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::channelmanager::{BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
15 /// Configuration we set when applicable.
17 /// Default::default() provides sane defaults.
18 #[derive(Copy, Clone, Debug)]
19 pub struct ChannelHandshakeConfig {
20 /// Confirmations we will wait for before considering the channel locked in.
21 /// Applied only for inbound channels (see ChannelHandshakeLimits::max_minimum_depth for the
22 /// equivalent limit applied to outbound channels).
25 pub minimum_depth: u32,
26 /// Set to the number of blocks we require our counterparty to wait to claim their money (ie
27 /// the number of blocks we have to punish our counterparty if they broadcast a revoked
30 /// This is one of the main parameters of our security model. We (or one of our watchtowers) MUST
31 /// be online to check for revoked transactions on-chain at least once every our_to_self_delay
32 /// blocks (minus some margin to allow us enough time to broadcast and confirm a transaction,
33 /// possibly with time in between to RBF the spending transaction).
35 /// Meanwhile, asking for a too high delay, we bother peer to freeze funds for nothing in
36 /// case of an honest unilateral channel close, which implicitly decrease the economic value of
39 /// Default value: [`BREAKDOWN_TIMEOUT`], we enforce it as a minimum at channel opening so you
40 /// can tweak config to ask for more security, not less.
41 pub our_to_self_delay: u16,
42 /// Set to the smallest value HTLC we will accept to process.
44 /// This value is sent to our counterparty on channel-open and we close the channel any time
45 /// our counterparty misbehaves by sending us an HTLC with a value smaller than this.
47 /// Default value: 1. If the value is less than 1, it is ignored and set to 1, as is required
49 pub our_htlc_minimum_msat: u64,
50 /// When set, we commit to an upfront shutdown_pubkey at channel open. If our counterparty
51 /// supports it, they will then enforce the mutual-close output to us matches what we provided
52 /// at intialization, preventing us from closing to an alternate pubkey.
54 /// This is set to true by default to provide a slight increase in security, though ultimately
55 /// any attacker who is able to take control of a channel can just as easily send the funds via
56 /// lightning payments, so we never require that our counterparties support this option.
58 /// This cannot be changed after a channel has been initialized.
60 /// Default value: true.
61 pub commit_upfront_shutdown_pubkey: bool
64 impl Default for ChannelHandshakeConfig {
65 fn default() -> ChannelHandshakeConfig {
66 ChannelHandshakeConfig {
68 our_to_self_delay: BREAKDOWN_TIMEOUT,
69 our_htlc_minimum_msat: 1,
70 commit_upfront_shutdown_pubkey: true
75 /// Optional channel limits which are applied during channel creation.
77 /// These limits are only applied to our counterparty's limits, not our own.
79 /// Use 0/<type>::max_value() as appropriate to skip checking.
81 /// Provides sane defaults for most configurations.
83 /// Most additional limits are disabled except those with which specify a default in individual
84 /// field documentation. Note that this may result in barely-usable channels, but since they
85 /// are applied mostly only to incoming channels that's not much of a problem.
86 #[derive(Copy, Clone, Debug)]
87 pub struct ChannelHandshakeLimits {
88 /// Minimum allowed satoshis when a channel is funded, this is supplied by the sender and so
89 /// only applies to inbound channels.
92 pub min_funding_satoshis: u64,
93 /// The remote node sets a limit on the minimum size of HTLCs we can send to them. This allows
94 /// you to limit the maximum minimum-size they can require.
96 /// Default value: u64::max_value.
97 pub max_htlc_minimum_msat: u64,
98 /// The remote node sets a limit on the maximum value of pending HTLCs to them at any given
99 /// time to limit their funds exposure to HTLCs. This allows you to set a minimum such value.
101 /// Default value: 0.
102 pub min_max_htlc_value_in_flight_msat: u64,
103 /// The remote node will require we keep a certain amount in direct payment to ourselves at all
104 /// time, ensuring that we are able to be punished if we broadcast an old state. This allows to
105 /// you limit the amount which we will have to keep to ourselves (and cannot use for HTLCs).
107 /// Default value: u64::max_value.
108 pub max_channel_reserve_satoshis: u64,
109 /// The remote node sets a limit on the maximum number of pending HTLCs to them at any given
110 /// time. This allows you to set a minimum such value.
112 /// Default value: 0.
113 pub min_max_accepted_htlcs: u16,
114 /// Before a channel is usable the funding transaction will need to be confirmed by at least a
115 /// certain number of blocks, specified by the node which is not the funder (as the funder can
116 /// assume they aren't going to double-spend themselves).
117 /// This config allows you to set a limit on the maximum amount of time to wait.
