There are some potential feefilter cleanups mentioned and motivated in comment https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-805808485 . If you address the locking one, please be careful and make sure that `round()` is only called under a lock. See https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-807992199

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* Bitcoin Core P2P design
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return;
        }
        std::vector<CBlockHeader> headers;
        
        unsigned int nCount = ReadCompactSize(vRecv);
        if (nCount > MAX_HEADERS_RESULTS) {
            Misbehaving(pfrom.GetId(), 20, strprintf("headers message size = %u", nCount));
            return;
        }
        headers.resize(nCount);
        for (unsigned int n = 0; n < nCount; n++) {
            vRecv >> headers[n];
            ReadCompactSize(vRecv); 
        }
        return ProcessHeadersMessage(pfrom, *peer, headers, false);
    }
    if (msg_type == NetMsgType::BLOCK)
    {
        
        if (fImporting || fReindex) {
            LogPrint(BCLog::NET, "Unexpected block message received from peer %d\n", pfrom.GetId());
            return;
        }
        std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
        vRecv >> *pblock;
        LogPrint(BCLog::NET, "received block %s peer=%d\n", pblock->GetHash().ToString(), pfrom.GetId());
        bool forceProcessing = false;
        const uint256 hash(pblock->GetHash());
        {
            LOCK(cs_main);