6 This file is a HOWTO for Wireshark developers. It describes how to start coding
7 a Wireshark protocol dissector and the use of some of the important functions
10 This file is compiled to give in depth information on Wireshark.
11 It is by no means all inclusive and complete. Please feel free to send
12 remarks and patches to the developer mailing list.
16 Before starting to develop a new dissector, a "running" Wireshark build
17 environment is required - there's no such thing as a standalone "dissector
20 How to setup such an environment is platform dependent; detailed information
21 about these steps can be found in the "Developer's Guide" (available from:
22 http://www.wireshark.org) and in the INSTALL and README files of the sources
25 0.1. General README files.
27 You'll find additional information in the following README files:
29 - README.capture - the capture engine internals
30 - README.design - Wireshark software design - incomplete
31 - README.developer - this file
32 - README.display_filter - Display Filter Engine
33 - README.idl2wrs - CORBA IDL converter
34 - README.packaging - how to distribute a software package containing WS
35 - README.regression - regression testing of WS and TS
36 - README.stats_tree - a tree statistics counting specific packets
37 - README.tapping - "tap" a dissector to get protocol specific events
38 - README.xml-output - how to work with the PDML exported output
39 - wiretap/README.developer - how to add additional capture file types to
42 0.2. Dissector related README files.
44 You'll find additional dissector related information in the following README
47 - README.binarytrees - fast access to large data collections
48 - README.heuristic - what are heuristic dissectors and how to write them
49 - README.malloc - how to obtain "memory leak free" memory
50 - README.plugins - how to "pluginize" a dissector
51 - README.request_response_tracking - how to track req./resp. times and such
55 James Coe <jammer[AT]cin.net>
56 Gilbert Ramirez <gram[AT]alumni.rice.edu>
57 Jeff Foster <jfoste[AT]woodward.com>
58 Olivier Abad <oabad[AT]cybercable.fr>
59 Laurent Deniel <laurent.deniel[AT]free.fr>
60 Gerald Combs <gerald[AT]wireshark.org>
61 Guy Harris <guy[AT]alum.mit.edu>
62 Ulf Lamping <ulf.lamping[AT]web.de>
64 1. Setting up your protocol dissector code.
66 This section provides skeleton code for a protocol dissector. It also explains
67 the basic functions needed to enter values in the traffic summary columns,
68 add to the protocol tree, and work with registered header fields.
74 Wireshark runs on many platforms, and can be compiled with a number of
75 different compilers; here are some rules for writing code that will work
76 on multiple platforms.
78 Don't use C++-style comments (comments beginning with "//" and running
79 to the end of the line); Wireshark's dissectors are written in C, and
80 thus run through C rather than C++ compilers, and not all C compilers
81 support C++-style comments (GCC does, but IBM's C compiler for AIX, for
82 example, doesn't do so by default).
84 Don't initialize variables in their declaration with non-constant
85 values. Not all compilers support this. E.g. don't use
86 guint32 i = somearray[2];
92 Don't use zero-length arrays; not all compilers support them. If an
93 array would have no members, just leave it out.
95 Don't declare variables in the middle of executable code; not all C
96 compilers support that. Variables should be declared outside a
97 function, or at the beginning of a function or compound statement.
99 Don't use anonymous unions; not all compilers support it.
106 } u; /* have a name here */
109 Don't use "uchar", "u_char", "ushort", "u_short", "uint", "u_int",
110 "ulong", "u_long" or "boolean"; they aren't defined on all platforms.
111 If you want an 8-bit unsigned quantity, use "guint8"; if you want an
112 8-bit character value with the 8th bit not interpreted as a sign bit,
113 use "guchar"; if you want a 16-bit unsigned quantity, use "guint16";
114 if you want a 32-bit unsigned quantity, use "guint32"; and if you want
115 an "int-sized" unsigned quantity, use "guint"; if you want a boolean,
116 use "gboolean". Use "%d", "%u", "%x", and "%o" to print those types;
117 don't use "%ld", "%lu", "%lx", or "%lo", as longs are 64 bits long on
118 many platforms, but "guint32" is 32 bits long.
120 Don't use "long" to mean "signed 32-bit integer", and don't use
121 "unsigned long" to mean "unsigned 32-bit integer"; "long"s are 64 bits
122 long on many platforms. Use "gint32" for signed 32-bit integers and use
123 "guint32" for unsigned 32-bit integers.
125 Don't use "long" to mean "signed 64-bit integer" and don't use "unsigned
126 long" to mean "unsigned 64-bit integer"; "long"s are 32 bits long on
127 many other platforms. Don't use "long long" or "unsigned long long",
128 either, as not all platforms support them; use "gint64" or "guint64",
129 which will be defined as the appropriate types for 64-bit signed and
132 On LLP64 data model systems (notably 64-bit Windows), "int" and "long"
133 are 32 bits while "size_t" and "ptrdiff_t" are 64 bits. This means that
134 the following will generate a compiler warning:
137 i = strlen("hello, sailor"); /* Compiler warning */
139 Normally, you'd just make "i" a size_t. However, many GLib and Wireshark
140 functions won't accept a size_t on LLP64:
143 char greeting[] = "hello, sailor";
144 guint byte_after_greet;
146 i = strlen(greeting);
147 byte_after_greet = tvb_get_guint8(tvb, i); /* Compiler warning */
149 Try to use the appropriate data type when you can. When you can't, you
150 will have to cast to a compatible data type, e.g.
153 char greeting[] = "hello, sailor";
154 guint byte_after_greet;
156 i = strlen(greeting);
157 byte_after_greet = tvb_get_guint8(tvb, (gint) i); /* OK */
162 char greeting[] = "hello, sailor";
163 guint byte_after_greet;
165 i = (gint) strlen(greeting);
166 byte_after_greet = tvb_get_guint8(tvb, i); /* Compiler warning */
168 See http://www.unix.org/version2/whatsnew/lp64_wp.html for more
169 information on the sizes of common types in different data models.
171 When printing or displaying the values of 64-bit integral data types,
172 don't use "%lld", "%llu", "%llx", or "%llo" - not all platforms
173 support "%ll" for printing 64-bit integral data types. Instead, for
174 GLib routines, and routines that use them, such as all the routines in
175 Wireshark that take format arguments, use G_GINT64_MODIFIER, for example:
177 proto_tree_add_text(tree, tvb, offset, 8,
178 "Sequence Number: %" G_GINT64_MODIFIER "u",
181 When specifying an integral constant that doesn't fit in 32 bits, don't
182 use "LL" at the end of the constant - not all compilers use "LL" for
183 that. Instead, put the constant in a call to the "G_GINT64_CONSTANT()"
186 G_GINT64_CONSTANT(11644473600U)
192 Don't use a label without a statement following it. For example,
202 will not work with all compilers - you have to do
212 with some statement, even if it's a null statement, after the label.
214 Don't use "bzero()", "bcopy()", or "bcmp()"; instead, use the ANSI C
217 "memset()" (with zero as the second argument, so that it sets
218 all the bytes to zero);
220 "memcpy()" or "memmove()" (note that the first and second
221 arguments to "memcpy()" are in the reverse order to the
222 arguments to "bcopy()"; note also that "bcopy()" is typically
223 guaranteed to work on overlapping memory regions, while
224 "memcpy()" isn't, so if you may be copying from one region to a
225 region that overlaps it, use "memmove()", not "memcpy()" - but
226 "memcpy()" might be faster as a result of not guaranteeing
227 correct operation on overlapping memory regions);
229 and "memcmp()" (note that "memcmp()" returns 0, 1, or -1, doing
230 an ordered comparison, rather than just returning 0 for "equal"
231 and 1 for "not equal", as "bcmp()" does).
233 Not all platforms necessarily have "bzero()"/"bcopy()"/"bcmp()", and
234 those that do might not declare them in the header file on which they're
235 declared on your platform.
237 Don't use "index()" or "rindex()"; instead, use the ANSI C equivalents,
238 "strchr()" and "strrchr()". Not all platforms necessarily have
239 "index()" or "rindex()", and those that do might not declare them in the
240 header file on which they're declared on your platform.
242 Don't fetch data from packets by getting a pointer to data in the packet
243 with "tvb_get_ptr()", casting that pointer to a pointer to a structure,
244 and dereferencing that pointer. That pointer won't necessarily be aligned
245 on the proper boundary, which can cause crashes on some platforms (even
246 if it doesn't crash on an x86-based PC); furthermore, the data in a
247 packet is not necessarily in the byte order of the machine on which
248 Wireshark is running. Use the tvbuff routines to extract individual
249 items from the packet, or use "proto_tree_add_item()" and let it extract
252 Don't use structures that overlay packet data, or into which you copy
253 packet data; the C programming language does not guarantee any
254 particular alignment of fields within a structure, and even the
255 extensions that try to guarantee that are compiler-specific and not
256 necessarily supported by all compilers used to build Wireshark. Using
257 bitfields in those structures is even worse; the order of bitfields
260 Don't use "ntohs()", "ntohl()", "htons()", or "htonl()"; the header
261 files required to define or declare them differ between platforms, and
262 you might be able to get away with not including the appropriate header
263 file on your platform but that might not work on other platforms.
264 Instead, use "g_ntohs()", "g_ntohl()", "g_htons()", and "g_htonl()";
265 those are declared by <glib.h>, and you'll need to include that anyway,
266 as Wireshark header files that all dissectors must include use stuff from
269 Don't fetch a little-endian value using "tvb_get_ntohs() or
270 "tvb_get_ntohl()" and then using "g_ntohs()", "g_htons()", "g_ntohl()",
271 or "g_htonl()" on the resulting value - the g_ routines in question
272 convert between network byte order (big-endian) and *host* byte order,
273 not *little-endian* byte order; not all machines on which Wireshark runs
274 are little-endian, even though PCs are. Fetch those values using
275 "tvb_get_letohs()" and "tvb_get_letohl()".
277 Don't put a comma after the last element of an enum - some compilers may
278 either warn about it (producing extra noise) or refuse to accept it.
280 Don't include <unistd.h> without protecting it with
288 and, if you're including it to get routines such as "open()", "close()",
289 "read()", and "write()" declared, also include <io.h> if present:
295 in order to declare the Windows C library routines "_open()",
296 "_close()", "_read()", and "_write()". Your file must include <glib.h>
297 - which many of the Wireshark header files include, so you might not have
298 to include it explicitly - in order to get "open()", "close()",
299 "read()", "write()", etc. mapped to "_open()", "_close()", "_read()",
302 Do not use "open()", "rename()", "mkdir()", "stat()", "unlink()", "remove()",
303 "fopen()", "freopen()" directly. Instead use "ws_open()", "ws_rename()",
304 "ws_mkdir()", "ws_stat()", "ws_unlink()", "ws_remove()", "ws_fopen()",
305 "ws_freopen()": these wrapper functions change the path and file name from
306 UTF8 to UTF16 on Windows allowing the functions to work correctly when the
307 path or file name contain non-ASCII characters.
309 When opening a file with "ws_fopen()", "ws_freopen()", or "ws_fdopen()", if
310 the file contains ASCII text, use "r", "w", "a", and so on as the open mode
311 - but if it contains binary data, use "rb", "wb", and so on. On
312 Windows, if a file is opened in a text mode, writing a byte with the
313 value of octal 12 (newline) to the file causes two bytes, one with the
314 value octal 15 (carriage return) and one with the value octal 12, to be
315 written to the file, and causes bytes with the value octal 15 to be
316 discarded when reading the file (to translate between C's UNIX-style
317 lines that end with newline and Windows' DEC-style lines that end with
318 carriage return/line feed).
320 In addition, that also means that when opening or creating a binary
321 file, you must use "ws_open()" (with O_CREAT and possibly O_TRUNC if the
322 file is to be created if it doesn't exist), and OR in the O_BINARY flag.
323 That flag is not present on most, if not all, UNIX systems, so you must
330 to properly define it for UNIX (it's not necessary on UNIX).
332 Don't use forward declarations of static arrays without a specified size
333 in a fashion such as this:
335 static const value_string foo_vals[];
339 static const value_string foo_vals[] = {
346 as some compilers will reject the first of those statements. Instead,
347 initialize the array at the point at which it's first declared, so that
350 Don't put a comma after the last tuple of an initializer of an array.
352 For #define names and enum member names, prefix the names with a tag so
353 as to avoid collisions with other names - this might be more of an issue
354 on Windows, as it appears to #define names such as DELETE and
357 Don't use the "numbered argument" feature that many UNIX printf's
360 g_snprintf(add_string, 30, " - (%1$d) (0x%1$04x)", value);
362 as not all UNIX printf's implement it, and Windows printf doesn't appear
363 to implement it. Use something like
365 g_snprintf(add_string, 30, " - (%d) (0x%04x)", value, value);
369 Don't use "variadic macros", such as
371 #define DBG(format, args...) fprintf(stderr, format, ## args)
373 as not all C compilers support them. Use macros that take a fixed
374 number of arguments, such as
376 #define DBG0(format) fprintf(stderr, format)
377 #define DBG1(format, arg1) fprintf(stderr, format, arg1)
378 #define DBG2(format, arg1, arg2) fprintf(stderr, format, arg1, arg2)
384 #define DBG(args) printf args
390 as that's not supported by all compilers.
392 snprintf() -> g_snprintf()
393 snprintf() is not available on all platforms, so it's a good idea to use the
394 g_snprintf() function declared by <glib.h> instead.
396 tmpnam() -> mkstemp()
397 tmpnam is insecure and should not be used any more. Wireshark brings its
398 own mkstemp implementation for use on platforms that lack mkstemp.
399 Note: mkstemp does not accept NULL as a parameter.
401 The pointer returned by a call to "tvb_get_ptr()" is not guaranteed to be
402 aligned on any particular byte boundary; this means that you cannot
403 safely cast it to any data type other than a pointer to "char",
404 "unsigned char", "guint8", or other one-byte data types. You cannot,
405 for example, safely cast it to a pointer to a structure, and then access
406 the structure members directly; on some systems, unaligned accesses to
407 integral data types larger than 1 byte, and floating-point data types,
408 cause a trap, which will, at best, result in the OS slowly performing an
409 unaligned access for you, and will, on at least some platforms, cause
410 the program to be terminated.
412 Wireshark supports platforms with GLib 2.4[.x]/GTK+ 2.4[.x] or newer.
413 If a Glib/GTK+ mechanism is available only in Glib/GTK+ versions
414 newer than 2.4/2.4 then use "#if GTK_CHECK_VERSION(...)" to conditionally
415 compile code using that mechanism.
417 When different code must be used on UN*X and Win32, use a #if or #ifdef
418 that tests _WIN32, not WIN32. Try to write code portably whenever
419 possible, however; note that there are some routines in Wireshark with
420 platform-dependent implementations and platform-independent APIs, such
421 as the routines in epan/filesystem.c, allowing the code that calls it to
422 be written portably without #ifdefs.
424 1.1.2 String handling
426 Do not use functions such as strcat() or strcpy().
427 A lot of work has been done to remove the existing calls to these functions and
428 we do not want any new callers of these functions.
430 Instead use g_snprintf() since that function will if used correctly prevent
431 buffer overflows for large strings.
433 When using a buffer to create a string, do not use a buffer stored on the stack.
434 I.e. do not use a buffer declared as
438 instead allocate a buffer dynamically using the string-specific or plain emem
439 routines (see README.malloc) such as
441 emem_strbuf_t *strbuf;
442 strbuf = ep_strbuf_new_label("");
443 ep_strbuf_append_printf(strbuf, ...
449 #define MAX_BUFFER 1024
450 buffer=ep_alloc(MAX_BUFFER);
453 g_snprintf(buffer, MAX_BUFFER, ...
455 This avoids the stack from being corrupted in case there is a bug in your code
456 that accidentally writes beyond the end of the buffer.
459 If you write a routine that will create and return a pointer to a filled in
460 string and if that buffer will not be further processed or appended to after
461 the routine returns (except being added to the proto tree),
462 do not preallocate the buffer to fill in and pass as a parameter instead
463 pass a pointer to a pointer to the function and return a pointer to an
464 emem allocated buffer that will be automatically freed. (see README.malloc)
466 I.e. do not write code such as
468 foo_to_str(char *string, ... ){
474 foo_to_str(buffer, ...
475 proto_tree_add_text(... buffer ...
477 instead write the code as
479 foo_to_str(char **buffer, ...
481 *buffer=ep_alloc(MAX_BUFFER);
487 foo_to_str(&buffer, ...
488 proto_tree_add_text(... *buffer ...
490 Use ep_ allocated buffers. They are very fast and nice. These buffers are all
491 automatically free()d when the dissection of the current packet ends so you
492 don't have to worry about free()ing them explicitly in order to not leak memory.
493 Please read README.malloc.
495 Don't use non-ASCII characters in source files; not all compiler
496 environments will be using the same encoding for non-ASCII characters,
497 and at least one compiler (Microsoft's Visual C) will, in environments
498 with double-byte character encodings, such as many Asian environments,
499 fail if it sees a byte sequence in a source file that doesn't correspond
500 to a valid character. This causes source files using either an ISO
501 8859/n single-byte character encoding or UTF-8 to fail to compile. Even
502 if the compiler doesn't fail, there is no guarantee that the compiler,
503 or a developer's text editor, will interpret the characters the way you
504 intend them to be interpreted.
508 Wireshark is not guaranteed to read only network traces that contain correctly-
509 formed packets. Wireshark is commonly used to track down networking
510 problems, and the problems might be due to a buggy protocol implementation
511 sending out bad packets.
