[BUG] Devcontainer init-firewall.sh does not block IPv6 traffic

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Devcontainer init-firewall.sh does not block access to IPv6 addresses. The check if example.com cannot be reached fails in IPv6 networks.

What Should Happen?

Devcontainer init-firewall.sh blocks access to IPv6 addresses. The check if example.com cannot be reached succeeds in IPv6 networks.

Error Messages/Logs

ERROR: Firewall verification failed - was able to reach https://example.com

Steps to Reproduce

Run Devcontainer with rootless podman in an IPv6 network.

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

v2.1.39

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

_No response_