Provided by: netsniff-ng_0.6.9-1_amd64 
NAME
trafgen - a fast, multithreaded network packet generator
SYNOPSIS
trafgen [options] [packet]
DESCRIPTION
trafgen is a fast, zero-copy network traffic generator for debugging, performance evaluation, and fuzz-
testing. trafgen utilizes the packet(7) socket interface of Linux which postpones complete control over
packet data and packet headers into the user space. It has a powerful packet configuration language,
which is rather low-level and not limited to particular protocols. Thus, trafgen can be used for many
purposes. Its only limitation is that it cannot mimic full streams resp. sessions. However, it is very
useful for various kinds of load testing in order to analyze and subsequently improve systems behaviour
under DoS attack scenarios, for instance.
trafgen is Linux specific, meaning there is no support for other operating systems, same as netsniff-
ng(8), thus we can keep the code footprint quite minimal and to the point. trafgen makes use of packet(7)
socket's TX_RING interface of the Linux kernel, which is a mmap(2)'ed ring buffer shared between user and
kernel space.
By default, trafgen starts as many processes as available CPUs, pins each of them to their respective CPU
and sets up the ring buffer each in their own process space after having compiled a list of packets to
transmit. Thus, this is likely the fastest one can get out of the box in terms of transmission
performance from user space, without having to load unsupported or non-mainline third-party kernel
modules. On Gigabit Ethernet, trafgen has a comparable performance to pktgen, the built-in Linux kernel
traffic generator, except that trafgen is more flexible in terms of packet configuration possibilities.
On 10-Gigabit-per-second Ethernet, trafgen might be slower than pktgen due to the user/kernel space
overhead but still has a fairly high performance for out of the box kernels.
trafgen has the potential to do fuzz testing, meaning a packet configuration can be built with random
numbers on all or certain packet offsets that are freshly generated each time a packet is sent out. With
a built-in IPv4 ping, trafgen can send out an ICMP probe after each packet injection to the remote host
in order to test if it is still responsive/alive. Assuming there is no answer from the remote host after
a certain threshold of probes, the machine is considered dead and the last sent packet is printed
together with the random seed that was used by trafgen. You might not really get lucky fuzz-testing the
Linux kernel, but presumably there are buggy closed-source embedded systems or network driver's firmware
files that are prone to bugs, where trafgen could help in finding them.
trafgen's configuration language is quite powerful, also due to the fact, that it supports C preprocessor
macros. A stddef.h is being shipped with trafgen for this purpose, so that well known defines from Linux
kernel or network programming can be reused. After a configuration file has passed the C preprocessor
stage, it is processed by the trafgen packet compiler. The language itself supports a couple of features
that are useful when assembling packets, such as built-in runtime checksum support for IP, UDP and TCP.
Also it has an expression evaluator where arithmetic (basic operations, bit operations, bit shifting,
...) on constant expressions is being reduced to a single constant on compile time. Other features are
''fill'' macros, where a packet can be filled with n bytes by a constant, a compile-time random number or
run-time random number (as mentioned with fuzz testing). Also, netsniff-ng(8) is able to convert a pcap
file into a trafgen configuration file, thus such a configuration can be further tweaked for a given
scenario.
OPTIONS
-i <cfg|pcap|->, -c <cfg|->, --in <cfg|pcap|->, --conf <cfg|->
Defines the input configuration file that can either be passed as a normal plain text file or via
stdin (''-''). Note that currently, if a configuration is passed through stdin, only 1 CPU will be
used. It is also possible to specify PCAP file with .pcap extension via -i/--in option, by
default packets will be sent at rate considering timestamp from PCAP file which might be reset via
the -b or -t option.
-o <dev|.pcap|.cfg>, -d <dev|.pcap|.cfg>, --out <dev|.pcap|.cfg>, --dev <dev|.pcap|.cfg>
Defines the outgoing networking device such as eth0, wlan0 and others or a *.pcap or *.cfg file.
Pcap and configuration files are identified by extension.
-p, --cpp
Pass the packet configuration to the C preprocessor before reading it into trafgen. This allows
#define and #include directives (e.g. to include definitions from system headers) to be used in
the trafgen configuration file.
