Explain how rounded millisat values are included in overall balance

Author: TheBlueMatt

lightning/src/chain/channelmonitor.rs

@@ -635,25 +635,37 @@ pub enum Balance {
 		/// [`Balance::MaybeTimeoutClaimableHTLC`] with their
 		/// [`Balance::MaybeTimeoutClaimableHTLC::outbound_payment`] flag set, as well as any dust
 		/// HTLCs which would otherwise be represented the same.
+		///
+		/// This value will not be included in `amount_satoshis` and any representable (quotient
+		/// when divided by 1000 without the remainder) value will go toward fees 
 		outbound_payment_htlc_rounded_msat: u64,
 		/// The amount of millisatoshis which has been burned to fees from HTLCs which are outbound
 		/// from us and are related to a forwarded HTLC. This is the sum of the millisatoshis part
 		/// of all HTLCs which are otherwise represented by [`Balance::MaybeTimeoutClaimableHTLC`]
 		/// with their [`Balance::MaybeTimeoutClaimableHTLC::outbound_payment`] flag *not* set, as
 		/// well as any dust HTLCs which would otherwise be represented the same.
+		///
+		/// This value will not be included in `amount_satoshis` and any representable (quotient
+		/// when divided by 1000 without the remainder) value will go toward fees 
 		outbound_forwarded_htlc_rounded_msat: u64,
 		/// The amount of millisatoshis which has been burned to fees from HTLCs which are inbound
 		/// to us and for which we know the preimage. This is the sum of the millisatoshis part of
 		/// all HTLCs which would be represented by [`Balance::ContentiousClaimable`] on channel
 		/// close, but who's current value is included in
 		/// [`Balance::ClaimableOnChannelClose::amount_satoshis`], as well as any dust HTLCs which
 		/// would otherwise be represented the same.
+		///
+		/// This value will not be included in `amount_satoshis` and any representable (quotient
+		/// when divided by 1000 without the remainder) value will go toward fees 
 		inbound_claiming_htlc_rounded_msat: u64,
 		/// The amount of millisatoshis which has been burned to fees from HTLCs which are inbound
 		/// to us and for which we do not know the preimage. This is the sum of the millisatoshis
 		/// part of all HTLCs which would be represented by [`Balance::MaybePreimageClaimableHTLC`]
 		/// on channel close, as well as any dust HTLCs which would otherwise be represented the
 		/// same.
+		///
+		/// This value will not be included in `amount_satoshis` and any representable (quotient
+		/// when divided by 1000 without the remainder) value will go toward fees 
 		inbound_htlc_rounded_msat: u64,
 	},
 	/// The channel has been closed, and the given balance is ours but awaiting confirmations until
@@ -2338,6 +2350,9 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 				}
 			}
 		} else {
+			let mut expected_tx_value_sats = if us.holder_pays_commitment_tx_fee.unwrap_or(true) {
+					us.channel_value_satoshis
+				} else { 0 };
 			let mut claimable_inbound_htlc_value_sat = 0;
 			let mut nondust_htlc_count = 0;
 			let mut outbound_payment_htlc_rounded_msat = 0;
@@ -2365,6 +2380,7 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 					} else {
 						outbound_forwarded_htlc_rounded_msat += rounded_value_msat;
 					}
+					expected_tx_value_sats = expected_tx_value_sats.saturating_sub((htlc.amount_msat + 999) / 1000);
 					if htlc.transaction_output_index.is_some() {
 						res.push(Balance::MaybeTimeoutClaimableHTLC {
 							amount_satoshis: htlc.amount_msat / 1000,
@@ -2391,12 +2407,13 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 					}
 				}
 			}
+			let tx_fee_satoshis = chan_utils::commit_tx_fee_sat(
+				us.current_holder_commitment_tx.feerate_per_kw, nondust_htlc_count,
+				us.onchain_tx_handler.channel_type_features());
 			res.push(Balance::ClaimableOnChannelClose {
 				amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat + claimable_inbound_htlc_value_sat,
 				transaction_fee_satoshis: if us.holder_pays_commitment_tx_fee.unwrap_or(true) {
-					chan_utils::commit_tx_fee_sat(
-						us.current_holder_commitment_tx.feerate_per_kw, nondust_htlc_count,
-						us.onchain_tx_handler.channel_type_features())
+					tx_fee_satoshis
 				} else { 0 },
 				outbound_payment_htlc_rounded_msat,
 				outbound_forwarded_htlc_rounded_msat,