Store both IPv4 and IPv6 addresses for Docker services

[agibson-bluecat]

Our team runs several docker containers as nomad tasks (registered as services with Consul), and we need access to the containers' IPv4 and IPv6 addresses in a consul template. We use Docker bridge networking for our containers, and have the following daemon.json settings to enable IPv6 networking for containers:

{
  "ipv6" : true,
  "fixed-cidr-v6": "fd00::/80"
}

We've noticed that the addresses registered for these services in Consul are either only IPv4, or only IPv6 (if we set advertise_ipv6_address in the task configuration):

• when I curl Consul's /v1/agent/services endpoint, I see that if advertise_ipv6_address is enabled for the service then the Address field is the container's IPv6 address and the only automatically-populated tagged addresses are lan_ipv6 and wan_ipv6
• otherwise the Address is the container's IPv4 address and we only get lan_ipv4 and wan_ipv4

Because Consul only ever stores either the IPv4 or IPv6 address, it seems like there is no way to get access to both addresses by pulling fields out of the service object in our templates. Would the Consul team be open to auto-populating both the _ipv4 and _ipv6 tagged addresses for docker container services, if the container has both types of addresses?

[enspritz]

We need this too! Hoping this will be scheduled for release --