new addressing + pipeline unification and routing stubs

nym-node/src/node/lp/data/handler/error.rs

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use nym_lp_data::packet::frame::LpFrameKind;
+use nym_sphinx_addressing::clients::ClientAddress;
 use nym_sphinx_addressing::nodes::NymNodeRoutingAddressError;
 use nym_sphinx_forwarding::packet::MixPacketFormattingError;
 use nym_sphinx_framing::processing::PacketProcessingError;
@@ -34,6 +35,12 @@ pub enum LpDataHandlerError {
     #[error("unwrapped a packet into a final hop packet. This is no longer supported")]
     FinalHop,
 
+    #[error("a mix node received a forward hop addressed to a client; only gateways may forward to clients")]
+    ClientForwardHopAtMixNode,
+
+    #[error("no UDP endpoint registered for client {client_addr}")]
+    UnknownClientAddress { client_addr: ClientAddress },
+
     #[error("{0}")]
     Internal(String),