Subject: bug#68595: VLANs in static-networking-service-type hangs shepherd

From: Lars Rustand <[email-masked]>
Date: Fri, 19 Jan 2024 20:12:24 +0100

Like the title says, if you add any VLAN in a
static-networking-service-type it seems like the whole shepherd daemon
freezes up and anything that depends on it stops responding.
Additionally the networking does not get fully configured either.

After configuring a VLAN `herd status`, `herd restart networking` and
any other herd command hangs forever with no output. Even reboot is not
working. The only remedy is to restart the system using the power
button, but even after the restart the networking service still fails to
start.

VLANs are seemingly created, but no addresses are created.

Steps to reproduce:

1. Add a static network with a VLAN to your system config (see below for
minimal example)
2. Reconfigure your system
3. Restart the networking service with `sudo herd restart networking`
4. Observe that herd does not finish
5. Try to run `herd status`, `guix system reconfigure`, or `sudo reboot`.
6. Observe that none of the commands seem to have any effect, and that
they hang indefinitely with no output

--8<---------------cut here---------------start------------->8---
(service static-networking-service-type
  (list (static-networking
         (links
          (list (network-link
                 (name "myvlan")
                 (type 'vlan)
                 (arguments '((id . 3)
                              (link . "eth0"))))))
         (addresses
          (list (network-address
                 (device "myvlan@eth0")
                 (value "192.168.0.2/24")))))))
--8<---------------cut here---------------end--------------->8---

Alternatively here are the reproduction steps using VM:

1. Build a qcow2 image, make sure there is enough space to reconfigure
   the system. Use --save-provenance so you have the config inside the
   vm so you can reconfigure later.
   `guix system image --image-type=qcow2 --image-size=30G --save-provenance minimal.scm`
2. Copy the qcow image to a writable directory.
3. Start up the vm.
```
sudo qemu-system-x86_64 \
   -nic user,model=virtio-net-pci \
   -enable-kvm -m 2048 \
   -device virtio-blk,drive=myhd \
   -drive
   if=none,file=1a7wi5mgcy3wrsx6pcnag6qjbb87djwl-image.qcow2,id=myhd
```
4. Edit /run/current-system/configuration.scm and uncomment the static
   networking.
5. Reconfigure the system.
6. Try to restart the networking service. `herd restart networking`
7. The command will hang infinitely. Cancel it.
8. Check the network interfaces. The VLAN interface will have been
   created, but it will not have any address.
9. The aforementioned commands will all be unresponsive now.
10. If you reboot your VM you will see that the networking service is
   failed at startup, and if you try to restart the service you will get
   an error: #<&netlink-response-error errno: 17>

--8<---------------cut here---------------start------------->8---
(use-modules
  (gnu)
  (gnu services)
  (gnu services base)
  (gnu services networking)
  (gnu bootloader)
  (gnu bootloader grub)
  (gnu system)
  (gnu system file-systems)
  (gnu system accounts))

(operating-system
  (host-name "minimal")

  (users
    (cons*
      (user-account
        (name "lars")
        (group "users"))
      %base-user-accounts))

  (services
   (cons*
          (service dhcp-client-service-type)
          ;; Commented out so you can uncomment it after booting the VM
          ;;(service static-networking-service-type
          ;;      (list (static-networking
          ;;             (links
          ;;              (list (network-link
          ;;                     (name "myvlan")
          ;;                     (type 'vlan)
          ;;                     (arguments '((id . 3)
          ;;                                  (link . "eth0"))))))
          ;;             (addresses
          ;;              (list (network-address
          ;;                     (device "myvlan@eth0")
          ;;                     (value "192.168.0.2/24")))))))
    %base-services))

   (bootloader
     (bootloader-configuration
       (bootloader grub-bootloader)
       (targets '("/dev/vda"))))

   (file-systems
    (cons*
     %base-file-systems)))
--8<---------------cut here---------------end--------------->8---