Feature Request: Implement "up" state filter ("ip addr show up") #71
Description
First, thank you for this very useful tool. It's a fantastic bridge for those of us who switch between Linux and macOS environments.
Feature Request
On Linux, a very common command is ip addr show up to list only the interfaces that are currently in the "UP" state.
It appears iproute2mac does not support this state-based filter. When running ip addr show up, the tool (correctly, given its current implementation) interprets up as a device name, which isn't the intended behavior for users accustomed to the Linux original.
I would like to offer to implement this feature.
Full disclosure: I am not a seasoned Python programmer (my background is primarily in Go, Rust, and Java). However, I am very willing to learn and contribute.
If you are interested in having this feature and are patient with my learning process and potential questions, I would be happy to put in the work and submit a pull request.
Please let me know if you are open to this contribution. If so, any initial guidance on where to start looking in the codebase would be greatly appreciated!