@@ -48,21 +48,95 @@ pub trait BroadcasterInterface {
4848/// estimation.
4949#[ derive( Clone , Copy , Debug , Hash , PartialEq , Eq ) ]
5050pub enum ConfirmationTarget {
51- /// We'd like a transaction to confirm in the future, but don't want to commit most of the fees
52- /// required to do so yet. The remaining fees will come via a Child-Pays-For-Parent (CPFP) fee
53- /// bump of the transaction.
54- ///
55- /// The feerate returned should be the absolute minimum feerate required to enter most node
56- /// mempools across the network. Note that if you are not able to obtain this feerate estimate,
57- /// you should likely use the furthest-out estimate allowed by your fee estimator.
58- MempoolMinimum ,
59- /// We are happy with a transaction confirming slowly, at least within a day or so worth of
60- /// blocks.
61- Background ,
62- /// We'd like a transaction to confirm without major delayed, i.e., within the next 12-24 blocks.
63- Normal ,
64- /// We'd like a transaction to confirm in the next few blocks.
65- HighPriority ,
51+ /// We have some funds available on chain which we need to spend prior to some expiry time at
52+ /// which point our counterparty may be able to steal them. Generally we have in the high tens
53+ /// to low hundreds of blocks to get our transaction on-chain, but we shouldn't risk too low a
54+ /// fee - this should be a relatively high priority feerate.
55+ OnChainSweep ,
56+ /// The highest feerate we will allow our channel counterparty to have in a non-anchor channel.
57+ ///
58+ /// This is the feerate on the transaction which we (or our counterparty) will broadcast in
59+ /// order to close the channel unilaterally. Because our counterparty must they can always
60+ /// broadcast the latest state, this value being too low will cause immediate force-closures.
61+ ///
62+ /// Allowing this value to be too high can allow our counterparty to burn our HTLC outputs to
63+ /// dust, which can result in HTLCs failing or force-closures (when the dust HTLCs exceed
64+ /// [`ChannelConfig::max_dust_htlc_exposure`]).
65+ ///
66+ /// Because most nodes use a feerate estimate which is based on a relatively high priority
67+ /// transaction entering the current mempool, setting this to a small multiple of your current
68+ /// high priority feerate estimate should suffice.
69+ ///
70+ /// [`ChannelConfig::max_dust_htlc_exposure`]: crate::util::config::ChannelConfig::max_dust_htlc_exposure
71+ MaxAllowedNonAnchorChannelRemoteFee ,
72+ /// This needs to be sufficient to get into the mempool when the channel needs to
73+ /// be force-closed. Setting too low may result in force-closures. Because this is for anchor
74+ /// channels, we can always bump the feerate later, the feerate here only needs to suffice to
75+ /// enter the mempool.
76+ ///
77+ /// This is the feerate on the transaction which we (or our counterparty) will broadcast in
78+ /// order to close the channel if a channel party goes away. Because our counterparty must
79+ /// ensure they can always broadcast the latest state, this value being too low will cause
80+ /// immediate force-closures.
81+ ///
82+ /// A good estimate is the expected mempool minimum at the time of force-closure. Obviously this
83+ /// is not an estimate which is very easy to calculate because we do not know the future. Using
84+ /// a simple long-term fee estimate or tracking of the mempool minimum is a good approach to
85+ /// ensure you can always close the channel. A future change to Bitcoin's P2P network
86+ /// (package relay) may obviate the need for this entirely.
87+ MinAllowedAnchorChannelRemoteFee ,
88+ /// The lowest feerate we will allow our channel counterparty to have in a non-anchor channel.
89+ /// This needs to be sufficient to get confirmed when the channel needs to be force-closed.
90+ /// Setting too low may result in force-closures.
91+ ///
92+ /// This is the feerate on the transaction which we (or our counterparty) will broadcast in
93+ /// order to close the channel if a channel party goes away. Because our counterparty must
94+ /// ensure they can always broadcast the latest state, this value being too low will cause
95+ /// immediate force-closures. However this value being too high can allow our counterparty to
96+ /// burn our HTLC outputs to dust (see [`ChannelConfig::max_dust_htlc_exposure`]), which can
97+ /// result in LDK force closing the channel to avoid losing money.
