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Drop max_inbound_htlc_value_in_flight_percent_of_channel #878

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Merged
tnull merged 1 commit into from
Apr 29, 2026
+41 −38
Merged

Drop max_inbound_htlc_value_in_flight_percent_of_channel #878

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28 changes: 14 additions & 14 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -40,18 +40,18 @@ default = []
#lightning-macros = { version = "0.2.0" }
#lightning-dns-resolver = { version = "0.3.0" }

lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std"] }
lightning-types = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std"] }
lightning-net-tokio = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
lightning-persister = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["tokio"] }
lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
lightning-block-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["rest-client", "rpc-client", "tokio"] }
lightning-transaction-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["esplora-async-https", "time", "electrum-rustls-ring"] }
lightning-liquidity = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std"] }
lightning-macros = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
lightning-dns-resolver = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133" }
lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std"] }
lightning-types = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
lightning-invoice = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std"] }
lightning-net-tokio = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
lightning-persister = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["tokio"] }
lightning-background-processor = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
lightning-rapid-gossip-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
lightning-block-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["rest-client", "rpc-client", "tokio"] }
lightning-transaction-sync = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["esplora-async-https", "time", "electrum-rustls-ring"] }
lightning-liquidity = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std"] }
lightning-macros = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }
lightning-dns-resolver = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144" }

bdk_chain = { version = "0.23.0", default-features = false, features = ["std"] }
bdk_esplora = { version = "0.22.0", default-features = false, features = ["async-https-rustls", "tokio"]}
Expand Down Expand Up @@ -81,13 +81,13 @@ async-trait = { version = "0.1", default-features = false }
vss-client = { package = "vss-client-ng", version = "0.5" }
prost = { version = "0.11.6", default-features = false}
#bitcoin-payment-instructions = { version = "0.6" }
bitcoin-payment-instructions = { git = "https://github.com/jkczyz/bitcoin-payment-instructions", rev = "340c535a600f7c43bef4c9f910edac4085f2e70c" }
bitcoin-payment-instructions = { git = "https://github.com/jkczyz/bitcoin-payment-instructions", rev = "679dac50cc0d81ec4d31da94b93d467e5308f16a" }

[target.'cfg(windows)'.dependencies]
winapi = { version = "0.3", features = ["winbase"] }

[dev-dependencies]
lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "044f3fab42e3085edecd40f0c9b369093edb7133", features = ["std", "_test_utils"] }
lightning = { git = "https://github.com/lightningdevkit/rust-lightning", rev = "369a2cf9c8ef810deea0cd2b4cf6ed0691b78144", features = ["std", "_test_utils"] }
rand = { version = "0.9.2", default-features = false, features = ["std", "thread_rng", "os_rng"] }
proptest = "1.0.0"
regex = "1.5.6"
Expand Down
5 changes: 0 additions & 5 deletions src/builder.rs
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Expand Up @@ -1657,11 +1657,6 @@ fn build_with_store_internal(

// If we act as an LSPS2 service, we allow forwarding to unannounced channels.
user_config.accept_forwards_to_priv_channels = true;

// If we act as an LSPS2 service, set the HTLC-value-in-flight to 100% of the channel value
// to ensure we can forward the initial payment.
user_config.channel_handshake_config.max_inbound_htlc_value_in_flight_percent_of_channel =
100;
Comment on lines -1670 to -1673
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@tankyleo tankyleo Apr 28, 2026

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To confirm here I don't think setting 100% here would have helped as that maximum only applies to the inbound HTLCs on that channel. To make sure that 100% of the value can be allocated to outbound HTLCs from the LSP's perspective as the comment describes, the user needs to set their max_inbound to 100%.

So seems to me the intention of the code did not match the comment ?

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@jkczyz jkczyz Apr 28, 2026

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Hmm... yeah it does seem that way.

