cap_sysctlbyname for hw.vmm.destroy

[Mark Johnston]

There are two bugs in the example, also present in your WIP.  I fixed
them here:
https://cgit.freebsd.org/src/commit/?id=44bbda649dc6c1cdc5a99641e14c77157967e140

On Wed, Apr 28, 2021 at 05:22:22PM +0300, Ionuț Mihalache wrote:
> I update the code now [1] but still the same error. Even without any limits
> the cap_sysctlbyname fails after using cap_enter.
> 
> [1] -
> https://github.com/FreeBSD-UPB/freebsd-src/blob/c54dce7590b065a757dff0f68fd921aca380670f/usr.sbin/bhyve/bhyverun.c#L1567
> 
> În mie., 28 apr. 2021 la 16:52, Mark Johnston <markj at freebsd.org> a scris:
> 
> > On Wed, Apr 28, 2021 at 02:30:26PM +0300, Ionuț Mihalache wrote:
> > > I tried to test the example from the documentation between here [1] and
> > > here [2]. The code stops here [3].
> >
> > I think you're referencing an old version of the cap_sysctl man page?
> > See the example from the copy in your repo:
> >
> > https://github.com/FreeBSD-UPB/freebsd-src/blob/3a08ffe4839de9b8396b1760f1dc42b066428807/lib/libcasper/services/cap_sysctl/cap_sysctl.3#L122
> > In particular, when setting limits consumers should not be building
> > nvlists directly.
> >
> > > [1] -
> > >
> > https://github.com/FreeBSD-UPB/freebsd-src/blob/3a08ffe4839de9b8396b1760f1dc42b066428807/usr.sbin/bhyve/bhyverun.c#L1538
> > > [2] -
> > >
> > https://github.com/FreeBSD-UPB/freebsd-src/blob/3a08ffe4839de9b8396b1760f1dc42b066428807/usr.sbin/bhyve/bhyverun.c#L1585
> > > [3] -
> > >
> > https://github.com/FreeBSD-UPB/freebsd-src/blob/3a08ffe4839de9b8396b1760f1dc42b066428807/usr.sbin/bhyve/bhyverun.c#L1581
> > >
> > > În lun., 26 apr. 2021 la 20:40, Mark Johnston <markj at freebsd.org> a
> > scris:
> > >
> > > > On Mon, Apr 26, 2021 at 05:16:14PM +0300, Ionuț Mihalache wrote:
> > > > > Hello,
> > > > >
> > > > > I am working on adding capsicum support for the bhyve snapshot
> > feature.
> > > > At
> > > > > the end of the suspend process, the guest should be destroyed and the
> > > > code
> > > > > handles this part with a sysctlbyname call which is not working in
> > > > > capability mode. I don't know what is the problem but even when using
> > > > > cap_sysctlbyname I still get the same error code (EPERM). I tried the
> > > > > example from the documentation aswell [1] and still the same error
> > code.
> > > > > What could be the problem? I have a FreeBSD13 host and a FreeBSD13
> > guest.
> > > >
> > > > I'm not sure why it would happen unless the casper process is somehow
> > > > running as a non-root user.  Can you share the code you're testing
> > > > somewhere?
> > > >
> >