Make selection of subnet using docker more flexible.

[Boomatang]

This removes the assumption that the first item in IPAM.Config is the IPv4 entry. However the assumption that only the IPv4 has a value for the gateway is being made.

[eguzki]

We had

## Parse kind network subnet
## Take only IPv4 subnets, exclude IPv6
SUBNET=$(docker network inspect $networkName --format '{{json .IPAM.Config }}' | \
    ${YQ} '.[] | select( .Subnet | test("^((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}/\d+$")) | .Subnet')
if [[ -z "$SUBNET" ]]; then
   echo "Error: parsing IPv4 network address for '$networkName' docker network"
   exit 1
fi

in the first place and it was changed on #517 when adding podman local setup. Maybe @david-martin has a good reason.

Maybe add it back?

[eguzki]

When I run

docker network inspect kind | yq e '.[] | select(.IPAM.Config[] | has("Gateway")) | .IPAM.Config[] | select(has("Gateway")) | .Subnet' -

I get

172.18.0.0/16
fc00:f853:ccd:e793::/64

When I run

docker network inspect kind --format '{{json .IPAM.Config }}' | \
    yq '.[] | select( .Subnet | test("^((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}/\d+$")) | .Subnet'

I get

172.18.0.0/16

[Boomatang]

I'll update this to include the regex. My assumption was there would be no gateway on the IPv6, which in my case was true. Gladly will fix.

[david-martin]

in the first place and it was changed on #517 when adding podman local setup. Maybe @david-martin has a good reason

The change landed on a working branch here before the changes landed back on main.
@jasonmadigan do you recall the reason for the change to the network inspect cmd? I think the suggested cmd came from the kind docs or metallb docs?

Either way, reverting the docker version of the cmd sounds reasonable if it fixes an issue and still gives the desired behaviour.

[jasonmadigan]

@jasonmadigan do you recall the reason for the change to the network inspect cmd? I think the suggested cmd came from the kind docs or metallb docs?

Either way, reverting the docker version of the cmd sounds reasonable if it fixes an issue and still gives the desired behaviour.

I don't recall, but this change/revert (with the regex) looks fine to me. No longer have docker so someone else should probably test.