[Bug 1736975] Re: netplan does not bring up anonymous bridge on boot

[Mathieu Trudel-Lapierre]

Won't Fix for nplan: we will not be backporting these fixes to releases
prior to 18.04.

** Changed in: nplan (Ubuntu)
       Status: Triaged => Won't Fix

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https://bugs.launchpad.net/bugs/1736975

Title:
  netplan does not bring up anonymous bridge on boot

Status in netplan:
  Fix Released
Status in netplan.io package in Ubuntu:
  Fix Released
Status in nplan package in Ubuntu:
  Won't Fix
Status in netplan.io source package in Bionic:
  Fix Released

Bug description:
  [Impact]
  Netplan users setting up bridges.

  [Test cases]
  1) Add a new bridge configuration in netplan yaml, without an IP address set:

    [...]
    bridges:
      br0:
        interfaces: [  interface   ]
        dhcp4: false
        parameters:
          stp: false
          forward-delay: 0

  [Regression potential]
  Possible regression scenarios might be for a configured bridge not to come up / not be created or added by systemd-networkd when the network is configured; or for a bridge to be configured with addresses that should not be present (ie. dhcp when it is not enabled, or link-local address when not configured).

  ---

  Configuring "/etc/netplan/01-netcfg.yaml" with an anonymous bridge
  seems to require running "ip link set dev br0 up" to bring the bridge
  up after boot. A bridge configured with an IP address is automatically
  up after boot.

  This is only a problem if you want an anonymous bridge which comes up
  automatically after boot. For example, if you preferred to isolate
  host traffic from your autostarting virtual machine traffic.

  Configuration that results in the bridge being down after boot:
  network:
    version: 2
    renderer: networkd
    ethernets:
      enp22s2:
        dhcp4: yes
      enp22s3:
        dhcp4: no
    bridges:
      br0:
        interfaces: [enp22s3]
        dhcp4: false
        parameters:
          stp: false
          forward-delay: 0

  Enabling DHCP results in a bridge that is automatically up after boot:
  network:
    version: 2
    renderer: networkd
    ethernets:
      enp22s2:
        dhcp4: yes
      enp22s3:
        dhcp4: no
    bridges:
      br0:
        interfaces: [enp22s3]
        dhcp4: true
        parameters:
          stp: false
          forward-delay: 0

  Setting a static IP address results in a bridge that is automatically up after boot:
  network:
    version: 2
    renderer: networkd
    ethernets:
      enp22s2:
        dhcp4: yes
      enp22s3:
        dhcp4: no
    bridges:
      br0:
        interfaces: [enp22s3]
        dhcp4: false
        addresses: [192.168.1.100/24]
        parameters:
          stp: false
          forward-delay: 0

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: nplan 0.30
  ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8
  Uname: Linux 4.13.0-17-generic x86_64
  ApportVersion: 2.20.7-0ubuntu3.5
  Architecture: amd64
  Date: Thu Dec  7 11:06:25 2017
  ProcEnviron:
   LANGUAGE=en_CA:en
   TERM=screen
   PATH=(custom, no user)
   LANG=en_CA.UTF-8
   SHELL=/bin/bash
  SourcePackage: nplan
  UpgradeStatus: No upgrade log present (probably fresh install)

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