-$Id: README.developer,v 1.88 2003/12/30 15:49:12 obiot Exp $
-
-This file is a HOWTO for Ethereal developers. It describes how to start coding
-a Ethereal protocol dissector and the use some of the important functions and
-variables.
+$Revision$
+$Date$
+$Author$
+Tabsize: 4
+
+This file is a HOWTO for Wireshark developers. It describes how to start coding
+a Wireshark protocol dissector and the use of some of the important functions
+and variables.
+
+This file is compiled to give in depth information on Wireshark.
+It is by no means all inclusive and complete. Please feel free to send
+remarks and patches to the developer mailing list.
+
+0. Prerequisites.
+
+Before starting to develop a new dissector, a "running" Wireshark build
+environment is required - there's no such thing as a standalone "dissector
+build toolkit".
+
+How to setup such an environment is platform dependent; detailed information
+about these steps can be found in the "Developer's Guide" (available from:
+http://www.wireshark.org) and in the INSTALL and README files of the sources
+root dir.
+
+0.1. General README files.
+
+You'll find additional information in the following README files:
+
+- README.capture - the capture engine internals
+- README.design - Wireshark software design - incomplete
+- README.developer - this file
+- README.display_filter - Display Filter Engine
+- README.idl2wrs - CORBA IDL converter
+- README.packaging - how to distribute a software package containing WS
+- README.regression - regression testing of WS and TS
+- README.stats_tree - a tree statistics counting specific packets
+- README.tapping - "tap" a dissector to get protocol specific events
+- README.xml-output - how to work with the PDML exported output
+- wiretap/README.developer - how to add additional capture file types to
+ Wiretap
+
+0.2. Dissector related README files.
+
+You'll find additional dissector related information in the following README
+files:
+
+- README.binarytrees - fast access to large data collections
+- README.heuristic - what are heuristic dissectors and how to write them
+- README.malloc - how to obtain "memory leak free" memory
+- README.plugins - how to "pluginize" a dissector
+- README.python - writing a dissector in PYTHON.
+- README.request_response_tracking - how to track req./resp. times and such
+
+0.3 Contributors
+
+James Coe <jammer[AT]cin.net>
+Gilbert Ramirez <gram[AT]alumni.rice.edu>
+Jeff Foster <jfoste[AT]woodward.com>
+Olivier Abad <oabad[AT]cybercable.fr>
+Laurent Deniel <laurent.deniel[AT]free.fr>
+Gerald Combs <gerald[AT]wireshark.org>
+Guy Harris <guy[AT]alum.mit.edu>
+Ulf Lamping <ulf.lamping[AT]web.de>
1. Setting up your protocol dissector code.
1.1.1 Portability.
-Ethereal runs on many platforms, and can be compiled with a number of
+Wireshark runs on many platforms, and can be compiled with a number of
different compilers; here are some rules for writing code that will work
on multiple platforms.
Don't use C++-style comments (comments beginning with "//" and running
-to the end of the line); Ethereal's dissectors are written in C, and
+to the end of the line); Wireshark's dissectors are written in C, and
thus run through C rather than C++ compilers, and not all C compilers
support C++-style comments (GCC does, but IBM's C compiler for AIX, for
example, doesn't do so by default).
+In general, don't use C99 features since some C compilers used to compile
+Wireshark don't support C99 (E.G. Microsoft C).
+
+Don't initialize variables in their declaration with non-constant
+values. Not all compilers support this. E.g. don't use
+ guint32 i = somearray[2];
+use
+ guint32 i;
+ i = somearray[2];
+instead.
+
Don't use zero-length arrays; not all compilers support them. If an
array would have no members, just leave it out.
compilers support that. Variables should be declared outside a
function, or at the beginning of a function or compound statement.
-Don't use "inline"; not all compilers support it. If you want to have a
-function be an inline function if the compiler supports it, use
-G_INLINE_FUNC, which is declared by <glib.h>. This may not work with
-functions declared in header files; if it doesn't work, don't declare
-the function in a header file, even if this requires that you not make
-it inline on any platform.
-
-Don't use "long long"; use "gint64" or "guint64", and only do so if
-G_HAVE_GINT64 is defined. Make sure your code works even if
-G_HAVE_GINT64 isn't defined, even if that means treating 64-bit integral
-data types as opaque arrays of bytes on platforms where it's not
-defined. Also, don't assume you can use "%lld", "%llu", "%llx", or
-"%llo" to print 64-bit integral data types - not all platforms support
-"%ll" for printing them.
+Don't use anonymous unions; not all compilers support them.
+Example:
+
+ typedef struct foo {
+ guint32 foo;
+ union {
+ guint32 foo_l;
+ guint16 foo_s;
+ } u; /* have a name here */
+ } foo_t;
Don't use "uchar", "u_char", "ushort", "u_short", "uint", "u_int",
-"ulong", or "u_long"; they aren't defined on all platforms. If you want
-an 8-bit unsigned quantity, use "guint8"; if you want an 8-bit character
-value with the 8th bit not interpreted as a sign bit, use "guchar"; if
-you want a 16-bit unsigned quantity, use "guint16"; if you want a 32-bit
-unsigned quantity, use "guint32"; and if you want an "int-sized"
-unsigned quantity, use "guint". Use "%d", "%u", "%x", and "%o" to print
-those types; don't use "%ld", "%lu", "%lx", or "%lo", as longs are 64
-bits long on many platforms, but "guint32" is 32 bits long.
+"ulong", "u_long" or "boolean"; they aren't defined on all platforms.
+If you want an 8-bit unsigned quantity, use "guint8"; if you want an
+8-bit character value with the 8th bit not interpreted as a sign bit,
+use "guchar"; if you want a 16-bit unsigned quantity, use "guint16";
+if you want a 32-bit unsigned quantity, use "guint32"; and if you want
+an "int-sized" unsigned quantity, use "guint"; if you want a boolean,
+use "gboolean". Use "%d", "%u", "%x", and "%o" to print those types;
+don't use "%ld", "%lu", "%lx", or "%lo", as longs are 64 bits long on
+many platforms, but "guint32" is 32 bits long.
Don't use "long" to mean "signed 32-bit integer", and don't use
"unsigned long" to mean "unsigned 32-bit integer"; "long"s are 64 bits
long on many platforms. Use "gint32" for signed 32-bit integers and use
"guint32" for unsigned 32-bit integers.
+Don't use "long" to mean "signed 64-bit integer" and don't use "unsigned
+long" to mean "unsigned 64-bit integer"; "long"s are 32 bits long on
+many other platforms. Don't use "long long" or "unsigned long long",
+either, as not all platforms support them; use "gint64" or "guint64",
+which will be defined as the appropriate types for 64-bit signed and
+unsigned integers.
+
+On LLP64 data model systems (notably 64-bit Windows), "int" and "long"
+are 32 bits while "size_t" and "ptrdiff_t" are 64 bits. This means that
+the following will generate a compiler warning:
+
+ int i;
+ i = strlen("hello, sailor"); /* Compiler warning */
+
+Normally, you'd just make "i" a size_t. However, many GLib and Wireshark
+functions won't accept a size_t on LLP64:
+
+ size_t i;
+ char greeting[] = "hello, sailor";
+ guint byte_after_greet;
+
+ i = strlen(greeting);
+ byte_after_greet = tvb_get_guint8(tvb, i); /* Compiler warning */
+
+Try to use the appropriate data type when you can. When you can't, you
+will have to cast to a compatible data type, e.g.
+
+ size_t i;
+ char greeting[] = "hello, sailor";
+ guint byte_after_greet;
+
+ i = strlen(greeting);
+ byte_after_greet = tvb_get_guint8(tvb, (gint) i); /* OK */
+
+or
+
+ gint i;
+ char greeting[] = "hello, sailor";
+ guint byte_after_greet;
+
+ i = (gint) strlen(greeting);
+ byte_after_greet = tvb_get_guint8(tvb, i); /* OK */
+
+See http://www.unix.org/version2/whatsnew/lp64_wp.html for more
+information on the sizes of common types in different data models.
+
+When printing or displaying the values of 64-bit integral data types,
+don't use "%lld", "%llu", "%llx", or "%llo" - not all platforms
+support "%ll" for printing 64-bit integral data types. Instead, for
+GLib routines, and routines that use them, such as all the routines in
+Wireshark that take format arguments, use G_GINT64_MODIFIER, for example:
+
+ proto_tree_add_text(tree, tvb, offset, 8,
+ "Sequence Number: %" G_GINT64_MODIFIER "u",
+ sequence_number);
+
+When specifying an integral constant that doesn't fit in 32 bits, don't
+use "LL" at the end of the constant - not all compilers use "LL" for
+that. Instead, put the constant in a call to the "G_GINT64_CONSTANT()"
+macro, e.g.
+
+ G_GINT64_CONSTANT(11644473600U)
+
+rather than
+
+ 11644473600ULL
+
+Don't assume that you can scan through a va_list initialized by va_start
+more than once without closing it with va_end and re-initalizing it with
+va_start. This applies even if you're not scanning through it yourself,
+but are calling a routine that scans through it, such as vfprintf() or
+one of the routines in Wireshark that takes a format and a va_list as an
+argument. You must do
+
+ va_start(ap, format);
+ call_routine1(xxx, format, ap);
+ va_end(ap);
+ va_start(ap, format);
+ call_routine2(xxx, format, ap);
+ va_end(ap);
+
+rather
+ va_start(ap, format);
+ call_routine1(xxx, format, ap);
+ call_routine2(xxx, format, ap);
+ va_end(ap);
+
Don't use a label without a statement following it. For example,
something such as
done:
}
-
+
will not work with all compilers - you have to do
if (...) {
Don't fetch data from packets by getting a pointer to data in the packet
with "tvb_get_ptr()", casting that pointer to a pointer to a structure,
-and dereferencing that pointer. That point won't necessarily be aligned
+and dereferencing that pointer. That pointer won't necessarily be aligned
on the proper boundary, which can cause crashes on some platforms (even
if it doesn't crash on an x86-based PC); furthermore, the data in a
packet is not necessarily in the byte order of the machine on which
-Ethereal is running. Use the tvbuff routines to extract individual
+Wireshark is running. Use the tvbuff routines to extract individual
items from the packet, or use "proto_tree_add_item()" and let it extract
the items for you.
+Don't use structures that overlay packet data, or into which you copy
+packet data; the C programming language does not guarantee any
+particular alignment of fields within a structure, and even the
+extensions that try to guarantee that are compiler-specific and not
+necessarily supported by all compilers used to build Wireshark. Using
+bitfields in those structures is even worse; the order of bitfields
+is not guaranteed.
+
Don't use "ntohs()", "ntohl()", "htons()", or "htonl()"; the header
files required to define or declare them differ between platforms, and
you might be able to get away with not including the appropriate header
-file on your platform but that might not work on other platforms.
+file on your platform but that might not work on other platforms.
Instead, use "g_ntohs()", "g_ntohl()", "g_htons()", and "g_htonl()";
those are declared by <glib.h>, and you'll need to include that anyway,
-as Ethereal header files that all dissectors must include use stuff from
+as Wireshark header files that all dissectors must include use stuff from
<glib.h>.
+Don't fetch a little-endian value using "tvb_get_ntohs() or
+"tvb_get_ntohl()" and then using "g_ntohs()", "g_htons()", "g_ntohl()",
+or "g_htonl()" on the resulting value - the g_ routines in question
+convert between network byte order (big-endian) and *host* byte order,
+not *little-endian* byte order; not all machines on which Wireshark runs
+are little-endian, even though PCs are. Fetch those values using
+"tvb_get_letohs()" and "tvb_get_letohl()".
+
Don't put a comma after the last element of an enum - some compilers may
either warn about it (producing extra noise) or refuse to accept it.
in order to declare the Windows C library routines "_open()",
"_close()", "_read()", and "_write()". Your file must include <glib.h>
-- which many of the Ethereal header files include, so you might not have
+- which many of the Wireshark header files include, so you might not have
to include it explicitly - in order to get "open()", "close()",
"read()", "write()", etc. mapped to "_open()", "_close()", "_read()",
"_write()", etc..
-When opening a file with "fopen()", "freopen()", or "fdopen()", if the
-file contains ASCII text, use "r", "w", "a", and so on as the open mode
+Do not use "open()", "rename()", "mkdir()", "stat()", "unlink()", "remove()",
+"fopen()", "freopen()" directly. Instead use "ws_open()", "ws_rename()",
+"ws_mkdir()", "ws_stat()", "ws_unlink()", "ws_remove()", "ws_fopen()",
+"ws_freopen()": these wrapper functions change the path and file name from
+UTF8 to UTF16 on Windows allowing the functions to work correctly when the
+path or file name contain non-ASCII characters.
+
+When opening a file with "ws_fopen()", "ws_freopen()", or "ws_fdopen()", if
+the file contains ASCII text, use "r", "w", "a", and so on as the open mode
- but if it contains binary data, use "rb", "wb", and so on. On
Windows, if a file is opened in a text mode, writing a byte with the
value of octal 12 (newline) to the file causes two bytes, one with the
carriage return/line feed).
In addition, that also means that when opening or creating a binary
-file, you must use "open()" (with O_CREAT and possibly O_TRUNC if the
-file is to be created if it doesn't exist), and OR in the O_BINARY flag.
+file, you must use "ws_open()" (with O_CREAT and possibly O_TRUNC if the
+file is to be created if it doesn't exist), and OR in the O_BINARY flag.
That flag is not present on most, if not all, UNIX systems, so you must
also do
initialize the array at the point at which it's first declared, so that
the size is known.
+Don't put a comma after the last tuple of an initializer of an array.
+
For #define names and enum member names, prefix the names with a tag so
as to avoid collisions with other names - this might be more of an issue
on Windows, as it appears to #define names such as DELETE and
Don't use the "numbered argument" feature that many UNIX printf's
implement, e.g.:
- sprintf(add_string, " - (%1$d) (0x%1$04x)", value);
+ g_snprintf(add_string, 30, " - (%1$d) (0x%1$04x)", value);
as not all UNIX printf's implement it, and Windows printf doesn't appear
to implement it. Use something like
- sprintf(add_string, " - (%d) (0x%04x)", value, value);
+ g_snprintf(add_string, 30, " - (%d) (0x%04x)", value, value);
instead.
-1.1.2 Name convention.
+Don't use "variadic macros", such as
+
+ #define DBG(format, args...) fprintf(stderr, format, ## args)
+
+as not all C compilers support them. Use macros that take a fixed
+number of arguments, such as
+
+ #define DBG0(format) fprintf(stderr, format)
+ #define DBG1(format, arg1) fprintf(stderr, format, arg1)
+ #define DBG2(format, arg1, arg2) fprintf(stderr, format, arg1, arg2)
+
+ ...
+
+or something such as
+
+ #define DBG(args) printf args
+
+Don't use
+
+ case N ... M:
+
+as that's not supported by all compilers.
+
+snprintf() -> g_snprintf()
+snprintf() is not available on all platforms, so it's a good idea to use the
+g_snprintf() function declared by <glib.h> instead.
+
+tmpnam() -> mkstemp()
+tmpnam is insecure and should not be used any more. Wireshark brings its
+own mkstemp implementation for use on platforms that lack mkstemp.
+Note: mkstemp does not accept NULL as a parameter.
+
+The pointer returned by a call to "tvb_get_ptr()" is not guaranteed to be
+aligned on any particular byte boundary; this means that you cannot
+safely cast it to any data type other than a pointer to "char",
+"unsigned char", "guint8", or other one-byte data types. You cannot,
+for example, safely cast it to a pointer to a structure, and then access
+the structure members directly; on some systems, unaligned accesses to
+integral data types larger than 1 byte, and floating-point data types,
+cause a trap, which will, at best, result in the OS slowly performing an
+unaligned access for you, and will, on at least some platforms, cause
+the program to be terminated.
+
+Wireshark supports platforms with GLib 2.14[.x]/GTK+ 2.12[.x] or newer.
+If a Glib/GTK+ mechanism is available only in Glib/GTK+ versions newer
+than 2.14/2.12 then use "#if GLIB_CHECK_VERSION(...)" or "#if
+GTK_CHECK_VERSION(...)" to conditionally compile code using that
+mechanism.
+
+When different code must be used on UN*X and Win32, use a #if or #ifdef
+that tests _WIN32, not WIN32. Try to write code portably whenever
+possible, however; note that there are some routines in Wireshark with
+platform-dependent implementations and platform-independent APIs, such
+as the routines in epan/filesystem.c, allowing the code that calls it to
+be written portably without #ifdefs.
+
+1.1.2 String handling
+
+Do not use functions such as strcat() or strcpy().
+A lot of work has been done to remove the existing calls to these functions and
+we do not want any new callers of these functions.
+
+Instead use g_snprintf() since that function will if used correctly prevent
+buffer overflows for large strings.
+
+When using a buffer to create a string, do not use a buffer stored on the stack.
+I.e. do not use a buffer declared as
+
+ char buffer[1024];
+
+instead allocate a buffer dynamically using the string-specific or plain emem
+routines (see README.malloc) such as
+
+ emem_strbuf_t *strbuf;
+ strbuf = ep_strbuf_new_label("");
+ ep_strbuf_append_printf(strbuf, ...
+
+or
+
+ char *buffer=NULL;
+ ...
+ #define MAX_BUFFER 1024
+ buffer=ep_alloc(MAX_BUFFER);
+ buffer[0]='\0';
+ ...
+ g_snprintf(buffer, MAX_BUFFER, ...
+
+This avoids the stack from being corrupted in case there is a bug in your code
+that accidentally writes beyond the end of the buffer.
+
+
+If you write a routine that will create and return a pointer to a filled in
+string and if that buffer will not be further processed or appended to after
+the routine returns (except being added to the proto tree),
+do not preallocate the buffer to fill in and pass as a parameter instead
+pass a pointer to a pointer to the function and return a pointer to an
+emem allocated buffer that will be automatically freed. (see README.malloc)
+
+I.e. do not write code such as
+ static void
+ foo_to_str(char *string, ... ){
+ <fill in string>
+ }
+ ...
+ char buffer[1024];
+ ...
+ foo_to_str(buffer, ...
+ proto_tree_add_text(... buffer ...
+
+instead write the code as
+ static void
+ foo_to_str(char **buffer, ...
+ #define MAX_BUFFER x
+ *buffer=ep_alloc(MAX_BUFFER);
+ <fill in *buffer>
+ }
+ ...
+ char *buffer;
+ ...
+ foo_to_str(&buffer, ...
+ proto_tree_add_text(... *buffer ...
+
+Use ep_ allocated buffers. They are very fast and nice. These buffers are all
+automatically free()d when the dissection of the current packet ends so you
+don't have to worry about free()ing them explicitly in order to not leak memory.
+Please read README.malloc.
+
+Don't use non-ASCII characters in source files; not all compiler
+environments will be using the same encoding for non-ASCII characters,
+and at least one compiler (Microsoft's Visual C) will, in environments
+with double-byte character encodings, such as many Asian environments,
+fail if it sees a byte sequence in a source file that doesn't correspond
+to a valid character. This causes source files using either an ISO
+8859/n single-byte character encoding or UTF-8 to fail to compile. Even
+if the compiler doesn't fail, there is no guarantee that the compiler,
+or a developer's text editor, will interpret the characters the way you
+intend them to be interpreted.
+
+1.1.3 Robustness.
+
+Wireshark is not guaranteed to read only network traces that contain correctly-
+formed packets. Wireshark is commonly used to track down networking
+problems, and the problems might be due to a buggy protocol implementation
+sending out bad packets.
+
+Therefore, protocol dissectors not only have to be able to handle
+correctly-formed packets without, for example, crashing or looping
+infinitely, they also have to be able to handle *incorrectly*-formed
+packets without crashing or looping infinitely.
+
+Here are some suggestions for making dissectors more robust in the face
+of incorrectly-formed packets:
+
+Do *NOT* use "g_assert()" or "g_assert_not_reached()" in dissectors.
