SYNOPSIS

tcprewrite [-flag [value]]... [--opt-name [[=| ]value]]...

All arguments must be options.

DESCRIPTION

This manual page briefly documents the tcprewrite command. Tcprewrite is a tool to rewrite packets stored in pcap(3) file format, such as crated by tools such as tcpdump(1) and ethereal(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

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.synfin.net/trac/wiki/manual

OPTIONS

-r string, --portmap=string

Rewrite TCP/UDP ports. This option may appear up to -1 times.

Specify a list of comma delimited port mappingings consisting of colon delimited port number pairs. Each colon delimited port pair consists of the 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 takes an integer number as its argument.

Causes the source and destination IPv4/v6 addresses to be pseudo randomized but still maintain client/server relationships. Since the randomization is deterministic based on the seed, you can reuse the same seed value to recreate the traffic.

-N string, --pnat=string

Rewrite IPv4/v6 addresses using pseudo-NAT. This option may appear up to 2 times. This option must not appear in combination 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 the IP address in the packet matches the first netblock, it is rewriten using the second netblock as a mask against the high order bits.

IPv4 Example:

    --pnat=192.168.0.0/16:10.77.0.0/16,172.16.0.0/12:10.1.0.0/24

IPv6 Example:

    --pnat=[2001:db8::/32]:[dead::/16],[2001:db8::/32]:[::ffff:0:0/96]

-S string, --srcipmap=string

Rewrite source IPv4/v6 addresses using pseudo-NAT. This option may appear up to 1 times. This option must not appear in combination with any of the following options: pnat.

Works just like the --pnat option, but only affects the source IP addresses in the IPv4/v6 header.

-D string, --dstipmap=string

Rewrite destination IPv4/v6 addresses using pseudo-NAT. This option may appear up to 1 times. This option must not appear in combination with any of the following options: pnat.

Works just like the --pnat option, but only affects the destination IP addresses in the IPv4/v6 header.

-e string, --endpoints=string

Rewrite IP addresses to be between two endpoints. This option may appear up to 1 times. This option must appear in combination with the following options: cachefile.

Takes a pair of colon delimited IPv4/v6 addresses which will be used to rewrite all traffic to appear to be between the two IP's.

IPv4 Example:

    --endpoints=172.16.0.1:172.16.0.2

IPv6 Example:

    --endpoints=[2001:db8::dead:beef]:[::ffff:0:0:ac:f:0:2]

-b, --skipbroadcast

Skip rewriting broadcast/multicast IPv4/v6 addresses.

By default --seed, --pnat and --endpoints will rewrite broadcast and multicast IPv4/v6 and MAC addresses.      Setting this flag
will keep broadcast/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 it's checksums recalcualted and fixed. Automatically enabled for packets modified with --seed, --pnat, --endpoints or --fixlen.

-m number, --mtu=number

Override default MTU length (1500 bytes). This option may appear up to 1 times. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  1 through MAXPACKET

Override the default 1500 byte MTU size for determining the maximum padding length (--fixlen=pad) or when truncating (--mtu-trunc).

--mtu-trunc

Truncate packets larger then specified MTU. This option may appear up to 1 times.

Similar to --fixlen, this option will truncate data in packets from Layer 3 and 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 don't actually check to see if a FCS actually exists in the frame, we just blindly delete the last two bytes. Hence, you should only use this if you know know that your OS provides 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. Specify a number to hard-code the value or +/-value to increase or decrease by the value 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 up to 1 times. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  0 through 255

Allows 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 up to 1 times. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  0 through 255

Allows you to override the IPv6 Traffic Class field.

--flowlabel=number

Set the IPv6 Flow Label. This option may appear up to 1 times. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  0 through 1048575

Allows you to override the 20bit IPv6 Flow Label field. Has no effect on IPv4 packets.

-F string, --fixlen=string

Pad or truncate packet data to match header length. This option may appear up to 1 times.

Packets may be truncated during capture if the snaplen is smaller then the packet. This option allows you to modify the packet to pad the packet back out to the size stored in the IPv4/v6 header or rewrite the IP header total length to reflect the stored packet length.

pad Truncated packets will be padded out so that the packet length matches the IPv4 total length

trunc Truncated packets will have their IPv4 total length field rewritten to match the actual packet length

del Delete the packet

--skipl2broadcast

Skip rewriting broadcast/multicast Layer 2 addresses.

By default, editing Layer 2 addresses will rewrite broadcast and multicast MAC addresses.  Setting this flag
will keep broadcast/multicast MAC addresses from being rewritten.

--dlt=string

Override output DLT encapsulation. This option may appear up to 1 times.

