#!/usr/bin/python3

# pylint: disable=c0111, w0703

import sys
import os
import re

from argparse import ArgumentParser

import setns

# can set to True here, but also use the -d option
DEBUG = False


def getarch(file):
    output = os.popen('readelf -h %s 2>&1' % file).readlines()
    classlines = [x for x in output if 'Class' in x.split(':')[0]]
    line = classlines[0]
    token = line.split(':')[1]
    if 'ELF64' in token:
        return 'x86_64'
    if 'ELF32' in token:
        return 'i686'
    raise Exception('Could not determine architecture')


def get_cgroup_subdirs_for_pid(pid):
    cgroup_info_file = '/proc/%s/cgroup' % pid
    cgroup_lines = open(cgroup_info_file).read().splitlines()

    subdirs = {}
    for line in cgroup_lines:
        try:
            _, cgroup_name, subdir = line.split(':')
            subdirs[cgroup_name] = subdir
        except Exception as exc:
            print("Error reading cgroup info: %s" % str(exc))

    return subdirs


def umount(fs_dir, opts=''):
    output = os.popen('/bin/umount %s %s 2>&1' % (opts, fs_dir)).read()
    return 'device is busy' not in output


def kvmsu(slice_name, args):
    mac_addresses = []

    # Find MAC addresses of virt interfaces
    process = os.popen("virsh domiflist %s" % slice_name)
    for line in process:
        match = re.search(r'([0-9A-F]{2}[:-]){5}([0-9A-F]{2})', line, re.I)
        if match:
            mac_addresses.append(match.group())

    # Find IP address of a reachable virt interface
    # Here we're taking the one attached to br-nat, but this is specific to OpenCloud
    ip_addr = None
    try:
        with open('/var/lib/dnsmasq/br-nat.hosts', 'r') as feed:
            for line in feed:
                for mac in mac_addresses:
                    match = re.search("^%s,[0-9.]+$" % mac, line, re.I)
                    if match:
                        ip_addr = match.group().split(',')[1]
                        break
    except Exception:
        pass

    if ip_addr:
        # Need to login to a Ubuntu Cloud image as 'ubuntu' user
        # Not sure how to make this more general
        os.execv('/usr/bin/ssh',
                 ['/usr/bin/ssh', '-o', 'StrictHostKeyChecking=no',
                  'ubuntu@%s' % ip_addr]
                 + args.command_to_run)
    else:
        # What should happen here?
        print("Cannot map instance to IP address")
        exit(1)


def lxcsu(slice_name, args):
        # plain lxcsu
    if not args.internal:
                # no command given: enter interactive shell
        if not args.command_to_run:
            args.command_to_run = ['/bin/sh']
        args.command_to_run = ['-c'] + [" ".join(args.command_to_run)]

    # support for either setting debug at the top of this file, or on the command-line
    if args.debug:
        global DEBUG
        DEBUG = True

    try:
        cmd = '/usr/bin/virsh --connect lxc:/// domid %s' % slice_name
        # convert to int as a minimal raincheck
        driver_pid = int(os.popen(cmd).read().strip())
        # locate the pid for the - expected - single child, that would be the init for that VM
        #init_pid = int(open("/proc/%s/task/%s/children"%(driver_pid,driver_pid)).read().strip())
        init_pid = int(os.popen('pgrep -P %s' %
                                driver_pid).readlines()[0].strip())
        # Thierry: I am changing the code below to use child_pid instead of driver_pid
        # for the namespace handling features, that I was able to check
        # I've left the other ones as they were, i.e. using driver_pid, but I suspect
        # they chould be changed as well

    except Exception:
        print("Domain %s not found" % slice_name)
        exit(1)

    if not driver_pid or not init_pid:
        print("Domain %s not started" % slice_name)
        exit(1)

    if DEBUG:
        print("Found driver_pid", driver_pid, 'and init_pid=', init_pid)
    arch = getarch('/proc/%s/exe' % driver_pid)

