[Bug 1776228] Re: Duplicate default routes on VMs with multiple NICs

[Steve Langasek]

A possible SRU regression has been reported against netplan.io
0.96-0ubuntu0.18.10.2 in LP: #1825206.  This version has been rolled
back to -proposed while the investigation is ongoing.

** Changed in: netplan.io (Ubuntu Cosmic)
       Status: Fix Released => Fix Committed

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to netplan.io in Ubuntu.
Matching subscriptions: foundations-bugs
https://bugs.launchpad.net/bugs/1776228

Title:
  Duplicate default routes on VMs with multiple NICs

Status in netplan:
  Fix Released
Status in netplan.io package in Ubuntu:
  Fix Released
Status in netplan.io source package in Bionic:
  Fix Committed
Status in netplan.io source package in Cosmic:
  Fix Committed

Bug description:
  [Impact]
  DHCP configurations where custom settings (routes) need to be applied. This is a subset of the changes presented in bug 1759014.

  [Test case]
  1) Configure netplan for the particulars of the network by configuring an appropriate dhcp{4,6}-override stanza:

  network:
    version: 2
    ethernets:
      engreen:
        dhcp4: true
        dhcp4-overrides:
          use-routes: false
          route-metric: 3333

  Additionally, if so required, add a custom routes to the
  configuration. e.g.

        routes:
          - to: 10.0.0.0/16
            via: 13.4.55.78

  (See https://netplan.io/reference#dhcp-overrides for the available
  options)

  2) Run 'netplan apply' or reboot to have the configuration applied.
  3) Validate that the routes / DNS are properly ignored and/or replaced by the defined values.

  [Regression potential]
  Minimal; this adds new values to the configuration generated for networkd or NetworkManager. Existing configurations will remain unchanged, but new configurations using the dhcp{4,6}-overrides fields will benefit from additional flexibility.

  ---

  I'm facing issues with OpenStack VMs built from Ubuntu 18.04 cloud
  image and configured with multiple NICs. I have a solution working on
  16.04, which doesn't do any more since the introduction of netplan.

  Requirements:

   - Multiple interfaces connected to different networks.
   - All NICs configured via DHCP to ensure IP address, but also parameters like MTU adapt to the environment automatically.
   - Default route is supposed to use one specific NIC and network.

  The solution on 16.04 was customization of /etc/dhcp/dhclient.conf,
  such that all unique parameters are retrieved from only that
  interface. Example with ens3 being the intended authoritative
  interface:

    option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
    send host-name = gethostname();
    request subnet-mask, broadcast-address, time-offset,
            netbios-name-servers, netbios-scope, interface-mtu,
            rfc3442-classless-static-routes;
    interface "ens3" { request routers, domain-name, domain-name-servers, domain-search, host-name,
                       dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers, ntp-servers; }

  This does no longer work with netplan. I couldn't figure any netplan
  properties to configure DHCP client to that granularity. And
  /etc/dhcp/dhclient.conf no longer seems to be honored. As I can see in
  VM startup console log, each interface is getting default route
  assigned and the system remains unresponsive most of the times.

  How am I supposed to solve this on a netplan managed system?

To manage notifications about this bug go to:
https://bugs.launchpad.net/netplan/+bug/1776228/+subscriptions