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 /// [`ChannelHandshakeConfig::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,
105 /// Set to announce the channel publicly and notify all nodes that they can route via this
108 /// This should only be set to true for nodes which expect to be online reliably.
110 /// As the node which funds a channel picks this value this will only apply for new outbound
111 /// channels unless [`ChannelHandshakeLimits::force_announced_channel_preference`] is set.
113 /// Default value: false.
114 pub announced_channel: bool,
115 /// When set, we commit to an upfront shutdown_pubkey at channel open. If our counterparty
116 /// supports it, they will then enforce the mutual-close output to us matches what we provided
117 /// at intialization, preventing us from closing to an alternate pubkey.
119 /// This is set to true by default to provide a slight increase in security, though ultimately
120 /// any attacker who is able to take control of a channel can just as easily send the funds via
121 /// lightning payments, so we never require that our counterparties support this option.
123 /// The upfront key committed is provided from [`KeysInterface::get_shutdown_scriptpubkey`].
125 /// Default value: true.
127 /// [`KeysInterface::get_shutdown_scriptpubkey`]: crate::chain::keysinterface::KeysInterface::get_shutdown_scriptpubkey
128 pub commit_upfront_shutdown_pubkey: bool,
131 impl Default for ChannelHandshakeConfig {
132 fn default() -> ChannelHandshakeConfig {
133 ChannelHandshakeConfig {
135 our_to_self_delay: BREAKDOWN_TIMEOUT,
136 our_htlc_minimum_msat: 1,
137 max_inbound_htlc_value_in_flight_percent_of_channel: 10,
138 negotiate_scid_privacy: false,
139 announced_channel: false,
140 commit_upfront_shutdown_pubkey: true,
145 /// Optional channel limits which are applied during channel creation.
147 /// These limits are only applied to our counterparty's limits, not our own.
149 /// Use 0/<type>::max_value() as appropriate to skip checking.
151 /// Provides sane defaults for most configurations.
153 /// Most additional limits are disabled except those with which specify a default in individual
154 /// field documentation. Note that this may result in barely-usable channels, but since they
155 /// are applied mostly only to incoming channels that's not much of a problem.
156 #[derive(Copy, Clone, Debug)]
157 pub struct ChannelHandshakeLimits {
158 /// Minimum allowed satoshis when a channel is funded. This is supplied by the sender and so
159 /// only applies to inbound channels.
161 /// Default value: 0.
162 pub min_funding_satoshis: u64,
163 /// Maximum allowed satoshis when a channel is funded. This is supplied by the sender and so
164 /// only applies to inbound channels.
166 /// Default value: 2^24 - 1.
167 pub max_funding_satoshis: u64,
168 /// The remote node sets a limit on the minimum size of HTLCs we can send to them. This allows
169 /// you to limit the maximum minimum-size they can require.
171 /// Default value: u64::max_value.
172 pub max_htlc_minimum_msat: u64,
173 /// The remote node sets a limit on the maximum value of pending HTLCs to them at any given
174 /// time to limit their funds exposure to HTLCs. This allows you to set a minimum such value.
176 /// Default value: 0.
177 pub min_max_htlc_value_in_flight_msat: u64,
178 /// The remote node will require we keep a certain amount in direct payment to ourselves at all
179 /// time, ensuring that we are able to be punished if we broadcast an old state. This allows to
180 /// you limit the amount which we will have to keep to ourselves (and cannot use for HTLCs).
182 /// Default value: u64::max_value.
183 pub max_channel_reserve_satoshis: u64,
184 /// The remote node sets a limit on the maximum number of pending HTLCs to them at any given
185 /// time. This allows you to set a minimum such value.
187 /// Default value: 0.
188 pub min_max_accepted_htlcs: u16,
189 /// Before a channel is usable the funding transaction will need to be confirmed by at least a
190 /// certain number of blocks, specified by the node which is not the funder (as the funder can
191 /// assume they aren't going to double-spend themselves).
192 /// This config allows you to set a limit on the maximum amount of time to wait.
194 /// Default value: 144, or roughly one day and only applies to outbound channels.
195 pub max_minimum_depth: u32,
196 /// Whether we implicitly trust funding transactions generated by us for our own outbound
197 /// channels to not be double-spent.
199 /// If this is set, we assume that our own funding transactions are *never* double-spent, and
200 /// thus we can trust them without any confirmations. This is generally a reasonable
201 /// assumption, given we're the only ones who could ever double-spend it (assuming we have sole
202 /// control of the signing keys).
