IPv6 route remove does not seem to work

[AaronKutch]

Using

net-route = "0.4"
tun = { version = "0.7", features = ["async"] }
netdev = "0.32"

    let addr = "10.0.0.1".parse().unwrap();
    let cidr = 32;
    //let addr = "fd00::1".parse().unwrap();
    //let cidr = 128;

    let tun_name = "test";
    let device = tun::create_as_async(&tun::configure().tun_name(tun_name).up()).unwrap();

    let interfaces = netdev::get_interfaces();
    let ni = {
        if let Some(name) = interfaces.iter().find(|x| x.name == tun_name) {
            name
        } else {
            // in some cases
            interfaces
                .iter()
                .find(|x| x.friendly_name.as_deref() == Some(tun_name))
                .unwrap()
        }
    };
    let ifindex = ni.index;

    let handle = net_route::Handle::new().unwrap();

    handle
        .add(&net_route::Route::new(addr, cidr).with_ifindex(ifindex))
        .await
        .unwrap();

    handle
        .delete(&net_route::Route::new(addr, cidr).with_ifindex(ifindex))
        .await
        .unwrap();

    drop(device);

The version adding and deleting an IPv4 address works fine for me on Linux, but with an IPv6 address the deletion function fails with

called `Result::unwrap()` on an `Err` value: Custom { kind: NotFound, error: "No matching route found to delete" }

I don't know what is happening here, running ip route del ... dev test works for both addresses, something this library is doing with IPv6 is not working. This is happening on more than one kind of Linux distribution for me, so I think it is some common issue.

[bryanlarsen]

We're also seeing this behavior. It appears to be a problem with the metric. If you do a list() after your add, you'll likely find the route has a metric different than the default one set in Route::new. Explicitly setting a metric may help you. The solution we've implemented is to do a list() before the delete, pull the matching route from the list and delete that.