513 Therefore, protocol dissectors not only have to be able to handle
514 correctly-formed packets without, for example, crashing or looping
515 infinitely, they also have to be able to handle *incorrectly*-formed
516 packets without crashing or looping infinitely.
518 Here are some suggestions for making dissectors more robust in the face
519 of incorrectly-formed packets:
521 Do *NOT* use "g_assert()" or "g_assert_not_reached()" in dissectors.
522 *NO* value in a packet's data should be considered "wrong" in the sense
523 that it's a problem with the dissector if found; if it cannot do
524 anything else with a particular value from a packet's data, the
525 dissector should put into the protocol tree an indication that the
526 value is invalid, and should return. The "expert" mechanism should be
527 used for that purpose.
529 If there is a case where you are checking not for an invalid data item
530 in the packet, but for a bug in the dissector (for example, an
531 assumption being made at a particular point in the code about the
532 internal state of the dissector), use the DISSECTOR_ASSERT macro for
533 that purpose; this will put into the protocol tree an indication that
534 the dissector has a bug in it, and will not crash the application.
536 If you are allocating a chunk of memory to contain data from a packet,
537 or to contain information derived from data in a packet, and the size of
538 the chunk of memory is derived from a size field in the packet, make
539 sure all the data is present in the packet before allocating the buffer.
542 1) Wireshark won't leak that chunk of memory if an attempt to
543 fetch data not present in the packet throws an exception.
547 2) it won't crash trying to allocate an absurdly-large chunk of
548 memory if the size field has a bogus large value.
550 If you're fetching into such a chunk of memory a string from the buffer,
551 and the string has a specified size, you can use "tvb_get_*_string()",
552 which will check whether the entire string is present before allocating
553 a buffer for the string, and will also put a trailing '\0' at the end of
556 If you're fetching into such a chunk of memory a 2-byte Unicode string
557 from the buffer, and the string has a specified size, you can use
558 "tvb_get_ephemeral_faked_unicode()", which will check whether the entire
559 string is present before allocating a buffer for the string, and will also
560 put a trailing '\0' at the end of the buffer. The resulting string will be
561 a sequence of single-byte characters; the only Unicode characters that
562 will be handled correctly are those in the ASCII range. (Wireshark's
563 ability to handle non-ASCII strings is limited; it needs to be
566 If you're fetching into such a chunk of memory a sequence of bytes from
567 the buffer, and the sequence has a specified size, you can use
568 "tvb_memdup()", which will check whether the entire sequence is present
569 before allocating a buffer for it.
571 Otherwise, you can check whether the data is present by using
572 "tvb_ensure_bytes_exist()" or by getting a pointer to the data by using
573 "tvb_get_ptr()", although note that there might be problems with using
574 the pointer from "tvb_get_ptr()" (see the item on this in the
575 Portability section above, and the next item below).
577 Note also that you should only fetch string data into a fixed-length
578 buffer if the code ensures that no more bytes than will fit into the
579 buffer are fetched ("the protocol ensures" isn't good enough, as
580 protocol specifications can't ensure only packets that conform to the
581 specification will be transmitted or that only packets for the protocol
582 in question will be interpreted as packets for that protocol by
583 Wireshark). If there's no maximum length of string data to be fetched,
584 routines such as "tvb_get_*_string()" are safer, as they allocate a buffer
585 large enough to hold the string. (Note that some variants of this call
586 require you to free the string once you're finished with it.)
588 If you have gotten a pointer using "tvb_get_ptr()", you must make sure
589 that you do not refer to any data past the length passed as the last
590 argument to "tvb_get_ptr()"; while the various "tvb_get" routines
591 perform bounds checking and throw an exception if you refer to data not
592 available in the tvbuff, direct references through a pointer gotten from
593 "tvb_get_ptr()" do not do any bounds checking.
595 If you have a loop that dissects a sequence of items, each of which has
596 a length field, with the offset in the tvbuff advanced by the length of
597 the item, then, if the length field is the total length of the item, and
598 thus can be zero, you *MUST* check for a zero-length item and abort the
599 loop if you see one. Otherwise, a zero-length item could cause the
600 dissector to loop infinitely. You should also check that the offset,
601 after having the length added to it, is greater than the offset before
602 the length was added to it, if the length field is greater than 24 bits
603 long, so that, if the length value is *very* large and adding it to the
604 offset causes an overflow, that overflow is detected.
606 If you are fetching a length field from the buffer, corresponding to the
607 length of a portion of the packet, and subtracting from that length a
608 value corresponding to the length of, for example, a header in the
609 packet portion in question, *ALWAYS* check that the value of the length
610 field is greater than or equal to the length you're subtracting from it,
611 and report an error in the packet and stop dissecting the packet if it's
612 less than the length you're subtracting from it. Otherwise, the
613 resulting length value will be negative, which will either cause errors
614 in the dissector or routines called by the dissector, or, if the value
615 is interpreted as an unsigned integer, will cause the value to be
616 interpreted as a very large positive value.
618 Any tvbuff offset that is added to as processing is done on a packet
619 should be stored in a 32-bit variable, such as an "int"; if you store it
620 in an 8-bit or 16-bit variable, you run the risk of the variable
623 sprintf() -> g_snprintf()
624 Prevent yourself from using the sprintf() function, as it does not test the
625 length of the given output buffer and might be writing into unintended memory
626 areas. This function is one of the main causes of security problems like buffer
627 exploits and many other bugs that are very hard to find. It's much better to
628 use the g_snprintf() function declared by <glib.h> instead.
630 You should test your dissector against incorrectly-formed packets. This
631 can be done using the randpkt and editcap utilities that come with the
632 Wireshark distribution. Testing using randpkt can be done by generating
633 output at the same layer as your protocol, and forcing Wireshark/TShark
634 to decode it as your protocol, e.g. if your protocol sits on top of UDP:
636 randpkt -c 50000 -t dns randpkt.pcap
637 tshark -nVr randpkt.pcap -d udp.port==53,<myproto>
639 Testing using editcap can be done using preexisting capture files and the
640 "-E" flag, which introduces errors in a capture file. E.g.:
642 editcap -E 0.03 infile.pcap outfile.pcap
643 tshark -nVr outfile.pcap
645 The script fuzz-test.sh is available to help automate these tests.
647 1.1.4 Name convention.
649 Wireshark uses the underscore_convention rather than the InterCapConvention for
650 function names, so new code should probably use underscores rather than
651 intercaps for functions and variable names. This is especially important if you
652 are writing code that will be called from outside your code. We are just
653 trying to keep things consistent for other developers.
655 1.1.5 White space convention.
657 Avoid using tab expansions different from 8 column widths, as not all
658 text editors in use by the developers support this. For a detailed
659 discussion of tabs, spaces, and indentation, see
661 http://www.jwz.org/doc/tabs-vs-spaces.html
663 When creating a new file, you are free to choose an indentation logic.
664 Most of the files in Wireshark tend to use 2-space or 4-space
665 indentation. You are encouraged to write a short comment on the
666 indentation logic at the beginning of this new file, especially if
667 you're using non-mod-8 tabs. The tabs-vs-spaces document above provides
668 examples of Emacs and vi modelines for this purpose.
670 When editing an existing file, try following the existing indentation
671 logic and even if it very tempting, never ever use a restyler/reindenter
672 utility on an existing file. If you run across wildly varying
673 indentation styles within the same file, it might be helpful to send a
674 note to wireshark-dev for guidance.
676 1.1.6 Compiler warnings
678 You should write code that is free of compiler warnings. Such warnings will
679 often indicate questionable code and sometimes even real bugs, so it's best
680 to avoid warnings at all.
682 The compiler flags in the Makefiles are set to "treat warnings as errors",
683 so your code won't even compile when warnings occur.
687 Wireshark requires certain things when setting up a protocol dissector.
688 Below is skeleton code for a dissector that you can copy to a file and
689 fill in. Your dissector should follow the naming convention of packet-
690 followed by the abbreviated name for the protocol. It is recommended
691 that where possible you keep to the IANA abbreviated name for the
692 protocol, if there is one, or a commonly-used abbreviation for the
695 Usually, you will put your newly created dissector file into the directory
696 epan/dissectors, just like all the other packet-....c files already in there.
698 Also, please add your dissector file to the corresponding makefile,
699 described in section "1.9 Editing Makefile.common to add your dissector" below.
701 Dissectors that use the dissector registration to register with a lower level
702 dissector don't need to define a prototype in the .h file. For other
703 dissectors the main dissector routine should have a prototype in a header
704 file whose name is "packet-", followed by the abbreviated name for the
705 protocol, followed by ".h"; any dissector file that calls your dissector
706 should be changed to include that file.
708 You may not need to include all the headers listed in the skeleton
709 below, and you may need to include additional headers. For example, the
718 is needed only if you are using a function from libpcre, e.g. the
719 "pcre_compile()" function.
721 The "$Id$" in the comment will be updated by Subversion when the file is
724 When creating a new file, it is fine to just write "$Id$" as Subversion will
725 automatically fill in the identifier at the time the file will be added to the
726 SVN repository (committed).
728 ------------------------------------Cut here------------------------------------
729 /* packet-PROTOABBREV.c
730 * Routines for PROTONAME dissection
731 * Copyright 200x, YOUR_NAME <YOUR_EMAIL_ADDRESS>
735 * Wireshark - Network traffic analyzer
736 * By Gerald Combs <gerald@wireshark.org>
737 * Copyright 1998 Gerald Combs
739 * Copied from WHATEVER_FILE_YOU_USED (where "WHATEVER_FILE_YOU_USED"
740 * is a dissector file; if you just copied this from README.developer,
741 * don't bother with the "Copied from" - you don't even need to put
742 * in a "Copied from" if you copied an existing dissector, especially
743 * if the bulk of the code in the new dissector is your code)
745 * This program is free software; you can redistribute it and/or modify
746 * it under the terms of the GNU General Public License as published by
747 * the Free Software Foundation; either version 2 of the License, or
748 * (at your option) any later version.
750 * This program is distributed in the hope that it will be useful,
751 * but WITHOUT ANY WARRANTY; without even the implied warranty of
752 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
753 * GNU General Public License for more details.
755 * You should have received a copy of the GNU General Public License along
756 * with this program; if not, write to the Free Software Foundation, Inc.,
757 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
770 #include <epan/packet.h>
771 #include <epan/prefs.h>
773 /* IF PROTO exposes code to other dissectors, then it must be exported
774 in a header file. If not, a header file is not needed at all. */
775 #include "packet-PROTOABBREV.h"
777 /* Forward declaration we need below (if using proto_reg_handoff...
778 as a prefs callback) */
779 void proto_reg_handoff_PROTOABBREV(void);
781 /* Initialize the protocol and registered fields */
782 static int proto_PROTOABBREV = -1;
783 static int hf_PROTOABBREV_FIELDABBREV = -1;
785 /* Global sample preference ("controls" display of numbers) */
786 static gboolean gPREF_HEX = FALSE;
787 /* Global sample port pref */
788 static guint gPORT_PREF = 1234;
790 /* Initialize the subtree pointers */
791 static gint ett_PROTOABBREV = -1;
793 /* Code to actually dissect the packets */
795 dissect_PROTOABBREV(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
798 /* Set up structures needed to add the protocol subtree and manage it */
800 proto_tree *PROTOABBREV_tree;
802 /* First, if at all possible, do some heuristics to check if the packet cannot
803 * possibly belong to your protocol. This is especially important for
804 * protocols directly on top of TCP or UDP where port collisions are
805 * common place (e.g., even though your protocol uses a well known port,
806 * someone else may set up, for example, a web server on that port which,
807 * if someone analyzed that web server's traffic in Wireshark, would result
808 * in Wireshark handing an HTTP packet to your dissector). For example:
810 /* Check that there's enough data */
811 if (tvb_length(tvb) < /* your protocol's smallest packet size */)
814 /* Get some values from the packet header, probably using tvb_get_*() */
815 if ( /* these values are not possible in PROTONAME */ )
816 /* This packet does not appear to belong to PROTONAME.
817 * Return 0 to give another dissector a chance to dissect it.
821 /* Make entries in Protocol column and Info column on summary display */
822 col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
824 /* This field shows up as the "Info" column in the display; you should use
825 it, if possible, to summarize what's in the packet, so that a user looking
826 at the list of packets can tell what type of packet it is. See section 1.5
827 for more information.
829 If you are setting the column to a constant string, use "col_set_str()",
830 as it's more efficient than the other "col_set_XXX()" calls.
832 If you're setting it to a string you've constructed, or will be
833 appending to the column later, use "col_add_str()".
835 "col_add_fstr()" can be used instead of "col_add_str()"; it takes
836 "printf()"-like arguments. Don't use "col_add_fstr()" with a format
837 string of "%s" - just use "col_add_str()" or "col_set_str()", as it's
838 more efficient than "col_add_fstr()".
840 If you will be fetching any data from the packet before filling in
841 the Info column, clear that column first, in case the calls to fetch
842 data from the packet throw an exception because they're fetching data
843 past the end of the packet, so that the Info column doesn't have data
844 left over from the previous dissector; do
846 col_clear(pinfo->cinfo, COL_INFO);
850 col_set_str(pinfo->cinfo, COL_INFO, "XXX Request");
852 /* A protocol dissector can be called in 2 different ways:
854 (a) Operational dissection
856 In this mode, Wireshark is only interested in the way protocols
857 interact, protocol conversations are created, packets are
858 reassembled and handed over to higher-level protocol dissectors.
859 In this mode Wireshark does not build a so-called "protocol
862 (b) Detailed dissection
864 In this mode, Wireshark is also interested in all details of
865 a given protocol, so a "protocol tree" is created.
867 Wireshark distinguishes between the 2 modes with the proto_tree pointer:
871 In the interest of speed, if "tree" is NULL, avoid building a
872 protocol tree and adding stuff to it, or even looking at any packet
873 data needed only if you're building the protocol tree, if possible.
875 Note, however, that you must fill in column information, create
876 conversations, reassemble packets, build any other persistent state
877 needed for dissection, and call subdissectors regardless of whether
878 "tree" is NULL or not. This might be inconvenient to do without
879 doing most of the dissection work; the routines for adding items to
880 the protocol tree can be passed a null protocol tree pointer, in
881 which case they'll return a null item pointer, and
882 "proto_item_add_subtree()" returns a null tree pointer if passed a
883 null item pointer, so, if you're careful not to dereference any null
884 tree or item pointers, you can accomplish this by doing all the
885 dissection work. This might not be as efficient as skipping that
886 work if you're not building a protocol tree, but if the code would
887 have a lot of tests whether "tree" is null if you skipped that work,
888 you might still be better off just doing all that work regardless of
889 whether "tree" is null or not. */
892 /* NOTE: The offset and length values in the call to
893 "proto_tree_add_item()" define what data bytes to highlight in the hex
894 display window when the line in the protocol tree display
895 corresponding to that item is selected.
897 Supplying a length of -1 is the way to highlight all data from the
898 offset to the end of the packet. */
900 /* create display subtree for the protocol */
901 ti = proto_tree_add_item(tree, proto_PROTOABBREV, tvb, 0, -1, FALSE);
903 PROTOABBREV_tree = proto_item_add_subtree(ti, ett_PROTOABBREV);
905 /* add an item to the subtree, see section 1.6 for more information */
906 proto_tree_add_item(PROTOABBREV_tree,
907 hf_PROTOABBREV_FIELDABBREV, tvb, offset, len, FALSE);
910 /* Continue adding tree items to process the packet here */
915 /* If this protocol has a sub-dissector call it here, see section 1.8 */
917 /* Return the amount of data this dissector was able to dissect */
918 return tvb_length(tvb);
922 /* Register the protocol with Wireshark */
924 /* this format is require because a script is used to build the C function
925 that calls all the protocol registration.
929 proto_register_PROTOABBREV(void)
931 module_t *PROTOABBREV_module;
933 /* Setup list of header fields See Section 1.6.1 for details*/
934 static hf_register_info hf[] = {
935 { &hf_PROTOABBREV_FIELDABBREV,
936 { "FIELDNAME", "PROTOABBREV.FIELDABBREV",
937 FIELDTYPE, FIELDBASE, FIELDCONVERT, BITMASK,
938 "FIELDDESCR", HFILL }
942 /* Setup protocol subtree array */
943 static gint *ett[] = {
947 /* Register the protocol name and description */
948 proto_PROTOABBREV = proto_register_protocol("PROTONAME",
949 "PROTOSHORTNAME", "PROTOABBREV");
951 /* Required function calls to register the header fields and subtrees used */
952 proto_register_field_array(proto_PROTOABBREV, hf, array_length(hf));
953 proto_register_subtree_array(ett, array_length(ett));
955 /* Register preferences module (See Section 2.6 for more on preferences) */
956 /* (Registration of a prefs callback is not required if there are no */
957 /* prefs-dependent registration functions (eg: a port pref). */
958 /* See proto_reg_handoff below. */
959 /* If a prefs callback is not needed, use NULL instead of */
960 /* proto_reg_handoff_PROTOABBREV in the following). */
961 PROTOABBREV_module = prefs_register_protocol(proto_PROTOABBREV,
962 proto_reg_handoff_PROTOABBREV);
964 /* Register a sample preference */
965 prefs_register_bool_preference(PROTOABBREV_module, "show_hex",
966 "Display numbers in Hex",
967 "Enable to display numerical values in hexadecimal.",
970 /* Register a sample port preference */
971 prefs_register_uint_preference(PROTOABBREV_module, "tcp.port", "PROTOABBREV TCP Port",
972 " PROTOABBREV TCP port if other than the default",
977 /* If this dissector uses sub-dissector registration add a registration routine.
