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Add config knob for accepting underpaying HTLCs

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See ChannelConfig::accept_underpaying_htlcs
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Valentine Wallace 2023-05-16 14:18:47 -04:00
parent 672d666ef4
commit 85a5b31bb8
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1 changed files with 31 additions and 0 deletions
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31
lightning/src/util/config.rs
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@ -397,6 +397,34 @@ pub struct ChannelConfig {
/// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
/// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
pub force_close_avoidance_max_fee_satoshis: u64,
/// If set, allows this channel's counterparty to skim an additional fee off this node's inbound
/// HTLCs. Useful for liquidity providers to offload on-chain channel costs to end users.
///
/// Usage:
/// - The payee will set this option and set its invoice route hints to use [intercept scids]
/// generated by this channel's counterparty.
/// - The counterparty will get an [`HTLCIntercepted`] event upon payment forward, and call
/// [`forward_intercepted_htlc`] with less than the amount provided in
/// [`HTLCIntercepted::expected_outbound_amount_msat`]. The difference between the expected and
/// actual forward amounts is their fee.
// TODO: link to LSP JIT channel invoice generation spec when it's merged
///
/// # Note
/// It's important for payee wallet software to verify that [`PaymentClaimable::amount_msat`] is
/// as-expected if this feature is activated, otherwise they may lose money!
///
/// # Note
/// Switching this config flag on may break compatibility with versions of LDK prior to 0.0.116.
///
/// Default value: false.
///
/// [intercept scids]: crate::ln::channelmanager::ChannelManager::get_intercept_scid
/// [`forward_intercepted_htlc`]: crate::ln::channelmanager::ChannelManager::forward_intercepted_htlc
/// [`HTLCIntercepted`]: crate::events::Event::HTLCIntercepted
/// [`HTLCIntercepted::expected_outbound_amount_msat`]: crate::events::Event::HTLCIntercepted::expected_outbound_amount_msat
/// [`PaymentClaimable::amount_msat`]: crate::events::Event::PaymentClaimable::amount_msat
// TODO: link to bLIP when it's merged
pub accept_underpaying_htlcs: bool,
}
impl ChannelConfig {
@ -429,12 +457,14 @@ impl Default for ChannelConfig {
cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
max_dust_htlc_exposure_msat: 5_000_000,
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),
@ -543,6 +573,7 @@ impl crate::util::ser::Readable for LegacyChannelConfig {
cltv_expiry_delta,
force_close_avoidance_max_fee_satoshis,
forwarding_fee_base_msat,
accept_underpaying_htlcs: false,
},
announced_channel,
commit_upfront_shutdown_pubkey,