+*NO* value in a packet's data should be considered "wrong" in the sense
+that it's a problem with the dissector if found; if it cannot do
+anything else with a particular value from a packet's data, the
+dissector should put into the protocol tree an indication that the
+value is invalid, and should return. The "expert" mechanism should be
+used for that purpose.
+
+If there is a case where you are checking not for an invalid data item
+in the packet, but for a bug in the dissector (for example, an
+assumption being made at a particular point in the code about the
+internal state of the dissector), use the DISSECTOR_ASSERT macro for
+that purpose; this will put into the protocol tree an indication that
+the dissector has a bug in it, and will not crash the application.
+
+If you are allocating a chunk of memory to contain data from a packet,
+or to contain information derived from data in a packet, and the size of
+the chunk of memory is derived from a size field in the packet, make
+sure all the data is present in the packet before allocating the buffer.
+Doing so means that:
+
+ 1) Wireshark won't leak that chunk of memory if an attempt to
+ fetch data not present in the packet throws an exception.
-Ethereal uses the underscore_convention rather than the InterCapConvention for
+and
+
+ 2) it won't crash trying to allocate an absurdly-large chunk of
+ memory if the size field has a bogus large value.
+
+If you're fetching into such a chunk of memory a string from the buffer,
+and the string has a specified size, you can use "tvb_get_*_string()",
+which will check whether the entire string is present before allocating
+a buffer for the string, and will also put a trailing '\0' at the end of
+the buffer.
+
+If you're fetching into such a chunk of memory a 2-byte Unicode string
+from the buffer, and the string has a specified size, you can use
+"tvb_get_ephemeral_faked_unicode()", which will check whether the entire
+string is present before allocating a buffer for the string, and will also
+put a trailing '\0' at the end of the buffer. The resulting string will be
+a sequence of single-byte characters; the only Unicode characters that
+will be handled correctly are those in the ASCII range. (Wireshark's
+ability to handle non-ASCII strings is limited; it needs to be
+improved.)
+
+If you're fetching into such a chunk of memory a sequence of bytes from
+the buffer, and the sequence has a specified size, you can use
+"tvb_memdup()", which will check whether the entire sequence is present
+before allocating a buffer for it.
+
+Otherwise, you can check whether the data is present by using
+"tvb_ensure_bytes_exist()" or by getting a pointer to the data by using
+"tvb_get_ptr()", although note that there might be problems with using
+the pointer from "tvb_get_ptr()" (see the item on this in the
+Portability section above, and the next item below).
+
+Note also that you should only fetch string data into a fixed-length
+buffer if the code ensures that no more bytes than will fit into the
+buffer are fetched ("the protocol ensures" isn't good enough, as
+protocol specifications can't ensure only packets that conform to the
+specification will be transmitted or that only packets for the protocol
+in question will be interpreted as packets for that protocol by
+Wireshark). If there's no maximum length of string data to be fetched,
+routines such as "tvb_get_*_string()" are safer, as they allocate a buffer
+large enough to hold the string. (Note that some variants of this call
+require you to free the string once you're finished with it.)
+
+If you have gotten a pointer using "tvb_get_ptr()", you must make sure
+that you do not refer to any data past the length passed as the last
+argument to "tvb_get_ptr()"; while the various "tvb_get" routines
+perform bounds checking and throw an exception if you refer to data not
+available in the tvbuff, direct references through a pointer gotten from
+"tvb_get_ptr()" do not do any bounds checking.
+
+If you have a loop that dissects a sequence of items, each of which has
+a length field, with the offset in the tvbuff advanced by the length of
+the item, then, if the length field is the total length of the item, and
+thus can be zero, you *MUST* check for a zero-length item and abort the
+loop if you see one. Otherwise, a zero-length item could cause the
+dissector to loop infinitely. You should also check that the offset,
+after having the length added to it, is greater than the offset before
+the length was added to it, if the length field is greater than 24 bits
+long, so that, if the length value is *very* large and adding it to the
+offset causes an overflow, that overflow is detected.
+
+If you have a
+
+ for (i = {start}; i < {end}; i++)
+
+loop, make sure that the type of the loop index variable is large enough
+to hold the maximum {end} value plus 1; otherwise, the loop index
+variable can overflow before it ever reaches its maximum value. In
+particular, be very careful when using gint8, guint8, gint16, or guint16
+variables as loop indices; you almost always want to use an "int"/"gint"
+or "unsigned int"/"guint" as the loop index rather than a shorter type.
+
+If you are fetching a length field from the buffer, corresponding to the
+length of a portion of the packet, and subtracting from that length a
+value corresponding to the length of, for example, a header in the
+packet portion in question, *ALWAYS* check that the value of the length
+field is greater than or equal to the length you're subtracting from it,
+and report an error in the packet and stop dissecting the packet if it's
+less than the length you're subtracting from it. Otherwise, the
+resulting length value will be negative, which will either cause errors
+in the dissector or routines called by the dissector, or, if the value
+is interpreted as an unsigned integer, will cause the value to be
+interpreted as a very large positive value.
+
+Any tvbuff offset that is added to as processing is done on a packet
+should be stored in a 32-bit variable, such as an "int"; if you store it
+in an 8-bit or 16-bit variable, you run the risk of the variable
+overflowing.
+
+sprintf() -> g_snprintf()
+Prevent yourself from using the sprintf() function, as it does not test the
+length of the given output buffer and might be writing into unintended memory
+areas. This function is one of the main causes of security problems like buffer
+exploits and many other bugs that are very hard to find. It's much better to
+use the g_snprintf() function declared by <glib.h> instead.
+
+You should test your dissector against incorrectly-formed packets. This
+can be done using the randpkt and editcap utilities that come with the
+Wireshark distribution. Testing using randpkt can be done by generating
+output at the same layer as your protocol, and forcing Wireshark/TShark
+to decode it as your protocol, e.g. if your protocol sits on top of UDP:
+
+ randpkt -c 50000 -t dns randpkt.pcap
+ tshark -nVr randpkt.pcap -d udp.port==53,<myproto>
+
+Testing using editcap can be done using preexisting capture files and the
+"-E" flag, which introduces errors in a capture file. E.g.:
+
+ editcap -E 0.03 infile.pcap outfile.pcap
+ tshark -nVr outfile.pcap
+
+The script fuzz-test.sh is available to help automate these tests.
+
+1.1.4 Name convention.
+
+Wireshark uses the underscore_convention rather than the InterCapConvention for
function names, so new code should probably use underscores rather than
intercaps for functions and variable names. This is especially important if you
are writing code that will be called from outside your code. We are just
-trying to keep things consistent for other users.
+trying to keep things consistent for other developers.
+
+1.1.5 White space convention.
+
+Avoid using tab expansions different from 8 column widths, as not all
+text editors in use by the developers support this. For a detailed
+discussion of tabs, spaces, and indentation, see
+
+ http://www.jwz.org/doc/tabs-vs-spaces.html
+
+When creating a new file, you are free to choose an indentation logic.
+Most of the files in Wireshark tend to use 2-space or 4-space
+indentation. You are encouraged to write a short comment on the
+indentation logic at the beginning of this new file, especially if
+you're using non-mod-8 tabs. The tabs-vs-spaces document above provides
+examples of Emacs and vi modelines for this purpose.
+
+Please do not leave trailing whitespace (spaces/tabs) on lines.
+
+When editing an existing file, try following the existing indentation
+logic and even if it very tempting, never ever use a restyler/reindenter
+utility on an existing file. If you run across wildly varying
+indentation styles within the same file, it might be helpful to send a
+note to wireshark-dev for guidance.
+
+1.1.6 Compiler warnings
+
+You should write code that is free of compiler warnings. Such warnings will
+often indicate questionable code and sometimes even real bugs, so it's best
+to avoid warnings at all.
+
+The compiler flags in the Makefiles are set to "treat warnings as errors",
+so your code won't even compile when warnings occur.
1.2 Skeleton code.
-Ethereal requires certain things when setting up a protocol dissector.
+Wireshark requires certain things when setting up a protocol dissector.
Below is skeleton code for a dissector that you can copy to a file and
fill in. Your dissector should follow the naming convention of packet-
followed by the abbreviated name for the protocol. It is recommended
protocol, if there is one, or a commonly-used abbreviation for the
protocol, if any.
-Dissectors that use the dissector registration to tell a lower level
+Usually, you will put your newly created dissector file into the directory
+epan/dissectors, just like all the other packet-....c files already in there.
+
+Also, please add your dissector file to the corresponding makefiles,
+described in section "1.9 Editing Makefile.common and CMakeLists.txt
+to add your dissector" below.
+
+Dissectors that use the dissector registration to register with a lower level
dissector don't need to define a prototype in the .h file. For other
dissectors the main dissector routine should have a prototype in a header
file whose name is "packet-", followed by the abbreviated name for the
should be changed to include that file.
You may not need to include all the headers listed in the skeleton
-below, and you may need to include additional headers. For example, the
-code inside
-
- #ifdef NEED_SNPRINTF_H
+below, and you may need to include additional headers.
- ...
-
- #endif
+The stdio.h, stdlib.h and string.h header files should be included only as needed.
-is needed only if you are using the "snprintf()" function.
-The "$Id: README.developer,v 1.88 2003/12/30 15:49:12 obiot Exp $"
-in the comment will be updated by CVS when the file is
-checked in; it will allow the RCS "ident" command to report which
-version of the file is currently checked out.
+The "$Id$" in the comment will be updated by Subversion when the file is
+checked in.
-When creating a new file, it is fine to just write "$Id: README.developer,v 1.88 2003/12/30 15:49:12 obiot Exp $" as RCS will
+When creating a new file, it is fine to just write "$Id$" as Subversion will
automatically fill in the identifier at the time the file will be added to the
-CVS repository (checked in).
+SVN repository (committed).
------------------------------------Cut here------------------------------------
/* packet-PROTOABBREV.c
* Routines for PROTONAME dissection
- * Copyright 2000, YOUR_NAME <YOUR_EMAIL_ADDRESS>
+ * Copyright 201x, YOUR_NAME <YOUR_EMAIL_ADDRESS>
*
- * $Id: README.developer,v 1.88 2003/12/30 15:49:12 obiot Exp $
+ * $Id$
*
- * Ethereal - Network traffic analyzer
- * By Gerald Combs <gerald@ethereal.com>
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* Copied from WHATEVER_FILE_YOU_USED (where "WHATEVER_FILE_YOU_USED"
* don't bother with the "Copied from" - you don't even need to put
* in a "Copied from" if you copied an existing dissector, especially
* if the bulk of the code in the new dissector is your code)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
+#if 0
+/* Include only as needed */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#endif
#include <glib.h>
-#ifdef NEED_SNPRINTF_H
-# include "snprintf.h"
-#endif
-
#include <epan/packet.h>
+#include <epan/prefs.h>
/* IF PROTO exposes code to other dissectors, then it must be exported
in a header file. If not, a header file is not needed at all. */
#include "packet-PROTOABBREV.h"
+/* Forward declaration we need below (if using proto_reg_handoff...
+ as a prefs callback) */
+void proto_reg_handoff_PROTOABBREV(void);
+
/* Initialize the protocol and registered fields */
static int proto_PROTOABBREV = -1;
static int hf_PROTOABBREV_FIELDABBREV = -1;
+/* Global sample preference ("controls" display of numbers) */
+static gboolean gPREF_HEX = FALSE;
+/* Global sample port pref */
+static guint gPORT_PREF = 1234;
+
/* Initialize the subtree pointers */
static gint ett_PROTOABBREV = -1;
/* Code to actually dissect the packets */
-static void
+static int
dissect_PROTOABBREV(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
proto_item *ti;
proto_tree *PROTOABBREV_tree;
+/* First, if at all possible, do some heuristics to check if the packet cannot
+ * possibly belong to your protocol. This is especially important for
+ * protocols directly on top of TCP or UDP where port collisions are
+ * common place (e.g., even though your protocol uses a well known port,
+ * someone else may set up, for example, a web server on that port which,
+ * if someone analyzed that web server's traffic in Wireshark, would result
+ * in Wireshark handing an HTTP packet to your dissector). For example:
+ */
+ /* Check that there's enough data */
+ if (tvb_length(tvb) < /* your protocol's smallest packet size */)
+ return 0;
+
+ /* Get some values from the packet header, probably using tvb_get_*() */
+ if ( /* these values are not possible in PROTONAME */ )
+ /* This packet does not appear to belong to PROTONAME.
+ * Return 0 to give another dissector a chance to dissect it.
+ */
+ return 0;
+
/* Make entries in Protocol column and Info column on summary display */
- if (check_col(pinfo->cinfo, COL_PROTOCOL))
- col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
-
-/* This field shows up as the "Info" column in the display; you should make
- it, if possible, summarize what's in the packet, so that a user looking
+ col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
+
+/* This field shows up as the "Info" column in the display; you should use
+ it, if possible, to summarize what's in the packet, so that a user looking
at the list of packets can tell what type of packet it is. See section 1.5
for more information.
- If you are setting it to a constant string, use "col_set_str()", as
- it's more efficient than the other "col_set_XXX()" calls.
+ If you are setting the column to a constant string, use "col_set_str()",
+ as it's more efficient than the other "col_set_XXX()" calls.
If you're setting it to a string you've constructed, or will be
appending to the column later, use "col_add_str()".
past the end of the packet, so that the Info column doesn't have data
left over from the previous dissector; do
- if (check_col(pinfo->cinfo, COL_INFO))
- col_clear(pinfo->cinfo, COL_INFO);
+ col_clear(pinfo->cinfo, COL_INFO);
*/
- if (check_col(pinfo->cinfo, COL_INFO))
- col_set_str(pinfo->cinfo, COL_INFO, "XXX Request");
+ col_set_str(pinfo->cinfo, COL_INFO, "XXX Request");
-/* A protocol dissector can be called in 2 different ways:
+/* A protocol dissector may be called in 2 different ways - with, or
+ without a non-null "tree" argument.
- (a) Operational dissection
-
- In this mode, Ethereal is only interested in the way protocols
- interact, protocol conversations are created, packets are reassembled
- and handed over to higher-level protocol dissectors.
- This way Ethereal does not build a so-called "protocol tree".
-
- (b) Detailed dissection
-
- In this mode, Ethereal is also interested in all details of a given
- protocol, so a "protocol tree" is created.
-
- Ethereal distinguishes between the 2 modes with the proto_tree pointer:
- (a) <=> tree == NULL
- (b) <=> tree != NULL
+ If the proto_tree argument is null, Wireshark does not need to use
+ the protocol tree information from your dissector, and therefore is
+ passing the dissector a null "tree" argument so that it doesn't
+ need to do work necessary to build the protocol tree.
In the interest of speed, if "tree" is NULL, avoid building a
- protocol tree and adding stuff to it if possible. Note,
- however, that you must call subdissectors regardless of whether
- "tree" is NULL or not. */
+ protocol tree and adding stuff to it, or even looking at any packet
+ data needed only if you're building the protocol tree, if possible.
+
+ Note, however, that you must fill in column information, create
+ conversations, reassemble packets, build any other persistent state
+ needed for dissection, and call subdissectors regardless of whether
+ "tree" is NULL or not. This might be inconvenient to do without
+ doing most of the dissection work; the routines for adding items to
+ the protocol tree can be passed a null protocol tree pointer, in
+ which case they'll return a null item pointer, and
+ "proto_item_add_subtree()" returns a null tree pointer if passed a
+ null item pointer, so, if you're careful not to dereference any null
+ tree or item pointers, you can accomplish this by doing all the
+ dissection work. This might not be as efficient as skipping that
+ work if you're not building a protocol tree, but if the code would
+ have a lot of tests whether "tree" is null if you skipped that work,
+ you might still be better off just doing all that work regardless of
+ whether "tree" is null or not.
+
+ Note also that there is no guarantee, the first time the dissector is
+ called, whether "tree" will be null or not; your dissector must work
+ correctly, building or updating whatever state information is
+ necessary, in either case. */
if (tree) {
/* NOTE: The offset and length values in the call to
offset to the end of the packet. */
/* create display subtree for the protocol */
- ti = proto_tree_add_item(tree, proto_PROTOABBREV, tvb, 0, -1, FALSE);
+ ti = proto_tree_add_item(tree, proto_PROTOABBREV, tvb, 0, -1, ENC_NA);
PROTOABBREV_tree = proto_item_add_subtree(ti, ett_PROTOABBREV);
/* add an item to the subtree, see section 1.6 for more information */
proto_tree_add_item(PROTOABBREV_tree,
- hf_PROTOABBREV_FIELDABBREV, tvb, offset, len, FALSE)
+ hf_PROTOABBREV_FIELDABBREV, tvb, offset, len, ENC_xxx);
/* Continue adding tree items to process the packet here */
}
/* If this protocol has a sub-dissector call it here, see section 1.8 */
+
+/* Return the amount of data this dissector was able to dissect */
+ return tvb_length(tvb);
}
-/* Register the protocol with Ethereal */
+/* Register the protocol with Wireshark */
/* this format is require because a script is used to build the C function
that calls all the protocol registration.
void
proto_register_PROTOABBREV(void)
-{
+{
+ module_t *PROTOABBREV_module;
/* Setup list of header fields See Section 1.6.1 for details*/
static hf_register_info hf[] = {
{ &hf_PROTOABBREV_FIELDABBREV,
{ "FIELDNAME", "PROTOABBREV.FIELDABBREV",
- FIELDTYPE, FIELDBASE, FIELDCONVERT, BITMASK,
- "FIELDDESCR" }
- },
+ FIELDTYPE, FIELDDISPLAY, FIELDCONVERT, BITMASK,
+ "FIELDDESCR", HFILL }
+ }
};
/* Setup protocol subtree array */
static gint *ett[] = {
- &ett_PROTOABBREV,
+ &ett_PROTOABBREV
};
/* Register the protocol name and description */
/* Required function calls to register the header fields and subtrees used */
proto_register_field_array(proto_PROTOABBREV, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
+
+/* Register preferences module (See Section 2.6 for more on preferences) */
+/* (Registration of a prefs callback is not required if there are no */
+/* prefs-dependent registration functions (eg: a port pref). */
+/* See proto_reg_handoff below. */
+/* If a prefs callback is not needed, use NULL instead of */
+/* proto_reg_handoff_PROTOABBREV in the following). */
+ PROTOABBREV_module = prefs_register_protocol(proto_PROTOABBREV,
+ proto_reg_handoff_PROTOABBREV);
+
+/* Register preferences module under preferences subtree.
+ Use this function instead of prefs_register_protocol if you want to group
+ preferences of several protocols under one preferences subtree.
+ Argument subtree identifies grouping tree node name, several subnodes can be
+ specified usign slash '/' (e.g. "OSI/X.500" - protocol preferences will be
+ accessible under Protocols->OSI->X.500-><PROTOSHORTNAME> preferences node.
+*/
+ PROTOABBREV_module = prefs_register_protocol_subtree(const char *subtree,
+ proto_PROTOABBREV, proto_reg_handoff_PROTOABBREV);
+
+/* Register a sample preference */
+ prefs_register_bool_preference(PROTOABBREV_module, "show_hex",
+ "Display numbers in Hex",
+ "Enable to display numerical values in hexadecimal.",
+ &gPREF_HEX);
+
+/* Register a sample port preference */
+ prefs_register_uint_preference(PROTOABBREV_module, "tcp.port", "PROTOABBREV TCP Port",
+ " PROTOABBREV TCP port if other than the default",
+ 10, &gPORT_PREF);
}
/* If this dissector uses sub-dissector registration add a registration routine.
- This format is required because a script is used to find these routines and
- create the code that calls these routines.
+ This exact format is required because a script is used to find these
+ routines and create the code that calls these routines.
+
+ If this function is registered as a prefs callback (see prefs_register_protocol
+ above) this function is also called by preferences whenever "Apply" is pressed;
+ In that case, it should accommodate being called more than once.
