fail intercepted payment

Author: johncantrell97

lightning/src/ln/channelmanager.rs

@@ -3089,9 +3089,20 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 			pending_intercepts.remove(&intercept_id)
 		};
 
-		if let Some(_payment) = pending_intercept {
-			// TODO: what's best way to fail this? in `process_pending_htlc_forwards` it uses that `fail_forward` macro
-			//			 awkward way could be to just use the forward_intercepted_payment code and pick a random scid
+		if let Some(payment) = pending_intercept {
+			if let HTLCForwardInfo::AddHTLC { forward_info, prev_short_channel_id, prev_htlc_id, prev_funding_outpoint, .. } = payment {
+
+				let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
+					short_channel_id: prev_short_channel_id,
+					outpoint: prev_funding_outpoint,
+					htlc_id: prev_htlc_id,
+					incoming_packet_shared_secret: forward_info.incoming_shared_secret,
+					phantom_shared_secret: None,
+				});
+
+				let failure_reason = HTLCFailReason::Reason { failure_code: 0x4000 | 10, data: Vec::new() };
+				self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_source, &forward_info.payment_hash, failure_reason);
+			}
 		}
 	}