tcprewrite(1)

Rewrite the packets in a pcap file.

Section 1 tcpreplay bookworm source

Description

tcprewrite

NAME

tcprewrite - Rewrite the packets in a pcap file.

SYNOPSIS

tcprewrite [-flags] [-flag [value]] [--option-name[[=| ]value]]

All arguments must be options.

DESCRIPTION

Tcprewrite is a tool to rewrite packets stored in pcap(3) file format, such as created by tools such as tcpdump(1) and wireshark(1). Once a pcap file has had it’s packets rewritten, they can be replayed back out on the network using tcpreplay(1).

tcprewrite currently supports reading the following DLT types:

DLT_C_HDLC aka Cisco HDLC

DLT_EN10MB aka Ethernet

DLT_LINUX_SLL aka Linux Cooked Socket

DLT_RAW aka RAW IP

DLT_NULL aka BSD Loopback

DLT_LOOP aka OpenBSD Loopback

DLT_IEEE802_11 aka 802.11a/b/g

DLT_IEEE802_11_RADIO aka 802.11a/b/g with Radiotap headers

DLT_JUNIPER_ETHER aka Juniper Encapsulated Ethernet

DLT_PPP_SERIAL aka PPP over Serial

Please see the --dlt option for supported DLT types for writing.

The packet editing features of tcprewrite which distinguish between "client" and "server" traffic requires a tcpprep(1) cache file.

For more details, please see the Tcpreplay Manual at: http://tcpreplay.appneta.com

