Olaoluwa Osuntokun [ARCHIVE] on Nostr: 📅 Original date posted:2020-10-12 📝 Original message: > It seems to me that the ...
📅 Original date posted:2020-10-12
📝 Original message:
> It seems to me that the "funder pays all the commit tx fees" rule exists
> solely for simplicity (which was totally reasonable).
At this stage, I've learned that simplicity (when doing anything that
involves multi-party on-chain fee negotiating/verification/enforcement can
really go a long way). Just think about all the edge cases w.r.t _allocating
enough funds to pay for fees_ we've discovered over the past few years in
the state machine. I fear adding a more elaborate fee splitting mechanism
would only blow up the number of obscure edge cases that may lead to a
channel temporarily or permanently being "borked".
If we're going to add a "fairer" way of splitting fees, we'll really need to
dig down pre-deployment to ensure that we've explored any resulting edge
cases within our solution space, as we'll only be _adding_ complexity to fee
splitting.
IMO, anchor commitments in their "final form" (fixed fee rate on commitment
transaction, only "emergency" use of update_fee) significantly simplifies
things as it shifts from "funding pay fees", to "broadcaster/confirmer pays
fees". However, as you note this doesn't fully distribute the worst-case
cost of needing to go to chain with a "fully loaded" commitment transaction.
Even with HTLCs, they could only be signed at 1 sat/byte from the funder's
perspective, once again putting the burden on the broadcaster/confirmer to
make up the difference.
-- Laolu
On Mon, Oct 5, 2020 at 6:13 AM Bastien TEINTURIER via Lightning-dev <
lightning-dev at lists.linuxfoundation.org> wrote:
> Good morning list,
>
> It seems to me that the "funder pays all the commit tx fees" rule exists
> solely for simplicity
> (which was totally reasonable). I haven't been able to find much
> discussion about this decision
> on the mailing list nor in the spec commits.
>
> At first glance, it's true that at the beginning of the channel lifetime,
> the funder should be
> responsible for the fee (it's his decision to open a channel after all).
> But as time goes by and
> both peers earn value from this channel, this rule becomes questionable.
> We've discovered since
> then that there is some risk associated with having pending HTLCs
> (flood-and-loot type of attacks,
> pinning, channel jamming, etc).
>
> I think that *in some cases*, fundees should be paying a portion of the
> commit-tx on-chain fees,
> otherwise we may end up with a web-of-trust network where channels would
> only exist between peers
> that trust each other, which is quite limiting (I'm hoping we can do
> better).
>
> Routing nodes may be at risk when they *receive* HTLCs. All the attacks
> that steal funds come from
> the fact that a routing node has paid downstream but cannot claim the
> upstream HTLCs (correct me
> if that's incorrect). Thus I'd like nodes to pay for the on-chain fees of
> the HTLCs they offer
> while they're pending in the commit-tx, regardless of whether they're
> funder or fundee.
>
> The simplest way to do this would be to deduce the HTLC cost (172 *
> feerate) from the offerer's
> main output (instead of the funder's main output, while keeping the base
> commit tx weight paid
> by the funder).
>
> A more extreme proposal would be to tie the *total* commit-tx fee to the
> channel usage:
>
> * if there are no pending HTLCs, the funder pays all the fee
> * if there are pending HTLCs, each node pays a proportion of the fee
> proportional to the number of
> HTLCs they offered. If Alice offered 1 HTLC and Bob offered 3 HTLCs, Bob
> pays 75% of the
> commit-tx fee and Alice pays 25%. When the HTLCs settle, the fee is
> redistributed.
>
> This model uses the on-chain fee as collateral for usage of the channel.
> If Alice wants to forward
> HTLCs through this channel (because she has something to gain - routing
> fees), she should be taking
> on some of the associated risk, not Bob. Bob will be taking the same risk
> downstream if he chooses
> to forward.
>
> I believe it also forces the fundee to care about on-chain feerates, which
> is a healthy incentive.
> It may create a feedback loop between on-chain feerates and routing fees,
> which I believe is also
> a good long-term thing (but it's hard to predict as there may be negative
> side-effects as well).
>
> What do you all think? Is this a terrible idea? Is it okay-ish, but not
> worth the additional
> complexity? Is it an amazing idea worth a lightning nobel? Please don't
> take any of my claims
> for granted and challenge them, there may be negative side-effects I'm
> completely missing, this is
> a fragile game of incentives...
>
> Side-note: don't forget to take into account that the fees for HTLC
> transactions (second-level txs)
> are always paid by the party that broadcasts them (which makes sense). I
> still think this is not
> enough and can even be abused by fundees in some setups.
