Add MPPFragmentFailed event

This will be used in upcoming commits to improve our interface for failed
payments.

Author: valentinewallace

lightning/src/routing/router.rs

@@ -28,7 +28,7 @@ use core::cmp;
 use core::ops::Deref;
 
 /// A hop in a route
-#[derive(Clone, Hash, PartialEq, Eq)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
 pub struct RouteHop {
 	/// The node_id of the node at this hop.
 	pub pubkey: PublicKey,

lightning/src/util/events.rs

@@ -17,6 +17,7 @@
 use ln::msgs;
 use ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 use chain::keysinterface::SpendableOutputDescriptor;
+use routing::router::RouteHop;
 use util::ser::{Writeable, Writer, MaybeReadable, Readable, VecReadWrapper, VecWriteWrapper};
 
 use bitcoin::blockdata::script::Script;
@@ -137,6 +138,14 @@ pub enum Event {
 #[cfg(test)]
 		error_data: Option<Vec<u8>>,
 	},
+	/// Indicates an outbound MPP payment partially failed. Probably some intermediary node dropped
+	/// something. You may wish to retry this portion of the payment with a different path.
+	MPPFragmentFailed {
+		/// The hash which was given to ChannelManager::send_payment.
+		payment_hash: PaymentHash,
+		/// The path that failed.
+		payment_path: Vec<RouteHop>,
+	},
 	/// Used to indicate that ChannelManager::process_pending_htlc_forwards should be called at a
 	/// time in the future.
 	PendingHTLCsForwardable {
@@ -250,6 +259,13 @@ impl Writeable for Event {
 					(2, claim_from_onchain_tx, required),
 				});
 			},
+			&Event::MPPFragmentFailed { ref payment_hash, ref payment_path } => {
+				9u8.write(writer)?;
+				write_tlv_fields!(writer, {
+					(0, payment_hash, required),
+					(2, payment_path, vec_type),
+				});
+			},
 		}
 		Ok(())
 	}
@@ -357,6 +373,18 @@ impl MaybeReadable for Event {
 				};
 				f()
 			},
+			9u8 => {
+				let f = || {
+					let mut payment_hash = PaymentHash([0; 32]);
+					let mut payment_path = None;
+					read_tlv_fields!(reader, {
+						(0, payment_hash, required),
+						(2, payment_path, vec_type),
+					});
+					Ok(Some(Event::MPPFragmentFailed { payment_hash, payment_path: payment_path.unwrap() }))
+				};
+				f()
+			}
 			// Versions prior to 0.0.100 did not ignore odd types, instead returning InvalidValue.
 			x if x % 2 == 1 => Ok(None),
 			_ => Err(msgs::DecodeError::InvalidValue)