add From<u32> for Ip

src/ip.rs

@@ -44,6 +44,19 @@ impl From<&Ip> for u32 {
     }
 }
 
+// convertion the other way arround, from u32 to Ip::V4
+impl From<u32> for Ip {
+    fn from(src: u32) -> Self {
+        let array = [ ((src >> 24) & 0xff) as u8,
+                        ((src >> 16) & 0xff) as u8,
+                        ((src >> 8) & 0xff) as u8,
+                        (src & 0xff) as u8
+        ];
+        Ip::V4(array)
+    }
+}
+
+
 // Display is a standard trait used by format! and println! and others
 // to display objects...
 impl Display for Ip {
@@ -91,3 +104,9 @@ fn test_u32_from_ip() {
     let nbr = u32::from(&ip);
     assert_eq!(nbr, 0x7f000001);
 }
+
+#[test]
+fn test_ip_from_u32() {
+    let ip = Ip::from(0x7f000001);
+    assert_eq!(ip, Ip::V4([127, 0, 0, 1]));
+}