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#LyX 1.3 created this file. For more info see http://www.lyx.org/ \lyxformat 221 \textclass article \language english \inputencoding latin1 \fontscheme times \graphics default \paperfontsize default \spacing single \papersize letterpaper \paperpackage a4 \use_geometry 1 \use_amsmath 0 \use_natbib 0 \use_numerical_citations 0 \paperorientation portrait \leftmargin 10mm \topmargin 10mm \rightmargin 10mm \bottommargin 15mm \secnumdepth 4 \tocdepth 3 \paragraph_separation skip \defskip medskip \quotes_language english \quotes_times 2 \papercolumns 1 \papersides 1 \paperpagestyle default \layout Title Tcpreplay 3.x Manual (BETA) \layout Author Aaron Turner \newline http://tcpreplay.sourceforge.net/ \layout Section* Notice \layout Standard This document is still in the process of being re-written due to the significant CLI and configuration file changes between versions 2.x and 3.x. For the definative source of configuration options, please see the tcpprep, tcprewrite, tcpreplay and tcpbridge man pages. \layout Section* Overview \layout Standard Tcpreplay is a suite of utilities for UNIX systems for editing and replaying network traffic which was previously captured by tools like tcpdump and ethereal. The goal of tcpreplay is to provide the means for providing reliable and repeatible means for testing a variety of network devices such as switches, router, firewalls, network intrusion detection and prevention systems (IDS and IPS). \layout Standard Tcpreplay provides the ability to classify traffic as client or server, edit packets at layers 2-4 and replay the traffic at arbitrary speeds onto a network for sniffing or through a device. \layout Standard Some of the advantages of using tcpreplay over using \begin_inset Quotes eld \end_inset exploit code \begin_inset Quotes erd \end_inset are: \layout Itemize Since tcpreplay emulates the victim and the attacker, you generally only need a tcpreplay box and the device under test (DUT) \layout Itemize Tests can include background traffic of entire networks without the cost and effort of setting up dozens of hosts or costly emulators \layout Itemize No need to have a \begin_inset Quotes eld \end_inset victim \begin_inset Quotes erd \end_inset host which needs to have the appropriate software installed, properly configure d and rebuilt after compromise \layout Itemize Less chance that a virus or trojan might escape your network and wreak havoc on your systems \layout Itemize Uses the open standard pcap file format for which dozens of command line and GUI utilities exist \layout Itemize Tests are fully repeatable without a complex test harnesses or network configura tion \layout Itemize Tests can be replayed at arbitrary speeds \layout Itemize Single command-line interface to learn and integrate into test harness \layout Itemize You only need to audit tcpreplay, rather then each and every exploit individuall y \layout Itemize Actively developed and supported by it's author \layout Subsection* Using this manual \layout Standard The goal of this manual is to provide an idea of what tcpreplay and it's utilities can do. It is not however intended to be a complete document which covers every possible use case or situation. It is also very much a work in progress and is far from complete and has numerous errors since a lot of things have changed since tcpreplay 2.x. It is expected that most of these issues will be ironed out before the offical 3.0 release is made. You should keep in mind the following conventions when reading this document: \layout Itemize Commands you should run from the command line \family typewriter are in monotype \family default . \layout Itemize Commands that should be run as root will have a '#' in front of them. \layout Itemize Commands that should be run as an unprivelged user will have a '$' in front of them. \layout Itemize Text that should be placed in a file \family typewriter is in monospace. \layout Standard All of the applications shipped with tcpreplay support both short (a single dash followed by a single character) and long (two dashes followed by multiple characters) arguments. For consistancy, this document uses the long option format. Please review the man pages for the short argument equivalents. \layout Subsection* Getting Help \layout Standard If you still have a question after reading the Tcpreplay manual, man pages and FAQ, please contact the Tcpreplay-Users mailing list. Note that if you ask a question which has clearly been covered in either the manual or FAQ, you will most likely be told to RTFM. Also, please try to explain your problem in detail. It is very difficult and fustrating to get requests from people seeking help who only provide vague and incomplete information. \layout Subsection* Corrections and additions to the manual \layout Standard I've tried to keep this document up to date with the changes in tcpreplay, but occasionally I get too busy, make a mistake or just forget something. If you find anything in this document which could be improved upon, please let me know. \layout Section* Getting Tcpreplay working on your system \layout Subsection* Getting the source code \layout Standard The source code is available as a tarball on the tcpreplay homepage: \begin_inset LatexCommand \htmlurl{http://tcpreplay.sourceforge.net/} \end_inset I also encourage users familiar with Subversion to try checking out the latest code as it often has additional features and bugfixes not yet found in the offical releases. \layout LyX-Code$ svn checkout https://www.synfin.net:444/svn/tcpreplay/trunk tcpreplay \layout Subsection* Requirements \layout Enumerate Libnet \begin_inset Foot collapsed true \layout Standard http://www.packetfactory.net/libnet/ \end_inset 1.1.x or better (1.1.3 fixes a checksum bug which effects tcprewrite) \layout Enumerate Libpcap \begin_inset Foot collapsed true \layout Standard http://www.tcpdump.org/ \end_inset 0.6.x or better (0.8.3 or better recommended) \layout Enumerate To support the packet decoding feature you'll need tcpdump \begin_inset Foot collapsed true \layout Standard http://www.tcpdump.org/ \end_inset binary installed. \layout Enumerate You'll also need a compatible operating system. Basically, any *NIX operating system should work. Linux, *BSD, Solaris, OS X and others should all work. If you find any compatibility issues with any *NIX OS, please let me know. \layout Subsection* Compiling Tcpreplay \layout Standard Two easy steps: \layout LyX-Code \emph on \emph default ./configure && make \emph on \layout LyX-Code \emph on # \emph default make install \layout Standard There are some optional arguments which can be passed to the 'configure' script which may help in cases where your libnet, libpcap or tcpdump installati on is not standard or if it can't determine the correct network interface card to use for testing. I also recommend that for beta code you specify \series bold -\SpecialChar \textcompwordmark{} -enable-debug \series default to the configure script in case you find any bugs. If you find that configure isn't completing correctly, run: \emph on ./configure -\SpecialChar \textcompwordmark{} -help \emph default for more information. \layout Standard You may also choose to run: \layout LyX-Code # \emph on make test -i \layout Itemize make test is just a series of sanity checks which try to find serious bugs (crashes) in tcpprep and tcpreplay. \layout Itemize make test requires at least one properly configured network interface. If the configure script can't guess what a valid interface is you can specify it with the -\SpecialChar \textcompwordmark{} -with-testnic and -\SpecialChar \textcompwordmark{} -with-testnic2 arguments. \layout Itemize If make test fails, often you can find details in test/test.log. \layout Itemize OpenBSD's make has a bug where it ignores the MAKEFLAGS variable in the Makefile, hence you'll probably want to run: \emph on make -is test \emph default instead. \layout Section* Basic Tcpreplay Usage \layout Subsection* Replaying the traffic \layout Standard To replay a given pcap as it was captured all you need to do is specify the pcap file and the interface to send the traffic out interface 'eth0': \layout LyX-Code # tcpreplay --intf1=eth0 sample.pcap \layout Subsection* Replaying at different speeds \layout Standard You can also replay the traffic at different speeds then it was originally captured \begin_inset Foot collapsed true \layout Standard Tcpreplay makes a "best" effort to replay traffic at the given rate, but due to limitations in hardware or the pcap file itself, it may not be possible. Capture files with only a few packets in them are especially susceptible to inaccurately timing packets. \end_inset . \layout Standard Some examples: \layout Itemize To replay traffic as quickly as possible: \layout LyX-Code # tcpreplay --topspeed --intf1=eth0 sample.pcap \layout Itemize To replay traffic at a rate of 10Mbps: \layout LyX-Code # tcpreplay --mbps=10.0 --intf1=eth0 sample.pcap \layout Itemize To replay traffic 7.3 times as fast as it was captured: \layout LyX-Code # tcpreplay --multiplier=7.3 --intf1=eth0 sample.pcap \layout Itemize To replay traffic at half-speed: \layout LyX-Code # tcpreplay --multiplier=0.5 --intf1=eth0 sample.pcap \layout Itemize To replay at 25 packets per second: \layout LyX-Code # tcpreplay --pps=25 --intf1=eth0 sample.pcap \layout Subsection* Replaying files multiple times \layout Standard Using the loop flag you can specify that a pcap file will be sent two or more times \begin_inset Foot collapsed true \layout Standard Looping files resets internal counters which control the speed that the file is replayed. Also because the file has to be closed and re-opened, an added delay between the last and first packet may occur. \end_inset : \layout Standard To replay the sample.pcap file 10 times: \layout LyX-Code # tcpreplay --loop=10 --intf1=eth0 sample.pcap \layout Standard To replay the sample.pcap an infinitely or until CTRL-C is pressed: \layout LyX-Code # tcpreplay --loop=0 --intf1=eth0 sample.pcap \layout Section* Editing Packets \layout Standard There are a number of ways you can edit packets stored in a pcap file: \layout Enumerate Rewriting IP addresses so that they appear to be sent from and to different hosts \layout Enumerate Fixing corrupted packets which were truncated by tcpdump or had bad checksums \layout Enumerate Adding, removing or changing 802.1q VLAN tags on frames \layout Enumerate Rewriting traffic so that it no longer uses \begin_inset Quotes eld \end_inset standard \begin_inset Quotes erd \end_inset TCP or UDP ports for the given service \layout Enumerate Changing ethernet MAC addresses so that packets will be accepted by a router or firewall \layout Section* Splitting Traffic \layout Standard Anything other then just replaying packets at different speeds requires additional work and CPU cycles. While older versions of tcpreplay allowed you to do many of these calculations while replaying traffic, it had a negative effect on the overall throughput and performance of tcpreplay. Hence, these secondary features have been placed in two utilities: \layout Itemize tcpprep - Used to categorize packets as originating from clients or servers \layout Itemize tcprewrite - Used to edit packets \layout Standard By using tcpprep and tcprewrite on a pcap file before sending it using tcpreplay , many possibilities open up. A few of these possibilities are: \layout Subsection* Classifying client and servers with tcpprep \layout Standard Both tcpreplay and tcprewrite process a single pcap file and generate output. Some features, such as rewriting IP or MAC addresses or sending traffic out two different interfaces, require tcpreplay and tcprewrite to have some basic knowledge about which packets were sent by \begin_inset Quotes eld \end_inset clients \begin_inset Quotes erd \end_inset and \begin_inset Quotes eld \end_inset servers \begin_inset Quotes erd \end_inset . Such classification is often rather arbitrary since for example a SMTP mail server both accepts inbound email (acts as a server) and forwards mail to other mail servers (acts as a client). A webserver might accept inbound HTTP requests, but make client connections to a SQL server. \layout Standard To deal with this problem, tcpreplay comes with tcpprep which provides a number of manual and automatic classification methods which cover a variety of situations. \layout Subsubsection* Seperating clients and servers automatically \layout Standard The easiest way to split clients and servers is to let tcpprep do the classifica tion for you. Tcpprep examines the pcap file for TCP three-way handshakes, DNS lookups and other types of traffic to figure out which IP's mostly act like clients and which mostly act like servers. There are four different automatic modes that you can choose between: \layout Enumerate Bridge - This is the simplest mode. Each IP is individually tracked and ranked as a client or server. However, if any of the hosts do not generate enough \begin_inset Quotes eld \end_inset client \begin_inset Quotes erd \end_inset or \begin_inset Quotes eld \end_inset server \begin_inset Quotes erd \end_inset traffic then tcpprep will abort complaining that it was unable to determine its classification. This works best when clients and servers are intermixed on the same subnet. \layout Enumerate Client - This works just like bridge mode, except that unknown hosts will be marked a client. \layout Enumerate Server - This works just like bridge mode, except that unknown hosts will be marked a server. \layout Enumerate Router - Hosts are first ranked as client or server. Then each host is placed in a subnet which is expanded until either all the unknown hosts are included or the --maxmask is reached. This works best when clients and servers are on diffierent networks. \layout Standard \align center \noun on \begin_inset Tabular \begin_inset Text \layout Standard TCPPREP AUTOMATIC ROUTER MODE PROCESS \end_inset \begin_inset Text \layout Standard \end_inset \begin_inset Text \layout Standard \noun on Step 1: \noun default Categorize Clients, Servers and Unknowns \end_inset \begin_inset Text \layout Standard \noun on Step 2: \noun default Clients and Servers Expand Their Subnets to Include Unknowns \end_inset \begin_inset Text \layout Standard \begin_inset Graphics filename router-mode1.eps lyxscale 60 scale 60 keepAspectRatio \end_inset \end_inset \begin_inset Text \layout Standard \begin_inset Graphics filename router-mode2.eps lyxscale 60 scale 60 keepAspectRatio \end_inset \end_inset \end_inset \layout Standard \SpecialChar ~ \SpecialChar ~ \SpecialChar ~ \layout Standard \align center \begin_inset Tabular \begin_inset Text \layout Standard \noun on Step 3: \noun default Unknowns Now Marked as Clients and Servers \end_inset \begin_inset Text \layout Standard \noun on \begin_inset Graphics filename router-mode3.eps lyxscale 60 scale 60 keepAspectRatio \end_inset \end_inset \end_inset \layout Standard Classifying clients and servers in automatic mode is as easy as choosing a pcap file, an output \begin_inset Quotes eld \end_inset tcpprep cache file \begin_inset Quotes erd \end_inset and the mode to use: \layout LyX-Code \emph on \emph default tcpprep --auto=bridge --pcap=input.pcap --cachefile=input.cache \layout Standard The above example would split traffic in bridge mode. Other modes are \begin_inset Quotes eld \end_inset router \begin_inset Quotes erd \end_inset , \begin_inset Quotes eld \end_inset client \begin_inset Quotes erd \end_inset and \begin_inset Quotes eld \end_inset server \begin_inset Quotes erd \end_inset . If you wish, you can override the default 2:1 ratio of server vs. client traffic required to classify an IP as a server. If for example you wanted to require 3.5 times as much server to client traffic you would specify it like: \layout LyX-Code \emph on \$ \emph default tcpprep --auto=bridge --ratio=3.5 --pcap=input.pcap --cachefile=input.cache \layout Subsubsection* Seperating clients and servers manually by subnet \layout Standard Sometimes, you may not want to split traffic based on clients and servers. The alternative to using on of the automatic modes in this case, is to use one of the manual modes. One manual way of differentiating between clients and servers using tcpprep is by specifying a list of networks in CIDR notation which contain \begin_inset Quotes eld \end_inset servers \begin_inset Quotes erd \end_inset . Of course the specified CIDR netblocks don't have to contain \layout Subsection* Replaying on multiple interfaces \layout Standard Tcpreplay can also split traffic so that each side of a connection is sent out a different interface \begin_inset Foot collapsed true \layout Standard Note that you can also use the following options to split traffic into two files using -w and -W which are described later on in this FAQ. \end_inset . In order to do this, tcpreplay needs the name of the second interface (-j) and a way to split the traffic. Currently, there are two ways to split traffic: \layout Enumerate -C = split traffic by source IP address which is specified in CIDR notation \layout Enumerate -c = split traffic according to a tcpprep cachefile \begin_inset Foot collapsed true \layout Standard For information on generating tcpprep cache files, see the section on tcpprep. \end_inset \layout Standard When splitting traffic, it is important to remember that traffic that matches the filter is sent out the primary interface (--intf1). In this case, when splitting traffic by source IP address, you provide a list of networks in CIDR notation. For example: \layout Itemize To send traffic from 10.0.0.0/8 out eth0 and everything else out eth1: \layout LyX-Code tcpreplay -C 10.0.0.0/8 --intf1=eth0 --intf2=eth1 sample.pcap \layout Itemize To send traffic from 10.1.0.0/24 and 10.2.0.0/20 out eth0 and everything else out eth1: \layout LyX-Code tcpreplay -C 10.1.0.0/24,10.2.0.0/20 --intf1=eth0 --intf2=eth1 sample.pcap \layout Itemize After using tcpprep to generate a cache file, you can use it to split traffic between two interfaces like this: \layout LyX-Code tcpreplay -c sample.cache --intf1=eth0 --intf2=eth1 sample.pcap \layout Subsection* Selectively sending or dropping packets \layout Standard Sometimes, you want to do some post-capture filtering of packets. Tcpreplay let's you have some control over which packets get sent. \layout Enumerate -M = disables sending of martian packets. By definition, martian packets have a source IP of 0.x.x.x, 127.x.x.x, or 255.x.x.x \layout Enumerate -x = send packets which match a specific pattern \layout Enumerate -X = send packets which do not match a specific pattern \layout Standard Both -x and -X support a variety of pattern matching types. These types are specified by a single character, followed by a colon, followed by the pattern. The following pattern matching types are available: \layout Enumerate S - Source IP \newline Pattern is a comma delimited CIDR notation \layout Enumerate D - Destination IP \newline Pattern is a comma delimited CIDR notation \layout Enumerate B - Both source and destination IP must match \newline Pattern is a comma delimited CIDR notation \layout Enumerate E - Either source or destination IP must match \newline Pattern is a comma delimited CIDR notation \layout Enumerate P - A list of packet numbers from the pcap file. \newline Pattern is a series of numbers, separated by commas or dashes. \layout Enumerate F - BPF syntax (same as used in tcpdump). \newline Filter must be quoted and is only supported with -x \begin_inset Foot collapsed true \layout Standard Note that if you want to send all the packets