NAME¶
text2pcap - Generate a capture file from an ASCII hexdump of packets
SYNOPSIS¶
text2pcap [
-a ] [
-d ] [
-e <l3pid> ] [
-h ] [
-i <proto> ] [
-l <typenum> ] [
-m <max-packet> ] [
-o hex|oct|dec ] [
-q ] [
-s <srcport>,<destport>,<tag> ] [
-S <srcport>,<destport>,<ppi> ] [
-t <timefmt> ] [
-T <srcport>,<destport> ] [
-u <srcport>,<destport> ] <
infile>|- <
outfile>|-
DESCRIPTION¶
Text2pcap is a program that reads in an ASCII hex dump and writes the
data described into a
libpcap 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 and surrounded
with a space. Each line begins with an offset describing the position in the
file. 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 e0 1e a7 05 6f 00 10 ........
000008 5a a0 b9 12 08 00 46 00 ........
000010 03 68 00 00 00 00 0a 2e ........
000018 ee 33 0f 19 08 7f 0f 19 ........
000020 03 80 94 04 00 00 10 01 ........
000028 16 a2 0a 00 03 50 00 0c ........
000030 01 01 0f 19 03 80 11 01 ........
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 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.
- -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 12 to indicate a raw IP packet to Wireshark. Note that -l
12 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).
- -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.
- -m <max-packet>
- Set the maximum packet length, default is 64000. Useful for
testing various packet boundaries when only an application level
datastream is available. Example:
od -Ax -tx1 stream | text2pcap -m1460 -T1234,1234 - stream.pcap
will convert from plain datastream format to a sequence of Ethernet TCP
packets.
- -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.
SEE ALSO¶
od(1),
pcap(3),
wireshark(1),
tshark(1),
dumpcap(1),
mergecap(1),
editcap(1),
strptime(3),
pcap-filter(7) or
tcpdump(8) if it doesn't exist.
NOTES¶
Text2pcap is part of the
Wireshark distribution. The latest
version of
Wireshark can be found at <
http://www.wireshark.org>.
AUTHORS¶
Ashok Narayanan <ashokn[AT]cisco.com>