1 // This file is Copyright its original authors, visible in version control
4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
7 // You may not use this file except in accordance with one or both of these
10 //! Various user-configurable channel limits and settings which ChannelManager
13 use crate::ln::channel::MAX_FUNDING_SATOSHIS_NO_WUMBO;
14 use crate::ln::channelmanager::{BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
17 use crate::util::ser::Readable;
19 /// Configuration we set when applicable.
21 /// Default::default() provides sane defaults.
22 #[derive(Copy, Clone, Debug)]
23 pub struct ChannelHandshakeConfig {
24 /// Confirmations we will wait for before considering the channel locked in.
25 /// Applied only for inbound channels (see ChannelHandshakeLimits::max_minimum_depth for the
26 /// equivalent limit applied to outbound channels).
28 /// A lower-bound of 1 is applied, requiring all channels to have a confirmed commitment
29 /// transaction before operation. If you wish to accept channels with zero confirmations, see
30 /// [`UserConfig::manually_accept_inbound_channels`] and
31 /// [`ChannelManager::accept_inbound_channel_from_trusted_peer_0conf`].
35 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
36 /// [`ChannelManager::accept_inbound_channel_from_trusted_peer_0conf`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel_from_trusted_peer_0conf
37 pub minimum_depth: u32,
38 /// Set to the number of blocks we require our counterparty to wait to claim their money (ie
39 /// the number of blocks we have to punish our counterparty if they broadcast a revoked
42 /// This is one of the main parameters of our security model. We (or one of our watchtowers) MUST
43 /// be online to check for revoked transactions on-chain at least once every our_to_self_delay
44 /// blocks (minus some margin to allow us enough time to broadcast and confirm a transaction,
45 /// possibly with time in between to RBF the spending transaction).
47 /// Meanwhile, asking for a too high delay, we bother peer to freeze funds for nothing in
48 /// case of an honest unilateral channel close, which implicitly decrease the economic value of
51 /// Default value: [`BREAKDOWN_TIMEOUT`], we enforce it as a minimum at channel opening so you
52 /// can tweak config to ask for more security, not less.
53 pub our_to_self_delay: u16,
54 /// Set to the smallest value HTLC we will accept to process.
56 /// This value is sent to our counterparty on channel-open and we close the channel any time
57 /// our counterparty misbehaves by sending us an HTLC with a value smaller than this.
59 /// Default value: 1. If the value is less than 1, it is ignored and set to 1, as is required
61 pub our_htlc_minimum_msat: u64,
62 /// Sets the percentage of the channel value we will cap the total value of outstanding inbound
65 /// This can be set to a value between 1-100, where the value corresponds to the percent of the
66 /// channel value in whole percentages.
69 /// * If configured to another value than the default value 10, any new channels created with
70 /// the non default value will cause versions of LDK prior to 0.0.104 to refuse to read the
73 /// * This caps the total value for inbound HTLCs in-flight only, and there's currently
74 /// no way to configure the cap for the total value of outbound HTLCs in-flight.
76 /// * The requirements for your node being online to ensure the safety of HTLC-encumbered funds
77 /// are different from the non-HTLC-encumbered funds. This makes this an important knob to
78 /// restrict exposure to loss due to being offline for too long.
79 /// See [`ChannelHandshakeConfig::our_to_self_delay`] and [`ChannelConfig::cltv_expiry_delta`]
80 /// for more information.
82 /// Default value: 10.
83 /// Minimum value: 1, any values less than 1 will be treated as 1 instead.
84 /// Maximum value: 100, any values larger than 100 will be treated as 100 instead.
85 pub max_inbound_htlc_value_in_flight_percent_of_channel: u8,
86 /// If set, we attempt to negotiate the `scid_privacy` (referred to as `scid_alias` in the
87 /// BOLTs) option for outbound private channels. This provides better privacy by not including
88 /// our real on-chain channel UTXO in each invoice and requiring that our counterparty only
89 /// relay HTLCs to us using the channel's SCID alias.
91 /// If this option is set, channels may be created that will not be readable by LDK versions
92 /// prior to 0.0.106, causing [`ChannelManager`]'s read method to return a
93 /// [`DecodeError::InvalidValue`].
95 /// Note that setting this to true does *not* prevent us from opening channels with
96 /// counterparties that do not support the `scid_alias` option; we will simply fall back to a
97 /// private channel without that option.
99 /// Ignored if the channel is negotiated to be announced, see
100 /// [`ChannelHandshakeConfig::announced_channel`] and
101 /// [`ChannelHandshakeLimits::force_announced_channel_preference`] for more.
103 /// Default value: false. This value is likely to change to true in the future.
105 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
106 /// [`DecodeError::InvalidValue`]: crate::ln::msgs::DecodeError::InvalidValue
107 pub negotiate_scid_privacy: bool,
108 /// Set to announce the channel publicly and notify all nodes that they can route via this
111 /// This should only be set to true for nodes which expect to be online reliably.
113 /// As the node which funds a channel picks this value this will only apply for new outbound
114 /// channels unless [`ChannelHandshakeLimits::force_announced_channel_preference`] is set.
116 /// Default value: false.
117 pub announced_channel: bool,
118 /// When set, we commit to an upfront shutdown_pubkey at channel open. If our counterparty
119 /// supports it, they will then enforce the mutual-close output to us matches what we provided
120 /// at intialization, preventing us from closing to an alternate pubkey.
122 /// This is set to true by default to provide a slight increase in security, though ultimately
123 /// any attacker who is able to take control of a channel can just as easily send the funds via
124 /// lightning payments, so we never require that our counterparties support this option.