204 /// You may wish to un-set this if you allow the user to (or do in an automated fashion)
205 /// double-spend the funding transaction to RBF with an alternative channel open.
207 /// This only applies if our counterparty set their confirmations-required value to 0, and we
208 /// always trust our own funding transaction at 1 confirmation irrespective of this value.
209 /// Thus, this effectively acts as a `min_minimum_depth`, with the only possible values being
210 /// `true` (0) and `false` (1).
212 /// Default value: true
213 pub trust_own_funding_0conf: bool,
214 /// Set to force an incoming channel to match our announced channel preference in
215 /// [`ChannelHandshakeConfig::announced_channel`].
217 /// For a node which is not online reliably, this should be set to true and
218 /// [`ChannelHandshakeConfig::announced_channel`] set to false, ensuring that no announced (aka public)
219 /// channels will ever be opened.
221 /// Default value: true.
222 pub force_announced_channel_preference: bool,
223 /// Set to the amount of time we're willing to wait to claim money back to us.
225 /// Not checking this value would be a security issue, as our peer would be able to set it to
226 /// max relative lock-time (a year) and we would "lose" money as it would be locked for a long time.
228 /// Default value: 2016, which we also enforce as a maximum value so you can tweak config to
229 /// reduce the loss of having useless locked funds (if your peer accepts)
230 pub their_to_self_delay: u16
233 impl Default for ChannelHandshakeLimits {
234 fn default() -> Self {
235 ChannelHandshakeLimits {
236 min_funding_satoshis: 0,
237 max_funding_satoshis: MAX_FUNDING_SATOSHIS_NO_WUMBO,
238 max_htlc_minimum_msat: <u64>::max_value(),
239 min_max_htlc_value_in_flight_msat: 0,
240 max_channel_reserve_satoshis: <u64>::max_value(),
241 min_max_accepted_htlcs: 0,
242 trust_own_funding_0conf: true,
243 max_minimum_depth: 144,
244 force_announced_channel_preference: true,
245 their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT,
250 /// Options which apply on a per-channel basis and may change at runtime or based on negotiation
251 /// with our counterparty.
252 #[derive(Copy, Clone, Debug, PartialEq)]
253 pub struct ChannelConfig {
254 /// Amount (in millionths of a satoshi) charged per satoshi for payments forwarded outbound
255 /// over the channel.
256 /// This may be allowed to change at runtime in a later update, however doing so must result in
257 /// update messages sent to notify all nodes of our updated relay fee.
259 /// Default value: 0.
260 pub forwarding_fee_proportional_millionths: u32,
261 /// Amount (in milli-satoshi) charged for payments forwarded outbound over the channel, in
262 /// excess of [`forwarding_fee_proportional_millionths`].
263 /// This may be allowed to change at runtime in a later update, however doing so must result in
264 /// update messages sent to notify all nodes of our updated relay fee.
266 /// The default value of a single satoshi roughly matches the market rate on many routing nodes
267 /// as of July 2021. Adjusting it upwards or downwards may change whether nodes route through
270 /// Default value: 1000.
272 /// [`forwarding_fee_proportional_millionths`]: ChannelConfig::forwarding_fee_proportional_millionths
273 pub forwarding_fee_base_msat: u32,
274 /// The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded over
275 /// the channel this config applies to.
277 /// This is analogous to [`ChannelHandshakeConfig::our_to_self_delay`] but applies to in-flight
278 /// HTLC balance when a channel appears on-chain whereas
279 /// [`ChannelHandshakeConfig::our_to_self_delay`] applies to the remaining
280 /// (non-HTLC-encumbered) balance.
282 /// Thus, for HTLC-encumbered balances to be enforced on-chain when a channel is force-closed,
283 /// we (or one of our watchtowers) MUST be online to check for broadcast of the current
284 /// commitment transaction at least once per this many blocks (minus some margin to allow us
285 /// enough time to broadcast and confirm a transaction, possibly with time in between to RBF
286 /// the spending transaction).
288 /// Default value: 72 (12 hours at an average of 6 blocks/hour).
289 /// Minimum value: [`MIN_CLTV_EXPIRY_DELTA`], any values less than this will be treated as
290 /// [`MIN_CLTV_EXPIRY_DELTA`] instead.
