[upgrade_path]Bug fix in test_upgrade_path

[bingwang-ms]

Description of PR

Summary:
Fixes # (issue)
This PR is to fix several bug in test_upgrade_path.

1. Fix bug in check_sonic_version_after_reboot;
2. Add filter for ping_dataplane to cut down CPU usage (99.9% -> 40%);
3. Refactor code in test_upgrade_path;
4. Use creds to retrive ssh_user and password.

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Approach

What is the motivation for this PR?

This PR is to fix several bug in test_upgrade_path.

How did you do it?

Fix several bugs.

1. Fix bug in check_sonic_version_after_reboot
   The original position of check_sonic_version_after_reboot is too closer to reboot, as a result, it might get a incorrect version. This commit moved it to the end of test.
2. Add filter for ping_dataplane to cut down CPU usage (99.9% -> 40%)
   A filter is applied before ping_dataplane to cut down CPU usage. At the very beginning of test, flooding ARP packets are captured and analyzed by ptf, which cousume lots of CPU. The filter only allow packets on port 5000 in, and the CPU usage is cut down from 99.9% to up to 40%. At the same time, the packet queue is also increase from 1000 to 10000 because the queue is full according debug log.
3. Refactor code in test_upgrade_path
   Use fixture to handle ptf scripts.
4. Use creds to retrive ssh_user and password

How did you verify/test it?

Verified on Arista-7260cx3

py.test upgrade_path/test_upgrade_path.py --inventory ../ansible/str,../ansible/veos --host-pattern str-7260cx3-acs-1 --module-path ../ansible/library/ --testbed vms7-t0-7260-1 --testbed_file ../ansible/testbed.csv --junit-xml=tr.xml --log-cli-level warn --base_image_list=http://100.127.20.23/installer/sonic/broadcom/internal-201811/sonic-aboot-broadcom-20181130.51.swi --target_image_list=http://100.127.20.23/installer/sonic/broadcom/internal-201811/sonic-aboot-broadcom.swi --restore_to_image=http://100.127.20.23/installer/sonic/broadcom/internal-201911/sonic-aboot-broadcom.swi
========================================================================================= test session starts =========================================================================================
platform linux2 -- Python 2.7.12, pytest-4.6.5, py-1.8.1, pluggy-0.13.1 -- /usr/bin/python
cachedir: .pytest_cache
ansible: 2.8.7
rootdir: /data/Networking-acs-sonic-mgmt/tests, inifile: pytest.ini
plugins: forked-1.1.3, xdist-1.28.0, ansible-2.2.2, repeat-0.8.0
collected 1 item                                                                                                                                                                                      

upgrade_path/test_upgrade_path.py::test_upgrade_path ^@^@^H^@^@PASSED                                                                                                                                     [100%]

------------------------------------------------------------------ generated xml file: /data/Networking-acs-sonic-mgmt/tests/tr.xml -------------------------------------------------------------------
===================================================================================== 1 passed in 1507.58 seconds =====================================================================================

Any platform specific information?

No.

Supported testbed topology if it's a new test case?

N/A

Documentation

No.

[lgtm-com]

This pull request introduces 1 alert when merging 1bcb7a3 into 528fb67 - view on LGTM.com

new alerts:

• 1 for Unused local variable

[bingwang-ms]

retest vsimage please

[neethajohn]

isn't this needed?

[tahmed-dev]

This required as all interface on new ptfdocker would have the same mac address.

[bingwang-ms]

Thanks. I'll recover it back.

[bingwang-ms]

Add and remove filter from fd frequently introduces a noticable delay. So I close this PR until fix it.