Default to creating BOLT4 tlv payload format onions

Default to creating tlv onions for nodes for which we haven't received
any features through node announcements, and where no other features are
known such as invoice features nor features in the init msg for nodes we
have channels to.

Author: ViktorT-11

lightning/src/routing/router.rs

@@ -1101,7 +1101,9 @@ where L::Target: Logger {
 		} }
 	}
 
-	let empty_node_features = NodeFeatures::empty();
+	let mut onion_format_optional_features = NodeFeatures::empty();
+	onion_format_optional_features.set_variable_length_onion_optional();
+
 	// Find ways (channels with destination) to reach a given node and store them
 	// in the corresponding data structures (routing graph etc).
 	// $fee_to_target_msat represents how much it costs to reach to this node from the payee,
@@ -1132,7 +1134,7 @@ where L::Target: Logger {
 				let features = if let Some(node_info) = $node.announcement_info.as_ref() {
 					&node_info.features
 				} else {
-					&empty_node_features
+					&onion_format_optional_features
 				};
 
 				if !features.requires_unknown_bits() {
@@ -1312,7 +1314,7 @@ where L::Target: Logger {
 			// traversing the graph and arrange the path out of what we found.
 			if node_id == our_node_id {
 				let mut new_entry = dist.remove(&our_node_id).unwrap();
-				let mut ordered_hops = vec!((new_entry.clone(), NodeFeatures::empty()));
+				let mut ordered_hops = vec!((new_entry.clone(), onion_format_optional_features.clone()));
 
 				'path_walk: loop {
 					let mut features_set = false;
@@ -1330,7 +1332,7 @@ where L::Target: Logger {
 							if let Some(node_info) = node.announcement_info.as_ref() {
 								ordered_hops.last_mut().unwrap().1 = node_info.features.clone();
 							} else {
-								ordered_hops.last_mut().unwrap().1 = NodeFeatures::empty();
+								ordered_hops.last_mut().unwrap().1 = onion_format_optional_features.clone();
 							}
 						} else {
 							// We can fill in features for everything except hops which were
@@ -1357,7 +1359,7 @@ where L::Target: Logger {
 					// so that fees paid for a HTLC forwarding on the current channel are
 					// associated with the previous channel (where they will be subtracted).
 					ordered_hops.last_mut().unwrap().0.fee_msat = new_entry.hop_use_fee_msat;
-					ordered_hops.push((new_entry.clone(), NodeFeatures::empty()));
+					ordered_hops.push((new_entry.clone(), onion_format_optional_features.clone()));
 				}
 				ordered_hops.last_mut().unwrap().0.fee_msat = value_contribution_msat;
 				ordered_hops.last_mut().unwrap().0.hop_use_fee_msat = 0;
@@ -1845,6 +1847,10 @@ mod tests {
 		}
 	}
 
+	fn default_onion_format_flags() -> Vec<u8> {
+		vec![0, 2]
+	}
+
 	fn build_graph() -> (
 		Secp256k1<All>,
 		sync::Arc<NetworkGraph>,
@@ -2785,7 +2791,7 @@ mod tests {
 		assert_eq!(route.paths[0][4].short_channel_id, 8);
 		assert_eq!(route.paths[0][4].fee_msat, 100);
 		assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][4].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 	}
 
@@ -2861,7 +2867,7 @@ mod tests {
 		assert_eq!(route.paths[0][4].short_channel_id, 8);
 		assert_eq!(route.paths[0][4].fee_msat, 100);
 		assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][4].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 	}
 
@@ -2958,7 +2964,7 @@ mod tests {
 		assert_eq!(route.paths[0][3].short_channel_id, last_hops[0].0[1].short_channel_id);
 		assert_eq!(route.paths[0][3].fee_msat, 100);
 		assert_eq!(route.paths[0][3].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][3].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][3].node_features.le_flags(), &vec![0, 2]); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][3].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 	}
 
@@ -3023,14 +3029,14 @@ mod tests {
 		assert_eq!(route.paths[0][2].short_channel_id, last_hops[0].0[0].short_channel_id);
 		assert_eq!(route.paths[0][2].fee_msat, 0);
 		assert_eq!(route.paths[0][2].cltv_expiry_delta, 129);
-		assert_eq!(route.paths[0][2].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][2].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][2].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 
 		assert_eq!(route.paths[0][3].pubkey, nodes[6]);
 		assert_eq!(route.paths[0][3].short_channel_id, last_hops[0].0[1].short_channel_id);
 		assert_eq!(route.paths[0][3].fee_msat, 100);
 		assert_eq!(route.paths[0][3].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][3].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][3].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][3].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 	}
 
@@ -3121,7 +3127,7 @@ mod tests {
 		assert_eq!(route.paths[0][4].short_channel_id, 8);
 		assert_eq!(route.paths[0][4].fee_msat, 100);
 		assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][4].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 	}
 
@@ -3151,7 +3157,7 @@ mod tests {
 		assert_eq!(route.paths[0][1].short_channel_id, 8);
 		assert_eq!(route.paths[0][1].fee_msat, 100);
 		assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][1].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][1].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][1].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 
 		last_hops[0].0[0].fees.base_msat = 1000;
@@ -3188,7 +3194,7 @@ mod tests {
 		assert_eq!(route.paths[0][3].short_channel_id, 10);
 		assert_eq!(route.paths[0][3].fee_msat, 100);
 		assert_eq!(route.paths[0][3].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][3].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][3].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][3].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 
 		// ...but still use 8 for larger payments as 6 has a variable feerate
@@ -3229,7 +3235,7 @@ mod tests {
 		assert_eq!(route.paths[0][4].short_channel_id, 8);
 		assert_eq!(route.paths[0][4].fee_msat, 2000);
 		assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][4].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
 	}
 
@@ -3281,7 +3287,7 @@ mod tests {
 		assert_eq!(route.paths[0][1].short_channel_id, 8);
 		assert_eq!(route.paths[0][1].fee_msat, 1000000);
 		assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
-		assert_eq!(route.paths[0][1].node_features.le_flags(), &[0; 0]); // We dont pass flags in from invoices yet
+		assert_eq!(route.paths[0][1].node_features.le_flags(), &default_onion_format_flags()); // We dont pass flags in from invoices yet
 		assert_eq!(route.paths[0][1].channel_features.le_flags(), &[0; 0]); // We can't learn any flags from invoices, sadly
 	}