which do not match a bpf filter, all you have to do is negate the bpf filter. See the tcpdump(1) man page for more info. \end_inset . \layout Standard Examples: \layout Itemize To only send traffic that is too and from a host in 10.0.0.0/8: \layout LyX-Code tcpreplay -x B:10.0.0.0/8 --intf1 eth0 sample.pcap \layout Itemize To not send traffic that is too or from a host in 10.0.0.0/8: \layout LyX-Code tcpreplay -X E:10.0.0.0/8 --intf1 eth0 sample.pcap \layout Itemize To send every packet except the first 10 packets: \layout LyX-Code tcpreplay -X P:1-10 --intf1 eth0 sample.pcap \layout Itemize To only send the first 50 packets followed by packets: 100, 150, 200 and 250: \layout LyX-Code tcpreplay -x P:1-50,100,150,200,250 --intf1 eth0 sample.pcap \layout Itemize To only send TCP packets from 10.0.0.1: \layout LyX-Code \emph on tcpreplay -x F:'tcp and host 10.0.0.1' --intf1 eth0 sample.pcap \layout Subsection* Replaying only a few packets \layout Standard Using the limit packets flag (-L) you can specify that tcpreplay will only send at most a specified number of packets. \layout Itemize To send at most 100 packets: \layout LyX-Code tcpreplay --intf1 eth0 -L 100 sample.pcap \layout Subsection* Skipping the first bytes in a pcap file \layout Standard If you want to skip the beginning of a pcap file, you can use the offset flag (-o) to skip a specified number of bytes and start sending on the next packet. \layout Itemize To skip 15Kb into the pcap file and start sending packets from there: \layout LyX-Code tcpreplay --intf1=eth0 -o 15000 sample.pcap \layout Subsection* Replaying packets which are bigger then the MTU \layout Standard Occasionally, you might find yourself trying to replay a pcap file which contains packets which are larger then the MTU for the sending interface. This might be due to the packets being captured on the loopback interface or on a 1000Mbps ethernet interface supporting \begin_inset Quotes eld \end_inset jumbo frames \begin_inset Quotes erd \end_inset . I've even seen packets which are 1500 bytes but contain both an ethernet header and trailer which bumps the total frame size to 1518 which is 4 bytes too large. \layout Standard By default, tcpreplay will skip these packets and not send them. Alternatively, you can specify the -T flag to truncate these packets to the MTU and then send them. Of course this may invalidate your testing, but it has proven useful in certain situations. Also, when this feature is enabled, tcpreplay will automatically recalculate the IP and TCP, UDP or ICMP checksums as needed. Example: \layout LyX-Code tcpreplay --intf1 eth0 -T sample.pcap \layout Subsection* Writing packets to a file \layout Standard It's not always necessary to write packets to the network. Since tcpreplay has so many features which modify and select which packets are sent, it is occasionally useful to save these changes to another pcap file for comparison. Rather then running a separate tcpdump process to capture the packets, tcpreplay now supports output directly to a file. Example: \layout LyX-Code tcpreplay --intf1 eth0 -w output.pcap -F -u pad -x E:10.0.0.0/8 input1.pcap input2.pca p input3.pcap \layout Standard Notice that specifying an interface is still required (required for various internal functions), but all the packets will be written to \emph on output.pcap \emph default . \layout Standard You can also split traffic into two files by using -W <2nd output file>. \layout Subsection* Extracting Application Data (Layer 7) \layout Standard New to version 2.0 is the ability to extract the application layer data from the packets and write them to a file. In the man page, we call this \begin_inset Quotes eld \end_inset data dump mode \begin_inset Quotes erd \end_inset which is enabled with -D. It's important to specify -D before -w (and -W if you're splitting data into two files). Example: \layout LyX-Code tcpreplay -D --intf1 eth0 -j eth0 -w clientdata -W serverdata -C 10.0.0.0/24 sample.pcap \layout Subsection* Replaying Live Traffic \layout Standard You can now replay live traffic sniffed on one network interface and replay it on another interface using the -S flag to indicate sniff mode and the appropriate snaplen in bytes (0 denotes the entire packet). You can also enabling bi-directional traffic using the bridge mode flag: -b. \layout Standard N \noun on ote: \noun default It is critical for your sanity (and to prevent your murder by your network administrators) that the input interface and the output interface be on separate networks and additionally that no other network devices (such as bridges, switches, routers, etc) be connecting the two networks, else you will surely get a networkstorm the likes that have not been seen for years. \layout Itemize Send packets sniffed on eth0 out eth1: \layout LyX-Code tcpreplay --intf1 eth1 -S 0 eth0 \layout Itemize Bridge two subnets connected to eth0 and eth1: \layout LyX-Code tcpreplay --intf1 eth0 --intf2=eth1 -b -S 0 \layout Standard By default, tcpreplay listens in promiscuous mode on the specified interface, however if you only want to send unicasts directed for the local system and broadcasts, you can specify the \begin_inset Quotes eld \end_inset not_nosy \begin_inset Quotes erd \end_inset option in the configuration file or -n on the command line. Note that if another program has already placed the interface in promiscuous mode, the -n flag will have no effect, so you may want to use the -x or -X argument to limit packets. \layout Subsection* Replaying Packet Capture Formats Other Than Libpcap \layout Standard There are about as many different capture file formats as there are sniffers. In the interest of simplicity, tcpreplay only supports libpcap \begin_inset Foot collapsed true \layout Standard Note that some versions of tcpreplay prior to 1.4 also supported the Solaris snoop format. \end_inset . If you would like to replay a file in one of these multitude of formats, the excellent open source tool Ethereal easily allows you to convert it to libpcap. For instance, to convert a file in Sun's snoop format to libpcap, issue the command: \layout LyX-Code tethereal -r blah.snoop -w blah.pcap \layout Standard and replay the resulting file. \layout Subsection* Replaying Client Traffic to a Server \layout Standard A common question on the tcpreplay-users list is how does one replay the client side of a connection back to a server. Unfortunately, tcpreplay doesn't support this right now. The major problem concerns syncing up TCP Seq/Ack numbers which will be different. ICMP also often contains