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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{
            LOCK(pfrom.m_tx_relay->cs_filter);
            pfrom.m_tx_relay->pfilter.reset(new CBloomFilter(filter));
            pfrom.m_tx_relay->fRelayTxes = true;
        }
        return;
    }
    if (msg_type == NetMsgType::FILTERADD) {
        if (!(pfrom.GetLocalServices() & NODE_BLOOM)) {
            LogPrint(BCLog::NET, "filteradd received despite not offering bloom services from peer=%d; disconnecting\n", pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
        std::vector<unsigned char> vData;
        vRecv >> vData;
        
        
        bool bad = false;
        if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE) {
            bad = true;
        } else if (pfrom.m_tx_relay != nullptr) {
            LOCK(pfrom.m_tx_relay->cs_filter);
            if (pfrom.m_tx_relay->pfilter) {
                pfrom.m_tx_relay->pfilter->insert(vData);
            } else {
                bad = true;
            }
        }
        if (bad) {
            Misbehaving(pfrom.GetId(), 100, "bad filteradd message");