Clean up existing and add range-based closing_signed negotiation

[rust-lightning] / lightning / src / util / config.rs

diff --git a/lightning/src/util/config.rs b/lightning/src/util/config.rs
index 2e9e8e036b5032d58a40d1748e92d1f70eb200cf..fb4f6fce737fb1eb47c8cb95abcc8ae69d5ef3b4 100644 (file)
--- a/lightning/src/util/config.rs
+++ b/lightning/src/util/config.rs
@@ -206,7 +206,46 @@ pub struct ChannelConfig {
        /// This cannot be changed after a channel has been initialized.
        ///
        /// Default value: true.
-       pub commit_upfront_shutdown_pubkey: bool
+       pub commit_upfront_shutdown_pubkey: bool,
+       /// Limit our total exposure to in-flight HTLCs which are burned to fees as they are too
+       /// small to claim on-chain.
+       ///
+       /// When an HTLC present in one of our channels is below a "dust" threshold, the HTLC will
+       /// not be claimable on-chain, instead being turned into additional miner fees if either
+       /// party force-closes the channel. Because the threshold is per-HTLC, our total exposure
+       /// to such payments may be sustantial if there are many dust HTLCs present when the
+       /// channel is force-closed.
+       ///
+       /// 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.
+       ///
+       /// Default value: 5_000_000 msat.
+       pub max_dust_htlc_exposure_msat: u64,
+       /// The additional fee we're willing to pay to avoid waiting for the counterparty's
+       /// `to_self_delay` to reclaim funds.
+       ///
+       /// When we close a channel cooperatively with our counterparty, we negotiate a fee for the
+       /// closing transaction which both sides find acceptable, ultimately paid by the channel
+       /// funder/initiator.
+       ///
+       /// When we are the funder, because we have to pay the channel closing fee, we bound the
+       /// acceptable fee by our [`Background`] and [`Normal`] fees, with the upper bound increased by
+       /// this value. Because the on-chain fee we'd pay to force-close the channel is kept near our
+       /// [`Normal`] feerate during normal operation, this value represents the additional fee we're
+       /// willing to pay in order to avoid waiting for our counterparty's to_self_delay to reclaim our
+       /// funds.
+       ///
+       /// When we are not the funder, we require the closing transaction fee pay at least our
+       /// [`Background`] fee estimate, but allow our counterparty to pay as much fee as they like.
+       /// Thus, this value is ignored when we are not the funder.
+       ///
+       /// Default value: 1000 satoshis.
+       ///
+       /// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
+       /// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
+       pub force_close_avoidance_max_fee_satoshis: u64,
 }
 
 impl Default for ChannelConfig {
@@ -218,13 +257,17 @@ impl Default for ChannelConfig {
                        cltv_expiry_delta: 6 * 12, // 6 blocks/hour * 12 hours
                        announced_channel: false,
                        commit_upfront_shutdown_pubkey: true,
+                       max_dust_htlc_exposure_msat: 5_000_000,
+                       force_close_avoidance_max_fee_satoshis: 1000,
                }
        }
 }
 
 impl_writeable_tlv_based!(ChannelConfig, {
        (0, forwarding_fee_proportional_millionths, required),
+       (1, max_dust_htlc_exposure_msat, (default_value, 5_000_000)),
        (2, cltv_expiry_delta, required),
+       (3, force_close_avoidance_max_fee_satoshis, (default_value, 1000)),
        (4, announced_channel, required),
        (6, commit_upfront_shutdown_pubkey, required),
        (8, forwarding_fee_base_msat, required),