My last release of application which is 12.8 is rejected by apple saying that i have to add the IPv6 support to the app, I read and reviewed the recommended apple doc named Supporting IPv6 DNS64/NAT64 Networks thoroughly and came to know that already i am using the NSURLConnection class for network connectivity which is mentioned in the same doc, you can see the image from doc under section "Ensuring IPv6 DNS64/NAT64 Compatibility" mentioning the name of NSURLConnection class as a one of recommended class, below is that image 
See the Recommended column in above image,
I thought something might be wrong. So, I did the set up of "local IPv6 Wi-Fi network on our Mac" as per the suggestion in the same apple doc under section *"Test for IPv6 DNS64/NAT64 Compatibility Regularly" and I wondered that the app is working like a charm without any issue or warning in debugger related to network connectivity.
I want some suggestions and recommendations from you related to same issue that is i am missing something to add support to IPv6 network connectivity. I have googled around for same thing and found the solutions whatever i have already tested, but still why apple rejected the app that i need to fix. Any help will be highly appreciated.
Note:
Also not able to get one thing that this is the version 12.8 the app is on app store from last 3 years till the day apple never asked or raised the bug for adding support to IPv6.
Don't believe everything that a reviewer says. You might think that I'm, pardon me for my language, bull-shiting. I am not. They use an iPad to test an app unless it doesn't support such. I got two of my iPhone & iPad apps rejected for the exactly same reason. In the end, they were wrong. One app which keeps track of subway train arrivals connecting a remote server got rejected at the beginning of last Jan. for that reason. But they tested the app at 4 AM according to a screenshot they showed me. No subway is running at that time in my country. The app was working as expected. When I said that to the reviwer through the resolution board, he approved it in a matter of minutes. The other app, which uses the device camera, got rejected for the same reason some 10 days ago. But it doesn't even get on the Internet in the first place. So I was very suspicous. And I appealed. After talking to an appeal board person, it turned out that the app crashed on the iPad because of its support of the camera flash, which the iPad doesn't have.
So what should you do? Talk to the reviewer and ask for more information. So let me say again. Don't believe everything they say when they mention IPv6.
Sometimes apple is really behaves like strange, Nothing was there related to IPv6 support already as i have mentioned in question the network connectivity framework i used "NSURLConnection" supports the IPv6, Still why/how the reviewer raised that issue dont know, It wasted my lot of time, Yesterday i push the app to app store and today it is approved,
Whatever @EI Tomato told was right.
Happy Coding to all!!
I too got faced the same issue. I replied the review team to test the app build again and to provide me crash logs.
And withing a day, my app is approved for distribution.
So if anyone facing the same issue, make sure you test your app against IPv6 WiFi hotspot (Apple source).
If it worked with that environment, reply app review team to review again as it worked with the suggested environment. Most probably your app will get approved after that :)
Hope it might help someone. Upvote if it answered your issue. :)
Thanks to @El Tomato.
TL;DR
[Rejection reason from Apple for my case]
Guideline 2.1 - Performance - App Completeness
We discovered one or more bugs in your app when reviewed on iPad running iOS 11.2 on Wi-Fi connected to an IPv6 network.
Specifically, your app was unresponsive upon launch.
Please see attached screenshots for details.
[My reply to them]
The app (Binary (0.0.xxxxx)) is working fine in our iPad and iPhone running iOS 11.2.1.
... MY DETAILED EXPLANATION ON HOW I TESTED THE APP ...
Can you please review again with the Binary (0.0.xxxxx)?
Is it possible for us to get the crash log, if any?
来源：https://stackoverflow.com/questions/42554285/application-rejected-with-the-reason-of-lack-of-ipv6-support