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Create RAndom Packets

Overview

CRAP is a Python script which has a very basic work flow to test the transmission, and optionally, the reception of frames and packets.

CRAP runs in two modes, tx/transmit mode and rx/receive mode. If you only want to send traffic then you can simply run CRAP, which runs in tx mode by default, and choose the type of traffic you want to send. If you wish to verify the traffic is also received, you need to run a second copy of CRAP in rx mode. You also have to specify the same type of traffic in rx mode because CRAP only listens for incoming traffic of the specified type.

If you want to run tcpdump and manually capture traffic sent by CRAP yourself, rather than using rx mode, CRAP always prints a libpcap filter which can be used with tcpdump to capture the traffic, when it runs in tx mode.

A typical use case for CRAP is testing the transparency of a L2 VPN:

 ┌─────────┐ L2 VPN ┌─────────┐
 │ Router1 ┼────────► Router2 │
 └────▲さんかく────┘ └────┬────┘
┌──────┼──────────────────┼──────┐
│ ┌────┴────┐ ┌────▼────┐ │
│ │ CRAP Tx │ │ CRAP Rx │ │Linux Server
│ └─────────┘ └─────────┘ │
└────────────────────────────────┘

Features

The following output shows the traffic types CRAP can generated. See the Protocol Definitions section to learn exactly what kind of frame/packet CRAP sends.

$ python3 ./crap.py -h
usage: crap.py [-h] [-c COUNT] [-i INTERFACE] [-n] [-p PCAP] [-r] [-u] [--l2-qos L2_QOS] [--l3-qos L3_QOS] [-q QINQ] [-v VLAN]
 (--l2-arp | --l2-cdp | --l2-cfm | --l2-isis-l1-hello | --l2-isis-l2-hello | --l2-lacp | --l2-lldp | --l2-macsec | --l2-mstp | --l2-rarp | --l2-rstp | --l2-rpvstp | --l2-stp | --l3-bfdasync | --l3-bfdcontrol | --l3-bfdecho | --l3-bfdmicro | --l3-bgp | --l3-eigrp2v4hello | --l3-eigrp2v6hello | --l3-icmpv4echorequest | --l3-icmpv4echoreply | --l3-icmpv6echorequest | --l3-icmpv6echoreply | --l3-igmpv3query | --l3-igmpv3report | --l3-mldv2query | --l3-mldv2report | --l3-multicastv4 | --l3-multicastv6 | --l3-ospfv2hello | --l3-ospfv2lsa | --l3-ospfv3hello | --l3-ospfv3lsa | --l3-vrrpv2 | --l3-vrrpv3)
Create RAndom Packets - Send and receive packets using Scapy
options:
 -h, --help show this help message and exit
 -c COUNT, --count COUNT
 Number of packets to send (default: 5)
 -i INTERFACE, --interface INTERFACE
 Interface (default: veth0)
 -n, --no-pad Disable automatic padding of frames to be at least 64 bytes long (default: False)
 -p PCAP, --pcap PCAP PCAP file to write received frames to in Rx mode, or write transmitted frames to in Tx mode (default: None)
 -r, --rx Receive instead of transmit (default is tx) (default: False)
 -u, --unicast Send a unicast packet to populate the MAC tables in the network, with the unicast MAC address used for testing, before sending the chosen test frame type (default: False)
QoS Settings:
 Set a CoS/DSCP values
 --l2-qos L2_QOS Specify an 802.1P value. If -v is not used, and this is non-zero, traffic will be tagged with VLAN 0. (default: None)
 --l3-qos L3_QOS Specify a DSCP value. (default: None)
VLAN Tag(s):
 Add a VLAN tag(s)
 -q QINQ, --qinq QINQ Specify an inner VLAN tag (requires -v). Note: QinQ doesn't work with MacSec! (default: None)
 -v VLAN, --vlan VLAN Specify an outer VLAN tag (default: None)

Traffic Type:
 Type of traffic to tx/rx [REQUIRED]

