[PATCH] handle renamed network interfaces properly if we manage hotplug.d/

If we take over the hotplug call and manage the events we don't need
to call the event fake script in dev.d/. Just set all expected values
to the new network interface name and call hotplug.d/. This way the
device renaming is completely handled inside of udev and userspace
can't get confused.

etc/dev.d/net/hotplug.dev

@@ -8,15 +8,13 @@
 # Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
 #
 
-# See if we really did rename this device.
-if [ "$INTERFACE" = "$DEVNAME" ]; then
+# Do nothing if udev handles hotplug.d.
+if [ "$MANAGED_EVENT" == "1" ]; then
 	exit 0
 fi
 
-# ok, we have renamed this device, so let's set $INTERFACE to the new name
-# and call the network hotplug script to handle it properly...
-INTERFACE=$DEVNAME
-export INTERFACE
+# ok, we have renamed this device, so let the network hotplug script
+# know about it to setup the device properly...
 if [ -f /etc/hotplug.d/default/default.hotplug ]; then
 	exec /etc/hotplug.d/default/default.hotplug net
 fi

udev.c

@@ -54,31 +54,32 @@ void log_message(int level, const char *format, ...)
 }
 #endif
 
-/* (for now) true if udevsend is the helper */
+/* decide if we should manage the whole hotplug event
+ * for now look if the kernel calls udevsend instead of /sbin/hotplug
+ */
 static int manage_hotplug_event(void) {
 	char helper[256];
 	int fd;
 	int len;
 
-	/* false, if we are called directly */
-	if (!getenv("MANAGED_EVENT"))
-		goto exit;
+	/* don't handle hotplug.d if we are called directly */
+	if (!getenv("UDEVD_EVENT"))
+		return 0;
 
 	fd = open("/proc/sys/kernel/hotplug", O_RDONLY);
 	if (fd < 0)
-		goto exit;
+		return 0;
 
 	len = read(fd, helper, 256);
 	close(fd);
 
 	if (len < 0)
-		goto exit;
+		return 0;
 	helper[len] = '\0';
 
 	if (strstr(helper, "udevsend"))
 		return 1;
 
-exit:
 	return 0;
 }
 
@@ -104,6 +105,7 @@ int main(int argc, char *argv[], char *envp[])
 	const char *action;
 	const char *devpath;
 	const char *subsystem;
+	int managed_event;
 	int retval = -EINVAL;
 
 	if (argc == 2 && strcmp(argv[1], "-V") == 0) {
@@ -139,6 +141,11 @@ int main(int argc, char *argv[], char *envp[])
 		goto exit;
 	}
 
+	/* let the executed programs know if we handle the whole hotplug event */
+	managed_event = manage_hotplug_event();
+	if (managed_event)
+		setenv("MANAGED_EVENT", "1", 1);
+
 	action = getenv("ACTION");
 	devpath = getenv("DEVPATH");
 	subsystem = getenv("SUBSYSTEM");
@@ -238,7 +245,7 @@ int main(int argc, char *argv[], char *envp[])
 	}
 
 hotplug:
-	if (udev_hotplug_d && manage_hotplug_event())
+	if (udev_hotplug_d && managed_event)
 		udev_multiplex_directory(&udev, HOTPLUGD_DIR, HOTPLUG_SUFFIX);
 
 exit:

udev_add.c

@@ -318,15 +318,16 @@ int udev_add_device(struct udevice *udev, struct sysfs_class_device *class_dev)
 			if (retval != 0)
 				goto exit;
 
-			/* we've changed the name, now fake the devpath,
-			 * cause original kernel name sleeps with the fishes
-			 * and we don't get any event from the kernel now
+			/* we've changed the name, now fake the devpath, cause the
+			 * original kernel name sleeps with the fishes and we don't
+			 * get an event from the kernel with the new name
 			 */
 			pos = strrchr(udev->devpath, '/');
 			if (pos != NULL) {
 				pos[1] = '\0';
 				strfieldcat(udev->devpath, udev->name);
 				setenv("DEVPATH", udev->devpath, 1);
+				setenv("INTERFACE", udev->name, 1);
 			}
 
 			/* use netif name for the environment */

udevd.c

@@ -335,7 +335,7 @@ static void handle_udevsend_msg(int sock)
 		if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
 			msg->physdevpath = &key[12];
 	}
-	msg->envp[i++] = "MANAGED_EVENT=1";
+	msg->envp[i++] = "UDEVD_EVENT=1";
 	msg->envp[i] = NULL;
 
 	/* if no seqnum is given, we move straight to exec queue */

udevsend.c

@@ -154,7 +154,7 @@ int main(int argc, char *argv[], char *envp[])
 		}
 
 		/* prevent loops in the scripts we execute */
-		if (strncmp(key, "MANAGED_EVENT=", 14) == 0) {
+		if (strncmp(key, "UDEVD_EVENT=", 12) == 0) {
 			dbg("seems that the event source is not the kernel, just exit");
 			goto exit;
 		}