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 ln::channel::MAX_FUNDING_SATOSHIS_NO_WUMBO;
14 use ln::channelmanager::{BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
16 /// Configuration we set when applicable.
18 /// Default::default() provides sane defaults.
19 #[derive(Copy, Clone, Debug)]
20 pub struct ChannelHandshakeConfig {
21 /// Confirmations we will wait for before considering the channel locked in.
22 /// Applied only for inbound channels (see ChannelHandshakeLimits::max_minimum_depth for the
23 /// equivalent limit applied to outbound channels).
25 /// A lower-bound of 1 is applied, requiring all channels to have a confirmed commitment
26 /// transaction before operation. If you wish to accept channels with zero confirmations, see
27 /// [`UserConfig::manually_accept_inbound_channels`] and
28 /// [`ChannelManager::accept_inbound_channel_from_trusted_peer_0conf`].
32 /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
33 /// [`ChannelManager::accept_inbound_channel_from_trusted_peer_0conf`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel_from_trusted_peer_0conf
34 pub minimum_depth: u32,
35 /// Set to the number of blocks we require our counterparty to wait to claim their money (ie
36 /// the number of blocks we have to punish our counterparty if they broadcast a revoked
39 /// This is one of the main parameters of our security model. We (or one of our watchtowers) MUST
40 /// be online to check for revoked transactions on-chain at least once every our_to_self_delay
41 /// blocks (minus some margin to allow us enough time to broadcast and confirm a transaction,
42 /// possibly with time in between to RBF the spending transaction).
44 /// Meanwhile, asking for a too high delay, we bother peer to freeze funds for nothing in
45 /// case of an honest unilateral channel close, which implicitly decrease the economic value of
48 /// Default value: [`BREAKDOWN_TIMEOUT`], we enforce it as a minimum at channel opening so you
49 /// can tweak config to ask for more security, not less.
50 pub our_to_self_delay: u16,
51 /// Set to the smallest value HTLC we will accept to process.
53 /// This value is sent to our counterparty on channel-open and we close the channel any time
54 /// our counterparty misbehaves by sending us an HTLC with a value smaller than this.
56 /// Default value: 1. If the value is less than 1, it is ignored and set to 1, as is required
58 pub our_htlc_minimum_msat: u64,
59 /// Sets the percentage of the channel value we will cap the total value of outstanding inbound
62 /// This can be set to a value between 1-100, where the value corresponds to the percent of the
63 /// channel value in whole percentages.
66 /// * If configured to another value than the default value 10, any new channels created with
67 /// the non default value will cause versions of LDK prior to 0.0.104 to refuse to read the
70 /// * This caps the total value for inbound HTLCs in-flight only, and there's currently
71 /// no way to configure the cap for the total value of outbound HTLCs in-flight.
73 /// * The requirements for your node being online to ensure the safety of HTLC-encumbered funds
74 /// are different from the non-HTLC-encumbered funds. This makes this an important knob to
75 /// restrict exposure to loss due to being offline for too long.
76 /// See [`ChannelHandshakeConfig::our_to_self_delay`] and [`ChannelConfig::cltv_expiry_delta`]
77 /// for more information.
79 /// Default value: 10.
80 /// Minimum value: 1, any values less than 1 will be treated as 1 instead.
81 /// Maximum value: 100, any values larger than 100 will be treated as 100 instead.
82 pub max_inbound_htlc_value_in_flight_percent_of_channel: u8,
83 /// If set, we attempt to negotiate the `scid_privacy` (referred to as `scid_alias` in the
84 /// BOLTs) option for outbound private channels. This provides better privacy by not including
85 /// our real on-chain channel UTXO in each invoice and requiring that our counterparty only
86 /// relay HTLCs to us using the channel's SCID alias.
88 /// If this option is set, channels may be created that will not be readable by LDK versions
89 /// prior to 0.0.106, causing [`ChannelManager`]'s read method to return a
90 /// [`DecodeError:InvalidValue`].
92 /// Note that setting this to true does *not* prevent us from opening channels with
93 /// counterparties that do not support the `scid_alias` option; we will simply fall back to a
94 /// private channel without that option.
96 /// Ignored if the channel is negotiated to be announced, see
97 /// [`ChannelConfig::announced_channel`] and
98 /// [`ChannelHandshakeLimits::force_announced_channel_preference`] for more.
100 /// Default value: false. This value is likely to change to true in the future.
102 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
103 /// [`DecodeError:InvalidValue`]: crate::ln::msgs::DecodeError::InvalidValue
104 pub negotiate_scid_privacy: bool,
107 impl Default for ChannelHandshakeConfig {
108 fn default() -> ChannelHandshakeConfig {
109 ChannelHandshakeConfig {
111 our_to_self_delay: BREAKDOWN_TIMEOUT,
112 our_htlc_minimum_msat: 1,
113 max_inbound_htlc_value_in_flight_percent_of_channel: 10,
114 negotiate_scid_privacy: false,
119 /// Optional channel limits which are applied during channel creation.
