From 6b46f470d101e9ad1c8a02a4c8cb06fb53a0d300 Mon Sep 17 00:00:00 2001
From: Doug Fawley <dfawley@google.com>
Date: Fri, 20 Sep 2019 16:07:23 -0700
Subject: [PATCH] =?UTF-8?q?client:=20consider=20service=20config=20invalid?=
 =?UTF-8?q?=20if=20loadBalancingConfig=E2=80=A6=20(#3034)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 service_config.go      |  8 ++++++++
 service_config_test.go | 17 +++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/service_config.go b/service_config.go
index d0787f1e2a1c..686ad7ba6160 100644
--- a/service_config.go
+++ b/service_config.go
@@ -310,6 +310,14 @@ func parseServiceConfig(js string) (*ServiceConfig, error) {
 			}
 			break
 		}
+		if sc.lbConfig == nil {
+			// We had a loadBalancingConfig field but did not encounter a
+			// supported policy.  The config is considered invalid in this
+			// case.
+			err := fmt.Errorf("invalid loadBalancingConfig: no supported policies found")
+			grpclog.Warningf(err.Error())
+			return nil, err
+		}
 	}
 
 	if rsc.MethodConfig == nil {
diff --git a/service_config_test.go b/service_config_test.go
index 754374bfcc6a..e01e46169f42 100644
--- a/service_config_test.go
+++ b/service_config_test.go
@@ -92,6 +92,23 @@ func (s) TestParseLBConfig(t *testing.T) {
 	runParseTests(t, testcases)
 }
 
+func (s) TestParseNoLBConfigSupported(t *testing.T) {
+	// We have a loadBalancingConfig field but will not encounter a supported
+	// policy.  The config will be considered invalid in this case.
+	testcases := []parseTestCase{
+		{
+			scjs: `{
+    "loadBalancingConfig": [{"not_a_balancer1": {} }, {"not_a_balancer2": {}}]
+}`,
+			wantErr: true,
+		}, {
+			scjs:    `{"loadBalancingConfig": []}`,
+			wantErr: true,
+		},
+	}
+	runParseTests(t, testcases)
+}
+
 func (s) TestParseLoadBalancer(t *testing.T) {
 	testcases := []parseTestCase{
 		{