Sat, Oct 29, 2016 at 04:49:03PM CEST, kubakici@wp.pl wrote:

On Sat, 29 Oct 2016 09:53:28 +0200, Jiri Pirko wrote:

quoted

Hi all.

The network world is divided into 2 general types of hw:
1) network ASICs - network specific silicon, containing things like TCAM
   These ASICs are suitable to be programmed by P4.
2) network processors - basically a general purpose CPUs
   These processors are suitable to be programmed by eBPF.

I believe that by now, the most people came to a conclusion that it is
very difficult to handle both types by either P4 or eBPF. And since
eBPF is part of the kernel, I would like to introduce P4 into kernel
as well. Here's a plan:

1) Define P4 intermediate representation
   I cannot imagine loading P4 program (c-like syntax text file) into
   kernel as is. That means that as the first step, we need find some
   intermediate representation. I can imagine someting in a form of AST,
   call it "p4ast". I don't really know how to do this exactly though,
   it's just an idea.

   In the end there would be a userspace precompiler for this:
   $ makep4ast example.p4 example.ast

Maybe stating the obvious, but IMHO defining the IR is the hardest part.
eBPF *is* the IR, we can compile C, P4 or even JIT Lua to eBPF.  The
AST/IR for switch pipelines should allow for similar flexibility.
Looser coupling would also protect us from changes in spec of the high
level language.

Agreed. I agree with you point this would be nice to have it done in a
generic way. However, I'm not aware of any other language similar to p4.