-D <name>=<definition>, --define <name>=<definition>
Add macro definition for the C preprocessor to use it within trafgen file. This option is used in
combination with the -p/--cpp option.
-J, --jumbo-support
By default trafgen's ring buffer frames are of a fixed size of 2048 bytes. This means that if
you're expecting jumbo frames or even super jumbo frames to pass your line, then you will need to
enable support for that with the help of this option. However, this has the disadvantage of a
performance regression and a bigger memory footprint for the ring buffer.
-R, --rfraw
In case the output networking device is a wireless device, it is possible with trafgen to turn
this into monitor mode and create a mon<X> device that trafgen will be transmitting on instead of
wlan<X>, for instance. This enables trafgen to inject raw 802.11 frames. In case if the output is
a pcap file the link type is set to 127 (ieee80211 radio tap).
-s <ipv4>, --smoke-test <ipv4>
In case this option is enabled, trafgen will perform a smoke test. In other words, it will probe
the remote end, specified by an <ipv4> address, that is being ''attacked'' with trafgen network
traffic, if it is still alive and responsive. That means, after each transmitted packet that has
been configured, trafgen sends out ICMP echo requests and waits for an answer before it continues.
In case the remote end stays unresponsive, trafgen assumes that the machine has crashed and will
print out the content of the last packet as a trafgen packet configuration and the random seed
that has been used in order to reproduce a possible bug. This might be useful when testing
proprietary embedded devices. It is recommended to have a direct link between the host running
trafgen and the host being attacked by trafgen.
-n <0|uint>, --num <0|uint>
Process a number of packets and then exit. If the number of packets is 0, then this is equivalent
to infinite packets resp. processing until interrupted. Otherwise, a number given as an unsigned
integer will limit processing.
-r, --rand
Randomize the packet selection of the configuration file. By default, if more than one packet is
defined in a packet configuration, packets are scheduled for transmission in a round robin
fashion. With this option, they are selected randomly instread.
-P <uint>[-<uint>], --cpus <uint>[-<uint>]
Specify the number of processes trafgen shall fork(2) off or list exact CPUs to use. By default
trafgen will start as many processes as CPUs that are online and pin them to each, respectively. A
single integer within interval [1,CPUs] overrides number of processes, which will be spawned
starting from the first CPU. A pair of integers within interval [0,CPUs-1], and separated using
''-'' represents an interval of CPUs, which will be used to spawn worker processes.
-t <time>, --gap <time>
Specify a static inter-packet timegap in seconds, milliseconds, microseconds, or nanoseconds:
''<num>s/ms/us/ns''. If no postfix is given default to microseconds. If this option is given, then
instead of packet(7)'s TX_RING interface, trafgen will use sendto(2) I/O for network packets, even
if the <time> argument is 0. This option is useful for a couple of reasons:
1) comparison between sendto(2) and TX_RING performance,
2) low-traffic packet probing for a given interval,
3) ping-like debugging with specific payload patterns.
Furthermore, the TX_RING interface does not cope with interpacket gaps.
-b <rate>, --rate <rate>
Specify the packet send rate <num>pps/kpps/Mpps/B/kB/MB/GB/kbit/Mbit/Gbit/KiB/MiB/GiB units. Like
with the -t/--gap option, the packets are sent in slow mode.
-S <size>, --ring-size <size>
Manually define the TX_RING resp. TX_RING size in ''<num>KiB/MiB/GiB''. By default the size is
being determined based on the network connectivity rate.
-E <uint>, --seed <uint>
Manually set the seed for pseudo random number generator (PRNG) in trafgen. By default, a random
seed from /dev/urandom is used to feed glibc's PRNG. If that fails, it falls back to the unix
timestamp. It can be useful to set the seed manually in order to be able to reproduce a trafgen
session, e.g. after fuzz testing.
-u <uid>, --user <uid> resp. -g <gid>, --group <gid>
After ring setup, drop privileges to a non-root user/group combination.
-H, --prio-high
Set this process as a high priority process in order to achieve a higher scheduling rate resp. CPU
time. This is however not the default setting, since it could lead to starvation of other
processes, for example low priority kernel threads.