IP header information which would need to be adjusted. About the only thing that could be easy to do is UDP, which isn't usually requested. \layout Standard This is however a feature that we're looking into implementing in the flowreplay utility. If you're interested in helping work on this feature, please contact us and we'd be more then happy to work with you. At this time however, we don't have an ETA when this will be implemented, so don't bother asking. \layout Subsection* Decoding Packets \layout Standard If the tcpdump binary is installed on your system when tcpreplay is compiled, it will allow you to decode packets as they are sent without running tcpdump in a separate window or worrying about it capturing packets which weren't sent by tcpreplay. \layout Itemize Decode packets as they are sent: \layout LyX-Code tcpreplay --intf1 eth0 -v sample.pcap \layout Itemize Decode packets with the link level header: \layout LyX-Code tcpreplay --intf1 eth0 -v -A \begin_inset Quotes eld \end_inset -e \begin_inset Quotes erd \end_inset sample.pcap \layout Itemize Fully decode and send one packet at a time: \layout LyX-Code tcpreplay --intf1 eth0 -v -1 -A \begin_inset Quotes eld \end_inset -s0 -evvvxX \begin_inset Quotes erd \end_inset sample.pcap \layout Standard Note that tcpreplay automatically applies the -n flag to disable DNS lookups which would slow down tcpdump too much to make it effective. \layout Section* Packet Editing \layout Subsection* Rewriting MAC addresses \layout Standard If you ever want to send traffic to another device on a switched LAN, you may need to change the destination MAC address of the packets. Tcpreplay allows you to set the destination MAC for each interface independentl y using the -I and -J switches. As of version 2.1.0, you can also specify the source MAC via -k and -K. Example: \layout Itemize To send traffic out eth0 with a destination MAC of your router (00:00:01:02:03:0 4) and the source MAC of the server (00:20:30:40:50:60): \layout LyX-Code tcpreplay --intf1=eth0 -I 00:00:01:02:03:04 -k 00:20:30:40:50:60 sample.pcap \layout Itemize To split traffic between internal (10.0.0.0/24) and external addresses and to send that traffic to the two interfaces of a firewall: \layout LyX-Code tcpreplay --intf1=eth0 --intf2=eth1 -I 00:01:00:00:AA:01 -J 00:01:00:00:AA:02 -C 10.0.0.0/24 sample.pcap \layout Subsection* Randomizing IP addresses \layout Standard Occasionally, it is necessary to have tcpreplay rewrite the source and destinati on IP addresses, yet maintain the client/server relationship. Such a case might be having multiple copies of tcpreplay running at the same time using the same pcap file while trying to stress test firewall, IDS or other stateful device. If you didn't change the source and destination IP addresses, the device under test would get confused since it would see multiple copies of the same connection occurring at the same time. In order to accomplish this, tcpreplay accepts a user specified seed which is used to generate pseudo-random IP addresses. Also, when this feature is enabled, tcpreplay will automatically recalculate the IP and TCP, UDP or ICMP checksums as needed. Example: \layout LyX-Code \emph on tcpreplay --intf1=eth0 -s 1239 sample.pcap & \newline tcpreplay --intf1=eth0 -s 76 sample.pcap & \newline tcpreplay --intf1=eth0 -s 239 sample.pcap & \newline tcpreplay --intf1=eth0 sample.pcap \layout Subsection* Replaying (de)truncated packets \layout Standard Occasionally, it is necessary to replay traffic which has been truncated by tcpdump. This occurs when the tcpdump snaplen is smaller then the actual packet size. Since this will create problems for devices which are expecting a full-sized packet or attempting checksum calculations, tcpreplay allows you to either pad the packet with zeros or reset the packet length in the headers to the actual packet size. In either case, the IP and TCP, UDP or ICMP checksums are recalculated. Examples: \layout Itemize Pad truncated packets: \layout LyX-Code tcpreplay --intf1=eth0 -u pad sample.pcap \layout Itemize Rewrite packet header lengths to the actual packet size: \layout LyX-Code tcpreplay --intf1=eth0 -u trunc sample.pcap \layout Subsection* Rewriting Layer 2 with -2 \layout Standard Starting in the 2.0.x branch, tcpreplay can replace the existing layer 2 header with one of your choosing. This is useful for when you want to change the layer 2 header type or add a header for pcap files without one. Each pcap file tells the type of frame. Currently tcpreplay knows how to deal with the following pcap(3) frame types: \layout Itemize DLT_EN10MB \newline Replace existing 802.3/Ethernet II header \layout Itemize DLT_RAW \newline Frame has no Layer 2 header, so we can add one. \layout Itemize DLT_LINUX_SLL \newline Frame uses the Linux Cooked Socket header which is most commonly created with \emph on tcpdump -i any \emph default on a Linux system. \layout Standard Tcpreplay accepts the new Layer 2 header as a string of comma separated hex values such as: 0xff,0xac,0x00,0x01,0xc0,0x64. Note that the leading '0x' is \emph on not \emph default required. \layout Standard Potential uses for this are to add a layer 2 header for DLT_RAW captures or add/remove ethernet tags or QoS features. \layout Subsection* Rewriting DLT_LINUX_SLL (Linux Cooked Socket) captures \layout Standard Tcpdump uses a special frame type to store captures created with the \begin_inset Quotes eld \end_inset -i any \begin_inset Quotes erd \end_inset argument. This frame type uses a custom 16 byte layer 2 header which tracks which interface captured the packet and often the source MAC address of the original ethernet frame. Unfortunately, it never stores the destination MAC address and it doesn't store a source MAC when the packet is captured on the loopback interface. Normally, tcpreplay can't replay these pcap files because there isn't enough information in the LINUX_SLL header to do so; however two options do exist: \layout Enumerate You can send these packets with -2 which will replace the LINUX_SLL header with an ethernet header of your choosing. \layout Enumerate You can specify a destination MAC via -I and -J in which case tcpreplay will use the stored source MAC and create a new 802.3 Ethernet header. Note that if the pcap contains loopback packets, you will also need to specify -k and/or -K to specify the source MAC as well or they will be skipped. \layout Subsection* Rewriting IP Addresses (pseudo-NAT) \layout Standard Pseudo-NAT allows the mapping of IP addresses in IPv4 and ARP packets from