What challenge are you facing?

(If I've missed a configuration setting, I apologize - I think this is a feature request, but might just be a documentation clarification.)

Some of the jobs we run make connections to ipv6-only addresses, and currently fail because (I believe) ipv6 support is not enabled when concourse configures garden (which wraps guardian's runc). The hosts we run concourse on are ipv6 enabled.

There was some support for ipv6 loopback in guardian added in cloudfoundry/guardian#79, and then made more extensible with cloudfoundry/guardian#100.

A Modest Proposal

I believe we could configure AdditionalHostEntries in the garden config to contain at least the loopback. I don't fully understand how garden is configured for its current ipv4 networking, but would appreciate a few pointers and then would like to submit a PR adding support for ipv6 configuration.