[Devel] [PATCH RFC 17/31] net: Factor out __dev_alloc_name from dev_alloc_name

[Eric W. Biederman]

From: Eric W. Biederman <ebiederm at xmission.com> - unquoted

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 at xmission.com>
---
 net/core/dev.c |   44 +++++++++++++++++++++++++++++++++-----------
 1 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 32fe905..fc0d2af 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -655,9 +655,10 @@ 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
@@ -668,18 +669,13 @@ 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(net_t net, const char *name, char buf[IFNAMSIZ])
 {
 	int i = 0;
-	char buf[IFNAMSIZ];
 	const char *p;
 	const int max_netdevices = 8*PAGE_SIZE;
 	long *inuse;
 	struct net_device *d;
-	net_t net;
-
-	BUG_ON(null_net(dev->nd_net));
-	net = dev->nd_net;
 
 	p = strnchr(name, IFNAMSIZ-1, '%');
 	if (p) {
@@ -713,10 +709,8 @@ int dev_alloc_name(struct net_device *dev, const char *name)
 	}
 
 	snprintf(buf, sizeof(buf), name, i);
-	if (!__dev_get_by_name(net, buf)) {
-		strlcpy(dev->name, buf, IFNAMSIZ);
+	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
@@ -725,6 +719,34 @@ 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];
+	net_t net;
+	int ret;
+
+	BUG_ON(null_net(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
-- 
1.4.4.1.g278f

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