On Tue, Dec 11, 2018 at 10:36:59AM -0500, Russell O'Connor wrote:
> I don't believe that the default RBF policy works that way.  My
> understanding is that current policy requires an absolute fee increase (by
> an amount related to incrementalrelayfee).  

Indeed, you are correct (BIP125 rule 4[1]).

Thanks for the correction,

-Dave

[1] For the curious, the relevant code from master's validation.cpp:

    // Finally in addition to paying more fees than the conflicts the
    // new transaction must pay for its own bandwidth.
    CAmount nDeltaFees = nModifiedFees - nConflictingFees;
    if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
    {
        return state.DoS(0, false,
                REJECT_INSUFFICIENTFEE, "insufficient fee", false,
                strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",
                      hash.ToString(),
                      FormatMoney(nDeltaFees),
                      FormatMoney(::incrementalRelayFee.GetFee(nSize))));
    }