udev: when setting up lo, do not return an error

From #20300:
> commit 70f32a260b5ebb68c19ecadf5d69b3844896ba55
> Author: Yu Watanabe <watanabe.yu+github@gmail.com>
> Date:   Sun May 23 16:59:40 2021 +0900

>     udev/net: do not manage loopback interfaces

>     There are nothing we can configure in udevd for loopback interfaces;
>     no ethertool configs can be applied, MAC address, interface name should

> introduced a regression for 'udevadm test-builtin net_setup_link /sys/class/net/lo/'.
> Prior to this commit this command would exit with 0 whereas after this commit
> it exists with 1. This causes cloud-init on Archlinux to fail as this command
> is run by it and likely also netplan to have networkd rescan and re-apply a
> bunch of things on NICs.

I think it's reasonable to keep returning 0 here: we are intentatinally doing
nothing for the device, and that is not an error, but a (noop) success.

Fixes #20300.

diff --git a/src/udev/udev-builtin-net_setup_link.c b/src/udev/udev-builtin-net_setup_link.c
index d40251331ce85b109ff8b78445d3cee2d277d6fd..5964e30bf1ad6fc5f1a558f9e17bc6ce555c6004 100644 (file)
--- a/src/udev/udev-builtin-net_setup_link.c
+++ b/src/udev/udev-builtin-net_setup_link.c
@@ -28,10 +28,12 @@ static int builtin_net_setup_link(sd_device *dev, int argc, char **argv, bool te
 
         r = link_config_get(ctx, dev, &link);
         if (r < 0) {
-                if (r == -ENOENT)
-                        return log_device_debug_errno(dev, r, "No matching link configuration found.");
                 if (r == -ENODEV)
                         return log_device_debug_errno(dev, r, "Link vanished while searching for configuration for it.");
+                if (r == -ENOENT) {
+                        log_device_debug_errno(dev, r, "No matching link configuration found, ignoring device.");
+                        return 0;
+                }
 
                 return log_device_error_errno(dev, r, "Failed to get link config: %m");
         }