 --l2-arp ARP request (default: False)
 --l2-cdp CDP message (default: False)
 --l2-cfm CFM CCM (default: False)
 --l2-isis-l1-hello IS-IS P2P Level 1 Hello (default: False)
 --l2-isis-l2-hello IS-IS P2P Level 2 Hello (default: False)
 --l2-lacp LACP message (default: False)
 --l2-lldp LLDP message (default: False)
 --l2-macsec MacSec message (default: False)
 --l2-mstp Multiple STP message (default: False)
 --l2-rarp ARP response (default: False)
 --l2-rstp Rapid STP message (default: False)
 --l2-rpvstp Rapid Per-VLAN STP (PVST+) message (default: False)
 --l2-stp STP message (default: False)
 --l3-bfdasync BFD message (async Mode) (default: False)
 --l3-bfdcontrol BFD Control message (default: False)
 --l3-bfdecho BFD message (echo Mode) (default: False)
 --l3-bfdmicro BFD Control message (Micro-BFD/BoB) (default: False)
 --l3-bgp BGP Keepalive message (default: False)
 --l3-eigrp2v4hello EIGRPv2 IPv4 Hello message (default: False)
 --l3-eigrp2v6hello EIGRPv2 IPv6 Hello message (default: False)
 --l3-icmpv4echorequest
 ICMPv4 Echo Request message (default: False)
 --l3-icmpv4echoreply ICMPv4 Echo Reply message (default: False)
 --l3-icmpv6echorequest
 ICMPv6 Echo Request message (default: False)
 --l3-icmpv6echoreply ICMPv6 Echo Reply message (default: False)
 --l3-igmpv3query IGMPv3 Query message (default: False)
 --l3-igmpv3report IGMPv3 Report message (default: False)
 --l3-mldv2query MLDv2 Query message (default: False)
 --l3-mldv2report MLDv2 Response message (default: False)
 --l3-multicastv4 IPv4 Multicast message (default: False)
 --l3-multicastv6 IPv4 Multicast message (default: False)
 --l3-ospfv2hello OSPFv2 Hello message (default: False)
 --l3-ospfv2lsa OSPFv2 LSA message (default: False)
 --l3-ospfv3hello OSPFv3 Hello message (default: False)
 --l3-ospfv3lsa OSPFv3 LSA message (default: False)
 --l3-vrrpv2 VRRPv2 IPV4 message (default: False)
 --l3-vrrpv3 VRRPv3 IPv6 message (default: False)

Install

  • (optional) Set up a Python virtual environment
sudo apt install --no-install-recommends python3-venv python3-pip
python3 -m venv --without-pip .venv && source .venv/bin/activate
  • Install the required Python modules:
python3 -m ensurepip
python3 -m pip install --upgrade pip
python3 -m pip install -r requirements.txt
  • You should be able to run the script now:
./crap.py -h

You need to run crap.py as root in order to send and receive raw frames. When using sudo a different Python interpreter is used than the one in the venv you just set up, which will be missing the dependencies, therefore you see sudo -E $(which python3) ./crap.py throughout this README. This is not needed if you are NOT using a venv or running in Docker.

Known Issues

  • QinQ in not currently supported for MacSec, only untagged or a single VLAN tag are supported by MacSec.

Quick Start Reference

Set up a veth pair and send traffic between them:

# Terminal 1
NS=scapy
sudo ip netns add $NS && \
sudo ip link add veth0 type veth peer name veth1 && \
sudo ip link set veth1 netns $NS && \
sudo ip netns exec $NS ip link set up dev veth1 && \
sudo ip link set up dev veth0
# Terminal 2
NS=scapy
sudo -E ip netns exec $NS $(which python3) ./crap.py -r -i veth1 --l3-mldv2query
sudo ip netns exec $NS wireshark -ki veth1
# Terminal 1
sudo -E $(which python3) ./crap.py --l3-mldv2query
# Clean-up
sudo ip netns delete $NS
sudo ip link del veth0 type veth peer name veth1

Detailed Example

Sending Traffic

Set up a pair of virtual interfaces which are linked together, and send some traffic into one of them:

  • Set up a pair of virtual interfaces:
NS=crap
sudo ip netns add $NS && \
sudo ip link add veth0 type veth peer name veth1 && \
sudo ip link set veth1 netns $NS && \
sudo ip netns exec $NS ip link set up dev veth1 && \
sudo ip link set up dev veth0
  • The minimum you need to specify, is the type of packet you want to send and the interface to send it on. In this example ARP requests are being sent:
sudo $(which python3) ./crap.py --l2-arp -i veth0
Using frame: <l2.Arp object at 0x7ff4a29846d0>
Packet data: <Ether dst=00:03:00:00:00:01 src=00:03:00:00:00:02 type=RARP |> <ARP op=is-at hwsrc=00:03:00:00:00:02 psrc=10.200.200.2 hwdst=00:03:00:00:00:01 pdst=10.200.200.1 |>
Filter data: ether src 00:03:00:00:00:01 and ether dst FF:FF:FF:FF:FF:FF and ether proto 0x0806
.....
Sent 5 packets.
# If using a virtual environment, you will need to specify the python interpreter for this environment, when using sudo:
sudo -E $(which python3) ./crap.py --l2-arp -i veth0
  • If you want to see the packets which were sent, start Wireshark on the other virtual interface:
NS=crap
sudo ip netns exec $NS wireshark -ki veth1

Receiving Traffic

In order to verify the traffic which was sent by CRAP into the first virtual interface, run CRAP on the second virtual interface in rx mode, and specify the kind of packet is needs to listen for. CRAP will generate a libpcap filter which only accepts the the specified type of packet.

