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SubjectRe: [PATCH 2/3] lib/kobject_uevent.c: add uevent forwarding function
On Tue, Sep 08, 2015 at 10:10:29PM -0400, Michael J. Coss wrote:
> Adds capability to allow userspace programs to forward a given event to
> a specific network namespace as determined by the provided pid. In
> addition, support for a per-namespace kobject_sequence counter was
> added. Sysfs was modified to return the correct event counter based on
> the current network namespace.
>
> Signed-off-by: Michael J. Coss <michael.coss@alcatel-lucent.com>
> ---
> include/linux/kobject.h | 3 ++
> include/net/net_namespace.h | 3 ++
> kernel/ksysfs.c | 12 ++++++
> lib/kobject_uevent.c | 90 +++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 108 insertions(+)
>
> diff --git a/include/linux/kobject.h b/include/linux/kobject.h
> index 637f670..d1bb509 100644
> --- a/include/linux/kobject.h
> +++ b/include/linux/kobject.h
> @@ -215,6 +215,9 @@ extern struct kobject *firmware_kobj;
> int kobject_uevent(struct kobject *kobj, enum kobject_action action);
> int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
> char *envp[]);
> +#if defined(CONFIG_UDEVNS) || defined(CONFIG_UDEVNS_MODULE)
> +int kobject_uevent_forward(char *buf, size_t len, pid_t pid);
> +#endif
>
> __printf(2, 3)
> int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...);
> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index e951453..a4013e5 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -134,6 +134,9 @@ struct net {
> #if IS_ENABLED(CONFIG_MPLS)
> struct netns_mpls mpls;
> #endif
> +#if defined(CONFIG_UDEVNS) || defined(CONFIG_UDEVNS_MODULE)
> + u64 kevent_seqnum;
> +#endif
> struct sock *diag_nlsk;
> atomic_t fnhe_genid;
> };
> diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
> index 6683cce..4bc15fd 100644
> --- a/kernel/ksysfs.c
> +++ b/kernel/ksysfs.c
> @@ -21,6 +21,9 @@
> #include <linux/compiler.h>
>
> #include <linux/rcupdate.h> /* rcu_expedited */
> +#if defined(CONFIG_UDEVNS) || defined(CONFIG_UDEVNS_MODULE)
> +#include <net/net_namespace.h>
> +#endif

#if isn't needed here, right?

>
> #define KERNEL_ATTR_RO(_name) \
> static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
> @@ -33,6 +36,15 @@ static struct kobj_attribute _name##_attr = \
> static ssize_t uevent_seqnum_show(struct kobject *kobj,
> struct kobj_attribute *attr, char *buf)
> {
> +#if defined(CONFIG_UDEVNS) || defined(CONFIG_UDEVNS_MODULE)
> + pid_t p = task_pid_vnr(current);
> + struct net *n = get_net_ns_by_pid(p);
> +
> + if (n != ERR_PTR(-ESRCH)) {
> + if (!net_eq(n, &init_net))
> + return sprintf(buf, "%llu\n", n->kevent_seqnum);
> + }
> +#endif
> return sprintf(buf, "%llu\n", (unsigned long long)uevent_seqnum);
> }
> KERNEL_ATTR_RO(uevent_seqnum);
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index d791e33..7589745 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -379,6 +379,96 @@ int kobject_uevent(struct kobject *kobj, enum kobject_action action)
> }
> EXPORT_SYMBOL_GPL(kobject_uevent);
>
> +#if defined(CONFIG_UDEVNS) || defined(CONFIG_UDEVNS_MODULE)
> +/**
> + * kobject_uevent_forward - forward event to specified network namespace
> + *
> + * @buf: event buffer
> + * @len: event length
> + * @pid: pid of network namespace
> + *
> + * Returns 0 if kobject_uevent_forward() is completed with success or the
> + * corresponding error when it fails.
> + */
> +int kobject_uevent_forward(char *buf, size_t len, pid_t pid)
> +{
> + int retval = 0;
> +#if defined(CONFIG_NET)
> + struct uevent_sock *ue_sk;
> + struct net *pns;
> + char *p;
> + u64 num;
> +
> + /* grab the network namespace of the provided pid */
> + pns = get_net_ns_by_pid(pid);
> + if (pns == ERR_PTR(-ESRCH))
> + return -ESRCH;
> +
> + /* find sequence number in buffer */
> + p = buf;
> + num = 0;
> + while (p < (buf + len)) {
> + if (strncmp(p, "SEQNUM=", 7) == 0) {
> + int r;
> +
> + p += 7;
> + r = kstrtoull(p, 10, &num);
> + if (r) {
> + put_net(pns);
> + return r;
> + }
> + break;
> + }
> + p += (strlen(p) + 1);
> + }

Ok, that's crazy, replacing an existing sequence number with a sequence
number of the namespace? An interesting hack, yes, but something we
want to maintain for the next 20+ years, no. Surely there's a better
way to do this?

But again, I'm not sold on this whole idea anyway.

greg k-h


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