forked from osmocom/wireshark
![João Valverde](/assets/img/avatar_default.png)
Now that nmake build system has been removed they are not needed anymore. Change-Id: I88075f955bb4349185859c1af4be22e53de5850f Reviewed-on: https://code.wireshark.org/review/16050 Petri-Dish: João Valverde <j@v6e.pt> Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org> Reviewed-by: João Valverde <j@v6e.pt>
91 lines
4 KiB
Text
91 lines
4 KiB
Text
This is a very quick and very dirty guide to adding support for new
|
|
capture file formats. If you see any errors or have any improvements,
|
|
submit patches - free software is a community effort....
|
|
|
|
To add the ability to read a new capture file format, you have to:
|
|
|
|
add a new WTAP_FILE_ value for the file type to
|
|
"wiretap/wtap.h";
|
|
|
|
write an "open" routine that can read the beginning of the
|
|
capture file and figure out if it's in that format or not,
|
|
either by looking at a magic number at the beginning or by using
|
|
some form of heuristic to determine if it's a file of that type
|
|
(if the file format has a magic number, that's what should be
|
|
used);
|
|
|
|
write a "read" routine that can read a packet from the file and
|
|
supply the packet length, captured data length, time stamp, and
|
|
packet pseudo-header (if any) and data, and have the "open"
|
|
routine set the "subtype_read" member of the "wtap" structure
|
|
supplied to it to point to that routine;
|
|
|
|
write a "seek and read" routine that can seek to a specified
|
|
location in the file for a packet and supply the packet
|
|
pseudo-header (if any) and data, and have the "open" routine set
|
|
the "subtype_seek_read" member of the "wtap" structure to point
|
|
to that routine;
|
|
|
|
write a "close" routine, if necessary (if, for example, the
|
|
"open" routine allocates any memory), and set the
|
|
"subtype_close" member of the "wtap" structure to point to it,
|
|
otherwise leave it set to NULL;
|
|
|
|
add a pointer to the "open" routine to the "open_routines_base[]"
|
|
table in "wiretap/file_access.c" - if it uses a magic number, put
|
|
it in the first section of that list, and, if it uses a heuristic,
|
|
put it in the second section, preferably putting the heuristic
|
|
routines for binary files before the heuristic routines for text
|
|
files;
|
|
|
|
add an entry for that file type in the "dump_open_table_base[]" in
|
|
"wiretap/file_access.c", giving a descriptive name, a short name
|
|
that's convenient to type on a command line (no blanks or capital
|
|
letters, please), common file extensions to open and save, a flag
|
|
if it can be compressed with gzip (currently unused) and pointers
|
|
to the "can_write_encap" and "dump_open" routines if writing that
|
|
file is supported (see below), otherwise just null pointers.
|
|
|
|
Wiretap applications typically first perform sequential reads through
|
|
the capture file and may later do "seek and read" for individual frames.
|
|
The "read" routine should set the variable data_offset to the byte
|
|
offset within the capture file from which the "seek and read" routine
|
|
will read. If the capture records consist of:
|
|
|
|
capture record header
|
|
pseudo-header (e.g., for ATM)
|
|
frame data
|
|
|
|
then data_offset should point to the pseudo-header. The first
|
|
sequential read pass will process and store the capture record header
|
|
data, but it will not store the pseudo-header. Note that the
|
|
seek_and_read routine should work with the "random_fh" file handle
|
|
of the passed in wtap struct, instead of the "fh" file habndle used
|
|
in the normal read routine.
|
|
|
|
To add the ability to write a new capture file format, you have to:
|
|
|
|
add a "can_write_encap" routine that returns an indication of
|
|
whether a given packet encapsulation format is supported by the
|
|
new capture file format;
|
|
|
|
add a "dump_open" routine that starts writing a file (writing
|
|
headers, allocating data structures, etc.);
|
|
|
|
add a "dump" routine to write a packet to a file, and have the
|
|
"dump_open" routine set the "subtype_write" member of the
|
|
"wtap_dumper" structure passed to it to point to it;
|
|
|
|
add a "dump_close" routine, if necessary (if, for example, the
|
|
"dump_open" routine allocates any memory, or if some of the file
|
|
header can be written only after all the packets have been
|
|
written), and have the "dump_open" routine set the
|
|
"subtype_close" member of the "wtap_dumper" structure to point
|
|
to it;
|
|
|
|
put pointers to the "can_write_encap" and "dump_open" routines
|
|
in the "dump_open_table_base[]" entry for that file type.
|
|
|
|
In the wiretap directory, add your source file to CMakelists.txt and
|
|
your source and header file to Makefile.am.
|