[GRPC] Add accessUnixDomainSocket permission for transport-grpc

CHANGELOG.md

@@ -17,6 +17,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Adding BackWardCompatibility test for remote publication enabled cluster ([#20221](https://github.com/opensearch-project/OpenSearch/pull/20221))
 - Support for hll field mapper to support cardinality rollups ([#20129](https://github.com/opensearch-project/OpenSearch/pull/20129))
 - Introduce new libs/netty4 module to share common implementation between netty-based plugins and modules (transport-netty4, transport-reactor-netty4) ([#20447](https://github.com/opensearch-project/OpenSearch/pull/20447))
+- Add security policy to allow deleting temporary socket files in `java.io.tmpdir` in `transport-grpc` module ([#20463](https://github.com/opensearch-project/OpenSearch/pull/20463))
 
 ### Changed
 - Handle custom metadata files in subdirectory-store ([#20157](https://github.com/opensearch-project/OpenSearch/pull/20157))

modules/transport-grpc/src/main/plugin-metadata/plugin-security.policy

@@ -15,4 +15,7 @@ grant codeBase "${codebase.grpc-netty-shaded}" {
 
    // Netty sets custom classloader for some of its internal threads
    permission java.lang.RuntimePermission "*", "setContextClassLoader";
+
+   // Netty on Windows uses WEPollSelectorImpl which needs to delete temporary socket files
+   permission java.io.FilePermission "${java.io.tmpdir}${/}socket_*", "delete";
 };