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2023-06-08 01:14:19 CEST

- reply

📅 Original date posted:2022-10-12
📝 Original message:Hello Pieter,
Thanks for taking the time to comment! I'll answer inline.
On Wed, Oct 12, 2022 at 2:51 PM Pieter Wuille <bitcoin-dev at wuille.net>
wrote:
> I certainly recognize that adding the flag is a likely step towards, over
> time, the full RBF policy becoming more widely adopted on the network.
That is
> presumably the reason why people are in favor of having the flag, even
default
> off - including me. I believe that policy's adoption is inevitable
eventually,
> but the speed at which that is achieved is certainly a function of
> availability and adopted of software which provides the option.
As stated in the original posting, I believe too that a full-RBF network is
not
only inevitable but also desirable. Miner incentives will eventually win,
so we
should address them before they fully kick in (ie. before transaction fees
become a meaningful portion of the block reward).
> So I have a hard time imagining how it would change anything
*immediately* on
> the network at large (without things like default on and/or preferential
> peering, ...), but I still believe it's an important step.
Notice that I'm not saying this changes anything immediately on the network
at
large. In fact, it is unlikely that the opt-in flag alone would be enough to
migrate the network at large to full-RBF.
There's a real possibility that, after deployment of the opt-in flag,
either no
meaningful hashing power adopts it or no connected component of
transaction-relaying nodes adopts it. If that's the case, the deployment
won't
help nodes participating in multi-party funded transactions protect against
the
class of attacks described in [1] (which was, as I understand, the original
intention of #25353).
If that's not the case, it means that at least some meaningful hashing power
adopted it and that there exist some connected components of
transaction-relaying nodes that adopted it. This is certainly far from
having
wide adoption of full-RBF in the network at large. However, once we reach
that
minimal level of adoption in the mining and relaying layers, any node on a
full-RBF connected component can send an on-chain payment to an application
and
then get a replacement mined. That is, applications that accept incoming
on-chain payments from untrusted parties can be immediately exposed to
full-RBF
transaction replacements, even if they didn't opt into full-RBF in their
nodes.
In an adversarial setting, such as the one for zero-conf applications (as
defined in the original posting), this increases the risk of an attack
substantially, making the entire strategy moot.
> In my view, it is just what I said: a step towards getting full RBF on the
> network, by allowing experimentation and socializing the notion that
> developers believe it is time.
Those are worthy goals. I believe we can design a deployment strategy for
full-RBF that takes them into account and, at the same time, gives a clear
timeline for any affected application to adapt.
This could be one such proposal:
1. We activate opt-in full-RBF on testnet now.
2. We commit now (in the code) to a block height in the future at which
opt-out
full-RBF will activate on mainnet.
The first point will allow for experimentation and give a testing ground to
all
affected applications. The second point socializes the notion that
developers
believe it is time, giving a clear message and timeline for anyone affected
to
adapt. It also has the benefit that many more nodes will have upgraded by
the
time we reach the activation block height, making the transition to a
full-RBF
network much more predictable and easy to reason about.
There's an argument to be made that the miner incentive incompatibility
problem
of a non-full-RBF network gets measurably worse at the time of the next
halving.
To fix this, we could choose any block height before that, giving a clear
and
predictable transition timeline.
[1]
https://lists.linuxfoundation.org/pipermail/lightning-dev/2021-May/003033.html
On Wed, Oct 12, 2022 at 1:11 PM Pieter Wuille <bitcoin-dev at wuille.net>
wrote:
> On Wednesday, October 12th, 2022 at 1:42 AM, Anthony Towns <
> aj at erisian.com.au> wrote:
>
> > On Tue, Oct 11, 2022 at 04:18:10PM +0000, Pieter Wuille via bitcoin-dev
> wrote:
> >
> > > On Friday, October 7th, 2022 at 5:37 PM, Dario Sneidermanis via
> bitcoin-dev bitcoin-dev at lists.linuxfoundation.org wrote:
> > >
> > > > Thanks for the fast answer! It seems I missed the link to the PR,
> sorry for the
> > > > confusion. I'm referring to the opt-in flag for full-RBF from #25353
> > > > (https://github.com/bitcoin/bitcoin/pull/25353).
> > > > It is not clear to me why you believe the merging of this particular
> pull request poses an immediate risk to you.
> >
> >
> > Did you see the rest of Dario's reply, bottom-posted after the quoted
> > text? Namely:
>
> Oh, my mail client for some reason chose to hide all that. Dario, I'm
> sorry for missing this; I see now that you were certainly aware of what the
> PR under consideration did.
>
> Further comments inline.
>
> > On Fri, Oct 07, 2022 at 06:37:38PM -0300, Dario Sneidermanis via
>
> > > The question then is whether an opt-in flag for full-RBF will have
> enough
> > > adoption to get us from 1 to 2. If it isn't, then #25353 won't meet its
> > > objective of allowing nodes participating in multi-party funding
> protocols
> > > to assume that they can rely on full-RBF. If it is, then zero-conf
> applications
> > > will be at severe risk (per the logic in the initial email).
>
> >
> >
> > That logic seems reasonably sound to me:
> >
> > - if adding the option does nothing, then there's no point adding it,
> > and no harm in restricting it to test nets only
> >
> > - if adding the option does do something, then businesses using zero-conf
> > need to react immediately, or will go from approximately zero risk of
> > losing funds, to substantial risk
> >
> > (I guess having the option today may allow you to manually switch your
> > node over to supporting fullrbf in future when the majority of the
> network
> > supports it, without needing to do an additional upgrade in the meantime;
> > but that seems like a pretty weak benefit)
>
> I certainly recognize that adding the flag is a likely step towards, over
> time, the full RBF policy becoming more widely adopted on the network. That
> is presumably the reason why people are in favor of having the flag, even
> default off - including me. I believe that policy's adoption is inevitable
> eventually, but the speed at which that is achieved is certainly a function
> of availability and adopted of software which provides the option.
>
> That said, I think it's a bit of a jump to conclude that the only two
> options are that either the existence of the flag either has no effect at
> all, or poses an immediate threat to those relying on its absence. In my
> view, it is just what I said: a step towards getting full RBF on the
> network, by allowing experimentation and socializing the notion that
> developers believe it is time. So I have a hard time imagining how it would
> change anything *immediately* on the network at large (without things like
> default on and/or preferential peering, ...), but I still believe it's an
> important step.
>
> Cheers,
>
> --
> Pieter
>
>
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2023-06-08 01:14:18 CEST

