[PATCH v3] udhcpc(6): add -K option to set kernel packet priority

[Pacien TRAN-GIRARD]

Quoting Clément Péron (2023-04-13 13:13:41)
> > +#if ENABLE_FEATURE_UDHCPC_SK_PRIO
> > +       if (setsockopt_SOL_SOCKET_int(fd, SO_PRIORITY, sk_prio) < 0) {
> 
> One difference is that it will call setsockopt even when sk_prio is
> not set and default to '0'.
> 
> I don't know if this can have an impact, or maybe we should default
> sk_prio to -1 and only call setsockopt_SOL_SOCKET_int() when it's >= 0

I omitted the check here since the default kernel packet priority is 0,
so setting it again to 0 by default should not do any harm.