    # Set sysctls specific to slice
    sysctls = []
    sysctl_dir = '/etc/planetlab/vsys-attributes/%s' % slice_name
    if os.access(sysctl_dir, 0):
        entries = os.listdir(sysctl_dir)
        for entry in entries:
            prefix = 'vsys_sysctl.'
            if entry.startswith(prefix):
                sysctl_file = '/'.join([sysctl_dir, entry])
                sysctl_name = entry[len(prefix):]
                with open(sysctl_file) as feed:
                    sysctl_val = feed.read()
                sysctls.append((sysctl_file, sysctl_name, sysctl_val))

    subdirs = get_cgroup_subdirs_for_pid(driver_pid)
    sysfs_root = '/sys/fs/cgroup'

    # 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)
    # Enter cgroups
    current_cgroup = ''
    for subsystem in ['cpuset', 'memory', 'blkio', 'cpuacct', 'cpuacct,cpu', 'freezer']:
        try:
            current_cgroup = subsystem

            # There seems to be a bug in the cgroup schema: cpuacct,cpu can become cpu,cpuacct
            # We need to handle both
            try:
                subsystem_comps = subsystem.split(',')
                subsystem_comps.reverse()
                subsystem_alt = ','.join(subsystem_comps)
                tasks_path_alt = [sysfs_root, subsystem_alt,
                                  subdirs[subsystem], 'tasks']
            except Exception:
                pass

            tasks_path = [sysfs_root, subsystem, subdirs[subsystem], 'tasks']
            tasks_path_str = '/'.join(tasks_path)

            try:
                feed = open(tasks_path_str, 'w')
            except Exception:
                tasks_path_alt_str = '/'.join(tasks_path_alt)
                feed = open(tasks_path_alt_str, 'w')

            feed.write(str(os.getpid()))
            if subsystem == 'freezer':
                feed.close()

        except Exception as exc:
            if subsystem not in subdirs:
                pass
            else:
                if DEBUG:
                    print(exc)
                print("Error assigning cgroup %s (pid=%s) for slice %s" %
                      (current_cgroup, driver_pid, slice_name))
                exit(1)

    def chcontext(path):
        retcod = setns.chcontext(path)
        if retcod != 0:
            print('WARNING - setns(%s)=>%s (ignored)' % (path, retcod))
        return retcod

    # Use init_pid and not driver_pid to locate reference namespaces
    ref_ns = "/proc/%s/ns/" % init_pid

    if True:
        chcontext(ref_ns+'uts')
    if True:
        chcontext(ref_ns+'ipc')

    if not args.no_pidns:
        chcontext(ref_ns+'pid')
    if not args.no_netns:
        chcontext(ref_ns+'net')
    if not args.no_mntns:
        chcontext(ref_ns+'mnt')

    if not os.access('/proc/self', 0):
        setns.proc_mount()

    for (sysctl_file, sysctl_name, sysctl_val) in sysctls:
        for binary in ["/sbin/sysctl", "/usr/sbin/sysctl", "/bin/sysctl", "/usr/bin/sysctl"]:
            if os.path.exists(binary):
                os.system('%s -w %s=%s	>/dev/null 2>&1' %
                          (binary, sysctl_name, sysctl_val))
                break
            else:
                print("Error: image does not have a sysctl binary")

    # cgroups is not yet LXC-safe, so we need to use the coarse grained access control
    # strategy of unmounting the filesystem

    for subsystem in ['cpuset', 'cpu,cpuacct', 'memory', 'devices', 'freezer',
                      'net_cls', 'blkio', 'perf_event', 'systemd']:
        fs_path = '/sys/fs/cgroup/%s' % subsystem
        if not umount(fs_path, '-l'):
            print('WARNING - umount failed (ignored) with path=', fs_path)
            # Leaving these comments for historical reference
            # print "Error disabling cgroup access"
            # exit(1) - Don't need this because failure here implies failure
            # in the call to umount /sys/fs/cgroup

    if not umount('/sys/fs/cgroup'):
        print("Error disabling cgroup access")
        exit(1)

    fork_pid = os.fork()

    def getuid(slicename):
        import pwd
        try:
            return pwd.getpwnam(slicename).pw_uid
        except Exception:
            return

