Allow the use of vmnet as an unprivileged user

[stevenjm]

Hi there!

I have a patch that I've been using on my own laptop for a few days to allow the use of vmnet as an unprivileged user. It works by opening the vmnet interface early and then dropping privileges if it detects that it is running setuid. chmod u+s on the hyperkit binary is then sufficient to allow unprivileged use of vmnet.

There are obviously security concerns with making the hyperkit binary setuid. As far as I can tell, the worst thing a user should be able to do is create a VM with the same UUID that another user wants to use so that a vmnet interface is created with the same MAC address, blocking the creation of the other user's VM. I'm not sure if this is worth worrying about or not.

I'll be opening a pull request with my proposed implementation of this momentarily.