- reply

📅 Original date posted:2022-10-07
📝 Original message:Hello David,
Thanks for the fast answer! It seems I missed the link to the PR, sorry for
the
confusion. I'm referring to the opt-in flag for full-RBF from #25353
(https://github.com/bitcoin/bitcoin/pull/25353).
On Fri, Oct 7, 2022 at 2:21 PM David A. Harding <dave at dtrt.org> wrote:
> On 2022-10-07 06:20, Dario Sneidermanis via bitcoin-dev wrote:
> > Hello list,
> >
> > I'm Dario, from Muun wallet [...] we've been reviewing the latest
> > bitcoin core release
> > candidate [...] we understood we had at least a year from the initial
> > opt-in deployment until opt-out was deployed, giving us enough time to
> > adapt
> > Muun to the new policies. However, when reviewing the 24.0 release
> > candidate
> > just a few days ago, we realized that zero-conf apps (like Muun) must
> > *immediately turn off* their zero-conf features.
>
> Hi Dario,
>
> I'm wondering if there's been some confusion. There are two RBF-related
> items in the current release notes draft:[1]
>
> 1. "A new mempoolfullrbf option has been added, which enables the
> mempool to accept transaction replacement without enforcing BIP125
> replaceability signaling. (#25353)"
>
> 2. "The -walletrbf startup option will now default to true. The wallet
> will now default to opt-in RBF on transactions that it creates.
> (#25610)"
>
> The first item (from PR #25353) does allow a transaction without a
> BIP125 signal to be replaced, but this configuration option is set to
> disabled by default.[2] There have been software forks of Bitcoin Core
> since at least 2015 which have allowed replacement of non-signaling
> transactions, so this option just makes that behavior a little bit more
> accessible to users of Bitcoin Core.
The "activation" of full-RBF after deployment works in a pretty interesting
way:
1. If no miner is running full-RBF or there aren't easily accessible
connected
components of nodes running full-RBF connected to the miners, then
full-RBF
is mostly ineffective since replacements aren't relayed and/or mined.
2. There's a middle ground where *some* connected components of full-RBF
nodes
can relay and mine replacements, where some full-RBF nodes will be able
to
replace via full-RBF and some won't (depending on their peers).
3. With high enough adoption, the relay graph has enough density of full-RBF
nodes that almost all full-RBF nodes can replace transactions via
full-RBF.
While there have been forks of Bitcoin Core (like Bitcoin Knots) running
full-RBF for a while, today most nodes (by far) are running Bitcoin Core.
So,
Bitcoin Core adding an opt-in flag (ie. off by default) makes it easier to
be
picked up by most node operators. Making the flag opt-out (ie. on by
default)
would make it easier still. We are dealing with a gradient going from hard
enough that we are still in 1, to easy enough that we get to 3.
The question then is whether an opt-in flag for full-RBF will have enough
adoption to get us from 1 to 2. If it isn't, then #25353 won't meet its
objective of allowing nodes participating in multi-party funding protocols
to
assume that they can rely on full-RBF. If it is, then zero-conf applications
will be at severe risk (per the logic in the initial email).
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