From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 include/linux/nsproxy.h | 85 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 include/linux/nsproxy.h

(limited to 'include/linux/nsproxy.h')

diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
new file mode 100644
index 000000000..35fa08fd7
--- /dev/null
+++ b/include/linux/nsproxy.h
@@ -0,0 +1,85 @@
+#ifndef _LINUX_NSPROXY_H
+#define _LINUX_NSPROXY_H
+
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+
+struct mnt_namespace;
+struct uts_namespace;
+struct ipc_namespace;
+struct pid_namespace;
+struct fs_struct;
+
+/*
+ * A structure to contain pointers to all per-process
+ * namespaces - fs (mount), uts, network, sysvipc, etc.
+ *
+ * The pid namespace is an exception -- it's accessed using
+ * task_active_pid_ns.  The pid namespace here is the
+ * namespace that children will use.
+ *
+ * 'count' is the number of tasks holding a reference.
+ * The count for each namespace, then, will be the number
+ * of nsproxies pointing to it, not the number of tasks.
+ *
+ * The nsproxy is shared by tasks which share all namespaces.
+ * As soon as a single namespace is cloned or unshared, the
+ * nsproxy is copied.
+ */
+struct nsproxy {
+	atomic_t count;
+	struct uts_namespace *uts_ns;
+	struct ipc_namespace *ipc_ns;
+	struct mnt_namespace *mnt_ns;
+	struct pid_namespace *pid_ns_for_children;
+	struct net 	     *net_ns;
+};
+extern struct nsproxy init_nsproxy;
+
+/*
+ * the namespaces access rules are:
+ *
+ *  1. only current task is allowed to change tsk->nsproxy pointer or
+ *     any pointer on the nsproxy itself.  Current must hold the task_lock
+ *     when changing tsk->nsproxy.
+ *
+ *  2. when accessing (i.e. reading) current task's namespaces - no
+ *     precautions should be taken - just dereference the pointers
+ *
+ *  3. the access to other task namespaces is performed like this
+ *     task_lock(task);
+ *     nsproxy = task->nsproxy;
+ *     if (nsproxy != NULL) {
+ *             / *
+ *               * work with the namespaces here
+ *               * e.g. get the reference on one of them
+ *               * /
+ *     } / *
+ *         * NULL task->nsproxy means that this task is
+ *         * almost dead (zombie)
+ *         * /
+ *     task_unlock(task);
+ *
+ */
+
+int copy_namespaces(unsigned long flags, struct task_struct *tsk);
+void exit_task_namespaces(struct task_struct *tsk);
+void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
+void free_nsproxy(struct nsproxy *ns);
+int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
+	struct cred *, struct fs_struct *);
+int __init nsproxy_cache_init(void);
+
+static inline void put_nsproxy(struct nsproxy *ns)
+{
+	if (atomic_dec_and_test(&ns->count)) {
+		free_nsproxy(ns);
+	}
+}
+
+static inline void get_nsproxy(struct nsproxy *ns)
+{
+	atomic_inc(&ns->count);
+}
+
+#endif
-- 
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