one subnet to another subnet of the same or different size. This allows some or all the traffic sent to appear to come from a different IP subnet then it actually was captured on. \layout Standard The mapping is done through a user specified translation table comprised of one or more source and destination network(s) in the format of /:/ deliminated by a comma. Mapping is done by matching IP addresses to the source subnet and rewriting the most significant bits with the destination subnet. For example: \layout Standard \emph on tcpreplay --intf1=eth0 -N 10.100.0.0/16:172.16.10.0/24 sample.pcap \layout Standard would match any IP in the 10.100.0.0/16 subnet and rewrite it as if it came from or sent to the 172.16.10.0/24 subnet. Ie: 10.100.5.88 would become 172.16.10.88 and 10.100.99.45 would become 172.16.10.45. But 10.150.7.44 would not be rewritten. \layout Standard For any given IP address, the translation table is applied in order (so if there are multiple mappings, earlier maps take precedence) and occurs only once per IP (no risk of an address getting rewritten a second time). \layout Subsection* Advanced pseudo-NAT \layout Standard Pseudo-NAT also works with traffic splitting (using two interfaces or output files) but with a few important differences. First you have the option of specifying one or two pseudo-NAT tables. Using a single pseudo-NAT table means that the source and destination IP addresses of both interfaces are rewritten using the same rules. Using two pseudo-NAT tables (specifying -N -N ) will cause the source and destination IP addresses to be rewritten differently for each interface using the following matrix: \layout Standard \align center \begin_inset Tabular \begin_inset Text \layout Standard \end_inset \begin_inset Text \layout Standard Out Primary Interface \end_inset \begin_inset Text \layout Standard Out Secondary Interface \end_inset \begin_inset Text \layout Standard Src IP \end_inset \begin_inset Text \layout Standard Table 1 \end_inset \begin_inset Text \layout Standard Table 2 \end_inset \begin_inset Text \layout Standard Dest IP \end_inset \begin_inset Text \layout Standard Table 2 \end_inset \begin_inset Text \layout Standard Table 1 \end_inset \end_inset \layout Standard While seemingly a bit confusing, this feature provides a number of interesting possibilities such as the ability to rewrite the IP headers of packets in the case where traffic is captured on the loopback interface (and the source and destination address is always 127.0.0.1) so that tcpreplay can make it look like two different systems are talking to each other (you'll probably also need to specify the source and destination MAC addresses via -I, -J, -k and -K). \layout Subsection* IP Endpoints \layout Standard While pseudo-NAT provides a great deal of flexibility, it is often more complicated then is necessary for testing of inline devices. As a simplier alternative, tcpreplay supports the concept of rewriting all traffic to so that it appears to be between two IP addresses: \layout LyX-Code tcpreplay --intf1=eth0 --intf2=eth1 -c sample.cache -e 10.0.0.1:10.1.1.1 sample.pcap \layout Standard Will rewrite all the traffic so that it is between 10.0.0.1 and 10.1.1.1. The equivalent command using -N would be: \layout LyX-Code tcpreplay --intf1=eth0 --intf2=eth1 -c sample.cache -N 0.0.0.0/0:10.0.0.1 -N 0.0.0.0/0:10.1. 1.1 sample.pcap \layout Subsection* Unifying Dual-Outputs \layout Standard Since a number of tcpreplay's packet editing functions require splitting traffic between client and servers, one problem that may arrise is needing to edit packets but still output to a single interface or file. The solution to this is to use the one output option -O which causes packets to be processed as if they will be split between the interfaces/files, but then always go out the primary interface or file. Note that even though only one interface/file will be written to, both -i and -j must be specified; although they can be the same physical interface. \layout LyX-Code tcpreplay --intf1=eth0 -j eth0 -O -c sample.cache -e 10.0.0.1:10.1.1.1 sample.pcap \layout Standard Merging the output to a single file: \layout LyX-Code tcpreplay --intf1=eth0 -j eth0 -w rewrite.pcap -c sample.cache -e 10.0.0.1:10.1.1.1 sample.pcap \layout Section* Tcpprep Usage \layout Subsection* What is tcpprep? \layout Standard Tcpreplay can send traffic out two network cards, however it requires the calculations be done in real-time. These calculations can be expensive and can significantly reduce the throughput of tcpreplay. \layout Standard Tcpprep is a libpcap pre-processor for tcpreplay which enables using two network cards to send traffic without the performance hit of doing the calculations in real-time. \layout Subsection* What are these 'modes' tcpprep has? \layout Standard Tcpprep has three basic modes which require the user to specify how to split traffic. \layout Itemize CIDR (-\SpecialChar \textcompwordmark{} -cidr) mode requires the user to provide a list of networks. Any packet with a source IP in one of these networks gets sent out the primary interface. \layout Itemize Regex (-\SpecialChar \textcompwordmark{} -regex) mode requires the user to provide a regular expression. Any packet with a source IP matching the regex gets sent out the primary interface. \layout Itemize Port (-\SpecialChar \textcompwordmark{} -port) mode splits TCP/UDP traffic based on the destination port in the header. Normally, ports 0-1023 are considered \begin_inset Quotes eld \end_inset server \begin_inset Quotes erd \end_inset ports and everything else a client port. You can create your own custom mapping file in the same format as /etc/services (see the services(5) man page for details) by specifying -\SpecialChar \textcompwordmark{} -services . \layout Standard And four auto modes in which tcpprep decides how to split traffic. Auto modes are useful for when you don't know much about the contents of the dump file in question and you want to split traffic up based upon servers and clients. \layout Itemize Auto/Router (-\SpecialChar \textcompwordmark{} -auto router) mode trys to find the largest network(s) that contain all the servers and no clients. Any unknown system is automatically re-classified as servers if it's inside the server network(s), otherwise it is classified as a client. \layout Itemize Auto/Bridge (-\SpecialChar \textcompwordmark{} -auto bridge) mode makes the assumption that the clients and servers are horribly intermixed on the network and there's no way to subnet them. While this takes less