978 This exact format is required because a script is used to find these
979 routines and create the code that calls these routines.
981 If this function is registered as a prefs callback (see prefs_register_protocol
982 above) this function is also called by preferences whenever "Apply" is pressed;
983 In that case, it should accommodate being called more than once.
985 This form of the reg_handoff function is used if if you perform
986 registration functions which are dependent upon prefs. See below
987 for a simpler form which can be used if there are no
988 prefs-dependent registration functions.
991 proto_reg_handoff_PROTOABBREV(void)
993 static gboolean initialized = FALSE;
994 static dissector_handle_t PROTOABBREV_handle;
995 static int currentPort;
999 /* Use new_create_dissector_handle() to indicate that dissect_PROTOABBREV()
1000 * returns the number of bytes it dissected (or 0 if it thinks the packet
1001 * does not belong to PROTONAME).
1003 PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV,
1005 dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
1011 If you perform registration functions which are dependent upon
1012 prefs the you should de-register everything which was associated
1013 with the previous settings and re-register using the new prefs
1014 settings here. In general this means you need to keep track of
1015 the PROTOABBREV_handle and the value the preference had at the time
1016 you registered. The PROTOABBREV_handle value and the value of the
1017 preference can be saved using local statics in this
1018 function (proto_reg_handoff).
1021 dissector_delete("tcp.port", currentPort, PROTOABBREV_handle);
1024 currentPort = gPORT_PREF;
1026 dissector_add("tcp.port", currentPort, PROTOABBREV_handle);
1031 /* Simple form of proto_reg_handoff_PROTOABBREV which can be used if there are
1032 no prefs-dependent registration function calls.
1036 proto_reg_handoff_PROTOABBREV(void)
1038 dissector_handle_t PROTOABBREV_handle;
1040 /* Use new_create_dissector_handle() to indicate that dissect_PROTOABBREV()
1041 * returns the number of bytes it dissected (or 0 if it thinks the packet
1042 * does not belong to PROTONAME).
1044 PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV,
1046 dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
1051 ------------------------------------Cut here------------------------------------
1053 1.3 Explanation of needed substitutions in code skeleton.
1055 In the above code block the following strings should be substituted with
1058 YOUR_NAME Your name, of course. You do want credit, don't you?
1059 It's the only payment you will receive....
1060 YOUR_EMAIL_ADDRESS Keep those cards and letters coming.
1061 WHATEVER_FILE_YOU_USED Add this line if you are using another file as a
1063 PROTONAME The name of the protocol; this is displayed in the
1064 top-level protocol tree item for that protocol.
1065 PROTOSHORTNAME An abbreviated name for the protocol; this is displayed
1066 in the "Preferences" dialog box if your dissector has
1067 any preferences, in the dialog box of enabled protocols,
1068 and in the dialog box for filter fields when constructing
1069 a filter expression.
1070 PROTOABBREV A name for the protocol for use in filter expressions;
1071 it shall contain only lower-case letters, digits, and
1073 FIELDNAME The displayed name for the header field.
1074 FIELDABBREV The abbreviated name for the header field. (NO SPACES)
1075 FIELDTYPE FT_NONE, FT_BOOLEAN, FT_UINT8, FT_UINT16, FT_UINT24,
1076 FT_UINT32, FT_UINT64, FT_INT8, FT_INT16, FT_INT24, FT_INT32,
1077 FT_INT64, FT_FLOAT, FT_DOUBLE, FT_ABSOLUTE_TIME,
1078 FT_RELATIVE_TIME, FT_STRING, FT_STRINGZ, FT_EBCDIC,
1079 FT_UINT_STRING, FT_ETHER, FT_BYTES, FT_UINT_BYTES, FT_IPv4,
1080 FT_IPv6, FT_IPXNET, FT_FRAMENUM, FT_PROTOCOL, FT_GUID, FT_OID
1081 FIELDBASE BASE_NONE, BASE_DEC, BASE_HEX, BASE_OCT, BASE_DEC_HEX,
1082 BASE_HEX_DEC, BASE_RANGE_STRING, BASE_CUSTOM
1083 FIELDCONVERT VALS(x), RVALS(x), TFS(x), NULL
1084 BITMASK Usually 0x0 unless using the TFS(x) field conversion.
1085 FIELDDESCR A brief description of the field, or NULL.
1086 PARENT_SUBFIELD Lower level protocol field used for lookup, i.e. "tcp.port"
1087 ID_VALUE Lower level protocol field value that identifies this protocol
1088 For example the TCP or UDP port number
1090 If, for example, PROTONAME is "Internet Bogosity Discovery Protocol",
1091 PROTOSHORTNAME would be "IBDP", and PROTOABBREV would be "ibdp". Try to
1092 conform with IANA names.
1094 1.4 The dissector and the data it receives.
1099 This is only needed if the dissector doesn't use self-registration to
1100 register itself with the lower level dissector, or if the protocol dissector
1101 wants/needs to expose code to other subdissectors.
1103 The dissector must be declared exactly as follows in the file
1104 packet-PROTOABBREV.h:
1107 dissect_PROTOABBREV(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);
1110 1.4.2 Extracting data from packets.
1112 NOTE: See the file /epan/tvbuff.h for more details.
1114 The "tvb" argument to a dissector points to a buffer containing the raw
1115 data to be analyzed by the dissector; for example, for a protocol
1116 running atop UDP, it contains the UDP payload (but not the UDP header,
1117 or any protocol headers above it). A tvbuffer is an opaque data
1118 structure, the internal data structures are hidden and the data must be
1119 accessed via the tvbuffer accessors.
1123 Bit accessors for a maximum of 8-bits, 16-bits 32-bits and 64-bits:
1125 guint8 tvb_get_bits8(tvbuff_t *tvb, gint bit_offset, gint no_of_bits);
1126 guint16 tvb_get_bits16(tvbuff_t *tvb, gint bit_offset, gint no_of_bits,gboolean little_endian);
1127 guint32 tvb_get_bits32(tvbuff_t *tvb, gint bit_offset, gint no_of_bits,gboolean little_endian);
1128 guint64 tvb_get_bits64(tvbuff_t *tvb, gint bit_offset, gint no_of_bits,gboolean little_endian);
1130 Single-byte accessor:
1132 guint8 tvb_get_guint8(tvbuff_t*, gint offset);
1134 Network-to-host-order accessors for 16-bit integers (guint16), 24-bit
1135 integers, 32-bit integers (guint32), and 64-bit integers (guint64):
1137 guint16 tvb_get_ntohs(tvbuff_t*, gint offset);
1138 guint32 tvb_get_ntoh24(tvbuff_t*, gint offset);
1139 guint32 tvb_get_ntohl(tvbuff_t*, gint offset);
1140 guint64 tvb_get_ntoh64(tvbuff_t*, gint offset);
1142 Network-to-host-order accessors for single-precision and
1143 double-precision IEEE floating-point numbers:
1145 gfloat tvb_get_ntohieee_float(tvbuff_t*, gint offset);
1146 gdouble tvb_get_ntohieee_double(tvbuff_t*, gint offset);
1148 Little-Endian-to-host-order accessors for 16-bit integers (guint16),
1149 24-bit integers, 32-bit integers (guint32), and 64-bit integers
1152 guint16 tvb_get_letohs(tvbuff_t*, gint offset);
1153 guint32 tvb_get_letoh24(tvbuff_t*, gint offset);
1154 guint32 tvb_get_letohl(tvbuff_t*, gint offset);
1155 guint64 tvb_get_letoh64(tvbuff_t*, gint offset);
1157 Little-Endian-to-host-order accessors for single-precision and
1158 double-precision IEEE floating-point numbers:
1160 gfloat tvb_get_letohieee_float(tvbuff_t*, gint offset);
1161 gdouble tvb_get_letohieee_double(tvbuff_t*, gint offset);
1163 Accessors for IPv4 and IPv6 addresses:
1165 guint32 tvb_get_ipv4(tvbuff_t*, gint offset);
1166 void tvb_get_ipv6(tvbuff_t*, gint offset, struct e_in6_addr *addr);
1168 NOTE: IPv4 addresses are not to be converted to host byte order before
1169 being passed to "proto_tree_add_ipv4()". You should use "tvb_get_ipv4()"
1170 to fetch them, not "tvb_get_ntohl()" *OR* "tvb_get_letohl()" - don't,
1171 for example, try to use "tvb_get_ntohl()", find that it gives you the
1172 wrong answer on the PC on which you're doing development, and try
1173 "tvb_get_letohl()" instead, as "tvb_get_letohl()" will give the wrong
1174 answer on big-endian machines.
1178 void tvb_get_ntohguid(tvbuff_t *, gint offset, e_guid_t *guid);
1179 void tvb_get_letohguid(tvbuff_t *, gint offset, e_guid_t *guid);
1183 guint8 *tvb_get_string(tvbuff_t*, gint offset, gint length);
1184 guint8 *tvb_get_ephemeral_string(tvbuff_t*, gint offset, gint length);
1185 guint8 *tvb_get_seasonal_string(tvbuff_t*, gint offset, gint length);
1187 Returns a null-terminated buffer containing data from the specified
1188 tvbuff, starting at the specified offset, and containing the specified
1189 length worth of characters (the length of the buffer will be length+1,
1190 as it includes a null character to terminate the string).
1192 tvb_get_string() returns a buffer allocated by g_malloc() so you must
1193 g_free() it when you are finished with the string. Failure to g_free() this
1194 buffer will lead to memory leaks.
1196 tvb_get_ephemeral_string() returns a buffer allocated from a special heap
1197 with a lifetime until the next packet is dissected. You do not need to
1198 free() this buffer, it will happen automatically once the next packet is
1201 tvb_get_seasonal_string() returns a buffer allocated from a special heap
1202 with a lifetime of the current capture session. You do not need to
1203 free() this buffer, it will happen automatically once the a new capture or
1206 guint8 *tvb_get_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
1207 guint8 *tvb_get_ephemeral_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
1208 guint8 *tvb_get_seasonal_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
1210 Returns a null-terminated buffer, allocated with "g_malloc()",
1211 containing data from the specified tvbuff, starting at the
1212 specified offset, and containing all characters from the tvbuff up to
1213 and including a terminating null character in the tvbuff. "*lengthp"
1214 will be set to the length of the string, including the terminating null.
1216 tvb_get_stringz() returns a buffer allocated by g_malloc() so you must
1217 g_free() it when you are finished with the string. Failure to g_free() this
1218 buffer will lead to memory leaks.
1219 tvb_get_ephemeral_stringz() returns a buffer allocated from a special heap
1220 with a lifetime until the next packet is dissected. You do not need to
1221 free() this buffer, it will happen automatically once the next packet is
1224 tvb_get_seasonal_stringz() returns a buffer allocated from a special heap
1225 with a lifetime of the current capture session. You do not need to
1226 free() this buffer, it will happen automatically once the a new capture or
1229 guint8 *tvb_fake_unicode(tvbuff_t*, gint offset, gint length, gboolean little_endian);
1230 guint8 *tvb_get_ephemeral_faked_unicode(tvbuff_t*, gint offset, gint length, gboolean little_endian);
1232 Converts a 2-byte unicode string to an ASCII string.
1233 Returns a null-terminated buffer containing data from the specified
1234 tvbuff, starting at the specified offset, and containing the specified
1235 length worth of characters (the length of the buffer will be length+1,
1236 as it includes a null character to terminate the string).
1238 tvb_fake_unicode() returns a buffer allocated by g_malloc() so you must
1239 g_free() it when you are finished with the string. Failure to g_free() this
1240 buffer will lead to memory leaks.
1241 tvb_get_ephemeral_faked_unicode() returns a buffer allocated from a special
1242 heap with a lifetime until the next packet is dissected. You do not need to
1243 free() this buffer, it will happen automatically once the next packet is
1246 Byte Array Accessors:
1248 gchar *tvb_bytes_to_str(tvbuff_t *tvb, gint offset, gint len);
1250 Formats a bunch of data from a tvbuff as bytes, returning a pointer
1251 to the string with the data formatted as two hex digits for each byte.
1252 The string pointed to is stored in an "ep_alloc'd" buffer which will be freed
1253 before the next frame is dissected. The formatted string will contain the hex digits
1254 for at most the first 16 bytes of the data. If len is greater than 16 bytes, a
1255 trailing "..." will be added to the string.
1257 gchar *tvb_bytes_to_str_punct(tvbuff_t *tvb, gint offset, gint len, gchar punct);
1259 This function is similar to tvb_bytes_to_str(...) except that 'punct' is inserted
1260 between the hex representation of each byte.
1264 guint8* tvb_memcpy(tvbuff_t*, guint8* target, gint offset, gint length);
1266 Copies into the specified target the specified length's worth of data
1267 from the specified tvbuff, starting at the specified offset.
1269 guint8* tvb_memdup(tvbuff_t*, gint offset, gint length);
1270 guint8* ep_tvb_memdup(tvbuff_t*, gint offset, gint length);
1272 Returns a buffer, allocated with "g_malloc()", containing the specified
1273 length's worth of data from the specified tvbuff, starting at the
1274 specified offset. The ephemeral variant is freed automatically after the
1275 packet is dissected.
1278 /* WARNING! This function is possibly expensive, temporarily allocating
1279 * another copy of the packet data. Furthermore, it's dangerous because once
1280 * this pointer is given to the user, there's no guarantee that the user will
1281 * honor the 'length' and not overstep the boundaries of the buffer.
1283 guint8* tvb_get_ptr(tvbuff_t*, gint offset, gint length);
1285 The reason that tvb_get_ptr() might have to allocate a copy of its data
1286 only occurs with TVBUFF_COMPOSITES, data that spans multiple tvbuffers.
1287 If the user requests a pointer to a range of bytes that span the member
1288 tvbuffs that make up the TVBUFF_COMPOSITE, the data will have to be
1289 copied to another memory region to assure that all the bytes are
1294 1.5 Functions to handle columns in the traffic summary window.
1296 The topmost pane of the main window is a list of the packets in the
1297 capture, possibly filtered by a display filter.
1299 Each line corresponds to a packet, and has one or more columns, as
1300 configured by the user.
1302 Many of the columns are handled by code outside individual dissectors;
1303 most dissectors need only specify the value to put in the "Protocol" and
1306 Columns are specified by COL_ values; the COL_ value for the "Protocol"
1307 field, typically giving an abbreviated name for the protocol (but not
1308 the all-lower-case abbreviation used elsewhere) is COL_PROTOCOL, and the
1309 COL_ value for the "Info" field, giving a summary of the contents of the
1310 packet for that protocol, is COL_INFO.
1312 The value for a column can be specified with one of several functions,
1313 all of which take the 'fd' argument to the dissector as their first
1314 argument, and the COL_ value for the column as their second argument.
1316 1.5.1 The col_set_str function.
1318 'col_set_str' takes a string as its third argument, and sets the value
1319 for the column to that value. It assumes that the pointer passed to it
1320 points to a string constant or a static "const" array, not to a
1321 variable, as it doesn't copy the string, it merely saves the pointer
1322 value; the argument can itself be a variable, as long as it always
1323 points to a string constant or a static "const" array.
1325 It is more efficient than 'col_add_str' or 'col_add_fstr'; however, if
1326 the dissector will be using 'col_append_str' or 'col_append_fstr" to
1327 append more information to the column, the string will have to be copied
1328 anyway, so it's best to use 'col_add_str' rather than 'col_set_str' in
1331 For example, to set the "Protocol" column
1334 col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
1337 1.5.2 The col_add_str function.
1339 'col_add_str' takes a string as its third argument, and sets the value
1340 for the column to that value. It takes the same arguments as
1341 'col_set_str', but copies the string, so that if the string is, for
1342 example, an automatic variable that won't remain in scope when the
1343 dissector returns, it's safe to use.
1346 1.5.3 The col_add_fstr function.
1348 'col_add_fstr' takes a 'printf'-style format string as its third
1349 argument, and 'printf'-style arguments corresponding to '%' format
1350 items in that string as its subsequent arguments. For example, to set
1351 the "Info" field to "<XXX> request, <N> bytes", where "reqtype" is a
1352 string containing the type of the request in the packet and "n" is an
1353 unsigned integer containing the number of bytes in the request:
1355 col_add_fstr(pinfo->cinfo, COL_INFO, "%s request, %u bytes",
1358 Don't use 'col_add_fstr' with a format argument of just "%s" -
1359 'col_add_str', or possibly even 'col_set_str' if the string that matches
1360 the "%s" is a static constant string, will do the same job more
1364 1.5.4 The col_clear function.
1366 If the Info column will be filled with information from the packet, that
1367 means that some data will be fetched from the packet before the Info
1368 column is filled in. If the packet is so small that the data in
1369 question cannot be fetched, the routines to fetch the data will throw an
1370 exception (see the comment at the beginning about tvbuffers improving
1371 the handling of short packets - the tvbuffers keep track of how much
1372 data is in the packet, and throw an exception on an attempt to fetch
1373 data past the end of the packet, so that the dissector won't process
1374 bogus data), causing the Info column not to be filled in.
1376 This means that the Info column will have data for the previous
1377 protocol, which would be confusing if, for example, the Protocol column
1378 had data for this protocol.
