http3: adding upstream API hooks (#14839)

Only adding explicit (hard-configured, or downstream-initiated) HTTP/3. Getting Auto for UDP/TCP is going to take substantially more work. HTTP/3 config will be rejected initially to keep this PR simple as possible.

Risk Level: Low (unused, hidden)
Testing: new unit tests
Docs Changes: n/a
Release Notes: n/a
Part of #14829
Signed-off-by: Alyssa Wilk <alyssar@chromium.org>

Mirrored from https://github.com/envoyproxy/envoy @ d06b41c670e29de9d09f0f088e007611f3800db9

envoy/config/core/v3/protocol.proto

@@ -389,3 +389,11 @@ message GrpcProtocolOptions {
 
   Http2ProtocolOptions http2_protocol_options = 1;
 }
+
+// [#not-implemented-hide:]
+//
+// A message which allows using HTTP/3 as an upstream protocol.
+//
+// Eventually this will include configuration for tuning HTTP/3.
+message Http3ProtocolOptions {
+}

envoy/config/core/v4alpha/protocol.proto

@@ -382,3 +382,13 @@ message GrpcProtocolOptions {
 
   Http2ProtocolOptions http2_protocol_options = 1;
 }
+
+// [#not-implemented-hide:]
+//
+// A message which allows using HTTP/3 as an upstream protocol.
+//
+// Eventually this will include configuration for tuning HTTP/3.
+message Http3ProtocolOptions {
+  option (udpa.annotations.versioning).previous_message_type =
+      "envoy.config.core.v3.Http3ProtocolOptions";
+}

envoy/extensions/upstreams/http/v3/http_protocol_options.proto

@@ -58,7 +58,7 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 //        .... [further cluster config]
 // [#next-free-field: 6]
 message HttpProtocolOptions {
-  // If this is used, the cluster will only operate on one of the possible upstream protocols (HTTP/1.1, HTTP/2).
+  // If this is used, the cluster will only operate on one of the possible upstream protocols.
   // Note that HTTP/2 should generally be used for upstream clusters doing gRPC.
   message ExplicitHttpConfig {
     oneof protocol_config {
@@ -67,6 +67,9 @@ message HttpProtocolOptions {
       config.core.v3.Http1ProtocolOptions http_protocol_options = 1;
 
       config.core.v3.Http2ProtocolOptions http2_protocol_options = 2;
+
+      // [#not-implemented-hide:]
+      config.core.v3.Http3ProtocolOptions http3_protocol_options = 3;
     }
   }
 
@@ -76,6 +79,9 @@ message HttpProtocolOptions {
     config.core.v3.Http1ProtocolOptions http_protocol_options = 1;
 
     config.core.v3.Http2ProtocolOptions http2_protocol_options = 2;
+
+    // [#not-implemented-hide:]
+    config.core.v3.Http3ProtocolOptions http3_protocol_options = 3;
   }
 
   // If this is used, the cluster can use either HTTP/1 or HTTP/2, and will use whichever

envoy/extensions/upstreams/http/v4alpha/http_protocol_options.proto

@@ -62,7 +62,7 @@ message HttpProtocolOptions {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.extensions.upstreams.http.v3.HttpProtocolOptions";
 
-  // If this is used, the cluster will only operate on one of the possible upstream protocols (HTTP/1.1, HTTP/2).
+  // If this is used, the cluster will only operate on one of the possible upstream protocols.
   // Note that HTTP/2 should generally be used for upstream clusters doing gRPC.
   message ExplicitHttpConfig {
     option (udpa.annotations.versioning).previous_message_type =
@@ -74,6 +74,9 @@ message HttpProtocolOptions {
       config.core.v4alpha.Http1ProtocolOptions http_protocol_options = 1;
 
       config.core.v4alpha.Http2ProtocolOptions http2_protocol_options = 2;
+
+      // [#not-implemented-hide:]
+      config.core.v4alpha.Http3ProtocolOptions http3_protocol_options = 3;
     }
   }
 
@@ -86,6 +89,9 @@ message HttpProtocolOptions {
     config.core.v4alpha.Http1ProtocolOptions http_protocol_options = 1;
 
     config.core.v4alpha.Http2ProtocolOptions http2_protocol_options = 2;
+
+    // [#not-implemented-hide:]
+    config.core.v4alpha.Http3ProtocolOptions http3_protocol_options = 3;
   }
 
   // If this is used, the cluster can use either HTTP/1 or HTTP/2, and will use whichever