Header Transforms

RouteEntry::requestHeaderTransforms and ResponseEntry::responseHeaderTransforms APIs

Overview

RouteEntry::requestHeaderTransforms and ResponseEntry::responseHeaderTransforms allows filters to obtain request and response header transformations that would be applied by RouteEntry::finalizeRequestHeaders and ResponseEntry::finalizeResponseHeaders respectively.

If you do not have full knowledge that there will be no further route modifications later in the filter chain, you should not use these APIs.

Example usage

To obtain the response header transformations at request time:

Http::FilterHeadersStatus MyFilter::decodeHeaders(
    Http::RequestHeaderMap& headers, bool) {
  auto transforms =
      decoder_callbacks_->route()->routeEntry()->responseHeaderTransforms(
          decoder_callbacks_->streamInfo());

  // Send the response headers back to the client; they will process them later.
  decoder_callbacks_->sendLocalReply(
      Envoy::Http::Code::OK, MySerializedTransforms(transforms), nullptr, Envoy::Grpc::Status::Ok,
      "local_reply");
}

If you want to retrieve the original values rather than the formatted ones, pass /*do_formatting=*/false as the second argument to responseHeaderTransforms.