126 /// The upfront key committed is provided from [`SignerProvider::get_shutdown_scriptpubkey`].
128 /// Default value: true.
130 /// [`SignerProvider::get_shutdown_scriptpubkey`]: crate::sign::SignerProvider::get_shutdown_scriptpubkey
131 pub commit_upfront_shutdown_pubkey: bool,
132 /// The Proportion of the channel value to configure as counterparty's channel reserve,
133 /// i.e., `their_channel_reserve_satoshis` for both outbound and inbound channels.
135 /// `their_channel_reserve_satoshis` is the minimum balance that the other node has to maintain
136 /// on their side, at all times.
137 /// This ensures that if our counterparty broadcasts a revoked state, we can punish them by
138 /// claiming at least this value on chain.
140 /// Channel reserve values greater than 30% could be considered highly unreasonable, since that
141 /// amount can never be used for payments.
142 /// Also, if our selected channel reserve for counterparty and counterparty's selected
143 /// channel reserve for us sum up to equal or greater than channel value, channel negotiations
146 /// Note: Versions of LDK earlier than v0.0.104 will fail to read channels with any channel reserve
147 /// other than the default value.
149 /// Default value: 1% of channel value, i.e., configured as 10,000 millionths.
150 /// Minimum value: If the calculated proportional value is less than 1000 sats, it will be treated
151 /// as 1000 sats instead, which is a safe implementation-specific lower bound.
152 /// Maximum value: 1,000,000, any values larger than 1 Million will be treated as 1 Million (or 100%)
153 /// instead, although channel negotiations will fail in that case.
154 pub their_channel_reserve_proportional_millionths: u32,
155 /// If set, we attempt to negotiate the `anchors_zero_fee_htlc_tx`option for all future
156 /// channels. This feature requires having a reserve of onchain funds readily available to bump
157 /// transactions in the event of a channel force close to avoid the possibility of losing funds.
159 /// Note that if you wish accept inbound channels with anchor outputs, you must enable
160 /// [`UserConfig::manually_accept_inbound_channels`] and manually accept them with
161 /// [`ChannelManager::accept_inbound_channel`]. This is done to give you the chance to check
162 /// whether your reserve of onchain funds is enough to cover the fees for all existing and new
163 /// channels featuring anchor outputs in the event of a force close.
165 /// If this option is set, channels may be created that will not be readable by LDK versions
166 /// prior to 0.0.116, causing [`ChannelManager`]'s read method to return a
167 /// [`DecodeError::InvalidValue`].
169 /// Note that setting this to true does *not* prevent us from opening channels with
170 /// counterparties that do not support the `anchors_zero_fee_htlc_tx` option; we will simply
171 /// fall back to a `static_remote_key` channel.
173 /// LDK will not support the legacy `option_anchors` commitment version due to a discovered
174 /// vulnerability after its deployment. For more context, see the [`SIGHASH_SINGLE + update_fee
175 /// Considered Harmful`] mailing list post.
177 /// Default value: false. This value is likely to change to true in the future.
179 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
180 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
181 /// [`DecodeError::InvalidValue`]: crate::ln::msgs::DecodeError::InvalidValue
182 /// [`SIGHASH_SINGLE + update_fee Considered Harmful`]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-September/002796.html
183 pub negotiate_anchors_zero_fee_htlc_tx: bool,
185 /// The maximum number of HTLCs in-flight from our counterparty towards us at the same time.
187 /// Increasing the value can help improve liquidity and stability in
188 /// routing at the cost of higher long term disk / DB usage.
190 /// Note: Versions of LDK earlier than v0.0.115 will fail to read channels with a configuration
191 /// other than the default value.
193 /// Default value: 50
194 /// Maximum value: 483, any values larger will be treated as 483.
195 /// This is the BOLT #2 spec limit on `max_accepted_htlcs`.
196 pub our_max_accepted_htlcs: u16,
199 impl Default for ChannelHandshakeConfig {
200 fn default() -> ChannelHandshakeConfig {
201 ChannelHandshakeConfig {
203 our_to_self_delay: BREAKDOWN_TIMEOUT,
204 our_htlc_minimum_msat: 1,
205 max_inbound_htlc_value_in_flight_percent_of_channel: 10,
206 negotiate_scid_privacy: false,
207 announced_channel: false,
208 commit_upfront_shutdown_pubkey: true,
209 their_channel_reserve_proportional_millionths: 10_000,
210 negotiate_anchors_zero_fee_htlc_tx: false,
211 our_max_accepted_htlcs: 50,
216 // When fuzzing, we want to allow the fuzzer to pick any configuration parameters. Thus, we
217 // implement Readable here in a naive way (which is a bit easier for the fuzzer to handle). We
218 // don't really want to ever expose this to users (if we did we'd want to use TLVs).
220 impl Readable for ChannelHandshakeConfig {
221 fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
223 minimum_depth: Readable::read(reader)?,
224 our_to_self_delay: Readable::read(reader)?,
225 our_htlc_minimum_msat: Readable::read(reader)?,
226 max_inbound_htlc_value_in_flight_percent_of_channel: Readable::read(reader)?,
227 negotiate_scid_privacy: Readable::read(reader)?,
228 announced_channel: Readable::read(reader)?,
229 commit_upfront_shutdown_pubkey: Readable::read(reader)?,
230 their_channel_reserve_proportional_millionths: Readable::read(reader)?,
231 negotiate_anchors_zero_fee_htlc_tx: Readable::read(reader)?,
232 our_max_accepted_htlcs: Readable::read(reader)?,
237 /// Optional channel limits which are applied during channel creation.
