, header.nBits)) {
        LogDebug(BCLog::NET, "Initial headers sync aborted with peer=%d: invalid difficulty transition at height=%i (redownload phase)\n", m_id, next_height);
        return false;
    }

    // Track work on the redownloaded chain
    m_redownload_chain_work += GetBlockProof(header);

    if (m_redownload_chain_work >= m_minimum_required_work) {
        m_process_all_remaining_headers = true;
    }

    // If we're at a header for which we previously stored a commitment, verify
    // it is correct. Failure will result in aborting download.
    // Also, don't check commitments once we've gotten to our target blockhash;
    // it's possible our peer has extended its chain between our first sync and
    // our second, and we don't want to return failure after we've seen our
    // target blockhash just because we ran out of commitments.
    if (!m_process_all_remaining_headers && next_height % m_params.commitment_period == m_commit_offset) {
        if (m_header_commitments.size() == 0) {
            LogDebug(BCLog::NET, "Initial headers sync aborted with peer=%d: commitment overrun at height=%i (redownload phase)\n", m_id, next_height);
            // Somehow our peer managed to feed us a different chain and
            // we've run out of commitments.
            return false;
        }
        bool commitment = m_hasher(header.GetHash()) & 1;
        bool expected_commitment = m_header_commitments.front();
        m_header_commitments.pop_front();
        if (commitment != expected_commitment) {
            LogDebug(BCLog::NET, "Initial headers sync aborted with peer=%d: commitment mismatch at height=%i (redownload phase)\n", m_id, next_height);
            return false;
        }
    }

    // Store this header for later processing.