text2pcap(1)
NAME
text2pcap - Generate a capture file from an ASCII hexdump of packets
SYNOPSIS
text2pcap [ -a ] [ -d ] [ -D ] [ -e <l3pid> ] [ -h ] [ -i <proto> ] [ -l <typenum> ] [ -n ] [ -m <max-packet> ] [ -o hex|oct|dec ] [ -q ] [ -s <srcport>,<destport>,<tag> ] [ -S <srcport>,<destport>,<ppi> ] [ -t <timefmt> ] [ -T <srcport>,<destport> ] [ -u <srcport>,<destport> ] [ -v ] <infile>|- <outfile>|-
DESCRIPTION
Text2pcap is a program that reads in an ASCII hex dump and writes the
data described into a pcap capture file. text2pcap can read hexdumps
with multiple packets in them, and build a capture file of multiple
packets. text2pcap is also capable of generating dummy Ethernet, IP
and UDP, TCP, or SCTP headers, in order to build fully processable
packet dumps from hexdumps of application-level data only.
Text2pcap understands a hexdump of the form generated by od -Ax -tx1
-v. In other words, each byte is individually displayed, with spaces
separating the bytes from each other. Each line begins with an offset
describing the position in the file, with a space separating it from
the following bytes. The offset is a hex number (can also be octal or
decimal - see -o), of more than two hex digits. Here is a sample dump
that text2pcap can recognize:
000000 00 0e b6 00 00 02 00 0e b6 00 00 01 08 00 45 00
000010 00 28 00 00 00 00 ff 01 37 d1 c0 00 02 01 c0 00
000020 02 02 08 00 a6 2f 00 01 00 01 48 65 6c 6c 6f 20
000030 57 6f 72 6c 64 21
000036
There is no limit on the width or number of bytes per line. Also the
text dump at the end of the line is ignored. Bytes/hex numbers can be
uppercase or lowercase. Any text before the offset is ignored,
including email forwarding characters '>'. Any lines of text between
the bytestring lines is ignored. The offsets are used to track the
bytes, so offsets must be correct. Any line which has only bytes
without a leading offset is ignored. An offset is recognized as being a
hex number longer than two characters. Any text after the bytes is
ignored (e.g. the character dump). Any hex numbers in this text are
also ignored. An offset of zero is indicative of starting a new packet,
so a single text file with a series of hexdumps can be converted into a
packet capture with multiple packets. Packets may be preceded by a
timestamp. These are interpreted according to the format given on the
command line (see -t). If not, the first packet is timestamped with the
current time the conversion takes place. Multiple packets are written
with timestamps differing by one microsecond each. In general, short
of these restrictions, text2pcap is pretty liberal about reading in
hexdumps and has been tested with a variety of mangled outputs
(including being forwarded through email multiple times, with limited
line wrap etc.)
There are a couple of other special features to note. Any line where
the first non-whitespace character is '#' will be ignored as a comment.
Any line beginning with #TEXT2PCAP is a directive and options can be
inserted after this command to be processed by text2pcap. Currently
there are no directives implemented; in the future, these may be used
to give more fine grained control on the dump and the way it should be
processed e.g. timestamps, encapsulation type etc.
Text2pcap also allows the user to read in dumps of application-level
data, by inserting dummy L2, L3 and L4 headers before each packet. The
user can elect to insert Ethernet headers, Ethernet and IP, or
Ethernet, IP and UDP/TCP/SCTP headers before each packet. This allows
Wireshark or any other full-packet decoder to handle these dumps.
OPTIONS
-a Enables ASCII text dump identification. It allows one to identify
the start of the ASCII text dump and not include it in the packet
even if it looks like HEX.
NOTE: Do not enable it if the input file does not contain the ASCII
text dump.
-d Displays debugging information during the process. Can be used
multiple times to generate more debugging information.
-D The text before the packet starts either with an I or O indicating
that the packet is inbound or outbound. This is only stored if the
output format is PCAP-NG.
-e <l3pid>
Include a dummy Ethernet header before each packet. Specify the
L3PID for the Ethernet header in hex. Use this option if your dump
has Layer 3 header and payload (e.g. IP header), but no Layer 2
encapsulation. Example: -e 0x806 to specify an ARP packet.
For IP packets, instead of generating a fake Ethernet header you
can also use -l 101 to indicate a raw IP packet to Wireshark. Note
that -l 101 does not work for any non-IP Layer 3 packet (e.g. ARP),
whereas generating a dummy Ethernet header with -e works for any
sort of L3 packet.
-h Displays a help message.
