323 lines
11 KiB
Python
323 lines
11 KiB
Python
# Copyright (C) 2015 Nippon Telegraph and Telephone Corporation.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Parsing libpcap and reading/writing PCAP file.
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Reference source: http://wiki.wireshark.org/Development/LibpcapFileFormat
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Libpcap File Format
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+---------------------+
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| Global Header |
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+---------------------+
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| Packet Header |
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+---------------------+
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| Packet Data |
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+---------------------+
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| Packet Header |
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+---------------------+
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| Packet Data |
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+---------------------+
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| ... |
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+---------------------+
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"""
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import struct
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import sys
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import time
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class PcapFileHdr(object):
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"""
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Global Header
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typedef struct pcap_hdr_s {
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guint32 magic_number; /* magic number */
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guint16 version_major; /* major version number */
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guint16 version_minor; /* minor version number */
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gint32 thiszone; /* GMT to local correction */
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guint32 sigfigs; /* accuracy of timestamps */
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guint32 snaplen; /* max length of captured packets,
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in octets */
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guint32 network; /* data link type */
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} pcap_hdr_t;
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Magic Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Version Major | Version Minor |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Thiszone |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Sigfigs |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Snaplen |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Network |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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File Format
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"""
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_FILE_HDR_FMT = '4sHHIIII'
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_FILE_HDR_FMT_BIG_ENDIAN = '>' + _FILE_HDR_FMT
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_FILE_HDR_FMT_LITTLE_ENDIAN = '<' + _FILE_HDR_FMT
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FILE_HDR_SIZE = struct.calcsize(_FILE_HDR_FMT)
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# Magic Number field is used to detect the file format itself and
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# the byte ordering.
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MAGIC_NUMBER_IDENTICAL = b'\xa1\xb2\xc3\xd4' # Big Endian
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MAGIC_NUMBER_SWAPPED = b'\xd4\xc3\xb2\xa1' # Little Endian
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def __init__(self, magic=MAGIC_NUMBER_SWAPPED, version_major=2,
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version_minor=4, thiszone=0, sigfigs=0, snaplen=0,
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network=0):
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self.magic = magic
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self.version_major = version_major
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self.version_minor = version_minor
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self.thiszone = thiszone
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self.sigfigs = sigfigs
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self.snaplen = snaplen
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self.network = network
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@classmethod
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def parser(cls, buf):
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magic_buf = buf[:4]
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if magic_buf == cls.MAGIC_NUMBER_IDENTICAL:
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# Big Endian
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fmt = cls._FILE_HDR_FMT_BIG_ENDIAN
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byteorder = 'big'
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elif magic_buf == cls.MAGIC_NUMBER_SWAPPED:
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# Little Endian
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fmt = cls._FILE_HDR_FMT_LITTLE_ENDIAN
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byteorder = 'little'
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else:
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raise struct.error('Invalid byte ordered pcap file.')
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return cls(*struct.unpack_from(fmt, buf)), byteorder
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def serialize(self):
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if sys.byteorder == 'big':
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# Big Endian
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fmt = self._FILE_HDR_FMT_BIG_ENDIAN
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self.magic = self.MAGIC_NUMBER_IDENTICAL
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else:
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# Little Endian
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fmt = self._FILE_HDR_FMT_LITTLE_ENDIAN
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self.magic = self.MAGIC_NUMBER_SWAPPED
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return struct.pack(fmt, self.magic, self.version_major,
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self.version_minor, self.thiszone,
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self.sigfigs, self.snaplen, self.network)
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class PcapPktHdr(object):
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"""
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Record (Packet) Header
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typedef struct pcaprec_hdr_s {
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guint32 ts_sec; /* timestamp seconds */
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guint32 ts_usec; /* timestamp microseconds */
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guint32 incl_len; /* number of octets of packet
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saved in file */
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guint32 orig_len; /* actual length of packet */
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} pcaprec_hdr_t;
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Timestamp Seconds |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Timestamp Microseconds |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Number of octets of saved in file |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Actual length of packet |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Record (Packet) Header Format
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"""
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_PKT_HDR_FMT = 'IIII'
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_PKT_HDR_FMT_BIG_ENDIAN = '>' + _PKT_HDR_FMT
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_PKT_HDR_FMT_LITTLE_ENDIAN = '<' + _PKT_HDR_FMT
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PKT_HDR_SIZE = struct.calcsize(_PKT_HDR_FMT)
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def __init__(self, ts_sec=0, ts_usec=0, incl_len=0, orig_len=0):
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self.ts_sec = ts_sec
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self.ts_usec = ts_usec
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self.incl_len = incl_len
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self.orig_len = orig_len
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@classmethod
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def parser(cls, buf, byteorder='little'):
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if not buf:
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raise IndexError('No data')
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if byteorder == 'big':
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# Big Endian
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fmt = cls._PKT_HDR_FMT_BIG_ENDIAN
