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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bool fAnnounceUsingCMPCTBLOCK = false;
            uint64_t nCMPCTBLOCKVersion = 2;
            if (pfrom.GetLocalServices() & NODE_WITNESS)
                m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
            nCMPCTBLOCKVersion = 1;
            m_connman.PushMessage(&pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
        }
        pfrom.fSuccessfullyConnected = true;
        return;
    }
    if (msg_type == NetMsgType::SENDHEADERS) {
        LOCK(cs_main);
        State(pfrom.GetId())->fPreferHeaders = true;
        return;
    }
    if (msg_type == NetMsgType::SENDCMPCT) {
        bool fAnnounceUsingCMPCTBLOCK = false;
        uint64_t nCMPCTBLOCKVersion = 0;
        vRecv >> fAnnounceUsingCMPCTBLOCK >> nCMPCTBLOCKVersion;
        if (nCMPCTBLOCKVersion == 1 || ((pfrom.GetLocalServices() & NODE_WITNESS) && nCMPCTBLOCKVersion == 2)) {
            LOCK(cs_main);
            
            if (!State(pfrom.GetId())->fProvidesHeaderAndIDs) {
                State(pfrom.GetId())->fProvidesHeaderAndIDs = true;
                State(pfrom.GetId())->fWantsCmpctWitness = nCMPCTBLOCKVersion == 2;
            }
            if (State(pfrom.GetId())->fWantsCmpctWitness == (nCMPCTBLOCKVersion == 2)) { 
                State(pfrom.GetId())->fPreferHeaderAndIDs = fAnnounceUsingCMPCTBLOCK;