From c2f95b558331c8332aed9ba8717e2826b6488b35 Mon Sep 17 00:00:00 2001
From: Kuat Yessenov <kuat@google.com>
Date: Mon, 9 Jan 2023 23:21:53 +0000
Subject: [PATCH] baggage: allow propagation

Signed-off-by: Kuat Yessenov <kuat@google.com>
---
 .../filters/http/connect_baggage/config.proto |  9 +++++--
 .../filters/http/connect_baggage/filter.cc    | 24 +++++++++++++++----
 .../filters/http/connect_baggage/filter.h     |  4 ++++
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/source/extensions/filters/http/connect_baggage/config.proto b/source/extensions/filters/http/connect_baggage/config.proto
index 3e338b9e91b..37e08c0b62b 100644
--- a/source/extensions/filters/http/connect_baggage/config.proto
+++ b/source/extensions/filters/http/connect_baggage/config.proto
@@ -17,5 +17,10 @@ syntax = "proto3";
 
 package io.istio.http.connect_baggage;
 
-// Computes and stores the downstream peer metadata from the "baggage" header.
-message Config {}
+// Computes or propagates the downstream peer metadata using the "baggage"
+// header.
+message Config {
+  // Write "baggage" header from downstream peer metadata, instead of reading
+  // it.
+  bool propagate = 1;
+}
diff --git a/source/extensions/filters/http/connect_baggage/filter.cc b/source/extensions/filters/http/connect_baggage/filter.cc
index 7963c4efb06..dda96adc27c 100644
--- a/source/extensions/filters/http/connect_baggage/filter.cc
+++ b/source/extensions/filters/http/connect_baggage/filter.cc
@@ -26,10 +26,26 @@ namespace Extensions {
 namespace HttpFilters {
 namespace ConnectBaggage {
 
+constexpr absl::string_view Baggage = "baggage";
+constexpr absl::string_view DownstreamPeerKey = "wasm.downstream_peer";
+
 Http::FilterHeadersStatus Filter::decodeHeaders(Http::RequestHeaderMap& headers,
                                                 bool) {
+  if (propagate_) {
+    const auto* object = decoder_callbacks_->streamInfo()
+                             .filterState()
+                             ->getDataReadOnly<Filters::Common::Expr::CelState>(
+                                 DownstreamPeerKey);
+    if (object) {
+      const auto peer = Istio::Common::convertFlatNodeToWorkloadMetadata(
+          *flatbuffers::GetRoot<Wasm::Common::FlatNode>(
+              object->value().data()));
+      headers.addCopy(Http::LowerCaseString(Baggage), peer.baggage());
+    }
+    return Http::FilterHeadersStatus::Continue;
+  }
   const auto header_string = Http::HeaderUtility::getAllOfHeaderAsString(
-      headers, Http::LowerCaseString("baggage"));
+      headers, Http::LowerCaseString(Baggage));
   const auto result = header_string.result();
   if (result) {
     const auto metadata_object =
@@ -67,10 +83,10 @@ Http::FilterHeadersStatus Filter::decodeHeaders(Http::RequestHeaderMap& headers,
 }
 
 Http::FilterFactoryCb FilterConfigFactory::createFilterFactoryFromProtoTyped(
-    const io::istio::http::connect_baggage::Config&, const std::string&,
+    const io::istio::http::connect_baggage::Config& config, const std::string&,
     Server::Configuration::FactoryContext&) {
-  return [](Http::FilterChainFactoryCallbacks& callbacks) {
-    auto filter = std::make_shared<Filter>();
+  return [config](Http::FilterChainFactoryCallbacks& callbacks) {
+    auto filter = std::make_shared<Filter>(config.propagate());
     callbacks.addStreamFilter(filter);
   };
 }
diff --git a/source/extensions/filters/http/connect_baggage/filter.h b/source/extensions/filters/http/connect_baggage/filter.h
index c9e93f0f743..96fe901ff5d 100644
--- a/source/extensions/filters/http/connect_baggage/filter.h
+++ b/source/extensions/filters/http/connect_baggage/filter.h
@@ -26,8 +26,12 @@ namespace ConnectBaggage {
 
 class Filter : public Http::PassThroughFilter {
  public:
+  Filter(bool propagate) : propagate_(propagate) {}
   Http::FilterHeadersStatus decodeHeaders(Http::RequestHeaderMap&,
                                           bool) override;
+
+ private:
+  bool propagate_;
 };
 
 class FilterConfigFactory