We are developing an iOS app and are using Firebase's Auth module. During IPv6 network testing, we found that the app fails when calling Apple's login authorization in an IPv6 environment.
After investigation, we confirmed that the following two API calls:
https://gateway.icloud.com.cn:443/ckdatabase/api/client/record/save https://gsa.apple.com/grandslam/GsService2 remain in a pending state.
We tested gateway.icloud.com.cn and gsa.apple.com and found that these two domains do not support IPv6 DNS.
What we would like to understand is whether these two domains truly do not support IPv6 DNS, and how we can implement Apple's login authorization in an IPv6 environment.