Persist update_add sender skimmed fee in Channel

Author: valentinewallace

lightning/src/ln/channel.rs

@@ -224,6 +224,7 @@ struct OutboundHTLCOutput {
 	payment_hash: PaymentHash,
 	state: OutboundHTLCState,
 	source: HTLCSource,
+	skimmed_fee_msat: Option<u64>,
 }
 
 /// See AwaitingRemoteRevoke ChannelState for more info
@@ -235,6 +236,8 @@ enum HTLCUpdateAwaitingACK {
 		payment_hash: PaymentHash,
 		source: HTLCSource,
 		onion_routing_packet: msgs::OnionPacket,
+		// The extra fee we're skimming off the top of this HTLC.
+		skimmed_fee_msat: Option<u64>,
 	},
 	ClaimHTLC {
 		payment_preimage: PaymentPreimage,
@@ -5126,6 +5129,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 				cltv_expiry,
 				source,
 				onion_routing_packet,
+				skimmed_fee_msat: None,
 			});
 			return Ok(None);
 		}
@@ -5137,6 +5141,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 			cltv_expiry,
 			state: OutboundHTLCState::LocalAnnounced(Box::new(onion_routing_packet.clone())),
 			source,
+			skimmed_fee_msat: None,
 		});
 
 		let res = msgs::UpdateAddHTLC {
@@ -6611,9 +6616,10 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
 		}
 
 		let mut preimages: Vec<&Option<PaymentPreimage>> = vec![];
+		let mut pending_outbound_skimmed_fees: Vec<Option<u64>> = Vec::new();
 
 		(self.context.pending_outbound_htlcs.len() as u64).write(writer)?;
-		for htlc in self.context.pending_outbound_htlcs.iter() {
+		for (idx, htlc) in self.context.pending_outbound_htlcs.iter().enumerate() {
 			htlc.htlc_id.write(writer)?;
 			htlc.amount_msat.write(writer)?;
 			htlc.cltv_expiry.write(writer)?;
@@ -6649,18 +6655,37 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
 					reason.write(writer)?;
 				}
 			}
+			if let Some(skimmed_fee) = htlc.skimmed_fee_msat {
+				if pending_outbound_skimmed_fees.is_empty() {
+					for _ in 0..idx { pending_outbound_skimmed_fees.push(None); }
+				}
+				pending_outbound_skimmed_fees.push(Some(skimmed_fee));
+			} else if !pending_outbound_skimmed_fees.is_empty() {
+				pending_outbound_skimmed_fees.push(None);
+			}
 		}
 
+		let mut holding_cell_skimmed_fees: Vec<Option<u64>> = Vec::new();
 		(self.context.holding_cell_htlc_updates.len() as u64).write(writer)?;
-		for update in self.context.holding_cell_htlc_updates.iter() {
+		for (idx, update) in self.context.holding_cell_htlc_updates.iter().enumerate() {
 			match update {
-				&HTLCUpdateAwaitingACK::AddHTLC { ref amount_msat, ref cltv_expiry, ref payment_hash, ref source, ref onion_routing_packet } => {
+				&HTLCUpdateAwaitingACK::AddHTLC {
+					ref amount_msat, ref cltv_expiry, ref payment_hash, ref source, ref onion_routing_packet,
+					skimmed_fee_msat,
+				} => {
 					0u8.write(writer)?;
 					amount_msat.write(writer)?;
 					cltv_expiry.write(writer)?;
 					payment_hash.write(writer)?;
 					source.write(writer)?;
 					onion_routing_packet.write(writer)?;
+
+					if let Some(skimmed_fee) = skimmed_fee_msat {
+						if holding_cell_skimmed_fees.is_empty() {
+							for _ in 0..idx { holding_cell_skimmed_fees.push(None); }
+						}
+						holding_cell_skimmed_fees.push(Some(skimmed_fee));
+					} else if !holding_cell_skimmed_fees.is_empty() { holding_cell_skimmed_fees.push(None); }
 				},
 				&HTLCUpdateAwaitingACK::ClaimHTLC { ref payment_preimage, ref htlc_id } => {
 					1u8.write(writer)?;
@@ -6827,6 +6852,8 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
 			(29, self.context.temporary_channel_id, option),
 			(31, channel_pending_event_emitted, option),
 			(33, self.context.pending_monitor_updates, vec_type),
+			(35, pending_outbound_skimmed_fees, optional_vec),
+			(37, holding_cell_skimmed_fees, optional_vec),
 		});
 
 		Ok(())
@@ -6937,6 +6964,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 					},
 					_ => return Err(DecodeError::InvalidValue),
 				},
+				skimmed_fee_msat: None,
 			});
 		}
 