239 /// These limits are only applied to our counterparty's limits, not our own.
241 /// Use 0/`<type>::max_value()` as appropriate to skip checking.
243 /// Provides sane defaults for most configurations.
245 /// Most additional limits are disabled except those with which specify a default in individual
246 /// field documentation. Note that this may result in barely-usable channels, but since they
247 /// are applied mostly only to incoming channels that's not much of a problem.
248 #[derive(Copy, Clone, Debug)]
249 pub struct ChannelHandshakeLimits {
250 /// Minimum allowed satoshis when a channel is funded. This is supplied by the sender and so
251 /// only applies to inbound channels.
253 /// Default value: 0.
254 pub min_funding_satoshis: u64,
255 /// Maximum allowed satoshis when a channel is funded. This is supplied by the sender and so
256 /// only applies to inbound channels.
258 /// Default value: 2^24 - 1.
259 pub max_funding_satoshis: u64,
260 /// The remote node sets a limit on the minimum size of HTLCs we can send to them. This allows
261 /// you to limit the maximum minimum-size they can require.
263 /// Default value: u64::max_value.
264 pub max_htlc_minimum_msat: u64,
265 /// The remote node sets a limit on the maximum value of pending HTLCs to them at any given
266 /// time to limit their funds exposure to HTLCs. This allows you to set a minimum such value.
268 /// Default value: 0.
269 pub min_max_htlc_value_in_flight_msat: u64,
270 /// The remote node will require we keep a certain amount in direct payment to ourselves at all
271 /// time, ensuring that we are able to be punished if we broadcast an old state. This allows to
272 /// you limit the amount which we will have to keep to ourselves (and cannot use for HTLCs).
274 /// Default value: u64::max_value.
275 pub max_channel_reserve_satoshis: u64,
276 /// The remote node sets a limit on the maximum number of pending HTLCs to them at any given
277 /// time. This allows you to set a minimum such value.
279 /// Default value: 0.
280 pub min_max_accepted_htlcs: u16,
281 /// Before a channel is usable the funding transaction will need to be confirmed by at least a
282 /// certain number of blocks, specified by the node which is not the funder (as the funder can
283 /// assume they aren't going to double-spend themselves).
284 /// This config allows you to set a limit on the maximum amount of time to wait.
286 /// Default value: 144, or roughly one day and only applies to outbound channels.
287 pub max_minimum_depth: u32,
288 /// Whether we implicitly trust funding transactions generated by us for our own outbound
289 /// channels to not be double-spent.
291 /// If this is set, we assume that our own funding transactions are *never* double-spent, and
292 /// thus we can trust them without any confirmations. This is generally a reasonable
293 /// assumption, given we're the only ones who could ever double-spend it (assuming we have sole
294 /// control of the signing keys).
296 /// You may wish to un-set this if you allow the user to (or do in an automated fashion)
297 /// double-spend the funding transaction to RBF with an alternative channel open.
299 /// This only applies if our counterparty set their confirmations-required value to 0, and we
300 /// always trust our own funding transaction at 1 confirmation irrespective of this value.
301 /// Thus, this effectively acts as a `min_minimum_depth`, with the only possible values being
302 /// `true` (0) and `false` (1).
304 /// Default value: true
305 pub trust_own_funding_0conf: bool,
306 /// Set to force an incoming channel to match our announced channel preference in
307 /// [`ChannelHandshakeConfig::announced_channel`].
309 /// For a node which is not online reliably, this should be set to true and
310 /// [`ChannelHandshakeConfig::announced_channel`] set to false, ensuring that no announced (aka public)
311 /// channels will ever be opened.
313 /// Default value: true.
314 pub force_announced_channel_preference: bool,
315 /// Set to the amount of time we're willing to wait to claim money back to us.
317 /// Not checking this value would be a security issue, as our peer would be able to set it to
318 /// max relative lock-time (a year) and we would "lose" money as it would be locked for a long time.
320 /// Default value: 2016, which we also enforce as a maximum value so you can tweak config to
321 /// reduce the loss of having useless locked funds (if your peer accepts)
322 pub their_to_self_delay: u16
325 impl Default for ChannelHandshakeLimits {
326 fn default() -> Self {
327 ChannelHandshakeLimits {
328 min_funding_satoshis: 0,
329 max_funding_satoshis: MAX_FUNDING_SATOSHIS_NO_WUMBO,
330 max_htlc_minimum_msat: <u64>::max_value(),
331 min_max_htlc_value_in_flight_msat: 0,
332 max_channel_reserve_satoshis: <u64>::max_value(),
333 min_max_accepted_htlcs: 0,
334 trust_own_funding_0conf: true,
335 max_minimum_depth: 144,
336 force_announced_channel_preference: true,
337 their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT,
342 // When fuzzing, we want to allow the fuzzer to pick any configuration parameters. Thus, we
343 // implement Readable here in a naive way (which is a bit easier for the fuzzer to handle). We
344 // don't really want to ever expose this to users (if we did we'd want to use TLVs).
346 impl Readable for ChannelHandshakeLimits {
347 fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
349 min_funding_satoshis: Readable::read(reader)?,
350 max_funding_satoshis: Readable::read(reader)?,
351 max_htlc_minimum_msat: Readable::read(reader)?,
352 min_max_htlc_value_in_flight_msat: Readable::read(reader)?,
353 max_channel_reserve_satoshis: Readable::read(reader)?,
354 min_max_accepted_htlcs: Readable::read(reader)?,
355 trust_own_funding_0conf: Readable::read(reader)?,
356 max_minimum_depth: Readable::read(reader)?,
357 force_announced_channel_preference: Readable::read(reader)?,
358 their_to_self_delay: Readable::read(reader)?,
363 /// Options for how to set the max dust exposure allowed on a channel. See
364 /// [`ChannelConfig::max_dust_htlc_exposure`] for details.
