Everything about icmp
So. Serializing IPv4 packets. Easy? Well, not exactly.
IPv4 was annoying to parse, because we had 3-bit integers, and 13-bit integers, and who knows what else. Serializing it is going to be exactly the same.
In the last part, we've finally parsed some IPv4 packets. We even found a way to filter only IPv4 packets that contain ICMP packets.
Let's set aside our
sup project for a while.
Don't get me wrong - it's a perfectly fine project, and, were we simply rewriting "ping" for Windows in Rust, we could (almost) stop there.
Our ping API is simple, but it's also very limited:
pub fn ping(dest: ipv4::Addr) -> Result<(), String> // called as: ping(ipv4::Addr([8, 8, 8, 8])).unwrap();
We've just spent a lot of time abstracting over LoadLibrary, but we still have all the gory details of the Win32 ICMP API straight in our main.rs file! That won't do.
It's time to make
sup, our own take on
ping, use the Win32 APIs to send
an ICMP echo. Earlier we discovered that Windows's
IcmpSendEcho2Ex. But for our purposes, the simpler
IcmpSendEcho will do
So, how does
ping.exe actually send a ping? It seems unrealistic that
ping.exe itself implements all the protocols involved in sending a ping.
So it must be calling some sort of library. Also, since it ends up
talking to the outside world via a NIC (network interface controller),
the kernel is probably involved at some point.