OPTIONS

-r string, --portmap=string Rewrite TCP/UDP ports. This option may appearup to 9999 times.Specify a list of comma delimited port mappings consisting of colondelimited port number pairs. Each colon delimited port pair consists ofthe port to match followed by the port number to rewrite.Examples:--portmap=80:8000 --portmap=8080:80 # 80->8000 and 8080->80--portmap=8000,8080,88888:80 # 3 different ports become 80--portmap=8000-8999:80 # ports 8000 to 8999 become 80-s number, --seed=number Randomize src/dst IPv4/v6 addresses w/ given seed.This option may appear up to 1 times. This option must not appear incombination with any of the following options: fuzz-seed. This optiontakes an integer number as its argument.Causes the source and destination IPv4/v6 addresses to be pseudo randomizedbut still maintain client/server relationships. Since the randomization isdeterministic based on the seed, you can reuse the same seed value torecreate the traffic.-N string, --pnat=string Rewrite IPv4/v6 addresses using pseudo-NAT. Thisoption may appear up to 2 times. This option must not appear incombination with any of the following options: srcipmap.Takes a comma delimited series of colon delimited CIDR netblock pairs.Each netblock pair is evaluated in order against the IP addresses. If theIP address in the packet matches the first netblock, it is rewritten usingthe second netblock as a mask against the high order bits.IPv4 Example:--pnat=192.168.0.0/16:10.77.0.0/16,172.16.0.0/12:10.1.0.0/24IPv6 Example:--pnat=[2001:db8::/32]:[dead::/16],[2001:db8::/32]:[::ffff:0:0/96]-S string, --srcipmap=string Rewrite source IPv4/v6 addresses usingpseudo-NAT. This option may appear up to 1 times. This option must notappear in combination with any of the following options: pnat.Works just like the --pnat option, but only affects the source IP addressesin the IPv4/v6 header.-D string, --dstipmap=string Rewrite destination IPv4/v6 addresses usingpseudo-NAT. This option may appear up to 1 times. This option must notappear in combination with any of the following options: pnat.Works just like the --pnat option, but only affects the destination IPaddresses in the IPv4/v6 header.-e string, --endpoints=string Rewrite IP addresses to be between twoendpoints. This option may appear up to 1 times. This option must appearin combination with the following options: cachefile.Takes a pair of colon delimited IPv4/v6 addresses which will be used torewrite all traffic to appear to be between the two IP addresses.IPv4 Example:--endpoints=172.16.0.1:172.16.0.2IPv6 Example:--endpoints=[2001:db8::dead:beef]:[::ffff:0:0:ac:f:0:2]--tcp-sequence=number Change TCP Sequence (and ACK) numbers /w given seed.This option takes an integer number as its argument. The value of numberis constrained to being:greater than or equal to 1The default number for this option is:0Change all TCP sequence numbers, and related sequence-acknowledgementnumbers. They will be shifted by a random amount based on the providedseed.-b, --skipbroadcast Skip rewriting broadcast/multicast IPv4/v6 addresses.By default --seed, --pnat and --endpoints will rewrite broadcast andmulticast IPv4/v6 and MAC addresses. Setting this flag will keepbroadcast/multicast IPv4/v6 and MAC addresses from being rewritten.-C, --fixcsum Force recalculation of IPv4/TCP/UDP header checksums.Causes each IPv4/v6 packet to have their checksums recalculated and fixed.Automatically enabled for packets modified with --seed, --pnat, --endpointsor --fixlen.-m number, --mtu=number Override default MTU length (1500 bytes). Thisoption may appear up to 1 times. This option takes an integer number asits argument. The value of number is constrained to being:in the range 1 through MAX_SNAPLENOverride the default 1500 byte MTU size for determining the maximum paddinglength (--fixlen=pad) or when truncating (--mtu-trunc).--mtu-trunc Truncate packets larger then specified MTU. This option mayappear up to 1 times.Similar to --fixlen, this option will truncate data in packets from Layer 3and above to be no larger then the MTU.-E, --efcs Remove Ethernet checksums (FCS) from end of frames.Note, this option is pretty dangerous! We do not actually check to see ifa FCS actually exists in the frame, we just blindly delete the last 4bytes. Hence, you should only use this if you know know that your OSprovides the FCS when reading raw packets.--ttl=string Modify the IPv4/v6 TTL/Hop Limit.Allows you to modify the TTL/Hop Limit of all the IPv4/v6 packets. Specifya number to hard-code the value or +/-value to increase or decrease by thevalue provided (limited to 1-255).Examples:--ttl=10--ttl=+7--ttl=-64--tos=number Set the IPv4 TOS/DiffServ/ECN byte. This option may appear upto 1 times. This option takes an integer number as its argument. Thevalue of number is constrained to being:in the range 0 through 255Allows you to override the TOS (also known as DiffServ/ECN) value in IPv4.--tclass=number Set the IPv6 Traffic Class byte. This option may appear upto 1 times. This option takes an integer number as its argument. Thevalue of number is constrained to being:in the range 0 through 255Allows you to override the IPv6 Traffic Class field.--flowlabel=number Set the IPv6 Flow Label. This option may appear up to 1times. This option takes an integer number as its argument. The value ofnumber is constrained to being:in the range 0 through 1048575Allows you to override the 20bit IPv6 Flow Label field. Has no effect onIPv4 packets.