98+ ///
99+ /// This feerate represents the fee we pick now, which must be sufficient to enter a block at an
100+ /// arbitrary time in the future. Obviously this is not an estimate which is very easy to
101+ /// calculate. This can leave channels subject to being unable to close if feerates rise, and in
102+ /// general you should prefer anchor channels to ensure you can increase the feerate when the
103+ /// transactions need broadcasting.
104+ ///
105+ /// [`ChannelConfig::max_dust_htlc_exposure`]: crate::util::config::ChannelConfig::max_dust_htlc_exposure
106+ MinAllowedNonAnchorChannelRemoteFee ,
107+ /// This needs to be sufficient to get into the mempool when the channel needs to
108+ /// be force-closed. Setting too low may result in force-closures. Because this is for anchor
109+ /// channels, it can be a low value as we can always bump the feerate later.
110+ ///
111+ /// A good estimate is the expected mempool minimum at the time of force-closure. Obviously this
112+ /// is not an estimate which is very easy to calculate because we do not know the future. Using
113+ /// a simple long-term fee estimate or tracking of the mempool minimum is a good approach to
114+ /// ensure you can always close the channel. A future change to Bitcoin's P2P network
115+ /// (package relay) may obviate the need for this entirely.
116+ AnchorChannelFee ,
117+ /// Lightning is built around the ability to broadcast a transaction in the future to close our
118+ /// channel and claim all pending funds. In order to do so, non-anchor channels are built with
119+ /// transactions which we need to be able to broadcast at some point in the future.
120+ ///
121+ /// This feerate represents the fee we pick now, which must be sufficient to enter a block at an
122+ /// arbitrary time in the future. Obviously this is not an estimate which is very easy to
123+ /// calculate, so most lightning nodes use some relatively high-priority feerate using the
124+ /// current mempool. This leaves channels subject to being unable to close if feerates rise, and
125+ /// in general you should prefer anchor channels to ensure you can increase the feerate when the
126+ /// transactions need broadcasting.
127+ ///
128+ /// This is also used as an upperbound for our attempted feerate when doing cooperative
129+ /// closure of any channel.
130+ NonAnchorChannelFee ,
131+ /// When cooperatively closing a channel, this is the minimum feerate we will accept.
132+ /// Recommended at least within a day or so worth of blocks.
133+ ///
134+ /// This will also be used when initiating a cooperative close of a channel. When closing a
135+ /// channel you can override this fee by using
136+ /// [`ChannelManager::close_channel_with_feerate_and_script`].
137+ ///
138+ /// [`ChannelManager::close_channel_with_feerate_and_script`]: crate::ln::channelmanager::ChannelManager::close_channel_with_feerate_and_script
139+ ChannelCloseMinimum ,
66140}
67141
68142/// A trait which should be implemented to provide feerate information on a number of time
@@ -135,7 +209,7 @@ mod tests {
135209 let test_fee_estimator = & TestFeeEstimator { sat_per_kw } ;
136210 let fee_estimator = LowerBoundedFeeEstimator :: new ( test_fee_estimator) ;
137211
138- assert_eq ! ( fee_estimator. bounded_sat_per_1000_weight( ConfirmationTarget :: Background ) , FEERATE_FLOOR_SATS_PER_KW ) ;
212+ assert_eq ! ( fee_estimator. bounded_sat_per_1000_weight( ConfirmationTarget :: AnchorChannelFee ) , FEERATE_FLOOR_SATS_PER_KW ) ;
139213 }
140214
141215 #[ test]
@@ -144,6 +218,6 @@ mod tests {
144218 let test_fee_estimator = & TestFeeEstimator { sat_per_kw } ;
145219 let fee_estimator = LowerBoundedFeeEstimator :: new ( test_fee_estimator) ;
146220
147- assert_eq ! ( fee_estimator. bounded_sat_per_1000_weight( ConfirmationTarget :: Background ) , sat_per_kw) ;
221+ assert_eq ! ( fee_estimator. bounded_sat_per_1000_weight( ConfirmationTarget :: AnchorChannelFee ) , sat_per_kw) ;
148222 }
149223}
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