glib warning on netplan-try with wrong config

[Alex]

Hello! Not sure if it is a bug or not, but:
While learning netplan, I've made a wrong config, then check it with netplan-try, and get the error below.

(generate:1255): GLib-WARNING **: 07:45:34.289: GError set over the top of a previous GError or uninitialized memory.
This indicates a bug in someone's code. You must ensure an error is NULL before it's set.
The overwriting error message was: /etc/netplan/00-installer-config.yaml:13:14: Error in network definition: unicast route must include both a 'to' and 'via' IP
             - to: 0.0.0.0/0
             ^
/etc/netplan/00-installer-config.yaml:17:21: Error in network definition: IP family mismatch in route to fe80::1
               via: fe80::1
                    ^
An error occurred: the configuration could not be generated
Reverting.
Warning: Stopping systemd-networkd.service, but it can still be activated by:
  systemd-networkd.socket

My config is (addresses were replaced):

network:
    version: 2
    renderer: networkd
    ethernets:
        eth0:
            addresses:
                - 192.46.XXX.XXX/24
                - 2a01:7e01:e001:23e:152c:a51c:beef:beer/64
            nameservers:
                addresses: [8.8.8.8, 1.1.1.1]
            routes:
             - to: 0.0.0.0/0
               via: 192.XXX.XXX.1
               metric: 100
             - to: 0.0.0.0/0
               via: fe80::1
               metric: 200

[Alex (qw)]

Oh, sorry, I've forgot to add the system info:
VPC
Linux localhost 5.4.0-80-generic #90-Ubuntu SMP Fri Jul 9 22:49:44 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

libnetplan0/focal-updates,now 0.102-0ubuntu1~20.04.2 amd64 [installed,automatic]
netplan.io/focal-updates,now 0.102-0ubuntu1~20.04.2 amd64 [installed,automatic]

[Roman K (roman84)]

It is a bug in error reporting. This netplan configuration is still incorrect.

[Roman K (roman84)]

I was trying to follow https://netplan.io/examples/ but it looks like the "default" key word cannot be used.

Linux srv2 5.4.0-81-generic #91-Ubuntu SMP Thu Jul 15 19:09:17 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

(generate:3732): GLib-WARNING **: 19:34:50.050: GError set over the top of a previous GError or uninitialized memory.
This indicates a bug in someone's code. You must ensure an error is NULL before it's set.
The overwriting error message was: /etc/netplan/00-installer-config.yaml:18:11: Error in network definition: unicast route must include both a 'to' and 'via' IP
          - to: default
          ^
/etc/netplan/00-installer-config.yaml:18:17: Error in network definition: invalid IP family '-1'
          - to: default
                ^

[Lukas Märdian (slyon)]

netplan try is saving you from applying a wrong config, as Roman already mentioned.

When defining an IP6 default route, you need to specify the IP6 default IP, i.e. use "::/0" instead of "0.0.0.0/0". This way your config (and netplan try) should work.

With the release of netplan v0.103 the "default" keyword was introduced, which will adopt the default route to either "0.0.0.0/0" (for IP4 routes) or "::/0" (for IP6 routes), but that is not yet available in all versions of Ubuntu.

Additionally, indeed you spotted a minor flaw in error reporting here, that should be fixed at some point: "GError set over the top of a previous GError or uninitialized memory."

[Alex (qw)]

Lukas Märdian (slyon)

Additionally, indeed you spotted a minor flaw in error reporting here, that should be fixed at some point: "GError set over the top of a previous GError or uninitialized memory."

Sure, that was the one and only point of my report, the rest of netpaln-try output is correct. Thank you!