  • Start listening on the second virtual interface for ARP packets:
NS=crap
sudo -E ip netns exec $NS $(which python3) ./crap.py --l2-arp -r -i veth1
Using frame: <l2.Arp object at 0x7ff7414c2e90>
Packet data: <Ether dst=00:03:00:00:00:01 src=00:03:00:00:00:02 type=RARP |> <ARP op=is-at hwsrc=00:03:00:00:00:02 psrc=10.200.200.2 hwdst=00:03:00:00:00:01 pdst=10.200.200.1 |>
Filter data: ether src 00:03:00:00:00:01 and ether dst FF:FF:FF:FF:FF:FF and ether proto 0x0806
Starting capture using filter: ether src 00:03:00:00:00:01 and ether dst FF:FF:FF:FF:FF:FF and ether proto 0x0806
  • From the first interface, send the ARP packets:
sudo -E $(which python3) ./crap.py -i veth0 --l2-arp
Using frame: <l2.Arp object at 0x7ff4a29846d0>
Packet data: <Ether dst=00:03:00:00:00:01 src=00:03:00:00:00:02 type=RARP |> <ARP op=is-at hwsrc=00:03:00:00:00:02 psrc=10.200.200.2 hwdst=00:03:00:00:00:01 pdst=10.200.200.1 |>
Filter data: ether src 00:03:00:00:00:01 and ether dst FF:FF:FF:FF:FF:FF and ether proto 0x0806
.....
Sent 5 packets.
  • On the second interface we see that the same number and type of frames which were transmitted, were received:
Captured 5 frames
  • Finally we can delete the virtual interfaces:
sudo ip netns delete $NS
sudo ip link del veth0 type veth peer name veth1

Protocol Definitions

The following table provides a definition of the of different protocols.