-F string, --fixlen=string Pad or truncate packet data to match headerlength. This option may appear up to 1 times.Packets may be truncated during capture if the snaplen is smaller then thepacket. This option allows you to modify the packet to pad the packet backout to the size stored in the IPv4/v6 header or rewrite the IP header totallength to reflect the stored packet length.pad Truncated packets will be padded out so that the packet length matchesthe IPv4 total lengthtrunc Truncated packets will have their IPv4 total length field rewrittento match the actual packet lengthdel Delete the packet--fuzz-seed=number Fuzz 1 in X packets. Edit bytes, length, or emulatepacket drop. This option takes an integer number as its argument. Thevalue of number is constrained to being:greater than or equal to 0The default number for this option is:0This fuzzing was designed as to test layer 7 protocols such as voipprotocols. It modifies randomly 1 out of X packets (where X =--fuzz-factor) in order for stateful protocols to cover more of their code.The random fuzzing actions focus on data start and end because it often isthe part of the data application protocols base their decisions on.Possible fuzzing actions list:* drop packet* reduce packet size* edit packet Bytes:* Not all Bytes have the same probability of appearance in real life.Replace with 0x00, 0xFF, or a random byte with equal likelihood.* Not all Bytes have the same significance in a packet.Replace the start, the end, or the middle of the packet with equallikelihood.* do nothing (7 out of 8 packets)--fuzz-factor=number Set the Fuzz 1 in X packet ratio (default 1 in 8packets). This option must appear in combination with the followingoptions: fuzz-seed. This option takes an integer number as its argument.The value of number is constrained to being:greater than or equal to 1The default number for this option is:8Sets the ratio of for --fuzz-seed option. By default this value is 8, whichmeans 1 in 8 packets are modified by fuzzing. Note that this ratio is basedon the random number generated by the supplied fuzz seed. Therefore bydefault you cannot expect that exactly every eighth packet will bemodified.--skipl2broadcast Skip rewriting broadcast/multicast Layer 2 addresses.By default, editing Layer 2 addresses will rewrite broadcast and multicastMAC addresses. Setting this flag will keep broadcast/multicast MACaddresses from being rewritten.--dlt=string Override output DLT encapsulation. This option may appear upto 1 times.By default, no DLT (data link type) conversion will be made. To change theDLT type of the output pcap, select one of the following values:enet Ethernet aka DLT_EN10MBhdlc Cisco HDLC aka DLT_C_HDLCjnpr_eth Juniper Ethernet DLT_C_JNPR_ETHERpppserial PPP Serial aka DLT_PPP_SERIALuser User specified Layer 2 header and DLT type--enet-dmac=string Override destination ethernet MAC addresses. Thisoption may appear up to 1 times.Takes a pair of comma deliminated ethernet MAC addresses which will replacethe destination MAC address of outbound packets. The first MAC addresswill be used for the server to client traffic and the optional second MACaddress will be used for the client to server traffic.Example:--enet-dmac=00:12:13:14:15:16,00:22:33:44:55:66--enet-smac=string Override source ethernet MAC addresses. This option mayappear up to 1 times.Takes a pair of comma deliminated ethernet MAC addresses which will replacethe source MAC address of outbound packets. The first MAC address will beused for the server to client traffic and the optional second MAC addresswill be used for the client to server traffic.Example:--enet-smac=00:12:13:14:15:16,00:22:33:44:55:66--enet-subsmac=string Substitute MAC addresses. This option may appear upto 9999 times.Allows you to rewrite ethernet MAC addresses of packets. It takes commadelimited pair or MACs address and rewrites all occurrences of the firstMAC with the value of the second MAC. Example:--enet-subsmac=00:12:13:14:15:16,00:22:33:44:55:66--enet-mac-seed=number Randomize MAC addresses. This option may appear upto 1 times. This option must not appear in combination with any of thefollowing options: enet-smac, enet-dmac, enet-subsmac. This option takesan integer number as its argument.Allows you to randomize ethernet MAC addresses of packets, mostly like what--seed option does for IPv4/IPv6 addresses.--enet-mac-seed-keep-bytes=number Randomize MAC addresses. This option mayappear up to 1 times. This option must appear in combination with thefollowing options: enet-mac-seed. This option takes an integer number asits argument. The value of number is constrained to being:in the range 1 through 6Keep some bytes untouched when usinging --enet-mac-seed option.--enet-vlan=string Specify ethernet 802.1q VLAN tag mode. This option mayappear up to 1 times.Allows you to rewrite ethernet frames to add a 802.1q header to standard802.3 ethernet headers or remove the 802.1q VLAN tag information.add Adds an 802.1q VLAN header to the existing 802.3 ethernet header. If aVLAN header already exists, a new VLAN header is added outside of theexisting header.Note that you will be allowed to run this option multiple times to createmore than 2 VLAN headers, however those packets will be valid. At most youshould have 2 X 802.1q VLAN tags, or outer an 802.1ad and an inner 802.1qVLAN tag.del Rewrites the existing 802.1q VLAN header as an 802.3 ethernet header--enet-vlan-tag=number Specify the new ethernet 802.1q VLAN tag value.This option may appear up to 1 times. This option must appear incombination with the following options: enet-vlan. This option takes aninteger number as its argument. The value of number is constrained tobeing:in the range 0 through 4095--enet-vlan-cfi=number Specify the ethernet 802.1q VLAN CFI value. Thisoption may appear up to 1 times. This option must appear in combinationwith the following options: enet-vlan. This option takes an integer numberas its argument. The value of number is constrained to being:in the range 0 through 1--enet-vlan-pri=number Specify the ethernet 802.1q VLAN priority. Thisoption may appear up to 1 times. This option must appear in combinationwith the following options: enet-vlan. This option takes an integer numberas its argument. The value of number is constrained to being:in the range 0 through 7--enet-vlan-proto=string Specify VLAN tag protocol 802.1q or 802.1ad. Thisoption may appear up to 1 times.Allows you to specify the protocol of the added VLAN tags.802.1q Specifies that 802.1q VLAN headers are to be added. This is thedefault.802.1ad Specifies that 802.1ad Q-in-Q VLAN headers are to be added. To makevalid packets, input packets must already have 802.1q VLAN headers.