tun: send netlink notification when the device is modified

I added dumping of link information about tun devices over netlink in
commit 1ec010e7 ("tun: export flags, uid, gid, queue information
over netlink"), but didn't add the missing netlink notifications when
the device's exported properties change.

This patch adds notifications when owner/group or flags are modified,
when queues are attached/detached, and when a tun fd is closed.
Reported-by: NThomas Haller <thaller@redhat.com>
Fixes: 1ec010e7 ("tun: export flags, uid, gid, queue information over netlink")
Signed-off-by: NSabrina Dubroca <sd@queasysnail.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -743,8 +743,15 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
 
 static void tun_detach(struct tun_file *tfile, bool clean)
 {
+	struct tun_struct *tun;
+	struct net_device *dev;
+
 	rtnl_lock();
+	tun = rtnl_dereference(tfile->tun);
+	dev = tun ? tun->dev : NULL;
 	__tun_detach(tfile, clean);
+	if (dev)
+		netdev_state_change(dev);
 	rtnl_unlock();
 }
 
@@ -2562,13 +2569,15 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 			/* One or more queue has already been attached, no need
 			 * to initialize the device again.
 			 */
+			netdev_state_change(dev);
 			return 0;
 		}
 
 		tun->flags = (tun->flags & ~TUN_FEATURES) |
 			      (ifr->ifr_flags & TUN_FEATURES);
-	}
-	else {
+
+		netdev_state_change(dev);
+	} else {
 		char *name;
 		unsigned long flags = 0;
 		int queues = ifr->ifr_flags & IFF_MULTI_QUEUE ?
@@ -2808,6 +2817,9 @@ static int tun_set_queue(struct file *file, struct ifreq *ifr)
 	} else
 		ret = -EINVAL;
 
+	if (ret >= 0)
+		netdev_state_change(tun->dev);
+
 unlock:
 	rtnl_unlock();
 	return ret;
@@ -2848,6 +2860,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 	unsigned int ifindex;
 	int le;
 	int ret;
+	bool do_notify = false;
 
 	if (cmd == TUNSETIFF || cmd == TUNSETQUEUE ||
 	    (_IOC_TYPE(cmd) == SOCK_IOC_TYPE && cmd != SIOCGSKNS)) {
@@ -2944,10 +2957,12 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 		if (arg && !(tun->flags & IFF_PERSIST)) {
 			tun->flags |= IFF_PERSIST;
 			__module_get(THIS_MODULE);
+			do_notify = true;
 		}
 		if (!arg && (tun->flags & IFF_PERSIST)) {
 			tun->flags &= ~IFF_PERSIST;
 			module_put(THIS_MODULE);
+			do_notify = true;
 		}
 
 		tun_debug(KERN_INFO, tun, "persist %s\n",
@@ -2962,6 +2977,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 			break;
 		}
 		tun->owner = owner;
+		do_notify = true;
 		tun_debug(KERN_INFO, tun, "owner set to %u\n",
 			  from_kuid(&init_user_ns, tun->owner));
 		break;
@@ -2974,6 +2990,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 			break;
 		}
 		tun->group = group;
+		do_notify = true;
 		tun_debug(KERN_INFO, tun, "group set to %u\n",
 			  from_kgid(&init_user_ns, tun->group));
 		break;
@@ -3133,6 +3150,9 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 		break;
 	}
 
+	if (do_notify)
+		netdev_state_change(tun->dev);
+
 unlock:
 	rtnl_unlock();
 	if (tun)