365 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
366 pub enum MaxDustHTLCExposure {
367 /// This sets a fixed limit on the total dust exposure in millisatoshis. Setting this too low
368 /// may prevent the sending or receipt of low-value HTLCs on high-traffic nodes, however this
369 /// limit is very important to prevent stealing of large amounts of dust HTLCs by miners
370 /// through [fee griefing
371 /// attacks](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-May/002714.html).
373 /// Note that if the feerate increases significantly, without a manual increase
374 /// to this maximum the channel may be unable to send/receive HTLCs between the maximum dust
375 /// exposure and the new minimum value for HTLCs to be economically viable to claim.
377 /// This sets a multiplier on the [`ConfirmationTarget::OnChainSweep`] feerate (in sats/KW) to
378 /// determine the maximum allowed dust exposure. If this variant is used then the maximum dust
379 /// exposure in millisatoshis is calculated as:
380 /// `feerate_per_kw * value`. For example, with our default value
381 /// `FeeRateMultiplier(10_000)`:
383 /// - For the minimum fee rate of 1 sat/vByte (250 sat/KW, although the minimum
384 /// defaults to 253 sats/KW for rounding, see [`FeeEstimator`]), the max dust exposure would
385 /// be 253 * 10_000 = 2,530,000 msats.
386 /// - For a fee rate of 30 sat/vByte (7500 sat/KW), the max dust exposure would be
387 /// 7500 * 50_000 = 75,000,000 msats (0.00075 BTC).
389 /// Note, if you're using a third-party fee estimator, this may leave you more exposed to a
390 /// fee griefing attack, where your fee estimator may purposely overestimate the fee rate,
391 /// causing you to accept more dust HTLCs than you would otherwise.
393 /// This variant is primarily meant to serve pre-anchor channels, as HTLC fees being included
394 /// on HTLC outputs means your channel may be subject to more dust exposure in the event of
395 /// increases in fee rate.
397 /// # Backwards Compatibility
398 /// This variant only became available in LDK 0.0.116, so if you downgrade to a prior version
399 /// by default this will be set to a [`Self::FixedLimitMsat`] of 5,000,000 msat.
401 /// [`FeeEstimator`]: crate::chain::chaininterface::FeeEstimator
402 /// [`ConfirmationTarget::OnChainSweep`]: crate::chain::chaininterface::ConfirmationTarget::OnChainSweep
403 FeeRateMultiplier(u64),
406 impl_writeable_tlv_based_enum!(MaxDustHTLCExposure, ;
408 (3, FeeRateMultiplier),
411 /// Options which apply on a per-channel basis and may change at runtime or based on negotiation
412 /// with our counterparty.
413 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
414 pub struct ChannelConfig {
415 /// Amount (in millionths of a satoshi) charged per satoshi for payments forwarded outbound
416 /// over the channel.
417 /// This may be allowed to change at runtime in a later update, however doing so must result in
418 /// update messages sent to notify all nodes of our updated relay fee.
420 /// Default value: 0.
421 pub forwarding_fee_proportional_millionths: u32,
422 /// Amount (in milli-satoshi) charged for payments forwarded outbound over the channel, in
423 /// excess of [`forwarding_fee_proportional_millionths`].
424 /// This may be allowed to change at runtime in a later update, however doing so must result in
425 /// update messages sent to notify all nodes of our updated relay fee.
427 /// The default value of a single satoshi roughly matches the market rate on many routing nodes
428 /// as of July 2021. Adjusting it upwards or downwards may change whether nodes route through
431 /// Default value: 1000.
433 /// [`forwarding_fee_proportional_millionths`]: ChannelConfig::forwarding_fee_proportional_millionths
434 pub forwarding_fee_base_msat: u32,
435 /// The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded over
436 /// the channel this config applies to.
438 /// This is analogous to [`ChannelHandshakeConfig::our_to_self_delay`] but applies to in-flight
439 /// HTLC balance when a channel appears on-chain whereas
440 /// [`ChannelHandshakeConfig::our_to_self_delay`] applies to the remaining
441 /// (non-HTLC-encumbered) balance.
443 /// Thus, for HTLC-encumbered balances to be enforced on-chain when a channel is force-closed,
444 /// we (or one of our watchtowers) MUST be online to check for broadcast of the current
445 /// commitment transaction at least once per this many blocks (minus some margin to allow us
446 /// enough time to broadcast and confirm a transaction, possibly with time in between to RBF
447 /// the spending transaction).
449 /// Default value: 72 (12 hours at an average of 6 blocks/hour).
450 /// Minimum value: [`MIN_CLTV_EXPIRY_DELTA`], any values less than this will be treated as
451 /// [`MIN_CLTV_EXPIRY_DELTA`] instead.
453 /// [`MIN_CLTV_EXPIRY_DELTA`]: crate::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA
454 pub cltv_expiry_delta: u16,
455 /// Limit our total exposure to potential loss to on-chain fees on close, including in-flight
456 /// HTLCs which are burned to fees as they are too small to claim on-chain and fees on
457 /// commitment transaction(s) broadcasted by our counterparty in excess of our own fee estimate.
