Re: [PATCH 4/4] net: Implement the per network namespace sysctl infrastructure

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Eric W. Biederman (ebiederm@xmission.com):
> 
> The user interface is: register_net_sysctl_table and
> unregister_net_sysctl_table.  Very much like the current
> interface except there is a network namespace parameter.
> 
> With this any sysctl registered with register_net_sysctl_table
> will only show up to tasks in the same network namespace.
> 
> All other sysctls continue to be globally visible.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> ---
>  include/net/net_namespace.h |    9 +++++++
>  net/sysctl_net.c            |   57 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 66 insertions(+), 0 deletions(-)
> 
> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index 4d0d634..235214c 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -25,6 +25,8 @@ struct net {
>  	struct proc_dir_entry 	*proc_net_stat;
>  	struct proc_dir_entry 	*proc_net_root;
> 
> +	struct list_head	sysctl_table_headers;
> +
>  	struct net_device       *loopback_dev;          /* The loopback */
> 
>  	struct list_head 	dev_base_head;
> @@ -144,4 +146,11 @@ extern void unregister_pernet_subsys(struct pernet_operations *);
>  extern int register_pernet_device(struct pernet_operations *);
>  extern void unregister_pernet_device(struct pernet_operations *);
> 
> +struct ctl_path;
> +struct ctl_table;
> +struct ctl_table_header;
> +extern struct ctl_table_header *register_net_sysctl_table(struct net *net,
> +	const struct ctl_path *path, struct ctl_table *table);
> +extern void unregister_net_sysctl_table(struct ctl_table_header *header);
> +
>  #endif /* __NET_NET_NAMESPACE_H */
> diff --git a/net/sysctl_net.c b/net/sysctl_net.c
> index cd4eafb..c50c793 100644
> --- a/net/sysctl_net.c
> +++ b/net/sysctl_net.c
> @@ -14,6 +14,7 @@
> 
>  #include <linux/mm.h>
>  #include <linux/sysctl.h>
> +#include <linux/nsproxy.h>
> 
>  #include <net/sock.h>
> 
> @@ -54,3 +55,59 @@ struct ctl_table net_table[] = {
>  #endif
>  	{ 0 },
>  };
> +
> +static struct list_head *
> +net_ctl_header_lookup(struct ctl_table_root *root, struct nsproxy *namespaces)
> +{
> +	return &namespaces->net_ns->sysctl_table_headers;
> +}
> +
> +static struct ctl_table_root net_sysctl_root = {
> +	.lookup = net_ctl_header_lookup,
> +};
> +
> +static int sysctl_net_init(struct net *net)
> +{
> +	INIT_LIST_HEAD(&net->sysctl_table_headers);
> +	return 0;
> +}
> +
> +static void sysctl_net_exit(struct net *net)
> +{
> +	WARN_ON(!list_empty(&net->sysctl_table_headers));
> +	return;
> +}
> +
> +static struct pernet_operations sysctl_pernet_ops = {
> +	.init = sysctl_net_init,
> +	.exit = sysctl_net_exit,
> +};
> +
> +static __init int sysctl_init(void)
> +{
> +	int ret;
> +	ret = register_pernet_subsys(&sysctl_pernet_ops);
> +	if (ret)
> +		goto out;
> +	register_sysctl_root(&net_sysctl_root);
> +out:
> +	return ret;
> +}
> +subsys_initcall(sysctl_init);
> +
> +struct ctl_table_header *register_net_sysctl_table(struct net *net,
> +	const struct ctl_path *path, struct ctl_table *table)
> +{
> +	struct nsproxy namespaces;
> +	namespaces = *current->nsproxy;
> +	namespaces.net_ns = net;
> +	return __register_sysctl_paths(&net_sysctl_root,
> +					&namespaces, path, table);

Hey Eric,

the patches look nice.

The hand-forcing of the passed-in net_ns into a copy of current->nsproxy
does make it seem like nsproxy may not be the best choice of what to
pass in.  Doesn't only net_sysctl_root->lookup() look at the argument?

But I assume you don't want to be more general than sending in a
nsproxy so as to dissuade abuse of this interface for needlessly complex
sysctl interfaces?

(Well I expect that'll become clear once the the patches using this
come out.)

Are you planning to use this infrastructure for the uts and ipc
sysctls as well?

thanks,
-serge

> +}
> +EXPORT_SYMBOL_GPL(register_net_sysctl_table);
> +
> +void unregister_net_sysctl_table(struct ctl_table_header *header)
> +{
> +	return unregister_sysctl_table(header);
> +}
> +EXPORT_SYMBOL_GPL(unregister_net_sysctl_table);
> -- 
> 1.5.3.rc6.17.g1911