net: introduce a function to check if a netdev name is in use

__dev_get_by_name is currently used to either retrieve a net device
reference using its name or to check if a name is already used by a
registered net device (per ns). In the later case there is no need to
return a reference to a net device.

Introduce a new helper, netdev_name_in_use, to check if a name is
currently used by a registered net device without leaking a reference
the corresponding net device. This helper uses netdev_name_node_lookup
instead of __dev_get_by_name as we don't need the extra logic retrieving
a reference to the corresponding net device.

Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d791632..15f4a65 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2955,6 +2955,7 @@ struct net_device *__dev_get_by_flags(struct net *net, unsigned short flags,
 struct net_device *dev_get_by_name(struct net *net, const char *name);
 struct net_device *dev_get_by_name_rcu(struct net *net, const char *name);
 struct net_device *__dev_get_by_name(struct net *net, const char *name);
+bool netdev_name_in_use(struct net *net, const char *name);
 int dev_alloc_name(struct net_device *dev, const char *name);
 int dev_open(struct net_device *dev, struct netlink_ext_ack *extack);
 void dev_close(struct net_device *dev);

diff --git a/net/core/dev.c b/net/core/dev.c
index 16ab09b..1594cd2 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -303,6 +303,12 @@ static struct netdev_name_node *netdev_name_node_lookup_rcu(struct net *net,
        return NULL;
 }
 
+bool netdev_name_in_use(struct net *net, const char *name)
+{
+       return netdev_name_node_lookup(net, name);
+}
+EXPORT_SYMBOL(netdev_name_in_use);
+
 int netdev_name_node_alt_create(struct net_device *dev, const char *name)
 {
        struct netdev_name_node *name_node;
@@ -1133,7 +1139,7 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
        }
 
        snprintf(buf, IFNAMSIZ, name, i);
-       if (!__dev_get_by_name(net, buf))
+       if (!netdev_name_in_use(net, buf))
                return i;
 
        /* It is possible to run out of possible slots
@@ -1187,7 +1193,7 @@ static int dev_get_valid_name(struct net *net, struct net_device *dev,
 
        if (strchr(name, '%'))
                return dev_alloc_name_ns(net, dev, name);
-       else if (__dev_get_by_name(net, name))
+       else if (netdev_name_in_use(net, name))
                return -EEXIST;
        else if (dev->name != name)
                strlcpy(dev->name, name, IFNAMSIZ);
@@ -11153,7 +11159,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
         * we can use it in the destination network namespace.
         */
        err = -EEXIST;
-       if (__dev_get_by_name(net, dev->name)) {
+       if (netdev_name_in_use(net, dev->name)) {
                /* We get here if we can't use the current device name */
                if (!pat)
                        goto out;
@@ -11506,7 +11512,7 @@ static void __net_exit default_device_exit(struct net *net)
 
                /* Push remaining network devices to init_net */
                snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
-               if (__dev_get_by_name(&init_net, fb_name))
+               if (netdev_name_in_use(&init_net, fb_name))
                        snprintf(fb_name, IFNAMSIZ, "dev%%d");
                err = dev_change_net_namespace(dev, &init_net, fb_name);
                if (err) {