First try at implementing current behaviour of unshare(1)

test

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+set -x
+
+NS_ROOT=${1?:Root not specified}
+N=$2
+
+python setup.py build || exit 1
+if [ ! -d ${NS_ROOT} ] ; then
+    sudo mkdir ${NS_ROOT}
+fi
+if [ "$(findmnt -n -o PROPAGATION ${NS_ROOT})" == "" ] ; then
+    sudo mount --bind ${NS_ROOT} ${NS_ROOT} 
+fi
+if [ "$(findmnt -n -o PROPAGATION ${NS_ROOT})" == "shared" ] ; then
+    sudo mount --make-private ${NS_ROOT} 
+fi
+
+sudo PYTHONPATH=build/lib.linux-x86_64-2.7/ ./test.py ${NS_ROOT} ${N}
+ls -li ${NS_ROOT}

test.py

@@ -0,0 +1,122 @@
+#!/usr/bin/python -u
+
+import unshare
+import time
+import sys
+import os
+import itertools
+import pickle
+
+kw_ns = dict(cgroup=unshare.CLONE_NEWCGROUP,
+             ipc=unshare.CLONE_NEWIPC,
+             mount=unshare.CLONE_NEWNS,
+             net=unshare.CLONE_NEWNET,
+             pid=unshare.CLONE_NEWPID,
+             user=unshare.CLONE_NEWUSER,
+             uts=unshare.CLONE_NEWUTS)
+
+flag_ns = (unshare.CLONE_FILES,
+           unshare.CLONE_FS,
+           unshare.CLONE_NEWCGROUP,
+           unshare.CLONE_NEWIPC,
+           unshare.CLONE_NEWNET,
+           unshare.CLONE_NEWNS,
+           unshare.CLONE_NEWPID,
+           unshare.CLONE_NEWUSER,
+           unshare.CLONE_NEWUTS,
+           unshare.CLONE_SIGHAND,
+           unshare.CLONE_SYSVSEM,
+           unshare.CLONE_THREAD,
+           unshare.CLONE_VM)
+
+def test(v):
+    flags = 0
+    kwpath = {}
+    for a in v:
+        if len(a) == 1:
+            flags |= a[0]
+        else:
+            kwpath[a[0]] = a[1];
+    for k in kwpath:
+        if os.path.exists(kwpath[k]) and unshare.get_nstype(kwpath[k]) != None:
+            unshare.unbind(kwpath[k], kw_ns[k])
+        open(kwpath[k], "w").close()
+    r,w = os.pipe()
+    r = os.fdopen(r)
+    w = os.fdopen(w, 'w')
+    pid = os.fork()
+    if pid != 0:
+        w.close()
+        ns1 = pickle.load(r)
+        ns2 = dict([ (k, os.stat("/proc/self/ns/%s" % (k)).st_ino)
+                     for k in os.listdir("/proc/self/ns") ])
+        pid, status = os.waitpid(pid, 0)
+        if status != 0:
+            print "%x %s failed" % (flags, kwpath)
+            raise(Exception)
+        else:
+            for k in ns1:
+                if k == 'pid':
+                    continue
+                def getpath():
+                    if k in kwpath:
+                        return kwpath[k]
+                    if k == 'mnt' and 'mount' in kwpath:
+                        return kwpath['mount']
+                    if k == 'pid_for_children' and 'pid' in kwpath:
+                        return kwpath['pid']
+                    return None
+                def getflags():
+                    if k in kw_ns:
+                        return kw_ns[k]
+                    if k == 'mnt':
+                        return kw_ns['mount']
+                    if k == 'pid_for_children':
+                        return kw_ns['pid']
+                    raise Exception(k)
+                path = getpath()
+                def error(msg):
+                    raise Exception("%s \n  %s \n  %s \n%x %s" % (
+                        msg, ns1, ns2, flags, kwpath))
+                if path != None:
+                    if ns1[k] != os.stat(path).st_ino:
+                        error("Wrong namespace saved in %s %d" % (
+                            path, os.stat(path).st_ino))
+                    if ns1[k] == ns2[k]:
+                        raise Exception("%s %s %s" % (k, ns1, ns2))
+                elif getflags() & flags == 0:
+                    if ns1[k] != ns2[k]:
+                        error("Namespaces not equal %s" % (k))
+                else:
+                     if ns1[k] == ns2[k]:
+                        error("Namespaces equal %s" % (k))
+    else:
+        r.close()
+        try:
+            unshare.unshare(flags, **kwpath)
+            ns = dict([ (k, os.stat("/proc/self/ns/%s" % (k)).st_ino)
+                        for k in os.listdir("/proc/self/ns") ])
+            pickle.dump(ns, w)
+            w.close()
+            os._exit(0)
+        except Exception, e:
+            print>>sys.stderr, e
+            os._exit(1)
+
+if __name__ == '__main__':
+    args = list([ (n, os.path.join(sys.argv[1], n)) for n in kw_ns ] +
+            [ (n,) for n in flag_ns ])
+    if len(sys.argv) >=3:
+        N = int(sys.argv[2])
+    else:
+        N = len(args)
+    unshare.unshare(unshare.CLONE_NEWNS) # Isolate test from systemd
+    for n in range(1, N + 1):
+        combinations = list(itertools.combinations(args, n))
+        print "n=%d/N=%d (%d combinations)" % (n, N, len(combinations))
+        for v in combinations:
+            try:
+                test(v)
+            except:
+                print "test(%s) failed" % (str(v))
+                raise