-A, --no-sock-mem
Do not change systems default socket memory setting during testrun. Default is to boost socket
buffer memory during the test to:
/proc/sys/net/core/rmem_default:4194304
/proc/sys/net/core/wmem_default:4194304
/proc/sys/net/core/rmem_max:104857600
/proc/sys/net/core/wmem_max:104857600
-Q, --notouch-irq
Do not reassign the NIC's IRQ CPU affinity settings.
-q, --qdisc-path
Since Linux 3.14, the kernel supports a socket option PACKET_QDISC_BYPASS, which trafgen enables
by default. This options disables the qdisc bypass, and uses the normal send path through the
kernel's qdisc (traffic control) layer, which can be usefully for testing the qdisc path.
-V, --verbose
Let trafgen be more talkative and let it print the parsed configuration and some ring buffer
statistics.
-e, --example
Show a built-in packet configuration example. This might be a good starting point for an initial
packet configuration scenario.
-C, --no-cpu-stats
Do not print CPU time statistics on exit.
-v, --version
Show version information and exit.
-h, --help
Show user help and exit.
SYNTAX
trafgen's packet configuration syntax is fairly simple. The very basic things one needs to know is that a
configuration file is a simple plain text file where packets are defined. It can contain one or more
packets. Packets are enclosed by opening '{' and closing '}' braces, for example:
{ /* packet 1 content goes here ... */ }
{ /* packet 2 content goes here ... */ }
Alternatively, packets can also be specified directly on the command line, using the same syntax as used
in the configuration files.
When trafgen is started using multiple CPUs (default), then each of those packets will be scheduled for
transmission on all CPUs by default. However, it is possible to tell trafgen to schedule a packet only on
a particular CPU:
cpu(1): { /* packet 1 content goes here ... */ }
cpu(2-3): { /* packet 2 content goes here ... */ }
Thus, in case we have a 4 core machine with CPU0-CPU3, packet 1 will be scheduled only on CPU1, packet 2
on CPU2 and CPU3. When using trafgen with --num option, then these constraints will still be valid and
the packet is fairly distributed among those CPUs.
Packet content is delimited either by a comma or whitespace, or both:
{ 0xca, 0xfe, 0xba 0xbe }
Packet content can be of the following:
hex bytes: 0xca, xff
decimal: 42
binary: 0b11110000, b11110000
octal: 011
character: 'a'
string: "hello world"
shellcode: "\x31\xdb\x8d\x43\x17\x99\xcd\x80\x31\xc9"
Thus, a quite useless packet configuration might look like this (one can verify this when running this
with trafgen in combination with -V):
{ 0xca, 42, 0b11110000, 011, 'a', "hello world",
"\x31\xdb\x8d\x43\x17\x99\xcd\x80\x31\xc9" }
There are a couple of helper functions in trafgen's language to make life easier to write configurations:
i) Fill with garbage functions:
byte fill function: fill(<content>, <times>): fill(0xca, 128)
compile-time random: rnd(<times>): rnd(128), rnd()
runtime random numbers: drnd(<times>): drnd(128), drnd()
compile-time counter: seqinc(<start-val>, <times>, <increment>)
seqdec(<start-val>, <times>, <decrement>)
runtime counter (1byte): dinc(<min-val>, <max-val>, <increment>)
ddec(<min-val>, <max-val>, <decrement>)
ii) Checksum helper functions (packet offsets start with 0):
IP/ICMP checksum: csumip/csumicmp(<off-from>, <off-to>)
UDP checksum: csumudp(<off-iphdr>, <off-udpdr>)
TCP checksum: csumtcp(<off-iphdr>, <off-tcphdr>)
UDP checksum (IPv6): csumudp6(<off-ip6hdr>, <off-udpdr>)
TCP checksum (IPv6): csumtcp6(<off-ip6hdr>, <off-tcphdr>)
iii) Multibyte functions, compile-time expression evaluation:
const8(<content>), c8(<content>), const16(<content>), c16(<content>),
const32(<content>), c32(<content>), const64(<content>), c64(<content>)
These functions write their result in network byte order into the packet configuration, e.g.
const16(0xaa) will result in ''00 aa''. Within c*() functions, it is possible to do some arithmetics:
-,+,*,/,%,&,|,<<,>>,^ E.g. const16((((1<<8)+0x32)|0b110)*2) will be evaluated to ''02 6c''.
iv) Protocol header functions:
The protocol header functions allow to fill protocol header fields by using following generic syntax:
<proto>(<field>=<value>,<field2>=<value2>,...,<field3>,...)