+
+ This form of the reg_handoff function is used if if you perform
+ registration functions which are dependent upon prefs. See below
+ for a simpler form which can be used if there are no
+ prefs-dependent registration functions.
*/
+void
+proto_reg_handoff_PROTOABBREV(void)
+{
+ static gboolean initialized = FALSE;
+ static dissector_handle_t PROTOABBREV_handle;
+ static int currentPort;
+
+ if (!initialized) {
+
+/* Use new_create_dissector_handle() to indicate that dissect_PROTOABBREV()
+ * returns the number of bytes it dissected (or 0 if it thinks the packet
+ * does not belong to PROTONAME).
+ */
+ PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV,
+ proto_PROTOABBREV);
+ initialized = TRUE;
+ } else {
+
+ /*
+ If you perform registration functions which are dependent upon
+ prefs the you should de-register everything which was associated
+ with the previous settings and re-register using the new prefs
+ settings here. In general this means you need to keep track of
+ the PROTOABBREV_handle and the value the preference had at the time
+ you registered. The PROTOABBREV_handle value and the value of the
+ preference can be saved using local statics in this
+ function (proto_reg_handoff).
+ */
+
+ dissector_delete_uint("tcp.port", currentPort, PROTOABBREV_handle);
+ }
+
+ currentPort = gPORT_PREF;
+
+ dissector_add_uint("tcp.port", currentPort, PROTOABBREV_handle);
+
+}
+
+#if 0
+/* Simple form of proto_reg_handoff_PROTOABBREV which can be used if there are
+ no prefs-dependent registration function calls.
+ */
+
void
proto_reg_handoff_PROTOABBREV(void)
{
dissector_handle_t PROTOABBREV_handle;
- PROTOABBREV_handle = create_dissector_handle(dissect_PROTOABBREV,
- proto_PROTOABBREV);
- dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
+/* Use new_create_dissector_handle() to indicate that dissect_PROTOABBREV()
+ * returns the number of bytes it dissected (or 0 if it thinks the packet
+ * does not belong to PROTONAME).
+ */
+ PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV,
+ proto_PROTOABBREV);
+ dissector_add_uint("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
}
+#endif
+
+
+/*
+ * Editor modelines - http://www.wireshark.org/tools/modelines.html
+ *
+ * Local variables:
+ * c-basic-offset: 4
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
+ * :indentSize=4:tabSize=8:noTabs=true:
+ */
+
------------------------------------Cut here------------------------------------
top-level protocol tree item for that protocol.
PROTOSHORTNAME An abbreviated name for the protocol; this is displayed
in the "Preferences" dialog box if your dissector has
- any preferences, and in the dialog box for filter fields
- when constructing a filter expression.
+ any preferences, in the dialog box of enabled protocols,
+ and in the dialog box for filter fields when constructing
+ a filter expression.
PROTOABBREV A name for the protocol for use in filter expressions;
- it should contain only lower-case letters, digits, and
+ it shall contain only lower-case letters, digits, and
hyphens.
FIELDNAME The displayed name for the header field.
FIELDABBREV The abbreviated name for the header field. (NO SPACES)
FIELDTYPE FT_NONE, FT_BOOLEAN, FT_UINT8, FT_UINT16, FT_UINT24,
FT_UINT32, FT_UINT64, FT_INT8, FT_INT16, FT_INT24, FT_INT32,
FT_INT64, FT_FLOAT, FT_DOUBLE, FT_ABSOLUTE_TIME,
- FT_RELATIVE_TIME, FT_STRING, FT_STRINGZ, FT_UINT_STRING,
- FT_ETHER, FT_BYTES, FT_IPv4, FT_IPv6, FT_IPXNET,
- FT_FRAMENUM
-FIELDBASE BASE_NONE, BASE_DEC, BASE_HEX, BASE_OCT
-FIELDCONVERT VALS(x), TFS(x), NULL
+ FT_RELATIVE_TIME, FT_STRING, FT_STRINGZ, FT_EUI64,
+ FT_UINT_STRING, FT_ETHER, FT_BYTES, FT_UINT_BYTES, FT_IPv4,
+ FT_IPv6, FT_IPXNET, FT_FRAMENUM, FT_PROTOCOL, FT_GUID, FT_OID
+FIELDDISPLAY For FT_UINT{8,16,24,32,64} and FT_INT{8,16,24,32,64):
+
+ BASE_DEC, BASE_HEX, BASE_OCT, BASE_DEC_HEX, BASE_HEX_DEC,
+ or BASE_CUSTOM, possibly ORed with BASE_RANGE_STRING
+
+ For FT_ABSOLUTE_TIME:
+
+ ABSOLUTE_TIME_LOCAL, ABSOLUTE_TIME_UTC, or
+ ABSOLUTE_TIME_DOY_UTC
+
+ For FT_BOOLEAN if BITMASK is non-zero:
+
+ Number of bits in the field containing the FT_BOOLEAN
+ bitfield
+
+ For all other types:
+
+ BASE_NONE
+FIELDCONVERT VALS(x), RVALS(x), TFS(x), NULL
BITMASK Usually 0x0 unless using the TFS(x) field conversion.
-FIELDDESCR A brief description of the field.
+FIELDDESCR A brief description of the field, or NULL. [Please do not use ""].
PARENT_SUBFIELD Lower level protocol field used for lookup, i.e. "tcp.port"
ID_VALUE Lower level protocol field value that identifies this protocol
For example the TCP or UDP port number
register itself with the lower level dissector, or if the protocol dissector
wants/needs to expose code to other subdissectors.
-The dissector has the following header that must be placed into
-packet-PROTOABBREV.h.
+The dissector must be declared exactly as follows in the file
+packet-PROTOABBREV.h:
-void
+int
dissect_PROTOABBREV(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree);
1.4.2 Extracting data from packets.
-NOTE: See the README.tvbuff for more details
+NOTE: See the file /epan/tvbuff.h for more details.
The "tvb" argument to a dissector points to a buffer containing the raw
data to be analyzed by the dissector; for example, for a protocol
running atop UDP, it contains the UDP payload (but not the UDP header,
-or any protocol headers above it). A tvbuffer is a opaque data
+or any protocol headers above it). A tvbuffer is an opaque data
structure, the internal data structures are hidden and the data must be
-access via the tvbuffer accessors.
+accessed via the tvbuffer accessors.
The accessors are:
+Bit accessors for a maximum of 8-bits, 16-bits 32-bits and 64-bits:
+
+guint8 tvb_get_bits8(tvbuff_t *tvb, gint bit_offset, gint no_of_bits);
+guint16 tvb_get_bits16(tvbuff_t *tvb, gint bit_offset, gint no_of_bits,gboolean little_endian);
+guint32 tvb_get_bits32(tvbuff_t *tvb, gint bit_offset, gint no_of_bits,gboolean little_endian);
+guint64 tvb_get_bits64(tvbuff_t *tvb, gint bit_offset, gint no_of_bits,gboolean little_endian);
+
Single-byte accessor:
guint8 tvb_get_guint8(tvbuff_t*, gint offset);
-Network-to-host-order access for 16-bit integers (guint16), 32-bit
-integers (guint32), and 24-bit integers:
+Network-to-host-order accessors for 16-bit integers (guint16), 24-bit
+integers, 32-bit integers (guint32), and 64-bit integers (guint64):
guint16 tvb_get_ntohs(tvbuff_t*, gint offset);
-guint32 tvb_get_ntohl(tvbuff_t*, gint offset);
guint32 tvb_get_ntoh24(tvbuff_t*, gint offset);
+guint32 tvb_get_ntohl(tvbuff_t*, gint offset);
+guint64 tvb_get_ntoh40(tvbuff_t*, gint offset);
+guint64 tvb_get_ntoh48(tvbuff_t*, gint offset);
+guint64 tvb_get_ntoh56(tvbuff_t*, gint offset);
+guint64 tvb_get_ntoh64(tvbuff_t*, gint offset);
-Network-to-host-order access for single-precision and double-precision
-IEEE floating-point numbers:
+Network-to-host-order accessors for single-precision and
+double-precision IEEE floating-point numbers:
gfloat tvb_get_ntohieee_float(tvbuff_t*, gint offset);
gdouble tvb_get_ntohieee_double(tvbuff_t*, gint offset);
-Little-Endian-to-host-order access for 16-bit integers (guint16), 32-bit
-integers (guint32), and 24-bit integers:
+Little-Endian-to-host-order accessors for 16-bit integers (guint16),
+24-bit integers, 32-bit integers (guint32), and 64-bit integers
+(guint64):
guint16 tvb_get_letohs(tvbuff_t*, gint offset);
-guint32 tvb_get_letohl(tvbuff_t*, gint offset);
guint32 tvb_get_letoh24(tvbuff_t*, gint offset);
+guint32 tvb_get_letohl(tvbuff_t*, gint offset);
+guint64 tvb_get_letoh40(tvbuff_t*, gint offset);
+guint64 tvb_get_letoh48(tvbuff_t*, gint offset);
+guint64 tvb_get_letoh56(tvbuff_t*, gint offset);
+guint64 tvb_get_letoh64(tvbuff_t*, gint offset);
-Little-Endian-to-host-order access for single-precision and
+Little-Endian-to-host-order accessors for single-precision and
double-precision IEEE floating-point numbers:
gfloat tvb_get_letohieee_float(tvbuff_t*, gint offset);
gdouble tvb_get_letohieee_double(tvbuff_t*, gint offset);
+Accessors for IPv4 and IPv6 addresses:
+
+guint32 tvb_get_ipv4(tvbuff_t*, gint offset);
+void tvb_get_ipv6(tvbuff_t*, gint offset, struct e_in6_addr *addr);
+
NOTE: IPv4 addresses are not to be converted to host byte order before
-being passed to "proto_tree_add_ipv4()". You should use "tvb_memcpy()"
+being passed to "proto_tree_add_ipv4()". You should use "tvb_get_ipv4()"
to fetch them, not "tvb_get_ntohl()" *OR* "tvb_get_letohl()" - don't,
for example, try to use "tvb_get_ntohl()", find that it gives you the
wrong answer on the PC on which you're doing development, and try
"tvb_get_letohl()" instead, as "tvb_get_letohl()" will give the wrong
answer on big-endian machines.
+Accessors for GUID:
+
+void tvb_get_ntohguid(tvbuff_t *, gint offset, e_guid_t *guid);
+void tvb_get_letohguid(tvbuff_t *, gint offset, e_guid_t *guid);
+
+String accessors:
+
+guint8 *tvb_get_string(tvbuff_t*, gint offset, gint length);
+gchar *tvb_get_unicode_string(tvbuff_t *tvb, const gint offset, gint length, const guint encoding);
+guint8 *tvb_get_ephemeral_string(tvbuff_t*, gint offset, gint length);
+gchar *tvb_get_ephemeral_unicode_string(tvbuff_t *tvb, const gint offset, gint length, const guint encoding);
+guint8 *tvb_get_seasonal_string(tvbuff_t*, gint offset, gint length);
+
+Returns a null-terminated buffer containing data from the specified
+tvbuff, starting at the specified offset, and containing the specified
+length worth of characters (the length of the buffer will be length+1,
+as it includes a null character to terminate the string).
+
+tvb_get_string() returns a buffer allocated by g_malloc() so you must
+g_free() it when you are finished with the string. Failure to g_free() this
+buffer will lead to memory leaks.
+
+tvb_get_unicode_string() is a unicode (UTF-16) version of above. This
+is intended for reading UTF-16 unicode strings out of a tvbuff and
+returning them as a UTF-8 string for use in Wireshark. The offset and
+returned length pointer are in bytes, not UTF-16 characters.
+
+tvb_get_ephemeral_string() returns a buffer allocated from a special heap
+with a lifetime until the next packet is dissected. You do not need to
+free() this buffer, it will happen automatically once the next packet is
+dissected.
+
+tvb_get_ephemeral_unicode_string() is a unicode (UTF-16) version of above.
+This is intended for reading UTF-16 unicode strings out of a tvbuff and
+returning them as a UTF-8 string for use in Wireshark. The offset and
+returned length pointer are in bytes, not UTF-16 characters.
+
+tvb_get_seasonal_string() returns a buffer allocated from a special heap
+with a lifetime of the current capture session. You do not need to
+free() this buffer, it will happen automatically once the a new capture or
+file is opened.
+
+guint8 *tvb_get_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
+const guint8 *tvb_get_const stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
+guint8 *tvb_get_ephemeral_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
+gchar *tvb_get_ephemeral_unicode_stringz(tvbuff_t *tvb, const gint offset, gint *lengthp, const guint encoding);
+guint8 *tvb_get_seasonal_stringz(tvbuff_t *tvb, gint offset, gint *lengthp);
+
+Returns a null-terminated buffer containing data from the specified tvbuff,
+starting at the specified offset, and containing all characters from the
+tvbuff up to and including a terminating null character in the tvbuff.
+"*lengthp" will be set to the length of the string, including the terminating
+null.
+
+tvb_get_stringz() returns a buffer allocated by g_malloc() so you must
+g_free() it when you are finished with the string. Failure to g_free() this
+buffer will lead to memory leaks.
+
+tvb_get_const_stringz() returns a pointer to the (const) string in the tvbuff.
+You do not need to free() this buffer, it will happen automatically once the
+next packet is dissected. This function is slightly more efficient than the
+others because it does not allocate memory and copy the string.
+
+tvb_get_ephemeral_stringz() returns a buffer allocated from a special heap
+with a lifetime until the next packet is dissected. You do not need to
+free() this buffer, it will happen automatically once the next packet is
+dissected.
+
+tvb_get_ephemeral_unicode_stringz() is a unicode (UTF-16) version of
+above. This is intended for reading UTF-16 unicode strings out of a tvbuff
+and returning them as a UTF-8 string for use in Wireshark. The offset and
+returned length pointer are in bytes, not UTF-16 characters.
+
+tvb_get_seasonal_stringz() returns a buffer allocated from a special heap
+with a lifetime of the current capture session. You do not need to
+free() this buffer, it will happen automatically once the a new capture or
+file is opened.
+
+tvb_fake_unicode() has been superseded by tvb_get_unicode_string(), which
+properly handles Unicode (UTF-16) strings by converting them to UTF-8.
+
+tvb_get_ephemeral_faked_unicode() has been superseded by
+tvb_get_ephemeral_string(), which properly handles Unicode (UTF-16) strings by
+converting them to UTF-8.
+
+Byte Array Accessors:
+
+gchar *tvb_bytes_to_str(tvbuff_t *tvb, gint offset, gint len);
+
+Formats a bunch of data from a tvbuff as bytes, returning a pointer
+to the string with the data formatted as two hex digits for each byte.
+The string pointed to is stored in an "ep_alloc'd" buffer which will be freed
+before the next frame is dissected. The formatted string will contain the hex digits
+for at most the first 16 bytes of the data. If len is greater than 16 bytes, a
+trailing "..." will be added to the string.
+
+gchar *tvb_bytes_to_str_punct(tvbuff_t *tvb, gint offset, gint len, gchar punct);
+
+This function is similar to tvb_bytes_to_str(...) except that 'punct' is inserted
+between the hex representation of each byte.
+
+gchar *tvb_bcd_dig_to_ep_str(tvbuff_t *tvb, const gint offset, const gint len, dgt_set_t *dgt, gboolean skip_first);
+
+Given a tvbuff, an offset into the tvbuff, and a length that starts
+at that offset (which may be -1 for "all the way to the end of the
+tvbuff"), fetch BCD encoded digits from a tvbuff starting from either
+the low or high half byte, formating the digits according to an input digit set,
+if NUll a default digit set of 0-9 returning "?" for overdecadic digits will be used.
+A pointer to the EP allocated string will be returned.
+Note: a tvbuff content of 0xf is considered a 'filler' and will end the conversion.
+
Copying memory:
guint8* tvb_memcpy(tvbuff_t*, guint8* target, gint offset, gint length);
+
+Copies into the specified target the specified length's worth of data
+from the specified tvbuff, starting at the specified offset.
+
guint8* tvb_memdup(tvbuff_t*, gint offset, gint length);
+guint8* ep_tvb_memdup(tvbuff_t*, gint offset, gint length);
+Returns a buffer, allocated with "g_malloc()", containing the specified
+length's worth of data from the specified tvbuff, starting at the
+specified offset. The ephemeral variant is freed automatically after the
+packet is dissected.
Pointer-retrieval:
/* WARNING! This function is possibly expensive, temporarily allocating
* another copy of the packet data. Furthermore, it's dangerous because once
* this pointer is given to the user, there's no guarantee that the user will
* honor the 'length' and not overstep the boundaries of the buffer.
- */
+ */
guint8* tvb_get_ptr(tvbuff_t*, gint offset, gint length);
-The reason that tvb_get_ptr() have to allocate a copy of its data only
-occurs with TVBUFF_COMPOSITES, data that spans multiple tvbuffers. If the
-user request a pointer to a range of bytes that spans the member tvbuffs that
-make up the TVBUFF_COMPOSITE, the data will have to be copied to another
-memory region to assure that all the bytes are contiguous.
+The reason that tvb_get_ptr() might have to allocate a copy of its data
+only occurs with TVBUFF_COMPOSITES, data that spans multiple tvbuffers.
+If the user requests a pointer to a range of bytes that span the member
+tvbuffs that make up the TVBUFF_COMPOSITE, the data will have to be
+copied to another memory region to assure that all the bytes are
+contiguous.
field, typically giving an abbreviated name for the protocol (but not
the all-lower-case abbreviation used elsewhere) is COL_PROTOCOL, and the
COL_ value for the "Info" field, giving a summary of the contents of the
-packet for that protocol, is COL_INFO.
-
-A value for a column should only be added if the user specified that it
-be displayed; to check whether a given column is to be displayed, call
-'check_col' with the COL_ value for that field as an argument - it will
-return TRUE if the column is to be displayed and FALSE if it is not to
-be displayed.
+packet for that protocol, is COL_INFO.
The value for a column can be specified with one of several functions,
all of which take the 'fd' argument to the dissector as their first
For example, to set the "Protocol" column
to "PROTOABBREV":
- if (check_col(pinfo->cinfo, COL_PROTOCOL))
- col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
+ col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
1.5.2 The col_add_str function.
string containing the type of the request in the packet and "n" is an
unsigned integer containing the number of bytes in the request:
- if (check_col(pinfo->cinfo, COL_INFO))
- col_add_fstr(pinfo->cinfo, COL_INFO, "%s request, %u bytes",
- reqtype, n);
+ col_add_fstr(pinfo->cinfo, COL_INFO, "%s request, %u bytes",
+ reqtype, n);
Don't use 'col_add_fstr' with a format argument of just "%s" -
'col_add_str', or possibly even 'col_set_str' if the string that matches
current value for the column, rather than replacing the value for that
column.
+1.5.7 The col_append_sep_str and col_append_sep_fstr functions.
+
+In specific situations the developer knows that a column's value will be
+created in a stepwise manner, where the appended values are listed. Both
+'col_append_sep_str' and 'col_append_sep_fstr' functions will add an item
+separator between two consecutive items, and will not add the separator at the
+beginning of the column. The remainder of the work both functions do is
+identical to what 'col_append_str' and 'col_append_fstr' do.
+
+1.5.8 The col_set_fence and col_prepend_fence_fstr functions.
+
+Sometimes a dissector may be called multiple times for different PDUs in the
+same frame (for example in the case of SCTP chunk bundling: several upper
+layer data packets may be contained in one SCTP packet). If the upper layer
+dissector calls 'col_set_str()' or 'col_clear()' on the Info column when it
+begins dissecting each of those PDUs then when the frame is fully dissected
+the Info column would contain only the string from the last PDU in the frame.
+The 'col_set_fence' function erects a "fence" in the column that prevents
+subsequent 'col_...' calls from clearing the data currently in that column.
+For example, the SCTP dissector calls 'col_set_fence' on the Info column
+after it has called any subdissectors for that chunk so that subdissectors
+of any subsequent chunks may only append to the Info column.
