Add new config setting `max_balance_dust_htlc_msat`

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

diff --git a/lightning/src/util/config.rs b/lightning/src/util/config.rs
index 2e9e8e036b5032d58a40d1748e92d1f70eb200cf..3348b7b254e6f001290904add735105da0f429fe 100644 (file)
--- a/lightning/src/util/config.rs
+++ b/lightning/src/util/config.rs
@@ -206,7 +206,23 @@ 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,
 }
 
 impl Default for ChannelConfig {
@@ -218,12 +234,14 @@ 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,
                }
        }
 }
 
 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),
        (4, announced_channel, required),
        (6, commit_upfront_shutdown_pubkey, required),