📅 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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Olaoluwa Osuntokun [ARCHIVE] /
npub19h…zkvn4
2023-06-09 13:01:01
in reply to nevent1q…4kn5
Author Public Key
npub19helcfnqgk2jrwzjex2aflq6jwfc8zd9uzzkwlgwhve7lykv23mq5zkvn4Published at
2023-06-09 13:01:01Event JSON
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"content": "📅 Original date posted:2020-10-12\n📝 Original message:\n\u003e It seems to me that the \"funder pays all the commit tx fees\" rule exists\n\u003e solely for simplicity (which was totally reasonable).\n\nAt this stage, I've learned that simplicity (when doing anything that\ninvolves multi-party on-chain fee negotiating/verification/enforcement can\nreally go a long way). Just think about all the edge cases w.r.t _allocating\nenough funds to pay for fees_ we've discovered over the past few years in\nthe state machine. I fear adding a more elaborate fee splitting mechanism\nwould only blow up the number of obscure edge cases that may lead to a\nchannel temporarily or permanently being \"borked\".\n\nIf we're going to add a \"fairer\" way of splitting fees, we'll really need to\ndig down pre-deployment to ensure that we've explored any resulting edge\ncases within our solution space, as we'll only be _adding_ complexity to fee\nsplitting.\n\nIMO, anchor commitments in their \"final form\" (fixed fee rate on commitment\ntransaction, only \"emergency\" use of update_fee) significantly simplifies\nthings as it shifts from \"funding pay fees\", to \"broadcaster/confirmer pays\nfees\". However, as you note this doesn't fully distribute the worst-case\ncost of needing to go to chain with a \"fully loaded\" commitment transaction.\nEven with HTLCs, they could only be signed at 1 sat/byte from the funder's\nperspective, once again putting the burden on the broadcaster/confirmer to\nmake up the difference.\n\n-- Laolu\n\n\nOn Mon, Oct 5, 2020 at 6:13 AM Bastien TEINTURIER via Lightning-dev \u003c\nlightning-dev at lists.linuxfoundation.org\u003e wrote:\n\n\u003e Good morning list,\n\u003e\n\u003e It seems to me that the \"funder pays all the commit tx fees\" rule exists\n\u003e solely for simplicity\n\u003e (which was totally reasonable). I haven't been able to find much\n\u003e discussion about this decision\n\u003e on the mailing list nor in the spec commits.\n\u003e\n\u003e At first glance, it's true that at the beginning of the channel lifetime,\n\u003e the funder should be\n\u003e responsible for the fee (it's his decision to open a channel after all).\n\u003e But as time goes by and\n\u003e both peers earn value from this channel, this rule becomes questionable.\n\u003e We've discovered since\n\u003e then that there is some risk associated with having pending HTLCs\n\u003e (flood-and-loot type of attacks,\n\u003e pinning, channel jamming, etc).\n\u003e\n\u003e I think that *in some cases*, fundees should be paying a portion of the\n\u003e commit-tx on-chain fees,\n\u003e otherwise we may end up with a web-of-trust network where channels would\n\u003e only exist between peers\n\u003e that trust each other, which is quite limiting (I'm hoping we can do\n\u003e better).\n\u003e\n\u003e Routing nodes may be at risk when they *receive* HTLCs. All the attacks\n\u003e that steal funds come from\n\u003e the fact that a routing node has paid downstream but cannot claim the\n\u003e upstream HTLCs (correct me\n\u003e if that's incorrect). Thus I'd like nodes to pay for the on-chain fees of\n\u003e the HTLCs they offer\n\u003e while they're pending in the commit-tx, regardless of whether they're\n\u003e funder or fundee.\n\u003e\n\u003e The simplest way to do this would be to deduce the HTLC cost (172 *\n\u003e feerate) from the offerer's\n\u003e main output (instead of the funder's main output, while keeping the base\n\u003e commit tx weight paid\n\u003e by the funder).\n\u003e\n\u003e A more extreme proposal would be to tie the *total* commit-tx fee to the\n\u003e channel usage:\n\u003e\n\u003e * if there are no pending HTLCs, the funder pays all the fee\n\u003e * if there are pending HTLCs, each node pays a proportion of the fee\n\u003e proportional to the number of\n\u003e HTLCs they offered. If Alice offered 1 HTLC and Bob offered 3 HTLCs, Bob\n\u003e pays 75% of the\n\u003e commit-tx fee and Alice pays 25%. When the HTLCs settle, the fee is\n\u003e redistributed.\n\u003e\n\u003e This model uses the on-chain fee as collateral for usage of the channel.\n\u003e If Alice wants to forward\n\u003e HTLCs through this channel (because she has something to gain - routing\n\u003e fees), she should be taking\n\u003e on some of the associated risk, not Bob. Bob will be taking the same risk\n\u003e downstream if he chooses\n\u003e to forward.\n\u003e\n\u003e I believe it also forces the fundee to care about on-chain feerates, which\n\u003e is a healthy incentive.\n\u003e It may create a feedback loop between on-chain feerates and routing fees,\n\u003e which I believe is also\n\u003e a good long-term thing (but it's hard to predict as there may be negative\n\u003e side-effects as well).\n\u003e\n\u003e What do you all think? Is this a terrible idea? Is it okay-ish, but not\n\u003e worth the additional\n\u003e complexity? Is it an amazing idea worth a lightning nobel? Please don't\n\u003e take any of my claims\n\u003e for granted and challenge them, there may be negative side-effects I'm\n\u003e completely missing, this is\n\u003e a fragile game of incentives...\n\u003e\n\u003e Side-note: don't forget to take into account that the fees for HTLC\n\u003e transactions (second-level txs)\n\u003e are always paid by the party that broadcasts them (which makes sense). I\n\u003e still think this is not\n\u003e enough and can even be abused by fundees in some setups.\n\u003e\n\u003e Thanks,\n\u003e Bastien\n\u003e _______________________________________________\n\u003e Lightning-dev mailing list\n\u003e Lightning-dev at lists.linuxfoundation.org\n\u003e https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev\n\u003e\n-------------- next part --------------\nAn HTML attachment was scrubbed...\nURL: \u003chttp://lists.linuxfoundation.org/pipermail/lightning-dev/attachments/20201012/148e00a3/attachment-0001.html\u003e",
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