Feature Request: extent IsInSubnet to support Subnet-to-Subnet Containment

[oryaacov]

Feature Request: Add Subnet-to-Subnet Containment Support

Opening words

You guys are doing an amazing work! thank you guys! :)

Summary

Add support for checking if one subnet is contained within another subnet.

Current vs Requested Behavior

Current:

isInSubnet('10.5.0.1', '10.4.5.0/16'); // IP in subnet

Requested:

isInSubnet('10.5.0.0/24', '10.4.0.0/16'); // true - subnet in subnet
isInSubnet('10.5.0.0/16', '10.4.0.0/24'); // false - larger cannot fit in smaller
isInSubnet('2001:db8:1::/64', '2001:db8::/32'); // true - IPv6 support

Use Cases

• Network planning and IPAM validation
• Security policy verification
• Cloud infrastructure subnet management

This would make the library much more useful for network management tasks.

[whitequark]

Seems fine to me as a feature. I don't have time to implement it though.