net_util: Remove unit error from Result

error: this returns a `Result<_, ()>
  --> net_util/src/mac.rs:68:5
   |
68 |     pub fn from_bytes(src: &[u8]) -> Result<MacAddr, ()> {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `-D clippy::result-unit-err` implied by `-D warnings`
   = help: use a custom Error type instead
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#result_unit_err

Replace with std::io::Error like other locations in the same file.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

net_util/src/mac.rs

@@ -65,9 +65,12 @@ impl MacAddr {
 
     // An error can only occur if the slice length is different from MAC_ADDR_LEN.
     #[inline]
-    pub fn from_bytes(src: &[u8]) -> Result<MacAddr, ()> {
+    pub fn from_bytes(src: &[u8]) -> Result<MacAddr, io::Error> {
         if src.len() != MAC_ADDR_LEN {
-            return Err(());
+            return Err(io::Error::new(
+                io::ErrorKind::Other,
+                format!("invalid length of slice: {} vs {}", src.len(), MAC_ADDR_LEN),
+            ));
         }
         Ok(MacAddr::from_bytes_unchecked(src))
     }

net_util/src/tap.rs

@@ -31,7 +31,7 @@ pub enum Error {
     NetUtil(NetUtilError),
     InvalidIfname,
     /// Error parsing MAC data
-    MacParsing(()),
+    MacParsing(IoError),
 }
 
 pub type Result<T> = ::std::result::Result<T, Error>;