fix(vpn): remove deprecated endpoint-independent NAT from tun defaults

[garmr-ulfr]

This pull request makes a small change to the default inbound configuration in vpn/boxoptions_default.go. The EndpointIndependentNat option was removed from the returned struct in the baseInbounds function. EndpointIndependentNat is only supported on gVisor stacks and is deprecated, so drop it from the system stack tun configuration.

Summary by CodeRabbit

• Bug Fixes
  • Updated TUN networking configuration while preserving existing interface, routing, and system stack settings.
  • Removed endpoint-independent NAT behavior from the default VPN inbound configuration.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8469a260-822d-48b6-a90b-1dfe7119b740

📥 Commits

Reviewing files that changed from the base of the PR and between 15a9ace and 7a96ac6.

📒 Files selected for processing (1)

• vpn/boxoptions_default.go

📝 Walkthrough

Walkthrough

The default utun225 TUN inbound configuration removes EndpointIndependentNat while retaining its interface, addresses, routing settings, and initial system stack.

Changes

TUN inbound configuration

Layer / File(s)	Summary
Update default TUN options vpn/boxoptions_default.go	Removes the EndpointIndependentNat assignment from the utun225 TUN inbound options while preserving the existing routing and stack settings.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: copilot, reflog

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: removing deprecated EndpointIndependentNat from the VPN TUN default configuration.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch remove-endpoint-independent-nat

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[Copilot]

Pull request overview

Removes the deprecated EndpointIndependentNat setting from the default TUN inbound options, aligning the default system-stack configuration with current sing-box support expectations.

Changes:

• Drops EndpointIndependentNat: true from baseInbounds()’s O.TunInboundOptions defaults.
• Removes the inline rationale comment that was tied to enabling endpoint-independent NAT by default.

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[atavism]

LGTM

[garmr-ulfr]

Thanks @atavism!