USB Gadget script: Problematic eth0 fallback logic needs redesign or removal

[coderabbitai]

Problem

The USB gadget network setup script contains fallback logic that attempts to use eth0 as a default interface, but this approach has fundamental issues:

Current problematic code (lines 87-89):

if [ -z $INTERFACE ]; then
  ip a add "${host_ip}/255.255.0.0" dev eth0 2> /dev/null && eth0 && INTERFACE=eth0
fi

Issues identified:

1. Syntax error: The && eth0 && token in the command chain is invalid and prevents the fallback from working
2. Obsolete assumption: eth0 is no longer a reliable interface name on modern Linux systems
3. Predictable network interface naming: Modern systems use names like end0 or other persistent naming schemes instead of eth0

Recommended solutions:

• Option 1: Remove the fallback logic entirely, as there's no reliable way to choose the "right" fallback interface
• Option 2: Implement a configuration file approach (e.g., /etc/default config) to allow users to specify the correct fallback interface
• Option 3: Implement dynamic interface detection logic that doesn't rely on hardcoded interface names

Context

This issue was identified during review of PR #8601, which addresses logging inconsistencies in the same script.

Related:

• PR: BSP: fix incorrect logging for USB Gadget script #8601
• Original comment: BSP: fix incorrect logging for USB Gadget script #8601 (comment)

Impact: The current fallback logic fails silently and may leave the USB gadget network in a non-functional state when the primary interface detection fails.

[github-actions]

Jira ticket: AR-2746