If a field is not specified, then a default value will be used (usually 0). Protocol fields might be
set in any order. However, the offset of the fields in the resulting packet is according to the
respective protocol.
Each field might be set with a function which generates field value at runtime by increment or
randomize it. For L3/L4 protocols the checksum is calculated automatically if the field was changed
dynamically by specified function. The following field functions are supported:
dinc - increment field value at runtime. By default increment step is '1'. min and max
parameters are used to increment field only in the specified range, by default original field
value is used. If the field length is greater than 4 then last 4 bytes are incremented only
(useful for MAC and IPv6 addresses):
<field> = dinc() | dinc(min, max) | dinc(min, max, step)
drnd - randomize field value at runtime. min and max parameters are used to randomize field only
in the specified range:
<field> = drnd() | drnd(min, max)
Example of using dynamic functions:
{
eth(saddr=aa:bb:cc:dd:ee:ff, saddr=dinc()),
ipv4(saddr=dinc()),
udp(sport=dinc(1, 13, 2), dport=drnd(80, 100))
}
Fields might be further manipulated with a function at a specific offset:
<field>[<index>] | <field>[<index>:<length>]
<index> - relative field offset with range 0..<field.len> - 1
<length> - length/size of the value which will be set; either 1, 2 or 4 bytes (default: 1)
The <index> starts from the field's first byte in network order.
The syntax is similar to the one used in pcap filters (man pcap-filter) for matching header field
at a specified offset.
Examples of using field offset (showing the effect in a shortenet output from netsniff-ng):
1) trafgen -o lo --cpus 1 -n 3 '{ eth(da=11:22:33:44:55:66, da[0]=dinc()), tcp() }'
[ Eth MAC (00:00:00:00:00:00 => 11:22:33:44:55:66)
[ Eth MAC (00:00:00:00:00:00 => 12:22:33:44:55:66)
[ Eth MAC (00:00:00:00:00:00 => 13:22:33:44:55:66)
2) trafgen -o lo --cpus 1 -n 3 '{ ipv4(da=1.2.3.4, da[0]=dinc()), tcp() }'
[ IPv4 Addr (127.0.0.1 => 1.2.3.4)
[ IPv4 Addr (127.0.0.1 => 2.2.3.4)
[ IPv4 Addr (127.0.0.1 => 3.2.3.4)
All required lower layer headers will be filled automatically if they were not specified by the user.
The headers will be filled in the order they were specified. Each header will be filled with some
mimimum required set of fields.
Supported protocol headers:
Ethernet : eth(da=<mac>, sa=<mac>, type=<number>)
da|daddr - Destination MAC address (default: 00:00:00:00:00:00)
sa|saddr - Source MAC address (default: device MAC address)
etype|type|prot|proto - Ethernet type (default: 0)
PAUSE (IEEE 802.3X) : pause(code=<number>, time=<number>)
code - MAC Control opcode (default: 0x0001)
time - Pause time (default: 0)
By default Ethernet header is added with a fields:
Ethernet type - 0x8808
Destination MAC address - 01:80:C2:00:00:01
PFC : pfc(pri|prio(<number>)=<number>, time(<number>)=<number>)
code - MAC Control opcode (default: 0x0101)
pri|prio - Priority enable vector (default: 0)
pri|prio(<number>) - Enable/disable (0 - disable, 1 - enable) pause for priority <number>
(default: 0)
time(<number>) - Set pause time for priority <number> (default: 0)
By default Ethernet header is added with a fields:
Ethernet type - 0x8808
Destination MAC address - 01:80:C2:00:00:01
VLAN : vlan(tpid=<number>, id=<number>, dei=<number>, tci=<number>, pcp=<number>, 1q, 1ad)
tpid|prot|proto - Tag Protocol Identifier (TPID) (default: 0x8100)
tci - Tag Control Information (TCI) field (VLAN Id + PCP + DEI) (default: 0)
dei|cfi - Drop Eligible Indicator (DEI), formerly Canonical Format Indicator (CFI) (default: 0)
pcp - Priority code point (PCP) (default: 0)
id - VLAN Identifier (default: 0)
1q - Set 802.1q header (TPID: 0x8100)
1ad - Set 802.1ad header (TPID: 0x88a8)
By default, if the lower level header is Ethernet, its EtherType is set to 0x8100 (802.1q).
