Unity WebRequest does not work when only IPv6 is enabled

Unity: WebRequest

Backport

Fixed

2022.1.X

2021.3.X

2020.3.X

Fixed in 2022.1.9f1 and above

Fixed in 2021.3.6f1 and above

Fixed in 2020.3.36f1 and above

How to reproduce:
1. Disable IPv4 on your network adapter
2. Open the user attached "ipv6_2018.zip" project
3. Open the "SampleScene"
4. Enter Play Mode
5. Click the start downloading button

Expected result: there should be no error
Actual result: error in console that the WebRequest can not be completed successfully

Reproducible with: 2019.4.30f1
Not reproducible with: 2019.4.29f1

Note: I could not test the versions due to my phone not supporting IPv6

Unity WebRequest does not work when only IPv6 is enabled