udev-shim: Harden rules file write with retry loop

Handle BrokenPipe and AlreadyExists races when writing default udev
rules during early boot. Retry up to 3 times with 50ms backoff.

local/recipes/system/udev-shim/source/src/naming.rs

@@ -2,6 +2,8 @@ use std::fs;
 use std::io;
 use std::os::unix::fs::symlink;
 use std::path::Path;
+use std::thread;
+use std::time::Duration;
 
 const DEFAULT_UDEV_RULES: &str = r#"# Network interface naming
 SUBSYSTEM=="net", KERNEL=="enp*", NAME="$kernel"
@@ -74,8 +76,26 @@ pub fn write_default_rules_file() -> io::Result<&'static str> {
     fs::create_dir_all(dir)?;
 
     let path = dir.join("50-default.rules");
-    fs::write(&path, default_udev_rules())?;
-    Ok("/etc/udev/rules.d/50-default.rules")
+    let contents = default_udev_rules();
+
+    if fs::metadata(&path).is_ok() {
+        let _ = fs::remove_file(&path);
+    }
+
+    for attempt in 0..3 {
+        match fs::write(&path, contents) {
+            Ok(()) => return Ok("/etc/udev/rules.d/50-default.rules"),
+            Err(e) if e.kind() == io::ErrorKind::BrokenPipe && attempt < 2 => {
+                thread::sleep(Duration::from_millis(50));
+            }
+            Err(e) if e.kind() == io::ErrorKind::AlreadyExists => {
+                return Ok("/etc/udev/rules.d/50-default.rules");
+            }
+            Err(e) => return Err(e),
+        }
+    }
+
+    unreachable!("write_default_rules_file loop always returns or errors")
 }
 
 fn parse_hex_byte(value: &str) -> Option<u8> {