459 /// # HTLC-based Dust Exposure
461 /// When an HTLC present in one of our channels is below a "dust" threshold, the HTLC will
462 /// not be claimable on-chain, instead being turned into additional miner fees if either
463 /// party force-closes the channel. Because the threshold is per-HTLC, our total exposure
464 /// to such payments may be substantial if there are many dust HTLCs present when the
465 /// channel is force-closed.
467 /// The dust threshold for each HTLC is based on the `dust_limit_satoshis` for each party in a
468 /// channel negotiated throughout the channel open process, along with the fees required to have
469 /// a broadcastable HTLC spending transaction. When a channel supports anchor outputs
470 /// (specifically the zero fee HTLC transaction variant), this threshold no longer takes into
471 /// account the HTLC transaction fee as it is zero. Because of this, you may want to set this
472 /// value to a fixed limit for channels using anchor outputs, while the fee rate multiplier
473 /// variant is primarily intended for use with pre-anchor channels.
475 /// The selected limit is applied for sent, forwarded, and received HTLCs and limits the total
476 /// exposure across all three types per-channel.
478 /// # Transaction Fee Dust Exposure
480 /// Further, counterparties broadcasting a commitment transaction in a force-close may result
481 /// in other balance being burned to fees, and thus all fees on commitment and HTLC
482 /// transactions in excess of our local fee estimates are included in the dust calculation.
484 /// Because of this, another way to look at this limit is to divide it by 43,000 (or 218,750
485 /// for non-anchor channels) and see it as the maximum feerate disagreement (in sats/vB) per
486 /// non-dust HTLC we're allowed to have with our peers before risking a force-closure for
487 /// inbound channels.
488 // This works because, for anchor channels the on-chain cost is 172 weight (172+703 for
489 // non-anchors with an HTLC-Success transaction), i.e.
490 // dust_exposure_limit_msat / 1000 = 172 * feerate_in_sat_per_vb / 4 * HTLC count
491 // dust_exposure_limit_msat = 43,000 * feerate_in_sat_per_vb * HTLC count
492 // dust_exposure_limit_msat / HTLC count / 43,000 = feerate_in_sat_per_vb
494 /// Thus, for the default value of 10_000 * a current feerate estimate of 10 sat/vB (or 2,500
495 /// sat/KW), we risk force-closure if we disagree with our peer by:
496 /// * `10_000 * 2_500 / 43_000 / (483*2)` = 0.6 sat/vB for anchor channels with 483 HTLCs in
497 /// both directions (the maximum),
498 /// * `10_000 * 2_500 / 43_000 / (50*2)` = 5.8 sat/vB for anchor channels with 50 HTLCs in both
499 /// directions (the LDK default max from [`ChannelHandshakeConfig::our_max_accepted_htlcs`])
500 /// * `10_000 * 2_500 / 218_750 / (483*2)` = 0.1 sat/vB for non-anchor channels with 483 HTLCs
501 /// in both directions (the maximum),
502 /// * `10_000 * 2_500 / 218_750 / (50*2)` = 1.1 sat/vB for non-anchor channels with 50 HTLCs
503 /// in both (the LDK default maximum from [`ChannelHandshakeConfig::our_max_accepted_htlcs`])
505 /// Note that when using [`MaxDustHTLCExposure::FeeRateMultiplier`] this maximum disagreement
506 /// will scale linearly with increases (or decreases) in the our feerate estimates. Further,
507 /// for anchor channels we expect our counterparty to use a relatively low feerate estimate
508 /// while we use [`ConfirmationTarget::OnChainSweep`] (which should be relatively high) and
509 /// feerate disagreement force-closures should only occur when theirs is higher than ours.
511 /// Default value: [`MaxDustHTLCExposure::FeeRateMultiplier`] with a multiplier of 10_000.
513 /// [`ConfirmationTarget::OnChainSweep`]: crate::chain::chaininterface::ConfirmationTarget::OnChainSweep
514 pub max_dust_htlc_exposure: MaxDustHTLCExposure,
515 /// The additional fee we're willing to pay to avoid waiting for the counterparty's
516 /// `to_self_delay` to reclaim funds.
518 /// When we close a channel cooperatively with our counterparty, we negotiate a fee for the
519 /// closing transaction which both sides find acceptable, ultimately paid by the channel
520 /// funder/initiator.
522 /// When we are the funder, because we have to pay the channel closing fee, we bound the
523 /// acceptable fee by our [`ChannelCloseMinimum`] and [`NonAnchorChannelFee`] fees, with the upper bound increased by
524 /// this value. Because the on-chain fee we'd pay to force-close the channel is kept near our
525 /// [`NonAnchorChannelFee`] feerate during normal operation, this value represents the additional fee we're
526 /// willing to pay in order to avoid waiting for our counterparty's to_self_delay to reclaim our
529 /// When we are not the funder, we require the closing transaction fee pay at least our
530 /// [`ChannelCloseMinimum`] fee estimate, but allow our counterparty to pay as much fee as they like.
531 /// Thus, this value is ignored when we are not the funder.
533 /// Default value: 1000 satoshis.
535 /// [`NonAnchorChannelFee`]: crate::chain::chaininterface::ConfirmationTarget::NonAnchorChannelFee
536 /// [`ChannelCloseMinimum`]: crate::chain::chaininterface::ConfirmationTarget::ChannelCloseMinimum
537 pub force_close_avoidance_max_fee_satoshis: u64,
538 /// If set, allows this channel's counterparty to skim an additional fee off this node's inbound
539 /// HTLCs. Useful for liquidity providers to offload on-chain channel costs to end users.
