> The issue is that the rust library apparently conflates datagram and UDP, when they're not the same thing.

It comes down to these two lines (using full items paths for clarity):

    let socket = socket2::Socket::new(Domain::IPV4, Type::DGRAM, Some(Protocol::ICMPV4))?;
    let socket: std::net::UdpSocket = socket.into();

Basically the `socket2` crate lets you convert the fd it produces into a `UdpSocket`. It doesn't verify it really is a UDP socket first; that's up to you. If you do it blindly, you can get something with the wrong name, but it's probably harmless. (At the very least, it doesn't violate memory safety guarantees, which is what Rust code tends to be very strict about.)

`UdpSocket` itself has a `From<OwnedFd>` impl that similarly doesn't check it really is a UDP socket; you could convert the `socket2::Socket` to an `OwnedFd` then that to a `UdpSocket`. https://doc.rust-lang.org/stable/std/net/struct.UdpSocket.ht... https://docs.rs/socket2/0.6.1/socket2/struct.Socket.html#imp...

It may be memory safe but it's not using the type system to represent the domain very well.

One could imagine a more type-friendly design in which we could write that first line as follows:

    let socket: Socket<IPv4, Datagram, IcmpV4> = Socket::new()?;

Edit: I realized that the issue here is actually the conversion, and that UdpSocket on its own is actually a type-safe representation of a UDP socket, not a general datagram socket. But the fact that this dubiously-safe conversion is possible and even useful suggests that an improved design is possible. For example, a method like UdpSocket's `set_broadcast` can't work with a socket like the above, and from a type safety perspective, it shouldn't be possible to call it on such a socket.