[eric_bullington]

It's pretty cool. I built a lexer/parser for the p4 language in Lua, with the intention of then building a "runtime" for it out of the Snabb networking toolkit (amusingly, I also finished most of a p4 lexer/parser in Elixir before switching to Lua).

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:

https://2016p4workshop.sched.org/info

[superbaconman]

I'm hesitant to pick up another network protocol after OpenFlow. Lots of vendors claimed to support it, but only a handful took an honest shot at a decent implementation.

[eric_bullington]

Just to be clear, p4 isn't actually a network protocol. It's a programming language, a DSL for programming network protocols. Small but significant difference between the two. But you're correct that it will require native support among router/switch vendors to be worth using.

Actually, p4 is aimed a solving a lot of the problems with OpenFlow that led to the situation you describe: incomplete support by vendors of all the different versions of OpenFlow. That's because each individual network protocol supported had to be written into the OpenFlow spec, thus the proliferation of versions. Whereas with p4, the vendors basically just provide a hardware runtime for the p4 language, and you install whichever protocols you wish to support (or write it yourself, if it's custom or new). It also has the potential to work very well with a scaled-down version of OpenFlow.

I'm not an SDN expert and am probably not doing justice to p4 with my description above, but it is important to realize this isn't just another network protocol. It would be like describing the Python or JS as just another program (the interpreter), and not as a program capable of running other programs.

[superbaconman]

Yes, thanks for the corrections you are absolutely correct.

[andy_ppp]

Cool stuff! Any reason why you switched to Lua from Elixir and any links to github with the code?

[eric_bullington]

Well, I switched to Lua because Snabb apps are built in Lua, and because the Snabb toolkit will ideally provide a lot of functionality for the runtime that I won't have to build myself. And Snabb is really quite impressive in itself.

That said, Elixir is an awesome language, and lovely to write lexer/parsers in. I took me only a few hours to build a functioning parser in Elixir, compared to several days to build one in Lua.

The p4 parser/lexer in Lua is here: https://github.com/esbullington/snabbp4

Next step would be to generate the parse graph.