-i <proto>
Include dummy IP headers before each packet. Specify the IP
protocol for the packet in decimal. Use this option if your dump is
the payload of an IP packet (i.e. has complete L4 information) but
does not have an IP header with each packet. Note that an
appropriate Ethernet header is automatically included with each
packet as well. Example: -i 46 to specify an RSVP packet (IP
protocol 46). See
<http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml>
for the complete list of assigned internet protocol numbers.
-l Specify the link-layer header type of this packet. Default is
Ethernet (1). See <http://www.tcpdump.org/linktypes.html> for the
complete list of possible encapsulations. Note that this option
should be used if your dump is a complete hex dump of an
encapsulated packet and you wish to specify the exact type of
encapsulation. Example: -l 7 for ARCNet packets encapsulated BSD-
style.
-m <max-packet>
Set the maximum packet length, default is 65535. Useful for
testing various packet boundaries when only an application level
datastream is available. Example:
od -Ax -tx1 -v stream | text2pcap -m1460 -T1234,1234 - stream.pcap
will convert from plain datastream format to a sequence of Ethernet
TCP packets.
-n Write PCAP-NG file instead of a PCAP.
-o hex|oct|dec
Specify the radix for the offsets (hex, octal or decimal). Defaults
to hex. This corresponds to the "-A" option for od.
-q Be completely quiet during the process.
-s <srcport>,<destport>,<tag>
Include dummy SCTP headers before each packet. Specify, in
decimal, the source and destination SCTP ports, and verification
tag, for the packet. Use this option if your dump is the SCTP
payload of a packet but does not include any SCTP, IP or Ethernet
headers. Note that appropriate Ethernet and IP headers are
automatically also included with each packet. A CRC32C checksum
will be put into the SCTP header.
-S <srcport>,<destport>,<ppi>
Include dummy SCTP headers before each packet. Specify, in
decimal, the source and destination SCTP ports, and a verification
tag of 0, for the packet, and prepend a dummy SCTP DATA chunk
header with a payload protocol identifier if ppi. Use this option
if your dump is the SCTP payload of a packet but does not include
any SCTP, IP or Ethernet headers. Note that appropriate Ethernet
and IP headers are automatically included with each packet. A
CRC32C checksum will be put into the SCTP header.
-t <timefmt>
Treats the text before the packet as a date/time code; timefmt is a
format string of the sort supported by strptime(3). Example: The
time "10:15:14.5476" has the format code "%H:%M:%S."
NOTE: The subsecond component delimiter must be specified (.) but
no pattern is required; the remaining number is assumed to be
fractions of a second.
NOTE: Date/time fields from the current date/time are used as the
default for unspecified fields.
-T <srcport>,<destport>
Include dummy TCP headers before each packet. Specify the source
and destination TCP ports for the packet in decimal. Use this
option if your dump is the TCP payload of a packet but does not
include any TCP, IP or Ethernet headers. Note that appropriate
Ethernet and IP headers are automatically also included with each
packet. Sequence numbers will start at 0.
-u <srcport>,<destport>
Include dummy UDP headers before each packet. Specify the source
and destination UDP ports for the packet in decimal. Use this
option if your dump is the UDP payload of a packet but does not
include any UDP, IP or Ethernet headers. Note that appropriate
Ethernet and IP headers are automatically also included with each
packet. Example: -u1000,69 to make the packets look like TFTP/UDP
packets.
-v Print the version and exit.
-4 <srcip>,<destip>
Prepend dummy IP header with specified IPv4 dest and source
address. This option should be accompanied by one of the following
options: -i, -s, -S, -T, -u Use this option to apply "custom" IP
addresses. Example: -4 10.0.0.1,10.0.0.2 to use 10.0.0.1 and
10.0.0.2 for all IP packets.
-6 <srcip>,<destip>
Prepend dummy IP header with specified IPv6 dest and source
address. This option should be accompanied by one of the following
options: -i, -s, -S, -T, -u Use this option to apply "custom" IP
addresses. Example: -6 fe80:0:0:0:202:b3ff:fe1e:8329,
2001:0db8:85a3:0000:0000:8a2e:0370:7334 to use
fe80:0:0:0:202:b3ff:fe1e:8329 and
2001:0db8:85a3:0000:0000:8a2e:0370:7334 for all IP packets.
SEE ALSO
od(1), pcap(3), wireshark(1), tshark(1), dumpcap(1), mergecap(1), editcap(1), strptime(3), pcap-filter(7) or tcpdump(8)
NOTES
Text2pcap is part of the Wireshark distribution. The latest version of Wireshark can be found at <https://www.wireshark.org>.
AUTHORS
Ashok Narayanan <ashokn[AT]cisco.com>
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