[libvirt] [PATCH v2 1/4] Add virDomainSendProcessSignal API

[Eric Blake]

> > Add an API for sending signals to arbitrary processes in the
> > guest OS. This is primarily useful for container based virt,
> > but can be used for machine virt too, if there is a suitable
> > guest agent,
> > 

> > +
> > +    if (signum > VIR_DOMAIN_PROCESS_SIGNAL_LAST) {
> > +        virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
> > +        goto error;
> > +    }
> 
> Drop this hunk (rather, move it to patch 4/4).  Such a check
> should be done in the hypervisor driver, not in the entry
> point.  Otherwise, if we add a new signal later, this hunk
> would prevent an older virsh from sending the new signal.

On the other hand, you _should_ add a check here that prevents
signum==0, since we have documented that signum must be non-zero
as part of the API contract.