MPLS : mpls(label=<number>, tc|exp=<number>, last=<number>, ttl=<number>)
label|lbl - MPLS label value (default: 0)
tclass|tc|exp - Traffic Class for QoS field (default: 0)
last - Bottom of stack S-flag (default: 1 for most last label)
ttl - Time To Live (TTL) (default: 0)
By default, if the lower level header is Ethernet, its EtherType is set to 0x8847 (MPLS Unicast). S-
flag is set automatically to 1 for the last label and resets to 0 if the lower MPLS label was added
after.
ARP : arp(htype=<number>, ptype=<number>, op=<request|reply|number>, request, reply, smac=<mac>,
sip=<ip4_addr>, tmac=<mac>, tip=<ip4_addr>)
htype - ARP hardware type (default: 1 [Ethernet])
ptype - ARP protocol type (default: 0x0800 [IPv4])
op - ARP operation type (request/reply) (default: request)
req|request - ARP Request operation type
reply - ARP Reply operation type
smac|sha - Sender hardware (MAC) address (default: device MAC address)
sip|spa - Sender protocol (IPv4) address (default: device IPv4 address)
tmac|tha - Target hardware (MAC) address (default: 00:00:00:00:00:00)
tip|tpa - Target protocol (IPv4) address (default: device IPv4 address)
By default, the ARP operation field is set to request and the Ethernet destination MAC address is set
to the broadcast address (ff:ff:ff:ff:ff:ff).
IPv4 : ip4|ipv4(ihl=<number>, ver=<number>, len=<number>, csum=<number>, ttl=<number>, tos=<number>,
dscp=<number>, ecn=<number>,
id=<number>, flags=<number>, frag=<number>, df, mf, da=<ip4_addr>, sa=<ip4_addr>,
prot[o]=<number>)
ver|version - Version field (default: 4)
ihl - Header length in number of 32-bit words (default: 5)
tos - Type of Service (ToS) field (default: 0)
dscp - Differentiated Services Code Point (DSCP, DiffServ) field (default: 0)
ecn - Explicit Congestion Notification (ECN) field (default: 0)
len|length - Total length of header and payload (calculated by default)
id - IPv4 datagram identification (default: 0)
flags - IPv4 flags value (DF, MF) (default: 0)
df - Don't fragment (DF) flag (default: 0)
mf - More fragments (MF) flag (default: 0)
frag - Fragment offset field in number of 8 byte blocks (default: 0)
ttl - Time to live (TTL) field (default: 0)
csum - Header checksum (calculated by default)
sa|saddr - Source IPv4 address (default: device IPv4 address)
da|daddr - Destination IPv4 address (default: 0.0.0.0)
prot|proto - IPv4 protocol number (default: 0)
By default, if the lower level header is Ethernet, its EtherType field is set to 0x0800 (IPv4). If
the lower level header is IPv4, its protocol field is set to 0x4 (IP-in-IP).
IPv6 : ip6|ipv6(ver=<number>, class=<number>, flow=<number> len=<number>, nexthdr=<number>,
hoplimit=<number>,
da=<ip6_addr>, sa=<ip6_addr>)
ver|version - Version field (default: 6)
tc|tclass - Traffic class (default: 0)
fl|flow - Flow label (default: 0)
len|length - Payload length (calculated by default)
nh|nexthdr - Type of next header, i.e. transport layer protocol number (default: 0)
hl|hoplimit|ttl - Hop limit, i.e. time to live (default: 0)
sa|saddr - Source IPv6 address (default: device IPv6 address)
da|daddr - Destination IPv6 address (default: 0:0:0:0:0:0:0:0)
By default, if the lower level header is Ethernet, its EtherType field is set to 0x86DD (IPv6).