>
> Thanks,
> Bastien
> _______________________________________________
> Lightning-dev mailing list
> Lightning-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
>
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📝 Original message:
> It seems to me that the "funder pays all the commit tx fees" rule exists
> solely for simplicity (which was totally reasonable).
At this stage, I've learned that simplicity (when doing anything that
involves multi-party on-chain fee negotiating/verification/enforcement can
really go a long way). Just think about all the edge cases w.r.t _allocating
enough funds to pay for fees_ we've discovered over the past few years in
the state machine. I fear adding a more elaborate fee splitting mechanism
would only blow up the number of obscure edge cases that may lead to a
channel temporarily or permanently being "borked".
If we're going to add a "fairer" way of splitting fees, we'll really need to
dig down pre-deployment to ensure that we've explored any resulting edge
cases within our solution space, as we'll only be _adding_ complexity to fee
splitting.
IMO, anchor commitments in their "final form" (fixed fee rate on commitment
transaction, only "emergency" use of update_fee) significantly simplifies
things as it shifts from "funding pay fees", to "broadcaster/confirmer pays
fees". However, as you note this doesn't fully distribute the worst-case
cost of needing to go to chain with a "fully loaded" commitment transaction.
Even with HTLCs, they could only be signed at 1 sat/byte from the funder's
perspective, once again putting the burden on the broadcaster/confirmer to
make up the difference.
-- Laolu
On Mon, Oct 5, 2020 at 6:13 AM Bastien TEINTURIER via Lightning-dev <
lightning-dev at lists.linuxfoundation.org> wrote:
> Good morning list,
>
> It seems to me that the "funder pays all the commit tx fees" rule exists
> solely for simplicity
> (which was totally reasonable). I haven't been able to find much
> discussion about this decision
> on the mailing list nor in the spec commits.
>
> At first glance, it's true that at the beginning of the channel lifetime,
> the funder should be
> responsible for the fee (it's his decision to open a channel after all).
> But as time goes by and
> both peers earn value from this channel, this rule becomes questionable.
> We've discovered since
> then that there is some risk associated with having pending HTLCs
> (flood-and-loot type of attacks,
> pinning, channel jamming, etc).
>
> I think that *in some cases*, fundees should be paying a portion of the
> commit-tx on-chain fees,
> otherwise we may end up with a web-of-trust network where channels would
> only exist between peers
> that trust each other, which is quite limiting (I'm hoping we can do
> better).
>
> Routing nodes may be at risk when they *receive* HTLCs. All the attacks
> that steal funds come from
> the fact that a routing node has paid downstream but cannot claim the
> upstream HTLCs (correct me
> if that's incorrect). Thus I'd like nodes to pay for the on-chain fees of
> the HTLCs they offer
> while they're pending in the commit-tx, regardless of whether they're
> funder or fundee.
>
> The simplest way to do this would be to deduce the HTLC cost (172 *
> feerate) from the offerer's
> main output (instead of the funder's main output, while keeping the base
> commit tx weight paid
> by the funder).
>
> A more extreme proposal would be to tie the *total* commit-tx fee to the
> channel usage:
>
> * if there are no pending HTLCs, the funder pays all the fee
> * if there are pending HTLCs, each node pays a proportion of the fee
> proportional to the number of
> HTLCs they offered. If Alice offered 1 HTLC and Bob offered 3 HTLCs, Bob
> pays 75% of the
> commit-tx fee and Alice pays 25%. When the HTLCs settle, the fee is
> redistributed.
>
> This model uses the on-chain fee as collateral for usage of the channel.
> If Alice wants to forward
> HTLCs through this channel (because she has something to gain - routing
> fees), she should be taking
> on some of the associated risk, not Bob. Bob will be taking the same risk
> downstream if he chooses
> to forward.
>
> I believe it also forces the fundee to care about on-chain feerates, which
> is a healthy incentive.
> It may create a feedback loop between on-chain feerates and routing fees,
> which I believe is also
> a good long-term thing (but it's hard to predict as there may be negative
> side-effects as well).
>
> What do you all think? Is this a terrible idea? Is it okay-ish, but not
> worth the additional
> complexity? Is it an amazing idea worth a lightning nobel? Please don't
> take any of my claims
> for granted and challenge them, there may be negative side-effects I'm
> completely missing, this is
> a fragile game of incentives...
>
> Side-note: don't forget to take into account that the fees for HTLC
> transactions (second-level txs)
> are always paid by the party that broadcasts them (which makes sense). I
> still think this is not
> enough and can even be abused by fundees in some setups.
>
> Thanks,
> Bastien
> _______________________________________________
> Lightning-dev mailing list
> Lightning-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev
>
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