xDS Interop Client changes for PSM security tests (#25613)

BUILD

@@ -357,6 +357,22 @@ grpc_cc_library(
 
 grpc_cc_library(
     name = "grpc++",
+    language = "c++",
+    select_deps = {
+        "grpc_no_xds": [],
+        "//conditions:default": [
+            "grpc++_xds_client",
+            "grpc++_xds_server",
+        ],
+    },
+    standalone = True,
+    deps = [
+        "grpc++_internals",
+    ],
+)
+
+grpc_cc_library(
+    name = "grpc++_internals",
     srcs = [
         "src/cpp/client/insecure_credentials.cc",
         "src/cpp/client/secure_credentials.cc",
@@ -382,14 +398,6 @@ grpc_cc_library(
     ],
     language = "c++",
     public_hdrs = GRPCXX_PUBLIC_HDRS,
-    select_deps = {
-        "grpc_no_xds": [],
-        "//conditions:default": [
-            "grpc++_xds_client",
-            "grpc++_xds_server",
-        ],
-    },
-    standalone = True,
     deps = [
         "gpr",
         "grpc",
@@ -411,7 +419,7 @@ grpc_cc_library(
     ],
     language = "c++",
     deps = [
-        "grpc++_base",
+        "grpc++_internals",
     ],
 )
 
@@ -428,7 +436,7 @@ grpc_cc_library(
         "include/grpcpp/xds_server_builder.h",
     ],
     deps = [
-        "grpc++_base",
+        "grpc++_internals",
     ],
 )
 

test/cpp/interop/xds_interop_client.cc

@@ -59,6 +59,8 @@ ABSL_FLAG(std::string, rpc, "UnaryCall",
 ABSL_FLAG(std::string, metadata, "", "metadata to send with the RPC.");
 ABSL_FLAG(std::string, expect_status, "OK",
           "RPC status for the test RPC to be considered successful");
+ABSL_FLAG(std::string, security, "none",
+          "If set to \"secure\", XdsCredentials are used");
 
 using grpc::Channel;
 using grpc::ClientAsyncResponseReader;
@@ -460,8 +462,12 @@ class XdsUpdateClientConfigureServiceImpl
 void RunTestLoop(std::chrono::duration<double> duration_per_query,
                  StatsWatchers* stats_watchers,
                  RpcConfigurationsQueue* rpc_configs_queue) {
-  TestClient client(grpc::CreateChannel(absl::GetFlag(FLAGS_server),
-                                        grpc::InsecureChannelCredentials()),
+  TestClient client(
+      grpc::CreateChannel(absl::GetFlag(FLAGS_server),
+                          absl::GetFlag(FLAGS_security) == "secure"
+                              ? grpc::experimental::XdsCredentials(
+                                    grpc::InsecureChannelCredentials())
+                              : grpc::InsecureChannelCredentials()),
       stats_watchers);
   std::chrono::time_point<std::chrono::system_clock> start =
       std::chrono::system_clock::now();