Introduce HTLCDestination enum

lightning/src/ln/channel.rs

@@ -46,6 +46,7 @@ use io;
 use prelude::*;
 use core::{cmp,mem,fmt};
 use core::ops::Deref;
+use std::io::Error;
 #[cfg(any(test, fuzzing, debug_assertions))]
 use sync::Mutex;
 use bitcoin::hashes::hex::ToHex;
@@ -799,6 +800,36 @@ impl fmt::Debug for ChannelError {
 	}
 }
 
+/// Used to return destination of where we are forwarding our HTLC to.
+#[derive(Clone, Debug)]
+pub enum HTLCDestination {
+	OpenChannel { node_id: PublicKey, channel_id: [u8; 32] },
+	Unknown { previous_hop_scid: u64 },
+	Payment { payment_hash: PaymentHash, payment_preimage: Option<PaymentPreimage> },
+}
+
+impl Writeable for HTLCDestination {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
+		match self {
+			HTLCDestination::OpenChannel { ref node_id, ref channel_id } => {
+				0u8.write(writer)?;
+				node_id.write(writer)?;
+				channel_id.write(writer)?;
+			},
+			HTLCDestination::Unknown { ref previous_hop_scid } => {
+				1u8.write(writer)?;
+				previous_hop_scid.write(writer)?;
+			},
+			HTLCDestination::Payment { ref payment_hash, ref payment_preimage } => {
+				2u8.write(writer)?;
+				payment_hash.write(writer)?;
+				payment_preimage.write(writer)?;
+			}
+		}
+		Ok(())
+	}
+}
+
 macro_rules! secp_check {
 	($res: expr, $err: expr) => {
 		match $res {
@@ -5577,7 +5608,7 @@ impl<Signer: Sign> Channel<Signer> {
 	/// those explicitly stated to be allowed after shutdown completes, eg some simple getters).
 	/// Also returns the list of payment_hashes for channels which we can safely fail backwards
 	/// immediately (others we will have to allow to time out).
-	pub fn force_shutdown(&mut self, should_broadcast: bool) -> (Option<(OutPoint, ChannelMonitorUpdate)>, Vec<(HTLCSource, PaymentHash, PublicKey)>) {
+	pub fn force_shutdown(&mut self, should_broadcast: bool) -> (Option<(OutPoint, ChannelMonitorUpdate)>, Vec<(HTLCSource, PaymentHash, HTLCDestination)>) {
 		// Note that we MUST only generate a monitor update that indicates force-closure - we're
 		// called during initialization prior to the chain_monitor in the encompassing ChannelManager
 		// being fully configured in some cases. Thus, its likely any monitor events we generate will
@@ -5591,7 +5622,7 @@ impl<Signer: Sign> Channel<Signer> {
 		for htlc_update in self.holding_cell_htlc_updates.drain(..) {
 			match htlc_update {
 				HTLCUpdateAwaitingACK::AddHTLC { source, payment_hash, .. } => {
-					dropped_outbound_htlcs.push((source, payment_hash, counterparty_node_id));
+					dropped_outbound_htlcs.push((source, payment_hash, HTLCDestination::OpenChannel { node_id: counterparty_node_id, channel_id: self.channel_id }));
 				},
 				_ => {}
 			}