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 │
  └────▲────┘        └────┬────┘
┌──────┼──────────────────┼──────┐
│ ┌────┴────┐        ┌────▼────┐ │
│ │ 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-rarp | --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-rarp             ARP response (default: False)
  --l2-rpvstp           Rapid Per-VLAN STP 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	00:00:00:00:00:00	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.
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.
~~Pause Frame~~	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/RSTP/MSTP	IEEE 802.3 + LLC	Unicast Source	01:80:C2:00:00:00	None	DSAP 0x42, SSAP 0x42	IEEE 802.1D, IEEE 802.1w, IEEE 802.1s, 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:

Name		Name	Last commit message	Last commit date
Latest commit History 8 Commits
crap		crap
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md
crap.py		crap.py
requirements.txt		requirements.txt
tests.sh		tests.sh

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Create RAndom Packets

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