Struct-ify decoded onion failures

To avoid several long hard-to-read tuple return values

lightning/src/ln/onion_utils.rs

@@ -396,15 +396,22 @@ pub(super) fn build_first_hop_failure_packet(shared_secret: &[u8], failure_type:
 	encrypt_failure_packet(shared_secret, &failure_packet.encode()[..])
 }
 
+pub(crate) struct DecodedOnionFailure {
+	pub(crate) network_update: Option<NetworkUpdate>,
+	pub(crate) short_channel_id: Option<u64>,
+	pub(crate) payment_retryable: bool,
+	#[cfg(test)]
+	pub(crate) onion_error_code: Option<u16>,
+	#[cfg(test)]
+	pub(crate) onion_error_data: Option<Vec<u8>>,
+}
+
 /// Process failure we got back from upstream on a payment we sent (implying htlc_source is an
 /// OutboundRoute).
-/// Returns update, a boolean indicating that the payment itself failed, the short channel id of
-/// the responsible channel, and the error code.
 #[inline]
 pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 	secp_ctx: &Secp256k1<T>, logger: &L, htlc_source: &HTLCSource, mut packet_decrypted: Vec<u8>
-) -> (Option<NetworkUpdate>, Option<u64>, bool, Option<u16>, Option<Vec<u8>>)
-where L::Target: Logger {
+) -> DecodedOnionFailure where L::Target: Logger {
 	let (path, session_priv, first_hop_htlc_msat) = if let &HTLCSource::OutboundRoute {
 		ref path, ref session_priv, ref first_hop_htlc_msat, ..
 	} = htlc_source {
@@ -635,11 +642,23 @@ where L::Target: Logger {
 		}
 	}).expect("Route that we sent via spontaneously grew invalid keys in the middle of it?");
 	if let Some((channel_update, short_channel_id, payment_retryable)) = res {
-		(channel_update, short_channel_id, payment_retryable, error_code_ret, error_packet_ret)
+		DecodedOnionFailure {
+			network_update: channel_update, short_channel_id, payment_retryable,
+			#[cfg(test)]
+			onion_error_code: error_code_ret,
+			#[cfg(test)]
+			onion_error_data: error_packet_ret
+		}
 	} else {
 		// only not set either packet unparseable or hmac does not match with any
 		// payment not retryable only when garbage is from the final node
-		(None, None, !is_from_final_node, None, None)
+		DecodedOnionFailure {
+			network_update: None, short_channel_id: None, payment_retryable: !is_from_final_node,
+			#[cfg(test)]
+			onion_error_code: None,
+			#[cfg(test)]
+			onion_error_data: None
+		}
 	}
 }
 
@@ -763,20 +782,28 @@ impl HTLCFailReason {
 
 	pub(super) fn decode_onion_failure<T: secp256k1::Signing, L: Deref>(
 		&self, secp_ctx: &Secp256k1<T>, logger: &L, htlc_source: &HTLCSource
-	) -> (Option<NetworkUpdate>, Option<u64>, bool, Option<u16>, Option<Vec<u8>>)
-	where L::Target: Logger {
+	) -> DecodedOnionFailure where L::Target: Logger {
 		match self.0 {
 			HTLCFailReasonRepr::LightningError { ref err } => {
 				process_onion_failure(secp_ctx, logger, &htlc_source, err.data.clone())
 			},
+			#[allow(unused)]
 			HTLCFailReasonRepr::Reason { ref failure_code, ref data, .. } => {
 				// we get a fail_malformed_htlc from the first hop
 				// TODO: We'd like to generate a NetworkUpdate for temporary
 				// failures here, but that would be insufficient as find_route
 				// generally ignores its view of our own channels as we provide them via
 				// ChannelDetails.
 				if let &HTLCSource::OutboundRoute { ref path, .. } = htlc_source {
-					(None, Some(path.hops[0].short_channel_id), true, Some(*failure_code), Some(data.clone()))
+					DecodedOnionFailure {
+						network_update: None,
+						payment_retryable: true,
+						short_channel_id: Some(path.hops[0].short_channel_id),
+						#[cfg(test)]
+						onion_error_code: Some(*failure_code),
+						#[cfg(test)]
+						onion_error_data: Some(data.clone()),
+					}
 				} else { unreachable!(); }
 			}
 		}

lightning/src/ln/outbound_payment.rs

@@ -17,7 +17,7 @@ use crate::sign::{EntropySource, NodeSigner, Recipient};
 use crate::events::{self, PaymentFailureReason};
 use crate::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 use crate::ln::channelmanager::{ChannelDetails, EventCompletionAction, HTLCSource, IDEMPOTENCY_TIMEOUT_TICKS, PaymentId};
-use crate::ln::onion_utils::HTLCFailReason;
+use crate::ln::onion_utils::{DecodedOnionFailure, HTLCFailReason};
 use crate::routing::router::{InFlightHtlcs, Path, PaymentParameters, Route, RouteParameters, Router};
 use crate::util::errors::APIError;
 use crate::util::logger::Logger;
@@ -1293,9 +1293,12 @@ impl OutboundPayments {
 		pending_events: &Mutex<VecDeque<(events::Event, Option<EventCompletionAction>)>>, logger: &L,
 	) -> bool where L::Target: Logger {
 		#[cfg(test)]
-		let (network_update, short_channel_id, payment_retryable, onion_error_code, onion_error_data) = onion_error.decode_onion_failure(secp_ctx, logger, &source);
+		let DecodedOnionFailure {
+			network_update, short_channel_id, payment_retryable, onion_error_code, onion_error_data
+		} = onion_error.decode_onion_failure(secp_ctx, logger, &source);
 		#[cfg(not(test))]
-		let (network_update, short_channel_id, payment_retryable, _, _) = onion_error.decode_onion_failure(secp_ctx, logger, &source);
+		let DecodedOnionFailure { network_update, short_channel_id, payment_retryable } =
+			onion_error.decode_onion_failure(secp_ctx, logger, &source);
 
 		let payment_is_probe = payment_is_probe(payment_hash, &payment_id, probing_cookie_secret);
 		let mut session_priv_bytes = [0; 32];