}
}
+/// Options for how to set the max dust HTLC exposure allowed on a channel. See
+/// [`ChannelConfig::max_dust_htlc_exposure`] for details.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum MaxDustHTLCExposure {
+ /// This sets a fixed limit on the total dust exposure in millisatoshis. Setting this too low
+ /// may prevent the sending or receipt of low-value HTLCs on high-traffic nodes, however this
+ /// limit is very important to prevent stealing of large amounts of dust HTLCs by miners
+ /// through [fee griefing
+ /// attacks](https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-May/002714.html).
+ ///
+ /// Note that if the feerate increases significantly, without a manual increase
+ /// to this maximum the channel may be unable to send/receive HTLCs between the maximum dust
+ /// exposure and the new minimum value for HTLCs to be economically viable to claim.
+ FixedLimitMsat(u64),
+ /// This sets a multiplier on the estimated high priority feerate (sats/KW, as obtained from
+ /// [`FeeEstimator`]) to determine the maximum allowed dust exposure. If this variant is used
+ /// then the maximum dust exposure in millisatoshis is calculated as:
+ /// `high_priority_feerate_per_kw * value`. For example, with our default value
+ /// `FeeRateMultiplier(5000)`:
+ ///
+ /// - For the minimum fee rate of 1 sat/vByte (250 sat/KW, although the minimum
+ /// defaults to 253 sats/KW for rounding, see [`FeeEstimator`]), the max dust exposure would
+ /// be 253 * 5000 = 1,265,000 msats.
+ /// - For a fee rate of 30 sat/vByte (7500 sat/KW), the max dust exposure would be
+ /// 7500 * 5000 = 37,500,000 msats.
+ ///
+ /// This allows the maximum dust exposure to automatically scale with fee rate changes.
+ ///
+ /// Note, if you're using a third-party fee estimator, this may leave you more exposed to a
+ /// fee griefing attack, where your fee estimator may purposely overestimate the fee rate,
+ /// causing you to accept more dust HTLCs than you would otherwise.
+ ///
+ /// This variant is primarily meant to serve pre-anchor channels, as HTLC fees being included
+ /// on HTLC outputs means your channel may be subject to more dust exposure in the event of
+ /// increases in fee rate.
+ ///
+ /// # Backwards Compatibility
+ /// This variant only became available in LDK 0.0.116, so if you downgrade to a prior version
+ /// by default this will be set to a [`Self::FixedLimitMsat`] of 5,000,000 msat.
+ ///
+ /// [`FeeEstimator`]: crate::chain::chaininterface::FeeEstimator
+ FeeRateMultiplier(u64),
+}
+
+impl_writeable_tlv_based_enum!(MaxDustHTLCExposure, ;
+ (1, FixedLimitMsat),
+ (3, FeeRateMultiplier),
+);
+
/// Options which apply on a per-channel basis and may change at runtime or based on negotiation
/// with our counterparty.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
/// channel negotiated throughout the channel open process, along with the fees required to have
/// a broadcastable HTLC spending transaction. When a channel supports anchor outputs
/// (specifically the zero fee HTLC transaction variant), this threshold no longer takes into
- /// account the HTLC transaction fee as it is zero.
+ /// account the HTLC transaction fee as it is zero. Because of this, you may want to set this
+ /// value to a fixed limit for channels using anchor outputs, while the fee rate multiplier
+ /// variant is primarily intended for use with pre-anchor channels.
///
- /// This limit is applied for sent, forwarded, and received HTLCs and limits the total
- /// exposure across all three types per-channel. Setting this too low may prevent the
- /// sending or receipt of low-value HTLCs on high-traffic nodes, and this limit is very
- /// important to prevent stealing of dust HTLCs by miners.
+ /// The selected limit is applied for sent, forwarded, and received HTLCs and limits the total
+ /// exposure across all three types per-channel.
///
- /// Default value: 5_000_000 msat.
- pub max_dust_htlc_exposure_msat: u64,
+ /// Default value: [`MaxDustHTLCExposure::FeeRateMultiplier`] with a multiplier of 5000.
+ pub max_dust_htlc_exposure: MaxDustHTLCExposure,
/// The additional fee we're willing to pay to avoid waiting for the counterparty's
/// `to_self_delay` to reclaim funds.