292 /// [`MIN_CLTV_EXPIRY_DELTA`]: crate::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA
293 pub cltv_expiry_delta: u16,
294 /// Limit our total exposure to in-flight HTLCs which are burned to fees as they are too
295 /// small to claim on-chain.
297 /// When an HTLC present in one of our channels is below a "dust" threshold, the HTLC will
298 /// not be claimable on-chain, instead being turned into additional miner fees if either
299 /// party force-closes the channel. Because the threshold is per-HTLC, our total exposure
300 /// to such payments may be sustantial if there are many dust HTLCs present when the
301 /// channel is force-closed.
303 /// This limit is applied for sent, forwarded, and received HTLCs and limits the total
304 /// exposure across all three types per-channel. Setting this too low may prevent the
305 /// sending or receipt of low-value HTLCs on high-traffic nodes, and this limit is very
306 /// important to prevent stealing of dust HTLCs by miners.
308 /// Default value: 5_000_000 msat.
309 pub max_dust_htlc_exposure_msat: u64,
310 /// The additional fee we're willing to pay to avoid waiting for the counterparty's
311 /// `to_self_delay` to reclaim funds.
313 /// When we close a channel cooperatively with our counterparty, we negotiate a fee for the
314 /// closing transaction which both sides find acceptable, ultimately paid by the channel
315 /// funder/initiator.
317 /// When we are the funder, because we have to pay the channel closing fee, we bound the
318 /// acceptable fee by our [`Background`] and [`Normal`] fees, with the upper bound increased by
319 /// this value. Because the on-chain fee we'd pay to force-close the channel is kept near our
320 /// [`Normal`] feerate during normal operation, this value represents the additional fee we're
321 /// willing to pay in order to avoid waiting for our counterparty's to_self_delay to reclaim our
324 /// When we are not the funder, we require the closing transaction fee pay at least our
325 /// [`Background`] fee estimate, but allow our counterparty to pay as much fee as they like.
326 /// Thus, this value is ignored when we are not the funder.
328 /// Default value: 1000 satoshis.
330 /// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
331 /// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
332 pub force_close_avoidance_max_fee_satoshis: u64,
335 impl Default for ChannelConfig {
336 /// Provides sane defaults for most configurations (but with zero relay fees!).
337 fn default() -> Self {
339 forwarding_fee_proportional_millionths: 0,
340 forwarding_fee_base_msat: 1000,
341 cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
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 (2, forwarding_fee_base_msat, required),
351 (4, cltv_expiry_delta, required),
352 (6, max_dust_htlc_exposure_msat, required),
353 // ChannelConfig serialized this field with a required type of 8 prior to the introduction of
354 // LegacyChannelConfig. To make sure that serialization is not compatible with this one, we use
355 // the next required type of 10, which if seen by the old serialization will always fail.
356 (10, force_close_avoidance_max_fee_satoshis, required),
359 /// Legacy version of [`ChannelConfig`] that stored the static
360 /// [`ChannelHandshakeConfig::announced_channel`] and
361 /// [`ChannelHandshakeConfig::commit_upfront_shutdown_pubkey`] fields.
362 #[derive(Copy, Clone, Debug)]
363 pub(crate) struct LegacyChannelConfig {
364 pub(crate) options: ChannelConfig,
365 /// Deprecated but may still be read from. See [`ChannelHandshakeConfig::announced_channel`] to
366 /// set this when opening/accepting a channel.
367 pub(crate) announced_channel: bool,
368 /// Deprecated but may still be read from. See
369 /// [`ChannelHandshakeConfig::commit_upfront_shutdown_pubkey`] to set this when
370 /// opening/accepting a channel.