processing time to create the cache file it is unable to deal with unknown systems. \layout Itemize Auto/Client (-\SpecialChar \textcompwordmark{} -auto client) mode which works just like Auto/Bridge mode, except that any system it can't figure out is treated like a client. \layout Itemize Auto/Server (-\SpecialChar \textcompwordmark{} -auto server) mode which works just like Auto/Bridge mode, except that any system it can't figure out is treated like a server. \layout Subsection* Splitting traffic based upon IP address \layout Standard Tcpprep supports the same CIDR mode that tcpreplay supports using the -\SpecialChar \textcompwordmark{} -cidr flag. Additionally, tcpprep also supports regex(7) regular expressions to match source IP addresses using the -\SpecialChar \textcompwordmark{} -regex flag. \layout Subsection* Auto Mode \layout Subsubsection* How does Auto/Bridge mode work? \layout Standard Tcpprep does an initial pass over the libpcap file to build a binary tree (one node per IP). For each IP, it keeps track of how many times it was a client or server. It then does a second pass of the file using the data in the tree and the ratio to determine if an IP is a client or server. If tcpprep is unable to determine the type (client or server) for each and every packet, then auto/bridge mode will fail. In these cases, it is best to use a different auto mode. \layout Subsubsection* How does Auto/Router mode work? \layout Standard Tcpprep does the same first pass as Auto/Bridge mode. It then trys to convert the binary tree into a list of networks containing the servers. Finally it uses the CIDR mode with the list of server networks in a second pass of the libpcap file. Unlike auto/bridge mode, auto/router mode can always successfully split IP addresses into clients and servers. \layout Subsubsection* Determining Clients and Servers \layout Standard Tcpprep uses the following methods in auto/router and auto/bridge mode to determine if an IP address is a client or server: \layout Itemize Client: \begin_deeper \layout Itemize TCP with Syn flag set \layout Itemize UDP source/destination port 53 (DNS) without query flag set \layout Itemize ICMP port unreachable (destination IP of packet) \end_deeper \layout Itemize Server: \begin_deeper \layout Itemize TCP with Syn/Ack flag set \layout Itemize UDP source/destination port 53 (DNS) with query flag set \layout Itemize ICMP port unreachable (source IP of packet) \end_deeper \layout Subsubsection* Client/Server ratio \layout Standard Since a system may send traffic which would classify it as both a client and server, it's necessary to be able to weigh the traffic. This is done by specifying the client/server ratio (-R) which is by default set to 2.0. The ratio is the modifier to the number of client connections. Hence, by default, client connections are valued twice as high as server connections. \layout Subsection* Selectively sending/dropping packets \layout Standard Tcpprep supports the same -\SpecialChar \textcompwordmark{} -include and -\SpecialChar \textcompwordmark{} -exclude options to selectively send or drop packets. \layout Subsection* Using tcpprep cache files with tcpreplay \layout Standard Just run: \layout LyX-Code tcpreplay --cachefile sample.cache --intf1=eth0 --intf2=eth1 sample.pcap \layout Subsection* Commenting tcpprep cache files \layout Standard In versions of tcpprep >= 2.1.0, you can specify a comment to be embeded in the tcpprep cache file. Comments are user specified and automatically include the command line arguments passed to tcpprep. \layout LyX-Code tcpprep --comment \begin_inset Quotes eld \end_inset this is my comment \begin_inset Quotes erd \end_inset --pcap sample.pcap --cachefile sample.cache \layout Standard Or for no user comment, but still embed the command arguments: \layout LyX-Code tcpprep --comment \begin_inset Quotes eld \end_inset \begin_inset Quotes erd \end_inset --pcap sample.pcap --cachefile sample.cache \layout Standard You can then later on print out the comments by running: \layout LyX-Code tcpprep --print-comment sample.cache \layout Section* Using Configuration Files \layout Standard Each of the applications in the tcpreplay suite offers the choice of specifying configuration options in a config file in addition to the traditional command line. Each command line option has an equivalent config file option which is listed in the man page. To specify the configuration file you'd like to use, use the -\SpecialChar \textcompwordmark{} -load-opts= option. \layout Standard Configuration files have one option per line, and lines beginning with the pound sign (#) are considered comments and ignored. An example config file follows: \layout Standard ------------BEGIN CONFIG FILE-------------- \layout Standard \family typewriter # send traffic out 'eth0' \newline intf1 eth0 \newline \newline # loop 5 times \newline loop 5 \newline \newline # send traffic 2x as fast \newline multiplier 2 \family default \newline --------------END CONFIG FILE--------------- \layout Standard You would then execute: \layout LyX-Code # tcpreplay --load-opts=myconfigfile sample.pcap \layout Standard You can also group configuration options for tcpprep, tcprewrite and tcpreplay in a single config file by placing section markers in the config file. An example: \layout Standard ------------BEGIN CONFIG FILE-------------- \layout Standard \family typewriter cachefile=example.tcpprep \newline \newline [TCPREPLAY] \newline intf1 eth0 \newline intf2 eth1 \newline topspeed \newline \newline [TCPPREP] \newline auto=bridge \newline comment='This cache file was created with a config file' \newline pcap=sample.pcap \newline \newline [TCPREWRITE] \newline infile=sample.pcap \newline outfile=newsample.pcap \newline vlan=add \newline vlan-tag=44 \newline endpoints=10.0.0.1:10.0.1.1 \layout Standard ------------END CONFIG FILE-------------- \layout Section* Flowreplay Usage \layout Standard While tcpreplay is a great way to test NIDS and firewalls, it can't be used to test servers or HIDS since tcpreplay can't connect to a service running on a device. The solution to this problem is flowreplay which instead of sending packets at Layer 2 (ethernet header and up), it can actually connect via TCP or UDP to server and then sends and receives data based upon a pcap capture file created with a tool like Ethereal or tcpdump. \layout Standard Please note that flowreplay is currently alpha quality and is missing a number of key features. \layout Subsection* How flowreplay works \layout Standard Put simply, flowreplay opens a