1 # Copyright (c) 2020 Cisco and/or its affiliates.
3 # SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
5 # Licensed under the Apache License 2.0 or
6 # GNU General Public License v2.0 or later; you may not use this file
7 # except in compliance with one of these Licenses. You
8 # may obtain a copy of the Licenses at:
10 # http://www.apache.org/licenses/LICENSE-2.0
11 # https://www.gnu.org/licenses/old-licenses/gpl-2.0-standalone.html
13 # Note: If this file is linked with Scapy, which is GPLv2+, your use of it
14 # must be under GPLv2+. If at any point in the future it is no longer linked
15 # with Scapy (or other GPLv2+ licensed software), you are free to choose Apache 2.
17 # Unless required by applicable law or agreed to in writing, software
18 # distributed under the License is distributed on an "AS IS" BASIS,
19 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
20 # See the License for the specific language governing permissions and
21 # limitations under the License.
23 """PacketVerifier module.
27 | >>> from scapy.all import *
28 | >>> from PacketVerifier import *
29 | >>> rxq = RxQueue('eth1')
30 | >>> txq = TxQueue('eth1')
31 | >>> src_mac = "AA:BB:CC:DD:EE:FF"
32 | >>> dst_mac = "52:54:00:ca:5d:0b"
33 | >>> src_ip = "11.11.11.10"
34 | >>> dst_ip = "11.11.11.11"
35 | >>> sent_packets = []
36 | >>> pkt_send = Ether(src=src_mac, dst=dst_mac) /
37 | ... IP(src=src_ip, dst=dst_ip) /
39 | >>> sent_packets.append(pkt_send)
40 | >>> txq.send(pkt_send)
41 | >>> pkt_send = Ether(src=src_mac, dst=dst_mac) /
42 | ... ARP(hwsrc=src_mac, psrc=src_ip, hwdst=dst_mac, pdst=dst_ip, op=2)
43 | >>> sent_packets.append(pkt_send)
44 | >>> txq.send(pkt_send)
45 | >>> rxq.recv(100, sent_packets).show()
47 | dst = aa:bb:cc:dd:ee:ff
48 | src = 52:54:00:ca:5d:0b
71 | load = 'RT\x00\xca]\x0b\xaa\xbb\xcc\xdd\xee\xff\x08\x06\x00\x01\x08\x00'
79 from scapy.all import ETH_P_IP, ETH_P_IPV6, ETH_P_ALL, ETH_P_ARP
80 from scapy.config import conf
81 from scapy.layers.inet6 import IPv6
82 from scapy.layers.l2 import Ether, ARP
83 from scapy.packet import Raw, Padding
85 # Enable libpcap's L2listen
89 u"RxQueue", u"TxQueue", u"Interface", u"create_gratuitous_arp_request",
90 u"auto_pad", u"checksum_equal"
93 # TODO: http://stackoverflow.com/questions/320232/
94 # ensuring-subprocesses-are-dead-on-exiting-python-program
98 """Base class for TX and RX queue objects for packet verifier."""
99 def __init__(self, interface_name):
101 f"sudo echo 1 > /proc/sys/net/ipv6/conf/{interface_name}/"
104 os.system(f"sudo ip link set {interface_name} up promisc on")
105 self._ifname = interface_name
108 def extract_one_packet(buf):
109 """Extract one packet from the incoming buf buffer.
111 Takes string as input and looks for first whole packet in it.
112 If it finds one, it returns substring from the buf parameter.
114 :param buf: String representation of incoming packet buffer.
116 :returns: String representation of first packet in buf.
125 ether_type = Ether(buf[0:14]).type
126 except AttributeError:
127 raise RuntimeError(f"No EtherType in packet {buf!r}")
129 if ether_type == ETH_P_IP:
130 # 14 is Ethernet fame header size.
131 # 4 bytes is just enough to look for length in ip header.
132 # ip total length contains just the IP packet length so add the Ether
134 pkt_len = Ether(buf[0:14+4]).len + 14
137 elif ether_type == ETH_P_IPV6:
138 if not Ether(buf[0:14+6]).haslayer(IPv6):
139 raise RuntimeError(f"Invalid IPv6 packet {buf!r}")
140 # ... to add to the above, 40 bytes is the length of IPV6 header.
141 # The ipv6.len only contains length of the payload and not the header
142 pkt_len = Ether(buf)[u"IPv6"].plen + 14 + 40
145 elif ether_type == ETH_P_ARP:
146 pkt = Ether(buf[:20])
147 if not pkt.haslayer(ARP):
148 raise RuntimeError(u"Incomplete ARP packet")
149 # len(eth) + arp(2 hw addr type + 2 proto addr type
150 # + 1b len + 1b len + 2b operation)
153 pkt_len += 2 * pkt.getlayer(ARP).hwlen
154 pkt_len += 2 * pkt.getlayer(ARP).plen
157 elif ether_type == 32821: # RARP (Reverse ARP)
158 pkt = Ether(buf[:20])
159 pkt.type = ETH_P_ARP # Change to ARP so it works with scapy
161 if not pkt.haslayer(ARP):
163 raise RuntimeError(u"Incomplete RARP packet")
165 # len(eth) + arp(2 hw addr type + 2 proto addr type
166 # + 1b len + 1b len + 2b operation)
168 pkt_len += 2 * pkt.getlayer(ARP).hwlen
169 pkt_len += 2 * pkt.getlayer(ARP).plen
173 raise RuntimeError(f"Unknown protocol {ether_type}")
178 if len(buf) < pkt_len:
181 return buf[0:pkt_len]
184 def packet_reader(interface_name, queue):
185 """Sub-process routine that reads packets and puts them to queue.
