[PATCH 3/3] udevHandleOneDevice: Remove old instance of device on "move"

Michal Privoznik mprivozn at redhat.com
Mon Apr 20 14:20:41 UTC 2020

When a device is "move"-d (this basically means it was renamed),
we add the new device onto our list but keep the old there too.
Fortunately, udev sets this DEVPATH_OLD property which points to
the old device path. We can use it to remove the old instance.

To test this try renaming an interface, for instance:

  # ip link set tunl0 name tunl1
  # ip link set tunl1 name tunl0

One problem with udev is that it sends old ifname in INTERFACE
property, which creates a problem for us, the property is where
we get the ifname from and use it then to query all kind of info
about the interface. Well, if it is non-existent then we can't
query anything. This happens if ifname rename is suppressed
(net.ifnames=0 on kernel cmd line for instance). Fortunately, we
can use "kernel" source for udev events which has always the
fresh info.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
 src/node_device/node_device_udev.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index e9a76a7b01..386f23ef3a 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -1507,7 +1507,14 @@ udevHandleOneDevice(struct udev_device *device)
         return udevRemoveOneDevice(device);
     if (STREQ(action, "move")) {
-        /* TODO: implement a way of finding and removing the old device */
+        const char *devpath_old = udevGetDeviceProperty(device, "DEVPATH_OLD");
+        if (devpath_old) {
+            g_autofree char *devpath_old_fixed = g_strdup_printf("/sys%s", devpath_old);
+            udevRemoveOneDeviceSysPath(devpath_old_fixed);
+        }
         return udevAddOneDevice(device);
@@ -1872,7 +1879,7 @@ nodeStateInitialize(bool privileged,
-    priv->udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
+    priv->udev_monitor = udev_monitor_new_from_netlink(udev, "kernel");
     if (!priv->udev_monitor) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("udev_monitor_new_from_netlink returned NULL"));

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