1380 Therefore, before a dissector fetches any data whatsoever from the
1381 packet (unless it's a heuristic dissector fetching data to determine
1382 whether the packet is one that it should dissect, in which case it
1383 should check, before fetching the data, whether there's any data to
1384 fetch; if there isn't, it should return FALSE), it should set the
1385 Protocol column and the Info column.
1387 If the Protocol column will ultimately be set to, for example, a value
1388 containing a protocol version number, with the version number being a
1389 field in the packet, the dissector should, before fetching the version
1390 number field or any other field from the packet, set it to a value
1391 without a version number, using 'col_set_str', and should later set it
1392 to a value with the version number after it's fetched the version
1395 If the Info column will ultimately be set to a value containing
1396 information from the packet, the dissector should, before fetching any
1397 fields from the packet, clear the column using 'col_clear' (which is
1398 more efficient than clearing it by calling 'col_set_str' or
1399 'col_add_str' with a null string), and should later set it to the real
1400 string after it's fetched the data to use when doing that.
1403 1.5.5 The col_append_str function.
1405 Sometimes the value of a column, especially the "Info" column, can't be
1406 conveniently constructed at a single point in the dissection process;
1407 for example, it might contain small bits of information from many of the
1408 fields in the packet. 'col_append_str' takes, as arguments, the same
1409 arguments as 'col_add_str', but the string is appended to the end of the
1410 current value for the column, rather than replacing the value for that
1411 column. (Note that no blank separates the appended string from the
1412 string to which it is appended; if you want a blank there, you must add
1413 it yourself as part of the string being appended.)
1416 1.5.6 The col_append_fstr function.
1418 'col_append_fstr' is to 'col_add_fstr' as 'col_append_str' is to
1419 'col_add_str' - it takes, as arguments, the same arguments as
1420 'col_add_fstr', but the formatted string is appended to the end of the
1421 current value for the column, rather than replacing the value for that
1424 1.5.7 The col_append_sep_str and col_append_sep_fstr functions.
1426 In specific situations the developer knows that a column's value will be
1427 created in a stepwise manner, where the appended values are listed. Both
1428 'col_append_sep_str' and 'col_append_sep_fstr' functions will add an item
1429 separator between two consecutive items, and will not add the separator at the
1430 beginning of the column. The remainder of the work both functions do is
1431 identical to what 'col_append_str' and 'col_append_fstr' do.
1433 1.5.8 The col_set_fence and col_prepend_fence_fstr functions.
1435 Sometimes a dissector may be called multiple times for different PDUs in the
1436 same frame (for example in the case of SCTP chunk bundling: several upper
1437 layer data packets may be contained in one SCTP packet). If the upper layer
1438 dissector calls 'col_set_str()' or 'col_clear()' on the Info column when it
1439 begins dissecting each of those PDUs then when the frame is fully dissected
1440 the Info column would contain only the string from the last PDU in the frame.
1441 The 'col_set_fence' function erects a "fence" in the column that prevents
1442 subsequent 'col_...' calls from clearing the data currently in that column.
1443 For example, the SCTP dissector calls 'col_set_fence' on the Info column
1444 after it has called any subdissectors for that chunk so that subdissectors
1445 of any subsequent chunks may only append to the Info column.
1446 'col_prepend_fence_fstr' prepends data before a fence (moving it if
1447 necessary). It will create a fence at the end of the prepended data if the
1448 fence does not already exist.
1451 1.5.9 The col_set_time function.
1453 The 'col_set_time' function takes an nstime value as its third argument.
1454 This nstime value is a relative value and will be added as such to the
1455 column. The fourth argument is the filtername holding this value. This
1456 way, rightclicking on the column makes it possible to build a filter
1457 based on the time-value.
1461 nstime_delta(&ts, &pinfo->fd->abs_ts, &tcpd->ts_first);
1462 col_set_time(pinfo->cinfo, COL_REL_CONV_TIME, &ts, "tcp.time_relative");
1465 1.6 Constructing the protocol tree.
1467 The middle pane of the main window, and the topmost pane of a packet
1468 popup window, are constructed from the "protocol tree" for a packet.
1470 The protocol tree, or proto_tree, is a GNode, the N-way tree structure
1471 available within GLIB. Of course the protocol dissectors don't care
1472 what a proto_tree really is; they just pass the proto_tree pointer as an
1473 argument to the routines which allow them to add items and new branches
1476 When a packet is selected in the packet-list pane, or a packet popup
1477 window is created, a new logical protocol tree (proto_tree) is created.
1478 The pointer to the proto_tree (in this case, 'protocol tree'), is passed
1479 to the top-level protocol dissector, and then to all subsequent protocol
1480 dissectors for that packet, and then the GUI tree is drawn via
1483 The logical proto_tree needs to know detailed information about the protocols
1484 and fields about which information will be collected from the dissection
1485 routines. By strictly defining (or "typing") the data that can be attached to a
1486 proto tree, searching and filtering becomes possible. This means that for
1487 every protocol and field (which I also call "header fields", since they are
1488 fields in the protocol headers) which might be attached to a tree, some
1489 information is needed.
1491 Every dissector routine will need to register its protocols and fields
1492 with the central protocol routines (in proto.c). At first I thought I
1493 might keep all the protocol and field information about all the
1494 dissectors in one file, but decentralization seemed like a better idea.
1495 That one file would have gotten very large; one small change would have
1496 required a re-compilation of the entire file. Also, by allowing
1497 registration of protocols and fields at run-time, loadable modules of
1498 protocol dissectors (perhaps even user-supplied) is feasible.
1500 To do this, each protocol should have a register routine, which will be
1501 called when Wireshark starts. The code to call the register routines is
1502 generated automatically; to arrange that a protocol's register routine
1503 be called at startup:
1505 the file containing a dissector's "register" routine must be
1506 added to "DISSECTOR_SRC" in "epan/dissectors/Makefile.common";
1508 the "register" routine must have a name of the form
1509 "proto_register_XXX";
1511 the "register" routine must take no argument, and return no
1514 the "register" routine's name must appear in the source file
1515 either at the beginning of the line, or preceded only by "void "
1516 at the beginning of the line (that would typically be the
1517 definition) - other white space shouldn't cause a problem, e.g.:
1519 void proto_register_XXX(void) {
1528 proto_register_XXX( void )
1535 and so on should work.
1537 For every protocol or field that a dissector wants to register, a variable of
1538 type int needs to be used to keep track of the protocol. The IDs are
1539 needed for establishing parent/child relationships between protocols and
1540 fields, as well as associating data with a particular field so that it
1541 can be stored in the logical tree and displayed in the GUI protocol
1544 Some dissectors will need to create branches within their tree to help
1545 organize header fields. These branches should be registered as header
1546 fields. Only true protocols should be registered as protocols. This is
1547 so that a display filter user interface knows how to distinguish
1548 protocols from fields.
1550 A protocol is registered with the name of the protocol and its
1553 Here is how the frame "protocol" is registered.
1557 proto_frame = proto_register_protocol (
1559 /* short name */ "Frame",
1560 /* abbrev */ "frame" );
1562 A header field is also registered with its name and abbreviation, but
1563 information about its data type is needed. It helps to look at
1564 the header_field_info struct to see what information is expected:
1566 struct header_field_info {
1571 const void *strings;
1579 A string representing the name of the field. This is the name
1580 that will appear in the graphical protocol tree. It must be a non-empty
1585 A string with an abbreviation of the field. We concatenate the
1586 abbreviation of the parent protocol with an abbreviation for the field,
1587 using a period as a separator. For example, the "src" field in an IP packet
1588 would have "ip.src" as an abbreviation. It is acceptable to have
1589 multiple levels of periods if, for example, you have fields in your
1590 protocol that are then subdivided into subfields. For example, TRMAC
1591 has multiple error fields, so the abbreviations follow this pattern:
1592 "trmac.errors.iso", "trmac.errors.noniso", etc.
1594 The abbreviation is the identifier used in a display filter. If it is
1595 an empty string then the field will not be filterable.
1599 The type of value this field holds. The current field types are:
1601 FT_NONE No field type. Used for fields that
1602 aren't given a value, and that can only
1603 be tested for presence or absence; a
1604 field that represents a data structure,
1605 with a subtree below it containing
1606 fields for the members of the structure,
1607 or that represents an array with a
1608 subtree below it containing fields for
1609 the members of the array, might be an
1611 FT_PROTOCOL Used for protocols which will be placing
1612 themselves as top-level items in the
1613 "Packet Details" pane of the UI.
1614 FT_BOOLEAN 0 means "false", any other value means
1616 FT_FRAMENUM A frame number; if this is used, the "Go
1617 To Corresponding Frame" menu item can
1619 FT_UINT8 An 8-bit unsigned integer.
1620 FT_UINT16 A 16-bit unsigned integer.
1621 FT_UINT24 A 24-bit unsigned integer.
1622 FT_UINT32 A 32-bit unsigned integer.
1623 FT_UINT64 A 64-bit unsigned integer.
1624 FT_INT8 An 8-bit signed integer.
1625 FT_INT16 A 16-bit signed integer.
1626 FT_INT24 A 24-bit signed integer.
1627 FT_INT32 A 32-bit signed integer.
1628 FT_INT64 A 64-bit signed integer.
1629 FT_FLOAT A single-precision floating point number.
1630 FT_DOUBLE A double-precision floating point number.
1631 FT_ABSOLUTE_TIME Seconds (4 bytes) and nanoseconds (4 bytes)
1632 of time displayed as month name, month day,
1633 year, hours, minutes, and seconds with 9
1634 digits after the decimal point.
1635 FT_RELATIVE_TIME Seconds (4 bytes) and nanoseconds (4 bytes)
1636 of time displayed as seconds and 9 digits
1637 after the decimal point.
1638 FT_STRING A string of characters, not necessarily
1639 NUL-terminated, but possibly NUL-padded.
1640 This, and the other string-of-characters
1641 types, are to be used for text strings,
1642 not raw binary data.
1643 FT_STRINGZ A NUL-terminated string of characters.
1644 FT_EBCDIC A string of characters, not necessarily
1645 NUL-terminated, but possibly NUL-padded.
1646 The data from the packet is converted from
1647 EBCDIC to ASCII before displaying to the user.
1648 FT_UINT_STRING A counted string of characters, consisting
1649 of a count (represented as an integral value,
1650 of width given in the proto_tree_add_item()
1651 call) followed immediately by that number of
1653 FT_ETHER A six octet string displayed in
1654 Ethernet-address format.
1655 FT_BYTES A string of bytes with arbitrary values;
1656 used for raw binary data.
1657 FT_UINT_BYTES A counted string of bytes, consisting
1658 of a count (represented as an integral value,
1659 of width given in the proto_tree_add_item()
1660 call) followed immediately by that number of
1661 arbitrary values; used for raw binary data.
1662 FT_IPv4 A version 4 IP address (4 bytes) displayed
1663 in dotted-quad IP address format (4
1664 decimal numbers separated by dots).
1665 FT_IPv6 A version 6 IP address (16 bytes) displayed
1666 in standard IPv6 address format.
1667 FT_IPXNET An IPX address displayed in hex as a 6-byte
1668 network number followed by a 6-byte station
1670 FT_GUID A Globally Unique Identifier
1671 FT_OID An ASN.1 Object Identifier
1673 Some of these field types are still not handled in the display filter
1674 routines, but the most common ones are. The FT_UINT* variables all
1675 represent unsigned integers, and the FT_INT* variables all represent
1676 signed integers; the number on the end represent how many bits are used
1677 to represent the number.
1679 Some constraints are imposed on the header fields depending on the type
1680 (e.g. FT_BYTES) of the field. Non integral types (e.g. types that are _not_
1681 FT_INT* and FT_UINT*) must use 'BASE_NONE', NULL, 0x0' as values for the
1682 'display', 'strings', 'bitmask' fields. The reason is simply that the type
1683 itself implictly defines the nature of 'display', 'strings', 'bitmask'.
1687 The display field has a couple of overloaded uses. This is unfortunate,
1688 but since we're using C as an application programming language, this sometimes
1689 makes for cleaner programs. Right now I still think that overloading
1690 this variable was okay.
1692 For integer fields (FT_UINT* and FT_INT*), this variable represents the
1693 base in which you would like the value displayed. The acceptable bases
1703 BASE_DEC, BASE_HEX, and BASE_OCT are decimal, hexadecimal, and octal,
1704 respectively. BASE_DEC_HEX and BASE_HEX_DEC display value in two bases
1705 (the 1st representation followed by the 2nd in parenthesis).
1707 BASE_CUSTOM allows one to specify a callback function pointer that will
1708 format the value. The function pointer of the same type as defined by
1709 custom_fmt_func_t in epan/proto.h, specifically:
1711 void func(gchar *, guint32);
1713 The first argument is a pointer to a buffer of the ITEM_LABEL_LENGTH size
1714 and the second argument is the value to be formatted.
1716 For FT_BOOLEAN fields that are also bitfields (i.e. 'bitmask' is non-zero),
1717 'display' is used to tell the proto_tree how wide the parent bitfield is.
1718 With integers this is not needed since the type of integer itself
1719 (FT_UINT8, FT_UINT16, FT_UINT24, FT_UINT32, etc.) tells the proto_tree how
1720 wide the parent bitfield is.
1722 Additionally, BASE_NONE is used for 'display' as a NULL-value. That is,
1723 for non-integers and non-bitfield FT_BOOLEANs, you'll want to use BASE_NONE
1724 in the 'display' field. You may not use BASE_NONE for integers.
1726 It is possible that in the future we will record the endianness of
1727 integers. If so, it is likely that we'll use a bitmask on the display field
1728 so that integers would be represented as BEND|BASE_DEC or LEND|BASE_HEX.
1729 But that has not happened yet.
1733 Some integer fields, of type FT_UINT*, need labels to represent the true
1734 value of a field. You could think of those fields as having an
1735 enumerated data type, rather than an integral data type.
1737 A 'value_string' structure is a way to map values to strings.
1739 typedef struct _value_string {
1744 For fields of that type, you would declare an array of "value_string"s:
1746 static const value_string valstringname[] = {
1747 { INTVAL1, "Descriptive String 1" },
1748 { INTVAL2, "Descriptive String 2" },
1752 (the last entry in the array must have a NULL 'strptr' value, to
1753 indicate the end of the array). The 'strings' field would be set to
1754 'VALS(valstringname)'.
1756 If the field has a numeric rather than an enumerated type, the 'strings'
1757 field would be set to NULL.
1759 If the field has a numeric type that might logically fit in ranges of values
1760 one can use a range_string struct.
1762 Thus a 'range_string' structure is a way to map ranges to strings.
1764 typedef struct _range_string {
1767 const gchar *strptr;
1770 For fields of that type, you would declare an array of "range_string"s:
1772 static const range_string rvalstringname[] = {
1773 { INTVAL_MIN1, INTVALMAX1, "Descriptive String 1" },
1774 { INTVAL_MIN2, INTVALMAX2, "Descriptive String 2" },
1778 If INTVAL_MIN equals INTVAL_MAX for a given entry the range_string
1779 behavior collapses to the one of value_string.
1780 For FT_(U)INT* fields that need a 'range_string' struct, the 'strings' field
1781 would be set to 'RVALS(rvalstringname)'. Furthermore, 'display' field must be
1782 ORed with 'BASE_RANGE_STRING' (e.g. BASE_DEC|BASE_RANGE_STRING).
1784 FT_BOOLEANs have a default map of 0 = "False", 1 (or anything else) = "True".
1785 Sometimes it is useful to change the labels for boolean values (e.g.,
1786 to "Yes"/"No", "Fast"/"Slow", etc.). For these mappings, a struct called
1787 true_false_string is used.
1789 typedef struct true_false_string {
1792 } true_false_string;
1794 For Boolean fields for which "False" and "True" aren't the desired
1795 labels, you would declare a "true_false_string"s:
1797 static const true_false_string boolstringname = {
1802 Its two fields are pointers to the string representing truth, and the
1803 string representing falsehood. For FT_BOOLEAN fields that need a
1804 'true_false_string' struct, the 'strings' field would be set to
1805 'TFS(&boolstringname)'.
1807 If the Boolean field is to be displayed as "False" or "True", the
1808 'strings' field would be set to NULL.
1810 Wireshark predefines a whole range of ready made "true_false_string"s
1811 in tfs.h, included via packet.h.
1815 If the field is a bitfield, then the bitmask is the mask which will
1816 leave only the bits needed to make the field when ANDed with a value.
1817 The proto_tree routines will calculate 'bitshift' automatically
1818 from 'bitmask', by finding the rightmost set bit in the bitmask.
1819 This shift is applied before applying string mapping functions or
1821 If the field is not a bitfield, then bitmask should be set to 0.
1825 This is a string giving a proper description of the field. It should be
1826 at least one grammatically complete sentence, or NULL in which case the
1828 It is meant to provide a more detailed description of the field than the
1829 name alone provides. This information will be used in the man page, and
1830 in a future GUI display-filter creation tool. We might also add tooltips
1831 to the labels in the GUI protocol tree, in which case the blurb would
1832 be used as the tooltip text.
1835 1.6.1 Field Registration.
1837 Protocol registration is handled by creating an instance of the
1838 header_field_info struct (or an array of such structs), and
1839 calling the registration function along with the registration ID of
1840 the protocol that is the parent of the fields. Here is a complete example:
1842 static int proto_eg = -1;
1843 static int hf_field_a = -1;
1844 static int hf_field_b = -1;
1846 static hf_register_info hf[] = {
1849 { "Field A", "proto.field_a", FT_UINT8, BASE_HEX, NULL,
1850 0xf0, "Field A represents Apples", HFILL }},
1853 { "Field B", "proto.field_b", FT_UINT16, BASE_DEC, VALS(vs),
1854 0x0, "Field B represents Bananas", HFILL }}
1857 proto_eg = proto_register_protocol("Example Protocol",
1859 proto_register_field_array(proto_eg, hf, array_length(hf));
1861 Be sure that your array of hf_register_info structs is declared 'static',
1862 since the proto_register_field_array() function does not create a copy
1863 of the information in the array... it uses that static copy of the
1864 information that the compiler created inside your array. Here's the
1865 layout of the hf_register_info struct:
1867 typedef struct hf_register_info {
1868 int *p_id; /* pointer to parent variable */
1869 header_field_info hfinfo;
1872 Also be sure to use the handy array_length() macro found in packet.h
1873 to have the compiler compute the array length for you at compile time.