121 /// These limits are only applied to our counterparty's limits, not our own.
123 /// Use 0/<type>::max_value() as appropriate to skip checking.
125 /// Provides sane defaults for most configurations.
127 /// Most additional limits are disabled except those with which specify a default in individual
128 /// field documentation. Note that this may result in barely-usable channels, but since they
129 /// are applied mostly only to incoming channels that's not much of a problem.
130 #[derive(Copy, Clone, Debug)]
131 pub struct ChannelHandshakeLimits {
132 /// Minimum allowed satoshis when a channel is funded. This is supplied by the sender and so
133 /// only applies to inbound channels.
135 /// Default value: 0.
136 pub min_funding_satoshis: u64,
137 /// Maximum allowed satoshis when a channel is funded. This is supplied by the sender and so
138 /// only applies to inbound channels.
140 /// Default value: 2^24 - 1.
141 pub max_funding_satoshis: u64,
142 /// The remote node sets a limit on the minimum size of HTLCs we can send to them. This allows
143 /// you to limit the maximum minimum-size they can require.
145 /// Default value: u64::max_value.
146 pub max_htlc_minimum_msat: u64,
147 /// The remote node sets a limit on the maximum value of pending HTLCs to them at any given
148 /// time to limit their funds exposure to HTLCs. This allows you to set a minimum such value.
150 /// Default value: 0.
151 pub min_max_htlc_value_in_flight_msat: u64,
152 /// The remote node will require we keep a certain amount in direct payment to ourselves at all
153 /// time, ensuring that we are able to be punished if we broadcast an old state. This allows to
154 /// you limit the amount which we will have to keep to ourselves (and cannot use for HTLCs).
156 /// Default value: u64::max_value.
157 pub max_channel_reserve_satoshis: u64,
158 /// The remote node sets a limit on the maximum number of pending HTLCs to them at any given
159 /// time. This allows you to set a minimum such value.
161 /// Default value: 0.
162 pub min_max_accepted_htlcs: u16,
163 /// Before a channel is usable the funding transaction will need to be confirmed by at least a
164 /// certain number of blocks, specified by the node which is not the funder (as the funder can
165 /// assume they aren't going to double-spend themselves).
166 /// This config allows you to set a limit on the maximum amount of time to wait.
168 /// Default value: 144, or roughly one day and only applies to outbound channels.
169 pub max_minimum_depth: u32,
170 /// Whether we implicitly trust funding transactions generated by us for our own outbound
171 /// channels to not be double-spent.
173 /// If this is set, we assume that our own funding transactions are *never* double-spent, and
174 /// thus we can trust them without any confirmations. This is generally a reasonable
175 /// assumption, given we're the only ones who could ever double-spend it (assuming we have sole
176 /// control of the signing keys).
178 /// You may wish to un-set this if you allow the user to (or do in an automated fashion)
179 /// double-spend the funding transaction to RBF with an alternative channel open.
181 /// This only applies if our counterparty set their confirmations-required value to 0, and we
182 /// always trust our own funding transaction at 1 confirmation irrespective of this value.
183 /// Thus, this effectively acts as a `min_minimum_depth`, with the only possible values being
184 /// `true` (0) and `false` (1).
186 /// Default value: true
187 pub trust_own_funding_0conf: bool,
188 /// Set to force an incoming channel to match our announced channel preference in
189 /// [`ChannelConfig::announced_channel`].
191 /// For a node which is not online reliably, this should be set to true and
192 /// [`ChannelConfig::announced_channel`] set to false, ensuring that no announced (aka public)
193 /// channels will ever be opened.
195 /// Default value: true.
196 pub force_announced_channel_preference: bool,
197 /// Set to the amount of time we're willing to wait to claim money back to us.
199 /// Not checking this value would be a security issue, as our peer would be able to set it to
200 /// max relative lock-time (a year) and we would "lose" money as it would be locked for a long time.
202 /// Default value: 2016, which we also enforce as a maximum value so you can tweak config to
203 /// reduce the loss of having useless locked funds (if your peer accepts)
204 pub their_to_self_delay: u16
207 impl Default for ChannelHandshakeLimits {
208 fn default() -> Self {
209 ChannelHandshakeLimits {
210 min_funding_satoshis: 0,
211 max_funding_satoshis: MAX_FUNDING_SATOSHIS_NO_WUMBO,
212 max_htlc_minimum_msat: <u64>::max_value(),
213 min_max_htlc_value_in_flight_msat: 0,
214 max_channel_reserve_satoshis: <u64>::max_value(),
215 min_max_accepted_htlcs: 0,
216 trust_own_funding_0conf: true,
217 max_minimum_depth: 144,
218 force_announced_channel_preference: true,
219 their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT,
224 /// Options which apply on a per-channel basis and may change at runtime or based on negotiation
225 /// with our counterparty.