}

if let Some(role) = async_payments_role {
Expand Down
24 changes: 13 additions & 11 deletions src/event.rs
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Expand Up @@ -26,9 +26,7 @@ use lightning::ln::channelmanager::{PaymentId, TrustedChannelFeatures};
use lightning::ln::types::ChannelId;
use lightning::routing::gossip::NodeId;
use lightning::sign::EntropySource;
use lightning::util::config::{
ChannelConfigOverrides, ChannelConfigUpdate, ChannelHandshakeConfigUpdate,
};
use lightning::util::config::{ChannelConfigOverrides, ChannelConfigUpdate};
use lightning::util::errors::APIError;
use lightning::util::persist::KVStore;
use lightning::util::ser::{Readable, ReadableArgs, Writeable, Writer};
Expand Down Expand Up @@ -1273,20 +1271,24 @@ where
if lsp_node_id == counterparty_node_id {
// When we're an LSPS2 client, allow claiming underpaying HTLCs as the LSP will skim off some fee. We'll
// check that they don't take too much before claiming.
//
// We also set maximum allowed inbound HTLC value in flight
// to 100%. We should eventually be able to set this on a per-channel basis, but for
// now we just bump the default for all channels.
channel_override_config = Some(ChannelConfigOverrides {
handshake_overrides: Some(ChannelHandshakeConfigUpdate {
max_inbound_htlc_value_in_flight_percent_of_channel: Some(100),
..Default::default()
}),
update_overrides: Some(ChannelConfigUpdate {
accept_underpaying_htlcs: Some(true),
..Default::default()
}),
..Default::default()
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@tankyleo tankyleo Apr 28, 2026

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nit: as elsewhere, maybe a quick debug_assert here on the 100% value ? Up to @tnull

});

// LSPS2 channels are unannounced; rely on LDK's default of 100%
// inbound HTLC value-in-flight so the LSP can forward the initial
// payment in full.
debug_assert_eq!(
self.channel_manager
.get_current_config()
.channel_handshake_config
.unannounced_channel_max_inbound_htlc_value_in_flight_percentage,
100
);
}
}
let res = if allow_0conf {
Expand Down
15 changes: 9 additions & 6 deletions src/lib.rs
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Expand Up @@ -1195,13 +1195,16 @@ impl Node {
let mut user_config = default_user_config(&self.config);
user_config.channel_handshake_config.announce_for_forwarding = announce_for_forwarding;
user_config.channel_config = (channel_config.unwrap_or_default()).clone().into();
// We set the max inflight to 100% for private channels.
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@tankyleo tankyleo Apr 28, 2026

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nit: similar here, would it be worth adding a debug_assert to guard against any changes away from this behavior ?

// FIXME: LDK will default to this behavior soon, too, at which point we should drop this
// manual override.

// Unannounced channels rely on LDK's default of 100% inbound HTLC value-in-flight
// to support large initial payments via LSPS2.
if !announce_for_forwarding {
user_config
.channel_handshake_config
.max_inbound_htlc_value_in_flight_percent_of_channel = 100;
debug_assert_eq!(
user_config
.channel_handshake_config
.unannounced_channel_max_inbound_htlc_value_in_flight_percentage,
100
);
}

let push_msat = push_to_counterparty_msat.unwrap_or(0);
Expand Down
7 changes: 5 additions & 2 deletions src/liquidity.rs
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Expand Up @@ -781,13 +781,16 @@ where

let mut config = self.channel_manager.get_current_config().clone();

// We set these LSP-specific values during Node building, here we're making sure it's actually set.
// If we act as an LSPS2 service, the HTLC-value-in-flight must be 100% of the
// channel value to ensure we can forward the initial payment. That cap only
// applies to unannounced channels, so the channel must also be unannounced.
debug_assert_eq!(
config
.channel_handshake_config
.max_inbound_htlc_value_in_flight_percent_of_channel,
.unannounced_channel_max_inbound_htlc_value_in_flight_percentage,
100
);
debug_assert!(!config.channel_handshake_config.announce_for_forwarding);
debug_assert!(config.accept_forwards_to_priv_channels);
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@tankyleo tankyleo Apr 28, 2026

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nit: can we add a debug_assert here on announce_for_forwarding = false ? IIUC right now we inherit announce_for_forwarding = false here because of the default in rust-lightning, but would be good to confirm this here I think.

This is to make sure that the 100% cap actually gets applied to the channel opened by the LSPS2 service.


// We set the forwarding fee to 0 for now as we're getting paid by the channel fee.
Expand Down
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