1875 If you don't have any fields to register, do *NOT* create a zero-length
1876 "hf" array; not all compilers used to compile Wireshark support them.
1877 Just omit the "hf" array, and the "proto_register_field_array()" call,
1880 It is OK to have header fields with a different format be registered with
1881 the same abbreviation. For instance, the following is valid:
1883 static hf_register_info hf[] = {
1885 { &hf_field_8bit, /* 8-bit version of proto.field */
1886 { "Field (8 bit)", "proto.field", FT_UINT8, BASE_DEC, NULL,
1887 0x00, "Field represents FOO", HFILL }},
1889 { &hf_field_32bit, /* 32-bit version of proto.field */
1890 { "Field (32 bit)", "proto.field", FT_UINT32, BASE_DEC, NULL,
1891 0x00, "Field represents FOO", HFILL }}
1894 This way a filter expression can match a header field, irrespective of the
1895 representation of it in the specific protocol context. This is interesting
1896 for protocols with variable-width header fields.
1898 The HFILL macro at the end of the struct will set reasonable default values
1899 for internally used fields.
1901 1.6.2 Adding Items and Values to the Protocol Tree.
1903 A protocol item is added to an existing protocol tree with one of a
1904 handful of proto_XXX_DO_YYY() functions.
1906 Remember that it only makes sense to add items to a protocol tree if its
1907 proto_tree pointer is not null. Should you add an item to a NULL tree, then
1908 the proto_XXX_DO_YYY() function will immediately return. The cost of this
1909 function call can be avoided by checking for the tree pointer.
1911 Subtrees can be made with the proto_item_add_subtree() function:
1913 item = proto_tree_add_item(....);
1914 new_tree = proto_item_add_subtree(item, tree_type);
1916 This will add a subtree under the item in question; a subtree can be
1917 created under an item made by any of the "proto_tree_add_XXX" functions,
1918 so that the tree can be given an arbitrary depth.
1920 Subtree types are integers, assigned by
1921 "proto_register_subtree_array()". To register subtree types, pass an
1922 array of pointers to "gint" variables to hold the subtree type values to
1923 "proto_register_subtree_array()":
1925 static gint ett_eg = -1;
1926 static gint ett_field_a = -1;
1928 static gint *ett[] = {
1933 proto_register_subtree_array(ett, array_length(ett));
1935 in your "register" routine, just as you register the protocol and the
1936 fields for that protocol.
1938 There are several functions that the programmer can use to add either
1939 protocol or field labels to the proto_tree:
1942 proto_tree_add_item(tree, id, tvb, start, length, little_endian);
1945 proto_tree_add_none_format(tree, id, tvb, start, length, format, ...);
1948 proto_tree_add_protocol_format(tree, id, tvb, start, length,
1952 proto_tree_add_bytes(tree, id, tvb, start, length, start_ptr);
1955 proto_tree_add_bytes_format(tree, id, tvb, start, length, start_ptr,
1959 proto_tree_add_bytes_format_value(tree, id, tvb, start, length,
1960 start_ptr, format, ...);
1963 proto_tree_add_time(tree, id, tvb, start, length, value_ptr);
1966 proto_tree_add_time_format(tree, id, tvb, start, length, value_ptr,
1970 proto_tree_add_time_format_value(tree, id, tvb, start, length,
1971 value_ptr, format, ...);
1974 proto_tree_add_ipxnet(tree, id, tvb, start, length, value);
1977 proto_tree_add_ipxnet_format(tree, id, tvb, start, length, value,
1981 proto_tree_add_ipxnet_format_value(tree, id, tvb, start, length,
1982 value, format, ...);
1985 proto_tree_add_ipv4(tree, id, tvb, start, length, value);
1988 proto_tree_add_ipv4_format(tree, id, tvb, start, length, value,
1992 proto_tree_add_ipv4_format_value(tree, id, tvb, start, length,
1993 value, format, ...);
1996 proto_tree_add_ipv6(tree, id, tvb, start, length, value_ptr);
1999 proto_tree_add_ipv6_format(tree, id, tvb, start, length, value_ptr,
2003 proto_tree_add_ipv6_format_value(tree, id, tvb, start, length,
2004 value_ptr, format, ...);
2007 proto_tree_add_ether(tree, id, tvb, start, length, value_ptr);
2010 proto_tree_add_ether_format(tree, id, tvb, start, length, value_ptr,
2014 proto_tree_add_ether_format_value(tree, id, tvb, start, length,
2015 value_ptr, format, ...);
2018 proto_tree_add_string(tree, id, tvb, start, length, value_ptr);
2021 proto_tree_add_string_format(tree, id, tvb, start, length, value_ptr,
2025 proto_tree_add_string_format_value(tree, id, tvb, start, length,
2026 value_ptr, format, ...);
2029 proto_tree_add_boolean(tree, id, tvb, start, length, value);
2032 proto_tree_add_boolean_format(tree, id, tvb, start, length, value,
2036 proto_tree_add_boolean_format_value(tree, id, tvb, start, length,
2037 value, format, ...);
2040 proto_tree_add_float(tree, id, tvb, start, length, value);
2043 proto_tree_add_float_format(tree, id, tvb, start, length, value,
2047 proto_tree_add_float_format_value(tree, id, tvb, start, length,
2048 value, format, ...);
2051 proto_tree_add_double(tree, id, tvb, start, length, value);
2054 proto_tree_add_double_format(tree, id, tvb, start, length, value,
2058 proto_tree_add_double_format_value(tree, id, tvb, start, length,
2059 value, format, ...);
2062 proto_tree_add_uint(tree, id, tvb, start, length, value);
2065 proto_tree_add_uint_format(tree, id, tvb, start, length, value,
2069 proto_tree_add_uint_format_value(tree, id, tvb, start, length,
2070 value, format, ...);
2073 proto_tree_add_uint64(tree, id, tvb, start, length, value);
2076 proto_tree_add_uint64_format(tree, id, tvb, start, length, value,
2080 proto_tree_add_uint64_format_value(tree, id, tvb, start, length,
2081 value, format, ...);
2084 proto_tree_add_int(tree, id, tvb, start, length, value);
2087 proto_tree_add_int_format(tree, id, tvb, start, length, value,
2091 proto_tree_add_int_format_value(tree, id, tvb, start, length,
2092 value, format, ...);
2095 proto_tree_add_int64(tree, id, tvb, start, length, value);
2098 proto_tree_add_int64_format(tree, id, tvb, start, length, value,
2102 proto_tree_add_int64_format_value(tree, id, tvb, start, length,
2103 value, format, ...);
2106 proto_tree_add_text(tree, tvb, start, length, format, ...);
2109 proto_tree_add_text_valist(tree, tvb, start, length, format, ap);
2112 proto_tree_add_guid(tree, id, tvb, start, length, value_ptr);
2115 proto_tree_add_guid_format(tree, id, tvb, start, length, value_ptr,
2119 proto_tree_add_guid_format_value(tree, id, tvb, start, length,
2120 value_ptr, format, ...);
2123 proto_tree_add_oid(tree, id, tvb, start, length, value_ptr);
2126 proto_tree_add_oid_format(tree, id, tvb, start, length, value_ptr,
2130 proto_tree_add_oid_format_value(tree, id, tvb, start, length,
2131 value_ptr, format, ...);
2134 proto_tree_add_bits_item(tree, id, tvb, bit_offset, no_of_bits,
2138 proto_tree_add_bits_ret_val(tree, id, tvb, bit_offset, no_of_bits,
2139 return_value, little_endian);
2142 proto_tree_add_bitmask(tree, tvb, start, header, ett, fields,
2146 proto_tree_add_bitmask_text(tree, tvb, offset, len, name, fallback,
2147 ett, fields, little_endian, flags);
2149 The 'tree' argument is the tree to which the item is to be added. The
2150 'tvb' argument is the tvbuff from which the item's value is being
2151 extracted; the 'start' argument is the offset from the beginning of that
2152 tvbuff of the item being added, and the 'length' argument is the length,
2153 in bytes, of the item, bit_offset is the offset in bits and no_of_bits
2154 is the length in bits.
2156 The length of some items cannot be determined until the item has been
2157 dissected; to add such an item, add it with a length of -1, and, when the
2158 dissection is complete, set the length with 'proto_item_set_len()':
2161 proto_item_set_len(ti, length);
2163 The "ti" argument is the value returned by the call that added the item
2164 to the tree, and the "length" argument is the length of the item.
2166 proto_tree_add_item()
2167 ---------------------
2168 proto_tree_add_item is used when you wish to do no special formatting.
2169 The item added to the GUI tree will contain the name (as passed in the
2170 proto_register_*() function) and a value. The value will be fetched
2171 from the tvbuff by proto_tree_add_item(), based on the type of the field
2172 and, for integral and Boolean fields, the byte order of the value; the
2173 byte order is specified by the 'little_endian' argument, which is TRUE
2174 if the value is little-endian and FALSE if it is big-endian.
2176 Now that definitions of fields have detailed information about bitfield
2177 fields, you can use proto_tree_add_item() with no extra processing to
2178 add bitfield values to your tree. Here's an example. Take the Format
2179 Identifier (FID) field in the Transmission Header (TH) portion of the SNA
2180 protocol. The FID is the high nibble of the first byte of the TH. The
2181 FID would be registered like this:
2183 name = "Format Identifier"
2184 abbrev = "sna.th.fid"
2187 strings = sna_th_fid_vals
2190 The bitmask contains the value which would leave only the FID if bitwise-ANDed
2191 against the parent field, the first byte of the TH.
2193 The code to add the FID to the tree would be;
2195 proto_tree_add_item(bf_tree, hf_sna_th_fid, tvb, offset, 1, TRUE);
2197 The definition of the field already has the information about bitmasking
2198 and bitshifting, so it does the work of masking and shifting for us!
2199 This also means that you no longer have to create value_string structs
2200 with the values bitshifted. The value_string for FID looks like this,
2201 even though the FID value is actually contained in the high nibble.
2202 (You'd expect the values to be 0x0, 0x10, 0x20, etc.)
2204 /* Format Identifier */
2205 static const value_string sna_th_fid_vals[] = {
2206 { 0x0, "SNA device <--> Non-SNA Device" },
2207 { 0x1, "Subarea Node <--> Subarea Node" },
2208 { 0x2, "Subarea Node <--> PU2" },
2209 { 0x3, "Subarea Node or SNA host <--> Subarea Node" },
2212 { 0xf, "Adjacent Subarea Nodes" },
2216 The final implication of this is that display filters work the way you'd
2217 naturally expect them to. You'd type "sna.th.fid == 0xf" to find Adjacent
2218 Subarea Nodes. The user does not have to shift the value of the FID to
2219 the high nibble of the byte ("sna.th.fid == 0xf0") as was necessary
2222 proto_tree_add_protocol_format()
2223 --------------------------------
2224 proto_tree_add_protocol_format is used to add the top-level item for the
2225 protocol when the dissector routine wants complete control over how the
2226 field and value will be represented on the GUI tree. The ID value for
2227 the protocol is passed in as the "id" argument; the rest of the
2228 arguments are a "printf"-style format and any arguments for that format.
2229 The caller must include the name of the protocol in the format; it is
2230 not added automatically as in proto_tree_add_item().
2232 proto_tree_add_none_format()
2233 ----------------------------
2234 proto_tree_add_none_format is used to add an item of type FT_NONE.
2235 The caller must include the name of the field in the format; it is
2236 not added automatically as in proto_tree_add_item().
2238 proto_tree_add_bytes()
2239 proto_tree_add_time()
2240 proto_tree_add_ipxnet()
2241 proto_tree_add_ipv4()
2242 proto_tree_add_ipv6()
2243 proto_tree_add_ether()
2244 proto_tree_add_string()
2245 proto_tree_add_boolean()
2246 proto_tree_add_float()
2247 proto_tree_add_double()
2248 proto_tree_add_uint()
2249 proto_tree_add_uint64()
2250 proto_tree_add_int()
2251 proto_tree_add_int64()
2252 proto_tree_add_guid()
2253 proto_tree_add_oid()
2254 ------------------------
2255 These routines are used to add items to the protocol tree if either:
2257 the value of the item to be added isn't just extracted from the
2258 packet data, but is computed from data in the packet;
2260 the value was fetched into a variable.
2262 The 'value' argument has the value to be added to the tree.
2264 NOTE: in all cases where the 'value' argument is a pointer, a copy is
2265 made of the object pointed to; if you have dynamically allocated a
2266 buffer for the object, that buffer will not be freed when the protocol
2267 tree is freed - you must free the buffer yourself when you don't need it
2270 For proto_tree_add_bytes(), the 'value_ptr' argument is a pointer to a
2273 For proto_tree_add_time(), the 'value_ptr' argument is a pointer to an
2274 "nstime_t", which is a structure containing the time to be added; it has
2275 'secs' and 'nsecs' members, giving the integral part and the fractional
2276 part of a time in units of seconds, with 'nsecs' being the number of
2277 nanoseconds. For absolute times, "secs" is a UNIX-style seconds since
2278 January 1, 1970, 00:00:00 GMT value.
2280 For proto_tree_add_ipxnet(), the 'value' argument is a 32-bit IPX
2283 For proto_tree_add_ipv4(), the 'value' argument is a 32-bit IPv4
2284 address, in network byte order.
2286 For proto_tree_add_ipv6(), the 'value_ptr' argument is a pointer to a
2287 128-bit IPv6 address.
2289 For proto_tree_add_ether(), the 'value_ptr' argument is a pointer to a
2292 For proto_tree_add_string(), the 'value_ptr' argument is a pointer to a
2295 For proto_tree_add_boolean(), the 'value' argument is a 32-bit integer.
2296 It is masked and shifted as defined by the field info after which zero
2297 means "false", and non-zero means "true".
2299 For proto_tree_add_float(), the 'value' argument is a 'float' in the
2300 host's floating-point format.
2302 For proto_tree_add_double(), the 'value' argument is a 'double' in the
2303 host's floating-point format.
2305 For proto_tree_add_uint(), the 'value' argument is a 32-bit unsigned
2306 integer value, in host byte order. (This routine cannot be used to add
2309 For proto_tree_add_uint64(), the 'value' argument is a 64-bit unsigned
2310 integer value, in host byte order.
2312 For proto_tree_add_int(), the 'value' argument is a 32-bit signed
2313 integer value, in host byte order. (This routine cannot be used to add
2316 For proto_tree_add_int64(), the 'value' argument is a 64-bit signed
2317 integer value, in host byte order.
2319 For proto_tree_add_guid(), the 'value_ptr' argument is a pointer to an
2322 For proto_tree_add_oid(), the 'value_ptr' argument is a pointer to an
2323 ASN.1 Object Identifier.
2325 proto_tree_add_bytes_format()
2326 proto_tree_add_time_format()
2327 proto_tree_add_ipxnet_format()
2328 proto_tree_add_ipv4_format()
2329 proto_tree_add_ipv6_format()
2330 proto_tree_add_ether_format()
2331 proto_tree_add_string_format()
2332 proto_tree_add_boolean_format()
2333 proto_tree_add_float_format()
2334 proto_tree_add_double_format()
2335 proto_tree_add_uint_format()
2336 proto_tree_add_uint64_format()
2337 proto_tree_add_int_format()
2338 proto_tree_add_int64_format()
2339 proto_tree_add_guid_format()
2340 proto_tree_add_oid_format()
2341 ----------------------------
2342 These routines are used to add items to the protocol tree when the
2343 dissector routine wants complete control over how the field and value
2344 will be represented on the GUI tree. The argument giving the value is
2345 the same as the corresponding proto_tree_add_XXX() function; the rest of
2346 the arguments are a "printf"-style format and any arguments for that
2347 format. The caller must include the name of the field in the format; it
2348 is not added automatically as in the proto_tree_add_XXX() functions.
2350 proto_tree_add_bytes_format_value()
2351 proto_tree_add_time_format_value()
2352 proto_tree_add_ipxnet_format_value()
2353 proto_tree_add_ipv4_format_value()
2354 proto_tree_add_ipv6_format_value()
2355 proto_tree_add_ether_format_value()
2356 proto_tree_add_string_format_value()
2357 proto_tree_add_boolean_format_value()
2358 proto_tree_add_float_format_value()
2359 proto_tree_add_double_format_value()
2360 proto_tree_add_uint_format_value()
2361 proto_tree_add_uint64_format_value()
2362 proto_tree_add_int_format_value()
2363 proto_tree_add_int64_format_value()
2364 proto_tree_add_guid_format_value()
2365 proto_tree_add_oid_format_value()
2366 ------------------------------------
2368 These routines are used to add items to the protocol tree when the
2369 dissector routine wants complete control over how the value will be
2370 represented on the GUI tree. The argument giving the value is the same
2371 as the corresponding proto_tree_add_XXX() function; the rest of the
2372 arguments are a "printf"-style format and any arguments for that format.