--hdlc-control=number Specify HDLC control value. This option may appearup to 1 times. This option takes an integer number as its argument.The Cisco HDLC header has a 1 byte "control" field. Apparently this shouldalways be 0, but if you can use any 1 byte value.--hdlc-address=number Specify HDLC address. This option may appear up to 1times. This option takes an integer number as its argument.The Cisco HDLC header has a 1 byte "address" field which has two validvalues:0x0F Unicast0xBF BroadcastYou can however specify any single byte value.--user-dlt=number Set output file DLT type. This option may appear up to 1times. This option takes an integer number as its argument.Set the DLT value of the output pcap file.--user-dlink=string Rewrite Data-Link layer with user specified data. Thisoption may appear up to 2 times.Provide a series of comma deliminated hex values which will be used torewrite or create the Layer 2 header of the packets. The first instance ofthis argument will rewrite both server and client traffic, but if thisargument is specified a second time, it will be used for the clienttraffic.Example:--user-dlink=01,02,03,04,05,06,00,1A,2B,3C,4D,5E,6F,08,00-d number, --dbug=number Enable debugging output. This option may appearup to 1 times. This option takes an integer number as its argument. Thevalue of number is constrained to being:in the range 0 through 5The default number for this option is:0If configured with --enable-debug, then you can specify a verbosity levelfor debugging output. Higher numbers increase verbosity.-i string, --infile=string Input pcap file to be processed. This optionmay appear up to 1 times.-o string, --outfile=string Output pcap file. This option may appear up to1 times.-c string, --cachefile=string Split traffic via tcpprep cache file. Thisoption may appear up to 1 times.Use tcpprep cache file to split traffic based upon client/serverrelationships.-v, --verbose Print decoded packets via tcpdump to STDOUT. This option mayappear up to 1 times.-A string, --decode=string Arguments passed to tcpdump decoder. Thisoption may appear up to 1 times. This option must appear in combinationwith the following options: verbose.When enabling verbose mode (-v) you may also specify one or more additionalarguments to pass to tcpdump to modify the way packets are decoded. Bydefault, -n and -l are used. Be sure to quote the arguments so that theyare not interpreted by tcprewrite. Please see the tcpdump(1) man page fora complete list of options.--fragroute=string Parse fragroute configuration file. This option mayappear up to 1 times.Enable advanced evasion techniques using the built-in fragroute(8) engine.See the fragroute(8) man page for more details. Important: tcprewrite doesnot support the delay, echo or print commands.--fragdir=string Which flows to apply fragroute to: c2s, s2c, both. Thisoption may appear up to 1 times. This option must appear in combinationwith the following options: cachefile.Apply the fragroute engine to packets going c2s, s2c or both when using acache file.--skip-soft-errors Skip writing packets with soft errors. This option mayappear up to 1 times.In some cases, packets can not be decoded or the requested editing is notpossible. Normally these packets are written to the output file uneditedso that tcpprep cache files can still be used, but if you wish, thesepackets can be suppressed.One example of this is 802.11 management frames which contain no data.-V, --version Print version information.-h, --less-help Display less usage information and exit.-H, --help Display usage information and exit.-!, --more-help Pass the extended usage information through a pager.--save-opts [=cfgfile] Save the option state to cfgfile. The default isthe last configuration file listed in the OPTION PRESETS section, below.The command will exit after updating the config file.--load-opts=cfgfile, --no-load-opts Load options from cfgfile. Theno-load-opts form will disable the loading of earlier config/rc/ini files.--no-load-opts is handled early, out of order.OPTION PRESETS

Any option that is not marked as not presettable may be preset by loading values from configuration ("RC" or ".INI") file(s). The homerc file is "$$/", unless that is a directory. In that case, the file ".tcprewriterc" is searched for within that directory.

FILES

See OPTION PRESETS for configuration files.

EXIT STATUS

One of the following exit values will be returned:
0 (EXIT_SUCCESS) Successful program execution.

1 (EXIT_FAILURE) The operation failed or the command syntax was not
valid.

66 (EX_NOINPUT) A specified configuration file could not be loaded.

70 (EX_SOFTWARE) libopts had an internal operational error. Please
report it to autogen-users@lists.sourceforge.net. Thank you.

AUTHORS

Copyright 2013-2022 Fred Klassen - AppNeta Copyright 2000-2012 Aaron Turner For support please use the tcpreplay-users@lists.sourceforge.net mailing list. The latest version of this software is always available from: http://tcpreplay.appneta.com/

COPYRIGHT

BUGS

Please send bug reports to: tcpreplay-users@lists.sourceforge.net

NOTES

This manual page was AutoGen-erated from the tcprewrite option definitions.