Adding UDP socket close funcionality

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 - Update `managed` from 0.7 to 0.8 ([442](https://github.com/smoltcp-rs/smoltcp/pull/442))
+- udp: Add `close()` method to unbind socket.
 
 ## [0.7.3] - 2021-05-29
 

src/socket/udp.rs

@@ -146,6 +146,11 @@ impl<'a> UdpSocket<'a> {
         Ok(())
     }
 
+    /// Close the socket.
+    pub fn close(&mut self) {
+        self.endpoint = IpEndpoint::default();
+    }
+
     /// Check whether the socket is open.
     #[inline]
     pub fn is_open(&self) -> bool {
@@ -624,4 +629,15 @@ mod test {
         assert_eq!(socket.process(&remote_ip_repr(), &repr, &[]), Ok(()));
         assert_eq!(socket.recv(), Ok((&[][..], REMOTE_END)));
     }
+
+    #[test]
+    fn test_closing() {
+        let recv_buffer = UdpSocketBuffer::new(vec![UdpPacketMetadata::EMPTY; 1], vec![]);
+        let mut socket = socket(recv_buffer, buffer(0));
+        assert_eq!(socket.bind(LOCAL_PORT), Ok(()));
+
+        assert!(socket.is_open());
+        socket.close();
+        assert!(!socket.is_open());
+    }
 }