fix: use better timings

Linux beacons weren't timing out and attempting to continue driving the
connection

Windows beacons still get stuck on their first connection, but that is
good enough for demonstration purposes

sparse-beacon/src/socket.rs

@@ -24,7 +24,7 @@ impl RawSocket {
         let name = std::str::from_utf8(&name_raw)?;
         let mut lower = Interface::new(name)?;
 
-        let mtu = a_interface.mtu as usize - if cfg!(unix) { 14 } else { 0 };
+        let mtu = a_interface.mtu as usize - if cfg!(unix) { 28 } else { 0 };
 
         lower.set_promisc(promisc)?;
         lower.set_buffer_size(mtu as i32)?;