Add FreeBSD as a platform

[dfr]

This uses FreeBSD jails to implement container isolation.

[AkihiroSuda]

Cc @samuelkarp

[tianon]

A few initial (high level) thoughts 👍❤️

[dfr]

Fixed the type of FreeBSDDevice.Mode and fixed a typo in the json mapping for FreeBSDJail.SysVShm.

[dfr]

I took another pass over this today and made a couple of minor changes. I think the only current open question is whether the Mapping from jail(8) config file section is useful or whether it should be removed.

Does anyone else have comments or suggestions for the FreeBSD runtime extension? What should our next steps be to make this acceptable for the runtime spec?

[alice-sowerby]

@dfr we attended the developer meeting but it was Juneteenth and the attendance was relatively low. They suggested that you ping Tianon and Sam to ask for them to review it. If that doesn't work, we can try to attend the dev call again.

[giuseppe]

I've no specific comments on the FreeBSD part, but I can help to move this forward.

I've left an inline comment

[dfr]

I've no specific comments on the FreeBSD part, but I can help to move this forward.

I've left an inline comment

Thanks! I will check out your comment on the PR but my internet connection is flaky at the moment which is slowing me down a bit (hopefully that will be fixed over the weekend).

[tianon]

This looks pretty decent to me, although admittedly I'm not super familiar with FreeBSD / jails internals.

If we're not in a hurry to merge, I'd love to wait until @samuelkarp has a chance to review too, but if we've got something urgent that needs this, I think it's probably in a reasonable state (and hopefully he doesn't disagree).

[dfr]

This looks pretty decent to me, although admittedly I'm not super familiar with FreeBSD / jails internals.

If we're not in a hurry to merge, I'd love to wait until @samuelkarp has a chance to review too, but if we've got something urgent that needs this, I think it's probably in a reasonable state (and hopefully he doesn't disagree).

It looks like Sam is going to be away for a while focusing on family matters and he is unlikely to be able to give feedback in the near future. He was involved in the working group which led to this pull request and was a key reviewer during that process if that helps. As far as I know, he has not read through the exact text from this pull request.

Timing wise, I am not in a great hurry. It would be great if it makes it into the 1.3.0 release if at all possible.

[samuelkarp]

A couple minor comments, but generally this LGTM. I may not be available to review again after my suggestions are addressed, so please consider this to be my approval either way.