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Subject[patch 4/4] Network namespaces: playing and debugging
Temporary code to play with network namespaces in the simplest way.
Do
exec 7< /proc/net/net_ns
in your bash shell and you'll get a brand new network namespace.
There you can, for example, do
ip link set lo up
ip addr list
ip addr add 1.2.3.4 dev lo
ping -n 1.2.3.4

Signed-off-by: Andrey Savochkin <saw@swsoft.com>
---
dev.c | 27 ++++++++++++++++++++++++++-
1 files changed, 26 insertions, 1 deletion
--- ./net/core/dev.c.vensdbg Fri Jun 23 11:50:16 2006
+++ ./net/core/dev.c Fri Jun 23 11:50:40 2006
@@ -3444,6 +3444,8 @@ int net_ns_start(void)
if (err)
goto out_register;
put_net_ns(orig_ns);
+ printk(KERN_DEBUG "NET_NS: created new netcontext %p for %s (pid=%d)\n",
+ ns, task->comm, task->tgid);
return 0;

out_register:
@@ -3461,6 +3463,7 @@ EXPORT_SYMBOL(net_ns_start);

void net_ns_free(struct net_namespace *ns)
{
+ printk(KERN_DEBUG "NET_NS: netcontext %p freed\n", ns);
kfree(ns);
}
EXPORT_SYMBOL(net_ns_free);
@@ -3473,8 +3476,13 @@ static void net_ns_destroy(void *data)
ns = data;
push_net_ns(ns, orig_ns);
unregister_netdev(ns->loopback);
+ if (!list_empty(&ns->dev_base)) {
+ printk("NET_NS: BUG: context %p has devices! ref %d\n",
+ ns, atomic_read(&ns->active_ref));
+ pop_net_ns(orig_ns);
+ return;
+ }
ip_fib_struct_fini();
- BUG_ON(!list_empty(&ns->dev_base));
pop_net_ns(orig_ns);

/* drop (hopefully) final reference */
@@ -3483,9 +3491,23 @@ static void net_ns_destroy(void *data)

void net_ns_stop(struct net_namespace *ns)
{
+ printk(KERN_DEBUG "NET_NS: netcontext %p scheduled for stop\n", ns);
execute_in_process_context(net_ns_destroy, ns, &ns->destroy_work);
}
EXPORT_SYMBOL(net_ns_stop);
+
+static int net_ns_open(struct inode *i, struct file *f)
+{
+ return net_ns_start();
+}
+static struct file_operations net_ns_fops = {
+ .open = net_ns_open,
+};
+static int net_ns_init(void)
+{
+ return proc_net_fops_create("net_ns", S_IRWXU, &net_ns_fops)
+ ? 0 : -ENOMEM;
+}
#endif

/*
@@ -3550,6 +3572,9 @@ static int __init net_dev_init(void)
hotcpu_notifier(dev_cpu_callback, 0);
dst_init();
dev_mcast_init();
+#ifdef CONFIG_NET_NS
+ net_ns_init();
+#endif
rc = 0;
out:
return rc;
-
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