Add new integration test for invalid client api version.

Signed-off-by: James Blair <mail@jamesblair.net>

tests/integration/clientv3/kv_test.go

@@ -27,6 +27,7 @@ import (
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/status"
 
 	"go.etcd.io/etcd/api/v3/mvccpb"
@@ -896,3 +897,25 @@ func TestBalancerSupportLearner(t *testing.T) {
 		t.Errorf("expect no error (balancer should retry when request to learner fails), got error: %v", err)
 	}
 }
+
+func TestInvalidUTF8ClientVersionOverwrite(t *testing.T) {
+
+	// Initialize integration test framework
+	integration2.BeforeTest(t)
+
+	// Create a new single node cluster
+	clus := integration2.NewCluster(t, &integration2.ClusterConfig{Size: 1})
+	defer clus.Terminate(t)
+
+	// Create a client request with an invalid client api version
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	ctx = metadata.NewIncomingContext(ctx, metadata.New(map[string]string{rpctypes.MetadataClientAPIVersionKey: "hello\xff\xfe\xfdworld"}))
+	resp, err := clus.Members[0].Client.Put(ctx, "/foo", "bar")
+
+	// We should see no error because downstream call stack for clientv3
+	// should overwrite the invalid version created here.
+	if err != nil {
+		t.Errorf("Expected no error (clienv3 should be overwriting invalid clientapiversion): %v", err)
+	}
+}