Check for the sudo password prompt and introduce a fallback when the prompt is not detected.

[binojrajan]

sudo 1.9.17 flushes the terminal input buffer (tcflush) before reading the password. The old check_and_input_password() sent the password after a blind 0.5-second delay — well before sudo displayed its "Password:" prompt on the slow QEMU (~3 seconds). The password got buffered in the PTY, then sudo flushed it and read nothing, causing it to re-prompt and eventually time out. This is a behavioral change from sudo 1.9.15p5 which read whatever was already buffered.

[binojrajan]

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[LiliDeng]

@lubaihua33 @paxue do you have any pipelines/scenario to verify this change?

[Copilot]

Pull request overview

Updates sudo password handling to wait for an actual password prompt (avoiding sudo 1.9.17+ input flush behavior) and adds a fallback path when prompt detection fails, plus an early prompt probe in sudo availability checks.

Changes:

• Wait for sudo password prompts before sending the password (with timeout + fallback).
• Add early detection of sudo password prompts during _check_sudo_available.
• Add additional prompt detection after command completion to classify “sudo needs password” as “sudo available”.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
lisa/util/process.py	Detects sudo prompt before sending password; adds timeout and fallback behavior.
lisa/node.py	Probes for sudo password prompt early and checks output for prompts to treat sudo as available.

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[Copilot]

Pull request overview

This PR improves sudo password handling for remote (SSH) command execution by synchronizing password input with the actual sudo prompt, and centralizes sudo prompt strings so Node and Process stay consistent.

Changes:

• Centralize sudo password prompt substrings into SUDO_PASSWORD_PROMPTS (shared by Process and Node).
• Update Process.check_and_input_password() to wait for the sudo password prompt (with a fallback) before sending the password to avoid tcflush-related drops on newer sudo versions.
• Speed up Node._check_sudo_available() by detecting sudo password prompts early during the probe.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
lisa/util/process.py	Adds shared sudo prompt constants and changes sudo password input to be prompt-synchronized with a timeout/fallback.
lisa/node.py	Reuses shared sudo prompt constants and adds early prompt detection during sudo availability probing.

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