#!/usr/bin/python


import setns
import os
import sys

#from optparse import OptionParser

drop_capabilities='cap_sys_admin,cap_sys_boot,cap_sys_module'.split(',')

"""
parser = OptionParser()
parser.add_option("-n", "--net",
                  action="store_true", dest="netns", default=False,
                  help="Enter network namespace")
parser.add_option("-m", "--mnt",
                  action="store_true", dest="mntns", default=False,
                  help="Enter mount namespace")
parser.add_option("-p", "--pid",
                  action="store_true", dest="pidns", default=False,
                  help="Enter pid namespace")

(options, args) = parser.parse_args()
"""
args = sys.argv[1:]

try:
	slice_name = args[0]
except IndexError:
	print "You must specify a vm name"
	exit(1)

try:
	cmd = 'grep %s /proc/*/cgroup | grep freezer'%slice_name
	output = os.popen(cmd).readlines()
except:
	print "Error finding slice %s"%slice_name
	exit(1)

slice_spec = None
for e in output:
	try:
		l = e.rstrip()
		path = l.split(':')[0]	
		comp = l.rsplit(':')[-1]
		slice_name_check = comp.rsplit('/')[-1]

		if (slice_name_check == slice_name):
			slice_path = path
			pid = slice_path.split('/')[2]
			cmdline = open('/proc/%s/cmdline'%pid).read().rstrip('\n\x00')
			if (cmdline == '/sbin/init'):
				slice_spec = slice_path
				break
	except:
		break

if (not slice_spec or not pid):
    print "Not started: %s"%slice_name
    exit(1)

# Enter cgroups
try:
    for subsystem in ['cpuset','memory','blkio']:
        open('/sys/fs/cgroup/%s/libvirt/lxc/%s/tasks'%(subsystem,slice_name),'w').write(str(os.getpid()))

except:
    print "Error assigning resources: %s"%slice_name
    exit(1)

try:
    open('/sys/fs/cgroup/cpuacct/system/libvirtd.service/libvirt/lxc/%s/tasks'%slice_name,'w').write(str(os.getpid()))
except:
    print "Error assigning cpuacct: %s" % slice_name
    exit(1)

# If the slice is frozen, then we'll get an EBUSY when trying to write to the task
# list for the freezer cgroup. Since the user couldn't do anything anyway, it's best
# in this case to error out the shell. (an alternative would be to un-freeze it,
# add the task, and re-freeze it)
try:
    f=open('/sys/fs/cgroup/freezer/libvirt/lxc/%s/tasks'%(slice_name),'w')
    f.write(str(os.getpid()))
    # note: we need to call f.close() explicitly, or we'll get an exception in
    # the object destructor, which will not be caught
    f.close()
except:
    print "Error adding task to freezer cgroup. Slice is probably frozen: %s" % slice_name
    exit(1)

r1 = setns.chcontext('/proc/%s/ns/uts'%pid)
r2 = setns.chcontext('/proc/%s/ns/ipc'%pid)
r3 = setns.chcontext('/proc/%s/ns/net'%pid)

open('/proc/lxcsu','w').write(pid)
open('/proc/pidsu','w').write(pid)

pid = os.fork()

cap_args = map(lambda c:'--drop='+c, drop_capabilities)
    
if (pid == 0):
    os.environ['SHELL'] = '/bin/sh'
    os.execv('/usr/sbin/capsh',cap_args+['--','--login']+args[1:])
else:
    os.waitpid(pid,0)