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Date: Thu, 27 Sep 2007 10:51:42 +0200
From: Cedric Le Goater <clg@...ibm.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
CC: David Miller <davem@...emloft.net>,
Linux Containers <containers@...ts.osdl.org>,
netdev@...r.kernel.org
Subject: Re: [PATCH] net: Add network namespace clone & unshare support.
Eric W. Biederman wrote:
> This patch allows you to create a new network namespace
> using sys_clone, or sys_unshare.
>
> As the network namespace is still experimental and under development
> clone and unshare support is only made available when CONFIG_NET_NS is
> selected at compile time.
>
> As this patch introduces network namespace support into code paths
> that exist when the CONFIG_NET is not selected there are a few
> additions made to net_namespace.h to allow a few more functions
> to be used when the networking stack is not compiled in.
>
> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> ---
> include/linux/sched.h | 1 +
> include/net/net_namespace.h | 18 ++++++++++++++++++
> kernel/fork.c | 3 ++-
> kernel/nsproxy.c | 15 +++++++++++++--
> net/Kconfig | 8 ++++++++
> net/core/net_namespace.c | 43 +++++++++++++++++++++++++++++++++++++++++--
> 6 files changed, 83 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index a01ac6d..e10a0a8 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -27,6 +27,7 @@
> #define CLONE_NEWUTS 0x04000000 /* New utsname group? */
> #define CLONE_NEWIPC 0x08000000 /* New ipcs */
> #define CLONE_NEWUSER 0x10000000 /* New user namespace */
> +#define CLONE_NEWNET 0x20000000 /* New network namespace */
This new flag is going to conflict with the pid namespace flag
CLONE_NEWPID in -mm. It might be worth changing it to:
#define CLONE_NEWNET 0x40000000
The changes in nxproxy.c and fork.c will also conflict but I don't
think we can do much about it for now.
C.
> /*
> * Scheduling policies
> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index ac8f830..3ea4194 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -38,11 +38,23 @@ extern struct net init_net;
>
> extern struct list_head net_namespace_list;
>
> +#ifdef CONFIG_NET
> +extern struct net *copy_net_ns(unsigned long flags, struct net *net_ns);
> +#else
> +static inline struct net *copy_net_ns(unsigned long flags, struct net *net_ns)
> +{
> + /* There is nothing to copy so this is a noop */
> + return net_ns;
> +}
> +#endif
> +
> extern void __put_net(struct net *net);
>
> static inline struct net *get_net(struct net *net)
> {
> +#ifdef CONFIG_NET
> atomic_inc(&net->count);
> +#endif
> return net;
> }
>
> @@ -60,19 +72,25 @@ static inline struct net *maybe_get_net(struct net *net)
>
> static inline void put_net(struct net *net)
> {
> +#ifdef CONFIG_NET
> if (atomic_dec_and_test(&net->count))
> __put_net(net);
> +#endif
> }
>
> static inline struct net *hold_net(struct net *net)
> {
> +#ifdef CONFIG_NET
> atomic_inc(&net->use_count);
> +#endif
> return net;
> }
>
> static inline void release_net(struct net *net)
> {
> +#ifdef CONFIG_NET
> atomic_dec(&net->use_count);
> +#endif
> }
>
> extern void net_lock(void);
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 33f12f4..5e67f90 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1608,7 +1608,8 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
> err = -EINVAL;
> if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
> CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
> - CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER))
> + CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
> + CLONE_NEWNET))
> goto bad_unshare_out;
>
> if ((err = unshare_thread(unshare_flags)))
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index a4fb7d4..f1decd2 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>
>
> static struct kmem_cache *nsproxy_cachep;
>
> @@ -98,8 +99,17 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
> goto out_user;
> }
>
> + new_nsp->net_ns = copy_net_ns(flags, tsk->nsproxy->net_ns);
> + if (IS_ERR(new_nsp->net_ns)) {
> + err = PTR_ERR(new_nsp->net_ns);
> + goto out_net;
> + }
> +
> return new_nsp;
>
> +out_net:
> + if (new_nsp->user_ns)
> + put_user_ns(new_nsp->user_ns);
> out_user:
> if (new_nsp->pid_ns)
> put_pid_ns(new_nsp->pid_ns);
> @@ -132,7 +142,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
>
> get_nsproxy(old_ns);
>
> - if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWUSER)))
> + if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWUSER | CLONE_NEWNET)))
> return 0;
>
> if (!capable(CAP_SYS_ADMIN)) {
> @@ -164,6 +174,7 @@ void free_nsproxy(struct nsproxy *ns)
> put_pid_ns(ns->pid_ns);
> if (ns->user_ns)
> put_user_ns(ns->user_ns);
> + put_net(ns->net_ns);
> kmem_cache_free(nsproxy_cachep, ns);
> }
>
> @@ -177,7 +188,7 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
> int err = 0;
>
> if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
> - CLONE_NEWUSER)))
> + CLONE_NEWUSER | CLONE_NEWNET)))
> return 0;
>
> if (!capable(CAP_SYS_ADMIN))
> diff --git a/net/Kconfig b/net/Kconfig
> index cdba08c..ab4e6da 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -27,6 +27,14 @@ if NET
>
> menu "Networking options"
>
> +config NET_NS
> + bool "Network namespace support"
> + default n
> + depends on EXPERIMENTAL && !SYSFS
> + help
> + Allow user space to create what appear to be multiple instances
> + of the network stack.
> +
> source "net/packet/Kconfig"
> source "net/unix/Kconfig"
> source "net/xfrm/Kconfig"
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 0e6cb02..e478e35 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -4,6 +4,7 @@
> #include <linux/slab.h>
> #include <linux/list.h>
> #include <linux/delay.h>
> +#include <linux/sched.h>
> #include <net/net_namespace.h>
>
> /*
> @@ -32,12 +33,10 @@ void net_unlock(void)
> mutex_unlock(&net_list_mutex);
> }
>
> -#if 0
> static struct net *net_alloc(void)
> {
> return kmem_cache_alloc(net_cachep, GFP_KERNEL);
> }
> -#endif
>
> static void net_free(struct net *net)
> {
> @@ -128,6 +127,46 @@ out_undo:
> goto out;
> }
>
> +struct net *copy_net_ns(unsigned long flags, struct net *old_net)
> +{
> + struct net *new_net = NULL;
> + int err;
> +
> + get_net(old_net);
> +
> + if (!(flags & CLONE_NEWNET))
> + return old_net;
> +
> +#ifndef CONFIG_NET_NS
> + return ERR_PTR(-EINVAL);
> +#endif
> +
> + err = -ENOMEM;
> + new_net = net_alloc();
> + if (!new_net)
> + goto out;
> +
> + mutex_lock(&net_mutex);
> + err = setup_net(new_net);
> + if (err)
> + goto out_unlock;
> +
> + net_lock();
> + list_add_tail(&new_net->list, &net_namespace_list);
> + net_unlock();
> +
> +
> +out_unlock:
> + mutex_unlock(&net_mutex);
> +out:
> + put_net(old_net);
> + if (err) {
> + net_free(new_net);
> + new_net = ERR_PTR(err);
> + }
> + return new_net;
> +}
> +
> static int __init net_ns_init(void)
> {
> int err;
-
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