Replace unnecessary use of Scapy with ptf.pcap_writer in p4tc tests

[jafingerhut]

This replacement allows the resulting test program to be licensed under Apache 2.0 license.

[jafingerhut]

@vbnogueira Please take a look at these changes, which are nearly identical to ones that I have made to bmv2 back end testing Python code in order to eliminate unnecessary uses of Scapy. If we do not do this, the Python files that import scapy must be licnesed as GPL-2.0-only. With these changes (assuming the tests still work -- waiting for CI test results now), the Python program can be licensed as Apache-2.0.

Regarding the standalone program named send_packet: as far as I can tell, it is not used anywhere. Would you be OK if we removed it? Or is it useful in your unit testing on your local development system, perhaps? I am OK if we keep it, as long as we license it as GPL-2.0-only, as proposed in this PR.

[vbnogueira]

@vbnogueira Please take a look at these changes, which are nearly identical to ones that I have made to bmv2 back end testing Python code in order to eliminate unnecessary uses of Scapy. If we do not do this, the Python files that import scapy must be licnesed as GPL-2.0-only. With these changes (assuming the tests still work -- waiting for CI test results now), the Python program can be licensed as Apache-2.0.

Thank you for the heads up.
I'll run the test locally today or tomorrow.
Everything seems to be fine, but just want to double check.

Regarding the standalone program named send_packet: as far as I can tell, it is not used anywhere.

It is, but it's not very explicit.
We assign it as send_script here [1] and run it inside the VM here [2]

Would you be OK if we removed it? Or is it useful in your unit testing on your local development system, perhaps? I am OK if we keep it, as long as we license it as GPL-2.0-only, as proposed in this PR.

Yes, we need to keep it, but I have no problem in changing the licence.

[1] https://github.com/jafingerhut/p4c/blob/replace-scapy-with-apache-code-in-p4tc-tests/backends/tc/test_infra.py#L232
[2] https://github.com/jafingerhut/p4c/blob/replace-scapy-with-apache-code-in-p4tc-tests/backends/tc/test_infra.py#L285

[jafingerhut]

@vbnogueira Please take a look at these changes, which are nearly identical to ones that I have made to bmv2 back end testing Python code in order to eliminate unnecessary uses of Scapy. If we do not do this, the Python files that import scapy must be licnesed as GPL-2.0-only. With these changes (assuming the tests still work -- waiting for CI test results now), the Python program can be licensed as Apache-2.0.

Thank you for the heads up. I'll run the test locally today or tomorrow. Everything seems to be fine, but just want to double check.

Running it locally will require using the latest version of the ptf package installed from https://github.com/p4lang/ptf source code. Using pip install ptf will get an older version.

[jafingerhut]

@vbnogueira Looks like all tests are passing in CI with these changes, except the Python formatter, which I will fix soon. If you get good local test results with the latest version of https://github.com/p4lang/ptf code, please approve the PR (unless you have other suggestions for changes).

[jafingerhut]

@vbnogueira Thanks for trying this out and approving. I will go ahead and merge given your approval and my testing.

FYI, I have found a small enhancement to the ptf package that should enable even your send_packet script to be licensed Apache-2.0, which I have tested with this PR: #5145

but given that it has a few other PRs that must be approved and merged before we can merge that one, it might be a while before that gets in.

[jafingerhut]

I jumped the gun on my previous comment -- merging this must wait for an approval from a reviewer with write access.

[fruffy]

Is this still needed?

[fruffy]

@vbnogueira Can we replace this code with the other utilities we are using?

[jafingerhut]

@fruffy It is currently used by the p4tc tests.

I have a way to update ptf and bf-pktpy with a few extra lines of code, such that we can relicense this send_packet file as Apache-2.0. I have those changes in this PR, but there are a couple of other PRs that must be approved and merged first before it can be merged: #5145