Internal Upstream Transport & Metadata Passthrough

[Eeshu-Yadav]

Implement the InternalUpstreamTransport functionality including metadata passthrough as specified in the Envoy internal upstream transport configuration.

Background

For complete waypoint proxy support, we need to implement metadata passthrough from downstream connections to internal upstream connections. This enables features like original destination preservation and custom metadata flow.

Configuration Structure to Support

transport_socket:
  name: "internal_upstream"
  typed_config:
    "@type": "type.googleapis.com/envoy.extensions.transport_sockets.internal_upstream.v3.InternalUpstreamTransport"
    passthrough_metadata:
      - kind:
          host: {}
        name: "envoy.filters.listener.original_dst"
      - kind:
          cluster: {}
        name: "custom.metadata.key"
    transport_socket:
      name: "raw_buffer"

Core Functionality Needed

async fn apply_internal_upstream_transport(
    connection: &mut InternalConnection,
    transport: &InternalUpstreamTransport,
    downstream_metadata: &DownstreamConnectionMetadata,
) -> Result<()> {
    for metadata_source in &transport.passthrough_metadata {
        let value = extract_metadata(downstream_metadata, metadata_source)?;
        connection.set_metadata(&metadata_source.name, value);
    }
    // Handle nested transport socket...
}

Dependencies

• Blocked by: Cluster Internal Connection Support #107