trafgen(8) — Linux manual page


TRAFGEN(8)                 netsniff-ng toolkit                TRAFGEN(8)

NAME         top

       trafgen - a fast, multithreaded network packet generator

SYNOPSIS         top

       trafgen [options] [packet]

DESCRIPTION         top

       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

       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         top

       -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
              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

       -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:


       -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         top

       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

       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

       Packet content is delimited either by a comma or whitespace, or

          { 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,
          compile-time random:     rnd(<times>): rnd(128), rnd()
          runtime random numbers:  drnd(<times>): drnd(128), drnd()
          compile-time counter:    seqinc(<start-val>, <times>,
                                   seqdec(<start-val>, <times>,
          runtime counter (1byte): dinc(<min-val>, <max-val>,
                                   ddec(<min-val>, <max-val>,

       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>),
          const32(<content>), c32(<content>), const64(<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:


           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,

               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()),
                     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

               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 =>

                       [ Eth MAC (00:00:00:00:00:00 =>

                       [ Eth MAC (00:00:00:00:00:00 =>

                   2) trafgen -o lo --cpus 1 -n 3 '{ ipv4(da=,
                   da[0]=dinc()), tcp() }'

                       [ IPv4 Addr ( =>

                       [ IPv4 Addr ( =>

                       [ IPv4 Addr ( =>

           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:

               sa|saddr - Source MAC address (default: device MAC

               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>,

               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>,

               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

               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:

               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:

               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>,
                           id=<number>, flags=<number>, frag=<number>,
                           df, mf, da=<ip4_addr>, sa=<ip4_addr>,

               ver|version - Version field (default: 4)

               ihl - Header length in number of 32-bit words (default:

               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

               da|daddr - Destination IPv4 address (default:

               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:

               sa|saddr - Source IPv6 address (default: device IPv6

               da|daddr - Destination IPv6 address (default:

           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:

               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:

           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>,

               sp|sport - Source port (default: 0)

               dp|dport - Destination port (default: 0)

               len|length - Length of UDP header and data (calculated by

               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>,

               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:

                 "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 */
            /* IPv4 Version, IHL, TOS */
            0b01000101, 0,
            /* IPv4 Total Len */
            /* IPv4 Ident */
            /* IPv4 Flags, Frag Off */
            0b01000000, 0,
            /* IPv4 TTL */
            /* Proto TCP */
            /* IPv4 Checksum (IP header from, to) */
            csumip(14, 33),
            /* Source IP */
            /* Dest IP */
            /* TCP Source Port */
            /* TCP Dest Port */
            /* TCP Sequence Number */
            /* TCP Ackn. Number */
            /* TCP Header length + TCP SYN/ECN Flag */
            c16((8 << 12) | TCP_FLAG_SYN | TCP_FLAG_ECE)
            /* Window Size */
            /* 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 */

       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
            # id (note: runtime dynamic random)
            # 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
            const16(48054), # src port
            const16(43514), # dst port
            const16(20),    # udp length
            # udp checksum can be dyn calc via csumudp(offset ip, offset
            # which is csumudp(14, 34), but for udp its allowed to be
            # payload
            'A',  fill(0x41, 11),


       The above example rewritten using the header generation

            # --- 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=,
            # --- udp header ---
            udp(sport=48054, dport=43514, csum=0)
            # payload
            'A',  fill(0x41, 11),

USAGE EXAMPLE         top

       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
              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 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

       trafgen --dev eth0 --conf tcp_syn.cfg -u `id -u bob` -g `id -g
              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         top

       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

       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.

       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         top

       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

LEGAL         top

       trafgen is licensed under the GNU GPL version 2.0.

HISTORY         top

       trafgen was originally written for the netsniff-ng toolkit by
       Daniel Borkmann. It is currently maintained by Tobias Klauser
       <> and Daniel Borkmann

SEE ALSO         top

       netsniff-ng(8), mausezahn(8), ifpps(8), bpfc(8), flowtop(8),
       astraceroute(8), curvetun(8)

AUTHOR         top

       Manpage was written by Daniel Borkmann.

COLOPHON         top

       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

COLOPHON         top

       This page is part of the netsniff-ng (a free Linux networking
       toolkit) project.  Information about the project can be found at
       ⟨⟩.  If you have a bug report for this
       manual page, send it to  This page
       was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-02-01.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Linux                         03 March 2013                   TRAFGEN(8)

Pages that refer to this page: astraceroute(8)bpfc(8)curvetun(8)flowtop(8)ifpps(8)mausezahn(8)netsniff-ng(8)