///
self.cltv_expiry_delta = cltv_expiry_delta;
}
if let Some(max_dust_htlc_exposure_msat) = update.max_dust_htlc_exposure_msat {
- self.max_dust_htlc_exposure_msat = max_dust_htlc_exposure_msat;
+ self.max_dust_htlc_exposure = max_dust_htlc_exposure_msat;
}
if let Some(force_close_avoidance_max_fee_satoshis) = update.force_close_avoidance_max_fee_satoshis {
self.force_close_avoidance_max_fee_satoshis = force_close_avoidance_max_fee_satoshis;
forwarding_fee_proportional_millionths: 0,
forwarding_fee_base_msat: 1000,
cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
- max_dust_htlc_exposure_msat: 5_000_000,
+ max_dust_htlc_exposure: MaxDustHTLCExposure::FeeRateMultiplier(5000),
force_close_avoidance_max_fee_satoshis: 1000,
accept_underpaying_htlcs: false,
}
}
}
-impl_writeable_tlv_based!(ChannelConfig, {
- (0, forwarding_fee_proportional_millionths, required),
- (1, accept_underpaying_htlcs, (default_value, false)),
- (2, forwarding_fee_base_msat, required),
- (4, cltv_expiry_delta, required),
- (6, max_dust_htlc_exposure_msat, required),
- // ChannelConfig serialized this field with a required type of 8 prior to the introduction of
- // LegacyChannelConfig. To make sure that serialization is not compatible with this one, we use
- // the next required type of 10, which if seen by the old serialization will always fail.
- (10, force_close_avoidance_max_fee_satoshis, required),
-});
+impl crate::util::ser::Writeable for ChannelConfig {
+ fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), crate::io::Error> {
+ let max_dust_htlc_exposure_msat_fixed_limit = match self.max_dust_htlc_exposure {
+ MaxDustHTLCExposure::FixedLimitMsat(limit) => limit,
+ MaxDustHTLCExposure::FeeRateMultiplier(_) => 5_000_000,
+ };
+ write_tlv_fields!(writer, {
+ (0, self.forwarding_fee_proportional_millionths, required),
+ (1, self.accept_underpaying_htlcs, (default_value, false)),
+ (2, self.forwarding_fee_base_msat, required),
+ (3, self.max_dust_htlc_exposure, required),
+ (4, self.cltv_expiry_delta, required),
+ (6, max_dust_htlc_exposure_msat_fixed_limit, required),
+ // ChannelConfig serialized this field with a required type of 8 prior to the introduction of
+ // LegacyChannelConfig. To make sure that serialization is not compatible with this one, we use
+ // the next required type of 10, which if seen by the old serialization will always fail.
+ (10, self.force_close_avoidance_max_fee_satoshis, required),
+ });
+ Ok(())
+ }
+}
+
+impl crate::util::ser::Readable for ChannelConfig {
+ fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
+ let mut forwarding_fee_proportional_millionths = 0;
+ let mut accept_underpaying_htlcs = false;
+ let mut forwarding_fee_base_msat = 1000;
+ let mut cltv_expiry_delta = 6 * 12;
+ let mut max_dust_htlc_exposure_msat = None;
+ let mut max_dust_htlc_exposure_enum = None;
+ let mut force_close_avoidance_max_fee_satoshis = 1000;
+ read_tlv_fields!(reader, {
+ (0, forwarding_fee_proportional_millionths, required),
+ (1, accept_underpaying_htlcs, (default_value, false)),
+ (2, forwarding_fee_base_msat, required),
+ (3, max_dust_htlc_exposure_enum, option),
+ (4, cltv_expiry_delta, required),
+ // Has always been written, but became optionally read in 0.0.116
+ (6, max_dust_htlc_exposure_msat, option),
+ (10, force_close_avoidance_max_fee_satoshis, required),
+ });
+ let max_dust_htlc_fixed_limit = max_dust_htlc_exposure_msat.unwrap_or(5_000_000);
+ let max_dust_htlc_exposure_msat = max_dust_htlc_exposure_enum
+ .unwrap_or(MaxDustHTLCExposure::FixedLimitMsat(max_dust_htlc_fixed_limit));
+ Ok(Self {
+ forwarding_fee_proportional_millionths,
+ accept_underpaying_htlcs,
+ forwarding_fee_base_msat,
+ cltv_expiry_delta,
+ max_dust_htlc_exposure: max_dust_htlc_exposure_msat,
+ force_close_avoidance_max_fee_satoshis,
+ })
+ }
+}
/// A parallel struct to [`ChannelConfig`] to define partial updates.
