[action] [PR:25947] [C0] Update timeout fomula for test_console_loopback

[mssonicbld]

Description of PR

Summary: Re-evaluate the timeout formula in test_console_loopback so it reflects the actual round-trip cost.

The old formula (packet_size * 10) * delay_factor / baud_rate models only the on-wire transmission time and scales inversely with baud rate. The real round-trip also includes baud-independent overhead: SSH round-trip through the mgmt LAN, sshd + pty + picocom bridge on the DUT, and pexpect's poll granularity. Splitting the timeout into a fixed term plus a wire-time term is a more accurate model, and lets us drop the platform-specific fudge factors that were compensating for the missing term.

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• New Test case
  • Skipped for non-supported platforms
• Test case improvement

Back port request

• 202311
• 202405
• 202411
• 202505
• 202511
• 202512
• 202605

Tracking issue/work item for backport/cherry-pick request:
Failure type:

Approach

What is the motivation for this PR?

The existing formula only accounts for on-wire time, so the timeout shrinks with baud rate even though the fixed SSH/pty/pexpect overhead does not. This forced per-platform multipliers to keep the timeout usable, and still left tight cases at high baud rates.

How did you do it?

timeout = overhead_seconds + wire_time, with overhead_seconds = 0.1. Platform-specific multipliers removed since the fixed term makes them unnecessary.

0.1 s covers the observed fixed overhead on an idle test env: SSH RTT through the mgmt LAN (a few switches), sshd + pty + picocom on the DUT, and pexpect's 10 ms poll — typically 15-30 ms, leaving headroom for jitter.

How did you verify/test it?

Ran test_console_loopback.py on 4 physical testbeds covering:

• Nokia-7215-C1: same-host and diff-host (c0-lo and c0)
• Cisco-C8220TG: same-host and diff-host (c0-lo and c0)

Result: 24 passed, 8 skipped (pingpong skips on same-host by design), 0 failed.

Any platform specific information?

None — the fixed overhead term makes the platform-specific multipliers unnecessary.

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

N/A (existing test).

Documentation

N/A.

Signed-off-by: Sonic Build Admin sonicbld@microsoft.com

[mssonicbld]

Original PR: sonic-net/sonic-mgmt#25947

[mssonicbld]

/azp run

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