226 #[derive(Copy, Clone, Debug)]
227 pub struct ChannelConfig {
228 /// Amount (in millionths of a satoshi) charged per satoshi for payments forwarded outbound
229 /// over the channel.
230 /// This may be allowed to change at runtime in a later update, however doing so must result in
231 /// update messages sent to notify all nodes of our updated relay fee.
233 /// Default value: 0.
234 pub forwarding_fee_proportional_millionths: u32,
235 /// Amount (in milli-satoshi) charged for payments forwarded outbound over the channel, in
236 /// excess of [`forwarding_fee_proportional_millionths`].
237 /// This may be allowed to change at runtime in a later update, however doing so must result in
238 /// update messages sent to notify all nodes of our updated relay fee.
240 /// The default value of a single satoshi roughly matches the market rate on many routing nodes
241 /// as of July 2021. Adjusting it upwards or downwards may change whether nodes route through
244 /// Default value: 1000.
246 /// [`forwarding_fee_proportional_millionths`]: ChannelConfig::forwarding_fee_proportional_millionths
247 pub forwarding_fee_base_msat: u32,
248 /// The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded over
249 /// the channel this config applies to.
251 /// This is analogous to [`ChannelHandshakeConfig::our_to_self_delay`] but applies to in-flight
252 /// HTLC balance when a channel appears on-chain whereas
253 /// [`ChannelHandshakeConfig::our_to_self_delay`] applies to the remaining
254 /// (non-HTLC-encumbered) balance.
256 /// Thus, for HTLC-encumbered balances to be enforced on-chain when a channel is force-closed,
257 /// we (or one of our watchtowers) MUST be online to check for broadcast of the current
258 /// commitment transaction at least once per this many blocks (minus some margin to allow us
259 /// enough time to broadcast and confirm a transaction, possibly with time in between to RBF
260 /// the spending transaction).
262 /// Default value: 72 (12 hours at an average of 6 blocks/hour).
263 /// Minimum value: [`MIN_CLTV_EXPIRY_DELTA`], any values less than this will be treated as
264 /// [`MIN_CLTV_EXPIRY_DELTA`] instead.
266 /// [`MIN_CLTV_EXPIRY_DELTA`]: crate::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA
267 pub cltv_expiry_delta: u16,
268 /// Set to announce the channel publicly and notify all nodes that they can route via this
271 /// This should only be set to true for nodes which expect to be online reliably.
273 /// As the node which funds a channel picks this value this will only apply for new outbound
274 /// channels unless [`ChannelHandshakeLimits::force_announced_channel_preference`] is set.
276 /// This cannot be changed after the initial channel handshake.
278 /// Default value: false.
279 pub announced_channel: bool,
280 /// When set, we commit to an upfront shutdown_pubkey at channel open. If our counterparty
281 /// supports it, they will then enforce the mutual-close output to us matches what we provided
282 /// at intialization, preventing us from closing to an alternate pubkey.
284 /// This is set to true by default to provide a slight increase in security, though ultimately
285 /// any attacker who is able to take control of a channel can just as easily send the funds via
286 /// lightning payments, so we never require that our counterparties support this option.
288 /// This cannot be changed after a channel has been initialized.
290 /// Default value: true.
291 pub commit_upfront_shutdown_pubkey: bool,
292 /// Limit our total exposure to in-flight HTLCs which are burned to fees as they are too
293 /// small to claim on-chain.
295 /// When an HTLC present in one of our channels is below a "dust" threshold, the HTLC will
296 /// not be claimable on-chain, instead being turned into additional miner fees if either
297 /// party force-closes the channel. Because the threshold is per-HTLC, our total exposure
298 /// to such payments may be sustantial if there are many dust HTLCs present when the
299 /// channel is force-closed.
301 /// This limit is applied for sent, forwarded, and received HTLCs and limits the total
302 /// exposure across all three types per-channel. Setting this too low may prevent the
303 /// sending or receipt of low-value HTLCs on high-traffic nodes, and this limit is very
304 /// important to prevent stealing of dust HTLCs by miners.
306 /// Default value: 5_000_000 msat.
307 pub max_dust_htlc_exposure_msat: u64,
308 /// The additional fee we're willing to pay to avoid waiting for the counterparty's
309 /// `to_self_delay` to reclaim funds.