119 /// Default value: 144, or roughly one day and only applies to outbound channels.
120 pub max_minimum_depth: u32,
121 /// Set to force an incoming channel to match our announced channel preference in
122 /// [`ChannelConfig::announced_channel`].
124 /// For a node which is not online reliably, this should be set to true and
125 /// [`ChannelConfig::announced_channel`] set to false, ensuring that no announced (aka public)
126 /// channels will ever be opened.
128 /// Default value: true.
129 pub force_announced_channel_preference: bool,
130 /// Set to the amount of time we're willing to wait to claim money back to us.
132 /// Not checking this value would be a security issue, as our peer would be able to set it to
133 /// max relative lock-time (a year) and we would "lose" money as it would be locked for a long time.
135 /// Default value: 2016, which we also enforce as a maximum value so you can tweak config to
136 /// reduce the loss of having useless locked funds (if your peer accepts)
137 pub their_to_self_delay: u16
140 impl Default for ChannelHandshakeLimits {
141 fn default() -> Self {
142 ChannelHandshakeLimits {
143 min_funding_satoshis: 0,
144 max_htlc_minimum_msat: <u64>::max_value(),
145 min_max_htlc_value_in_flight_msat: 0,
146 max_channel_reserve_satoshis: <u64>::max_value(),
147 min_max_accepted_htlcs: 0,
148 max_minimum_depth: 144,
149 force_announced_channel_preference: true,
150 their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT,
155 /// Options which apply on a per-channel basis and may change at runtime or based on negotiation
156 /// with our counterparty.
157 #[derive(Copy, Clone, Debug)]
158 pub struct ChannelConfig {
159 /// Amount (in millionths of a satoshi) charged per satoshi for payments forwarded outbound
160 /// over the channel.
161 /// This may be allowed to change at runtime in a later update, however doing so must result in
162 /// update messages sent to notify all nodes of our updated relay fee.
164 /// Default value: 0.
165 pub forwarding_fee_proportional_millionths: u32,
166 /// Amount (in milli-satoshi) charged for payments forwarded outbound over the channel, in
167 /// excess of [`forwarding_fee_proportional_millionths`].
168 /// This may be allowed to change at runtime in a later update, however doing so must result in
169 /// update messages sent to notify all nodes of our updated relay fee.
171 /// The default value of a single satoshi roughly matches the market rate on many routing nodes
172 /// as of July 2021. Adjusting it upwards or downwards may change whether nodes route through
175 /// Default value: 1000.
177 /// [`forwarding_fee_proportional_millionths`]: ChannelConfig::forwarding_fee_proportional_millionths
178 pub forwarding_fee_base_msat: u32,
179 /// The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded over
180 /// the channel this config applies to.
182 /// This is analogous to [`ChannelHandshakeConfig::our_to_self_delay`] but applies to in-flight
183 /// HTLC balance when a channel appears on-chain whereas
184 /// [`ChannelHandshakeConfig::our_to_self_delay`] applies to the remaining
185 /// (non-HTLC-encumbered) balance.
187 /// Thus, for HTLC-encumbered balances to be enforced on-chain when a channel is force-closed,
188 /// we (or one of our watchtowers) MUST be online to check for broadcast of the current
189 /// commitment transaction at least once per this many blocks (minus some margin to allow us
190 /// enough time to broadcast and confirm a transaction, possibly with time in between to RBF
191 /// the spending transaction).
193 /// Default value: 72 (12 hours at an average of 6 blocks/hour).
194 /// Minimum value: [`MIN_CLTV_EXPIRY_DELTA`], any values less than this will be treated as
195 /// [`MIN_CLTV_EXPIRY_DELTA`] instead.
197 /// [`MIN_CLTV_EXPIRY_DELTA`]: crate::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA
198 pub cltv_expiry_delta: u16,
199 /// Set to announce the channel publicly and notify all nodes that they can route via this
202 /// This should only be set to true for nodes which expect to be online reliably.
204 /// As the node which funds a channel picks this value this will only apply for new outbound
205 /// channels unless [`ChannelHandshakeLimits::force_announced_channel_preference`] is set.
207 /// This cannot be changed after the initial channel handshake.
209 /// Default value: false.
210 pub announced_channel: bool,
211 /// This value is moved to ChannelHandshakeConfig, optional here for old serialiization
212 pub commit_upfront_shutdown_pubkey: Option<bool>,
213 /// Limit our total exposure to in-flight HTLCs which are burned to fees as they are too
214 /// small to claim on-chain.
216 /// When an HTLC present in one of our channels is below a "dust" threshold, the HTLC will
217 /// not be claimable on-chain, instead being turned into additional miner fees if either
218 /// party force-closes the channel. Because the threshold is per-HTLC, our total exposure
219 /// to such payments may be sustantial if there are many dust HTLCs present when the
220 /// channel is force-closed.
