• backport: IPv6 only: add API option enable/disable IPv4 #48271

- What I did

• Added top level network-create option EnableIPv4 (which can later be hooked up to an option --ipv4 in the CLI, equivalent to --ipv6).
• Added equivalent driver option com.docker.network.enable_ipv4.
  • Like enable_ipv6, it can be set via default-network-opts.
• Show EnableIPv4 alongside EnableIPv6 in "inspect" output.
• Predefined Linux none/host and Windows null networks are created with EnableIPv4=false.
• Other networks, including predefined Linux bridge default to EnableIPv4=true.\
• Ignore (clear) EnableIPv4 in a network create request if the API version is less than 1.47.
• Require --experimental to disable IPv4.

Follow-up PRs will make the option do-something.

- How I did it

The first commit here, bumping the API version to 1.47, is likely to disappear - as this will be merged after another PR that does the same thing. But, for now, it means there's somewhere to put an API version-history.md update.

The rest is fairly machanical copying of EnableIPv6 behaviour.

- How to verify it

Can't disable IPv4 without --experimental:

# docker network create -o com.docker.network.enable_ipv4=false n1
Error response from daemon: IPv4 can only be disabled if experimental features are enabled

With --experimental, can disable IPv4:

# docker network create -o com.docker.network.enable_ipv4=false n1
e3fc95637aa2d9902ed188960283e025b95521cd44c95a645e0b48e7548ef2e6
# docker network inspect n1
[
    {
        "Name": "n1",
        ...
        "EnableIPv4": false,
        "EnableIPv6": false,

Default for a new bridge network is true:

# docker network create n2
9d71a90d0353fd352d53495fca214fa1a8ddecaca90c959a4ef9ed2318438d05
# docker network inspect n2
[
    {
        "Name": "n2",
        "Id": "9d71a90d0353fd352d53495fca214fa1a8ddecaca90c959a4ef9ed2318438d05",
        ...
        "EnableIPv4": true,
        "EnableIPv6": false,

Predefined host network shows EnableIPv4:false, like the existing EnableIPv6:false:

# docker network inspect host
[
    {
        "Name": "host",
        ...
        "EnableIPv4": false,
        "EnableIPv6": false,

Predefined bridge network has EnableIPv4:true:

# docker network inspect bridge
[
    {
        "Name": "bridge",
        ...
        "Driver": "bridge",
        "EnableIPv4": true,
        "EnableIPv6": false,
       ...

Marshalling/unmarshalling a libnetwork.Network with EnableIPv4:true is covered in an updated unit test.

- Description for the changelog

- API Changes:
  - `POST /networks/create` now has an `EnableIPv4` field. Setting it to `false`
  disables IPv4 IPAM for the network. It can only be set to `false` if the
  daemon has experimental features enabled.
  - `GET /networks/{id}` now returns an `EnableIPv4` field showing whether the
  network has IPv4 IPAM enabled.