Date: Sun, 20 May 2018 23:56:58 -0400
From: Peter Todd <pete@petertodd.org>
To: Rusty Russell <rusty@rustcorp.com.au>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Message-ID: <20180521035658.vfo4wx6ifum2s2o5@petertodd.org>
References: <87po25lmzs.fsf@rustcorp.com.au>
	<201805100227.42217.luke@dashjr.org>
	<87vabnq9ui.fsf@rustcorp.com.au>
	<CADZtCShwOV+GuJ5__GMi9hd2_X=BztASPBihDXakU3Mjb39wcQ@mail.gmail.com>
	<87zi0tisft.fsf@rustcorp.com.au>
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In-Reply-To: <87zi0tisft.fsf@rustcorp.com.au>
User-Agent: NeoMutt/20170113 (1.7.2)
Cc: Matt Corallo <matt@chaincode.com>
Subject: Re: [bitcoin-dev] Making OP_TRUE standard?
Precedence: list


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On Mon, May 21, 2018 at 01:14:06PM +0930, Rusty Russell via bitcoin-dev wro=
te:
> Jim Posen <jim.posen@gmail.com> writes:
> > I believe OP_CSV with a relative locktime of 0 could be used to enforce=
 RBF
> > on the spending tx?
>=20
> Marco points out that if the parent is RBF, this child inherits it, so
> we're actually good here.
>=20
> However, Matt Corallo points out that you can block RBF will a
> large-but-lowball tx, as BIP 125 points out:
>=20
>    will be replaced by a new transaction...:
>=20
>    3. The replacement transaction pays an absolute fee of at least the sum
>       paid by the original transactions.
>=20
> I understand implementing a single mempool requires these kind of
> up-front decisions on which tx is "better", but I wonder about the
> consequences of dropping this heuristic?  Peter?

We've discussed this before: that rule prevents bandwidth usage DoS attacks=
 on
the mempool; it's not a "heuristic". If you drop it, an attacker can repeat=
edly
broadcast and replace a series of transactions to use up tx relay bandwidth=
 for
significantly lower cost than otherwise.

Though these days with relatively high minimum fees that may not matter.

--=20
https://petertodd.org 'peter'[:-1]@petertodd.org

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