People are also building compilers for P4 that are targeting other runtimes like BPF. Recently, there's been an effort to run a subset of BPF on hardware (NPF?).
As for "unfortunately", what don't you like about it, apart from it not being what you're used to from elsewhere? I've used Visual Sourcesafe, Perforce and git, and Perforce seems like a perfectly decent source control system.
However, I won't deny that it would be nice to be able to manage multiple revisions locally so that I can explore different approaches and easily backtrack without having to commit to the central server.
I don't think be able to build a full p4 implementation with Snabb running as a substrate (although it's been 6 months since I last worked on it, and am blanking at the moment why not), but I think it could get pretty close. But it will be a ton of work if I get around to it, plus I don't have much experience doing networking programming at this low of a level. I got a bit distracted with work and other obligations, but I hope to pick it back up soon, particularly if p4 is finally starting to get some well-deserved attention.
p4 is an awesome idea, and solves a lot of the problems OpenFlow was running into with having to constantly update the spec for new network protocols. With p4, that's just a software update, not a protocol update. It has some other neat features as well, but unfortunately it doesn't seem as though p4 has yet caught on like OpenFlow did, even though it has many of the same people behind it as OpenFlow.
Some of the cool things that people have done with p4:
To get a taste of what is P4 like, you can get started with the Behavioural Model [1], which you can imagine as some sort of emulator over x86. My understanding is that it is also being reworked in C++ [2].
Finally, there's a module coming up for OpenVSwitch.
is this project linux only?
Does FreeBSD nowadays provide some form of network isolation like it is available with Linux network namespaces? Nothing relevant shows up in the likely places, so I don't think it does.