GitLab.com: webhooks should work on IPv6
Summary
Webhooks don't work for IPv6-only receivers.
Steps to reproduce
Create a webhook with a URL that has a literal IPv6 address (e.g., http://[2001:db8::f]:8088/payload), or a DNS name that only has a AAAA record (e.g., http://ipv6.example.com:8088/payload). Test that webhook. GitLab gives error 500 and doesn't execute the webhook.
What is the current bug behavior?
GitLab gives error 500 and doesn't execute the webhook.
What is the expected correct behavior?
GitLab executes the webhook.
Output of checks
This bug happens on GitLab.com
Possible fixes
Host the webhook runner on an IPv6-capable host.