fix aardvark-dns error handling

Big ops, we didn't handle any error when starting aardvark-dns. While we
waited for the fork to happen we never checked the exit status of the
command thus all errors were silently ignored. Also the command is
supposed to capture the error message so we can return it as proper
error string to podman. Before we should wrote to stderr which will not
show up for podman-remote users.

Of course right now aardvark-dns doesn't actually report many errors so
we never cought this but I am trying to make bind failures visible to
users so we need this.

Signed-off-by: Paul Holzinger <[email protected]>

Author: Luap99

src/dns/aardvark.rs

@@ -116,16 +116,35 @@ impl Aardvark {
         // After https://github.com/containers/aardvark-dns/pull/148 this command
         // will block till aardvark-dns's parent process returns back and let
         // aardvark inherit all the fds.
-        Command::new(aardvark_args[0])
+        let out = Command::new(aardvark_args[0])
             .args(&aardvark_args[1..])
-            .stdin(Stdio::inherit())
-            .stdout(Stdio::inherit())
-            .stderr(Stdio::inherit())
+            .stdin(Stdio::null())
+            .stdout(Stdio::null())
             // set RUST_LOG for aardvark
             .env("RUST_LOG", log::max_level().as_str())
             .output()?;
 
-        Ok(())
+        if out.status.success() {
+            return Ok(());
+        }
+        if out.stderr.is_empty() {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::Other,
+                "aardvark-dns exited unexpectedly without error message",
+            ));
+        }
+        // aardvark-dns failed capture stderr
+        let msg = String::from_utf8(out.stderr).map_err(|e| {
+            std::io::Error::new(
+                std::io::ErrorKind::Other,
+                format!("failed to parse aardvark-dns stderr message: {e}"),
+            )
+        })?;
+
+        Err(std::io::Error::new(
+            std::io::ErrorKind::Other,
+            format!("aardvark-dns failed to start: {}", msg),
+        ))
     }
 
     fn check_netns(&self, pid: pid_t) {