net_util: Fix map_err losing the inner error

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

net_util/src/mac.rs

@@ -7,6 +7,7 @@
 
 use rand::Rng;
 use std::fmt;
+use std::io;
 use std::result::Result;
 
 use serde::de::{Deserialize, Deserializer, Error};
@@ -20,23 +21,31 @@ pub struct MacAddr {
 }
 
 impl MacAddr {
-    // The error contains the str that failed to be parsed, for nicer error message generation.
+    pub fn parse_str<S>(s: &S) -> Result<MacAddr, io::Error>
-    pub fn parse_str<S>(s: &S) -> Result<MacAddr, &str>
     where
         S: AsRef<str> + ?Sized,
     {
         let v: Vec<&str> = s.as_ref().split(':').collect();
         let mut bytes = [0u8; MAC_ADDR_LEN];
+        let common_err = Err(io::Error::new(
+            io::ErrorKind::Other,
+            format!("parsing of {} into a MAC address failed", s.as_ref()),
+        ));
 
         if v.len() != MAC_ADDR_LEN {
-            return Err(s.as_ref());
+            return common_err;
         }
 
         for i in 0..MAC_ADDR_LEN {
             if v[i].len() != 2 {
-                return Err(s.as_ref());
+                return common_err;
             }
-            bytes[i] = u8::from_str_radix(v[i], 16).map_err(|_| s.as_ref())?;
+            bytes[i] = u8::from_str_radix(v[i], 16).map_err(|e| {
+                io::Error::new(
+                    io::ErrorKind::Other,
+                    format!("parsing of {} into a MAC address failed: {}", s.as_ref(), e),
+                )
+            })?;
         }
 
         Ok(MacAddr { bytes })
@@ -106,7 +115,8 @@ impl<'de> Deserialize<'de> for MacAddr {
         D: Deserializer<'de>,
     {
         let s = String::deserialize(deserializer)?;
-        MacAddr::parse_str(&s).map_err(|_| D::Error::custom("The provided MAC address is invalid."))
+        MacAddr::parse_str(&s)
+            .map_err(|e| D::Error::custom(format!("The provided MAC address is invalid: {}", e)))
     }
 }
 

vmm/src/config.rs

@@ -8,6 +8,7 @@ extern crate vm_virtio;
 use clap::ArgMatches;
 use net_util::MacAddr;
 use std::convert::From;
+use std::io;
 use std::net::AddrParseError;
 use std::net::Ipv4Addr;
 use std::path::PathBuf;
@@ -23,7 +24,7 @@ pub const DEFAULT_QUEUE_SIZE_VUBLK: u16 = 128;
 
 /// Errors associated with VM configuration parameters.
 #[derive(Debug)]
-pub enum Error<'a> {
+pub enum Error {
     /// Failed parsing cpus parameters.
     ParseCpusParams(std::num::ParseIntError),
     /// Unexpected vCPU parameter
@@ -45,7 +46,7 @@ pub enum Error<'a> {
     /// Failed parsing network mask parameter.
     ParseNetMaskParam(AddrParseError),
     /// Failed parsing network mac parameter.
-    ParseNetMacParam(&'a str),
+    ParseNetMacParam(io::Error),
     /// Failed parsing network queue number parameter.
     ParseNetNumQueuesParam(std::num::ParseIntError),
     /// Failed parsing network queue size parameter.
@@ -71,7 +72,7 @@ pub enum Error<'a> {
     /// Both console and serial are tty.
     ParseTTYParam,
     /// Failed parsing vhost-user-net mac parameter.
-    ParseVuNetMacParam(&'a str),
+    ParseVuNetMacParam(io::Error),
     /// Failed parsing vhost-user sock parameter.
     ParseVuSockParam,
     /// Failed parsing vhost-user queue number parameter.
@@ -91,7 +92,7 @@ pub enum Error<'a> {
     /// Failed parsing generic on|off parameter.
     ParseOnOff,
 }
-pub type Result<'a, T> = result::Result<T, Error<'a>>;
+pub type Result<T> = result::Result<T, Error>;
 
 pub struct VmParams<'a> {
     pub cpus: &'a str,