From c55c64cce2449b4616b3f71b42fedc1e3098a04c Mon Sep 17 00:00:00 2001
From: Michal Sekletar <msekleta@redhat.com>
Date: Fri, 21 Sep 2018 08:42:58 +0000
Subject: [PATCH] core: don't rename interfaces that already have the name in
 expected format

---
 src/main.rs |  5 +++++
 src/util.rs | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index 54f4de4..5c1a42b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -37,6 +37,11 @@ fn main() {
         exit_maybe_unlock(None, 0);
     }
 
+    if ! rename_needed(&prefix).unwrap() {
+        info!("Interface name already has expected format, not renaming again");
+        exit_maybe_unlock(None, 0);
+    }
+
     let mut sema = match Semaphore::new_with_name("net-prefix-ifnames") {
         Ok(s) => s,
         Err(e) => {
diff --git a/src/util.rs b/src/util.rs
index 85a1090..8727074 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -11,6 +11,14 @@ use regex::Regex;
 
 use sema::*;
 
+pub fn rename_needed(prefix: &str) -> Result<bool, Box<Error>> {
+    // TODO: if INTERFACE is unset we should probably check sysname
+    let ifname = env::var("INTERFACE").unwrap_or("".to_string());
+    let re: Regex = Regex::new(&format!("{}\\d+", prefix)).unwrap();
+
+    Ok(!re.is_match(&ifname))
+}
+
 pub fn hwaddr_valid<T: ToString>(hwaddr: &T) -> bool {
     use std::num::ParseIntError;
 
@@ -161,4 +169,23 @@ mod tests {
     fn long_prefix_not_ok() {
         assert_eq!(false, prefix_ok(&"neeeeeeeeeeeeeeet"));
     }
+
+    #[test]
+    fn rename_is_needed() {
+        env::set_var("INTERFACE", "eth0");
+
+        assert_eq!(rename_needed("net").unwrap(), true);
+    }
+
+    #[test]
+    fn rename_not_needed() {
+        env::set_var("INTERFACE", "net0");
+
+        assert_eq!(rename_needed("net").unwrap(), false);
+    }
+
+    #[test]
+    fn rename_needed_interface_unset() {
+        assert_eq!(rename_needed("net").unwrap(), true);
+    }
 }
-- 
2.17.1