#[allow(missing_docs)]
pub forwarding_fee_proportional_millionths: Option<u32>,
pub forwarding_fee_base_msat: Option<u32>,
pub cltv_expiry_delta: Option<u16>,
- pub max_dust_htlc_exposure_msat: Option<u64>,
+ pub max_dust_htlc_exposure_msat: Option<MaxDustHTLCExposure>,
pub force_close_avoidance_max_fee_satoshis: Option<u64>,
}
forwarding_fee_proportional_millionths: Some(config.forwarding_fee_proportional_millionths),
forwarding_fee_base_msat: Some(config.forwarding_fee_base_msat),
cltv_expiry_delta: Some(config.cltv_expiry_delta),
- max_dust_htlc_exposure_msat: Some(config.max_dust_htlc_exposure_msat),
+ max_dust_htlc_exposure_msat: Some(config.max_dust_htlc_exposure),
force_close_avoidance_max_fee_satoshis: Some(config.force_close_avoidance_max_fee_satoshis),
}
}
impl crate::util::ser::Writeable for LegacyChannelConfig {
fn write<W: crate::util::ser::Writer>(&self, writer: &mut W) -> Result<(), crate::io::Error> {
+ let max_dust_htlc_exposure_msat_fixed_limit = match self.options.max_dust_htlc_exposure {
+ MaxDustHTLCExposure::FixedLimitMsat(limit) => limit,
+ MaxDustHTLCExposure::FeeRateMultiplier(_) => 5_000_000,
+ };
write_tlv_fields!(writer, {
(0, self.options.forwarding_fee_proportional_millionths, required),
- (1, self.options.max_dust_htlc_exposure_msat, (default_value, 5_000_000)),
+ (1, max_dust_htlc_exposure_msat_fixed_limit, required),
(2, self.options.cltv_expiry_delta, required),
(3, self.options.force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
(4, self.announced_channel, required),
+ (5, self.options.max_dust_htlc_exposure, required),
(6, self.commit_upfront_shutdown_pubkey, required),
(8, self.options.forwarding_fee_base_msat, required),
});
impl crate::util::ser::Readable for LegacyChannelConfig {
fn read<R: crate::io::Read>(reader: &mut R) -> Result<Self, crate::ln::msgs::DecodeError> {
let mut forwarding_fee_proportional_millionths = 0;
- let mut max_dust_htlc_exposure_msat = 5_000_000;
+ let mut max_dust_htlc_exposure_msat_fixed_limit = None;
let mut cltv_expiry_delta = 0;
let mut force_close_avoidance_max_fee_satoshis = 1000;
let mut announced_channel = false;
let mut commit_upfront_shutdown_pubkey = false;
let mut forwarding_fee_base_msat = 0;
+ let mut max_dust_htlc_exposure_enum = None;
read_tlv_fields!(reader, {
(0, forwarding_fee_proportional_millionths, required),
- (1, max_dust_htlc_exposure_msat, (default_value, 5_000_000u64)),
+ // Has always been written, but became optionally read in 0.0.116
+ (1, max_dust_htlc_exposure_msat_fixed_limit, option),
(2, cltv_expiry_delta, required),
(3, force_close_avoidance_max_fee_satoshis, (default_value, 1000u64)),
(4, announced_channel, required),
+ (5, max_dust_htlc_exposure_enum, option),
(6, commit_upfront_shutdown_pubkey, required),
(8, forwarding_fee_base_msat, required),
});
+ let max_dust_htlc_exposure_msat_fixed_limit =
+ max_dust_htlc_exposure_msat_fixed_limit.unwrap_or(5_000_000);
+ let max_dust_htlc_exposure_msat = max_dust_htlc_exposure_enum
+ .unwrap_or(MaxDustHTLCExposure::FixedLimitMsat(max_dust_htlc_exposure_msat_fixed_limit));
Ok(Self {
options: ChannelConfig {
forwarding_fee_proportional_millionths,
- max_dust_htlc_exposure_msat,
+ max_dust_htlc_exposure: max_dust_htlc_exposure_msat,
cltv_expiry_delta,
force_close_avoidance_max_fee_satoshis,
forwarding_fee_base_msat,
projects / rust-lightning / blobdiff