Add Istio LICENSE
diff --git a/LICENSE b/LICENSE
index 4702175..b2d3628 100644
--- a/LICENSE
+++ b/LICENSE
@@ -280,3 +280,10 @@
of the input file used when generating it. This code is not
standalone and requires a support library to be linked with it. This
support library is itself covered by the above license.
+
+For the ca.proto in dubbo-registry-xds:
+
+This product contains a modified portion of 'Istio', an open platform to connect, manage, and secure microservices also
+ under a "Apache License 2.0" license, see https://github.com/istio/api/blob/master/LICENSE:
+
+ * security/v1alpha1/ca.proto