542 /// - The payee will set this option and set its invoice route hints to use [intercept scids]
543 /// generated by this channel's counterparty.
544 /// - The counterparty will get an [`HTLCIntercepted`] event upon payment forward, and call
545 /// [`forward_intercepted_htlc`] with less than the amount provided in
546 /// [`HTLCIntercepted::expected_outbound_amount_msat`]. The difference between the expected and
547 /// actual forward amounts is their fee. See
548 /// <https://github.com/BitcoinAndLightningLayerSpecs/lsp/tree/main/LSPS2#flow-lsp-trusts-client-model>
549 /// for how this feature may be used in the LSP use case.
552 /// It's important for payee wallet software to verify that [`PaymentClaimable::amount_msat`] is
553 /// as-expected if this feature is activated, otherwise they may lose money!
554 /// [`PaymentClaimable::counterparty_skimmed_fee_msat`] provides the fee taken by the
558 /// Switching this config flag on may break compatibility with versions of LDK prior to 0.0.116.
559 /// Unsetting this flag between restarts may lead to payment receive failures.
561 /// Default value: false.
563 /// [intercept scids]: crate::ln::channelmanager::ChannelManager::get_intercept_scid
564 /// [`forward_intercepted_htlc`]: crate::ln::channelmanager::ChannelManager::forward_intercepted_htlc
565 /// [`HTLCIntercepted`]: crate::events::Event::HTLCIntercepted
566 /// [`HTLCIntercepted::expected_outbound_amount_msat`]: crate::events::Event::HTLCIntercepted::expected_outbound_amount_msat
567 /// [`PaymentClaimable::amount_msat`]: crate::events::Event::PaymentClaimable::amount_msat
568 /// [`PaymentClaimable::counterparty_skimmed_fee_msat`]: crate::events::Event::PaymentClaimable::counterparty_skimmed_fee_msat
569 // TODO: link to bLIP when it's merged
570 pub accept_underpaying_htlcs: bool,
574 /// Applies the given [`ChannelConfigUpdate`] as a partial update to the [`ChannelConfig`].
575 pub fn apply(&mut self, update: &ChannelConfigUpdate) {
576 if let Some(forwarding_fee_proportional_millionths) = update.forwarding_fee_proportional_millionths {
577 self.forwarding_fee_proportional_millionths = forwarding_fee_proportional_millionths;
579 if let Some(forwarding_fee_base_msat) = update.forwarding_fee_base_msat {
580 self.forwarding_fee_base_msat = forwarding_fee_base_msat;
582 if let Some(cltv_expiry_delta) = update.cltv_expiry_delta {
583 self.cltv_expiry_delta = cltv_expiry_delta;
585 if let Some(max_dust_htlc_exposure_msat) = update.max_dust_htlc_exposure_msat {
586 self.max_dust_htlc_exposure = max_dust_htlc_exposure_msat;
588 if let Some(force_close_avoidance_max_fee_satoshis) = update.force_close_avoidance_max_fee_satoshis {
589 self.force_close_avoidance_max_fee_satoshis = force_close_avoidance_max_fee_satoshis;
594 impl Default for ChannelConfig {
595 /// Provides sane defaults for most configurations (but with zero relay fees!).
596 fn default() -> Self {
598 forwarding_fee_proportional_millionths: 0,
599 forwarding_fee_base_msat: 1000,
600 cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
601 max_dust_htlc_exposure: MaxDustHTLCExposure::FeeRateMultiplier(10000),
602 force_close_avoidance_max_fee_satoshis: 1000,
603 accept_underpaying_htlcs: false,
608 impl crate::util::ser::Writeable for ChannelConfig {
609 fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), crate::io::Error> {
610 let max_dust_htlc_exposure_msat_fixed_limit = match self.max_dust_htlc_exposure {
611 MaxDustHTLCExposure::FixedLimitMsat(limit) => limit,
612 MaxDustHTLCExposure::FeeRateMultiplier(_) => 5_000_000,
614 write_tlv_fields!(writer, {
615 (0, self.forwarding_fee_proportional_millionths, required),
616 (1, self.accept_underpaying_htlcs, (default_value, false)),
617 (2, self.forwarding_fee_base_msat, required),
618 (3, self.max_dust_htlc_exposure, required),
619 (4, self.cltv_expiry_delta, required),
620 (6, max_dust_htlc_exposure_msat_fixed_limit, required),
621 // ChannelConfig serialized this field with a required type of 8 prior to the introduction of
622 // LegacyChannelConfig. To make sure that serialization is not compatible with this one, we use
623 // the next required type of 10, which if seen by the old serialization will always fail.
624 (10, self.force_close_avoidance_max_fee_satoshis, required),
630 impl crate::util::ser::Readable for ChannelConfig {
631 fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
632 let mut forwarding_fee_proportional_millionths = 0;
633 let mut accept_underpaying_htlcs = false;
634 let mut forwarding_fee_base_msat = 1000;
635 let mut cltv_expiry_delta = 6 * 12;
636 let mut max_dust_htlc_exposure_msat = None;
637 let mut max_dust_htlc_exposure_enum = None;
638 let mut force_close_avoidance_max_fee_satoshis = 1000;
639 read_tlv_fields!(reader, {
640 (0, forwarding_fee_proportional_millionths, required),
641 (1, accept_underpaying_htlcs, (default_value, false)),
642 (2, forwarding_fee_base_msat, required),
643 (3, max_dust_htlc_exposure_enum, option),
644 (4, cltv_expiry_delta, required),
645 // Has always been written, but became optionally read in 0.0.116
646 (6, max_dust_htlc_exposure_msat, option),
647 (10, force_close_avoidance_max_fee_satoshis, required),
649 let max_dust_htlc_fixed_limit = max_dust_htlc_exposure_msat.unwrap_or(5_000_000);
650 let max_dust_htlc_exposure_msat = max_dust_htlc_exposure_enum
651 .unwrap_or(MaxDustHTLCExposure::FixedLimitMsat(max_dust_htlc_fixed_limit));
653 forwarding_fee_proportional_millionths,
654 accept_underpaying_htlcs,
655 forwarding_fee_base_msat,
657 max_dust_htlc_exposure: max_dust_htlc_exposure_msat,
658 force_close_avoidance_max_fee_satoshis,
663 /// A parallel struct to [`ChannelConfig`] to define partial updates.
