Wsl2 support for generated configs

[Sammers21]

By default generated configs does not allow WSL2 to access network with wireguard enabled. So here is the quick fix for it: microsoft/WSL#7895 (comment)

I guess DNS server must be changed too to 1.1.1.1, does not work without it for me.

[CLAassistant]

All committers have signed the CLA.

[dguido]

Technical Review

Thank you for this PR addressing WSL2 compatibility. I've analyzed the changes and their implications:

What This Change Does

The PR modifies the WireGuard AllowedIPs configuration from:

• 0.0.0.0/0,::/0 (route all traffic through VPN)
• To: ::/128, 0.0.0.0/1, 128.0.0.0/1 (split routing)

Breaking down the changes:

1. IPv6: Changes from ::/0 (all IPv6 traffic) to ::/128 (only the :: address itself)
2. IPv4: Splits 0.0.0.0/0 into two halves: 0.0.0.0/1 (0.0.0.0-127.255.255.255) and 128.0.0.0/1 (128.0.0.0-255.255.255.255)

Why This Helps WSL2

WSL2 has known networking quirks due to its virtualized network stack. This split routing approach is a documented workaround in the WireGuard community that helps avoid conflicts with WSL2's internal networking.

Concerns

1. IPv6 Impact: This change effectively disables IPv6 VPN routing for all users. Only the :: address itself will be routed through the VPN, meaning IPv6 traffic will leak outside the VPN tunnel.

2. Global Change: This affects all WireGuard configurations generated by Algo, not just those intended for WSL2 users.

3. DNS Configuration: You mentioned needing to change DNS to 1.1.1.1, but this change isn't included in the PR.

Recommendation

While this fix helps WSL2 users, applying it globally would break IPv6 VPN functionality for everyone else. Instead, consider:

1. Making this configuration optional during setup (e.g., "Will you use WireGuard on WSL2?")
2. Generating WSL2-specific configuration files alongside standard ones
3. Adding documentation about the IPv6 limitation
4. Addressing the DNS configuration if it's also needed for WSL2

This way, WSL2 users get the fix they need without impacting other users' VPN functionality.