2373 With these routines, unlike the proto_tree_add_XXX_format() routines,
2374 the name of the field is added automatically as in the
2375 proto_tree_add_XXX() functions; only the value is added with the format.
2377 proto_tree_add_text()
2378 ---------------------
2379 proto_tree_add_text() is used to add a label to the GUI tree. It will
2380 contain no value, so it is not searchable in the display filter process.
2381 This function was needed in the transition from the old-style proto_tree
2382 to this new-style proto_tree so that Wireshark would still decode all
2383 protocols w/o being able to filter on all protocols and fields.
2384 Otherwise we would have had to cripple Wireshark's functionality while we
2385 converted all the old-style proto_tree calls to the new-style proto_tree
2386 calls. In other words, you should not use this in new code unless you've got
2387 a specific reason (see below).
2389 This can also be used for items with subtrees, which may not have values
2390 themselves - the items in the subtree are the ones with values.
2392 For a subtree, the label on the subtree might reflect some of the items
2393 in the subtree. This means the label can't be set until at least some
2394 of the items in the subtree have been dissected. To do this, use
2395 'proto_item_set_text()' or 'proto_item_append_text()':
2398 proto_item_set_text(proto_item *ti, ...);
2401 proto_item_append_text(proto_item *ti, ...);
2403 'proto_item_set_text()' takes as an argument the value returned by
2404 'proto_tree_add_text()', a 'printf'-style format string, and a set of
2405 arguments corresponding to '%' format items in that string, and replaces
2406 the text for the item created by 'proto_tree_add_text()' with the result
2407 of applying the arguments to the format string.
2409 'proto_item_append_text()' is similar, but it appends to the text for
2410 the item the result of applying the arguments to the format string.
2412 For example, early in the dissection, one might do:
2414 ti = proto_tree_add_text(tree, tvb, offset, length, <label>);
2418 proto_item_set_text(ti, "%s: %s", type, value);
2420 after the "type" and "value" fields have been extracted and dissected.
2421 <label> would be a label giving what information about the subtree is
2422 available without dissecting any of the data in the subtree.
2424 Note that an exception might be thrown when trying to extract the values of
2425 the items used to set the label, if not all the bytes of the item are
2426 available. Thus, one should create the item with text that is as
2427 meaningful as possible, and set it or append additional information to
2428 it as the values needed to supply that information are extracted.
2430 proto_tree_add_text_valist()
2431 ----------------------------
2432 This is like proto_tree_add_text(), but takes, as the last argument, a
2433 'va_list'; it is used to allow routines that take a printf-like
2434 variable-length list of arguments to add a text item to the protocol
2437 proto_tree_add_bits_item()
2438 --------------------------
2439 Adds a number of bits to the protocol tree which does not have to be byte
2440 aligned. The offset and length is in bits.
2443 ..10 1010 10.. .... "value" (formatted as FT_ indicates).
2445 proto_tree_add_bits_ret_val()
2446 -----------------------------
2447 Works in the same way but also returns the value of the read bits.
2449 proto_tree_add_bitmask() and proto_tree_add_bitmask_text()
2450 ----------------------------------------------------------
2451 This function provides an easy to use and convenient helper function
2452 to manage many types of common bitmasks that occur in protocols.
2454 This function will dissect a 1/2/3/4 byte large bitmask into its individual
2456 header is an integer type and must be of type FT_[U]INT{8|16|24|32} and
2457 represents the entire width of the bitmask.
2459 'header' and 'ett' are the hf fields and ett field respectively to create an
2460 expansion that covers the 1-4 bytes of the bitmask.
2462 'fields' is a NULL terminated array of pointers to hf fields representing
2463 the individual subfields of the bitmask. These fields must either be integers
2464 of the same byte width as 'header' or of the type FT_BOOLEAN.
2465 Each of the entries in 'fields' will be dissected as an item under the
2466 'header' expansion and also IF the field is a boolean and IF it is set to 1,
2467 then the name of that boolean field will be printed on the 'header' expansion
2468 line. For integer type subfields that have a value_string defined, the
2469 matched string from that value_string will be printed on the expansion line
2472 Example: (from the SCSI dissector)
2473 static int hf_scsi_inq_peripheral = -1;
2474 static int hf_scsi_inq_qualifier = -1;
2475 static int hf_scsi_inq_devtype = -1;
2477 static gint ett_scsi_inq_peripheral = -1;
2479 static const int *peripheal_fields[] = {
2480 &hf_scsi_inq_qualifier,
2481 &hf_scsi_inq_devtype,
2485 /* Qualifier and DeviceType */
2486 proto_tree_add_bitmask(tree, tvb, offset, hf_scsi_inq_peripheral,
2487 ett_scsi_inq_peripheral, peripheal_fields, FALSE);
2490 { &hf_scsi_inq_peripheral,
2491 {"Peripheral", "scsi.inquiry.preipheral", FT_UINT8, BASE_HEX,
2492 NULL, 0, NULL, HFILL}},
2493 { &hf_scsi_inq_qualifier,
2494 {"Qualifier", "scsi.inquiry.qualifier", FT_UINT8, BASE_HEX,
2495 VALS (scsi_qualifier_val), 0xE0, NULL, HFILL}},
2496 { &hf_scsi_inq_devtype,
2497 {"Device Type", "scsi.inquiry.devtype", FT_UINT8, BASE_HEX,
2498 VALS (scsi_devtype_val), SCSI_DEV_BITS, NULL, HFILL}},
2501 Which provides very pretty dissection of this one byte bitmask.
2503 Peripheral: 0x05, Qualifier: Device type is connected to logical unit, Device Type: CD-ROM
2504 000. .... = Qualifier: Device type is connected to logical unit (0x00)
2505 ...0 0101 = Device Type: CD-ROM (0x05)
2507 The proto_tree_add_bitmask_text() function is an extended version of
2508 the proto_tree_add_bitmask() function. In addition, it allows to:
2509 - Provide a leading text (e.g. "Flags: ") that will appear before
2510 the comma-separated list of field values
2511 - Provide a fallback text (e.g. "None") that will be appended if
2512 no fields warranted a change to the top-level title.
2513 - Using flags, specify which fields will affect the top-level title.
2515 There are the following flags defined:
2517 BMT_NO_APPEND - the title is taken "as-is" from the 'name' argument.
2518 BMT_NO_INT - only boolean flags are added to the title.
2519 BMT_NO_FALSE - boolean flags are only added to the title if they are set.
2520 BMT_NO_TFS - only add flag name to the title, do not use true_false_string
2522 The proto_tree_add_bitmask() behavior can be obtained by providing
2523 both 'name' and 'fallback' arguments as NULL, and a flags of
2524 (BMT_NO_FALSE|BMT_NO_TFS).
2526 PROTO_ITEM_SET_GENERATED()
2527 --------------------------
2528 PROTO_ITEM_SET_GENERATED is used to mark fields as not being read from the
2529 captured data directly, but inferred from one or more values.
2531 One of the primary uses of this is the presentation of verification of
2532 checksums. Every IP packet has a checksum line, which can present the result
2533 of the checksum verification, if enabled in the preferences. The result is
2534 presented as a subtree, where the result is enclosed in square brackets
2535 indicating a generated field.
2537 Header checksum: 0x3d42 [correct]
2541 PROTO_ITEM_SET_HIDDEN()
2542 -----------------------
2543 PROTO_ITEM_SET_HIDDEN is used to hide fields, which have already been added
2544 to the tree, from being visible in the displayed tree.
2546 NOTE that creating hidden fields is actually quite a bad idea from a UI design
2547 perspective because the user (someone who did not write nor has ever seen the
2548 code) has no way of knowing that hidden fields are there to be filtered on
2549 thus defeating the whole purpose of putting them there. A Better Way might
2550 be to add the fields (that might otherwise be hidden) to a subtree where they
2551 won't be seen unless the user opens the subtree--but they can be found if the
2554 One use for hidden fields (which would be better implemented using visible
2555 fields in a subtree) follows: The caller may want a value to be
2556 included in a tree so that the packet can be filtered on this field, but
2557 the representation of that field in the tree is not appropriate. An
2558 example is the token-ring routing information field (RIF). The best way
2559 to show the RIF in a GUI is by a sequence of ring and bridge numbers.
2560 Rings are 3-digit hex numbers, and bridges are single hex digits:
2562 RIF: 001-A-013-9-C0F-B-555
2564 In the case of RIF, the programmer should use a field with no value and
2565 use proto_tree_add_none_format() to build the above representation. The
2566 programmer can then add the ring and bridge values, one-by-one, with
2567 proto_tree_add_item() and hide them with PROTO_ITEM_SET_HIDDEN() so that the
2568 user can then filter on or search for a particular ring or bridge. Here's a
2569 skeleton of how the programmer might code this.
2572 rif = create_rif_string(...);
2574 proto_tree_add_none_format(tree, hf_tr_rif_label, ..., "RIF: %s", rif);
2576 for(i = 0; i < num_rings; i++) {
2579 pi = proto_tree_add_item(tree, hf_tr_rif_ring, ..., FALSE);
2580 PROTO_ITEM_SET_HIDDEN(pi);
2582 for(i = 0; i < num_rings - 1; i++) {
2585 pi = proto_tree_add_item(tree, hf_tr_rif_bridge, ..., FALSE);
2586 PROTO_ITEM_SET_HIDDEN(pi);
2589 The logical tree has these items:
2591 hf_tr_rif_label, text="RIF: 001-A-013-9-C0F-B-555", value = NONE
2592 hf_tr_rif_ring, hidden, value=0x001
2593 hf_tr_rif_bridge, hidden, value=0xA
2594 hf_tr_rif_ring, hidden, value=0x013
2595 hf_tr_rif_bridge, hidden, value=0x9
2596 hf_tr_rif_ring, hidden, value=0xC0F
2597 hf_tr_rif_bridge, hidden, value=0xB
2598 hf_tr_rif_ring, hidden, value=0x555
2600 GUI or print code will not display the hidden fields, but a display
2601 filter or "packet grep" routine will still see the values. The possible
2602 filter is then possible:
2604 tr.rif_ring eq 0x013
2608 PROTO_ITEM_SET_URL is used to mark fields as containing a URL. This can only
2609 be done with fields of type FT_STRING(Z). If these fields are presented they
2610 are underlined, as could be done in a browser. These fields are sensitive to
2611 clicks as well, launching the configured browser with this URL as parameter.
2613 1.7 Utility routines.
2615 1.7.1 match_strval and val_to_str.
2617 A dissector may need to convert a value to a string, using a
2618 'value_string' structure, by hand, rather than by declaring a field with
2619 an associated 'value_string' structure; this might be used, for example,
2620 to generate a COL_INFO line for a frame.
2622 'match_strval()' will do that:
2625 match_strval(guint32 val, const value_string *vs)
2627 It will look up the value 'val' in the 'value_string' table pointed to
2628 by 'vs', and return either the corresponding string, or NULL if the
2629 value could not be found in the table. Note that, unless 'val' is
2630 guaranteed to be a value in the 'value_string' table ("guaranteed" as in
2631 "the code has already checked that it's one of those values" or "the
2632 table handles all possible values of the size of 'val'", not "the
2633 protocol spec says it has to be" - protocol specs do not prevent invalid
2634 packets from being put onto a network or into a purported packet capture
2635 file), you must check whether 'match_strval()' returns NULL, and arrange
2636 that its return value not be dereferenced if it's NULL. 'val_to_str()'
2637 can be used to generate a string for values not found in the table:
2640 val_to_str(guint32 val, const value_string *vs, const char *fmt)
2642 If the value 'val' is found in the 'value_string' table pointed to by
2643 'vs', 'val_to_str' will return the corresponding string; otherwise, it
2644 will use 'fmt' as an 'sprintf'-style format, with 'val' as an argument,
2645 to generate a string, and will return a pointer to that string.
2646 You can use it in a call to generate a COL_INFO line for a frame such as
2648 col_add_fstr(COL_INFO, ", %s", val_to_str(val, table, "Unknown %d"));
2650 1.7.2 match_strrval and rval_to_str.
2652 A dissector may need to convert a range of values to a string, using a
2653 'range_string' structure.
2655 'match_strrval()' will do that:
2658 match_strrval(guint32 val, const range_string *rs)
2660 It will look up the value 'val' in the 'range_string' table pointed to
2661 by 'rs', and return either the corresponding string, or NULL if the
2662 value could not be found in the table. Please note that its base
2663 behavior is inherited from match_strval().
2665 'rval_to_str()' can be used to generate a string for values not found in
2669 rval_to_str(guint32 val, const range_string *rs, const char *fmt)
2671 If the value 'val' is found in the 'range_string' table pointed to by
2672 'rs', 'rval_to_str' will return the corresponding string; otherwise, it
2673 will use 'fmt' as an 'sprintf'-style format, with 'val' as an argument,
2674 to generate a string, and will return a pointer to that string. Please
2675 note that its base behavior is inherited from match_strval().
2677 1.8 Calling Other Dissectors.
2679 As each dissector completes its portion of the protocol analysis, it
2680 is expected to create a new tvbuff of type TVBUFF_SUBSET which
2681 contains the payload portion of the protocol (that is, the bytes
2682 that are relevant to the next dissector).
2684 The syntax for creating a new TVBUFF_SUBSET is:
2686 next_tvb = tvb_new_subset(tvb, offset, length, reported_length)
2689 tvb is the tvbuff that the dissector has been working on. It
2690 can be a tvbuff of any type.
2692 next_tvb is the new TVBUFF_SUBSET.
2694 offset is the byte offset of 'tvb' at which the new tvbuff
2695 should start. The first byte is the 0th byte.
2697 length is the number of bytes in the new TVBUFF_SUBSET. A length
2698 argument of -1 says to use as many bytes as are available in
2701 reported_length is the number of bytes that the current protocol
2702 says should be in the payload. A reported_length of -1 says that
2703 the protocol doesn't say anything about the size of its payload.
2706 An example from packet-ipx.c -
2709 dissect_ipx(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
2712 int reported_length, available_length;
2715 /* Make the next tvbuff */
2717 /* IPX does have a length value in the header, so calculate report_length */
2718 Set this to -1 if there isn't any length information in the protocol
2720 reported_length = ipx_length - IPX_HEADER_LEN;
2722 /* Calculate the available data in the packet,
2723 set this to -1 to use all the data in the tv_buffer
2725 available_length = tvb_length(tvb) - IPX_HEADER_LEN;
2727 /* Create the tvbuffer for the next dissector */
2728 next_tvb = tvb_new_subset(tvb, IPX_HEADER_LEN,
2729 MIN(available_length, reported_length),
2732 /* call the next dissector */
2733 dissector_next( next_tvb, pinfo, tree);
2736 1.9 Editing Makefile.common to add your dissector.
2738 To arrange that your dissector will be built as part of Wireshark, you
2739 must add the name of the source file for your dissector to the
2740 'DISSECTOR_SRC' macro in the 'Makefile.common' file in the 'epan/dissectors'
2741 directory. (Note that this is for modern versions of UNIX, so there
2742 is no 14-character limitation on file names, and for modern versions of
2743 Windows, so there is no 8.3-character limitation on file names.)
2745 If your dissector also has its own header file or files, you must add
2746 them to the 'DISSECTOR_INCLUDES' macro in the 'Makefile.common' file in
2747 the 'epan/dissectors' directory, so that it's included when release source
2748 tarballs are built (otherwise, the source in the release tarballs won't
2751 1.10 Using the SVN source code tree.
2753 See <http://www.wireshark.org/develop.html>
2755 1.11 Submitting code for your new dissector.
2757 - VERIFY that your dissector code does not use prohibited or deprecated APIs
2759 perl <wireshark_root>/tools/checkAPIs.pl <source-filename(s)>
2761 - TEST YOUR DISSECTOR BEFORE SUBMITTING IT.
2762 Use fuzz-test.sh and/or randpkt against your dissector. These are
2763 described at <http://wiki.wireshark.org/FuzzTesting>.
2765 - Subscribe to <mailto:wireshark-dev[AT]wireshark.org> by sending an email to
2766 <mailto:wireshark-dev-request[AT]wireshark.org?body="help"> or visiting
2767 <http://www.wireshark.org/lists/>.
2769 - 'svn add' all the files of your new dissector.
2771 - 'svn diff' the workspace and save the result to a file.
2773 - Edit the diff file - remove any changes unrelated to your new dissector,
2774 e.g. changes in config.nmake
2776 - Submit a bug report to the Wireshark bug database, found at
2777 <http://bugs.wireshark.org>, qualified as an enhancement and attach your
2778 diff file there. Set the review request flag to '?' so it will pop up in
2779 the patch review list.
2781 - Create a Wiki page on the protocol at <http://wiki.wireshark.org>.
2782 A template is provided so it is easy to setup in a consistent style.
2784 - If possible, add sample capture files to the sample captures page at
2785 <http://wiki.wireshark.org/SampleCaptures>. These files are used by
2786 the automated build system for fuzz testing.
2788 - If you find that you are contributing a lot to wireshark on an ongoing
2789 basis you can request to become a committer which will allow you to
2790 commit files to subversion directly.
2792 2. Advanced dissector topics.
2796 Some of the advanced features are being worked on constantly. When using them
2797 it is wise to check the relevant header and source files for additional details.
2799 2.2 Following "conversations".
2801 In wireshark a conversation is defined as a series of data packets between two
2802 address:port combinations. A conversation is not sensitive to the direction of
2803 the packet. The same conversation will be returned for a packet bound from
2804 ServerA:1000 to ClientA:2000 and the packet from ClientA:2000 to ServerA:1000.
2806 There are five routines that you will use to work with a conversation:
2807 conversation_new, find_conversation, conversation_add_proto_data,
2808 conversation_get_proto_data, and conversation_delete_proto_data.
