[Bug 1917552] [NEW] User-defined routing tables not created for loopback interface

[Nicholas Schell]

Public bug reported:

Ubuntu: 20.04.2 LTS
netplan.io: 0.101-0ubuntu3~20.04.2

Attempting to use the following config:

network:
    version: 2
    ethernets:
        loop0:
            match:
                name: lo
            routes:
                - to: 0.0.0.0/0
                  via: 127.0.0.1
                  table: 99
            routing-policy:
                - to: 0.0.0.0/0
                  mark: 7
                  table: 99

Will create the rule, but not table 99.

root at ubuntu-focal:~# ip rule list
0:	from all lookup local
0:	from all fwmark 0x7 lookup 99
32766:	from all lookup main
32767:	from all lookup default

root at ubuntu-focal:~# ip route show table 99
--- no output ----

However using the same config on Ubuntu 18.04 is working.
Ubuntu: 18.04.5 LTS
netplan.io: 0.99-0ubuntu3~18.04.4

root at ubuntu-bionic:~# ip route show table 99
default via 127.0.0.1 dev lo proto static

The generated configs in /run/systemd/network/ is the same on both
systems.

root at ubuntu-focal:~# cat /run/systemd/network/10-netplan-loop0.network 
[Match]
Name=lo

[Network]
LinkLocalAddressing=ipv6

[Route]
Destination=0.0.0.0/0
Gateway=127.0.0.1
Table=99

[RoutingPolicyRule]
To=0.0.0.0/0
Table=99
FirewallMark=7

This seems very similar to this report: https://bugs.launchpad.net/ubuntu/+source/netplan.io/+bug/1830641
Except that my config is working on Ubuntu 18.04, and I'm not dealing with any DHCP related routes since this is the loopback interface. Is there a new configure option or something I'm missing from a change in Ubuntu 20.04? Or some change to networkd possibly?

** Affects: netplan.io (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1917552

Title:
  User-defined routing tables not created for loopback interface

Status in netplan.io package in Ubuntu:
  New

Bug description:
  Ubuntu: 20.04.2 LTS
  netplan.io: 0.101-0ubuntu3~20.04.2

  Attempting to use the following config:

  network:
      version: 2
      ethernets:
          loop0:
              match:
                  name: lo
              routes:
                  - to: 0.0.0.0/0
                    via: 127.0.0.1
                    table: 99
              routing-policy:
                  - to: 0.0.0.0/0
                    mark: 7
                    table: 99

  Will create the rule, but not table 99.

  root at ubuntu-focal:~# ip rule list
  0:	from all lookup local
  0:	from all fwmark 0x7 lookup 99
  32766:	from all lookup main
  32767:	from all lookup default

  root at ubuntu-focal:~# ip route show table 99
  --- no output ----

  However using the same config on Ubuntu 18.04 is working.
  Ubuntu: 18.04.5 LTS
  netplan.io: 0.99-0ubuntu3~18.04.4

  root at ubuntu-bionic:~# ip route show table 99
  default via 127.0.0.1 dev lo proto static

  The generated configs in /run/systemd/network/ is the same on both
  systems.

  root at ubuntu-focal:~# cat /run/systemd/network/10-netplan-loop0.network 
  [Match]
  Name=lo

  [Network]
  LinkLocalAddressing=ipv6

  [Route]
  Destination=0.0.0.0/0
  Gateway=127.0.0.1
  Table=99

  [RoutingPolicyRule]
  To=0.0.0.0/0
  Table=99
  FirewallMark=7

  This seems very similar to this report: https://bugs.launchpad.net/ubuntu/+source/netplan.io/+bug/1830641
  Except that my config is working on Ubuntu 18.04, and I'm not dealing with any DHCP related routes since this is the loopback interface. Is there a new configure option or something I'm missing from a change in Ubuntu 20.04? Or some change to networkd possibly?

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