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,
52 impl Default for ChannelHandshakeConfig {
53 fn default() -> ChannelHandshakeConfig {
54 ChannelHandshakeConfig {
56 our_to_self_delay: BREAKDOWN_TIMEOUT,
57 our_htlc_minimum_msat: 1,
62 /// Optional channel limits which are applied during channel creation.
64 /// These limits are only applied to our counterparty's limits, not our own.
66 /// Use 0/<type>::max_value() as appropriate to skip checking.
68 /// Provides sane defaults for most configurations.
70 /// Most additional limits are disabled except those with which specify a default in individual
71 /// field documentation. Note that this may result in barely-usable channels, but since they
72 /// are applied mostly only to incoming channels that's not much of a problem.
73 #[derive(Copy, Clone, Debug)]
74 pub struct ChannelHandshakeLimits {
75 /// Minimum allowed satoshis when a channel is funded, this is supplied by the sender and so
76 /// only applies to inbound channels.
79 pub min_funding_satoshis: u64,
80 /// The remote node sets a limit on the minimum size of HTLCs we can send to them. This allows
81 /// you to limit the maximum minimum-size they can require.
83 /// Default value: u64::max_value.
84 pub max_htlc_minimum_msat: u64,
85 /// The remote node sets a limit on the maximum value of pending HTLCs to them at any given
86 /// time to limit their funds exposure to HTLCs. This allows you to set a minimum such value.
89 pub min_max_htlc_value_in_flight_msat: u64,
90 /// The remote node will require we keep a certain amount in direct payment to ourselves at all
91 /// time, ensuring that we are able to be punished if we broadcast an old state. This allows to
92 /// you limit the amount which we will have to keep to ourselves (and cannot use for HTLCs).
94 /// Default value: u64::max_value.
95 pub max_channel_reserve_satoshis: u64,
96 /// The remote node sets a limit on the maximum number of pending HTLCs to them at any given
97 /// time. This allows you to set a minimum such value.
100 pub min_max_accepted_htlcs: u16,
101 /// Before a channel is usable the funding transaction will need to be confirmed by at least a
102 /// certain number of blocks, specified by the node which is not the funder (as the funder can
103 /// assume they aren't going to double-spend themselves).
104 /// This config allows you to set a limit on the maximum amount of time to wait.
106 /// Default value: 144, or roughly one day and only applies to outbound channels.
107 pub max_minimum_depth: u32,
108 /// Set to force an incoming channel to match our announced channel preference in
109 /// [`ChannelConfig::announced_channel`].
111 /// For a node which is not online reliably, this should be set to true and
112 /// [`ChannelConfig::announced_channel`] set to false, ensuring that no announced (aka public)
113 /// channels will ever be opened.
115 /// Default value: true.
116 pub force_announced_channel_preference: bool,
117 /// Set to the amount of time we're willing to wait to claim money back to us.
119 /// Not checking this value would be a security issue, as our peer would be able to set it to
120 /// max relative lock-time (a year) and we would "lose" money as it would be locked for a long time.
122 /// Default value: 2016, which we also enforce as a maximum value so you can tweak config to
123 /// reduce the loss of having useless locked funds (if your peer accepts)
124 pub their_to_self_delay: u16
127 impl Default for ChannelHandshakeLimits {
128 fn default() -> Self {
129 ChannelHandshakeLimits {
130 min_funding_satoshis: 0,
131 max_htlc_minimum_msat: <u64>::max_value(),
132 min_max_htlc_value_in_flight_msat: 0,
133 max_channel_reserve_satoshis: <u64>::max_value(),
134 min_max_accepted_htlcs: 0,
135 max_minimum_depth: 144,
136 force_announced_channel_preference: true,
137 their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT,
142 /// Options which apply on a per-channel basis and may change at runtime or based on negotiation
143 /// with our counterparty.
144 #[derive(Copy, Clone, Debug)]
145 pub struct ChannelConfig {
146 /// Amount (in millionths of a satoshi) charged per satoshi for payments forwarded outbound
147 /// over the channel.
148 /// This may be allowed to change at runtime in a later update, however doing so must result in
149 /// update messages sent to notify all nodes of our updated relay fee.
151 /// Default value: 0.
152 pub forwarding_fee_proportional_millionths: u32,
153 /// Amount (in milli-satoshi) charged for payments forwarded outbound over the channel, in
154 /// excess of [`forwarding_fee_proportional_millionths`].
155 /// This may be allowed to change at runtime in a later update, however doing so must result in
156 /// update messages sent to notify all nodes of our updated relay fee.
158 /// The default value of a single satoshi roughly matches the market rate on many routing nodes
159 /// as of July 2021. Adjusting it upwards or downwards may change whether nodes route through
162 /// Default value: 1000.