2811 2.2.1 The conversation_init function.
2813 This is an internal routine for the conversation code. As such you
2814 will not have to call this routine. Just be aware that this routine is
2815 called at the start of each capture and before the packets are filtered
2816 with a display filter. The routine will destroy all stored
2817 conversations. This routine does NOT clean up any data pointers that are
2818 passed in the conversation_new 'data' variable. You are responsible for
2819 this clean up if you pass a malloc'ed pointer in this variable.
2821 See item 2.2.8 for more information about the 'data' pointer.
2824 2.2.2 The conversation_new function.
2826 This routine will create a new conversation based upon two address/port
2827 pairs. If you want to associate with the conversation a pointer to a
2828 private data structure you must use the conversation_add_proto_data
2829 function. The ptype variable is used to differentiate between
2830 conversations over different protocols, i.e. TCP and UDP. The options
2831 variable is used to define a conversation that will accept any destination
2832 address and/or port. Set options = 0 if the destination port and address
2833 are know when conversation_new is called. See section 2.4 for more
2834 information on usage of the options parameter.
2836 The conversation_new prototype:
2837 conversation_t *conversation_new(guint32 setup_frame, address *addr1,
2838 address *addr2, port_type ptype, guint32 port1, guint32 port2,
2842 guint32 setup_frame = The lowest numbered frame for this conversation
2843 address* addr1 = first data packet address
2844 address* addr2 = second data packet address
2845 port_type ptype = port type, this is defined in packet.h
2846 guint32 port1 = first data packet port
2847 guint32 port2 = second data packet port
2848 guint options = conversation options, NO_ADDR2 and/or NO_PORT2
2850 setup_frame indicates the first frame for this conversation, and is used to
2851 distinguish multiple conversations with the same addr1/port1 and addr2/port2
2852 pair that occur within the same capture session.
2854 "addr1" and "port1" are the first address/port pair; "addr2" and "port2"
2855 are the second address/port pair. A conversation doesn't have source
2856 and destination address/port pairs - packets in a conversation go in
2857 both directions - so "addr1"/"port1" may be the source or destination
2858 address/port pair; "addr2"/"port2" would be the other pair.
2860 If NO_ADDR2 is specified, the conversation is set up so that a
2861 conversation lookup will match only the "addr1" address; if NO_PORT2 is
2862 specified, the conversation is set up so that a conversation lookup will
2863 match only the "port1" port; if both are specified, i.e.
2864 NO_ADDR2|NO_PORT2, the conversation is set up so that the lookup will
2865 match only the "addr1"/"port1" address/port pair. This can be used if a
2866 packet indicates that, later in the capture, a conversation will be
2867 created using certain addresses and ports, in the case where the packet
2868 doesn't specify the addresses and ports of both sides.
2870 2.2.3 The find_conversation function.
2872 Call this routine to look up a conversation. If no conversation is found,
2873 the routine will return a NULL value.
2875 The find_conversation prototype:
2877 conversation_t *find_conversation(guint32 frame_num, address *addr_a,
2878 address *addr_b, port_type ptype, guint32 port_a, guint32 port_b,
2882 guint32 frame_num = a frame number to match
2883 address* addr_a = first address
2884 address* addr_b = second address
2885 port_type ptype = port type
2886 guint32 port_a = first data packet port
2887 guint32 port_b = second data packet port
2888 guint options = conversation options, NO_ADDR_B and/or NO_PORT_B
2890 frame_num is a frame number to match. The conversation returned is where
2891 (frame_num >= conversation->setup_frame
2892 && frame_num < conversation->next->setup_frame)
2893 Suppose there are a total of 3 conversations (A, B, and C) that match
2894 addr_a/port_a and addr_b/port_b, where the setup_frame used in
2895 conversation_new() for A, B and C are 10, 50, and 100 respectively. The
2896 frame_num passed in find_conversation is compared to the setup_frame of each
2897 conversation. So if (frame_num >= 10 && frame_num < 50), conversation A is
2898 returned. If (frame_num >= 50 && frame_num < 100), conversation B is returned.
2899 If (frame_num >= 100) conversation C is returned.
2901 "addr_a" and "port_a" are the first address/port pair; "addr_b" and
2902 "port_b" are the second address/port pair. Again, as a conversation
2903 doesn't have source and destination address/port pairs, so
2904 "addr_a"/"port_a" may be the source or destination address/port pair;
2905 "addr_b"/"port_b" would be the other pair. The search will match the
2906 "a" address/port pair against both the "1" and "2" address/port pairs,
2907 and match the "b" address/port pair against both the "2" and "1"
2908 address/port pairs; you don't have to worry about which side the "a" or
2909 "b" pairs correspond to.
2911 If the NO_ADDR_B flag was specified to "find_conversation()", the
2912 "addr_b" address will be treated as matching any "wildcarded" address;
2913 if the NO_PORT_B flag was specified, the "port_b" port will be treated
2914 as matching any "wildcarded" port. If both flags are specified, i.e.
2915 NO_ADDR_B|NO_PORT_B, the "addr_b" address will be treated as matching
2916 any "wildcarded" address and the "port_b" port will be treated as
2917 matching any "wildcarded" port.
2920 2.2.4 The conversation_add_proto_data function.
2922 Once you have created a conversation with conversation_new, you can
2923 associate data with it using this function.
2925 The conversation_add_proto_data prototype:
2927 void conversation_add_proto_data(conversation_t *conv, int proto,
2931 conversation_t *conv = the conversation in question
2932 int proto = registered protocol number
2933 void *data = dissector data structure
2935 "conversation" is the value returned by conversation_new. "proto" is a
2936 unique protocol number created with proto_register_protocol. Protocols
2937 are typically registered in the proto_register_XXXX section of your
2938 dissector. "data" is a pointer to the data you wish to associate with the
2939 conversation. Using the protocol number allows several dissectors to
2940 associate data with a given conversation.
2943 2.2.5 The conversation_get_proto_data function.
2945 After you have located a conversation with find_conversation, you can use
2946 this function to retrieve any data associated with it.
2948 The conversation_get_proto_data prototype:
2950 void *conversation_get_proto_data(conversation_t *conv, int proto);
2953 conversation_t *conv = the conversation in question
2954 int proto = registered protocol number
2956 "conversation" is the conversation created with conversation_new. "proto"
2957 is a unique protocol number created with proto_register_protocol,
2958 typically in the proto_register_XXXX portion of a dissector. The function
2959 returns a pointer to the data requested, or NULL if no data was found.
2962 2.2.6 The conversation_delete_proto_data function.
2964 After you are finished with a conversation, you can remove your association
2965 with this function. Please note that ONLY the conversation entry is
2966 removed. If you have allocated any memory for your data, you must free it
2969 The conversation_delete_proto_data prototype:
2971 void conversation_delete_proto_data(conversation_t *conv, int proto);
2974 conversation_t *conv = the conversation in question
2975 int proto = registered protocol number
2977 "conversation" is the conversation created with conversation_new. "proto"
2978 is a unique protocol number created with proto_register_protocol,
2979 typically in the proto_register_XXXX portion of a dissector.
2982 2.2.7 Using timestamps relative to the conversation
2984 There is a framework to calculate timestamps relative to the start of the
2985 conversation. First of all the timestamp of the first packet that has been
2986 seen in the conversation must be kept in the protocol data to be able
2987 to calculate the timestamp of the current packet relative to the start
2988 of the conversation. The timestamp of the last packet that was seen in the
2989 conversation should also be kept in the protocol data. This way the
2990 delta time between the current packet and the previous packet in the
2991 conversation can be calculated.
2993 So add the following items to the struct that is used for the protocol data:
2998 The ts_prev value should only be set during the first run through the
2999 packets (ie pinfo->fd->flags.visited is false).
3001 Next step is to use the per-packet information (described in section 2.5)
3002 to keep the calculated delta timestamp, as it can only be calculated
3003 on the first run through the packets. This is because a packet can be
3004 selected in random order once the whole file has been read.
3006 After calculating the conversation timestamps, it is time to put them in
3007 the appropriate columns with the function 'col_set_time' (described in
3008 section 1.5.9). There are two columns for conversation timestamps:
3010 COL_REL_CONV_TIME, /* Relative time to beginning of conversation */
3011 COL_DELTA_CONV_TIME,/* Delta time to last frame in conversation */
3013 Last but not least, there MUST be a preference in each dissector that
3014 uses conversation timestamps that makes it possible to enable and
3015 disable the calculation of conversation timestamps. The main argument
3016 for this is that a higher level conversation is able to overwrite
3017 the values of lowel level conversations in these two columns. Being
3018 able to actively select which protocols may overwrite the conversation
3019 timestamp columns gives the user the power to control these columns.
3020 (A second reason is that conversation timestamps use the per-packet
3021 data structure which uses additional memory, which should be avoided
3022 if these timestamps are not needed)
3024 Have a look at the differences to packet-tcp.[ch] in SVN 22966 and
3025 SVN 23058 to see the implementation of conversation timestamps for
3029 2.2.8 The example conversation code with GMemChunk's.
3031 For a conversation between two IP addresses and ports you can use this as an
3032 example. This example uses the GMemChunk to allocate memory and stores the data
3033 pointer in the conversation 'data' variable.
3035 NOTE: Remember to register the init routine (my_dissector_init) in the
3036 protocol_register routine.
3039 /************************ Global values ************************/
3041 /* the number of entries in the memory chunk array */
3042 #define my_init_count 10
3044 /* define your structure here */
3049 /* the GMemChunk base structure */
3050 static GMemChunk *my_vals = NULL;
3052 /* Registered protocol number */
3053 static int my_proto = -1;
3056 /********************* in the dissector routine *********************/
3058 /* the local variables in the dissector */
3060 conversation_t *conversation;
3061 my_entry_t *data_ptr;
3064 /* look up the conversation */
3066 conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
3067 pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
3069 /* if conversation found get the data pointer that you stored */
3071 data_ptr = (my_entry_t*)conversation_get_proto_data(conversation, my_proto);
3074 /* new conversation create local data structure */
3076 data_ptr = g_mem_chunk_alloc(my_vals);
3078 /*** add your code here to setup the new data structure ***/
3080 /* create the conversation with your data pointer */
3082 conversation = conversation_new(pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype,
3083 pinfo->srcport, pinfo->destport, 0);
3084 conversation_add_proto_data(conversation, my_proto, (void *)data_ptr);
3087 /* at this point the conversation data is ready */
3090 /******************* in the dissector init routine *******************/
3092 #define my_init_count 20
3095 my_dissector_init(void)
3098 /* destroy memory chunks if needed */
3101 g_mem_chunk_destroy(my_vals);
3103 /* now create memory chunks */
3105 my_vals = g_mem_chunk_new("my_proto_vals",
3107 my_init_count * sizeof(my_entry_t),
3111 /***************** in the protocol register routine *****************/
3113 /* register re-init routine */
3115 register_init_routine(&my_dissector_init);
3117 my_proto = proto_register_protocol("My Protocol", "My Protocol", "my_proto");
3120 2.2.9 An example conversation code that starts at a specific frame number.
3122 Sometimes a dissector has determined that a new conversation is needed that
3123 starts at a specific frame number, when a capture session encompasses multiple
3124 conversation that reuse the same src/dest ip/port pairs. You can use the
3125 conversation->setup_frame returned by find_conversation with
3126 pinfo->fd->num to determine whether or not there already exists a conversation
3127 that starts at the specific frame number.
3129 /* in the dissector routine */
3131 conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
3132 pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
3133 if (conversation == NULL || (conversation->setup_frame != pinfo->fd->num)) {
3134 /* It's not part of any conversation or the returned
3135 * conversation->setup_frame doesn't match the current frame
3138 conversation = conversation_new(pinfo->fd->num, &pinfo->src,
3139 &pinfo->dst, pinfo->ptype, pinfo->srcport, pinfo->destport,
3144 2.2.10 The example conversation code using conversation index field.
3146 Sometimes the conversation isn't enough to define a unique data storage
3147 value for the network traffic. For example if you are storing information
3148 about requests carried in a conversation, the request may have an
3149 identifier that is used to define the request. In this case the
3150 conversation and the identifier are required to find the data storage
3151 pointer. You can use the conversation data structure index value to
3152 uniquely define the conversation.
3154 See packet-afs.c for an example of how to use the conversation index. In
3155 this dissector multiple requests are sent in the same conversation. To store
3156 information for each request the dissector has an internal hash table based
3157 upon the conversation index and values inside the request packets.
3160 /* in the dissector routine */
3162 /* to find a request value, first lookup conversation to get index */
3163 /* then used the conversation index, and request data to find data */
3164 /* in the local hash table */
3166 conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
3167 pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
3168 if (conversation == NULL) {
3169 /* It's not part of any conversation - create a new one. */
3170 conversation = conversation_new(pinfo->fd->num, &pinfo->src,
3171 &pinfo->dst, pinfo->ptype, pinfo->srcport, pinfo->destport,
3175 request_key.conversation = conversation->index;
3176 request_key.service = pntohs(&rxh->serviceId);
3177 request_key.callnumber = pntohl(&rxh->callNumber);
3179 request_val = (struct afs_request_val *)g_hash_table_lookup(
3180 afs_request_hash, &request_key);
3182 /* only allocate a new hash element when it's a request */
3184 if (!request_val && !reply)
3186 new_request_key = g_mem_chunk_alloc(afs_request_keys);
3187 *new_request_key = request_key;
3189 request_val = g_mem_chunk_alloc(afs_request_vals);
3190 request_val -> opcode = pntohl(&afsh->opcode);
3191 opcode = request_val->opcode;
3193 g_hash_table_insert(afs_request_hash, new_request_key,
3199 2.3 Dynamic conversation dissector registration.
3202 NOTE: This sections assumes that all information is available to
3203 create a complete conversation, source port/address and
3204 destination port/address. If either the destination port or
3205 address is know, see section 2.4 Dynamic server port dissector
3208 For protocols that negotiate a secondary port connection, for example
3209 packet-msproxy.c, a conversation can install a dissector to handle
3210 the secondary protocol dissection. After the conversation is created
3211 for the negotiated ports use the conversation_set_dissector to define
3212 the dissection routine.
3213 Before we create these conversations or assign a dissector to them we should
3214 first check that the conversation does not already exist and if it exists
3215 whether it is registered to our protocol or not.
3216 We should do this because it is uncommon but it does happen that multiple
3217 different protocols can use the same socketpair during different stages of
3218 an application cycle. By keeping track of the frame number a conversation
3219 was started in wireshark can still tell these different protocols apart.
3221 The second argument to conversation_set_dissector is a dissector handle,
3222 which is created with a call to create_dissector_handle or
3225 create_dissector_handle takes as arguments a pointer to the dissector
3226 function and a protocol ID as returned by proto_register_protocol;
3227 register_dissector takes as arguments a string giving a name for the
3228 dissector, a pointer to the dissector function, and a protocol ID.
3230 The protocol ID is the ID for the protocol dissected by the function.
3231 The function will not be called if the protocol has been disabled by the
3232 user; instead, the data for the protocol will be dissected as raw data.
3236 /* the handle for the dynamic dissector *
3237 static dissector_handle_t sub_dissector_handle;
3239 /* prototype for the dynamic dissector */
3240 static void sub_dissector(tvbuff_t *tvb, packet_info *pinfo,
3243 /* in the main protocol dissector, where the next dissector is setup */
3245 /* if conversation has a data field, create it and load structure */
3247 /* First check if a conversation already exists for this
3250 conversation = find_conversation(pinfo->fd->num,
3251 &pinfo->src, &pinfo->dst, protocol,
3252 src_port, dst_port, new_conv_info, 0);
3254 /* If there is no such conversation, or if there is one but for
3255 someone else's protocol then we just create a new conversation
3256 and assign our protocol to it.
3258 if ( (conversation == NULL) ||
3259 (conversation->dissector_handle != sub_dissector_handle) ) {
3260 new_conv_info = g_mem_chunk_alloc(new_conv_vals);
3261 new_conv_info->data1 = value1;
3263 /* create the conversation for the dynamic port */
3264 conversation = conversation_new(pinfo->fd->num,
3265 &pinfo->src, &pinfo->dst, protocol,
3266 src_port, dst_port, new_conv_info, 0);
3268 /* set the dissector for the new conversation */
3269 conversation_set_dissector(conversation, sub_dissector_handle);
3274 proto_register_PROTOABBREV(void)
3278 sub_dissector_handle = create_dissector_handle(sub_dissector,
3284 2.4 Dynamic server port dissector registration.
3286 NOTE: While this example used both NO_ADDR2 and NO_PORT2 to create a
3287 conversation with only one port and address set, this isn't a
3288 requirement. Either the second port or the second address can be set
3289 when the conversation is created.
3291 For protocols that define a server address and port for a secondary
3292 protocol, a conversation can be used to link a protocol dissector to
3293 the server port and address. The key is to create the new
3294 conversation with the second address and port set to the "accept
3297 Some server applications can use the same port for different protocols during
3298 different stages of a transaction. For example it might initially use SNMP
3299 to perform some discovery and later switch to use TFTP using the same port.
3300 In order to handle this properly we must first check whether such a
3301 conversation already exists or not and if it exists we also check whether the
3302 registered dissector_handle for that conversation is "our" dissector or not.
3303 If not we create a new conversation on top of the previous one and set this new
3304 conversation to use our protocol.
