webdm failed to start / Failed to listen 224.0.0.251:5353

[Simon Eisenmann]

When booting into my Snappy image, suddenly webdm fails to start when no network cable is connected.

(ODROIDC)root@odroid:~# systemctl status -l webdm_snappyd_0.9
● webdm_snappyd_0.9.service - Snappy WebDM
   Loaded: loaded (/etc/systemd/system/webdm_snappyd_0.9.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Thu 2015-06-18 21:41:17 UTC; 9min ago
  Process: 726 ExecStart=/usr/bin/ubuntu-core-launcher webdm webdm_snappyd_0.9 /apps/webdm/0.9/snappyd (code=exited, status=1/FAILURE)
 Main PID: 726 (code=exited, status=1/FAILURE)

Jun 18 21:41:17 odroid systemd[1]: Started Snappy WebDM.
Jun 18 21:41:17 odroid systemd[1]: Starting Snappy WebDM...
Jun 18 21:41:17 odroid ubuntu-core-launcher[726]: 2015/06/18 21:41:17 Failed to listen 224.0.0.251:5353: listen udp4 224.0.0.251: setsockopt: no such device
Jun 18 21:41:17 odroid systemd[1]: webdm_snappyd_0.9.service: main process exited, code=exited, status=1/FAILURE
Jun 18 21:41:17 odroid systemd[1]: Unit webdm_snappyd_0.9.service entered failed state.
Jun 18 21:41:17 odroid systemd[1]: webdm_snappyd_0.9.service failed.

When booting with network cable connected it works just fine:

● webdm_snappyd_0.9.service - Snappy WebDM
   Loaded: loaded (/etc/systemd/system/webdm_snappyd_0.9.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2015-06-18 21:52:42 UTC; 25s ago
 Main PID: 772 (snappyd)
   CGroup: /system.slice/webdm_snappyd_0.9.service
           └─772 /apps/webdm/0.9/bin/arm-linux-gnueabihf/snappyd

Jun 18 21:52:42 odroid systemd[1]: Started Snappy WebDM.
Jun 18 21:52:42 odroid systemd[1]: Starting Snappy WebDM...
Jun 18 21:52:42 odroid ubuntu-core-launcher[772]: Snappy: 2015/06/18 21:52:42 handlers.go:52: Initializing HTTP handlers...
Jun 18 21:52:42 odroid ubuntu-core-launcher[772]: Snappy: 2015/06/18 21:52:42 snappyd.go:41: Snappy starting...
Jun 18 21:52:42 odroid ubuntu-core-launcher[772]: Snappy: 2015/06/18 21:52:42 avahi.go:50: Publishing odroid.local. 60 IN A 192.168.1.87
Jun 18 21:52:42 odroid ubuntu-core-launcher[772]: Snappy: 2015/06/18 21:52:42 avahi.go:50: Publishing odroid.local. 60 IN A ::1
Jun 18 21:52:42 odroid ubuntu-core-launcher[772]: Snappy: 2015/06/18 21:52:42 avahi.go:50: Publishing odroid.local. 60 IN A fe80::21e:6ff:fecf:adb1

Details of installation:
(ODROIDC)root@odroid:~# snappy info
release: ubuntu-core/15.04/stable
architecture: armhf
frameworks: docker, webdm
apps:

(ODROIDC)root@odroid:~# snappy list
Name Date Version Developer
ubuntu-core 2015-06-11 3 ubuntu
docker 2015-06-15 1.6.1.002
webdm 2015-06-15 0.9
odroidc 2015-06-15 0.2

[John Lenton (chipaca)]

So, the conceptually easiest way to fix this would be to have webdm setsockopt IP_FREEBIND. Sadly that implies reimplementing nearly all of net/ as well as patching the mdns library we use, so probably not a good idea.

[Oliver Grawert (ogra)]

i wouldn't call it a bug if a service that has a hard requirement for network doesn't start when no network is available at all (in fact i'd even call this a feature since it won't uselessly occupy resources)

indeed it should gracefully stop and indeed it should start dynamically along with the network as soon as a cable is attached though.