I was trying to test some software that supports IPv6 and I was disappointed to discover that my test was failing in Travis.
After Googling, I found that a number of the Travis build environments don't support IPv6 but I couldn't find some definitive answers.
The different types of build environment are listed here: https://docs.travis-ci.com/user/reference/overview/
You can see the results of the tests here: https://travis-ci.org/njh/travis-ipv6-test
My findings are summarised below.
First I checked if the network interfaces had IPv6 addresses allocated:
| Build Environment | IPv6 Loopback | IPv6 Link Local | IPv6 Global |
|---|---|---|---|
| Trusty VM (sudo: required) | No | No | No |
| Trusty Container (sudo: false) | Yes | Yes | No |
| Precise VM (sudo: required) | No | No | No |
| Precise Container (sudo: false) | Yes | Yes | No |
| Mac OS X | Yes | Yes | No |
Binding a web server to IPv6 localhost works for containers (sudo: false) and Mac OS X.
It fails for the Linux VMs (sudo: required).
Sending a UDP packet to IPv6 localhost works for containers (sudo: false) and Mac OS X.
It fails for the Linux VMs (sudo: required).