Make htlc_minimum_msat configurable

Enforce a minimum htlc_minimum_msat of 1.

Instead of computing dynamically htlc_minimum_msat based on feerate,
relies on user-provided configuration value. This let user compute
an economical-driven channel parameter according to network dynamics.

Author: Antoine Riard

lightning/src/ln/channel.rs

@@ -433,10 +433,6 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		cmp::max(at_open_background_feerate * B_OUTPUT_PLUS_SPENDING_INPUT_WEIGHT / 1000, 546) //TODO
 	}
 
-	fn derive_our_htlc_minimum_msat(_at_open_channel_feerate_per_kw: u64) -> u64 {
-		1000 // TODO
-	}
-
 	// Constructors:
 	pub fn new_outbound<K: Deref, F: Deref>(fee_estimator: &F, keys_provider: &K, their_node_id: PublicKey, channel_value_satoshis: u64, push_msat: u64, user_id: u64, logger: Arc<Logger>, config: &UserConfig) -> Result<Channel<ChanSigner>, APIError>
 	where K::Target: KeysInterface<ChanKeySigner = ChanSigner>,
@@ -519,7 +515,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			their_max_htlc_value_in_flight_msat: 0,
 			their_channel_reserve_satoshis: 0,
 			their_htlc_minimum_msat: 0,
-			our_htlc_minimum_msat: Channel::<ChanSigner>::derive_our_htlc_minimum_msat(feerate),
+			our_htlc_minimum_msat: if config.own_channel_config.our_htlc_minimum_msat == 0 { 1 } else { config.own_channel_config.our_htlc_minimum_msat },
 			their_to_self_delay: 0,
 			our_to_self_delay: config.own_channel_config.our_to_self_delay,
 			their_max_accepted_htlcs: 0,
@@ -744,7 +740,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			their_max_htlc_value_in_flight_msat: cmp::min(msg.max_htlc_value_in_flight_msat, msg.funding_satoshis * 1000),
 			their_channel_reserve_satoshis: msg.channel_reserve_satoshis,
 			their_htlc_minimum_msat: msg.htlc_minimum_msat,
-			our_htlc_minimum_msat: Channel::<ChanSigner>::derive_our_htlc_minimum_msat(msg.feerate_per_kw as u64),
+			our_htlc_minimum_msat: if config.own_channel_config.our_htlc_minimum_msat == 0 { 1 } else { config.own_channel_config.our_htlc_minimum_msat },
 			their_to_self_delay: msg.to_self_delay,
 			our_to_self_delay: config.own_channel_config.our_to_self_delay,
 			their_max_accepted_htlcs: msg.max_accepted_htlcs,

lightning/src/ln/functional_test_utils.rs

@@ -1005,6 +1005,7 @@ pub fn create_node_chanmgrs<'a, 'b>(node_count: usize, cfgs: &'a Vec<NodeCfg<'b>
 		let mut default_config = UserConfig::default();
 		default_config.channel_options.announced_channel = true;
 		default_config.peer_channel_config_limits.force_announced_channel_preference = false;
+		default_config.own_channel_config.our_htlc_minimum_msat = 1000; // sanitization being done by the sender, to exerce receiver logic we need to lift of limit
 		let node = ChannelManager::new(Network::Testnet, cfgs[i].fee_estimator, &cfgs[i].chan_monitor, cfgs[i].tx_broadcaster, cfgs[i].logger.clone(), &cfgs[i].keys_manager, if node_config[i].is_some() { node_config[i].clone().unwrap() } else { default_config }, 0).unwrap();
 		chanmgrs.push(node);
 	}

lightning/src/util/config.rs

@@ -51,13 +51,22 @@ pub struct ChannelHandshakeConfig {
 	/// Default value: BREAKDOWN_TIMEOUT (currently 144), we enforce it as a minimum at channel
 	/// opening so you can tweak config to ask for more security, not less.
 	pub our_to_self_delay: u16,
+	/// Set to the smallest value HTLC we will accept to process.
+	///
+	/// This value is sent to our counterparty on channel-open and we close the channel any time
+	/// our counterparty misbehaves by sending us an HTLC with a value smaller than this.
+	///
+	/// Default value: 1. If the value is less than 1, it is ignored and set to 1, as is required
+	/// by the protocol.
+	pub our_htlc_minimum_msat: u64,
 }
 
 impl Default for ChannelHandshakeConfig {
 	fn default() -> ChannelHandshakeConfig {
 		ChannelHandshakeConfig {
 			minimum_depth: 6,
 			our_to_self_delay: BREAKDOWN_TIMEOUT,
+			our_htlc_minimum_msat: 1,
 		}
 	}
 }