Control Protocol Format Src Mac Dst MAC Ethertype LLC/SNAP Description
ARP Ethernet II Unicast Source FF:FF:FF:FF:FF:FF 0x0806 None IPv4 ARP broadcast
BFD Control Ethernet II Unicast Source Unicast Destination 0x0800 None BFD Control packet over IPv4 with unicast source and destination IPs
BFD Control (Micro-BFD) Ethernet II Unicast Source 01:00:5E:90:00:01 0x0800 None BFD Control packet for Micro-BFD (BoB) over IPv4 with unicast source and destination IPs, to multicast destination MAC.
BFD Echo Ethernet II Unicast Source Unicast Destination 0x0800 None BFD Echo packet over IPv4 with own unicast address as source and destination IPs
BFD Echo (Async) Ethernet II Unicast Source Unicast Destination 0x0800 None BFD Echo packet over IPv4 with distinct unicast source and destination IPs
BGP Ethernet II Unicast Source Unicast Destination 0x0800/0x86DD None IPv4/6 packet with unicast source IP and unicast destination IP, with TCP source port or destination port set to 179
CDP IEEE 802.3 + LLC + SNAP Unicast Source 01:00:0C:CC:CC:CC None DSAP 0xAA, SSAP 0xAA, OUI: 0x00000C, protocol ID: 0x2000 Cisco Discovery Protocol
CFM Ethernet II Unicast Source 01:80:C2:00:00:30-3F 0x8902 None IEEE 802.1ag and Y.1731 Connectivity Fault Management.
EIGRP v2 Ethernet II Unicast Source 01:00:5E:00:00:0A / 33:33:00:00:00:0A 0x0800/0x86DD None IPv4/6 packets with unicast source IP, muticast destination IP (224.0.0.10/FF02::A), and IP protocol 88
E-LMI Ethernet II 01:80:C2:00:00:07 0x88EE None MEF-16 E-LMI Ethernet Local Management Interface
LACP Ethernet II Unicast Source 01:80:C2:00:00:02 0x8809 None IEEE 802.3ad / IEEE 802.1AX-2008 Link Aggregation Control Protocol.
LLDP Ethernet II Unicast Source 01:80:C2:00:00:0E 0x88CC None IEEE 802.1AB Link Layer Discovery Protocol
IGMPv3 Query Ethernet II Unicast Source Multicast Destination 0x0800 None IGMP packet with IPv4 multicast destination address (224.0.0.0/4) and matching multicast destination MAC.
IGMPv3 Response Ethernet II Unicast Source Multicast Destination 0x0800 None IGMP packet with IPv4 multicast destination address (224.0.0.0/4) and matching multicast destination MAC.
IS-IS L1 Hello IEEE 802.3 + LLC Unicast Source 01:80:C2:00:00:14 None DSAP 0xFE, SSAP 0xFE ISO/IEC 10589
IS-IS L2 Hello IEEE 802.3 + LLC Unicast Source 01:80:C2:00:00:15 None DSAP 0xFE, SSAP 0xFE ISO/IEC 10589
ES-IS IS->ES IEEE 802.8 + LLC Unicast Source 09:00:2B:00:00:04 None ISO/IEC 10589
ES-IS ES->IS IEEE 802.8 + LLC Unicast Source 09:00:2B:00:00:05 None ISO/IEC 10589
IPv4 Multicast Ethernet II Unicast Source Multicast Destination 0x0800 None IPv4 packets with a multicast destination IP (224.0.0.0/4) and matching multicast destination MAC.
IPv6 Multicast Ethernet II Unicast Source Multicast Destination 0x86DD None IPv6 packets with a multicast destination IP (FF00::/8) and matching multicast destination MAC.
MACSec Ethernet II Unicast Source Unicast Destination 0x88E5 None IEEE 802.1AE
MLDv2 Query Ethernet II Unicast Source Multicast Destination 0x86DD None ICMPv6 packet with IPv6 multicast destination address (FF02::16) and matching multicast destination MAC.
MLDv2 Report Ethernet II Unicast Source Multicast Destination 0x86DD None ICMPv6 packet with IPv6 multicast destination address (FF02::16) and matching multicast destination MAC.
MSTP IEEE 802.3 + LLC Unicast Source 01:80:C2:00:00:08 None DSAP 0x42, SSAP 0x42 IEEE 802.1s, IEEE 802.1q-2014
OAM Ethernet II 01:80:C2:00:00:02 0x8809 None IEEE 802.3ah Ethernet OAM uses the same destination MAC and Ethertype as LACP.
OSPFv2 Hello Ethernet II Unicast Source Multicast Destination 0x0800 None IPv4 packets with a multicast destination IP (224.0.0.5) and matching multicast destination MAC.
OSPFv2 LSA Ethernet II Unicast Source Multicast Destination 0x0800 None IPv4 packets with a multicast destination IP (224.0.0.5) and matching multicast destination MAC.
OSPFv3 Hello Ethernet II Unicast Source Multicast Destination 0x86DD None IPv6 packets with a multicast destination IP (FF02::5) and matching multicast destination MAC.
OSPFv3 LSA Ethernet II Unicast Source Multicast Destination 0x86DD None IPv6 packets with a multicast destination IP (FF02::5) and matching multicast destination MAC.
(削除) Pause Frame (削除ここまで) Ethernet II 01:80:C2:00:00:01 0x8808 None IEEE 802.3x Ethernet Flow Control. These must not be transported across the service as per the standard.
PVST+ IEEE 802.3 + LLC Unicast Source 01:00:0C:CC:CC:CD None DSAP 0xAA, SSAP 0xAA, OUI: 0x00000C, protocol ID: 0x010b Rapid Per-VLAN Spanning Tree
RARP Ethernet II Unicast Source Unicast Destination 0x8035 None IPv4 ARP reply from unicast source MAC, to unicast destination MAC
STP IEEE 802.3 + LLC Unicast Source 01:80:C2:00:00:00 None DSAP 0x42, SSAP 0x42 IEEE 802.1D, IEEE 802.1q-2014
RSTP IEEE 802.3 + LLC Unicast Source 01:80:C2:00:00:00 None DSAP 0x42, SSAP 0x42 IEEE 802.1w, IEEE 802.1q-2014
UDLD IEEE 802.3 + LLC + SNAP Unicast Source 01:00:0C:CC:CC:CC None DSAP 0xAA, SSAP 0xAA, OUI: 0x00000C, protocol ID: 0x0111 Unidirection Link Detection Protocol
VLAN Ethernet II Any Any 0x8100 None Single- and double-VLAN tagged frames.
VRRP v2 Ethernet II 00:00:5E:00: + VRRP GRP ID 01:00:5E:00:00:12 0x0800 None IPv4 packets with a unicast source IP and multicast destination IP (224.0.0.18)
VRRP v3 Ethernet II 00:00:5e:00: + VRRP GRP ID 01:00:5E:00:00:18/12 0x0800/0x86DD None IPv4/6 packets with a unicast source IP and multicast destination IP (224.0.0.18/FF02::12)
VTP IEEE 802.3 + LLC + SNAP Unicast Source 01:00:0C:CC:CC:CC None DSAP 0xAA, SSAP 0xAA, OUI: 0x00000C, protocol ID: 0x2003 Virtual Trunking Protocol

References:

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