ICMPv4 : icmp4|icmpv4(type=<number>, code=<number>, echorequest, echoreply, csum=<number>,
mtu=<number>, seq=<number>, id=<number>, addr=<ip4_addr>)
type - Message type (default: 0 - Echo reply)
code - Message code (default: 0)
echorequest - ICMPv4 echo (ping) request (type: 8, code: 0)
echoreply - ICMPv4 echo (ping) reply (type: 0, code: 0)
csum - Checksum of ICMPv4 header and payload (calculated by default)
mtu - Next-hop MTU field used in 'Datagram is too big' message type (default; 0)
seq - Sequence number used in Echo/Timestamp/Address mask messages (default: 0)
id - Identifier used in Echo/Timestamp/Address mask messages (default: 0)
addr - IPv4 address used in Redirect messages (default: 0.0.0.0)
Example ICMP echo request (ping):
{ icmpv4(echorequest, seq=1, id=1326) }
ICMPv6 : icmp6|icmpv6(type=<number>, echorequest, echoreply, code=<number>, csum=<number>)
type - Message type (default: 0)
code - Code (default: 0)
echorequest - ICMPv6 echo (ping) request
echoreply - ICMPv6 echo (ping) reply
csum - Message checksum (calculated by default)
By default, if the lower level header is IPv6, its Next Header field is set to 58 (ICMPv6).
UDP : udp(sp=<number>, dp=<number>, len=<number>, csum=<number>)
sp|sport - Source port (default: 0)
dp|dport - Destination port (default: 0)
len|length - Length of UDP header and data (calculated by default)
csum - Checksum field over IPv4 pseudo header (calculated by default)
By default, if the lower level header is IPv4, its protocol field is set to 0x11 (UDP).
TCP : tcp(sp=<number>, dp=<number>, seq=<number>, aseq|ackseq=<number>, doff|hlen=<number>, cwr,
ece|ecn, urg, ack, psh, rst, syn, fin, win|window=<number>, csum=<number>, urgptr=<number>)
sp|sport - Source port (default: 0)
dp|dport - Destination port (default: 0)
seq - Sequence number (default: 0)
aseq|ackseq - Acknowledgement number (default: 0)
doff|hlen - Header size (data offset) in number of 32-bit words (default: 5)
cwr - Congestion Window Reduced (CWR) flag (default: 0)
ece|ecn - ECN-Echo (ECE) flag (default: 0)
urg - Urgent flag (default: 0)
ack - Acknowledgement flag (default: 0)
psh - Push flag (default: 0)
rst - Reset flag (default: 0)
syn - Synchronize flag (default: 0)
fin - Finish flag (default: 0)
win|window - Receive window size (default: 0)
csum - Checksum field over IPv4 pseudo header (calculated by default)
urgptr - Urgent pointer (default: 0)
By default, if the lower level header is IPv4, its protocol field is set to 0x6 (TCP).
Simple example of a UDP Echo packet:
{
eth(da=11:22:33:44:55:66),
ipv4(daddr=1.2.3.4)
udp(dp=7),
"Hello world"
}
Furthermore, there are two types of comments in trafgen configuration files:
1. Multi-line C-style comments: /* put comment here */
2. Single-line Shell-style comments: # put comment here
Next to all of this, a configuration can be passed through the C preprocessor before the trafgen compiler
gets to see it with option --cpp. To give you a taste of a more advanced example, run ''trafgen -e'',
fields are commented:
/* Note: dynamic elements make trafgen slower! */
#include <stddef.h>
{
/* MAC Destination */
fill(0xff, ETH_ALEN),
/* MAC Source */
0x00, 0x02, 0xb3, drnd(3),
/* IPv4 Protocol */
c16(ETH_P_IP),
/* IPv4 Version, IHL, TOS */
0b01000101, 0,
/* IPv4 Total Len */
c16(59),
/* IPv4 Ident */
drnd(2),
/* IPv4 Flags, Frag Off */
0b01000000, 0,
/* IPv4 TTL */
64,
/* Proto TCP */
0x06,
/* IPv4 Checksum (IP header from, to) */
csumip(14, 33),
/* Source IP */
drnd(4),
/* Dest IP */