+'col_prepend_fence_fstr' prepends data before a fence (moving it if
+necessary). It will create a fence at the end of the prepended data if the
+fence does not already exist.
+
+
+1.5.9 The col_set_time function.
+
+The 'col_set_time' function takes an nstime value as its third argument.
+This nstime value is a relative value and will be added as such to the
+column. The fourth argument is the filtername holding this value. This
+way, rightclicking on the column makes it possible to build a filter
+based on the time-value.
+
+For example:
+
+ nstime_delta(&ts, &pinfo->fd->abs_ts, &tcpd->ts_first);
+ col_set_time(pinfo->cinfo, COL_REL_CONV_TIME, &ts, "tcp.time_relative");
+
1.6 Constructing the protocol tree.
to the tree.
When a packet is selected in the packet-list pane, or a packet popup
-window is created, a new logical protocol tree (proto_tree) is created.
+window is created, a new logical protocol tree (proto_tree) is created.
The pointer to the proto_tree (in this case, 'protocol tree'), is passed
to the top-level protocol dissector, and then to all subsequent protocol
dissectors for that packet, and then the GUI tree is drawn via
proto_tree_draw().
-The logical proto_tree needs to know detailed information about the
-protocols and fields about which information will be collected from the
-dissection routines. By strictly defining (or "typing") the data that can
-be attached to a proto tree, searching and filtering becomes possible.
-This means that the for every protocol and field (which I also call
-"header fields", since they are fields in the protocol headers) which
-might be attached to a tree, some information is needed.
+The logical proto_tree needs to know detailed information about the protocols
+and fields about which information will be collected from the dissection
+routines. By strictly defining (or "typing") the data that can be attached to a
+proto tree, searching and filtering becomes possible. This means that for
+every protocol and field (which I also call "header fields", since they are
+fields in the protocol headers) which might be attached to a tree, some
+information is needed.
Every dissector routine will need to register its protocols and fields
with the central protocol routines (in proto.c). At first I thought I
protocol dissectors (perhaps even user-supplied) is feasible.
To do this, each protocol should have a register routine, which will be
-called when Ethereal starts. The code to call the register routines is
+called when Wireshark starts. The code to call the register routines is
generated automatically; to arrange that a protocol's register routine
be called at startup:
the file containing a dissector's "register" routine must be
- added to "DISSECTOR_SRC" in "Makefile.am" and "Makefile.nmake";
-
+ added to "DISSECTOR_SRC" in "epan/dissectors/Makefile.common"
+ (and in "epan/CMakeLists.txt");
+
the "register" routine must have a name of the form
"proto_register_XXX";
-
+
the "register" routine must take no argument, and return no
value;
-
+
the "register" routine's name must appear in the source file
either at the beginning of the line, or preceded only by "void "
- at the beginning of the line (that'd typically be the
+ at the beginning of the line (that would typically be the
definition) - other white space shouldn't cause a problem, e.g.:
-
+
void proto_register_XXX(void) {
-
+
...
-
+
}
-
+
and
-
+
void
proto_register_XXX( void )
{
-
+
...
-
+
}
-
+
and so on should work.
For every protocol or field that a dissector wants to register, a variable of
Here is how the frame "protocol" is registered.
- int proto_frame;
+ int proto_frame;
proto_frame = proto_register_protocol (
/* name */ "Frame",
/* abbrev */ "frame" );
A header field is also registered with its name and abbreviation, but
-information about the its data type is needed. It helps to look at
+information about its data type is needed. It helps to look at
the header_field_info struct to see what information is expected:
struct header_field_info {
- char *name;
- char *abbrev;
+ const char *name;
+ const char *abbrev;
enum ftenum type;
int display;
- void *strings;
- guint bitmask;
- char *blurb;
-
- int id; /* calculated */
- int parent;
- int bitshift; /* calculated */
+ const void *strings;
+ guint32 bitmask;
+ const char *blurb;
+ .....
};
name
----
A string representing the name of the field. This is the name
-that will appear in the graphical protocol tree.
+that will appear in the graphical protocol tree. It must be a non-empty
+string.
abbrev
------
has multiple error fields, so the abbreviations follow this pattern:
"trmac.errors.iso", "trmac.errors.noniso", etc.
-The abbreviation is the identifier used in a display filter.
+The abbreviation is the identifier used in a display filter. If it is
+an empty string then the field will not be filterable.
type
----
subtree below it containing fields for
the members of the array, might be an
FT_NONE field.
+ FT_PROTOCOL Used for protocols which will be placing
+ themselves as top-level items in the
+ "Packet Details" pane of the UI.
FT_BOOLEAN 0 means "false", any other value means
"true".
FT_FRAMENUM A frame number; if this is used, the "Go
FT_INT64 A 64-bit signed integer.
FT_FLOAT A single-precision floating point number.
FT_DOUBLE A double-precision floating point number.
- FT_ABSOLUTE_TIME Seconds (4 bytes) and nanoseconds (4 bytes)
- of time displayed as month name, month day,
- year, hours, minutes, and seconds with 9
- digits after the decimal point.
+ FT_ABSOLUTE_TIME An absolute time from some fixed point in time,
+ displayed as the date, followed by the time, as
+ hours, minutes, and seconds with 9 digits after
+ the decimal point.
FT_RELATIVE_TIME Seconds (4 bytes) and nanoseconds (4 bytes)
- of time displayed as seconds and 9 digits
+ of time relative to an arbitrary time.
+ displayed as seconds and 9 digits
after the decimal point.
FT_STRING A string of characters, not necessarily
NUL-terminated, but possibly NUL-padded.
types, are to be used for text strings,
not raw binary data.
FT_STRINGZ A NUL-terminated string of characters.
+ The string length is normally the length
+ given in the proto_tree_add_item() call.
+ However if the length given in the call
+ is -1, then the length used is that
+ returned by calling tvb_strsize().
FT_UINT_STRING A counted string of characters, consisting
- of a count (represented as an integral
- value) followed immediately by the
- specified number of characters.
+ of a count (represented as an integral value,
+ of width given in the proto_tree_add_item()
+ call) followed immediately by that number of
+ characters.
FT_ETHER A six octet string displayed in
Ethernet-address format.
FT_BYTES A string of bytes with arbitrary values;
used for raw binary data.
+ FT_UINT_BYTES A counted string of bytes, consisting
+ of a count (represented as an integral value,
+ of width given in the proto_tree_add_item()
+ call) followed immediately by that number of
+ arbitrary values; used for raw binary data.
FT_IPv4 A version 4 IP address (4 bytes) displayed
in dotted-quad IP address format (4
decimal numbers separated by dots).
in standard IPv6 address format.
FT_IPXNET An IPX address displayed in hex as a 6-byte
network number followed by a 6-byte station
- address.
+ address.
+ FT_GUID A Globally Unique Identifier
+ FT_OID An ASN.1 Object Identifier
+ FT_EUI64 A EUI-64 Address
Some of these field types are still not handled in the display filter
routines, but the most common ones are. The FT_UINT* variables all
signed integers; the number on the end represent how many bits are used
to represent the number.
+Some constraints are imposed on the header fields depending on the type
+(e.g. FT_BYTES) of the field. Fields of type FT_ABSOLUTE_TIME must use
+'ABSOLUTE_TIME_{LOCAL,UTC,DOY_UTC}, NULL, 0x0' as values for the
+'display, 'strings', and 'bitmask' fields, and all other non-integral
+types (i.e.. types that are _not_ FT_INT* and FT_UINT*) must use
+'BASE_NONE, NULL, 0x0' as values for the 'display', 'strings', 'bitmask'
+fields. The reason is simply that the type itself implictly defines the
+nature of 'display', 'strings', 'bitmask'.
+
display
-------
The display field has a couple of overloaded uses. This is unfortunate,
-but since we're C as an application programming language, this sometimes
+but since we're using C as an application programming language, this sometimes
makes for cleaner programs. Right now I still think that overloading
this variable was okay.
BASE_DEC,
BASE_HEX,
- BASE_OCT
+ BASE_OCT,
+ BASE_DEC_HEX,
+ BASE_HEX_DEC,
+ BASE_CUSTOM
BASE_DEC, BASE_HEX, and BASE_OCT are decimal, hexadecimal, and octal,
-respectively.
+respectively. BASE_DEC_HEX and BASE_HEX_DEC display value in two bases
+(the 1st representation followed by the 2nd in parenthesis).
+
+BASE_CUSTOM allows one to specify a callback function pointer that will
+format the value. The function pointer of the same type as defined by
+custom_fmt_func_t in epan/proto.h, specifically:
+
+ void func(gchar *, guint32);
+
+The first argument is a pointer to a buffer of the ITEM_LABEL_LENGTH size
+and the second argument is the value to be formatted.
-For FT_BOOLEAN fields that are also bitfields, 'display' is used to tell
-the proto_tree how wide the parent bitfield is. With integers this is
-not needed since the type of integer itself (FT_UINT8, FT_UINT16,
-FT_UINT24, FT_UINT32, etc.) tells the proto_tree how wide the parent
-bitfield is.
+For FT_BOOLEAN fields that are also bitfields (i.e. 'bitmask' is non-zero),
+'display' is used to tell the proto_tree how wide the parent bitfield is.
+With integers this is not needed since the type of integer itself
+(FT_UINT8, FT_UINT16, FT_UINT24, FT_UINT32, etc.) tells the proto_tree how
+wide the parent bitfield is.
-Additionally, BASE_NONE is used for 'display' as a NULL-value. That is,
-for non-integers and non-bitfield FT_BOOLEANs, you'll want to use BASE_NONE
-in the 'display' field. You may not use BASE_NONE for integers.
+For FT_ABSOLUTE_TIME fields, 'display' is used to indicate whether the
+time is to be displayed as a time in the time zone for the machine on
+which Wireshark/TShark is running or as UTC and, for UTC, whether the
+date should be displayed as "{monthname}, {month} {day_of_month},
+{year}" or as "{year/day_of_year}".
+
+Additionally, BASE_NONE is used for 'display' as a NULL-value. That is, for
+non-integers other than FT_ABSOLUTE_TIME fields, and non-bitfield
+FT_BOOLEANs, you'll want to use BASE_NONE in the 'display' field. You may
+not use BASE_NONE for integers.
It is possible that in the future we will record the endianness of
integers. If so, it is likely that we'll use a bitmask on the display field
so that integers would be represented as BEND|BASE_DEC or LEND|BASE_HEX.
-But that has not happened yet.
+But that has not happened yet; note that there are protocols for which
+no endianness is specified, such as the X11 protocol and the DCE RPC
+protocol, so it would not be possible to record the endianness of all
+integral fields.
strings
-------
+-- value_string
Some integer fields, of type FT_UINT*, need labels to represent the true
value of a field. You could think of those fields as having an
enumerated data type, rather than an integral data type.
-A 'value_string' structure is a way to map values to strings.
+A 'value_string' structure is a way to map values to strings.
typedef struct _value_string {
guint32 value;
For fields of that type, you would declare an array of "value_string"s:
static const value_string valstringname[] = {
- { INTVAL1, "Descriptive String 1" },
- { INTVAL2, "Descriptive String 2" },
- { 0, NULL },
+ { INTVAL1, "Descriptive String 1" },
+ { INTVAL2, "Descriptive String 2" },
+ { 0, NULL }
};
(the last entry in the array must have a NULL 'strptr' value, to
indicate the end of the array). The 'strings' field would be set to
'VALS(valstringname)'.
-(Note: before Ethereal 0.7.6, we had separate field types like
-FT_VALS_UINT8 which denoted the use of value_strings. Now, the
-non-NULLness of the pointer lets the proto_tree know that a value_string
-is meant for this field).
-
If the field has a numeric rather than an enumerated type, the 'strings'
field would be set to NULL.
-FT_BOOLEANS have a default map of 0 = "False", 1 (or anything else) = "True".
+-- Extended value strings
+You can also use an extended version of the value_string for faster lookups.
+It requires a value_string as input.
+If all of a contiguous range of values from min to max are present in the array
+the value will be used as as a direct index into a value_string array.
+
+If the values in the array are not contiguous (ie: there are "gaps"), but are
+in assending order a binary search will be used.
+
+Note: "gaps" in a value_string array can be filled with "empty" entries eg:
+{value, "Unknown"} so that direct access to the array is is possible.
+
+The init macro (see below) will perform a check on the value string the first
+time it is used to determine which search algorithm fits and fall back to a
+linear search if the value_string does not meet the criteria above.
+
+Use this macro to initialise the extended value_string at comile time:
+
+static value_string_ext valstringname_ext = VALUE_STRING_EXT_INIT(valstringname);
+
+Extended value strings can be created at runtime by calling
+ value_string_ext_new(<ptr to value_string array>,
+ <total number of entries in the value_string_array>, /* include {0, NULL} entry */
+ <value_string_name>);
+
+For hf[] array FT_(U)INT* fields that need a 'valstringname_ext' struct, the
+'strings' field would be set to '&valstringname_ext)'. Furthermore, 'display'
+field must be ORed with 'BASE_EXT_STRING' (e.g. BASE_DEC|BASE_EXT_STRING).
+
+
+-- Ranges
+If the field has a numeric type that might logically fit in ranges of values
+one can use a range_string struct.
+
+Thus a 'range_string' structure is a way to map ranges to strings.
+
+ typedef struct _range_string {
+ guint32 value_min;
+ guint32 value_max;
+ const gchar *strptr;
+ } range_string;
+
+For fields of that type, you would declare an array of "range_string"s:
+
+ static const range_string rvalstringname[] = {
+ { INTVAL_MIN1, INTVALMAX1, "Descriptive String 1" },
+ { INTVAL_MIN2, INTVALMAX2, "Descriptive String 2" },
+ { 0, 0, NULL }
+ };
+
+If INTVAL_MIN equals INTVAL_MAX for a given entry the range_string
+behavior collapses to the one of value_string.
+For FT_(U)INT* fields that need a 'range_string' struct, the 'strings' field
+would be set to 'RVALS(rvalstringname)'. Furthermore, 'display' field must be
+ORed with 'BASE_RANGE_STRING' (e.g. BASE_DEC|BASE_RANGE_STRING).
+
+-- Booleans
+FT_BOOLEANs have a default map of 0 = "False", 1 (or anything else) = "True".
Sometimes it is useful to change the labels for boolean values (e.g.,
to "Yes"/"No", "Fast"/"Slow", etc.). For these mappings, a struct called
-true_false_string is used. (This struct is new as of Ethereal 0.7.6).
+true_false_string is used.
typedef struct true_false_string {
char *true_string;
Its two fields are pointers to the string representing truth, and the
string representing falsehood. For FT_BOOLEAN fields that need a
'true_false_string' struct, the 'strings' field would be set to
-'TFS(&boolstringname)'.
+'TFS(&boolstringname)'.
If the Boolean field is to be displayed as "False" or "True", the
'strings' field would be set to NULL.
+Wireshark predefines a whole range of ready made "true_false_string"s
+in tfs.h, included via packet.h.
+
bitmask
-------
If the field is a bitfield, then the bitmask is the mask which will
leave only the bits needed to make the field when ANDed with a value.
The proto_tree routines will calculate 'bitshift' automatically
from 'bitmask', by finding the rightmost set bit in the bitmask.
+This shift is applied before applying string mapping functions or
+filtering.
If the field is not a bitfield, then bitmask should be set to 0.
blurb
-----
-This is a string giving a proper description of the field.
-It should be at least one grammatically complete sentence.
+This is a string giving a proper description of the field. It should be
+at least one grammatically complete sentence, or NULL in which case the
+name field is used. (Please do not use "").
It is meant to provide a more detailed description of the field than the
name alone provides. This information will be used in the man page, and
in a future GUI display-filter creation tool. We might also add tooltips
{ &hf_field_a,
{ "Field A", "proto.field_a", FT_UINT8, BASE_HEX, NULL,
- 0xf0, "Field A represents Apples" }},
+ 0xf0, "Field A represents Apples", HFILL }},
{ &hf_field_b,
{ "Field B", "proto.field_b", FT_UINT16, BASE_DEC, VALS(vs),
- 0x0, "Field B represents Bananas" }}
+ 0x0, "Field B represents Bananas", HFILL }}
};
proto_eg = proto_register_protocol("Example Protocol",
to have the compiler compute the array length for you at compile time.
If you don't have any fields to register, do *NOT* create a zero-length
-"hf" array; not all compilers used to compile Ethereal support them.
+"hf" array; not all compilers used to compile Wireshark support them.
Just omit the "hf" array, and the "proto_register_field_array()" call,
entirely.
{ &hf_field_8bit, /* 8-bit version of proto.field */
{ "Field (8 bit)", "proto.field", FT_UINT8, BASE_DEC, NULL,
- 0x00, "Field represents FOO" }},
+ 0x00, "Field represents FOO", HFILL }},
{ &hf_field_32bit, /* 32-bit version of proto.field */
{ "Field (32 bit)", "proto.field", FT_UINT32, BASE_DEC, NULL,
- 0x00, "Field represents FOO" }}
+ 0x00, "Field represents FOO", HFILL }}
};
This way a filter expression can match a header field, irrespective of the
representation of it in the specific protocol context. This is interesting
for protocols with variable-width header fields.
+The HFILL macro at the end of the struct will set reasonable default values
+for internally used fields.
+
1.6.2 Adding Items and Values to the Protocol Tree.
A protocol item is added to an existing protocol tree with one of a
static gint *ett[] = {
&ett_eg,
- &ett_field_a,
+ &ett_field_a
};
proto_register_subtree_array(ett, array_length(ett));
in your "register" routine, just as you register the protocol and the
fields for that protocol.
+The ett_ variables identify particular type of subtree so that if you expand
+one of them, Wireshark keeps track of that and, when you click on
+another packet, it automatically opens all subtrees of that type.
+If you close one of them, all subtrees of that type will be closed when
+you move to another packet.
