[PATCH RFC 22/31] net: Add network namespace clone support.

[Daniel Lezcano]

Eric W. Biederman wrote:
> From: Eric W. Biederman <ebiederm at xmission.com> - unquoted
>
> This patch allows you to create a new network namespace
> using sys_clone(...).
>
> Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
> ---
>  include/linux/sched.h    |    1 +
>  kernel/nsproxy.c         |   11 +++++++++++
>  net/core/net_namespace.c |   38 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 50 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 4463735..9e0f91a 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -26,6 +26,7 @@
>  #define CLONE_STOPPED		0x02000000	/* Start in stopped state */
>  #define CLONE_NEWUTS		0x04000000	/* New utsname group? */
>  #define CLONE_NEWIPC		0x08000000	/* New ipcs */
> +#define CLONE_NEWNET		0x20000000	/* New network namespace */
>
>  /*
>   * Scheduling policies
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 4f3c95a..7861c4c 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -20,6 +20,7 @@
>  #include <linux/mnt_namespace.h>
>  #include <linux/utsname.h>
>  #include <linux/pid_namespace.h>
> +#include <net/net_namespace.h>
>
>  struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
>  EXPORT_SYMBOL_GPL(init_nsproxy);
> @@ -70,6 +71,7 @@ struct nsproxy *dup_namespaces(struct nsproxy *orig)
>  			get_ipc_ns(ns->ipc_ns);
>  		if (ns->pid_ns)
>  			get_pid_ns(ns->pid_ns);
> +		get_net(ns->net_ns);
>  	}
>
>  	return ns;
> @@ -117,10 +119,18 @@ int copy_namespaces(int flags, struct task_struct *tsk)
>  	if (err)
>  		goto out_pid;
>
> +	err = copy_net(flags, tsk);
> +	if (err)
> +		goto out_net;
> +
>  out:
>  	put_nsproxy(old_ns);
>  	return err;
>
> +out_net:
> +	if (new_ns->pid_ns)
> +		put_pid_ns(new_ns->pid_ns);
> +
>  out_pid:
>  	if (new_ns->ipc_ns)
>  		put_ipc_ns(new_ns->ipc_ns);
> @@ -146,5 +156,6 @@ void free_nsproxy(struct nsproxy *ns)
>  		put_ipc_ns(ns->ipc_ns);
>  	if (ns->pid_ns)
>  		put_pid_ns(ns->pid_ns);
> +	put_net(ns->net_ns);
>  	kfree(ns);
>  }
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 93e3879..cc56105 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -175,6 +175,44 @@ out_undo:
>  	goto out;
>  }
>
> +int copy_net(int flags, struct task_struct *tsk)
> +{
> +	net_t old_net = tsk->nsproxy->net_ns;
> +	net_t new_net;
> +	int err;
> +
> +	get_net(old_net);
> +
> +	if (!(flags & CLONE_NEWNET))
> +		return 0;
> +
> +	err = -EPERM;
> +	if (!capable(CAP_SYS_ADMIN))
> +		goto out;
> +
> +	err = -ENOMEM;
> +	new_net = net_alloc();
> +	if (null_net(new_net))
> +		goto out;
> +
> +	mutex_lock(&net_mutex);
> +	err = setup_net(new_net);
> +	if (err)
> +		goto out_unlock;
>   
Should we "net_free" in case of error ?
> +
> +	net_lock();
> +	net_list_append(new_net);
> +	net_unlock();
> +
> +	tsk->nsproxy->net_ns = new_net;
> +
> +out_unlock:
> +	mutex_unlock(&net_mutex);
> +out:
> +	put_net(old_net);
> +	return err;
> +}
> +
>  void pernet_modcopy(void *pnetdst, const void *src, unsigned long size)
>  {
>  	net_t net;
>