http: add CONNECT-UDP support (#27714)

Commit Message:
This commit adds CONNECT-UDP (RFC 9298) support. UdpConnPool is added to create a UDP socket for a new CONNECT-UDP request, and UDPUpstream is added to maintain the socket and other relevant data associated with UDP upstreams.

We added an integration test for the terminating CONNECT-UDP proxy, but not the forwarding proxy in this commit. We are going to add test cases to cover the forwarding proxy scenario in a subsequent commit.

Additional Description:
Risk Level: Medium, the feature can only be enabled by the new configuration added in this commit.
Testing: Integration test
Runtime guard: envoy.reloadable_features.enable_connect_udp_support
Release Notes: added support for CONNECT-UDP (RFC 9298). Can be disabled by setting runtime feature envoy.reloadable_features.enable_connect_udp_support to false.

Signed-off-by: Jeongseok Son <jeongseok.son@gmail.com>
Co-authored-by: asingh-g <abhisinghx@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ b4f37553d6887447f942a1aedbc8c2dacae45537

BUILD

@@ -309,6 +309,7 @@ proto_library(
         "//envoy/extensions/upstreams/http/generic/v3:pkg",
         "//envoy/extensions/upstreams/http/http/v3:pkg",
         "//envoy/extensions/upstreams/http/tcp/v3:pkg",
+        "//envoy/extensions/upstreams/http/udp/v3:pkg",
         "//envoy/extensions/upstreams/http/v3:pkg",
         "//envoy/extensions/upstreams/tcp/generic/v3:pkg",
         "//envoy/extensions/upstreams/tcp/v3:pkg",

envoy/extensions/upstreams/http/udp/v3/BUILD

@@ -0,0 +1,9 @@
+# DO NOT EDIT. This file is generated by tools/proto_format/proto_sync.py.
+
+load("@envoy_api//bazel:api_build_system.bzl", "api_proto_package")
+
+licenses(["notice"])  # Apache 2
+
+api_proto_package(
+    deps = ["@com_github_cncf_udpa//udpa/annotations:pkg"],
+)

envoy/extensions/upstreams/http/udp/v3/udp_connection_pool.proto

@@ -0,0 +1,18 @@
+syntax = "proto3";
+
+package envoy.extensions.upstreams.http.udp.v3;
+
+import "udpa/annotations/status.proto";
+
+option java_package = "io.envoyproxy.envoy.extensions.upstreams.http.udp.v3";
+option java_outer_classname = "UdpConnectionPoolProtoOuterClass";
+option java_multiple_files = true;
+option go_package = "github.com/envoyproxy/go-control-plane/envoy/extensions/upstreams/http/udp/v3;udpv3";
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+
+// [#protodoc-title: Udp Connection Pool]
+
+// A connection pool which forwards downstream HTTP as UDP to upstream,
+// [#extension: envoy.upstreams.http.udp]
+message UdpConnectionPoolProto {
+}

versioning/BUILD

@@ -248,6 +248,7 @@ proto_library(
         "//envoy/extensions/upstreams/http/generic/v3:pkg",
         "//envoy/extensions/upstreams/http/http/v3:pkg",
         "//envoy/extensions/upstreams/http/tcp/v3:pkg",
+        "//envoy/extensions/upstreams/http/udp/v3:pkg",
         "//envoy/extensions/upstreams/http/v3:pkg",
         "//envoy/extensions/upstreams/tcp/generic/v3:pkg",
         "//envoy/extensions/upstreams/tcp/v3:pkg",