222 /// This limit is applied for sent, forwarded, and received HTLCs and limits the total
223 /// exposure across all three types per-channel. Setting this too low may prevent the
224 /// sending or receipt of low-value HTLCs on high-traffic nodes, and this limit is very
225 /// important to prevent stealing of dust HTLCs by miners.
227 /// Default value: 5_000_000 msat.
228 pub max_dust_htlc_exposure_msat: u64,
229 /// The additional fee we're willing to pay to avoid waiting for the counterparty's
230 /// `to_self_delay` to reclaim funds.
232 /// When we close a channel cooperatively with our counterparty, we negotiate a fee for the
233 /// closing transaction which both sides find acceptable, ultimately paid by the channel
234 /// funder/initiator.
236 /// When we are the funder, because we have to pay the channel closing fee, we bound the
237 /// acceptable fee by our [`Background`] and [`Normal`] fees, with the upper bound increased by
238 /// this value. Because the on-chain fee we'd pay to force-close the channel is kept near our
239 /// [`Normal`] feerate during normal operation, this value represents the additional fee we're
240 /// willing to pay in order to avoid waiting for our counterparty's to_self_delay to reclaim our
243 /// When we are not the funder, we require the closing transaction fee pay at least our
244 /// [`Background`] fee estimate, but allow our counterparty to pay as much fee as they like.
245 /// Thus, this value is ignored when we are not the funder.
247 /// Default value: 1000 satoshis.
249 /// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
250 /// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
251 pub force_close_avoidance_max_fee_satoshis: u64,
254 impl Default for ChannelConfig {
255 /// Provides sane defaults for most configurations (but with zero relay fees!).
256 fn default() -> Self {
258 forwarding_fee_proportional_millionths: 0,
259 forwarding_fee_base_msat: 1000,
260 cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
261 announced_channel: false,
262 commit_upfront_shutdown_pubkey: Some(true),
263 max_dust_htlc_exposure_msat: 5_000_000,
264 force_close_avoidance_max_fee_satoshis: 1000,
269 impl_writeable_tlv_based!(ChannelConfig, {
270 (0, forwarding_fee_proportional_millionths, required),
271 (1, max_dust_htlc_exposure_msat, (default_value, 5_000_000)),
272 (2, cltv_expiry_delta, required),
273 (3, force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
274 (4, announced_channel, required),
275 (6, commit_upfront_shutdown_pubkey, option),
276 (8, forwarding_fee_base_msat, required),
279 /// Top-level config which holds ChannelHandshakeLimits and ChannelConfig.
281 /// Default::default() provides sane defaults for most configurations
282 /// (but currently with 0 relay fees!)
283 #[derive(Copy, Clone, Debug)]
284 pub struct UserConfig {
285 /// Channel config that we propose to our counterparty.
286 pub own_channel_config: ChannelHandshakeConfig,
287 /// Limits applied to our counterparty's proposed channel config settings.
288 pub peer_channel_config_limits: ChannelHandshakeLimits,
289 /// Channel config which affects behavior during channel lifetime.
290 pub channel_options: ChannelConfig,
291 /// If this is set to false, we will reject any HTLCs which were to be forwarded over private
292 /// channels. This prevents us from taking on HTLC-forwarding risk when we intend to run as a
293 /// node which is not online reliably.
295 /// For nodes which are not online reliably, you should set all channels to *not* be announced
296 /// (using [`ChannelConfig::announced_channel`] and
297 /// [`ChannelHandshakeLimits::force_announced_channel_preference`]) and set this to false to
298 /// ensure you are not exposed to any forwarding risk.
300 /// Note that because you cannot change a channel's announced state after creation, there is no
301 /// way to disable forwarding on public channels retroactively. Thus, in order to change a node
302 /// from a publicly-announced forwarding node to a private non-forwarding node you must close
303 /// all your channels and open new ones. For privacy, you should also change your node_id
304 /// (swapping all private and public key material for new ones) at that time.
306 /// Default value: false.
307 pub accept_forwards_to_priv_channels: bool,
308 /// If this is set to false, we do not accept inbound requests to open a new channel.
309 /// Default value: true.
310 pub accept_inbound_channels: bool,
313 impl Default for UserConfig {
314 fn default() -> Self {
316 own_channel_config: ChannelHandshakeConfig::default(),
317 peer_channel_config_limits: ChannelHandshakeLimits::default(),
318 channel_options: ChannelConfig::default(),
319 accept_forwards_to_priv_channels: false,
320 accept_inbound_channels: true,