From 63f0a31b597b32253c886d8e10115bd09f948e14 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Viktor=20Tigerstr=C3=B6m?=
 <11711198+ViktorTigerstrom@users.noreply.github.com>
Date: Tue, 19 Apr 2022 23:34:53 +0200
Subject: [PATCH] Add outbound min/max to `ChannelCounterparty`

---
 fuzz/src/router.rs                 |  2 ++
 lightning/src/ln/channel.rs        |  5 +++++
 lightning/src/ln/channelmanager.rs | 16 ++++++++++++++++
 lightning/src/routing/router.rs    |  4 ++++
 4 files changed, 27 insertions(+)

diff --git a/fuzz/src/router.rs b/fuzz/src/router.rs
index 4db6587b4..b0f052dbc 100644
--- a/fuzz/src/router.rs
+++ b/fuzz/src/router.rs
@@ -213,6 +213,8 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
 									features: InitFeatures::known(),
 									unspendable_punishment_reserve: 0,
 									forwarding_info: None,
+									outbound_htlc_minimum_msat: None,
+									outbound_htlc_maximum_msat: None,
 								},
 								funding_txo: Some(OutPoint { txid: bitcoin::Txid::from_slice(&[0; 32]).unwrap(), index: 0 }),
 								channel_type: None,
diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 12fd69583..b0551bf83 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -4347,6 +4347,11 @@ impl<Signer: Sign> Channel<Signer> {
 		self.counterparty_htlc_minimum_msat
 	}
 
+	/// Allowed in any state (including after shutdown), but will return none before TheirInitSent
+	pub fn get_counterparty_htlc_maximum_msat(&self) -> Option<u64> {
+		self.get_htlc_maximum_msat(self.counterparty_max_htlc_value_in_flight_msat)
+	}
+
 	fn get_htlc_maximum_msat(&self, party_max_htlc_value_in_flight_msat: u64) -> Option<u64> {
 		self.counterparty_selected_channel_reserve_satoshis.map(|counterparty_reserve| {
 			let holder_reserve = self.holder_selected_channel_reserve_satoshis;
diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index abb20845c..020fc22cd 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -922,6 +922,12 @@ pub struct ChannelCounterparty {
 	/// Information on the fees and requirements that the counterparty requires when forwarding
 	/// payments to us through this channel.
 	pub forwarding_info: Option<CounterpartyForwardingInfo>,
+	/// The smallest value HTLC (in msat) the remote peer will accept, for this channel. This field
+	/// is only `None` before we have received either the `OpenChannel` or `AcceptChannel` message
+	/// from the remote peer, or for `ChannelCounterparty` objects serialized prior to LDK 0.0.107.
+	pub outbound_htlc_minimum_msat: Option<u64>,
+	/// The largest value HTLC (in msat) the remote peer currently will accept, for this channel.
+	pub outbound_htlc_maximum_msat: Option<u64>,
 }
 
 /// Details of a channel, as returned by ChannelManager::list_channels and ChannelManager::list_usable_channels
@@ -1675,6 +1681,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 						features: InitFeatures::empty(),
 						unspendable_punishment_reserve: to_remote_reserve_satoshis,
 						forwarding_info: channel.counterparty_forwarding_info(),
+						// Ensures that we have actually received the `htlc_minimum_msat` value
+						// from the counterparty through the `OpenChannel` or `AcceptChannel`
+						// message (as they are always the first message from the counterparty).
+						// Else `Channel::get_counterparty_htlc_minimum_msat` could return the
+						// default `0` value set by `Channel::new_outbound`.
+						outbound_htlc_minimum_msat: if channel.have_received_message() {
+							Some(channel.get_counterparty_htlc_minimum_msat()) } else { None },
+						outbound_htlc_maximum_msat: channel.get_counterparty_htlc_maximum_msat(),
 					},
 					funding_txo: channel.get_funding_txo(),
 					// Note that accept_channel (or open_channel) is always the first message, so
@@ -5904,6 +5918,8 @@ impl_writeable_tlv_based!(ChannelCounterparty, {
 	(4, features, required),
 	(6, unspendable_punishment_reserve, required),
 	(8, forwarding_info, option),
+	(9, outbound_htlc_minimum_msat, option),
+	(11, outbound_htlc_maximum_msat, option),
 });
 
 impl_writeable_tlv_based!(ChannelDetails, {
diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 5afe052bb..212ac2f10 100644
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -1735,6 +1735,8 @@ mod tests {
 				node_id,
 				unspendable_punishment_reserve: 0,
 				forwarding_info: None,
+				outbound_htlc_minimum_msat: None,
+				outbound_htlc_maximum_msat: None,
 			},
 			funding_txo: Some(OutPoint { txid: bitcoin::Txid::from_slice(&[0; 32]).unwrap(), index: 0 }),
 			channel_type: None,
@@ -5458,6 +5460,8 @@ mod benches {
 				node_id,
 				unspendable_punishment_reserve: 0,
 				forwarding_info: None,
+				outbound_htlc_minimum_msat: None,
+				outbound_htlc_maximum_msat: None,
 			},
 			funding_txo: Some(OutPoint {
 				txid: bitcoin::Txid::from_slice(&[0; 32]).unwrap(), index: 0
-- 
2.39.5