371 pub(crate) commit_upfront_shutdown_pubkey: bool,
374 impl Default for LegacyChannelConfig {
375 fn default() -> Self {
377 options: ChannelConfig::default(),
378 announced_channel: false,
379 commit_upfront_shutdown_pubkey: true,
384 impl ::util::ser::Writeable for LegacyChannelConfig {
385 fn write<W: ::util::ser::Writer>(&self, writer: &mut W) -> Result<(), ::io::Error> {
386 write_tlv_fields!(writer, {
387 (0, self.options.forwarding_fee_proportional_millionths, required),
388 (1, self.options.max_dust_htlc_exposure_msat, (default_value, 5_000_000)),
389 (2, self.options.cltv_expiry_delta, required),
390 (3, self.options.force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
391 (4, self.announced_channel, required),
392 (6, self.commit_upfront_shutdown_pubkey, required),
393 (8, self.options.forwarding_fee_base_msat, required),
399 impl ::util::ser::Readable for LegacyChannelConfig {
400 fn read<R: ::io::Read>(reader: &mut R) -> Result<Self, ::ln::msgs::DecodeError> {
401 let mut forwarding_fee_proportional_millionths = 0;
402 let mut max_dust_htlc_exposure_msat = 5_000_000;
403 let mut cltv_expiry_delta = 0;
404 let mut force_close_avoidance_max_fee_satoshis = 1000;
405 let mut announced_channel = false;
406 let mut commit_upfront_shutdown_pubkey = false;
407 let mut forwarding_fee_base_msat = 0;
408 read_tlv_fields!(reader, {
409 (0, forwarding_fee_proportional_millionths, required),
410 (1, max_dust_htlc_exposure_msat, (default_value, 5_000_000u64)),
411 (2, cltv_expiry_delta, required),
412 (3, force_close_avoidance_max_fee_satoshis, (default_value, 1000u64)),
413 (4, announced_channel, required),
414 (6, commit_upfront_shutdown_pubkey, required),
415 (8, forwarding_fee_base_msat, required),
418 options: ChannelConfig {
419 forwarding_fee_proportional_millionths,
420 max_dust_htlc_exposure_msat,
422 force_close_avoidance_max_fee_satoshis,
423 forwarding_fee_base_msat,
426 commit_upfront_shutdown_pubkey,
431 /// Top-level config which holds ChannelHandshakeLimits and ChannelConfig.
433 /// Default::default() provides sane defaults for most configurations
434 /// (but currently with 0 relay fees!)
435 #[derive(Copy, Clone, Debug)]
436 pub struct UserConfig {
437 /// Channel handshake config that we propose to our counterparty.
438 pub channel_handshake_config: ChannelHandshakeConfig,
439 /// Limits applied to our counterparty's proposed channel handshake config settings.
440 pub channel_handshake_limits: ChannelHandshakeLimits,
441 /// Channel config which affects behavior during channel lifetime.
442 pub channel_config: ChannelConfig,
443 /// If this is set to false, we will reject any HTLCs which were to be forwarded over private
444 /// channels. This prevents us from taking on HTLC-forwarding risk when we intend to run as a
445 /// node which is not online reliably.
447 /// For nodes which are not online reliably, you should set all channels to *not* be announced
448 /// (using [`ChannelHandshakeConfig::announced_channel`] and
449 /// [`ChannelHandshakeLimits::force_announced_channel_preference`]) and set this to false to
450 /// ensure you are not exposed to any forwarding risk.
452 /// Note that because you cannot change a channel's announced state after creation, there is no
453 /// way to disable forwarding on public channels retroactively. Thus, in order to change a node
454 /// from a publicly-announced forwarding node to a private non-forwarding node you must close
455 /// all your channels and open new ones. For privacy, you should also change your node_id
456 /// (swapping all private and public key material for new ones) at that time.
458 /// Default value: false.
459 pub accept_forwards_to_priv_channels: bool,
460 /// If this is set to false, we do not accept inbound requests to open a new channel.
461 /// Default value: true.
462 pub accept_inbound_channels: bool,
463 /// If this is set to true, the user needs to manually accept inbound requests to open a new
466 /// When set to true, [`Event::OpenChannelRequest`] will be triggered once a request to open a
467 /// new inbound channel is received through a [`msgs::OpenChannel`] message. In that case, a
468 /// [`msgs::AcceptChannel`] message will not be sent back to the counterparty node unless the
469 /// user explicitly chooses to accept the request.
471 /// Default value: false.
473 /// [`Event::OpenChannelRequest`]: crate::util::events::Event::OpenChannelRequest
474 /// [`msgs::OpenChannel`]: crate::ln::msgs::OpenChannel
475 /// [`msgs::AcceptChannel`]: crate::ln::msgs::AcceptChannel
476 pub manually_accept_inbound_channels: bool,
479 impl Default for UserConfig {
480 fn default() -> Self {
482 channel_handshake_config: ChannelHandshakeConfig::default(),
483 channel_handshake_limits: ChannelHandshakeLimits::default(),
484 channel_config: ChannelConfig::default(),
485 accept_forwards_to_priv_channels: false,
486 accept_inbound_channels: true,
487 manually_accept_inbound_channels: false,