Method ProcessHeadersMessage

src/net_processing.cpp:2989–3148

}

void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, Peer& peer,
                                            std::vector<CBlockHeader>&& headers,
                                            bool via_compact_block)
{
    size_t nCount = headers.size();

    if (nCount == 0) {
        // Nothing interesting. Stop asking this peers for more headers.
        // If we were in the middle of headers sync, receiving an empty headers
        // message suggests that the peer suddenly has nothing to give us
        // (perhaps it reorged to our chain). Clear download state for this peer.
        LOCK(peer.m_headers_sync_mutex);
        if (peer.m_headers_sync) {
            peer.m_headers_sync.reset(nullptr);
            LOCK(m_headers_presync_mutex);
            m_headers_presync_stats.erase(pfrom.GetId());
        }
        // A headers message with no headers cannot be an announcement, so assume
        // it is a response to our last getheaders request, if there is one.
        peer.m_last_getheaders_timestamp = {};
        return;
    }

    // Before we do any processing, make sure these pass basic sanity checks.
    // We'll rely on headers having valid proof-of-work further down, as an
    // anti-DoS criteria (note: this check is required before passing any
    // headers into HeadersSyncState).
    if (!CheckHeadersPoW(headers, peer)) {
        // Misbehaving() calls are handled within CheckHeadersPoW(), so we can
        // just return. (Note that even if a header is announced via compact
        // block, the header itself should be valid, so this type of error can
        // always be punished.)
        return;
    }

    const CBlockIndex *pindexLast = nullptr;

    // We'll set already_validated_work to true if these headers are
    // successfully processed as part of a low-work headers sync in progress
    // (either in PRESYNC or REDOWNLOAD phase).
    // If true, this will mean that any headers returned to us (ie during
    // REDOWNLOAD) can be validated without further anti-DoS checks.
    bool already_validated_work = false;

    // If we're in the middle of headers sync, let it do its magic.
    bool have_headers_sync = false;
    {
        LOCK(peer.m_headers_sync_mutex);

        already_validated_work = IsContinuationOfLowWorkHeadersSync(peer, pfrom, headers);

        // The headers we passed in may have been:
        // - untouched, perhaps if no headers-sync was in progress, or some
        //   failure occurred
        // - erased, such as if the headers were successfully processed and no
        //   additional headers processing needs to take place (such as if we
        //   are still in PRESYNC)
        // - replaced with headers that are now ready for validation, such as