@@ -6950,6 +6978,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 					payment_hash: Readable::read(reader)?,
 					source: Readable::read(reader)?,
 					onion_routing_packet: Readable::read(reader)?,
+					skimmed_fee_msat: None,
 				},
 				1 => HTLCUpdateAwaitingACK::ClaimHTLC {
 					payment_preimage: Readable::read(reader)?,
@@ -7105,6 +7134,9 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 
 		let mut pending_monitor_updates = Some(Vec::new());
 
+		let mut pending_outbound_skimmed_fees_opt: Option<Vec<Option<u64>>> = None;
+		let mut holding_cell_skimmed_fees_opt: Option<Vec<Option<u64>>> = None;
+
 		read_tlv_fields!(reader, {
 			(0, announcement_sigs, option),
 			(1, minimum_depth, option),
@@ -7128,6 +7160,8 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 			(29, temporary_channel_id, option),
 			(31, channel_pending_event_emitted, option),
 			(33, pending_monitor_updates, vec_type),
+			(35, pending_outbound_skimmed_fees_opt, optional_vec),
+			(37, holding_cell_skimmed_fees_opt, optional_vec),
 		});
 
 		let (channel_keys_id, holder_signer) = if let Some(channel_keys_id) = channel_keys_id {
@@ -7182,6 +7216,25 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
 
 		let holder_max_accepted_htlcs = holder_max_accepted_htlcs.unwrap_or(DEFAULT_MAX_HTLCS);
 
+		if let Some(skimmed_fees) = pending_outbound_skimmed_fees_opt {
+			let mut iter = skimmed_fees.into_iter();
+			for htlc in pending_outbound_htlcs.iter_mut() {
+				htlc.skimmed_fee_msat = iter.next().ok_or(DecodeError::InvalidValue)?;
+			}
+			// We expect all skimmed fees to be consumed above
+			if iter.next().is_some() { return Err(DecodeError::InvalidValue) }
+		}
+		if let Some(skimmed_fees) = holding_cell_skimmed_fees_opt {
+			let mut iter = skimmed_fees.into_iter();
+			for htlc in holding_cell_htlc_updates.iter_mut() {
+				if let HTLCUpdateAwaitingACK::AddHTLC { ref mut skimmed_fee_msat, .. } = htlc {
+					*skimmed_fee_msat = iter.next().ok_or(DecodeError::InvalidValue)?;
+				}
+			}
+			// We expect all skimmed fees to be consumed above
+			if iter.next().is_some() { return Err(DecodeError::InvalidValue) }
+		}
+
 		Ok(Channel {
 			context: ChannelContext {
 				user_id,
@@ -7524,7 +7577,8 @@ mod tests {
 				session_priv: SecretKey::from_slice(&hex::decode("0fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap()[..]).unwrap(),
 				first_hop_htlc_msat: 548,
 				payment_id: PaymentId([42; 32]),
-			}
+			},
+			skimmed_fee_msat: None,
 		});
 
 		// Make sure when Node A calculates their local commitment transaction, none of the HTLCs pass
@@ -8081,6 +8135,7 @@ mod tests {
 				payment_hash: PaymentHash([0; 32]),
 				state: OutboundHTLCState::Committed,
 				source: HTLCSource::dummy(),
+				skimmed_fee_msat: None,
 			};
 			out.payment_hash.0 = Sha256::hash(&hex::decode("0202020202020202020202020202020202020202020202020202020202020202").unwrap()).into_inner();
 			out
@@ -8093,6 +8148,7 @@ mod tests {
 				payment_hash: PaymentHash([0; 32]),
 				state: OutboundHTLCState::Committed,
 				source: HTLCSource::dummy(),
+				skimmed_fee_msat: None,
 			};
 			out.payment_hash.0 = Sha256::hash(&hex::decode("0303030303030303030303030303030303030303030303030303030303030303").unwrap()).into_inner();
 			out
@@ -8494,6 +8550,7 @@ mod tests {
 				payment_hash: PaymentHash([0; 32]),
 				state: OutboundHTLCState::Committed,
 				source: HTLCSource::dummy(),
+				skimmed_fee_msat: None,
 			};
 			out.payment_hash.0 = Sha256::hash(&hex::decode("0505050505050505050505050505050505050505050505050505050505050505").unwrap()).into_inner();
 			out
@@ -8506,6 +8563,7 @@ mod tests {
 				payment_hash: PaymentHash([0; 32]),
 				state: OutboundHTLCState::Committed,
 				source: HTLCSource::dummy(),
+				skimmed_fee_msat: None,
 			};
 			out.payment_hash.0 = Sha256::hash(&hex::decode("0505050505050505050505050505050505050505050505050505050505050505").unwrap()).into_inner();
 			out