text2pcap
TEXT2PCAP(1) The Ethereal Network Analyzer TEXT2PCAP(1)
NAME
text2pcap - Generate a capture file from an ASCII hexdump of packets
SYNOPSYS
text2pcap [ -h ] [ -d ] [ -q ] [ -o hex|oct ] [ -l typenum ]
[ -e l3pid ] [ -i proto ] [ -m max-packet ] [ -u srcport,destport ]
[ -T srcport,destport ] [ -s srcport,destport,tag ] [ -S srcport,dest-
port,ppi ] [ -t timefmt ] infile outfile
DESCRIPTION
Text2pcap is a program that reads in an ASCII hex dump and writes the
data described into a libpcap-style 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 Ether-
net, IP and UDP, TCP, or SCTP headers, in order to build fully process-
able packet dumps from hexdumps of application-level data only.
Text2pcap understands a hexdump of the form generated by od -t x1. 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 - see -o), of more
than two hex digits. Here is a sample dump that text2pcap can recog-
nize:
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, includ-
ing 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 num-
ber 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. Multiple packets are read in with
timestamps differing by one second 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 for-
warded 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 Ether-
net, IP and UDP/TCP headers before each packet. This allows Ethereal or
any other full-packet decoder to handle these dumps.
OPTIONS
-h Displays a help message.
-d Displays debugging information during the process. Can be used mul-
tiple times to generate more debugging information.
-q Be completely quiet during the process.
-o hex|oct
Specify the radix for the offsets (hex or octal). Defaults to hex.
This corresponds to the "-A" option for od.
-l Specify the link-layer type of this packet. Default is Ethernet
(1). See net/bpf.h for the complete list of possible encapsula-
tions. Note that this option should be used if your dump is a com-
plete hex dump of an encapsulated packet and you wish to specify
the exact type of encapsulation. Example: -l 7 for ARCNet packets.
-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 Ethereal. 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.
-i proto
Include dummy IP headers before each packet. Specify the IP proto-
col 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. Note that this automatically includes an
appropriate Ethernet header as well. Example: -i 46 to specify an
RSVP packet (IP protocol 46).
-m max-packet
Set the maximum packet length, default is 64000. Useful for test-
ing various packet boundaries when only an application level datas-
tream 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.
-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 this automati-
cally includes appropriate Ethernet and IP headers with each
packet. Example: -u 1000,69 to make the packets look like TFTP/UDP
packets.
-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 this automati-
cally includes appropriate Ethernet and IP headers with each
packet. Sequence numbers will start a 0.
-s srcport,destport,tag
Include dummy SCTP headers before each packet. Specify, in deci-
mal, 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 this automatically includes appropriate Ethernet and IP
headers 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 deci-
mal, 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 this automatically includes
appropriate Ethernet and IP headers 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 frac-
tions of a second.
SEE ALSO
tcpdump(8), pcap(3), ethereal(1), editcap(1), strptime(3).
NOTES
Text2pcap is part of the Ethereal distribution. The latest version of
Ethereal can be found at http://www.ethereal.com.
AUTHORS
Ashok Narayanan <ashokn[AT]cisco.com>
0.10.13 2005-10-10 TEXT2PCAP(1)