664 #[allow(missing_docs)]
665 pub struct ChannelConfigUpdate {
666 pub forwarding_fee_proportional_millionths: Option<u32>,
667 pub forwarding_fee_base_msat: Option<u32>,
668 pub cltv_expiry_delta: Option<u16>,
669 pub max_dust_htlc_exposure_msat: Option<MaxDustHTLCExposure>,
670 pub force_close_avoidance_max_fee_satoshis: Option<u64>,
673 impl Default for ChannelConfigUpdate {
674 fn default() -> ChannelConfigUpdate {
675 ChannelConfigUpdate {
676 forwarding_fee_proportional_millionths: None,
677 forwarding_fee_base_msat: None,
678 cltv_expiry_delta: None,
679 max_dust_htlc_exposure_msat: None,
680 force_close_avoidance_max_fee_satoshis: None,
685 impl From<ChannelConfig> for ChannelConfigUpdate {
686 fn from(config: ChannelConfig) -> ChannelConfigUpdate {
687 ChannelConfigUpdate {
688 forwarding_fee_proportional_millionths: Some(config.forwarding_fee_proportional_millionths),
689 forwarding_fee_base_msat: Some(config.forwarding_fee_base_msat),
690 cltv_expiry_delta: Some(config.cltv_expiry_delta),
691 max_dust_htlc_exposure_msat: Some(config.max_dust_htlc_exposure),
692 force_close_avoidance_max_fee_satoshis: Some(config.force_close_avoidance_max_fee_satoshis),
697 /// Legacy version of [`ChannelConfig`] that stored the static
698 /// [`ChannelHandshakeConfig::announced_channel`] and
699 /// [`ChannelHandshakeConfig::commit_upfront_shutdown_pubkey`] fields.
700 #[derive(Copy, Clone, Debug)]
701 pub(crate) struct LegacyChannelConfig {
702 pub(crate) options: ChannelConfig,
703 /// Deprecated but may still be read from. See [`ChannelHandshakeConfig::announced_channel`] to
704 /// set this when opening/accepting a channel.
705 pub(crate) announced_channel: bool,
706 /// Deprecated but may still be read from. See
707 /// [`ChannelHandshakeConfig::commit_upfront_shutdown_pubkey`] to set this when
708 /// opening/accepting a channel.
709 pub(crate) commit_upfront_shutdown_pubkey: bool,
712 impl Default for LegacyChannelConfig {
713 fn default() -> Self {
715 options: ChannelConfig::default(),
716 announced_channel: false,
717 commit_upfront_shutdown_pubkey: true,
722 impl crate::util::ser::Writeable for LegacyChannelConfig {
723 fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), crate::io::Error> {
724 let max_dust_htlc_exposure_msat_fixed_limit = match self.options.max_dust_htlc_exposure {
725 MaxDustHTLCExposure::FixedLimitMsat(limit) => limit,
726 MaxDustHTLCExposure::FeeRateMultiplier(_) => 5_000_000,
728 write_tlv_fields!(writer, {
729 (0, self.options.forwarding_fee_proportional_millionths, required),
730 (1, max_dust_htlc_exposure_msat_fixed_limit, required),
731 (2, self.options.cltv_expiry_delta, required),
732 (3, self.options.force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
733 (4, self.announced_channel, required),
734 (5, self.options.max_dust_htlc_exposure, required),
735 (6, self.commit_upfront_shutdown_pubkey, required),
736 (8, self.options.forwarding_fee_base_msat, required),
742 impl crate::util::ser::Readable for LegacyChannelConfig {
743 fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
744 let mut forwarding_fee_proportional_millionths = 0;
745 let mut max_dust_htlc_exposure_msat_fixed_limit = None;
746 let mut cltv_expiry_delta = 0;
747 let mut force_close_avoidance_max_fee_satoshis = 1000;
748 let mut announced_channel = false;
749 let mut commit_upfront_shutdown_pubkey = false;
750 let mut forwarding_fee_base_msat = 0;
751 let mut max_dust_htlc_exposure_enum = None;
752 read_tlv_fields!(reader, {
753 (0, forwarding_fee_proportional_millionths, required),
754 // Has always been written, but became optionally read in 0.0.116
755 (1, max_dust_htlc_exposure_msat_fixed_limit, option),
756 (2, cltv_expiry_delta, required),
757 (3, force_close_avoidance_max_fee_satoshis, (default_value, 1000u64)),
758 (4, announced_channel, required),
759 (5, max_dust_htlc_exposure_enum, option),
760 (6, commit_upfront_shutdown_pubkey, required),
761 (8, forwarding_fee_base_msat, required),
763 let max_dust_htlc_exposure_msat_fixed_limit =
764 max_dust_htlc_exposure_msat_fixed_limit.unwrap_or(5_000_000);
765 let max_dust_htlc_exposure_msat = max_dust_htlc_exposure_enum
766 .unwrap_or(MaxDustHTLCExposure::FixedLimitMsat(max_dust_htlc_exposure_msat_fixed_limit));
768 options: ChannelConfig {
769 forwarding_fee_proportional_millionths,
770 max_dust_htlc_exposure: max_dust_htlc_exposure_msat,
772 force_close_avoidance_max_fee_satoshis,
773 forwarding_fee_base_msat,
774 accept_underpaying_htlcs: false,
777 commit_upfront_shutdown_pubkey,
782 /// Top-level config which holds ChannelHandshakeLimits and ChannelConfig.
