f: add drop attribution data test

Author: joostjager

lightning/src/ln/onion_utils.rs

@@ -2810,6 +2810,7 @@ fn process_failure_packet(
 
 #[cfg(test)]
 mod tests {
+	use core::iter;
 	use std::sync::Arc;
 
 	use crate::io;
@@ -3153,14 +3154,18 @@ mod tests {
 
 			for mutation_type in failure_mutations
 				.chain(attribution_data_mutations.map(MutationType::AttributionData))
+				.chain(iter::once(MutationType::DropAttributionData))
 			{
+				// If the mutation is in the attribution data and not in the failure message itself, the invalid
+				// attribution data should be ignored and the failure should still surface.
+				let failure_ok = matches!(mutation_type, MutationType::DropAttributionData)
+					|| matches!(mutation_type, MutationType::AttributionData(_));
+
 				let mutation = Mutation { node: mutating_node, mutation_type };
 				let decrypted_failure =
 					test_attributable_failure_packet_onion_with_mutation(Some(mutation));
 
-				// If the mutation is in the attribution data and not in the failure message itself, the invalid
-				// attribution data should be ignored and the failure should still surface.
-				if mutated_index >= FAILURE_MESSAGE_LEN {
+				if failure_ok {
 					assert_eq!(
 						decrypted_failure.onion_error_code,
 						Some(LocalHTLCFailureReason::IncorrectPaymentDetails)
@@ -3198,6 +3203,7 @@ mod tests {
 	enum MutationType {
 		FailureMessage(usize),
 		AttributionData(AttributionDataMutationType),
+		DropAttributionData,
 	}
 
 	struct Mutation {
@@ -3285,6 +3291,10 @@ mod tests {
 					// Mutate hold times.
 					packet.attribution_data.as_mut().unwrap().hmacs[*i] ^= 1;
 				},
+				MutationType::DropAttributionData => {
+					// Drop attribution data completely. This simulates a node that does not support the feature.
+					packet.attribution_data = None;
+				},
 			}
 		};