By default, no DLT (data link type) conversion will be made. To change the DLT type of the output pcap, select one of the following values:

enet Ethernet aka DLT_EN10MB

hdlc Cisco HDLC aka DLT_C_HDLC

user User specified Layer 2 header and DLT type

--enet-dmac=string

Override destination ethernet MAC addresses. This option may appear up to 1 times.

Takes a pair of comma deliminated ethernet MAC addresses which will replace the destination MAC address of outbound packets. The first MAC address will be used for the server to client traffic and the optional second MAC address 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 may appear up to 1 times.

Takes a pair of comma deliminated ethernet MAC addresses which will replace the source MAC address of outbound packets. The first MAC address will be used for the server to client traffic and the optional second MAC address will be used for the client to server traffic.

Example:

    --enet-smac=00:12:13:14:15:16,00:22:33:44:55:66

--enet-vlan=string

Specify ethernet 802.1q VLAN tag mode. This option may appear up to 1 times.

Allows you to rewrite ethernet frames to add a 802.1q header to standard 802.3 ethernet headers or remove the 802.1q VLAN tag information.

add Rewrites the existing 802.3 ethernet header as an 802.1q VLAN header

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 in combination with the following options: enet-vlan. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  0 through 4095

--enet-vlan-cfi=number

Specify the ethernet 802.1q VLAN CFI value. This option may appear up to 1 times. This option must appear in combination with the following options: enet-vlan. This option takes an integer number as 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. This option may appear up to 1 times. This option must appear in combination with the following options: enet-vlan. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  0 through 7

--hdlc-control=number

Specify HDLC control value. This option may appear up to 1 times. This option takes an integer number as its argument.

The Cisco HDLC header has a 1 byte "control" field. Apparently this should always be 0, but if you can use any 1 byte value.

--hdlc-address=number

Specify HDLC address. This option may appear up to 1 times. This option takes an integer number as its argument.

The Cisco HDLC header has a 1 byte "address" field which has two valid values:

0x0F Unicast

0xBF Broadcast
You can however specify any single byte value.

--user-dlt=number

Set output file DLT type. This option may appear up to 1 times. 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. This option may appear up to 2 times.

Provide a series of comma deliminated hex values which will be used to rewrite or create the Layer 2 header of the packets. The first instance of this argument will rewrite both server and client traffic, but if this argument is specified a second time, it will be used for the client traffic.

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 appear up to 1 times. This option takes an integer number as its argument. The value of number is constrained to being:

in the range  0 through 5

The default number for this option is:
    
 0

If configured with --enable-debug, then you can specify a verbosity level for debugging output. Higher numbers increase verbosity.

-i string, --infile=string

Input pcap file to be processed. This option may appear up to 1 times.

-o string, --outfile=string

Output pcap file. This option may appear up to 1 times.

-c string, --cachefile=string

Split traffic via tcpprep cache file. This option may appear up to 1 times.

Use tcpprep cache file to split traffic based upon client/server relationships.

-v, --verbose

Print decoded packets via tcpdump to STDOUT. This option may appear up to 1 times.

-A string, --decode=string

Arguments passed to tcpdump decoder. This option may appear up to 1 times. This option must appear in combination with the following options: verbose.

When enabling verbose mode (-v) you may also specify one or more additional arguments to pass to tcpdump to modify the way packets are decoded. By default, -n and -l are used. Be sure to quote the arguments so that they are not interpreted by tcprewrite. Please see the tcpdump(1) man page for a complete list of options.

--fragroute=string

Parse fragroute configuration file. This option may appear 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 does not support the delay, echo or print commands.

--fragdir=string

Which flows to apply fragroute to: c2s, s2c, both. This option may appear up to 1 times. This option must appear in combination with the following options: cachefile.

Apply the fragroute engine to packets going c2s, s2c or both when using a cache file.

--skip-soft-errors

Skip writing packets with soft errors. This option may appear up to 1 times.

In some cases, packets can't be decoded or the requested editing is not possible. Normally these packets are written to the output file unedited so that tcpprep cache files can still be used, but if you wish, these packets 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

Extended usage information passed thru pager.

- [rcfile], --save-opts[=rcfile]

Save the option state to rcfile. The default is the last configuration file listed in the OPTION PRESETS section, below.

- rcfile, --load-opts=rcfile, --no-load-opts

Load options from rcfile. The no-load-opts form will disable the loading of earlier 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.

AUTHOR

Copyright 2000-2010 Aaron Turner

For support please use the [email protected] mailing list.

The latest version of this software is always available from: http://tcpreplay.synfin.net/

Released under the Free BSD License.

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