[Test gap] Test dhcp_relay with source port ip enabled

[yejianquan]

Description of PR

Summary:
Fixes #3624
Mitigate the test gap: Test dhcp relay with source port ip in relay enabled.

Type of change

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

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

What is the motivation for this PR?

Fixes #3624
Mitigate the test gap: Test dhcp relay with source port ip in relay enabled.

How did you do it?

1. Enhance dhcp_relay ptf test to verify the src_ip in relay packets
2. Add a fixture which modify deployment_id to 8 and enable source port ip in relay
3. Add a test case exactly same with test_dhcp_relay_default but include fixture enable_source_port_ip_in_relay.

How did you verify/test it?

Run on local dev vm,
dhcp_relay/test_dhcp_relay.py::test_interface_binding PASSED [ 12%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_default PASSED [ 25%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_with_source_port_ip_in_relay_enabled PASSED [ 37%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_after_link_flap PASSED [ 50%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_start_with_uplinks_down PASSED [ 62%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_unicast_mac PASSED [ 75%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_random_sport PASSED [ 87%]
dhcp_relay/test_dhcp_relay.py::test_dhcp_relay_counter SKIPPED (skip...) [100%]
and PR test will test it again.

Any platform specific information?

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

Documentation

[yejianquan]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[yejianquan]

Hi @Blueve @yaqiangz , could you please help to review this PR?

[yaqiangz]

LGTM

[yaqiangz]

Hold on..

[yaqiangz]

Hi @lolyu does dualtor need this test? It would affect source IP sent from relay to DHCP server

[lolyu]

Hi @lolyu does dualtor need this test? It would affect source IP sent from relay to DHCP server

If it is a generic feature on T0, dualtor will need it.
dhcp-relay will enable source port ip on t0, right?

[yejianquan]

Hi @lolyu does dualtor need this test? It would affect source IP sent from relay to DHCP server

If it is a generic feature on T0, dualtor will need it. dhcp-relay will enable source port ip on t0, right?

@lolyu What do you mean by 'dhcp-relay will enable source port ip on t0'?

From my understanding and research,
when the -si is used, in the relay packets, the source ip will be client_ip instead of the loopback ip of DUT.

In the buildimage, only when deployment_id==8, we enable source ip in relay.
https://github.com/sonic-net/sonic-buildimage/blob/e0e0c0c1b3c58635bc25fde6a77ca3b0849dfde1/dockers/docker-dhcp-relay/dhcpv4-relay.agents.j2#L16
But not sure when the deployment_id will be 8 in the production ENV.