net: rename sysfs symlinks on device name change

Currently, we don't rename the upper/lower_ifc symlinks in
/sys/class/net/*/ , which might result stale/duplicate links/names.

Fix this by adding netdev_adjacent_rename_links(dev, oldname) which renames
all the upper/lower interface's links to dev from the upper/lower_oldname
to the new name.

We don't need a rollback because only we control these symlinks and if we
fail to rename them - sysfs will anyway complain.
Reported-by: Ding Tianhong <dingtianhong@huawei.com>
CC: Ding Tianhong <dingtianhong@huawei.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <edumazet@google.com>
CC: Nicolas Dichtel <nicolas.dichtel@6wind.com>
CC: Cong Wang <amwang@redhat.com>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -2941,6 +2941,7 @@ int netdev_master_upper_dev_link_private(struct net_device *dev,
 					 void *private);
 void netdev_upper_dev_unlink(struct net_device *dev,
 			     struct net_device *upper_dev);
+void netdev_adjacent_rename_links(struct net_device *dev, char *oldname);
 void *netdev_lower_dev_get_private(struct net_device *dev,
 				   struct net_device *lower_dev);
 int skb_checksum_help(struct sk_buff *skb);

net/core/dev.c

@@ -1119,6 +1119,8 @@ int dev_change_name(struct net_device *dev, const char *newname)
 
 	write_seqcount_end(&devnet_rename_seq);
 
+	netdev_adjacent_rename_links(dev, oldname);
+
 	write_lock_bh(&dev_base_lock);
 	hlist_del_rcu(&dev->name_hlist);
 	write_unlock_bh(&dev_base_lock);
@@ -1138,6 +1140,7 @@ int dev_change_name(struct net_device *dev, const char *newname)
 			err = ret;
 			write_seqcount_begin(&devnet_rename_seq);
 			memcpy(dev->name, oldname, IFNAMSIZ);
+			memcpy(oldname, newname, IFNAMSIZ);
 			goto rollback;
 		} else {
 			pr_err("%s: name change rollback failed: %d\n",
@@ -4999,6 +5002,25 @@ void netdev_upper_dev_unlink(struct net_device *dev,
 }
 EXPORT_SYMBOL(netdev_upper_dev_unlink);
 
+void netdev_adjacent_rename_links(struct net_device *dev, char *oldname)
+{
+	struct netdev_adjacent *iter;
+
+	list_for_each_entry(iter, &dev->adj_list.upper, list) {
+		netdev_adjacent_sysfs_del(iter->dev, oldname,
+					  &iter->dev->adj_list.lower);
+		netdev_adjacent_sysfs_add(iter->dev, dev,
+					  &iter->dev->adj_list.lower);
+	}
+
+	list_for_each_entry(iter, &dev->adj_list.lower, list) {
+		netdev_adjacent_sysfs_del(iter->dev, oldname,
+					  &iter->dev->adj_list.upper);
+		netdev_adjacent_sysfs_add(iter->dev, dev,
+					  &iter->dev->adj_list.upper);
+	}
+}
+
 void *netdev_lower_dev_get_private(struct net_device *dev,
 				   struct net_device *lower_dev)
 {