Add RouteBlinding feature flag

The RouteBlinding feature flag is signals support for relaying payments
over blinded paths. It is used for paying BOLT 12 invoices, which are
required to included at least one blinded path.

Author: jkczyz

lightning/src/ln/features.rs

@@ -45,6 +45,8 @@
 //!     and HTLC transactions are pre-signed with zero fee (see
 //!     [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more
 //!     information).
+//! - `RouteBlinding` - requires/supports that a node can relay payments over blinded paths
+//!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#route-blinding) for more information).
 //! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
 //!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
 //! - `OnionMessages` - requires/supports forwarding onion messages
@@ -136,7 +138,7 @@ mod sealed {
 		// Byte 2
 		BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
 		// Byte 3
-		ShutdownAnySegwit,
+		RouteBlinding | ShutdownAnySegwit,
 		// Byte 4
 		OnionMessages,
 		// Byte 5
@@ -152,7 +154,7 @@ mod sealed {
 		// Byte 2
 		BasicMPP | Wumbo | AnchorsZeroFeeHtlcTx,
 		// Byte 3
-		ShutdownAnySegwit,
+		RouteBlinding | ShutdownAnySegwit,
 		// Byte 4
 		OnionMessages,
 		// Byte 5
@@ -381,6 +383,9 @@ mod sealed {
 	define_feature!(23, AnchorsZeroFeeHtlcTx, [InitContext, NodeContext, ChannelTypeContext],
 		"Feature flags for `option_anchors_zero_fee_htlc_tx`.", set_anchors_zero_fee_htlc_tx_optional,
 		set_anchors_zero_fee_htlc_tx_required, supports_anchors_zero_fee_htlc_tx, requires_anchors_zero_fee_htlc_tx);
+	define_feature!(25, RouteBlinding, [InitContext, NodeContext],
+		"Feature flags for `option_route_blinding`.", set_route_blinding_optional,
+		set_route_blinding_required, supports_route_blinding, requires_route_blinding);
 	define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
 		"Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
 		set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
@@ -882,6 +887,7 @@ mod tests {
 		init_features.set_basic_mpp_optional();
 		init_features.set_wumbo_optional();
 		init_features.set_anchors_zero_fee_htlc_tx_optional();
+		init_features.set_route_blinding_optional();
 		init_features.set_shutdown_any_segwit_optional();
 		init_features.set_onion_messages_optional();
 		init_features.set_channel_type_optional();
@@ -898,15 +904,15 @@ mod tests {
 			// - option_data_loss_protect (req)
 			// - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
 			// - basic_mpp | wumbo | option_anchors_zero_fee_htlc_tx
-			// - opt_shutdown_anysegwit
+			// - option_route_blinding | opt_shutdown_anysegwit
 			// - onion_messages
 			// - option_channel_type | option_scid_alias
 			// - option_zeroconf
 			assert_eq!(node_features.flags.len(), 7);
 			assert_eq!(node_features.flags[0], 0b00000001);
 			assert_eq!(node_features.flags[1], 0b01010001);
 			assert_eq!(node_features.flags[2], 0b10001010);
-			assert_eq!(node_features.flags[3], 0b00001000);
+			assert_eq!(node_features.flags[3], 0b00001010);
 			assert_eq!(node_features.flags[4], 0b10000000);
 			assert_eq!(node_features.flags[5], 0b10100000);
 			assert_eq!(node_features.flags[6], 0b00001000);