187 This function is meant to be run in separate subprocess and is in tight
188 loop reading raw packets from interface passed as parameter.
190 :param interface_name: Name of interface to read packets from.
191 :param queue: Queue in which this function will push incoming packets.
192 :type interface_name: str
193 :type queue: multiprocessing.Queue
195 sock = conf.L2listen(iface=interface_name, type=ETH_P_ALL)
198 pkt = sock.recv(0x7fff)
202 class RxQueue(PacketVerifier):
203 """Receive queue object.
205 This object creates raw socket, reads packets from it and provides
206 function to access them.
208 :param interface_name: Which interface to bind to.
209 :type interface_name: str
211 def __init__(self, interface_name):
212 PacketVerifier.__init__(self, interface_name)
213 self._sock = conf.L2listen(iface=interface_name, type=ETH_P_ALL)
215 def recv(self, timeout=3, ignore=None, verbose=True):
216 """Read next received packet.
218 Returns scapy's Ether() object created from next packet in the queue.
219 Queue is being filled in parallel in subprocess. If no packet
220 arrives in given timeout None is returned.
222 If the list of packets to ignore is given, they are logged
223 but otherwise ignored upon arrival, not adding to the timeout.
224 Each time a packet is ignored, it is removed from the ignored list.
226 :param timeout: How many seconds to wait for next packet.
227 :param ignore: List of packets that should be ignored.
228 :param verbose: Used to suppress detailed logging of received packets.
233 :returns: Ether() initialized object from packet data.
236 time_end = time.monotonic() + timeout
237 ignore = ignore if ignore else list()
238 # Auto pad all packets in ignore list
239 ignore = [str(auto_pad(ig_pkt)) for ig_pkt in ignore]
241 time_now = time.monotonic()
242 if time_now >= time_end:
244 timedelta = time_end - time_now
245 rlist, _, _ = select.select([self._sock], [], [], timedelta)
246 if self._sock not in rlist:
247 # Might have been an interrupt.
249 pkt = self._sock.recv(0x7fff)
250 pkt_pad = str(auto_pad(pkt))
251 print(f"Received packet on {self._ifname} of len {len(pkt)}")
253 if hasattr(pkt, u"show2"):
256 # Never happens in practice, but Pylint does not know that.
257 print(f"Unexpected instance: {pkt!r}")
259 if pkt_pad in ignore:
260 ignore.remove(pkt_pad)
261 print(u"Received packet ignored.")
266 class TxQueue(PacketVerifier):
267 """Transmission queue object.
269 This object is used to send packets over RAW socket on a interface.
271 :param interface_name: Which interface to send packets from.
272 :type interface_name: str
274 def __init__(self, interface_name):
275 PacketVerifier.__init__(self, interface_name)
276 self._sock = conf.L2socket(iface=interface_name, type=ETH_P_ALL)
278 def send(self, pkt, verbose=True):
279 """Send packet out of the bound interface.
281 :param pkt: Packet to send.
282 :param verbose: Used to suppress detailed logging of sent packets.
283 :type pkt: string or scapy Packet derivative.
287 print(f"Sending packet out of {self._ifname} of len {len(pkt)}")
296 """Class for network interfaces. Contains methods for sending and receiving
298 def __init__(self, if_name):
299 """Initialize the interface class.
301 :param if_name: Name of the interface.
304 self.if_name = if_name
305 self.sent_packets = []
306 self.rxq = RxQueue(if_name)
307 self.txq = TxQueue(if_name)
309 def send_pkt(self, pkt):
310 """Send the provided packet out the interface."""
311 self.sent_packets.append(pkt)
314 def recv_pkt(self, timeout=3):
315 """Read one packet from the interface's receive queue.
317 :param timeout: Timeout value in seconds.
319 :returns: Ether() initialized object from packet data.
322 return self.rxq.recv(timeout, self.sent_packets)
325 def create_gratuitous_arp_request(src_mac, src_ip):
326 """Creates scapy representation of gratuitous ARP request."""
327 return (Ether(src=src_mac, dst=u"ff:ff:ff:ff:ff:ff") /
328 ARP(psrc=src_ip, hwsrc=src_mac, pdst=src_ip)
332 def auto_pad(packet):
333 """Pads zeroes at the end of the packet if the total packet length is less
334 then 64 bytes in case of IPv4 or 78 bytes in case of IPv6.
336 min_len = 78 if packet.haslayer(IPv6) else 64
337 pad_layer = Raw if packet.haslayer(Raw) \
338 else Padding if packet.haslayer(Padding) else None
340 packet[pad_layer].load += (b"\0" * (min_len - len(packet)))
344 def checksum_equal(chksum1, chksum2):
345 """Compares two checksums in one's complement notation.
347 Checksums to be compared are calculated as 16 bit one's complement of the
348 one's complement sum of 16 bit words of some buffer.
349 In one's complement notation 0x0000 (positive zero) and 0xFFFF
350 (negative zero) are equivalent.
352 :param chksum1: First checksum.
353 :param chksum2: Second checksum.
354 :type chksum1: uint16
355 :type chksum2: uint16
357 :returns: True if checksums are equivalent, False otherwise.
360 if chksum1 == 0xFFFF:
362 if chksum2 == 0xFFFF:
364 return chksum1 == chksum2