784 /// Default::default() provides sane defaults for most configurations
785 /// (but currently with 0 relay fees!)
786 #[derive(Copy, Clone, Debug)]
787 pub struct UserConfig {
788 /// Channel handshake config that we propose to our counterparty.
789 pub channel_handshake_config: ChannelHandshakeConfig,
790 /// Limits applied to our counterparty's proposed channel handshake config settings.
791 pub channel_handshake_limits: ChannelHandshakeLimits,
792 /// Channel config which affects behavior during channel lifetime.
793 pub channel_config: ChannelConfig,
794 /// If this is set to false, we will reject any HTLCs which were to be forwarded over private
795 /// channels. This prevents us from taking on HTLC-forwarding risk when we intend to run as a
796 /// node which is not online reliably.
798 /// For nodes which are not online reliably, you should set all channels to *not* be announced
799 /// (using [`ChannelHandshakeConfig::announced_channel`] and
800 /// [`ChannelHandshakeLimits::force_announced_channel_preference`]) and set this to false to
801 /// ensure you are not exposed to any forwarding risk.
803 /// Note that because you cannot change a channel's announced state after creation, there is no
804 /// way to disable forwarding on public channels retroactively. Thus, in order to change a node
805 /// from a publicly-announced forwarding node to a private non-forwarding node you must close
806 /// all your channels and open new ones. For privacy, you should also change your node_id
807 /// (swapping all private and public key material for new ones) at that time.
809 /// Default value: false.
810 pub accept_forwards_to_priv_channels: bool,
811 /// If this is set to false, we do not accept inbound requests to open a new channel.
812 /// Default value: true.
813 pub accept_inbound_channels: bool,
814 /// If this is set to true, the user needs to manually accept inbound requests to open a new
817 /// When set to true, [`Event::OpenChannelRequest`] will be triggered once a request to open a
818 /// new inbound channel is received through a [`msgs::OpenChannel`] message. In that case, a
819 /// [`msgs::AcceptChannel`] message will not be sent back to the counterparty node unless the
820 /// user explicitly chooses to accept the request.
822 /// Default value: false.
824 /// [`Event::OpenChannelRequest`]: crate::events::Event::OpenChannelRequest
825 /// [`msgs::OpenChannel`]: crate::ln::msgs::OpenChannel
826 /// [`msgs::AcceptChannel`]: crate::ln::msgs::AcceptChannel
827 pub manually_accept_inbound_channels: bool,
828 /// If this is set to true, LDK will intercept HTLCs that are attempting to be forwarded over
829 /// fake short channel ids generated via [`ChannelManager::get_intercept_scid`]. Upon HTLC
830 /// intercept, LDK will generate an [`Event::HTLCIntercepted`] which MUST be handled by the user.
832 /// Setting this to true may break backwards compatibility with LDK versions < 0.0.113.
834 /// Default value: false.
836 /// [`ChannelManager::get_intercept_scid`]: crate::ln::channelmanager::ChannelManager::get_intercept_scid
837 /// [`Event::HTLCIntercepted`]: crate::events::Event::HTLCIntercepted
838 pub accept_intercept_htlcs: bool,
839 /// If this is set to false, when receiving a keysend payment we'll fail it if it has multiple
840 /// parts. If this is set to true, we'll accept the payment.
842 /// Setting this to true will break backwards compatibility upon downgrading to an LDK
843 /// version < 0.0.116 while receiving an MPP keysend. If we have already received an MPP
844 /// keysend, downgrading will cause us to fail to deserialize [`ChannelManager`].
846 /// Default value: false.
848 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
849 pub accept_mpp_keysend: bool,
852 impl Default for UserConfig {
853 fn default() -> Self {
855 channel_handshake_config: ChannelHandshakeConfig::default(),
856 channel_handshake_limits: ChannelHandshakeLimits::default(),
857 channel_config: ChannelConfig::default(),
858 accept_forwards_to_priv_channels: false,
859 accept_inbound_channels: true,
860 manually_accept_inbound_channels: false,
861 accept_intercept_htlcs: false,
862 accept_mpp_keysend: false,
867 // When fuzzing, we want to allow the fuzzer to pick any configuration parameters. Thus, we
868 // implement Readable here in a naive way (which is a bit easier for the fuzzer to handle). We
869 // don't really want to ever expose this to users (if we did we'd want to use TLVs).
871 impl Readable for UserConfig {
872 fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
874 channel_handshake_config: Readable::read(reader)?,
875 channel_handshake_limits: Readable::read(reader)?,
876 channel_config: Readable::read(reader)?,
877 accept_forwards_to_priv_channels: Readable::read(reader)?,
878 accept_inbound_channels: Readable::read(reader)?,
879 manually_accept_inbound_channels: Readable::read(reader)?,
880 accept_intercept_htlcs: Readable::read(reader)?,
881 accept_mpp_keysend: Readable::read(reader)?,