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

In combination with the sysfs support I am in the process of merging
with gregkh, creates a separate instance of the /sys/class/net directory
for each network namespace so two devices with the same name do not conflict.
Then a network namespace sensitive follow link method on the /sys/class/net
directory ensures that you see the directory instance for your current network
namespace.

Ensuring all existing applications continue to see what we is currently
present in sysfs.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 net/core/net-sysfs.c |   53 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 52 insertions(+), 1 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 5d08cc9..b08c1be 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -11,12 +11,14 @@
 
 #include <linux/capability.h>
 #include <linux/kernel.h>
+#include <linux/sysfs.h>
 #include <linux/netdevice.h>
 #include <linux/if_arp.h>
 #include <net/sock.h>
 #include <linux/rtnetlink.h>
 #include <linux/wireless.h>
 #include <net/iw_handler.h>
+#include <net/net_namespace.h>
 
 #define to_class_dev(obj) container_of(obj,struct class_device,kobj)
 #define to_net_dev(class) container_of(class, struct net_device, class_dev)
@@ -431,6 +433,24 @@ static void netdev_release(struct class_device *cd)
 	kfree((char *)dev - dev->padded);
 }
 
+static DEFINE_PER_NET(struct dentry *, net_shadow) = NULL;
+
+static struct dentry *net_class_device_dparent(struct class_device *cd)
+{
+	struct net_device *dev
+		= container_of(cd, struct net_device, class_dev);
+	net_t net = dev->nd_net;
+
+	return per_net(net_shadow, net);
+}
+
+static void *class_net_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+	dput(nd->dentry);
+	nd->dentry = dget(per_net(net_shadow, current->nsproxy->net_ns));
+	return NULL;
+}
+
 static struct class net_class = {
 	.name = "net",
 	.release = netdev_release,
@@ -438,6 +458,8 @@ static struct class net_class = {
 #ifdef CONFIG_HOTPLUG
 	.uevent = netdev_uevent,
 #endif
+	.class_device_dparent	= net_class_device_dparent,
+	.class_follow_link	= class_net_follow_link,
 };
 
 void netdev_unregister_sysfs(struct net_device * dev)
@@ -470,7 +492,36 @@ int netdev_register_sysfs(struct net_device *dev)
 	return class_device_add(class_dev);
 }
 
+static int netdev_sysfs_net_init(net_t net)
+{
+	struct dentry *shadow;
+	int error = 0;
+	shadow = sysfs_create_shadow_dir(&net_class.subsys.kset.kobj);
+	if (IS_ERR(shadow))
+		error = PTR_ERR(shadow);
+	else
+		per_net(net_shadow, net) = shadow;
+	return error;
+}
+
+static void netdev_sysfs_net_exit(net_t net)
+{
+	sysfs_remove_shadow_dir(per_net(net_shadow, net));
+	per_net(net_shadow, net) = NULL;
+}
+
+static struct pernet_operations netdev_sysfs_ops = {
+	.init = netdev_sysfs_net_init,
+	.exit = netdev_sysfs_net_exit,
+};
+ 
 int netdev_sysfs_init(void)
 {
-	return class_register(&net_class);
+	int rc;
+	if ((rc = class_register(&net_class)))
+		goto out;
+	if ((rc = register_pernet_subsys(&netdev_sysfs_ops)))
+		goto out;
+out:
+	return rc;
 }
-- 
1.4.4.1.g278f

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