+
There are several functions that the programmer can use to add either
protocol or field labels to the proto_tree:
proto_item*
- proto_tree_add_item(tree, id, tvb, start, length, little_endian);
-
- proto_item*
- proto_tree_add_item_hidden(tree, id, tvb, start, length, little_endian);
+ proto_tree_add_item(tree, id, tvb, start, length, encoding);
proto_item*
proto_tree_add_none_format(tree, id, tvb, start, length, format, ...);
proto_item*
proto_tree_add_protocol_format(tree, id, tvb, start, length,
- format, ...);
+ format, ...);
proto_item *
proto_tree_add_bytes(tree, id, tvb, start, length, start_ptr);
proto_item *
- proto_tree_add_bytes_hidden(tree, id, tvb, start, length, start_ptr);
+ proto_tree_add_bytes_format(tree, id, tvb, start, length, start_ptr,
+ format, ...);
proto_item *
- proto_tree_add_bytes_format(tree, id, tvb, start, length, start_ptr,
- format, ...);
+ proto_tree_add_bytes_format_value(tree, id, tvb, start, length,
+ start_ptr, format, ...);
proto_item *
proto_tree_add_time(tree, id, tvb, start, length, value_ptr);
proto_item *
- proto_tree_add_time_hidden(tree, id, tvb, start, length, value_ptr);
+ proto_tree_add_time_format(tree, id, tvb, start, length, value_ptr,
+ format, ...);
proto_item *
- proto_tree_add_time_format(tree, id, tvb, start, length, value_ptr,
- format, ...);
+ proto_tree_add_time_format_value(tree, id, tvb, start, length,
+ value_ptr, format, ...);
proto_item *
proto_tree_add_ipxnet(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_ipxnet_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_ipxnet_format(tree, id, tvb, start, length, value,
+ format, ...);
proto_item *
- proto_tree_add_ipxnet_format(tree, id, tvb, start, length, value,
- format, ...);
+ proto_tree_add_ipxnet_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item *
proto_tree_add_ipv4(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_ipv4_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_ipv4_format(tree, id, tvb, start, length, value,
+ format, ...);
proto_item *
- proto_tree_add_ipv4_format(tree, id, tvb, start, length, value,
- format, ...);
+ proto_tree_add_ipv4_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item *
proto_tree_add_ipv6(tree, id, tvb, start, length, value_ptr);
proto_item *
- proto_tree_add_ipv6_hidden(tree, id, tvb, start, length, value_ptr);
+ proto_tree_add_ipv6_format(tree, id, tvb, start, length, value_ptr,
+ format, ...);
proto_item *
- proto_tree_add_ipv6_format(tree, id, tvb, start, length, value_ptr,
- format, ...);
+ proto_tree_add_ipv6_format_value(tree, id, tvb, start, length,
+ value_ptr, format, ...);
proto_item *
proto_tree_add_ether(tree, id, tvb, start, length, value_ptr);
proto_item *
- proto_tree_add_ether_hidden(tree, id, tvb, start, length, value_ptr);
+ proto_tree_add_ether_format(tree, id, tvb, start, length, value_ptr,
+ format, ...);
proto_item *
- proto_tree_add_ether_format(tree, id, tvb, start, length, value_ptr,
- format, ...);
+ proto_tree_add_ether_format_value(tree, id, tvb, start, length,
+ value_ptr, format, ...);
proto_item *
proto_tree_add_string(tree, id, tvb, start, length, value_ptr);
proto_item *
- proto_tree_add_string_hidden(tree, id, tvb, start, length, value_ptr);
+ proto_tree_add_string_format(tree, id, tvb, start, length, value_ptr,
+ format, ...);
proto_item *
- proto_tree_add_string_format(tree, id, tvb, start, length, value_ptr,
- format, ...);
+ proto_tree_add_string_format_value(tree, id, tvb, start, length,
+ value_ptr, format, ...);
proto_item *
proto_tree_add_boolean(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_boolean_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_boolean_format(tree, id, tvb, start, length, value,
+ format, ...);
proto_item *
- proto_tree_add_boolean_format(tree, id, tvb, start, length, value,
- format, ...);
+ proto_tree_add_boolean_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item *
proto_tree_add_float(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_float_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_float_format(tree, id, tvb, start, length, value,
+ format, ...);
proto_item *
- proto_tree_add_float_format(tree, id, tvb, start, length, value,
- format, ...);
+ proto_tree_add_float_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item *
proto_tree_add_double(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_double_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_double_format(tree, id, tvb, start, length, value,
+ format, ...);
proto_item *
- proto_tree_add_double_format(tree, id, tvb, start, length, value,
- format, ...);
+ proto_tree_add_double_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item *
proto_tree_add_uint(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_uint_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_uint_format(tree, id, tvb, start, length, value,
+ format, ...);
+
+ proto_item *
+ proto_tree_add_uint_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item *
- proto_tree_add_uint_format(tree, id, tvb, start, length, value,
- format, ...);
+ proto_tree_add_uint64(tree, id, tvb, start, length, value);
proto_item *
- proto_tree_add_int(tree, id, tvb, start, length, value);
+ proto_tree_add_uint64_format(tree, id, tvb, start, length, value,
+ format, ...);
proto_item *
- proto_tree_add_int_hidden(tree, id, tvb, start, length, value);
+ proto_tree_add_uint64_format_value(tree, id, tvb, start, length,
+ value, format, ...);
+
+ proto_item *
+ proto_tree_add_int(tree, id, tvb, start, length, value);
proto_item *
proto_tree_add_int_format(tree, id, tvb, start, length, value,
- format, ...);
+ format, ...);
+
+ proto_item *
+ proto_tree_add_int_format_value(tree, id, tvb, start, length,
+ value, format, ...);
+
+ proto_item *
+ proto_tree_add_int64(tree, id, tvb, start, length, value);
+
+ proto_item *
+ proto_tree_add_int64_format(tree, id, tvb, start, length, value,
+ format, ...);
+
+ proto_item *
+ proto_tree_add_int64_format_value(tree, id, tvb, start, length,
+ value, format, ...);
proto_item*
proto_tree_add_text(tree, tvb, start, length, format, ...);
proto_item*
proto_tree_add_text_valist(tree, tvb, start, length, format, ap);
+ proto_item *
+ proto_tree_add_guid(tree, id, tvb, start, length, value_ptr);
+
+ proto_item *
+ proto_tree_add_guid_format(tree, id, tvb, start, length, value_ptr,
+ format, ...);
+
+ proto_item *
+ proto_tree_add_guid_format_value(tree, id, tvb, start, length,
+ value_ptr, format, ...);
+
+ proto_item *
+ proto_tree_add_oid(tree, id, tvb, start, length, value_ptr);
+
+ proto_item *
+ proto_tree_add_oid_format(tree, id, tvb, start, length, value_ptr,
+ format, ...);
+
+ proto_item *
+ proto_tree_add_eui64(tree, id, tvb, start, length, value);
+
+ proto_item *
+ proto_tree_add_eui64_format(tree, id, tvb, start, length, value,
+ format, ...);
+
+ proto_item *
+ proto_tree_add_eui64_format_value(tree, id, tvb, start, length,
+ value, format, ...);
+
+ proto_item *
+ proto_tree_add_oid_format_value(tree, id, tvb, start, length,
+ value_ptr, format, ...);
+
+ proto_item*
+ proto_tree_add_bits_item(tree, id, tvb, bit_offset, no_of_bits,
+ little_endian);
+
+ proto_item *
+ proto_tree_add_bits_ret_val(tree, id, tvb, bit_offset, no_of_bits,
+ return_value, little_endian);
+
+ proto_item *
+ proto_tree_add_bitmask(tree, tvb, start, header, ett, fields,
+ little_endian);
+
+ proto_item *
+ proto_tree_add_bitmask_text(tree, tvb, offset, len, name, fallback,
+ ett, fields, little_endian, flags);
+
The 'tree' argument is the tree to which the item is to be added. The
'tvb' argument is the tvbuff from which the item's value is being
extracted; the 'start' argument is the offset from the beginning of that
tvbuff of the item being added, and the 'length' argument is the length,
-in bytes, of the item.
+in bytes, of the item, bit_offset is the offset in bits and no_of_bits
+is the length in bits.
The length of some items cannot be determined until the item has been
dissected; to add such an item, add it with a length of -1, and, when the
proto_tree_add_item()
---------------------
-proto_tree_add_item is used when you wish to do no special formatting.
+proto_tree_add_item is used when you wish to do no special formatting.
The item added to the GUI tree will contain the name (as passed in the
proto_register_*() function) and a value. The value will be fetched
from the tvbuff by proto_tree_add_item(), based on the type of the field
-and, for integral and Boolean fields, the byte order of the value; the
-byte order is specified by the 'little_endian' argument, which is TRUE
-if the value is little-endian and FALSE if it is big-endian.
+and the encoding of the value as specified by the "encoding" argument.
+
+For FT_NONE, FT_BYTES, FT_ETHER, FT_IPv6, FT_IPXNET, FT_OID fields,
+and 'protocol' fields the encoding is not relevant; the 'encoding'
+argument should be ENC_NA (Not Applicable).
+
+For integral, floating-point, Boolean, FT_GUID, and FT_EUI64 fields,
+the encoding specifies the byte order of the value; the 'encoding'
+argument should be is ENC_LITTLE_ENDIAN if the value is little-endian
+and ENC_BIG_ENDIAN if it is big-endian.
+
+For FT_IPv4 fields, the encoding also specifies the byte order of the
+value. In almost all cases, the encoding is in network byte order,
+hence big-endian, but in at least one protocol dissected by Wireshark,
+at least one IPv4 address is byte-swapped, so it's in little-endian
+order.
+
+For string fields, the encoding specifies the character set used for the
+string and the way individual code points in that character set are
+encoded. For FT_UINT_STRING fields, the byte order of the count must be
+specified; when support for UTF-16 encoding is added, the byte order of
+the encoding will also have to be specified. In other cases, ENC_NA
+should be used. The character encodings that are currently
+supported are:
+
+ ENC_UTF_8 - UTF-8
+ ENC_ASCII - ASCII (currently treated as UTF-8; in the future,
+ all bytes with the 8th bit set will be treated as
+ errors)
+ ENC_EBCDIC - EBCDIC
+
+Other encodings will be added in the future.
+
+For FT_ABSOLUTE_TIME fields, the encoding specifies the form in which
+the time stamp is specified, as well as its byte order. The time stamp
+encodings that are curretly supported are:
+
+ ENC_TIME_TIMESPEC - seconds (4 bytes) and nanoseconds (4 bytes)
+ of time since January 1, 1970, midnight UTC.
+
+ ENC_TIME_NTP - an NTP timestamp, represented as a 64-bit
+ unsigned fixed-point number, in seconds relative to 0h
+ on 1 January 1900. The integer part is in the first 32
+ bits and the fraction part in the last 32 bits.
+
+For other types, there is no support for proto_tree_add_item().
Now that definitions of fields have detailed information about bitfield
fields, you can use proto_tree_add_item() with no extra processing to
add bitfield values to your tree. Here's an example. Take the Format
-Identifer (FID) field in the Transmission Header (TH) portion of the SNA
+Identifier (FID) field in the Transmission Header (TH) portion of the SNA
protocol. The FID is the high nibble of the first byte of the TH. The
FID would be registered like this:
- name = "Format Identifer"
+ name = "Format Identifier"
abbrev = "sna.th.fid"
type = FT_UINT8
display = BASE_HEX
The code to add the FID to the tree would be;
- proto_tree_add_item(bf_tree, hf_sna_th_fid, tvb, offset, 1, TRUE);
+ proto_tree_add_item(bf_tree, hf_sna_th_fid, tvb, offset, 1,
+ ENC_BIG_ENDIAN);
The definition of the field already has the information about bitmasking
and bitshifting, so it does the work of masking and shifting for us!
This also means that you no longer have to create value_string structs
with the values bitshifted. The value_string for FID looks like this,
-even though the FID value is actually contained in the high nibble.
+even though the FID value is actually contained in the high nibble.
(You'd expect the values to be 0x0, 0x10, 0x20, etc.)
/* Format Identifier */
{ 0x3, "Subarea Node or SNA host <--> Subarea Node" },
{ 0x4, "?" },
{ 0x5, "?" },
- { 0xf, "Adjaced Subarea Nodes" },
+ { 0xf, "Adjacent Subarea Nodes" },
{ 0, NULL }
};
naturally expect them to. You'd type "sna.th.fid == 0xf" to find Adjacent
Subarea Nodes. The user does not have to shift the value of the FID to
the high nibble of the byte ("sna.th.fid == 0xf0") as was necessary
-before Ethereal 0.7.6.
-
-proto_tree_add_item_hidden()
-----------------------------
-proto_tree_add_item_hidden is used to add fields and values to a tree,
-but not show them on a GUI tree. The caller may want a value to be
-included in a tree so that the packet can be filtered on this field, but
-the representation of that field in the tree is not appropriate. An
-example is the token-ring routing information field (RIF). The best way
-to show the RIF in a GUI is by a sequence of ring and bridge numbers.
-Rings are 3-digit hex numbers, and bridges are single hex digits:
-
- RIF: 001-A-013-9-C0F-B-555
-
-In the case of RIF, the programmer should use a field with no value and
-use proto_tree_add_none_format() to build the above representation. The
-programmer can then add the ring and bridge values, one-by-one, with
-proto_tree_add_item_hidden() so that the user can then filter on or
-search for a particular ring or bridge. Here's a skeleton of how the
-programmer might code this.
-
- char *rif;
- rif = create_rif_string(...);
-
- proto_tree_add_none_format(tree, hf_tr_rif_label, ..., "RIF: %s", rif);
-
- for(i = 0; i < num_rings; i++) {
- proto_tree_add_item_hidden(tree, hf_tr_rif_ring, ..., FALSE);
- }
- for(i = 0; i < num_rings - 1; i++) {
- proto_tree_add_item_hidden(tree, hf_tr_rif_bridge, ..., FALSE);
- }
-
-The logical tree has these items:
-
- hf_tr_rif_label, text="RIF: 001-A-013-9-C0F-B-555", value = NONE
- hf_tr_rif_ring, hidden, value=0x001
- hf_tr_rif_bridge, hidden, value=0xA
- hf_tr_rif_ring, hidden, value=0x013
- hf_tr_rif_bridge, hidden, value=0x9
- hf_tr_rif_ring, hidden, value=0xC0F
- hf_tr_rif_bridge, hidden, value=0xB
- hf_tr_rif_ring, hidden, value=0x555
-
-GUI or print code will not display the hidden fields, but a display
-filter or "packet grep" routine will still see the values. The possible
-filter is then possible:
-
- tr.rif_ring eq 0x013
+in the past.
proto_tree_add_protocol_format()
-----------------------------
+--------------------------------
proto_tree_add_protocol_format is used to add the top-level item for the
-protocol when the dissector routines wants complete control over how the
+protocol when the dissector routine wants complete control over how the
field and value will be represented on the GUI tree. The ID value for
the protocol is passed in as the "id" argument; the rest of the
-arguments are a "printf"-style format and any arguments for that format.
+arguments are a "printf"-style format and any arguments for that format.
The caller must include the name of the protocol in the format; it is
not added automatically as in proto_tree_add_item().
proto_tree_add_float()
proto_tree_add_double()
proto_tree_add_uint()
+proto_tree_add_uint64()
proto_tree_add_int()
-----------------------------
+proto_tree_add_int64()
+proto_tree_add_guid()
+proto_tree_add_oid()
+proto_tree_add_eui64()
+------------------------
These routines are used to add items to the protocol tree if either:
the value of the item to be added isn't just extracted from the
For proto_tree_add_bytes(), the 'value_ptr' argument is a pointer to a
sequence of bytes.
+For proto_tree_add_bytes_format() and proto_tree_add_bytes_format_value(), the
+'value_ptr' argument is a pointer to a sequence of bytes or NULL if the bytes
+should be taken from the given TVB using the given offset and length.
+
For proto_tree_add_time(), the 'value_ptr' argument is a pointer to an
"nstime_t", which is a structure containing the time to be added; it has
'secs' and 'nsecs' members, giving the integral part and the fractional
For proto_tree_add_string(), the 'value_ptr' argument is a pointer to a
text string.
-For proto_tree_add_boolean(), the 'value' argument is a 32-bit integer;
-zero means "false", and non-zero means "true".
+For proto_tree_add_boolean(), the 'value' argument is a 32-bit integer.
+It is masked and shifted as defined by the field info after which zero
+means "false", and non-zero means "true".
For proto_tree_add_float(), the 'value' argument is a 'float' in the
host's floating-point format.
For proto_tree_add_uint(), the 'value' argument is a 32-bit unsigned
integer value, in host byte order. (This routine cannot be used to add
-64-bit integers; they can only be added with proto_tree_add_item().)
+64-bit integers.)
+
+For proto_tree_add_uint64(), the 'value' argument is a 64-bit unsigned
+integer value, in host byte order.
For proto_tree_add_int(), the 'value' argument is a 32-bit signed
integer value, in host byte order. (This routine cannot be used to add
-64-bit integers; they can only be added with proto_tree_add_item().)
-
-proto_tree_add_bytes_hidden()
-proto_tree_add_time_hidden()
-proto_tree_add_ipxnet_hidden()
-proto_tree_add_ipv4_hidden()
-proto_tree_add_ipv6_hidden()
-proto_tree_add_ether_hidden()
-proto_tree_add_string_hidden()
-proto_tree_add_boolean_hidden()
-proto_tree_add_float_hidden()
-proto_tree_add_double_hidden()
-proto_tree_add_uint_hidden()
-proto_tree_add_int_hidden()
-----------------------------
-These routines add fields and values to a tree, but don't show them in
-the GUI tree. They are used for the same reason that
-proto_tree_add_item() is used.
+64-bit integers.)
+
+For proto_tree_add_int64(), the 'value' argument is a 64-bit signed
+integer value, in host byte order.
+
+For proto_tree_add_guid(), the 'value_ptr' argument is a pointer to an
+e_guid_t structure.
+
+For proto_tree_add_oid(), the 'value_ptr' argument is a pointer to an
+ASN.1 Object Identifier.
+
+For proto_tree_add_eui64(), the 'value' argument is a 64-bit integer
+value
proto_tree_add_bytes_format()
proto_tree_add_time_format()
proto_tree_add_float_format()
proto_tree_add_double_format()
proto_tree_add_uint_format()
+proto_tree_add_uint64_format()
proto_tree_add_int_format()
+proto_tree_add_int64_format()
+proto_tree_add_guid_format()
+proto_tree_add_oid_format()
+proto_tree_add_eui64_format()
----------------------------
These routines are used to add items to the protocol tree when the
-dissector routines wants complete control over how the field and value
+dissector routine wants complete control over how the field and value
will be represented on the GUI tree. The argument giving the value is
the same as the corresponding proto_tree_add_XXX() function; the rest of
the arguments are a "printf"-style format and any arguments for that
format. The caller must include the name of the field in the format; it
is not added automatically as in the proto_tree_add_XXX() functions.
+proto_tree_add_bytes_format_value()
+proto_tree_add_time_format_value()
+proto_tree_add_ipxnet_format_value()
+proto_tree_add_ipv4_format_value()
+proto_tree_add_ipv6_format_value()
+proto_tree_add_ether_format_value()
+proto_tree_add_string_format_value()
+proto_tree_add_boolean_format_value()
+proto_tree_add_float_format_value()
+proto_tree_add_double_format_value()
+proto_tree_add_uint_format_value()
+proto_tree_add_uint64_format_value()
+proto_tree_add_int_format_value()
+proto_tree_add_int64_format_value()
+proto_tree_add_guid_format_value()
+proto_tree_add_oid_format_value()
+proto_tree_add_eui64_format_value()
+------------------------------------
+
+These routines are used to add items to the protocol tree when the
+dissector routine wants complete control over how the value will be
+represented on the GUI tree. The argument giving the value is the same
+as the corresponding proto_tree_add_XXX() function; the rest of the
+arguments are a "printf"-style format and any arguments for that format.
+With these routines, unlike the proto_tree_add_XXX_format() routines,
+the name of the field is added automatically as in the
+proto_tree_add_XXX() functions; only the value is added with the format.
+
proto_tree_add_text()
---------------------
proto_tree_add_text() is used to add a label to the GUI tree. It will
-contain no value, so it is not searchable in the display filter process.
+contain no value, so it is not searchable in the display filter process.
This function was needed in the transition from the old-style proto_tree
-to this new-style proto_tree so that Ethereal would still decode all
-protocols w/o being able to filter on all protocols and fields.
-Otherwise we would have had to cripple Ethereal's functionality while we
+to this new-style proto_tree so that Wireshark would still decode all
+protocols w/o being able to filter on all protocols and fields.
+Otherwise we would have had to cripple Wireshark's functionality while we
converted all the old-style proto_tree calls to the new-style proto_tree
-calls.
+calls. In other words, you should not use this in new code unless you've got
+a specific reason (see below).
This can also be used for items with subtrees, which may not have values
themselves - the items in the subtree are the ones with values.
'proto_tree_add_text()', a 'printf'-style format string, and a set of
arguments corresponding to '%' format items in that string, and replaces
the text for the item created by 'proto_tree_add_text()' with the result
-of applying the arguments to the format string.
+of applying the arguments to the format string.
'proto_item_append_text()' is similar, but it appends to the text for
the item the result of applying the arguments to the format string.
proto_item_set_text(ti, "%s: %s", type, value);
-after the "type" and "value" fields have been extracted and dissected.
+after the "type" and "value" fields have been extracted and dissected.
<label> would be a label giving what information about the subtree is
available without dissecting any of the data in the subtree.
-Note that an exception might thrown when trying to extract the values of
+Note that an exception might be thrown when trying to extract the values of
the items used to set the label, if not all the bytes of the item are
available. Thus, one should create the item with text that is as
meaningful as possible, and set it or append additional information to
-it as the values needed to supply that information is extracted.
