211 lines
9.8 KiB
Python
211 lines
9.8 KiB
Python
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#!/usr/bin/env python3
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# See RFC 2131, Figure 1 and Table 1 (section 2)
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# Much thanks to https://github.com/igordcard/dhcplease for digging into dhcpcd
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# source for the actual file structure (and providing inspiration).
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import argparse
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import collections
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import os
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import re
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import struct
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from io import BytesIO
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## DEFINE SOME PRETTY STUFF ##
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class color(object):
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PURPLE = '\033[95m'
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CYAN = '\033[96m'
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DARKCYAN = '\033[36m'
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BLUE = '\033[94m'
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GREEN = '\033[92m'
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YELLOW = '\033[93m'
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RED = '\033[91m'
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BOLD = '\033[1m'
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UNDERLINE = '\033[4m'
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END = '\033[0m'
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class packetParser(object):
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def __init__(self, data):
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## Set the segment labels and struct formats
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self.fmt = collections.OrderedDict()
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# In the below, 'cnt' is how large (in octets) the field is.
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# 'fmt' is a struct format string (https://docs.python.org/3/library/struct.html#format-characters)
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# "op" through "hops" (incl.) may actually be '8B' instead of '8c'.
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self.fmt['op'] = {'cnt': 8, 'fmt': '8c'} # this will always be \x02
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self.fmt['htype'] = {'cnt': 8, 'fmt': '8c'} # this will always be \x01
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self.fmt['hlen'] = {'cnt': 8, 'fmt': '8c'}
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self.fmt['hops'] = {'cnt': 8, 'fmt': '8c'}
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self.fmt['xid'] = {'cnt': 32, 'fmt': '8I'}
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self.fmt['secs'] = {'cnt': 16, 'fmt': '8H'}
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self.fmt['flags'] = {'cnt': 16, 'fmt': '8H'}
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# "ciaddr" through "giaddr" (incl.) may actually be '4c' instead of '4B'.
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self.fmt['ciaddr'] = {'cnt': 4, 'fmt': '4B'}
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self.fmt['yiaddr'] = {'cnt': 4, 'fmt': '4B'}
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self.fmt['siaddr'] = {'cnt': 4, 'fmt': '4B'}
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self.fmt['giaddr'] = {'cnt': 4, 'fmt': '4B'}
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# "chaddr" through "file" (incl.) may actually be <#>c instead of <#>B.
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self.fmt['chaddr'] = {'cnt': 16, 'fmt': '16B'} # first 6 bytes used for MAC addr of client
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self.fmt['sname'] = {'cnt': 64, 'fmt': '64B'} # server host name (via BOOTP)
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self.fmt['file'] = {'cnt': 128, 'fmt': '128B'} # the boot filename (for BOOTP)
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# OPTIONS - RFC 2132
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# Starting at octet 320 (so, f.seek(319, 0)) to the end of the message are
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# DHCP options. It's a variable-length field so it makes things tricky
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# for us. But it's at *least* 312 octets long per the RFC?
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# It probably starts with a magic.
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#self.dhcp_opts = {'idx': 324, 'cnt': 4, 'fmt': '4c'}
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#self.dhcp_opts = {'idx': 324, 'cnt': 4, 'fmt': None}
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self.opts = {'magic': b'\x63\x82\x53\x63',
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'struct': {'idx': 324, 'cnt': 4, 'fmt': '4B'},
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'size': 0,
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'bytes': b'\00'}
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## Convert the data into a bytes object because struct.unpack() wants a stream
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self.buf = BytesIO(data)
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def getStd(self):
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self.reconstructed_segments = collections.OrderedDict()
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_idx = 0 # add to this with the 'cnt' value for each iteration.
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for k in self.fmt.keys():
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print('Segment: ' + k) # TODO: remove, this stuff goes in the printer
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pkt = struct.Struct(self.fmt[k]['fmt'])
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self.buf.seek(_idx, 0)
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try:
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self.reconstructed_segments[k] = pkt.unpack(self.buf.read(self.fmt[k]['cnt']))
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except struct.error as e:
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# Some DHCP implementations are... broken.
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# I've noticed it mostly in Verizon Fi-OS gateways/WAPs/routers.
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print('Warning({0}): {1}'.format(k, e))
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self.buf.seek(_idx, 0)
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_truesize = len(self.buf.read(self.fmt[k]['cnt']))
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print('Length of bytes read: {0}'.format(_truesize))
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# But sometimes it's... kind of fixable?
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if k == 'file' and _truesize < self.fmt[k]['cnt']:
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self.buf.seek(_idx, 0)
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self.fmt[k] = {'cnt': _truesize, 'fmt': '{0}B'.format(_truesize)}
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pkt = struct.Struct(self.fmt[k]['fmt'])
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print('Struct format size automatically adjusted.')
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try:
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self.reconstructed_segments[k] = pkt.unpack(self.buf.read(self.fmt[k]['cnt']))
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except struct.error as e2:
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# yolo.
