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Bug: VXLAN entropy tests intermittently lose packets when the PTF receive queue overflowsΒ #27561

Description

@zypgithub

Is it platform specific

generic

Importance or Severity

Critical

Description of the bug

VXLAN entropy tests can report packet-count or ECMP distribution failures even when VXLAN forwarding is working correctly.

The test sends up to 1,000 packets before polling for responses, while the PTF receive queue is also configured for 1,000 packets. During bursty traffic or delayed packet processing, returned VXLAN packets can fill the receive queue before polling begins. Packets dropped from the queue are then treated as forwarding loss by the test.

Steps to Reproduce

Run test case vxlan/test_vxlan_ecmp.py::Test_VxLAN_entropy::test_vxlan_varying_src_ip[v6_in_v6]

Actual Behavior and Expected Behavior

Actual Behavior

The PTF test may collect fewer packets than were sent because the receive queue fills before the test polls and drains it. This causes intermittent packet-accounting or ECMP distribution failures even though the DUT forwarded the packets correctly.

Expected Behavior

The test should collect all expected VXLAN packets without overflowing the PTF receive queue. Packet-count and ECMP distribution checks should reflect DUT forwarding behavior rather than packet loss in the test infrastructure.

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