+it as the values needed to supply that information are extracted.
proto_tree_add_text_valist()
----------------------
+----------------------------
This is like proto_tree_add_text(), but takes, as the last argument, a
'va_list'; it is used to allow routines that take a printf-like
variable-length list of arguments to add a text item to the protocol
tree.
-1.7 Utility routines
+proto_tree_add_bits_item()
+--------------------------
+Adds a number of bits to the protocol tree which does not have to be byte
+aligned. The offset and length is in bits.
+Output format:
+
+..10 1010 10.. .... "value" (formatted as FT_ indicates).
+
+proto_tree_add_bits_ret_val()
+-----------------------------
+Works in the same way but also returns the value of the read bits.
+
+proto_tree_add_bitmask() and proto_tree_add_bitmask_text()
+----------------------------------------------------------
+This function provides an easy to use and convenient helper function
+to manage many types of common bitmasks that occur in protocols.
+
+This function will dissect a 1/2/3/4 byte large bitmask into its individual
+fields.
+header is an integer type and must be of type FT_[U]INT{8|16|24|32} and
+represents the entire width of the bitmask.
+
+'header' and 'ett' are the hf fields and ett field respectively to create an
+expansion that covers the 1-4 bytes of the bitmask.
+
+'fields' is a NULL terminated array of pointers to hf fields representing
+the individual subfields of the bitmask. These fields must either be integers
+of the same byte width as 'header' or of the type FT_BOOLEAN.
+Each of the entries in 'fields' will be dissected as an item under the
+'header' expansion and also IF the field is a boolean and IF it is set to 1,
+then the name of that boolean field will be printed on the 'header' expansion
+line. For integer type subfields that have a value_string defined, the
+matched string from that value_string will be printed on the expansion line
+as well.
+
+Example: (from the SCSI dissector)
+ static int hf_scsi_inq_peripheral = -1;
+ static int hf_scsi_inq_qualifier = -1;
+ static int hf_scsi_inq_devtype = -1;
+ ...
+ static gint ett_scsi_inq_peripheral = -1;
+ ...
+ static const int *peripheal_fields[] = {
+ &hf_scsi_inq_qualifier,
+ &hf_scsi_inq_devtype,
+ NULL
+ };
+ ...
+ /* Qualifier and DeviceType */
+ proto_tree_add_bitmask(tree, tvb, offset, hf_scsi_inq_peripheral,
+ ett_scsi_inq_peripheral, peripheal_fields, FALSE);
+ offset+=1;
+ ...
+ { &hf_scsi_inq_peripheral,
+ {"Peripheral", "scsi.inquiry.preipheral", FT_UINT8, BASE_HEX,
+ NULL, 0, NULL, HFILL}},
+ { &hf_scsi_inq_qualifier,
+ {"Qualifier", "scsi.inquiry.qualifier", FT_UINT8, BASE_HEX,
+ VALS (scsi_qualifier_val), 0xE0, NULL, HFILL}},
+ { &hf_scsi_inq_devtype,
+ {"Device Type", "scsi.inquiry.devtype", FT_UINT8, BASE_HEX,
+ VALS (scsi_devtype_val), SCSI_DEV_BITS, NULL, HFILL}},
+ ...
+
+Which provides very pretty dissection of this one byte bitmask.
+
+ Peripheral: 0x05, Qualifier: Device type is connected to logical unit, Device Type: CD-ROM
+ 000. .... = Qualifier: Device type is connected to logical unit (0x00)
+ ...0 0101 = Device Type: CD-ROM (0x05)
+
+The proto_tree_add_bitmask_text() function is an extended version of
+the proto_tree_add_bitmask() function. In addition, it allows to:
+- Provide a leading text (e.g. "Flags: ") that will appear before
+ the comma-separated list of field values
+- Provide a fallback text (e.g. "None") that will be appended if
+ no fields warranted a change to the top-level title.
+- Using flags, specify which fields will affect the top-level title.
+
+There are the following flags defined:
+
+ BMT_NO_APPEND - the title is taken "as-is" from the 'name' argument.
+ BMT_NO_INT - only boolean flags are added to the title.
+ BMT_NO_FALSE - boolean flags are only added to the title if they are set.
+ BMT_NO_TFS - only add flag name to the title, do not use true_false_string
+
+The proto_tree_add_bitmask() behavior can be obtained by providing
+both 'name' and 'fallback' arguments as NULL, and a flags of
+(BMT_NO_FALSE|BMT_NO_TFS).
+
+PROTO_ITEM_SET_GENERATED()
+--------------------------
+PROTO_ITEM_SET_GENERATED is used to mark fields as not being read from the
+captured data directly, but inferred from one or more values.
+
+One of the primary uses of this is the presentation of verification of
+checksums. Every IP packet has a checksum line, which can present the result
+of the checksum verification, if enabled in the preferences. The result is
+presented as a subtree, where the result is enclosed in square brackets
+indicating a generated field.
+
+ Header checksum: 0x3d42 [correct]
+ [Good: True]
+ [Bad: False]
+
+PROTO_ITEM_SET_HIDDEN()
+-----------------------
+PROTO_ITEM_SET_HIDDEN is used to hide fields, which have already been added
+to the tree, from being visible in the displayed tree.
+
+NOTE that creating hidden fields is actually quite a bad idea from a UI design
+perspective because the user (someone who did not write nor has ever seen the
+code) has no way of knowing that hidden fields are there to be filtered on
+thus defeating the whole purpose of putting them there. A Better Way might
+be to add the fields (that might otherwise be hidden) to a subtree where they
+won't be seen unless the user opens the subtree--but they can be found if the
+user wants.
+
+One use for hidden fields (which would be better implemented using visible
+fields in a subtree) follows: The caller may want a value to be
+included in a tree so that the packet can be filtered on this field, but
+the representation of that field in the tree is not appropriate. An
+example is the token-ring routing information field (RIF). The best way
+to show the RIF in a GUI is by a sequence of ring and bridge numbers.
+Rings are 3-digit hex numbers, and bridges are single hex digits:
+
+ RIF: 001-A-013-9-C0F-B-555
+
+In the case of RIF, the programmer should use a field with no value and
+use proto_tree_add_none_format() to build the above representation. The
+programmer can then add the ring and bridge values, one-by-one, with
+proto_tree_add_item() and hide them with PROTO_ITEM_SET_HIDDEN() so that the
+user can then filter on or search for a particular ring or bridge. Here's a
+skeleton of how the programmer might code this.
-1.7.1 match_strval and val_to_str
+ char *rif;
+ rif = create_rif_string(...);
+
+ proto_tree_add_none_format(tree, hf_tr_rif_label, ..., "RIF: %s", rif);
+
+ for(i = 0; i < num_rings; i++) {
+ proto_item *pi;
+
+ pi = proto_tree_add_item(tree, hf_tr_rif_ring, ...,
+ ENC_BIG_ENDIAN);
+ PROTO_ITEM_SET_HIDDEN(pi);
+ }
+ for(i = 0; i < num_rings - 1; i++) {
+ proto_item *pi;
+
+ pi = proto_tree_add_item(tree, hf_tr_rif_bridge, ...,
+ ENC_BIG_ENDIAN);
+ PROTO_ITEM_SET_HIDDEN(pi);
+ }
+
+The logical tree has these items:
+
+ hf_tr_rif_label, text="RIF: 001-A-013-9-C0F-B-555", value = NONE
+ hf_tr_rif_ring, hidden, value=0x001
+ hf_tr_rif_bridge, hidden, value=0xA
+ hf_tr_rif_ring, hidden, value=0x013
+ hf_tr_rif_bridge, hidden, value=0x9
+ hf_tr_rif_ring, hidden, value=0xC0F
+ hf_tr_rif_bridge, hidden, value=0xB
+ hf_tr_rif_ring, hidden, value=0x555
+
+GUI or print code will not display the hidden fields, but a display
+filter or "packet grep" routine will still see the values. The possible
+filter is then possible:
+
+ tr.rif_ring eq 0x013
+
+PROTO_ITEM_SET_URL
+------------------
+PROTO_ITEM_SET_URL is used to mark fields as containing a URL. This can only
+be done with fields of type FT_STRING(Z). If these fields are presented they
+are underlined, as could be done in a browser. These fields are sensitive to
+clicks as well, launching the configured browser with this URL as parameter.
+
+1.7 Utility routines.
+
+1.7.1 match_strval, match_strval_ext, val_to_str and val_to_str_ext.
A dissector may need to convert a value to a string, using a
'value_string' structure, by hand, rather than by declaring a field with
It will look up the value 'val' in the 'value_string' table pointed to
by 'vs', and return either the corresponding string, or NULL if the
-value could not be found in the table.
-
-'val_to_str()' can be used to generate a string for values not found in
-the table:
+value could not be found in the table. Note that, unless 'val' is
+guaranteed to be a value in the 'value_string' table ("guaranteed" as in
+"the code has already checked that it's one of those values" or "the
+table handles all possible values of the size of 'val'", not "the
+protocol spec says it has to be" - protocol specs do not prevent invalid
+packets from being put onto a network or into a purported packet capture
+file), you must check whether 'match_strval()' returns NULL, and arrange
+that its return value not be dereferenced if it's NULL. 'val_to_str()'
+can be used to generate a string for values not found in the table:
gchar*
val_to_str(guint32 val, const value_string *vs, const char *fmt)
If the value 'val' is found in the 'value_string' table pointed to by
'vs', 'val_to_str' will return the corresponding string; otherwise, it
will use 'fmt' as an 'sprintf'-style format, with 'val' as an argument,
-to generate a string, and will return a pointer to that string.
-(Currently, it has three 64-byte static buffers, and cycles through
-them; this permits the results of up to three calls to 'val_to_str' to
-be passed as arguments to a routine using those strings.)
+to generate a string, and will return a pointer to that string.
+You can use it in a call to generate a COL_INFO line for a frame such as
+
+ col_add_fstr(COL_INFO, ", %s", val_to_str(val, table, "Unknown %d"));
+
+The match_strval_ext and val_to_str_ext functions are "extended" versions
+of match_strval and val_to_str. They should be used for large value-string
+arrays which contain many entries. They implement value to string conversions
+which will do either a direct access or a binary search of the
+value string array if possible. See "Extended Value Strings" under
+section 1.6 "Constructing the protocol tree" for more information.
+
+See epan/value_string.h for detailed information on the various value_string
+functions.
-1.8 Calling Other Dissector
+1.7.2 match_strrval and rval_to_str.
-NOTE: This is discussed in the README.tvbuff file. For more
-information on tvbuffers consult that file.
+A dissector may need to convert a range of values to a string, using a
+'range_string' structure.
+
+'match_strrval()' will do that:
+
+ gchar*
+ match_strrval(guint32 val, const range_string *rs)
+
+It will look up the value 'val' in the 'range_string' table pointed to
+by 'rs', and return either the corresponding string, or NULL if the
+value could not be found in the table. Please note that its base
+behavior is inherited from match_strval().
+
+'rval_to_str()' can be used to generate a string for values not found in
+the table:
+
+ gchar*
+ rval_to_str(guint32 val, const range_string *rs, const char *fmt)
+
+If the value 'val' is found in the 'range_string' table pointed to by
+'rs', 'rval_to_str' will return the corresponding string; otherwise, it
+will use 'fmt' as an 'sprintf'-style format, with 'val' as an argument,
+to generate a string, and will return a pointer to that string. Please
+note that its base behavior is inherited from match_strval().
+
+1.8 Calling Other Dissectors.
As each dissector completes its portion of the protocol analysis, it
is expected to create a new tvbuff of type TVBUFF_SUBSET which
tvbuff_t *next_tvb;
int reported_length, available_length;
-
+
/* Make the next tvbuff */
/* IPX does have a length value in the header, so calculate report_length */
*/
reported_length = ipx_length - IPX_HEADER_LEN;
-/* Calculate the available data in the packet,
+/* Calculate the available data in the packet,
set this to -1 to use all the data in the tv_buffer
*/
available_length = tvb_length(tvb) - IPX_HEADER_LEN;
dissector_next( next_tvb, pinfo, tree);
-1.9 Editing Makefile.am and Makefile.nmake to add your dissector.
+1.9 Editing Makefile.common and CMakeLists.txt to add your dissector.
+
+To arrange that your dissector will be built as part of Wireshark, you
+must add the name of the source file for your dissector to the
+'DISSECTOR_SRC' macro in the 'Makefile.common' file in the 'epan/dissectors'
+directory. (Note that this is for modern versions of UNIX, so there
+is no 14-character limitation on file names, and for modern versions of
+Windows, so there is no 8.3-character limitation on file names.)
+
+If your dissector also has its own header file or files, you must add
+them to the 'DISSECTOR_INCLUDES' macro in the 'Makefile.common' file in
+the 'epan/dissectors' directory, so that it's included when release source
+tarballs are built (otherwise, the source in the release tarballs won't
+compile).
+
+In addition to the above, you should add your dissector source file name
+to the DISSECTOR_SRC section of epan/CMakeLists.txt
+
+
+1.10 Using the SVN source code tree.
+
+ See <http://www.wireshark.org/develop.html>
-To arrange that your dissector will be built as part of Ethereal, you
-must add the name of the source file for your dissector, and the header
-file that declares your main dissector routine, to the
-'DISSECTOR_SRC' macro in the 'Makefile.am' and 'Makefile.nmake'
-files in the top-level directory. (Note that this is for modern
-versions of UNIX, so there is no 14-character limitation on file names,
-and for modern versions of Windows, so there is no 8.3-character
-limitation on file names.)
-If your dissector also has its own header files, you must add them to
-the 'noinst_HEADERS' macro in the 'Makefile.am' file in the top-level
-directory, so that it's included when release source tarballs are built
-(otherwise, the source in the release tarballs won't compile).
+1.10a Using git with the SVN source code tree.
-Please remember to update both files; it may not be necessary to do so
-in order for you to build Ethereal on your machine, but both changes
-will need to be checked in to the Ethereal source code, to allow it to
-build on all platforms.
+ Install git and the git-svn package.
+ Run "mkdir git; cd git; git svn clone <svn-url>", e.g. if you are using
+ the anonymous svn tree, run
+ "git svn clone http://anonsvn.wireshark.org/wireshark/trunk/"
+
+ After that, a typical workflow may look like this (from "man git-svn"):
+
+ # Clone a repo (like git clone):
+ git svn clone http://svn.example.com/project/trunk
+ # Enter the newly cloned directory:
+ cd trunk
+ # You should be on master branch, double-check with ´git branch´
+ git branch
+ # Do some work and commit locally to git:
+ git commit ...
+ # Something is committed to SVN, rebase your local changes against the
+ # latest changes in SVN:
+ git svn rebase
+ # Now commit your changes (that were committed previously using git) to SVN
+ # as well as automatically updating your working HEAD:
+ git svn dcommit
+ # Append svn:ignore settings to the default git exclude file:
+ git svn show-ignore >> .git/info/exclude
-1.10 Using the CVS source code tree.
1.11 Submitting code for your new dissector.
+ - VERIFY that your dissector code does not use prohibited or deprecated APIs
+ as follows:
+ perl <wireshark_root>/tools/checkAPIs.pl <source-filename(s)>
+
+ - TEST YOUR DISSECTOR BEFORE SUBMITTING IT.
+ Use fuzz-test.sh and/or randpkt against your dissector. These are
+ described at <http://wiki.wireshark.org/FuzzTesting>.
+
+ - Subscribe to <mailto:wireshark-dev[AT]wireshark.org> by sending an email to
+ <mailto:wireshark-dev-request[AT]wireshark.org?body="help"> or visiting
+ <http://www.wireshark.org/lists/>.
+
+ - 'svn add' all the files of your new dissector.
+
+ - 'svn diff' the workspace and save the result to a file.
+
+ - Edit the diff file - remove any changes unrelated to your new dissector,
+ e.g. changes in config.nmake
+
+ - Submit a bug report to the Wireshark bug database, found at
+ <http://bugs.wireshark.org>, qualified as an enhancement and attach your
+ diff file there. Set the review request flag to '?' so it will pop up in
+ the patch review list.
+
+ - Create a Wiki page on the protocol at <http://wiki.wireshark.org>.
+ A template is provided so it is easy to setup in a consistent style.
+ See: <http://wiki.wireshark.org/HowToEdit>
+ and <http://wiki.wireshark.org/ProtocolReference>
+
+ - If possible, add sample capture files to the sample captures page at
+ <http://wiki.wireshark.org/SampleCaptures>. These files are used by
+ the automated build system for fuzz testing.
+
+ - If you find that you are contributing a lot to wireshark on an ongoing
+ basis you can request to become a committer which will allow you to
+ commit files to subversion directly.
+
2. Advanced dissector topics.
-2.1 ??
+2.1 Introduction.
+
+Some of the advanced features are being worked on constantly. When using them
+it is wise to check the relevant header and source files for additional details.
2.2 Following "conversations".
-In ethereal a conversation is defined as a series of data packet between two
+In wireshark a conversation is defined as a series of data packets between two
address:port combinations. A conversation is not sensitive to the direction of
the packet. The same conversation will be returned for a packet bound from
ServerA:1000 to ClientA:2000 and the packet from ClientA:2000 to ServerA:1000.
-There are five routines that you will use to work with a conversation:
+2.2.1 Conversation Routines
+
+There are six routines that you will use to work with a conversation:
conversation_new, find_conversation, conversation_add_proto_data,
-conversation_get_proto_data, and conversation_delete_proto_data.
+conversation_get_proto_data, conversation_delete_proto_data,
+and conversation_set_dissector.
-2.2.1 The conversation_init function.
+2.2.1.1 The conversation_init function.
-This is an internal routine for the conversation code. As such the you
+This is an internal routine for the conversation code. As such you
will not have to call this routine. Just be aware that this routine is
called at the start of each capture and before the packets are filtered
with a display filter. The routine will destroy all stored
conversations. This routine does NOT clean up any data pointers that are
-passed in the conversation_new 'data' variable. You are responsible for
-this clean up if you pass a malloc'ed pointer in this variable.
+passed in the conversation_add_proto_data 'data' variable. You are
+responsible for this clean up if you pass a malloc'ed pointer
+in this variable.
-See item 2.2.7 for more information about the 'data' pointer.
+See item 2.2.1.5 for more information about use of the 'data' pointer.
-2.2.2 The conversation_new function.
+2.2.1.2 The conversation_new function.
This routine will create a new conversation based upon two address/port
pairs. If you want to associate with the conversation a pointer to a
information on usage of the options parameter.
The conversation_new prototype:
- conversation_t *conversation_new(address *addr1, address *addr2,
- port_type ptype, guint32 port1, guint32 port2, guint options);
+ conversation_t *conversation_new(guint32 setup_frame, address *addr1,
+ address *addr2, port_type ptype, guint32 port1, guint32 port2,
+ guint options);
Where:
- address* addr1 = first data packet address
- address* addr2 = second data packet address
- port_type ptype = port type, this is defined in packet.h
- guint32 port1 = first data packet port
- guint32 port2 = second data packet port
- guint options = conversation options, NO_ADDR2 and/or NO_PORT2
+ guint32 setup_frame = The lowest numbered frame for this conversation
+ address* addr1 = first data packet address
+ address* addr2 = second data packet address
+ port_type ptype = port type, this is defined in packet.h
+ guint32 port1 = first data packet port
+ guint32 port2 = second data packet port
+ guint options = conversation options, NO_ADDR2 and/or NO_PORT2
+
+setup_frame indicates the first frame for this conversation, and is used to
+distinguish multiple conversations with the same addr1/port1 and addr2/port2
+pair that occur within the same capture session.
"addr1" and "port1" are the first address/port pair; "addr2" and "port2"
are the second address/port pair. A conversation doesn't have source
created using certain addresses and ports, in the case where the packet
doesn't specify the addresses and ports of both sides.
-2.2.3 The find_conversation function.
+2.2.1.3 The find_conversation function.