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print('We still couldn\'t populate {0}; filling with a nullbyte.'.format(k))
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print('Error (try #2): {0}'.format(e2))
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print('We read {0} bytes.'.format(_truesize))
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print('fmt: {0}'.format(self.fmt[k]['fmt']))
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self.reconstructed_segments[k] = b'\00'
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_idx += self.fmt[k]['cnt']
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self.buf.seek(_idx, 0)
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# Finally, check for opts. If they exist, populate.
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_optbytes = len(self.buf.read())
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if _optbytes >= 1:
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self.opts['size'] = _optbytes
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self.buf.seek(_idx, 0)
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self.opts['bytes'] = self.buf.read() # read to the end
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return()
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def getOpts(self):
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pass
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def close(self):
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self.buf.close()
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def parseArgs():
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args = argparse.ArgumentParser()
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_deflease = '/var/lib/dhcpcd/'
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args.add_argument('-l', '--lease',
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metavar = '/path/to/lease/dir/or_file.lease',
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default = _deflease,
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dest = 'leasepath',
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help = ('The path to the directory of lease files or specific lease file. ' +
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'If a directory is provided, all lease files found within will be ' +
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'parsed. Default: {0}{1}{2}').format(color.BOLD,
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_deflease,
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color.END))
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args.add_argument('-n', '--no-color',
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action = 'store_false',
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dest = 'color',
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help = ('If specified, suppress color formatting in output.'))
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args.add_argument('-d', '--dump',
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metavar = '/path/to/dumpdir',
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default = False,
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dest = 'dump',
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help = ('If provided, dump the parsed leases to this directory (in ' +
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'addition to printing). It will dump with the same filename ' +
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'and overwrite any existing file with the same filename, so ' +
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'do NOT use the same directory as your dhcpcd lease files! ' +
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'({0}-l/--lease{1}). The directory will be created if it does ' +
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'not exist').format(color.BOLD,
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color.END))
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args.add_argument('-p', '--pretty',
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action = 'store_true',
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dest = 'prettyprint',
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help = ('If specified, include color formatting {0}in the dump ' +
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'file(s){1}').format(color.BOLD, color.END))
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return(args)
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def getLeaseData(fpath):
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if not os.path.isfile(fpath):
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raise FileNotFoundError('{0} does not exist'.format(fpath))
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with open(fpath, 'rb') as f:
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_data = f.read()
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return(_data)
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def iterLease(args):
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# If the lease path is a file, just operate on that.
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# If it's a directory, iterate (recursively) through it.
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leases = {}
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if not os.path.lexists(args['leasepath']):
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raise FileNotFoundError('{0} does not exist'.format(args['leasepath']))
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if os.path.isfile(args['leasepath']):
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_pp = packetParser(getLeaseData(args['leasepath']))
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# TODO: convert the hex vals to their actual vals... maybe?
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_keyname = re.sub('^(dhcpcd-)?(.*)\.lease$',
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'\g<2>',
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os.path.basename(args['leasepath']))
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leases[_keyname] = leaseParse(_pp, args)
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else:
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# walk() instead of listdir() because whotf knows when some distro like
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# *coughcoughUbuntucoughcough* will do some breaking change like creating
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# subdirs based on iface name or something.
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for _, _, files in os.walk(args['leasepath']):
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if not files:
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continue
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files = [i for i in files if i.endswith('.lease')] # only get .lease files
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for i in files:
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_args = args.copy()
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_fpath = os.path.join(args['leasepath'], i)
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_keyname = re.sub('^(dhcpcd-)?(.*)\.lease$', '\g<2>', os.path.basename(_fpath))
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_dupeid = 0
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# JUST in case there are multiple levels of dirs in the future
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# that have files of the sama name
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while _keyname in leases.keys():
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# TODO: convert the hex vals to their actual vals... maybe?
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_keyname = re.sub('^$',
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'\g<1>.{0}'.format(_dupeid),
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_keyname)
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_dupeid += 1
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_pp = packetParser(getLeaseData(_fpath))
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leases[_keyname] = leaseParse(_pp, _args, fname = _fpath)
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return(leases)
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def leaseParse(pp, args, fname = False):
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# Essentially just a wrapper function.
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# Debugging output...
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if fname:
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print(fname)
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pp.getStd()
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pp.getOpts()
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if args['dump']:
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pass # TODO: write to files, creating dump dir if needed, etc.
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pp.close()
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# do pretty-printing (color-coded segments, etc.) here
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return(pp.reconstructed_segments)
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if __name__ == '__main__':
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args = vars(parseArgs().parse_args())
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args['leasepath'] = os.path.abspath(os.path.expanduser(args['leasepath']))
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if not os.path.lexists(args['leasepath']):
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exit('{0} does not exist!'.format(args['leasepath']))
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leases = iterLease(args)
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# just print for now until we write the parser/prettyprinter
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print(list(leases.keys()))
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