## This file is part of Scapy
## See http://www.secdev.org/projects/scapy for more informations
## Copyright (C) Philippe Biondi <phil@secdev.org>
## This program is published under a GPLv2 license

"""
NTP (Network Time Protocol).
"""

import time
from scapy.packet import *
from scapy.fields import *
from scapy.layers.inet import UDP


# seconds between 01-01-1900 and 01-01-1970
_NTP_BASETIME = 2208988800

class TimeStampField(FixedPointField):
    def __init__(self, name, default):
        FixedPointField.__init__(self, name, default, 64, 32)

    def i2repr(self, pkt, val):
        if val is None:
            return "--"
        val = self.i2h(pkt,val)
        if val < _NTP_BASETIME:
            return val
        return time.strftime("%a, %d %b %Y %H:%M:%S +0000", time.gmtime(val-_NTP_BASETIME))

    def any2i(self, pkt, val):
        if type(val) is str:
            return int(time.mktime(time.strptime(val))) + _NTP_BASETIME + 3600 # XXX
        return FixedPointField.any2i(self,pkt,val)
    
    def i2m(self, pkt, val):
        if val is None:
            val = FixedPointField.any2i(self, pkt, time.time()+_NTP_BASETIME)
        return FixedPointField.i2m(self, pkt, val)
        


class NTP(Packet):
    # RFC 1769
    name = "NTP"
    fields_desc = [ 
         BitEnumField('leap', 0, 2,
                      { 0: 'nowarning',
                        1: 'longminute',
                        2: 'shortminute',
                        3: 'notsync'}),
         BitField('version', 3, 3),
         BitEnumField('mode', 3, 3,
                      { 0: 'reserved',
                        1: 'sym_active',
                        2: 'sym_passive',
                        3: 'client',
                        4: 'server',
                        5: 'broadcast',
                        6: 'control',
                        7: 'private'}),
         BitField('stratum', 2, 8),
         BitField('poll', 0xa, 8),          ### XXX : it's a signed int
         BitField('precision', 0, 8),       ### XXX : it's a signed int
         FixedPointField('delay', 0, size=32, frac_bits=16),
         FixedPointField('dispersion', 0, size=32, frac_bits=16),
         IPField('id', "127.0.0.1"),
         TimeStampField('ref', 0),
         TimeStampField('orig', None),  # None means current time
         TimeStampField('recv', 0),
         TimeStampField('sent', None) 
         ]
    def mysummary(self):
        return self.sprintf("NTP v%ir,NTP.version%, %NTP.mode%")


bind_layers( UDP,           NTP,           dport=123, sport=123)