Call this routine to look up a conversation. If no conversation is found,
the routine will return a NULL value.
The find_conversation prototype:
- conversation_t *find_conversation(address *addr_a, address *addr_b,
- port_type ptype, guint32 port_a, guint32 port_b, guint options);
+ conversation_t *find_conversation(guint32 frame_num, address *addr_a,
+ address *addr_b, port_type ptype, guint32 port_a, guint32 port_b,
+ guint options);
Where:
+ guint32 frame_num = a frame number to match
address* addr_a = first address
address* addr_b = second address
port_type ptype = port type
guint32 port_b = second data packet port
guint options = conversation options, NO_ADDR_B and/or NO_PORT_B
+frame_num is a frame number to match. The conversation returned is where
+ (frame_num >= conversation->setup_frame
+ && frame_num < conversation->next->setup_frame)
+Suppose there are a total of 3 conversations (A, B, and C) that match
+addr_a/port_a and addr_b/port_b, where the setup_frame used in
+conversation_new() for A, B and C are 10, 50, and 100 respectively. The
+frame_num passed in find_conversation is compared to the setup_frame of each
+conversation. So if (frame_num >= 10 && frame_num < 50), conversation A is
+returned. If (frame_num >= 50 && frame_num < 100), conversation B is returned.
+If (frame_num >= 100) conversation C is returned.
+
"addr_a" and "port_a" are the first address/port pair; "addr_b" and
"port_b" are the second address/port pair. Again, as a conversation
doesn't have source and destination address/port pairs, so
If the NO_ADDR_B flag was specified to "find_conversation()", the
"addr_b" address will be treated as matching any "wildcarded" address;
if the NO_PORT_B flag was specified, the "port_b" port will be treated
-as matching any "wildcarded" port. If both flags are specified, i.e.
+as matching any "wildcarded" port. If both flags are specified, i.e.
NO_ADDR_B|NO_PORT_B, the "addr_b" address will be treated as matching
any "wildcarded" address and the "port_b" port will be treated as
matching any "wildcarded" port.
-2.2.4 The conversation_add_proto_data function.
+2.2.1.4 The find_or_create_conversation function.
+
+This convenience function will create find an existing conversation (by calling
+find_conversation()) and, if a conversation does not already exist, create a
+new conversation by calling conversation_new().
+
+The find_or_create_conversation prototype:
+
+ extern conversation_t *find_or_create_conversation(packet_info *pinfo);
+
+Where:
+ packet_info *pinfo = the packet_info structure
+
+The frame number and the addresses necessary for find_conversation() and
+conversation_new() are taken from the pinfo structure (as is commonly done)
+and no 'options' are used.
+
+
+2.2.1.5 The conversation_add_proto_data function.
Once you have created a conversation with conversation_new, you can
associate data with it using this function.
The conversation_add_proto_data prototype:
void conversation_add_proto_data(conversation_t *conv, int proto,
- void *proto_data);
+ void *proto_data);
Where:
conversation_t *conv = the conversation in question
unique protocol number created with proto_register_protocol. Protocols
are typically registered in the proto_register_XXXX section of your
dissector. "data" is a pointer to the data you wish to associate with the
-conversation. Using the protocol number allows several dissectors to
+conversation. "data" usually points to "se_alloc'd" memory; the
+memory will be automatically freed each time a new dissection begins
+and thus need not be managed (freed) by the dissector.
+Using the protocol number allows several dissectors to
associate data with a given conversation.
-2.2.5 The conversation_get_proto_data function.
+2.2.1.6 The conversation_get_proto_data function.
After you have located a conversation with find_conversation, you can use
this function to retrieve any data associated with it.
Where:
conversation_t *conv = the conversation in question
int proto = registered protocol number
-
+
"conversation" is the conversation created with conversation_new. "proto"
-is a unique protocol number acreated with proto_register_protocol,
+is a unique protocol number created with proto_register_protocol,
typically in the proto_register_XXXX portion of a dissector. The function
returns a pointer to the data requested, or NULL if no data was found.
-2.2.6 The conversation_delete_proto_data function.
+2.2.1.7 The conversation_delete_proto_data function.
-After you are finished with a conversation, you can remove your assocation
+After you are finished with a conversation, you can remove your association
with this function. Please note that ONLY the conversation entry is
-removed. If you have allocated any memory for your data, you must free it
-as well.
+removed. If you have allocated any memory for your data (other than with se_alloc),
+ you must free it as well.
The conversation_delete_proto_data prototype:
void conversation_delete_proto_data(conversation_t *conv, int proto);
-
+
Where:
conversation_t *conv = the conversation in question
int proto = registered protocol number
"conversation" is the conversation created with conversation_new. "proto"
-is a unique protocol number acreated with proto_register_protocol,
+is a unique protocol number created with proto_register_protocol,
typically in the proto_register_XXXX portion of a dissector.
+2.2.1.8 The conversation_set_dissector function
-2.2.7 The example conversation code with GMemChunk's
+This function sets the protocol dissector to be invoked whenever
+conversation parameters (addresses, port_types, ports, etc) are matched
+during the dissection of a packet.
-For a conversation between two IP addresses and ports you can use this as an
-example. This example uses the GMemChunk to allocate memory and stores the data
-pointer in the conversation 'data' variable.
+The conversation_set_dissector prototype:
-NOTE: Remember to register the init routine (my_dissector_init) in the
-protocol_register routine.
+ void conversation_set_dissector(conversation_t *conversation, const dissector_handle_t handle);
+Where:
+ conversation_t *conv = the conversation in question
+ const dissector_handle_t handle = the dissector handle.
-/************************ Globals values ************************/
-/* the number of entries in the memory chunk array */
-#define my_init_count 10
+2.2.2 Using timestamps relative to the conversation
+
+There is a framework to calculate timestamps relative to the start of the
+conversation. First of all the timestamp of the first packet that has been
+seen in the conversation must be kept in the protocol data to be able
+to calculate the timestamp of the current packet relative to the start
+of the conversation. The timestamp of the last packet that was seen in the
+conversation should also be kept in the protocol data. This way the
+delta time between the current packet and the previous packet in the
+conversation can be calculated.
+
+So add the following items to the struct that is used for the protocol data:
+
+ nstime_t ts_first;
+ nstime_t ts_prev;
+
+The ts_prev value should only be set during the first run through the
+packets (ie pinfo->fd->flags.visited is false).
+
+Next step is to use the per-packet information (described in section 2.5)
+to keep the calculated delta timestamp, as it can only be calculated
+on the first run through the packets. This is because a packet can be
+selected in random order once the whole file has been read.
+
+After calculating the conversation timestamps, it is time to put them in
+the appropriate columns with the function 'col_set_time' (described in
+section 1.5.9). There are two columns for conversation timestamps:
+
+COL_REL_CONV_TIME, /* Relative time to beginning of conversation */
+COL_DELTA_CONV_TIME,/* Delta time to last frame in conversation */
+
+Last but not least, there MUST be a preference in each dissector that
+uses conversation timestamps that makes it possible to enable and
+disable the calculation of conversation timestamps. The main argument
+for this is that a higher level conversation is able to overwrite
+the values of lowel level conversations in these two columns. Being
+able to actively select which protocols may overwrite the conversation
+timestamp columns gives the user the power to control these columns.
+(A second reason is that conversation timestamps use the per-packet
+data structure which uses additional memory, which should be avoided
+if these timestamps are not needed)
+
+Have a look at the differences to packet-tcp.[ch] in SVN 22966 and
+SVN 23058 to see the implementation of conversation timestamps for
+the tcp-dissector.
+
+
+2.2.3 The example conversation code using se_alloc'd memory.
+
+For a conversation between two IP addresses and ports you can use this as an
+example. This example uses se_alloc() to allocate memory and stores the data
+pointer in the conversation 'data' variable.
+
+/************************ Global values ************************/
/* define your structure here */
typedef struct {
-}my_entry_t;
-
-/* the GMemChunk base structure */
-static GMemChunk *my_vals = NULL;
+} my_entry_t;
-/* Registered protocol number
+/* Registered protocol number */
static int my_proto = -1;
-
/********************* in the dissector routine *********************/
/* the local variables in the dissector */
conversation_t *conversation;
-my_entry_t *data_ptr
+my_entry_t *data_ptr;
/* look up the conversation */
-conversation = find_conversation( &pinfo->src, &pinfo->dst, pinfo->ptype,
- pinfo->srcport, pinfo->destport, 0);
+conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
+ pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
/* if conversation found get the data pointer that you stored */
-if ( conversation)
- data_ptr = (my_entry_t*)conversation_get_proto_data(conversation,
- my_proto);
+if (conversation)
+ data_ptr = (my_entry_t*)conversation_get_proto_data(conversation, my_proto);
else {
/* new conversation create local data structure */
- data_ptr = g_mem_chunk_alloc(my_protocol_vals);
+ data_ptr = se_alloc(sizeof(my_entry_t));
/*** add your code here to setup the new data structure ***/
/* create the conversation with your data pointer */
- conversation_new( &pinfo->src, &pinfo->dst, pinfo->ptype,
+ conversation = conversation_new(pinfo->fd->num, &pinfo->src, &pinfo->dst, pinfo->ptype,
pinfo->srcport, pinfo->destport, 0);
- conversation_add_proto_data(conversation, my_proto, (void *) data_ptr);
+ conversation_add_proto_data(conversation, my_proto, (void *)data_ptr);
}
/* at this point the conversation data is ready */
+/***************** in the protocol register routine *****************/
-/******************* in the dissector init routine *******************/
-
-#define my_init_count 20
-
-static void
-my_dissector_init( void){
-
- /* destroy memory chunks if needed */
-
- if ( my_vals)
- g_mem_chunk_destroy(my_vals);
-
- /* now create memory chunks */
+my_proto = proto_register_protocol("My Protocol", "My Protocol", "my_proto");
- my_vals = g_mem_chunk_new( "my_proto_vals",
- sizeof( _entry_t),
- my_init_count * sizeof( my_entry_t),
- G_ALLOC_AND_FREE);
-}
-/***************** in the protocol register routine *****************/
+2.2.4 An example conversation code that starts at a specific frame number.
-/* register re-init routine */
+Sometimes a dissector has determined that a new conversation is needed that
+starts at a specific frame number, when a capture session encompasses multiple
+conversation that reuse the same src/dest ip/port pairs. You can use the
+conversation->setup_frame returned by find_conversation with
+pinfo->fd->num to determine whether or not there already exists a conversation
+that starts at the specific frame number.
-register_init_routine( &my_dissector_init);
+/* in the dissector routine */
-my_proto = proto_register_protocol("My Protocol", "My Protocol", "my_proto");
+ conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
+ pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
+ if (conversation == NULL || (conversation->setup_frame != pinfo->fd->num)) {
+ /* It's not part of any conversation or the returned
+ * conversation->setup_frame doesn't match the current frame
+ * create a new one.
+ */
+ conversation = conversation_new(pinfo->fd->num, &pinfo->src,
+ &pinfo->dst, pinfo->ptype, pinfo->srcport, pinfo->destport,
+ NULL, 0);
+ }
-2.2.8 The example conversation code using conversation index field
+2.2.5 The example conversation code using conversation index field.
Sometimes the conversation isn't enough to define a unique data storage
value for the network traffic. For example if you are storing information
identifier that is used to define the request. In this case the
conversation and the identifier are required to find the data storage
pointer. You can use the conversation data structure index value to
-uniquely define the conversation.
+uniquely define the conversation.
See packet-afs.c for an example of how to use the conversation index. In
this dissector multiple requests are sent in the same conversation. To store
information for each request the dissector has an internal hash table based
-upon the conversation index and values inside the request packets.
+upon the conversation index and values inside the request packets.
-/* in the dissector routine */
+ /* in the dissector routine */
-/* to find a request value, first lookup conversation to get index */
-/* then used the conversation index, and request data to find data */
-/* in the local hash table */
+ /* to find a request value, first lookup conversation to get index */
+ /* then used the conversation index, and request data to find data */
+ /* in the local hash table */
- conversation = find_conversation(&pinfo->src, &pinfo->dst, pinfo->ptype,
- pinfo->srcport, pinfo->destport, 0);
- if (conversation == NULL) {
- /* It's not part of any conversation - create a new one. */
- conversation = conversation_new(&pinfo->src, &pinfo->dst, pinfo->ptype,
- pinfo->srcport, pinfo->destport, NULL, 0);
- }
+ conversation = find_or_create_conversation(pinfo);
- request_key.conversation = conversation->index;
+ request_key.conversation = conversation->index;
request_key.service = pntohs(&rxh->serviceId);
request_key.callnumber = pntohl(&rxh->callNumber);
- request_val = (struct afs_request_val *) g_hash_table_lookup(
+ request_val = (struct afs_request_val *)g_hash_table_lookup(
afs_request_hash, &request_key);
/* only allocate a new hash element when it's a request */
opcode = 0;
- if ( !request_val && !reply)
+ if (!request_val && !reply)
{
- new_request_key = g_mem_chunk_alloc(afs_request_keys);
+ new_request_key = se_alloc(sizeof(struct afs_request_key));
*new_request_key = request_key;
- request_val = g_mem_chunk_alloc(afs_request_vals);
+ request_val = se_alloc(sizeof(struct afs_request_val));
request_val -> opcode = pntohl(&afsh->opcode);
opcode = request_val->opcode;
-2.3 Dynamic conversation dissector registration
+2.3 Dynamic conversation dissector registration.
-NOTE: This sections assumes that all information is available to
+NOTE: This sections assumes that all information is available to
create a complete conversation, source port/address and
destination port/address. If either the destination port or
address is know, see section 2.4 Dynamic server port dissector
registration.
For protocols that negotiate a secondary port connection, for example
-packet-msproxy.c, a conversation can install a dissector to handle
+packet-msproxy.c, a conversation can install a dissector to handle
the secondary protocol dissection. After the conversation is created
for the negotiated ports use the conversation_set_dissector to define
the dissection routine.
+Before we create these conversations or assign a dissector to them we should
+first check that the conversation does not already exist and if it exists
+whether it is registered to our protocol or not.
+We should do this because it is uncommon but it does happen that multiple
+different protocols can use the same socketpair during different stages of
+an application cycle. By keeping track of the frame number a conversation
+was started in wireshark can still tell these different protocols apart.
The second argument to conversation_set_dissector is a dissector handle,
which is created with a call to create_dissector_handle or
register_dissector takes as arguments a string giving a name for the
dissector, a pointer to the dissector function, and a protocol ID.
-The protocol ID is the ID for the protocol dissected by the function.
+The protocol ID is the ID for the protocol dissected by the function.
The function will not be called if the protocol has been disabled by the
user; instead, the data for the protocol will be dissected as raw data.
static dissector_handle_t sub_dissector_handle;
/* prototype for the dynamic dissector */
-static void sub_dissector( tvbuff_t *tvb, packet_info *pinfo,
+static void sub_dissector(tvbuff_t *tvb, packet_info *pinfo,
proto_tree *tree);
/* in the main protocol dissector, where the next dissector is setup */
/* if conversation has a data field, create it and load structure */
- new_conv_info = g_mem_chunk_alloc( new_conv_vals);
- new_conv_info->data1 = value1;
+/* First check if a conversation already exists for this
+ socketpair
+*/
+ conversation = find_conversation(pinfo->fd->num,
+ &pinfo->src, &pinfo->dst, protocol,
+ src_port, dst_port, 0);
+
+/* If there is no such conversation, or if there is one but for
+ someone else's protocol then we just create a new conversation
+ and assign our protocol to it.
+*/
+ if ( (conversation == NULL) ||
+ (conversation->dissector_handle != sub_dissector_handle) ) {
+ new_conv_info = se_alloc(sizeof(struct _new_conv_info));
+ new_conv_info->data1 = value1;
/* create the conversation for the dynamic port */
- conversation = conversation_new( &pinfo->src, &pinfo->dst, protocol,
- src_port, dst_port, new_conv_info, 0);
+ conversation = conversation_new(pinfo->fd->num,
+ &pinfo->src, &pinfo->dst, protocol,
+ src_port, dst_port, new_conv_info, 0);
/* set the dissector for the new conversation */
- conversation_set_dissector(conversation, sub_dissector_handle);
-
+ conversation_set_dissector(conversation, sub_dissector_handle);
+ }
...
void
proto_register_PROTOABBREV(void)
-{
+{
...
sub_dissector_handle = create_dissector_handle(sub_dissector,
...
}
-2.4 Dynamic server port dissector registration
+2.4 Dynamic server port dissector registration.
NOTE: While this example used both NO_ADDR2 and NO_PORT2 to create a
conversation with only one port and address set, this isn't a
For protocols that define a server address and port for a secondary
protocol, a conversation can be used to link a protocol dissector to
-the server port and address. The key is to create the new
+the server port and address. The key is to create the new
conversation with the second address and port set to the "accept
-any" values.
+any" values.
+
+Some server applications can use the same port for different protocols during
+different stages of a transaction. For example it might initially use SNMP
+to perform some discovery and later switch to use TFTP using the same port.
+In order to handle this properly we must first check whether such a
+conversation already exists or not and if it exists we also check whether the
+registered dissector_handle for that conversation is "our" dissector or not.
+If not we create a new conversation on top of the previous one and set this new
+conversation to use our protocol.
+Since wireshark keeps track of the frame number where a conversation started
+wireshark will still be able to keep the packets apart even though they do use
+the same socketpair.
+ (See packet-tftp.c and packet-snmp.c for examples of this)
There are two support routines that will allow the second port and/or
-address to be set latter.
+address to be set later.
conversation_set_port2( conversation_t *conv, guint32 port);
conversation_set_addr2( conversation_t *conv, address addr);
These routines will change the second address or port for the
conversation. So, the server port conversation will be converted into a
more complete conversation definition. Don't use these routines if you
-want create a conversation between the server and client and retain the
+want to create a conversation between the server and client and retain the
server port definition, you must create a new conversation.
/* if conversation has a data field, create it and load structure */
- new_conv_info = g_mem_chunk_alloc( new_conv_vals);
+ new_conv_info = se_alloc(sizeof(struct _new_conv_info));
new_conv_info->data1 = value1;
/* create the conversation for the dynamic server address and port */
/* NOTE: The second address and port values don't matter because the */
/* NO_ADDR2 and NO_PORT2 options are set. */
- conversation = conversation_new( &server_src_addr, 0, protocol,
- server_src_port, 0, new_conv_info, NO_ADDR2 | NO_PORT2);
+/* First check if a conversation already exists for this
+ IP/protocol/port
+*/
+ conversation = find_conversation(pinfo->fd->num,
+ &server_src_addr, 0, protocol,
+ server_src_port, 0, NO_ADDR2 | NO_PORT_B);
+/* If there is no such conversation, or if there is one but for
+ someone else's protocol then we just create a new conversation
+ and assign our protocol to it.
+*/
+ if ( (conversation == NULL) ||
+ (conversation->dissector_handle != sub_dissector_handle) ) {
+ conversation = conversation_new(pinfo->fd->num,
+ &server_src_addr, 0, protocol,
+ server_src_port, 0, new_conv_info, NO_ADDR2 | NO_PORT2);
/* set the dissector for the new conversation */
- conversation_set_dissector(conversation, sub_dissector_handle);
-
+ conversation_set_dissector(conversation, sub_dissector_handle);
+ }
-2.5 Per packet information
+2.5 Per-packet information.
-Information can be stored for each data packet that is process by the dissector.
-The information is added with the p_add_proto_data function and retreived with the
-p_get_proto_data function. The data pointers passed into the p_add_proto_data are
-not managed by the proto_data routines. If you use malloc or any other dynamic
-memory allocation scheme, you must release the data when it isn't required.