164 /// [`forwarding_fee_proportional_millionths`]: ChannelConfig::forwarding_fee_proportional_millionths
165 pub forwarding_fee_base_msat: u32,
166 /// The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded over
167 /// the channel this config applies to.
169 /// This is analogous to [`ChannelHandshakeConfig::our_to_self_delay`] but applies to in-flight
170 /// HTLC balance when a channel appears on-chain whereas
171 /// [`ChannelHandshakeConfig::our_to_self_delay`] applies to the remaining
172 /// (non-HTLC-encumbered) balance.
174 /// Thus, for HTLC-encumbered balances to be enforced on-chain when a channel is force-closed,
175 /// we (or one of our watchtowers) MUST be online to check for broadcast of the current
176 /// commitment transaction at least once per this many blocks (minus some margin to allow us
177 /// enough time to broadcast and confirm a transaction, possibly with time in between to RBF
178 /// the spending transaction).
180 /// Default value: 72 (12 hours at an average of 6 blocks/hour).
181 /// Minimum value: [`MIN_CLTV_EXPIRY_DELTA`], any values less than this will be treated as
182 /// [`MIN_CLTV_EXPIRY_DELTA`] instead.
184 /// [`MIN_CLTV_EXPIRY_DELTA`]: crate::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA
185 pub cltv_expiry_delta: u16,
186 /// Set to announce the channel publicly and notify all nodes that they can route via this
189 /// This should only be set to true for nodes which expect to be online reliably.
191 /// As the node which funds a channel picks this value this will only apply for new outbound
192 /// channels unless [`ChannelHandshakeLimits::force_announced_channel_preference`] is set.
194 /// This cannot be changed after the initial channel handshake.
196 /// Default value: false.
197 pub announced_channel: bool,
198 /// When set, we commit to an upfront shutdown_pubkey at channel open. If our counterparty
199 /// supports it, they will then enforce the mutual-close output to us matches what we provided
200 /// at intialization, preventing us from closing to an alternate pubkey.
202 /// This is set to true by default to provide a slight increase in security, though ultimately
203 /// any attacker who is able to take control of a channel can just as easily send the funds via
204 /// lightning payments, so we never require that our counterparties support this option.
206 /// This cannot be changed after a channel has been initialized.
208 /// Default value: true.
209 pub commit_upfront_shutdown_pubkey: bool
212 impl Default for ChannelConfig {
213 /// Provides sane defaults for most configurations (but with zero relay fees!).
214 fn default() -> Self {
216 forwarding_fee_proportional_millionths: 0,
217 forwarding_fee_base_msat: 1000,
218 cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
219 announced_channel: false,
220 commit_upfront_shutdown_pubkey: true,
225 impl_writeable_tlv_based!(ChannelConfig, {
226 (0, forwarding_fee_proportional_millionths, required),
227 (2, cltv_expiry_delta, required),
228 (4, announced_channel, required),
229 (6, commit_upfront_shutdown_pubkey, required),
230 (8, forwarding_fee_base_msat, required),
233 /// Top-level config which holds ChannelHandshakeLimits and ChannelConfig.
235 /// Default::default() provides sane defaults for most configurations
236 /// (but currently with 0 relay fees!)
237 #[derive(Copy, Clone, Debug)]
238 pub struct UserConfig {
239 /// Channel config that we propose to our counterparty.
240 pub own_channel_config: ChannelHandshakeConfig,
241 /// Limits applied to our counterparty's proposed channel config settings.
242 pub peer_channel_config_limits: ChannelHandshakeLimits,
243 /// Channel config which affects behavior during channel lifetime.
244 pub channel_options: ChannelConfig,
245 /// If this is set to false, we will reject any HTLCs which were to be forwarded over private
246 /// channels. This prevents us from taking on HTLC-forwarding risk when we intend to run as a
247 /// node which is not online reliably.
249 /// For nodes which are not online reliably, you should set all channels to *not* be announced
250 /// (using [`ChannelConfig::announced_channel`] and
251 /// [`ChannelHandshakeLimits::force_announced_channel_preference`]) and set this to false to
252 /// ensure you are not exposed to any forwarding risk.
254 /// Note that because you cannot change a channel's announced state after creation, there is no
255 /// way to disable forwarding on public channels retroactively. Thus, in order to change a node
256 /// from a publicly-announced forwarding node to a private non-forwarding node you must close
257 /// all your channels and open new ones. For privacy, you should also change your node_id
258 /// (swapping all private and public key material for new ones) at that time.
260 /// Default value: false.
261 pub accept_forwards_to_priv_channels: bool,
264 impl Default for UserConfig {
265 fn default() -> Self {
267 own_channel_config: ChannelHandshakeConfig::default(),
268 peer_channel_config_limits: ChannelHandshakeLimits::default(),
269 channel_options: ChannelConfig::default(),
270 accept_forwards_to_priv_channels: false,