drnd(4),
/* TCP Source Port */
drnd(2),
/* TCP Dest Port */
c16(80),
/* TCP Sequence Number */
drnd(4),
/* TCP Ackn. Number */
c32(0),
/* TCP Header length + TCP SYN/ECN Flag */
c16((8 << 12) | TCP_FLAG_SYN | TCP_FLAG_ECE)
/* Window Size */
c16(16),
/* TCP Checksum (offset IP, offset TCP) */
csumtcp(14, 34),
/* TCP Options */
0x00, 0x00, 0x01, 0x01, 0x08, 0x0a, 0x06,
0x91, 0x68, 0x7d, 0x06, 0x91, 0x68, 0x6f,
/* Data blob */
"gotcha!",
}
Another real-world example by Jesper Dangaard Brouer [1]:
{
# --- ethernet header ---
0x00, 0x1b, 0x21, 0x3c, 0x9d, 0xf8, # mac destination
0x90, 0xe2, 0xba, 0x0a, 0x56, 0xb4, # mac source
const16(0x0800), # protocol
# --- ip header ---
# ipv4 version (4-bit) + ihl (4-bit), tos
0b01000101, 0,
# ipv4 total len
const16(40),
# id (note: runtime dynamic random)
drnd(2),
# ipv4 3-bit flags + 13-bit fragment offset
# 001 = more fragments
0b00100000, 0,
64, # ttl
17, # proto udp
# dynamic ip checksum (note: offsets are zero indexed)
csumip(14, 33),
192, 168, 51, 1, # source ip
192, 168, 51, 2, # dest ip
# --- udp header ---
# as this is a fragment the below stuff does not matter too much
const16(48054), # src port
const16(43514), # dst port
const16(20), # udp length
# udp checksum can be dyn calc via csumudp(offset ip, offset tcp)
# which is csumudp(14, 34), but for udp its allowed to be zero
const16(0),
# payload
'A', fill(0x41, 11),
}
[1] https://marc.info/?l=linux-netdev&m=135903630614184
The above example rewritten using the header generation functions:
{
# --- ethernet header ---
eth(da=00:1b:21:3c:9d:f8, sa=90:e2:ba:0a:56:b4)
# --- ip header ---
ipv4(id=drnd(), mf, ttl=64, sa=192.168.51.1, da=192.168.51.2)
# --- udp header ---
udp(sport=48054, dport=43514, csum=0)
# payload
'A', fill(0x41, 11),
}
USAGE EXAMPLE
trafgen --dev eth0 --conf trafgen.cfg
This is the most simple and, probably, the most common use of trafgen. It will generate traffic
defined in the configuration file ''trafgen.cfg'' and transmit this via the ''eth0'' networking
device. All online CPUs are used.
trafgen --dev eth0 --conf trafgen.cfg --cpus 2-4
Instead of using all online CPUs, transmit traffic from CPUs 2, 3, and 4.
trafgen -e | trafgen -i - -o lo --cpp -n 1
This is an example where we send one packet of the built-in example through the loopback device.
The example configuration is passed via stdin and also through the C preprocessor before trafgen's
packet compiler will see it.
trafgen --dev eth0 --conf fuzzing.cfg --smoke-test 10.0.0.1
Read the ''fuzzing.cfg'' packet configuration file (which contains drnd() calls) and send out the
generated packets to the ''eth0'' device. After each sent packet, ping probe the attacked host
with address 10.0.0.1 to check if it's still alive. This also means, that we utilize 1 CPU only,
and do not use the TX_RING, but sendto(2) packet I/O due to ''slow mode''.
trafgen --dev wlan0 --rfraw --conf beacon-test.txf -V --cpus 2
As an output device ''wlan0'' is used and put into monitoring mode, thus we are going to transmit
raw 802.11 frames through the air. Use the ''beacon-test.txf'' configuration file, set trafgen
into verbose mode and use only 2 CPUs starting from CPU 0.
trafgen --dev em1 --conf frag_dos.cfg --rand --gap 1000us
Use trafgen in sendto(2) mode instead of TX_RING mode and sleep after each sent packet a static
timegap for 1000us. Generate packets from ''frag_dos.cfg'' and select next packets to send
randomly instead of a round-robin fashion. The output device for packets is ''em1''.
