http1 encode trailers in chunk encoding (#8667)

Signed-off-by: Chuong Vu <chuongv@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ cbf565fed3ecf04df7be9b90c3f1384396c54012

envoy/api/v2/core/protocol.proto

@@ -46,6 +46,7 @@ message HttpProtocolOptions {
   google.protobuf.UInt32Value max_headers_count = 2 [(validate.rules).uint32 = {gte: 1}];
 }
 
+// [#next-free-field: 6]
 message Http1ProtocolOptions {
   message HeaderKeyFormat {
     message ProperCaseWords {
@@ -83,6 +84,17 @@ message Http1ProtocolOptions {
   // Describes how the keys for response headers should be formatted. By default, all header keys
   // are lower cased.
   HeaderKeyFormat header_key_format = 4;
+
+  // Enables trailers for HTTP/1. By default the HTTP/1 codec drops proxied trailers.
+  //
+  // .. attention::
+  //
+  //   Note that this only happens when Envoy is chunk encoding which occurs when:
+  //   - The request is HTTP/1.1.
+  //   - Is neither a HEAD only request nor a HTTP Upgrade.
+  //   - Not a response to a HEAD request.
+  //   - The content length header is not present.
+  bool enable_trailers = 5;
 }
 
 // [#next-free-field: 13]

envoy/api/v3alpha/core/protocol.proto

@@ -53,6 +53,7 @@ message HttpProtocolOptions {
   google.protobuf.UInt32Value max_headers_count = 2 [(validate.rules).uint32 = {gte: 1}];
 }
 
+// [#next-free-field: 6]
 message Http1ProtocolOptions {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.api.v2.core.Http1ProtocolOptions";
@@ -98,6 +99,17 @@ message Http1ProtocolOptions {
   // Describes how the keys for response headers should be formatted. By default, all header keys
   // are lower cased.
   HeaderKeyFormat header_key_format = 4;
+
+  // Enables trailers for HTTP/1. By default the HTTP/1 codec drops proxied trailers.
+  //
+  // .. attention::
+  //
+  //   Note that this only happens when Envoy is chunk encoding which occurs when:
+  //   - The request is HTTP/1.1.
+  //   - Is neither a HEAD only request nor a HTTP Upgrade.
+  //   - Not a response to a HEAD request.
+  //   - The content length header is not present.
+  bool enable_trailers = 5;
 }
 
 // [#next-free-field: 13]