socket connection to a service on a target system(s) and sends data over that socket based on the packet capture. Flowreplay has no understanding of the application protocol (like HTTP or FTP) so it is somewhat limited in how it can deal with complicated exchanges between client and server. \layout Standard Some of these limitations are: \layout Itemize Flowreplay only plays the client side \begin_inset Foot collapsed false \layout Standard Flowreplay assumes the first UDP packet on a given 4-tuple is the client \end_inset of the connection. \layout Itemize Flowreplay doesn't understand the application protocols. Hence it can't always deal with the case when the server sends a different response then what was originally captured in the pcap file. \layout Itemize Flowreplay only sends TCP and UDP traffic. \layout Itemize Flowreplay doesn't know about multi-flow protocols like FTP. \layout Itemize Flowreplay can't listen on a port and wait for a client to connect to it. \layout Subsection* Running flowreplay \layout Standard See the flowreplay(8) man page for details. \layout Section* Tuning OS's for high performance \layout Standard Regardless of the size of physical memory, UNIX kernels will only allocate a static amount for network buffers. This includes packets sent via the "raw" interface, like with tcpreplay. Most kernels will allow you to tweak the size of these buffers, drastically increasing performance and accuracy. \layout Standard N \noun on ote: \noun default The following information is provided based upon our own experiences or the reported experiences of others. Depending on your hardware and specific hardware, it may or may not work for you. It may even make your system horribly unstable, corrupt your harddrive, or worse. \layout Standard \noun on Note \noun default : Different operating systems, network card drivers, and even hardware can have an effect on the accuracy of packet timestamps that tcpdump or other capture utilities generate. And as you know: garbage in, garbage out. \layout Standard \noun on Note: \noun default If you have information on tuning the kernel of an operating system not listed here, please send it to me so I can include it. \layout Subsection* Linux 2.4.x \layout Standard The following is known to apply to the 2.4.x series of kernels. If anyone has any information regarding other kernel versions, please let us know. By default Linux's tcpreplay performance isn't all that stellar. However, with a simple tweak, relatively decent performance can be had on the right hardware. By default, Linux specifies a 64K buffer for sending packets. Increasing this buffer to about half a megabyte does a good job: \layout Standard \emph on echo 524287 >/proc/sys/net/core/wmem_default \newline echo 524287 >/proc/sys/net/core/wmem_max \newline echo 524287 >/proc/sys/net/core/rmem_max \newline echo 524287 >/proc/sys/net/core/rmem_default \layout Standard On one system, we've seen a jump from 23.02 megabits/sec (5560 packets/sec) to 220.30 megabits/sec (53212 packets/sec) which is nearly a 10x increase in performance. Depending on your system and capture file, different numbers may provide different results. \layout Subsection* *BSD \layout Standard *BSD systems typically allow you to specify the size of network buffers with the NMBCLUSTERS option in the kernel config file. Experiment with different sizes to see which yields the best performance. See the options(4) man page for more details. \layout Section* Required Libraries and Tools \layout Subsection* Libpcap \layout Standard As of tcpreplay v1.4, you'll need to have libpcap installed on your system. As of v2.0, you'll need at least version 0.6.0 or better, but I only test our code with the latest version. Libpcap can be obtained on the tcpdump homepage \begin_inset Foot collapsed true \layout Standard \begin_inset LatexCommand \htmlurl{http://www.tcpdump.org/} \end_inset \end_inset . \layout Subsection* Libnet \layout Standard Tcpreplay v1.3 is the last version to support the old libnet API (everything before 1.1.x). As of v1.4 you will need to use Libnet 1.1.0 or better which can be obtained from the Libnet homepage \begin_inset Foot collapsed true \layout Standard \begin_inset LatexCommand \htmlurl{http://www.packetfactory.net/Projects/Libnet/} \end_inset \end_inset . \layout Subsection* Tcpdump \layout Standard As of 2.0, tcpreplay uses tcpdump (the binary, not code) to decode packets to STDOUT in a human readable (with practice) format as it sends them. If you would like this feature, tcpdump must be installed on your system. \layout Standard \noun on Note: \noun default The location of the tcpdump binary is hardcoded in tcpreplay at compile time. If tcpdump gets renamed or moved, the feature will become disabled. \layout Part* Other Resources \layout Section* Other pcap tools available \layout Subsection* Tools to capture network traffic or decode pcap files \layout Itemize tcpdump \newline \begin_inset LatexCommand \htmlurl{http://www.tcpdump.org/} \end_inset \layout Itemize ethereal \newline \begin_inset LatexCommand \htmlurl{http://www.ethereal.com/} \end_inset \layout Itemize ettercap \newline \begin_inset LatexCommand \htmlurl{http://ettercap.sourceforge.net/} \end_inset \layout Subsection* Tools to edit pcap files \layout Itemize tcpslice \newline Splits pcap files into smaller files \newline \begin_inset LatexCommand \htmlurl{http://www.tcpdump.org/} \end_inset \layout Itemize mergecap \newline Merges two pcap capture files into one \newline \begin_inset LatexCommand \htmlurl{http://www.ethereal.com/} \end_inset \layout Itemize editcap \newline Converts capture file formats (pcap, snoop, etc) \newline \begin_inset LatexCommand \htmlurl{http://www.ethereal.com/} \end_inset \layout Itemize netdude \newline GTK based pcap capture file editor. Allows editing most anything in the packet. \newline \begin_inset LatexCommand \htmlurl{http://netdude.sourceforge.net/} \end_inset \layout Subsection* Other useful tools \layout Itemize capinfo \newline Prints statistics and basic information about a pcap file \newline \begin_inset LatexCommand \htmlurl{http://www.ethereal.com/} \end_inset \layout Itemize text2pcap \newline Generates a pcap capture file from a hex dump \newline \begin_inset LatexCommand \htmlurl{http://www.ethereal.com/} \end_inset \layout Itemize tcpflow \newline Extracts and reassembles the data portion on a per-flow basis on live traffic or pcap capture files \newline \begin_inset LatexCommand \htmlurl{http://www.circlemud.org/~jelson/software/tcpflow/} \end_inset \the_end