udev: do not try to rename interface if it is already up

See dev_change_name() in kernel's net/core/dev.c.

Fixes #21105.

(cherry picked from commit 6681eb021a0b56ef0dc849e3b358a515ece16482)

1 files changed, 11 insertions, 0 deletions

diff --git a/src/udev/udev-event.c b/src/udev/udev-event.c
index b28089be71..9854270b27 100644
--- a/src/udev/udev-event.c
+++ b/src/udev/udev-event.c
@@ -828,6 +828,7 @@ int udev_event_spawn(UdevEvent *event,
 static int rename_netif(UdevEvent *event) {
         sd_device *dev = event->dev;
         const char *oldname;
+        unsigned flags;
         int ifindex, r;
 
         if (!event->name)
@@ -855,6 +856,16 @@ static int rename_netif(UdevEvent *event) {
                 return 0;
         }
 
+        r = rtnl_get_link_info(&event->rtnl, ifindex, NULL, &flags);
+        if (r < 0)
+                return log_device_warning_errno(dev, r, "Failed to get link flags: %m");
+
+        if (FLAGS_SET(flags, IFF_UP)) {
+                log_device_info(dev, "Network interface '%s' is already up, refusing to rename to '%s'.",
+                                oldname, event->name);
+                return 0;
+        }
+
         /* Set ID_RENAMING boolean property here, and drop it in the corresponding move uevent later. */
         r = device_add_property(dev, "ID_RENAMING", "1");
         if (r < 0)