Config proto for Secure Session Agent (S2A) transport socket extension. (#16183)

Config proto for Secure Session Agent (S2A) transport socket extension (#16110).

Signed-off-by: Tavish Vaidya <tavish@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ abe2f9b4af4b3c697ee8b3fda934aa2e181bc5ef

BUILD

@@ -263,6 +263,7 @@ proto_library(
         "//envoy/extensions/transport_sockets/proxy_protocol/v3:pkg",
         "//envoy/extensions/transport_sockets/quic/v3:pkg",
         "//envoy/extensions/transport_sockets/raw_buffer/v3:pkg",
+        "//envoy/extensions/transport_sockets/s2a/v3alpha:pkg",
         "//envoy/extensions/transport_sockets/starttls/v3:pkg",
         "//envoy/extensions/transport_sockets/tap/v3:pkg",
         "//envoy/extensions/transport_sockets/tls/v3:pkg",

envoy/extensions/transport_sockets/s2a/v3alpha/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/transport_sockets/s2a/v3alpha/s2a.proto

@@ -0,0 +1,22 @@
+syntax = "proto3";
+
+package envoy.extensions.transport_sockets.s2a.v3alpha;
+
+import "udpa/annotations/status.proto";
+import "validate/validate.proto";
+
+option java_package = "io.envoyproxy.envoy.extensions.transport_sockets.s2a.v3alpha";
+option java_outer_classname = "S2aProto";
+option java_multiple_files = true;
+option (udpa.annotations.file_status).work_in_progress = true;
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+
+// [#not-implemented-hide:]
+// Configuration for S2A transport socket. This allows Envoy clients to
+// configure how to offload mTLS handshakes to the S2A service.
+// https://github.com/google/s2a-core#readme
+message S2AConfiguration {
+  // The address of the S2A. This can be an IP address or a hostname,
+  // followed by a port number.
+  string s2a_address = 1 [(validate.rules).string = {min_len: 1}];
+}

versioning/BUILD

@@ -146,6 +146,7 @@ proto_library(
         "//envoy/extensions/transport_sockets/proxy_protocol/v3:pkg",
         "//envoy/extensions/transport_sockets/quic/v3:pkg",
         "//envoy/extensions/transport_sockets/raw_buffer/v3:pkg",
+        "//envoy/extensions/transport_sockets/s2a/v3alpha:pkg",
         "//envoy/extensions/transport_sockets/starttls/v3:pkg",
         "//envoy/extensions/transport_sockets/tap/v3:pkg",
         "//envoy/extensions/transport_sockets/tls/v3:pkg",