[Feature] missing "--tun-post-down" option

[aa51513]

Description

After starting tun2socks, I used the "--tun-post-up" option to adjust the routing table,

but now I have a problem, I can't find the hook to restore the routing table after the process is closed,

I think "--tun -post-down" option is very necessary

Is this feature related to a specific bug?

no

Do you have a specific solution in mind?

add "--tun-post-down" option

[Juan Calderon-Perez]

@xjasonlyu This would be very helpful to keep a clean state. Else when the interface comes back up it will run post-up twice

[Jason Lyu]

sounds good