Unable to consume officially supported sysext extensions behind proxy

[markafarrell]

Description

I am unable to consume officially supported sysext extensions where flatcar is behind a proxy (i.e. does not have direct internet access)

Impact

This means I am unable to consume the official sysext extensions when my flatcar host does not have direct internet access

Environment and steps to reproduce

Using flatcar version 4054.0.0 on openstack

1. Enable zfs sysext extension by adding it to /etc/flatcar/enabled-sysext.conf using ignition.
2. Configure global proxy settings as per https://www.flatcar.org/docs/latest/setup/systemd/environment-variables/#system-wide-environment-variables
3. Create flatcar server
4. 

Expected behavior

Flatcar is able to download sysext extension image using proxy server

Additional information

I believe the sysext extensions are downloaded by https://github.com/flatcar/bootengine/blob/flatcar-master/dracut/99setup-root/initrd-setup-root-after-ignition#L136

[jepio]

As a workaround, I think initially fetching the sysext through ignition would allow to pass proxy information:

variant: flatcar
version: 1.0.0
storage:
  files:
  - path: /etc/flatcar/sysext/flatcar-zfs-4054.0.0.raw
    contents:
      source: https://alpha.release.flatcar-linux.net/amd64-usr/4054.0.0/flatcar-zfs.raw
    verification:
      hash:  sha512-76bf45a0c76063532b15af5ebc702a147c734e80e7d0392119f20d0a2ac3de4bfa19afb713389dcaa13e6a0ca0a445830ac9ce5fb01f8dde719d00422955e96a
  - path: /etc/flatcar/enabled-sysext.conf
    mode: 0600
    append:
    - inline: zfs

[markafarrell]

For reference the workaround ended up being:

---
variant: flatcar
version: 1.0.0
ignition:
  proxy:
    http_proxy: http://my-proxy:3128
    https_proxy: http://my-proxy:3128
kernel_arguments:
  should_exist:
  - ip=<my-host-ip>::<my-gateway-ip>:<my-netmask>::eth0:none:<my-dns-server>
storage:
  files:
  - contents:
      inline: |-
        zfs
        python
    mode: 384
    path: "/etc/flatcar/enabled-sysext.conf"
  - contents:
      source: https://alpha.release.flatcar-linux.net/amd64-usr/4054.0.0/flatcar-zfs.raw
      verification:
        hash: sha512-76bf45a0c76063532b15af5ebc702a147c734e80e7d0392119f20d0a2ac3de4bfa19afb713389dcaa13e6a0ca0a445830ac9ce5fb01f8dde719d00422955e96a
    path: "/etc/flatcar/sysext/flatcar-zfs-4054.0.0.raw"
  - contents:
      source: https://alpha.release.flatcar-linux.net/amd64-usr/4054.0.0/flatcar-python.raw
      verification:
        hash: sha512-37fe9b15ebf8d1106b2c384a40abaa621b9f42c82f4cb17ea413f8d96d0764a54eeea5b56840aad65176db392bf750b36740773b433ee8820806dd22bed58ace
    path: "/etc/flatcar/sysext/flatcar-python-4054.0.0.raw"