trafgen --dev eth0 --conf icmp.cfg --rand --num 1400000 -k1000
Send only 1400000 packets using the ''icmp.cfg'' configuration file and then exit trafgen. Select
packets randomly from that file for transmission and send them out via ''eth0''. Also, trigger the
kernel every 1000us for batching the ring frames from user space (default is 10us).
trafgen --dev eth0 --conf tcp_syn.cfg -u `id -u bob` -g `id -g bob`
Send out packets generated from the configuration file ''tcp_syn.cfg'' via the ''eth0'' networking
device. After setting up the ring for transmission, drop credentials to the non-root user/group
bob/bob.
trafgen --dev eth0 '{ fill(0xff, 6), 0x00, 0x02, 0xb3, rnd(3), c16(0x0800), fill(0xca, 64) }' -n 1
Send out 1 invaid IPv4 packet built from command line to all hosts.
NOTE
trafgen can saturate a Gigabit Ethernet link without problems. As always, of course, this depends on your
hardware as well. Not everywhere where it says Gigabit Ethernet on the box, will you reach almost
physical line rate! Please also read the netsniff-ng(8) man page, section NOTE for further details about
tuning your system e.g. with tuned(8).
If you intend to use trafgen on a 10-Gbit/s Ethernet NIC, make sure you are using a multiqueue tc(8)
discipline, and make sure that the packets you generate with trafgen will have a good distribution among
tx_hashes so that you'll actually make use of multiqueues.
For introducing bit errors, delays with random variation and more, there is no built-in option in
trafgen. Rather, one should reuse existing methods for that which integrate nicely with trafgen, such as
tc(8) with its different disciplines, i.e. netem.
For more complex packet configurations, it is recommended to use high-level scripting for generating
trafgen packet configurations in a more automated way, i.e. also to create different traffic
distributions that are common for industrial benchmarking:
Traffic model Distribution
IMIX 64:7, 570:4, 1518:1
Tolly 64:55, 78:5, 576:17, 1518:23
Cisco 64:7, 594:4, 1518:1
RPR Trimodal 64:60, 512:20, 1518:20
RPR Quadrimodal 64:50, 512:15, 1518:15, 9218:20
The low-level nature of trafgen makes trafgen rather protocol independent and therefore useful in many
scenarios when stress testing is needed, for instance. However, if a traffic generator with higher level
packet descriptions is desired, netsniff-ng's mausezahn(8) can be of good use as well.
For smoke/fuzz testing with trafgen, it is recommended to have a direct link between the host you want to
analyze (''victim'' machine) and the host you run trafgen on (''attacker'' machine). If the ICMP reply
from the victim fails, we assume that probably its kernel crashed, thus we print the last sent packet
together with the seed and quit probing. It might be very unlikely to find such a ping-of-death on modern
Linux systems. However, there might be a good chance to find it on some proprietary (e.g. embedded)
systems or buggy driver firmwares that are in the wild. Also, fuzz testing can be done on raw 802.11
frames, of course. In case you find a ping-of-death, please mention that you were using trafgen in your
commit message of the fix!
BUGS
For old trafgen versions only, there could occur kernel crashes: we have fixed this bug in the mainline
and stable kernels under commit 7f5c3e3a8 (''af_packet: remove BUG statement in tpacket_destruct_skb'')
and also in trafgen.
Probably the best is if you upgrade trafgen to the latest version.
LEGAL
trafgen is licensed under the GNU GPL version 2.0.
HISTORY
trafgen was originally written for the netsniff-ng toolkit by Daniel Borkmann. It is currently maintained
by Tobias Klauser <tklauser@distanz.ch> and Daniel Borkmann <dborkma@tik.ee.ethz.ch>.
SEE ALSO
netsniff-ng(8), mausezahn(8), ifpps(8), bpfc(8), flowtop(8), astraceroute(8), curvetun(8)
AUTHOR
Manpage was written by Daniel Borkmann.
COLOPHON
This page is part of the Linux netsniff-ng toolkit project. A description of the project, and information
about reporting bugs, can be found at http://netsniff-ng.org/.
Linux 03 March 2013 TRAFGEN(8)