bhyve: allow specifiying tty by fd

[Peter Grehan]

Hi Roman,

>>> bhyve <snip>  -s 31,lpc -l com1,fd=19 vm0
>>
>>    Yes, useful idea, and will become more relevant in the capsicum world
>> of passing fd's to a sandboxed bhyve.
>>
>>    Thanks: I'll get this submitted.
>
> Hi Peter!
>
> Any news on that?

  I started to do it, and then hesitated bit for two reasons. First, 
it's useful for all backends, but there still needs to be a type - file 
descriptors can't be treated as something opaque: there still needs to 
be knowledge of whether it's a socket, char device, file etc, so the 
option may need additional information to describe that.

  Also, given that Capsicum wants to pass fd's as parameters, I was 
wondering if there is a general syntax style for doing this. "fd=%d" 
seems Ok, though it would be useful if there was something in libutil to 
parse an option like this if it is the preferred way forward for FreeBSD 
executables.

  What do folk think ? Any useful precedents ?

later,

Peter.