3305 Since wireshark keeps track of the frame number where a conversation started
3306 wireshark will still be able to keep the packets apart even though they do use
3307 the same socketpair.
3308 (See packet-tftp.c and packet-snmp.c for examples of this)
3310 There are two support routines that will allow the second port and/or
3311 address to be set later.
3313 conversation_set_port2( conversation_t *conv, guint32 port);
3314 conversation_set_addr2( conversation_t *conv, address addr);
3316 These routines will change the second address or port for the
3317 conversation. So, the server port conversation will be converted into a
3318 more complete conversation definition. Don't use these routines if you
3319 want to create a conversation between the server and client and retain the
3320 server port definition, you must create a new conversation.
3325 /* the handle for the dynamic dissector *
3326 static dissector_handle_t sub_dissector_handle;
3330 /* in the main protocol dissector, where the next dissector is setup */
3332 /* if conversation has a data field, create it and load structure */
3334 new_conv_info = g_mem_chunk_alloc(new_conv_vals);
3335 new_conv_info->data1 = value1;
3337 /* create the conversation for the dynamic server address and port */
3338 /* NOTE: The second address and port values don't matter because the */
3339 /* NO_ADDR2 and NO_PORT2 options are set. */
3341 /* First check if a conversation already exists for this
3344 conversation = find_conversation(pinfo->fd->num,
3345 &server_src_addr, 0, protocol,
3346 server_src_port, 0, NO_ADDR2 | NO_PORT_B);
3347 /* If there is no such conversation, or if there is one but for
3348 someone else's protocol then we just create a new conversation
3349 and assign our protocol to it.
3351 if ( (conversation == NULL) ||
3352 (conversation->dissector_handle != sub_dissector_handle) ) {
3353 conversation = conversation_new(pinfo->fd->num,
3354 &server_src_addr, 0, protocol,
3355 server_src_port, 0, new_conv_info, NO_ADDR2 | NO_PORT2);
3357 /* set the dissector for the new conversation */
3358 conversation_set_dissector(conversation, sub_dissector_handle);
3361 2.5 Per-packet information.
3363 Information can be stored for each data packet that is processed by the
3364 dissector. The information is added with the p_add_proto_data function and
3365 retrieved with the p_get_proto_data function. The data pointers passed into
3366 the p_add_proto_data are not managed by the proto_data routines. If you use
3367 malloc or any other dynamic memory allocation scheme, you must release the
3368 data when it isn't required.
3371 p_add_proto_data(frame_data *fd, int proto, void *proto_data)
3373 p_get_proto_data(frame_data *fd, int proto)
3376 fd - The fd pointer in the pinfo structure, pinfo->fd
3377 proto - Protocol id returned by the proto_register_protocol call
3378 during initialization
3379 proto_data - pointer to the dissector data.
3382 2.6 User Preferences.
3384 If the dissector has user options, there is support for adding these preferences
3385 to a configuration dialog.
3387 You must register the module with the preferences routine with -
3389 module_t *prefs_register_protocol(proto_id, void (*apply_cb)(void))
3391 Where: proto_id - the value returned by "proto_register_protocol()" when
3392 the protocol was registered.
3393 apply_cb - Callback routine that is called when preferences are
3394 applied. It may be NULL, which inhibits the callback.
3396 Then you can register the fields that can be configured by the user with these
3399 /* Register a preference with an unsigned integral value. */
3400 void prefs_register_uint_preference(module_t *module, const char *name,
3401 const char *title, const char *description, guint base, guint *var);
3403 /* Register a preference with an Boolean value. */
3404 void prefs_register_bool_preference(module_t *module, const char *name,
3405 const char *title, const char *description, gboolean *var);
3407 /* Register a preference with an enumerated value. */
3408 void prefs_register_enum_preference(module_t *module, const char *name,
3409 const char *title, const char *description, gint *var,
3410 const enum_val_t *enumvals, gboolean radio_buttons)
3412 /* Register a preference with a character-string value. */
3413 void prefs_register_string_preference(module_t *module, const char *name,
3414 const char *title, const char *description, char **var)
3416 /* Register a preference with a range of unsigned integers (e.g.,
3419 void prefs_register_range_preference(module_t *module, const char *name,
3420 const char *title, const char *description, range_t *var,
3423 Where: module - Returned by the prefs_register_protocol routine
3424 name - This is appended to the name of the protocol, with a
3425 "." between them, to construct a name that identifies
3426 the field in the preference file; the name itself
3427 should not include the protocol name, as the name in
3428 the preference file will already have it
3429 title - Field title in the preferences dialog
3430 description - Comments added to the preference file above the
3432 var - pointer to the storage location that is updated when the
3433 field is changed in the preference dialog box
3434 base - Base that the unsigned integer is expected to be in,
3436 enumvals - an array of enum_val_t structures. This must be
3437 NULL-terminated; the members of that structure are:
3439 a short name, to be used with the "-o" flag - it
3440 should not contain spaces or upper-case letters,
3441 so that it's easier to put in a command line;
3443 a description, which is used in the GUI (and
3444 which, for compatibility reasons, is currently
3445 what's written to the preferences file) - it can
3446 contain spaces, capital letters, punctuation,
3449 the numerical value corresponding to that name
3451 radio_buttons - TRUE if the field is to be displayed in the
3452 preferences dialog as a set of radio buttons,
3453 FALSE if it is to be displayed as an option
3455 max_value - The maximum allowed value for a range (0 is the minimum).
3457 An example from packet-beep.c -
3459 proto_beep = proto_register_protocol("Blocks Extensible Exchange Protocol",
3464 /* Register our configuration options for BEEP, particularly our port */
3466 beep_module = prefs_register_protocol(proto_beep, proto_reg_handoff_beep);
3468 prefs_register_uint_preference(beep_module, "tcp.port", "BEEP TCP Port",
3469 "Set the port for BEEP messages (if other"
3470 " than the default of 10288)",
3471 10, &global_beep_tcp_port);
3473 prefs_register_bool_preference(beep_module, "strict_header_terminator",
3474 "BEEP Header Requires CRLF",
3475 "Specifies that BEEP requires CRLF as a "
3476 "terminator, and not just CR or LF",
3477 &global_beep_strict_term);
3479 This will create preferences "beep.tcp.port" and
3480 "beep.strict_header_terminator", the first of which is an unsigned
3481 integer and the second of which is a Boolean.
3483 Note that a warning will pop up if you've saved such preference to the
3484 preference file and you subsequently take the code out. The way to make
3485 a preference obsolete is to register it as such:
3487 /* Register a preference that used to be supported but no longer is. */
3488 void prefs_register_obsolete_preference(module_t *module,
3491 2.7 Reassembly/desegmentation for protocols running atop TCP.
3493 There are two main ways of reassembling a Protocol Data Unit (PDU) which
3494 spans across multiple TCP segments. The first approach is simpler, but
3495 assumes you are running atop of TCP when this occurs (but your dissector
3496 might run atop of UDP, too, for example), and that your PDUs consist of a
3497 fixed amount of data that includes enough information to determine the PDU
3498 length, possibly followed by additional data. The second method is more
3499 generic but requires more code and is less efficient.
3501 2.7.1 Using tcp_dissect_pdus().
3503 For the first method, you register two different dissection methods, one
3504 for the TCP case, and one for the other cases. It is a good idea to
3505 also have a dissect_PROTO_common function which will parse the generic
3506 content that you can find in all PDUs which is called from
3507 dissect_PROTO_tcp when the reassembly is complete and from
3508 dissect_PROTO_udp (or dissect_PROTO_other).
3510 To register the distinct dissector functions, consider the following
3511 example, stolen from packet-dns.c:
3513 dissector_handle_t dns_udp_handle;
3514 dissector_handle_t dns_tcp_handle;
3515 dissector_handle_t mdns_udp_handle;
3517 dns_udp_handle = create_dissector_handle(dissect_dns_udp,
3519 dns_tcp_handle = create_dissector_handle(dissect_dns_tcp,
3521 mdns_udp_handle = create_dissector_handle(dissect_mdns_udp,
3524 dissector_add("udp.port", UDP_PORT_DNS, dns_udp_handle);
3525 dissector_add("tcp.port", TCP_PORT_DNS, dns_tcp_handle);
3526 dissector_add("udp.port", UDP_PORT_MDNS, mdns_udp_handle);
3527 dissector_add("tcp.port", TCP_PORT_MDNS, dns_tcp_handle);
3529 The dissect_dns_udp function does very little work and calls
3530 dissect_dns_common, while dissect_dns_tcp calls tcp_dissect_pdus with a
3531 reference to a callback which will be called with reassembled data:
3534 dissect_dns_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
3536 tcp_dissect_pdus(tvb, pinfo, tree, dns_desegment, 2,
3537 get_dns_pdu_len, dissect_dns_tcp_pdu);
3540 (The dissect_dns_tcp_pdu function acts similarly to dissect_dns_udp.)
3541 The arguments to tcp_dissect_pdus are:
3543 the tvbuff pointer, packet_info pointer, and proto_tree pointer
3544 passed to the dissector;
3546 a gboolean flag indicating whether desegmentation is enabled for
3549 the number of bytes of PDU data required to determine the length
3552 a routine that takes as arguments a packet_info pointer, a tvbuff
3553 pointer and an offset value representing the offset into the tvbuff
3554 at which a PDU begins and should return - *without* throwing an
3555 exception (it is guaranteed that the number of bytes specified by the
3556 previous argument to tcp_dissect_pdus is available, but more data
3557 might not be available, so don't refer to any data past that) - the
3558 total length of the PDU, in bytes;
3560 a routine that's passed a tvbuff pointer, packet_info pointer,
3561 and proto_tree pointer, with the tvbuff containing a
3562 possibly-reassembled PDU, and that should dissect that PDU.
3564 2.7.2 Modifying the pinfo struct.
3566 The second reassembly mode is preferred when the dissector cannot determine
3567 how many bytes it will need to read in order to determine the size of a PDU.
3568 It may also be useful if your dissector needs to support reassembly from
3569 protocols other than TCP.
3571 Your dissect_PROTO will initially be passed a tvbuff containing the payload of
3572 the first packet. It should dissect as much data as it can, noting that it may
3573 contain more than one complete PDU. If the end of the provided tvbuff coincides
3574 with the end of a PDU then all is well and your dissector can just return as
3575 normal. (If it is a new-style dissector, it should return the number of bytes
3576 successfully processed.)
3578 If the dissector discovers that the end of the tvbuff does /not/ coincide with
3579 the end of a PDU, (ie, there is half of a PDU at the end of the tvbuff), it can
3580 indicate this to the parent dissector, by updating the pinfo struct. The
3581 desegment_offset field is the offset in the tvbuff at which the dissector will
3582 continue processing when next called. The desegment_len field should contain
3583 the estimated number of additional bytes required for completing the PDU. Next
3584 time your dissect_PROTO is called, it will be passed a tvbuff composed of the
3585 end of the data from the previous tvbuff together with desegment_len more bytes.
3587 If the dissector cannot tell how many more bytes it will need, it should set
3588 desegment_len=DESEGMENT_ONE_MORE_SEGMENT; it will then be called again as soon
3589 as any more data becomes available. Dissectors should set the desegment_len to a
3590 reasonable value when possible rather than always setting
3591 DESEGMENT_ONE_MORE_SEGMENT as it will generally be more efficient. Also, you
3592 *must not* set desegment_len=1 in this case, in the hope that you can change
3593 your mind later: once you return a positive value from desegment_len, your PDU
3594 boundary is set in stone.
3596 static hf_register_info hf[] = {
3598 {"C String", "c.string", FT_STRING, BASE_NONE, NULL, 0x0,
3604 * Dissect a buffer containing C strings.
3606 * @param tvb The buffer to dissect.
3607 * @param pinfo Packet Info.
3608 * @param tree The protocol tree.
3610 static void dissect_cstr(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
3613 while(offset < tvb_reported_length(tvb)) {
3614 gint available = tvb_reported_length_remaining(tvb, offset);
3615 gint len = tvb_strnlen(tvb, offset, available);
3618 /* we ran out of data: ask for more */
3619 pinfo->desegment_offset = offset;
3620 pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
3624 col_set_str(pinfo->cinfo, COL_INFO, "C String");
3626 len += 1; /* Add one for the '\0' */
3629 proto_tree_add_item(tree, hf_cstring, tvb, offset, len, FALSE);
3631 offset += (guint)len;
3634 /* if we get here, then the end of the tvb coincided with the end of a
3635 string. Happy days. */
3638 This simple dissector will repeatedly return DESEGMENT_ONE_MORE_SEGMENT
3639 requesting more data until the tvbuff contains a complete C string. The C string
3640 will then be added to the protocol tree. Note that there may be more
3641 than one complete C string in the tvbuff, so the dissection is done in a
3646 The ptvcursor API allows a simpler approach to writing dissectors for
3647 simple protocols. The ptvcursor API works best for protocols whose fields
3648 are static and whose format does not depend on the value of other fields.
3649 However, even if only a portion of your protocol is statically defined,
3650 then that portion could make use of ptvcursors.
3652 The ptvcursor API lets you extract data from a tvbuff, and add it to a
3653 protocol tree in one step. It also keeps track of the position in the
3654 tvbuff so that you can extract data again without having to compute any
3655 offsets --- hence the "cursor" name of the API.
3657 The three steps for a simple protocol are:
3658 1. Create a new ptvcursor with ptvcursor_new()
3659 2. Add fields with multiple calls of ptvcursor_add()
3660 3. Delete the ptvcursor with ptvcursor_free()
3662 ptvcursor offers the possibility to add subtrees in the tree as well. It can be
3663 done in very simple steps :
3664 1. Create a new subtree with ptvcursor_push_subtree(). The old subtree is
3665 pushed in a stack and the new subtree will be used by ptvcursor.
3666 2. Add fields with multiple calls of ptvcursor_add(). The fields will be
3667 added in the new subtree created at the previous step.
3668 3. Pop the previous subtree with ptvcursor_pop_subtree(). The previous
3669 subtree is again used by ptvcursor.
3670 Note that at the end of the parsing of a packet you must have popped each
3671 subtree you pushed. If it's not the case, the dissector will generate an error.
3673 To use the ptvcursor API, include the "ptvcursor.h" file. The PGM dissector
3674 is an example of how to use it. You don't need to look at it as a guide;
3675 instead, the API description here should be good enough.
3677 2.8.1 ptvcursor API.
3680 ptvcursor_new(proto_tree* tree, tvbuff_t* tvb, gint offset)
3681 This creates a new ptvcursor_t object for iterating over a tvbuff.
3682 You must call this and use this ptvcursor_t object so you can use the
3686 ptvcursor_add(ptvcursor_t* ptvc, int hf, gint length, gboolean endianness)
3687 This will extract 'length' bytes from the tvbuff and place it in
3688 the proto_tree as field 'hf', which is a registered header_field. The
3689 pointer to the proto_item that is created is passed back to you. Internally,
3690 the ptvcursor advances its cursor so the next call to ptvcursor_add
3691 starts where this call finished. The 'endianness' parameter matters for
3692 FT_UINT* and FT_INT* fields.
3695 ptvcursor_add_no_advance(ptvcursor_t* ptvc, int hf, gint length, gboolean endianness)
3696 Like ptvcursor_add, but does not advance the internal cursor.
3699 ptvcursor_advance(ptvcursor_t* ptvc, gint length)
3700 Advances the internal cursor without adding anything to the proto_tree.
3703 ptvcursor_free(ptvcursor_t* ptvc)
3704 Frees the memory associated with the ptvcursor. You must call this
3705 after your dissection with the ptvcursor API is completed.
3709 ptvcursor_push_subtree(ptvcursor_t* ptvc, proto_item* it, gint ett_subtree)
3710 Pushes the current subtree in the tree stack of the cursor, creates a new
3711 one and sets this one as the working tree.
3714 ptvcursor_pop_subtree(ptvcursor_t* ptvc);
3715 Pops a subtree in the tree stack of the cursor
3718 ptvcursor_add_with_subtree(ptvcursor_t* ptvc, int hfindex, gint length,
3719 gboolean little_endian, gint ett_subtree);
3720 Adds an item to the tree and creates a subtree.
3721 If the length is unknown, length may be defined as SUBTREE_UNDEFINED_LENGTH.
3722 In this case, at the next pop, the item length will be equal to the advancement
3723 of the cursor since the creation of the subtree.
3726 ptvcursor_add_text_with_subtree(ptvcursor_t* ptvc, gint length,
3727 gint ett_subtree, const char* format, ...);
3728 Add a text node to the tree and create a subtree.
3729 If the length is unknown, length may be defined as SUBTREE_UNDEFINED_LENGTH.
3730 In this case, at the next pop, the item length will be equal to the advancement
3731 of the cursor since the creation of the subtree.
3733 2.8.2 Miscellaneous functions.
3736 ptvcursor_tvbuff(ptvcursor_t* ptvc)
3737 Returns the tvbuff associated with the ptvcursor.
3740 ptvcursor_current_offset(ptvcursor_t* ptvc)
3741 Returns the current offset.
3744 ptvcursor_tree(ptvcursor_t* ptvc)
3745 Returns the proto_tree associated with the ptvcursor.
3748 ptvcursor_set_tree(ptvcursor_t* ptvc, proto_tree *tree)
3749 Sets a new proto_tree for the ptvcursor.
3752 ptvcursor_set_subtree(ptvcursor_t* ptvc, proto_item* it, gint ett_subtree);
3753 Creates a subtree and adds it to the cursor as the working tree but does
3754 not save the old working tree.