311 /// When we close a channel cooperatively with our counterparty, we negotiate a fee for the
312 /// closing transaction which both sides find acceptable, ultimately paid by the channel
313 /// funder/initiator.
315 /// When we are the funder, because we have to pay the channel closing fee, we bound the
316 /// acceptable fee by our [`Background`] and [`Normal`] fees, with the upper bound increased by
317 /// this value. Because the on-chain fee we'd pay to force-close the channel is kept near our
318 /// [`Normal`] feerate during normal operation, this value represents the additional fee we're
319 /// willing to pay in order to avoid waiting for our counterparty's to_self_delay to reclaim our
322 /// When we are not the funder, we require the closing transaction fee pay at least our
323 /// [`Background`] fee estimate, but allow our counterparty to pay as much fee as they like.
324 /// Thus, this value is ignored when we are not the funder.
326 /// Default value: 1000 satoshis.
328 /// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
329 /// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
330 pub force_close_avoidance_max_fee_satoshis: u64,
333 impl Default for ChannelConfig {
334 /// Provides sane defaults for most configurations (but with zero relay fees!).
335 fn default() -> Self {
337 forwarding_fee_proportional_millionths: 0,
338 forwarding_fee_base_msat: 1000,
339 cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
340 announced_channel: false,
341 commit_upfront_shutdown_pubkey: true,
342 max_dust_htlc_exposure_msat: 5_000_000,
343 force_close_avoidance_max_fee_satoshis: 1000,
348 impl_writeable_tlv_based!(ChannelConfig, {
349 (0, forwarding_fee_proportional_millionths, required),
350 (1, max_dust_htlc_exposure_msat, (default_value, 5_000_000)),
351 (2, cltv_expiry_delta, required),
352 (3, force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
353 (4, announced_channel, required),
354 (6, commit_upfront_shutdown_pubkey, required),
355 (8, forwarding_fee_base_msat, required),
358 /// Top-level config which holds ChannelHandshakeLimits and ChannelConfig.
360 /// Default::default() provides sane defaults for most configurations
361 /// (but currently with 0 relay fees!)
362 #[derive(Copy, Clone, Debug)]
363 pub struct UserConfig {
364 /// Channel config that we propose to our counterparty.
365 pub own_channel_config: ChannelHandshakeConfig,
366 /// Limits applied to our counterparty's proposed channel config settings.
367 pub peer_channel_config_limits: ChannelHandshakeLimits,
368 /// Channel config which affects behavior during channel lifetime.
369 pub channel_options: ChannelConfig,
370 /// If this is set to false, we will reject any HTLCs which were to be forwarded over private
371 /// channels. This prevents us from taking on HTLC-forwarding risk when we intend to run as a
372 /// node which is not online reliably.
374 /// For nodes which are not online reliably, you should set all channels to *not* be announced
375 /// (using [`ChannelConfig::announced_channel`] and
376 /// [`ChannelHandshakeLimits::force_announced_channel_preference`]) and set this to false to
377 /// ensure you are not exposed to any forwarding risk.
379 /// Note that because you cannot change a channel's announced state after creation, there is no
380 /// way to disable forwarding on public channels retroactively. Thus, in order to change a node
381 /// from a publicly-announced forwarding node to a private non-forwarding node you must close
382 /// all your channels and open new ones. For privacy, you should also change your node_id
383 /// (swapping all private and public key material for new ones) at that time.
385 /// Default value: false.
386 pub accept_forwards_to_priv_channels: bool,
387 /// If this is set to false, we do not accept inbound requests to open a new channel.
388 /// Default value: true.
389 pub accept_inbound_channels: bool,
390 /// If this is set to true, the user needs to manually accept inbound requests to open a new
393 /// When set to true, [`Event::OpenChannelRequest`] will be triggered once a request to open a
394 /// new inbound channel is received through a [`msgs::OpenChannel`] message. In that case, a
395 /// [`msgs::AcceptChannel`] message will not be sent back to the counterparty node unless the
396 /// user explicitly chooses to accept the request.
398 /// Default value: false.
400 /// [`Event::OpenChannelRequest`]: crate::util::events::Event::OpenChannelRequest
401 /// [`msgs::OpenChannel`]: crate::ln::msgs::OpenChannel
402 /// [`msgs::AcceptChannel`]: crate::ln::msgs::AcceptChannel
403 pub manually_accept_inbound_channels: bool,
406 impl Default for UserConfig {
407 fn default() -> Self {
409 own_channel_config: ChannelHandshakeConfig::default(),
410 peer_channel_config_limits: ChannelHandshakeLimits::default(),
411 channel_options: ChannelConfig::default(),
412 accept_forwards_to_priv_channels: false,
413 accept_inbound_channels: true,
414 manually_accept_inbound_channels: false,