Hi, Thanks for the suggestion, I think that's resonable and I modify my app code to follow the guideline. Actually I do find some issue because my quirks sometimes find a stale ifindex due to previous utun interface seems does not cleanup, in iOS 18 its quite easy to get the correct index, below iOS 18 I have to fix the logic to make it's more stable...

Thanks a lot for the msg, I was noticed virtualInterface property, but sadyly found it's only avalable on iOS 18+, may be in the future we'd better migrate to use this for reliably get the bsd interface and index.

Yes, mess around with UTUN interface is hard but joyful:) Here is the answers for the question, the platform is iOS, it's a packet tunnel provider. Will also consider to release a macOS app later if we have more time.

sorry for the post, it seems in some case my code can't correct find the utun ifindex, this plan actually works.