[LEDE-DEV] umdns fails to launch (seccom related)?

[Michal Sojka]

Hi Bryan,

On Fri, Nov 03 2017, Bryan Mayland wrote:
> I use a custom LEDE build as the basis for an open source project and
> noticed recently that the umdns daemon has stopped loading. This also
> occurs with the standard development snapshot with the umdns package
> installed.
> root at LEDE:~# /etc/init.d/umdns restart
> Command failed: Request timed out
>
> umdns never launches so the service_started() handler waits for the 10
> seconds for the ubus response then fails. If I comment out the
> `procd_set_param seccomp /etc/seccomp/umdns.json` line it works just
> fine. I've also tried replacing the umdns executable with a simple
> shell script and it never appears to execute. This occurs if the
> daemon is configured to be jailed or not.
>
> Because my bcm2708 target does not have CONFIG_KERNEL_SECCOMP enabled,
> this should not make a difference right? I've also tried adding a
> /sbin/seccomp-trace which was just a shell script as well to launch
> umdns and it had no effect.
>
> I believe it is a problem in procd but I'm not sure where else to look
> as this seems like it could affect anything with a seccomp procd init,
> and umdns is the only one that does this so far.

you're right, I'm aware of the problem. I already have a patch with the
fix. I need to do a few cleanups before posting it - I'll look at that
tonight.

-Michal