[NET]: Factor out __dev_alloc_name from dev_alloc_name

When forcibly changing the network namespace of a device
I need something that can generate a name for the device
in the new namespace without overwriting the old name.

__dev_alloc_name provides me that functionality.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 13 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 3a3d5ee73909..520ef7b20862 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -739,9 +739,10 @@ int dev_valid_name(const char *name)
 }
 
 /**
- *      dev_alloc_name - allocate a name for a device
- *      @dev: device
+ *      __dev_alloc_name - allocate a name for a device
+ *      @net: network namespace to allocate the device name in
  *      @name: name format string
+ *      @buf:  scratch buffer and result name string
  *
  *      Passed a format string - eg "lt%d" it will try and find a suitable
  *      id. It scans list of devices to build up a free map, then chooses
@@ -752,18 +753,13 @@ int dev_valid_name(const char *name)
  *      Returns the number of the unit assigned or a negative errno code.
  */
 
-int dev_alloc_name(struct net_device *dev, const char *name)
+static int __dev_alloc_name(struct net *net, const char *name, char *buf)
 {
         int i = 0;
-        char buf[IFNAMSIZ];
         const char *p;
         const int max_netdevices = 8*PAGE_SIZE;
         long *inuse;
         struct net_device *d;
-        struct net *net;
-
-        BUG_ON(!dev->nd_net);
-        net = dev->nd_net;
 
         p = strnchr(name, IFNAMSIZ-1, '%');
         if (p) {
@@ -787,7 +783,7 @@ int dev_alloc_name(struct net_device *dev, const char *name)
                                 continue;
 
                         /*  avoid cases where sscanf is not exact inverse of printf */
-                        snprintf(buf, sizeof(buf), name, i);
+                        snprintf(buf, IFNAMSIZ, name, i);
                         if (!strncmp(buf, d->name, IFNAMSIZ))
                                 set_bit(i, inuse);
                 }
@@ -796,11 +792,9 @@ int dev_alloc_name(struct net_device *dev, const char *name)
                 free_page((unsigned long) inuse);
         }
 
-        snprintf(buf, sizeof(buf), name, i);
-        if (!__dev_get_by_name(net, buf)) {
-                strlcpy(dev->name, buf, IFNAMSIZ);
+        snprintf(buf, IFNAMSIZ, name, i);
+        if (!__dev_get_by_name(net, buf))
                 return i;
-        }
 
         /* It is possible to run out of possible slots
          * when the name is long and there isn't enough space left
@@ -809,6 +803,34 @@ int dev_alloc_name(struct net_device *dev, const char *name)
         return -ENFILE;
 }
 
+/**
+ *      dev_alloc_name - allocate a name for a device
+ *      @dev: device
+ *      @name: name format string
+ *
+ *      Passed a format string - eg "lt%d" it will try and find a suitable
+ *      id. It scans list of devices to build up a free map, then chooses
+ *      the first empty slot. The caller must hold the dev_base or rtnl lock
+ *      while allocating the name and adding the device in order to avoid
+ *      duplicates.
+ *      Limited to bits_per_byte * page size devices (ie 32K on most platforms).
+ *      Returns the number of the unit assigned or a negative errno code.
+ */
+
+int dev_alloc_name(struct net_device *dev, const char *name)
+{
+        char buf[IFNAMSIZ];
+        struct net *net;
+        int ret;
+
+        BUG_ON(!dev->nd_net);
+        net = dev->nd_net;
+        ret = __dev_alloc_name(net, name, buf);
+        if (ret >= 0)
+                strlcpy(dev->name, buf, IFNAMSIZ);
+        return ret;
+}
+
 
 /**
  *      dev_change_name - change name of a device