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else:
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# Little Endian
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fmt = cls._PKT_HDR_FMT_LITTLE_ENDIAN
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(ts_sec, ts_usec, incl_len, orig_len) = struct.unpack_from(fmt, buf)
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hdr = cls(ts_sec, ts_usec, incl_len, orig_len)
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return hdr, buf[cls.PKT_HDR_SIZE:cls.PKT_HDR_SIZE + incl_len]
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def serialize(self):
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if sys.byteorder == 'big':
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# Big Endian
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fmt = self._PKT_HDR_FMT_BIG_ENDIAN
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else:
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# Little Endian
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fmt = self._PKT_HDR_FMT_LITTLE_ENDIAN
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return struct.pack(fmt, self.ts_sec, self.ts_usec,
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self.incl_len, self.orig_len)
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class Reader(object):
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"""
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PCAP file reader
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================ ===================================
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Argument Description
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================ ===================================
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file_obj File object which reading PCAP file
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in binary mode
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================ ===================================
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Example of usage::
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from os_ken.lib import pcaplib
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from os_ken.lib.packet import packet
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frame_count = 0
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# iterate pcaplib.Reader that yields (timestamp, packet_data)
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# in the PCAP file
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for ts, buf in pcaplib.Reader(open('test.pcap', 'rb')):
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frame_count += 1
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pkt = packet.Packet(buf)
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print("%d, %f, %s" % (frame_count, ts, pkt))
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"""
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def __init__(self, file_obj):
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self._fp = file_obj
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buf = self._fp.read(PcapFileHdr.FILE_HDR_SIZE)
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# Read only pcap file header
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self.pcap_header, self._file_byteorder = PcapFileHdr.parser(buf)
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# Read pcap data with out header
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self._pcap_body = self._fp.read()
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self._fp.close()
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self._next_pos = 0
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def __iter__(self):
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return self
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def next(self):
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try:
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pkt_hdr, pkt_data = PcapPktHdr.parser(
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self._pcap_body[self._next_pos:], self._file_byteorder)
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self._next_pos += pkt_hdr.incl_len + PcapPktHdr.PKT_HDR_SIZE
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except IndexError:
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raise StopIteration()
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return pkt_hdr.ts_sec + (pkt_hdr.ts_usec / 1e6), pkt_data
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# for Python 3 compatible
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__next__ = next
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class Writer(object):
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"""
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PCAP file writer
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========== ==================================================
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Argument Description
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========== ==================================================
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file_obj File object which writing PCAP file in binary mode
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snaplen Max length of captured packets (in octets)
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network Data link type. (e.g. 1 for Ethernet,
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see `tcpdump.org`_ for details)
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========== ==================================================
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.. _tcpdump.org: http://www.tcpdump.org/linktypes.html
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Example of usage::
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...
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from os_ken.lib import pcaplib
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class SimpleSwitch13(app_manager.RyuApp):
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OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
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def __init__(self, *args, **kwargs):
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super(SimpleSwitch13, self).__init__(*args, **kwargs)
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self.mac_to_port = {}
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# Create pcaplib.Writer instance with a file object
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# for the PCAP file
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self.pcap_writer = pcaplib.Writer(open('mypcap.pcap', 'wb'))
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...
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@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
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def _packet_in_handler(self, ev):
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# Dump the packet data into PCAP file
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self.pcap_writer.write_pkt(ev.msg.data)
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...
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"""
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def __init__(self, file_obj, snaplen=65535, network=1):
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self._f = file_obj
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self.snaplen = snaplen
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self.network = network
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self._write_pcap_file_hdr()
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def _write_pcap_file_hdr(self):
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pcap_file_hdr = PcapFileHdr(snaplen=self.snaplen,
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network=self.network)
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self._f.write(pcap_file_hdr.serialize())
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def _write_pkt_hdr(self, ts, buf_len):
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sec = int(ts)
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usec = int(round(ts % 1, 6) * 1e6) if sec != 0 else 0
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pc_pkt_hdr = PcapPktHdr(ts_sec=sec, ts_usec=usec,
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incl_len=buf_len, orig_len=buf_len)
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self._f.write(pc_pkt_hdr.serialize())
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def write_pkt(self, buf, ts=None):
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ts = time.time() if ts is None else ts
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# Check the max length of captured packets
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buf_len = len(buf)
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if buf_len > self.snaplen:
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buf_len = self.snaplen
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buf = buf[:self.snaplen]
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self._write_pkt_hdr(ts, buf_len)
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self._f.write(buf)
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def __del__(self):
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self._f.close()
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