[ECS] [Service Discovery]: Add ability for reverse lookups

### Community Note

* Please vote on this issue by adding a 👍 [reaction](https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to the original issue to help the community and maintainers prioritize this request
* Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request
* If you are interested in working on this issue or have submitted a pull request, please leave a comment

We use Service Discovery within ECS so that one service can talk to another service within the same VPC. This works great!
However as the service receiving a request, I need to know who the origin service is and I need to do this in a secure way.
We could of course sign every request cryptographically but if we were able to reverse lookup the IP of the request sender, we could also retrieve the sending service through that a lot easier.

AWS support looked into this functionality and found that ECS Service discovery currently does not provide a feature to automatically configure reverse DNS records for the service tasks.

Please let me know if you have further questions about the use case.
Christoph

Start by reviewing the ECS Service Discovery behavior described in the issue and the AWS support finding about reverse DNS records for service tasks. Done means ECS can automatically configure reverse lookups so a receiving service can identify the originating service from its request IP.

Written by the indexing model from the issue text.