.\" netsniff-ng - the packet sniffing beast .\" Copyright 2013 Daniel Borkmann. .\" Subject to the GPL, version 2. .TH TRAFGEN 8 "03 March 2013" "Linux" "netsniff-ng toolkit" .SH NAME trafgen \- a fast, multithreaded network packet generator .SH SYNOPSIS \fB trafgen\fR [\fIoptions\fR] .SH DESCRIPTION trafgen is a fast, zero-copy network traffic generator for debugging, performance evaluation and fuzz-testing purposes. 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 only, meaning there is no support for other operating systems just as in 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. On default, trafgen starts as many processes as CPUs that are online, 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, only 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 a possibility 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 then be further tweaked for a given scenario. .SH OPTIONS .SS -i , -c , --in , --conf TODO .SS -o , -d , --out , --dev TODO .SS -p, --cpp Pass the packet configuration to .SS -J, --jumbo-support On 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 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. .SS -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 device that trafgen will be transmitting on instead of wlan, for instance. This enables trafgen to inject raw 802.11 frames. .SS -s , --smoke-test TODO .SS -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. .SS -r, --rand Randomize the packet selection of the configuration file. On 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. .SS -P , --cpus Specify the number of processes trafgen shall fork(2) off. On default trafgen will start as many processes as CPUs that are online and pin them to each, respectively. Allowed value must be within interval [1,CPUs]. .SS -t , --gap Specify a static inter-packet timegap in micro-seconds. 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 argument is 0. This option is useful for a couple of reasons: i) comparison between sendto(2) and TX_RING performance, ii) low-traffic packet probing for a given interval, iii) ping-like debugging with specific payload patterns. Furthermore, the TX_RING interface does not cope with interpacket gaps. .SS -S , --ring-size Manually define the RX_RING resp. TX_RING size in ``KiB/MiB/GiB''. On default the size is being determined based on the network connectivity rate. .SS -k , --kernel-pull Manually define the interval in micro-seconds where the kernel should be triggered to batch process the ring buffer frames. On default, it is every 10us, but it can manually be prolonged, for instance.. .SS -E , --seed Manually set the seed for trafgen. On default, a random seed from /dev/urandom is being used to feed glibc's pseudo random number generator. If that fails, it falls back to the unix timestamp. It can be useful to set it up manually to be able to reproduce a trafgen session, e.g. after fuzz testing. .SS -u , --user resp. -g , --group After ring setup drop privileges to a non-root user/group combination. .SS -V, --verbose Let trafgen be more talkative and let it print the parsed configuration and some ring buffer statistics. .SS -e, --example Show a built-in packet configuration example. This might be a good starting point for an initial packet configuration scenario. .SS -v, --version Show versioning information. .SS -h, --help Show user help. .SH SYNTAX TODO .SH SOURCE EXAMPLES TODO .SH USAGE EXAMPLE TODO .SH 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, you'll 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 independant 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 togther 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! .SH BUGS When I start trafgen, my 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''). Either update your kernel to the latest version, e.g. clone and build it from git.kernel.org, to a stable kernel, or don't start multiple trafgen instances at once resp. start trafgen with flag -A to disable temporary socket memory adaptation! .SH LEGAL trafgen is licensed under the GNU GPL version 2.0. .SH HISTORY .B trafgen was originally written for the netsniff-ng toolkit by Daniel Borkmann. It is currently maintained by Tobias Klauser and Daniel Borkmann . .SH SEE ALSO .BR netsniff-ng (8), .BR mausezahn (8), .BR ifpps (8), .BR bpfc (8), .BR flowtop (8), .BR astraceroute (8), .BR curvetun (8) .SH AUTHOR Manpage was written by Daniel Borkmann.