Possible to restart ES service during Remote Reindex?

Hello

I'm reindexing some from a remote cluster, but i had to whitelist some more ip's for our backends in elasticsearch.yml. However, it appears i cannot start reindex process until we restart ElasticSearch for our changes to be used. Can i restart my elasticsearch service safely? Will it stop the existing reindex process? it's only about 50% done and it's been a day. I don't want to lose progress.