Add detection of feature_static_remotekey support and print

This adds the ability to check for static_remotekey in appropriate
feature contexts and prints it at connect time. It is still
considered unknown for the purposes of requires_unknown_bits() as
we don't yet implement it.

Author: TheBlueMatt

lightning/src/ln/features.rs

@@ -34,6 +34,10 @@ mod sealed { // You should just use the type aliases instead.
 	impl VariableLengthOnion for InitContext {}
 	impl VariableLengthOnion for NodeContext {}
 
+	pub trait StaticRemoteKey: Context {}
+	impl StaticRemoteKey for InitContext {}
+	impl StaticRemoteKey for NodeContext {}
+
 	pub trait PaymentSecret: Context {}
 	impl PaymentSecret for InitContext {}
 	impl PaymentSecret for NodeContext {}
@@ -222,8 +226,8 @@ impl<T: sealed::Context> Features<T> {
 				// unknown, upfront_shutdown_script, initial_routing_sync (is only valid as an
 				// optional feature), and data_loss_protect:
 				0 => (byte & 0b11000100),
-				// payment_secret, unknown, unknown, var_onion_optin:
-				1 => (byte & 0b00111100),
+				// payment_secret, static_remotekey, unknown, var_onion_optin:
+				1 => (byte & 0b00001100),
 				// unknown, unknown, unknown, basic_mpp:
 				2 => (byte & 0b11111100),
 				_ => byte,
@@ -293,6 +297,12 @@ impl<T: sealed::InitialRoutingSync> Features<T> {
 	}
 }
 
+impl<T: sealed::StaticRemoteKey> Features<T> {
+	pub(crate) fn supports_static_remote_key(&self) -> bool {
+		self.flags.len() > 1 && (self.flags[1] & (3 << 4)) != 0
+	}
+}
+
 impl<T: sealed::PaymentSecret> Features<T> {
 	#[allow(dead_code)]
 	// Note that we never need to test this since what really matters is the invoice - iff the

lightning/src/ln/peer_handler.rs

@@ -625,10 +625,11 @@ impl<Descriptor: SocketDescriptor, CM: Deref> PeerManager<Descriptor, CM> where
 													return Err(PeerHandleError{ no_connection_possible: false });
 												}
 
-												log_info!(self, "Received peer Init message: data_loss_protect: {}, initial_routing_sync: {}, upfront_shutdown_script: {}, unkown local flags: {}, unknown global flags: {}",
+												log_info!(self, "Received peer Init message: data_loss_protect: {}, initial_routing_sync: {}, upfront_shutdown_script: {}, static_remote_key: {}, unkown local flags: {}, unknown global flags: {}",
 													if msg.features.supports_data_loss_protect() { "supported" } else { "not supported"},
 													if msg.features.initial_routing_sync() { "requested" } else { "not requested" },
 													if msg.features.supports_upfront_shutdown_script() { "supported" } else { "not supported"},
+													if msg.features.supports_static_remote_key() { "supported" } else { "not supported"},
 													if msg.features.supports_unknown_bits() { "present" } else { "none" },
 													if msg.features.supports_unknown_bits() { "present" } else { "none" });