Clarify policy applied in send htlc error msgs

max_htlc_value_in_flight_msat is applied
per-direction

Author: Antoine Riard

src/ln/channel.rs

@@ -1590,10 +1590,9 @@ impl Channel {
 		if inbound_htlc_count + 1 > OUR_MAX_HTLCS as u32 {
 			return Err(ChannelError::Close("Remote tried to push more than our max accepted HTLCs"));
 		}
-		//TODO: Spec is unclear if this is per-direction or in total (I assume per direction):
 		// Check our_max_htlc_value_in_flight_msat
 		if htlc_inbound_value_msat + msg.amount_msat > Channel::get_our_max_htlc_value_in_flight_msat(self.channel_value_satoshis) {
-			return Err(ChannelError::Close("Remote HTLC add would put them over their max HTLC value in flight"));
+			return Err(ChannelError::Close("Remote HTLC add would put them over our max HTLC value"));
 		}
 		// Check our_channel_reserve_satoshis (we're getting paid, so they have to at least meet
 		// the reserve_satoshis we told them to always have as direct payment so that they lose
@@ -3214,16 +3213,15 @@ impl Channel {
 		if outbound_htlc_count + 1 > self.their_max_accepted_htlcs as u32 {
 			return Err(ChannelError::Ignore("Cannot push more than their max accepted HTLCs"));
 		}
-		//TODO: Spec is unclear if this is per-direction or in total (I assume per direction):
 		// Check their_max_htlc_value_in_flight_msat
 		if htlc_outbound_value_msat + amount_msat > self.their_max_htlc_value_in_flight_msat {
-			return Err(ChannelError::Ignore("Cannot send value that would put us over the max HTLC value in flight"));
+			return Err(ChannelError::Ignore("Cannot send value that would put us over the max HTLC value in flight our peer will accept"));
 		}
 
 		// Check self.their_channel_reserve_satoshis (the amount we must keep as
 		// reserve for them to have something to claim if we misbehave)
 		if self.value_to_self_msat < self.their_channel_reserve_satoshis * 1000 + amount_msat + htlc_outbound_value_msat {
-			return Err(ChannelError::Ignore("Cannot send value that would put us over the reserve value"));
+			return Err(ChannelError::Ignore("Cannot send value that would put us over their reserve value"));
 		}
 
 		//TODO: Check cltv_expiry? Do this in channel manager?

src/ln/functional_test_utils.rs

@@ -702,7 +702,7 @@ pub fn route_over_limit(origin_node: &Node, expected_route: &[&Node], recv_value
 
 	let err = origin_node.node.send_payment(route, our_payment_hash).err().unwrap();
 	match err {
-		APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the max HTLC value in flight"),
+		APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the max HTLC value in flight our peer will accept"),
 		_ => panic!("Unknown error variants"),
 	};
 }

src/ln/functional_tests.rs

@@ -1235,7 +1235,7 @@ fn do_channel_reserve_test(test_recv: bool) {
 		assert!(route.hops.iter().rev().skip(1).all(|h| h.fee_msat == feemsat));
 		let err = nodes[0].node.send_payment(route, our_payment_hash).err().unwrap();
 		match err {
-			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the max HTLC value in flight"),
+			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the max HTLC value in flight our peer will accept"),
 			_ => panic!("Unknown error variants"),
 		}
 	}
@@ -1271,7 +1271,7 @@ fn do_channel_reserve_test(test_recv: bool) {
 		let (route, our_payment_hash, _) = get_route_and_payment_hash!(recv_value + 1);
 		let err = nodes[0].node.send_payment(route.clone(), our_payment_hash).err().unwrap();
 		match err {
-			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the reserve value"),
+			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over their reserve value"),
 			_ => panic!("Unknown error variants"),
 		}
 	}
@@ -1296,7 +1296,7 @@ fn do_channel_reserve_test(test_recv: bool) {
 	{
 		let (route, our_payment_hash, _) = get_route_and_payment_hash!(recv_value_2 + 1);
 		match nodes[0].node.send_payment(route, our_payment_hash).err().unwrap() {
-			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the reserve value"),
+			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over their reserve value"),
 			_ => panic!("Unknown error variants"),
 		}
 	}
@@ -1359,7 +1359,7 @@ fn do_channel_reserve_test(test_recv: bool) {
 	{
 		let (route, our_payment_hash, _) = get_route_and_payment_hash!(recv_value_22+1);
 		match nodes[0].node.send_payment(route, our_payment_hash).err().unwrap() {
-			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over the reserve value"),
+			APIError::ChannelUnavailable{err} => assert_eq!(err, "Cannot send value that would put us over their reserve value"),
 			_ => panic!("Unknown error variants"),
 		}
 	}
@@ -4852,7 +4852,7 @@ fn test_update_add_htlc_bolt2_sender_exceed_max_htlc_value_in_flight() {
 	let err = nodes[0].node.send_payment(route, our_payment_hash);
 
 	if let Err(APIError::ChannelUnavailable{err}) = err {
-		assert_eq!(err, "Cannot send value that would put us over the max HTLC value in flight");
+		assert_eq!(err, "Cannot send value that would put us over the max HTLC value in flight our peer will accept");
 	} else {
 		assert!(false);
 	}
@@ -4975,7 +4975,7 @@ fn test_update_add_htlc_bolt2_receiver_check_max_in_flight_msat() {
 	let err = nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &updates.update_add_htlcs[0]);
 
 	if let Err(msgs::HandleError{err, action: Some(msgs::ErrorAction::SendErrorMessage {..})}) = err {
-		assert_eq!(err,"Remote HTLC add would put them over their max HTLC value in flight");
+		assert_eq!(err,"Remote HTLC add would put them over our max HTLC value");
 	} else {
 		assert!(false);
 	}