    if fork_pid == 0:
        if not args.root:
            setns.drop_caps()
            if args.nosliceuid:
                # we still want to drop capabilities, but don't want to switch UIDs
                exec_args = [arch, '/bin/sh', '--login', ] + args.command_to_run
            else:
                # let's keep this check even though we don't use the uid
                # as a way of checking the existence of the slice account
                uid = getuid(slice_name)
                if not uid:
                    print("lxcsu could not spot %s in /etc/passwd - exiting" %
                          slice_name)
                    exit(1)
                exec_args = [arch, '/usr/bin/sudo', '-u', slice_name,
                             '/bin/sh', '--login', ] + args.command_to_run
# once we can drop f12, it would be nicer to instead go for
# exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--user=%s'%slice_name,'--login',]+args.command_to_run
        else:
            exec_args = [arch, '/bin/sh', '--login'] + args.command_to_run

        os.environ['SHELL'] = '/bin/sh'
        if os.path.exists('/etc/planetlab/lib/bind_public.so'):
            os.environ['LD_PRELOAD'] = '/etc/planetlab/lib/bind_public.so'
        if not args.noslicehome:
            os.environ['HOME'] = '/home/%s' % slice_name
            os.chdir("/home/%s" % (slice_name))
        if DEBUG:
            print('lxcsu:execv:', '/usr/bin/setarch', exec_args)
        os.execv('/usr/bin/setarch', exec_args)
    else:
        setns.proc_umount()
        _, status = os.waitpid(fork_pid, 0)
        exit(os.WEXITSTATUS(status))


def main():
    parser = ArgumentParser()
    parser.add_argument(
        "-n", "--nonet",
        action="store_true", dest="no_netns", default=False,
        help="Don't enter network namespace")
    parser.add_argument(
        "-m", "--nomnt",
        action="store_true", dest="no_mntns", default=False,
        help="Don't enter mount namespace")
    parser.add_argument(
        "-p", "--nopid",
        action="store_true", dest="no_pidns", default=False,
        help="Don't enter pid namespace")
    parser.add_argument(
        "-r", "--root",
        action="store_true", dest="root", default=False,
        help="Enter as root: be careful")
    parser.add_argument(
        "-i", "--internal",
        action="store_true", dest="internal", default=False,
        help="does *not* prepend '-- -c' to arguments - or invoke lxcsu-internal")
    parser.add_argument(
        "-d", "--debug",
        action='store_true', dest='debug', default=False,
        help="debug option")
    parser.add_argument(
        "-s", "--nosliceuid",
        action='store_true', dest="nosliceuid", default=False,
        help="do not change to slice uid inside of slice")
    parser.add_argument(
        "-o", "--noslicehome",
        action='store_true', dest="noslicehome", default=False,
        help="do not change to slice home directory inside of slice")

    if os.path.exists("/etc/lxcsu_default"):
        with open("/etc/lxcsu_default", "r") as feed:
            defaults = parser.parse_args(feed.read().split())
        parser.set_defaults(**defaults.__dict__)

    parser.add_argument("slice_name")
    parser.add_argument("command_to_run", nargs="*")

    args = parser.parse_args()
    slice_name = args.slice_name

    # unless we run the symlink 'lxcsu-internal', or we specify the -i option, prepend '--' '-c'
    if sys.argv[0].find('internal') >= 0:
        args.internal = True

    if args.command_to_run and (args.command_to_run[0] == "/sbin/service"):
        # A quick hack to support nodemanager interfaces.py when restarting
        # networking in a slice.
        args.nosliceuid = True

    try:
        cmd = '/usr/bin/virsh dominfo %s' % slice_name
        info = os.popen(cmd).read()
        useless_hash = {}

        ostype = None
        for line in info.split('\n'):
            pair = line.split(':')
            useless_hash[pair[0].strip()] = pair[1].strip()
            if pair[0].strip() == 'OS Type':
                ostype = pair[1].strip()
                break
    except Exception:
        print("Domain %s not found" % slice_name)

    is_kvm = ostype == 'hvm'

    if is_kvm:
        kvmsu(slice_name, args)
    else:
        lxcsu(slice_name, args)


if __name__ == '__main__':
    main()