allow creating macvlan network without subnet when using netavark backend

[craftyguy]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind feature

Description

podman (with netavark) should allow creating a mavlan network without specifying a subnet, for cases where the container is capable of managing its own IP assignment on the network (e.g. running its own dhcp client). Currently --subnet is required, or podman network create -d macvlan will error out.

Steps to reproduce the issue:

1. podman network create -d macvlan foo

2. error that --subnet is required

Describe the results you received:

Error: macvlan driver needs at least one subnet specified, DHCP is not supported with netavark

Describe the results you expected:

New macvlan network created with no IP management by podman

Additional information you deem important (e.g. issue happens only occasionally):

This was discussed briefly in chat with @Luap99. Also related: containers/netavark#152

Output of podman version:

❯ podman version
Client:       Podman Engine
Version:      4.0.2
API Version:  4.0.2
Go Version:   go1.17.7
Git Commit:   bddda48d70a98bb3d47ffe747ba2f84f340b4722
Built:        Wed Mar  2 18:56:21 2022
OS/Arch:      linux/amd64

Output of podman info --debug:

❯ podman info --debug
host:
  arch: amd64
  buildahVersion: 1.24.1
  cgroupControllers: []
  cgroupManager: cgroupfs
  cgroupVersion: v1
  conmon:
    package: conmon-2.1.0-r0
    path: /usr/bin/conmon
    version: 'conmon version 2.1.0, commit: feb71f1a6023ee6d874ed0a62a46a205a92f5dfc'
  cpus: 12
  distribution:
    distribution: alpine
    version: 3.15.0
  eventLogger: file
  hostname: librem14
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 5.15.26-0-lts
  linkmode: dynamic
  logDriver: k8s-file
  memFree: 10435219456
  memTotal: 33538834432
  networkBackend: netavark
  ociRuntime:
    name: crun
    package: crun-1.4.3-r0
    path: /usr/bin/crun
    version: |-
      crun version 1.4.3
      commit: 61c9600d1335127eba65632731e2d72bc3f0b9e8
      spec: 1.0.0
      +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +YAJL
  os: linux
  remoteSocket:
    path: /tmp/1000-runtime-dir/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    seccompProfilePath: /etc/containers/seccomp.json
    selinuxEnabled: false
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.1.12-r0
    version: |-
      slirp4netns version 1.1.12
      commit: 7a104a101aa3278a2152351a082a6df71f57c9a3
      libslirp: 4.6.1
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.2
  swapFree: 8374448128
  swapTotal: 8384409600
  uptime: 163h 30m 32.32s (Approximately 6.79 days)
plugins:
  log:
  - k8s-file
  - none
  - passthrough
  network:
  - bridge
  - macvlan
  volume:
  - local
registries:
  search:
  - docker.io
store:
  configFile: /home/clayton/.config/containers/storage.conf
  containerStore:
    number: 3
    paused: 0
    running: 1
    stopped: 2
  graphDriverName: overlay
  graphOptions: {}
  graphRoot: /home/clayton/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  imageCopyTmpDir: /var/tmp
  imageStore:
    number: 32
  runRoot: /tmp/1000-runtime-dir/containers
  volumePath: /home/clayton/.local/share/containers/storage/volumes
version:
  APIVersion: 4.0.2
  Built: 1646276181
  BuiltTime: Wed Mar  2 18:56:21 2022
  GitCommit: bddda48d70a98bb3d47ffe747ba2f84f340b4722
  GoVersion: go1.17.7
  OsArch: linux/amd64
  Version: 4.0.2

Package info (e.g. output of rpm -q podman or apt list podman):

podman
podman-openrc
podman-zsh-completion

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/main/troubleshooting.md)

(Yes)/No

Additional environment details (AWS, VirtualBox, physical, etc.):

Alpine Linux Edge

[mheon]

@baude This is DHCP support, I believe?

[Luap99]

Yes we discussed that on IRC.
Short term I want to add --ipam-driver none option which would only add interfaces and no ip addresses.
That would also help me to fix #13124 and #12990

[craftyguy]

@mheon ya this is closer to what @Luap99 mentioned, supporting DHCP would be nice, but it sounds like it might be difficult. In reality, I just need a way to create interfaces with macvlan and have the container manage IP assignment. Currently I have to specify --subnet or else the net create will fail.