antoninbas
commented
1 month ago This code is written in C for legacy reasons. It was "copied over" years ago from the previous version of the behavioral model: https://github.com/p4lang/p4factory/tree/master/modules/BMI. There was no strong reason to rewrite this code at the time (although I think it may have been marginally improved over time), as it was working and this is a part of the code that is both essential and hard to test in an automatic way.
That being said, I think rewriting this code in C++ and taking a more modern approach (I would say the select-based approach is probably a bit obsolete now) is a great idea. While I will not work on this, I would be happy to review such a change. I would say that if anyone wants to work on this, please do not start any implementation work until first presenting your proposed approach here and getting some sort of consensus. I would be fine with something that is based on Boost Asio.
Before approving such a change, and because we don't have automated tests for the I/O code, I would expect the following:
- a performance comparison of the current approach and the new proposed approach using this benchmark: https://github.com/p4lang/behavioral-model/blob/main/docs/performance.md#running-the-benchmark. The new approach should yield at least the same throughput.
- a successful test run of the p4c PTF test suite using the modified bmv2 + veths for packet I/O. Assuming there is such a thing... cc @fruffy
fruffy
Hello everyone!
I'm trying to make a backward-compatible edit to the BMv2 simple switch. Simple switch passes a packet handler from the place that
static void packet_handler(int port_num, const char *buffer, int len, void *cookie)function is defined here, all the way to the place it's used in the bmi_port.c.I see that in the dev_mgr_bmi.cpp here, a transform is performed on the handler from std::function to C style function pointer, because the next code in the chain is a C code (bmi_port.c). I am trying to pass a std::function that has capture and this transform is causing some issues for me. Now I have a question. Why bmi_port.c is a C code and not C++. What is the restriction that binds us to use C code? Is it possible to change this to C++?