proc: Usable inode numbers for the namespace file descriptors.
Assign a unique proc inode to each namespace, and use that
inode number to ensure we only allocate at most one proc
inode for every namespace in proc.
A single proc inode per namespace allows userspace to test
to see if two processes are in the same namespace.
This has been a long requested feature and only blocked because
a naive implementation would put the id in a global space and
would ultimately require having a namespace for the names of
namespaces, making migration and certain virtualization tricks
impossible.
We still don't have per superblock inode numbers for proc, which
appears necessary for application unaware checkpoint/restart and
migrations (if the application is using namespace file descriptors)
but that is now allowd by the design if it becomes important.
I have preallocated the ipc and uts initial proc inode numbers so
their structures can be statically initialized.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index ec2870b..2e9a313 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -381,6 +381,21 @@
}
EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
+static __net_init int net_ns_net_init(struct net *net)
+{
+ return proc_alloc_inum(&net->proc_inum);
+}
+
+static __net_exit void net_ns_net_exit(struct net *net)
+{
+ proc_free_inum(net->proc_inum);
+}
+
+static struct pernet_operations __net_initdata net_ns_ops = {
+ .init = net_ns_net_init,
+ .exit = net_ns_net_exit,
+};
+
static int __init net_ns_init(void)
{
struct net_generic *ng;
@@ -412,6 +427,8 @@
mutex_unlock(&net_mutex);
+ register_pernet_subsys(&net_ns_ops);
+
return 0;
}
@@ -640,11 +657,18 @@
return 0;
}
+static unsigned int netns_inum(void *ns)
+{
+ struct net *net = ns;
+ return net->proc_inum;
+}
+
const struct proc_ns_operations netns_operations = {
.name = "net",
.type = CLONE_NEWNET,
.get = netns_get,
.put = netns_put,
.install = netns_install,
+ .inum = netns_inum,
};
#endif