+Information can be stored for each data packet that is processed by the
+dissector. The information is added with the p_add_proto_data function and
+retrieved with the p_get_proto_data function. The data pointers passed into
+the p_add_proto_data are not managed by the proto_data routines. If you use
+malloc or any other dynamic memory allocation scheme, you must release the
+data when it isn't required.
void
p_add_proto_data(frame_data *fd, int proto, void *proto_data)
void *
p_get_proto_data(frame_data *fd, int proto)
-Where:
+Where:
fd - The fd pointer in the pinfo structure, pinfo->fd
- proto - Protocol id returned by the proto_register_protocol call during initialization
+ proto - Protocol id returned by the proto_register_protocol call
+ during initialization
proto_data - pointer to the dissector data.
-2.6 User Preferences
+2.6 User Preferences.
If the dissector has user options, there is support for adding these preferences
to a configuration dialog.
You must register the module with the preferences routine with -
-module_t *prefs_register_protocol(proto_id, void (*apply_cb)(void))
+ module_t *prefs_register_protocol(proto_id, void (*apply_cb)(void))
+ or
+ module_t *prefs_register_protocol_subtree(const char *subtree, int id,
+ void (*apply_cb)(void));
-Where: proto_id - the value returned by "proto_register_protocol()" when
- the protocol was registered
- apply_cb - Callback routine that is call when preferences are applied
+Where: proto_id - the value returned by "proto_register_protocol()" when
+ the protocol was registered.
+ apply_cb - Callback routine that is called when preferences are
+ applied. It may be NULL, which inhibits the callback.
+ subtree - grouping preferences tree node name (several protocols can
+ be grouped under one preferences subtree)
-Then you can register the fields that can be configured by the user with these routines -
+Then you can register the fields that can be configured by the user with these
+routines -
/* Register a preference with an unsigned integral value. */
void prefs_register_uint_preference(module_t *module, const char *name,
/* Register a preference with an enumerated value. */
void prefs_register_enum_preference(module_t *module, const char *name,
const char *title, const char *description, gint *var,
- const enum_val *enumvals, gboolean radio_buttons)
+ const enum_val_t *enumvals, gboolean radio_buttons)
/* Register a preference with a character-string value. */
void prefs_register_string_preference(module_t *module, const char *name,
const char *title, const char *description, char **var)
+ /* Register a preference with a range of unsigned integers (e.g.,
+ * "1-20,30-40").
+ */
+ void prefs_register_range_preference(module_t *module, const char *name,
+ const char *title, const char *description, range_t *var,
+ guint32 max_value)
+
Where: module - Returned by the prefs_register_protocol routine
- name - This is appended to the name of the protocol, with a
- "." between them, to construct a name that
- identifies the field in the preference file;
- the name itself should not include the protocol
- name, as the name in the preference file will
- already have it
- title - Field title in the preferences dialog
- description - Comments added to the preference file above the
- preference value
+ name - This is appended to the name of the protocol, with a
+ "." between them, to construct a name that identifies
+ the field in the preference file; the name itself
+ should not include the protocol name, as the name in
+ the preference file will already have it. Make sure that
+ only lower-case ASCII letters, numbers, underscores and
+ dots appear in the preference name.
+ title - Field title in the preferences dialog
+ description - Comments added to the preference file above the
+ preference value and shown as tooltip in the GUI, or NULL
var - pointer to the storage location that is updated when the
- field is changed in the preference dialog box
- enumvals - an array of enum_val structures. This must be NULL terminated
- radio_buttons - Is the enumvals a list of radio buttons?
-
+ field is changed in the preference dialog box. Note that
+ with string preferences the given pointer is overwritten
+ with a pointer to a new copy of the string during the
+ preference registration. The passed-in string may be
+ freed, but you must keep another pointer to the string
+ in order to free it.
+ base - Base that the unsigned integer is expected to be in,
+ see strtoul(3).
+ enumvals - an array of enum_val_t structures. This must be
+ NULL-terminated; the members of that structure are:
+
+ a short name, to be used with the "-o" flag - it
+ should not contain spaces or upper-case letters,
+ so that it's easier to put in a command line;
+
+ a description, which is used in the GUI (and
+ which, for compatibility reasons, is currently
+ what's written to the preferences file) - it can
+ contain spaces, capital letters, punctuation,
+ etc.;
+
+ the numerical value corresponding to that name
+ and description
+ radio_buttons - TRUE if the field is to be displayed in the
+ preferences dialog as a set of radio buttons,
+ FALSE if it is to be displayed as an option
+ menu
+ max_value - The maximum allowed value for a range (0 is the minimum).
An example from packet-beep.c -
-
+
proto_beep = proto_register_protocol("Blocks Extensible Exchange Protocol",
"BEEP", "beep");
" than the default of 10288)",
10, &global_beep_tcp_port);
- prefs_register_bool_preference(beep_module, "strict_header_terminator",
- "BEEP Header Requires CRLF",
+ prefs_register_bool_preference(beep_module, "strict_header_terminator",
+ "BEEP Header Requires CRLF",
"Specifies that BEEP requires CRLF as a "
"terminator, and not just CR or LF",
&global_beep_strict_term);
"beep.strict_header_terminator", the first of which is an unsigned
integer and the second of which is a Boolean.
-2.7 Reassembly/desegmentation for protocols running atop TCP
+Note that a warning will pop up if you've saved such preference to the
+preference file and you subsequently take the code out. The way to make
+a preference obsolete is to register it as such:
+
+/* Register a preference that used to be supported but no longer is. */
+ void prefs_register_obsolete_preference(module_t *module,
+ const char *name);
+
+2.7 Reassembly/desegmentation for protocols running atop TCP.
-There are two main ways of reassembling PDUs spanning across multiple
-TCP segmentss. The first one is simpler, but assumes you are running
-atop of TCP when this occurs (but your dissector might run atop of UDP,
-too, for example), and that your PDUs consist of a fixed amount of data
-that includes enough information to determine the PDU length, possibly
-followed by additional data. The second one is more generic but
-requires more code and is less efficient.
+There are two main ways of reassembling a Protocol Data Unit (PDU) which
+spans across multiple TCP segments. The first approach is simpler, but
+assumes you are running atop of TCP when this occurs (but your dissector
+might run atop of UDP, too, for example), and that your PDUs consist of a
+fixed amount of data that includes enough information to determine the PDU
+length, possibly followed by additional data. The second method is more
+generic but requires more code and is less efficient.
-For the first method, you register two different dissection methods, on
+2.7.1 Using tcp_dissect_pdus().
+
+For the first method, you register two different dissection methods, one
for the TCP case, and one for the other cases. It is a good idea to
-have a dissect_PROTO_common function which will parse the generic
+also have a dissect_PROTO_common function which will parse the generic
content that you can find in all PDUs which is called from
dissect_PROTO_tcp when the reassembly is complete and from
dissect_PROTO_udp (or dissect_PROTO_other).
mdns_udp_handle = create_dissector_handle(dissect_mdns_udp,
proto_dns);
- dissector_add("udp.port", UDP_PORT_DNS, dns_udp_handle);
- dissector_add("tcp.port", TCP_PORT_DNS, dns_tcp_handle);
- dissector_add("udp.port", UDP_PORT_MDNS, mdns_udp_handle);
- dissector_add("tcp.port", TCP_PORT_MDNS, dns_tcp_handle);
+ dissector_add_uint("udp.port", UDP_PORT_DNS, dns_udp_handle);
+ dissector_add_uint("tcp.port", TCP_PORT_DNS, dns_tcp_handle);
+ dissector_add_uint("udp.port", UDP_PORT_MDNS, mdns_udp_handle);
+ dissector_add_uint("tcp.port", TCP_PORT_MDNS, dns_tcp_handle);
The dissect_dns_udp function does very little work and calls
dissect_dns_common, while dissect_dns_tcp calls tcp_dissect_pdus with a
get_dns_pdu_len, dissect_dns_tcp_pdu);
}
-(The dissect_dns_tcp_pdu function acts similarly to dissect_dns_udp.)
+(The dissect_dns_tcp_pdu function acts similarly to dissect_dns_udp.)
The arguments to tcp_dissect_pdus are:
the tvbuff pointer, packet_info pointer, and proto_tree pointer
the number of bytes of PDU data required to determine the length
of the PDU;
- a routine that takes as arguments a tvbuff pointer and an offset
- value representing the offset into the tvbuff at which a PDU
- begins and should return - *without* throwing an exception (it
- is guaranteed that the number of bytes specified by the previous
- argument to tcp_dissect_pdus is available, but more data might
- not be available, so don't refer to any data past that) - the
+ a routine that takes as arguments a packet_info pointer, a tvbuff
+ pointer and an offset value representing the offset into the tvbuff
+ at which a PDU begins and should return - *without* throwing an
+ exception (it is guaranteed that the number of bytes specified by the
+ previous argument to tcp_dissect_pdus is available, but more data
+ might not be available, so don't refer to any data past that) - the
total length of the PDU, in bytes;
a routine that's passed a tvbuff pointer, packet_info pointer,
and proto_tree pointer, with the tvbuff containing a
possibly-reassembled PDU, and that should dissect that PDU.
-The second method is to return a modified pinfo structure when
-dissect_PROTO is called. In this case, you have to check if you have
-collected enough bytes: if you have enough, you parse the PDU, and if
-don't have enough bytes, you return from the dissector supplying
-information to the caller on how many bytes you need to proceed. This
-is done by indicating the offset where you would like to start again and
-the number of bytes that you need in pinfo->desegment_*:
-
- if (i_miss_five_bytes) {
- pinfo->desegment_offset = offset;
- pinfo->desegment_len = 5;
- }
-
-You can repeat this procedure until you've got enough bytes; for
-example, you can request one byte more until you've got the byte you're
-searching for if the data to be dissected consists of a sequence of
-bytes ending with a particular byte value.
-
-3. Plugins
-
-See the README.plugins for more information on how to "pluginize"
-a dissector.
-
-4.0 Extending Wiretap.
-
-5.0 How the Display Filter Engine works
-
-code:
-epan/dfilter/* - the display filter engine, including
- scanner, parser, syntax-tree semantics checker, DFVM bytecode
- generator, and DFVM engine.
-epan/ftypes/* - the definitions of the various FT_* field types.
-epan/proto.c - proto_tree-related routines
-
-5.1 Parsing text
-
-The scanner/parser pair read the string representing the display filter
-and convert it into a very simple syntax tree. The syntax tree is very
-simple in that it is possible that many of the nodes contain unparsed
-chunks of text from the display filter.
-
-5.1 Enhancing the syntax tree.
-
-The semantics of the simple syntax tree are checked to make sure that
-the fields that are being compared are being compared to appropriate
-values. For example, if a field is an integer, it can't be compared to
-a string, unless a value_string has been defined for that field.
-
-During the process of checking the semantics, the simple syntax tree is
-fleshed out and no longer contains nodes with unparsed information. The
-syntax tree is no longer in its simple form, but in its complete form.
-
-5.2 Converting to DFVM bytecode
-
-The syntax tree is analyzed to create a sequence of bytecodes in the
-"DFVM" language. "DFVM" stands for Display Filter Virtual Machine. The
-DFVM is similar in spirit, but not in definition, to the BPF VM that
-libpcap uses to analyze packets.
+2.7.2 Modifying the pinfo struct.
+
+The second reassembly mode is preferred when the dissector cannot determine
+how many bytes it will need to read in order to determine the size of a PDU.
+It may also be useful if your dissector needs to support reassembly from
+protocols other than TCP.
+
+Your dissect_PROTO will initially be passed a tvbuff containing the payload of
+the first packet. It should dissect as much data as it can, noting that it may
+contain more than one complete PDU. If the end of the provided tvbuff coincides
+with the end of a PDU then all is well and your dissector can just return as
+normal. (If it is a new-style dissector, it should return the number of bytes
+successfully processed.)
+
+If the dissector discovers that the end of the tvbuff does /not/ coincide with
+the end of a PDU, (ie, there is half of a PDU at the end of the tvbuff), it can
+indicate this to the parent dissector, by updating the pinfo struct. The
+desegment_offset field is the offset in the tvbuff at which the dissector will
+continue processing when next called. The desegment_len field should contain
+the estimated number of additional bytes required for completing the PDU. Next
+time your dissect_PROTO is called, it will be passed a tvbuff composed of the
+end of the data from the previous tvbuff together with desegment_len more bytes.
+
+If the dissector cannot tell how many more bytes it will need, it should set
+desegment_len=DESEGMENT_ONE_MORE_SEGMENT; it will then be called again as soon
+as any more data becomes available. Dissectors should set the desegment_len to a
+reasonable value when possible rather than always setting
+DESEGMENT_ONE_MORE_SEGMENT as it will generally be more efficient. Also, you
+*must not* set desegment_len=1 in this case, in the hope that you can change
+your mind later: once you return a positive value from desegment_len, your PDU
+boundary is set in stone.
+
+static hf_register_info hf[] = {
+ {&hf_cstring,
+ {"C String", "c.string", FT_STRING, BASE_NONE, NULL, 0x0,
+ NULL, HFILL}
+ }
+ };
+
+/**
+* Dissect a buffer containing ASCII C strings.
+*
+* @param tvb The buffer to dissect.
+* @param pinfo Packet Info.
+* @param tree The protocol tree.
+**/
+static void dissect_cstr(tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
+{
+ guint offset = 0;
+ while(offset < tvb_reported_length(tvb)) {
+ gint available = tvb_reported_length_remaining(tvb, offset);
+ gint len = tvb_strnlen(tvb, offset, available);
+
+ if( -1 == len ) {
+ /* we ran out of data: ask for more */
+ pinfo->desegment_offset = offset;
+ pinfo->desegment_len = DESEGMENT_ONE_MORE_SEGMENT;
+ return;
+ }
+
+ col_set_str(pinfo->cinfo, COL_INFO, "C String");
+
+ len += 1; /* Add one for the '\0' */
+
+ if (tree) {
+ proto_tree_add_item(tree, hf_cstring, tvb, offset, len,
+ ENC_ASCII|ENC_NA);
+ }
+ offset += (guint)len;
+ }
+
+ /* if we get here, then the end of the tvb coincided with the end of a
+ string. Happy days. */
+}
-A virtual bytecode is created and used so that the actual process of
-filtering packets will be fast. That is, it should be faster to process
-a list of VM bytecodes than to attempt to filter packets directly from
-the syntax tree. (heh... no measurement has been made to support this
-supposition)
+This simple dissector will repeatedly return DESEGMENT_ONE_MORE_SEGMENT
+requesting more data until the tvbuff contains a complete C string. The C string
+will then be added to the protocol tree. Note that there may be more
+than one complete C string in the tvbuff, so the dissection is done in a
+loop.
+
+2.8 ptvcursors.
+
+The ptvcursor API allows a simpler approach to writing dissectors for
+simple protocols. The ptvcursor API works best for protocols whose fields
+are static and whose format does not depend on the value of other fields.
+However, even if only a portion of your protocol is statically defined,
+then that portion could make use of ptvcursors.
+
+The ptvcursor API lets you extract data from a tvbuff, and add it to a
+protocol tree in one step. It also keeps track of the position in the
+tvbuff so that you can extract data again without having to compute any
+offsets --- hence the "cursor" name of the API.
+
+The three steps for a simple protocol are:
+ 1. Create a new ptvcursor with ptvcursor_new()
+ 2. Add fields with multiple calls of ptvcursor_add()
+ 3. Delete the ptvcursor with ptvcursor_free()
+
+ptvcursor offers the possibility to add subtrees in the tree as well. It can be
+done in very simple steps :
+ 1. Create a new subtree with ptvcursor_push_subtree(). The old subtree is
+ pushed in a stack and the new subtree will be used by ptvcursor.
+ 2. Add fields with multiple calls of ptvcursor_add(). The fields will be
+ added in the new subtree created at the previous step.
+ 3. Pop the previous subtree with ptvcursor_pop_subtree(). The previous
+ subtree is again used by ptvcursor.
+Note that at the end of the parsing of a packet you must have popped each
+subtree you pushed. If it's not the case, the dissector will generate an error.
+
+To use the ptvcursor API, include the "ptvcursor.h" file. The PGM dissector
+is an example of how to use it. You don't need to look at it as a guide;
+instead, the API description here should be good enough.
+
+2.8.1 ptvcursor API.
+
+ptvcursor_t*
+ptvcursor_new(proto_tree* tree, tvbuff_t* tvb, gint offset)
+ This creates a new ptvcursor_t object for iterating over a tvbuff.
+You must call this and use this ptvcursor_t object so you can use the
+ptvcursor API.
+
+proto_item*
+ptvcursor_add(ptvcursor_t* ptvc, int hf, gint length, const guint encoding)
+ This will extract 'length' bytes from the tvbuff and place it in
+the proto_tree as field 'hf', which is a registered header_field. The
+pointer to the proto_item that is created is passed back to you. Internally,
+the ptvcursor advances its cursor so the next call to ptvcursor_add
+starts where this call finished. The 'encoding' parameter is relevant for
+certain type of fields (See above under proto_tree_add_item()).
+
+proto_item*
+ptvcursor_add_no_advance(ptvcursor_t* ptvc, int hf, gint length, const guint encoding)
+ Like ptvcursor_add, but does not advance the internal cursor.
-5.3 Filtering
+void
+ptvcursor_advance(ptvcursor_t* ptvc, gint length)
+ Advances the internal cursor without adding anything to the proto_tree.
-Once the DFVM bytecode has been produced, it's a simple matter of
-running the DFVM engine against the proto_tree from the packet
-dissection, using the DFVM bytecodes as instructions. If the DFVM
-bytecode is known before packet dissection occurs, the
-proto_tree-related code can be "primed" to store away pointers to
-field_info structures that are interesting to the display filter. This
-makes lookup of those field_info structures during the filtering process
-faster.
+void
+ptvcursor_free(ptvcursor_t* ptvc)
+ Frees the memory associated with the ptvcursor. You must call this
+after your dissection with the ptvcursor API is completed.
-6.0 Adding new capabilities.
+proto_tree*
+ptvcursor_push_subtree(ptvcursor_t* ptvc, proto_item* it, gint ett_subtree)
+ Pushes the current subtree in the tree stack of the cursor, creates a new
+one and sets this one as the working tree.
+void
+ptvcursor_pop_subtree(ptvcursor_t* ptvc);
+ Pops a subtree in the tree stack of the cursor
+
+proto_tree*
+ptvcursor_add_with_subtree(ptvcursor_t* ptvc, int hfindex, gint length,
+ const guint encoding, gint ett_subtree);
+ Adds an item to the tree and creates a subtree.
+If the length is unknown, length may be defined as SUBTREE_UNDEFINED_LENGTH.
+In this case, at the next pop, the item length will be equal to the advancement
+of the cursor since the creation of the subtree.
+
+proto_tree*
+ptvcursor_add_text_with_subtree(ptvcursor_t* ptvc, gint length,
+ gint ett_subtree, const char* format, ...);
+ Add a text node to the tree and create a subtree.
+If the length is unknown, length may be defined as SUBTREE_UNDEFINED_LENGTH.
+In this case, at the next pop, the item length will be equal to the advancement
+of the cursor since the creation of the subtree.
+
+2.8.2 Miscellaneous functions.
+
+tvbuff_t*
+ptvcursor_tvbuff(ptvcursor_t* ptvc)
+ Returns the tvbuff associated with the ptvcursor.
+
+gint
+ptvcursor_current_offset(ptvcursor_t* ptvc)
+ Returns the current offset.
+
+proto_tree*
+ptvcursor_tree(ptvcursor_t* ptvc)
+ Returns the proto_tree associated with the ptvcursor.
+void
+ptvcursor_set_tree(ptvcursor_t* ptvc, proto_tree *tree)
+ Sets a new proto_tree for the ptvcursor.
+proto_tree*
+ptvcursor_set_subtree(ptvcursor_t* ptvc, proto_item* it, gint ett_subtree);
+ Creates a subtree and adds it to the cursor as the working tree but does
+not save the old working tree.
-James Coe <jammer@cin.net>
-Gilbert Ramirez <gram@alumni.rice.edu>
-Jeff Foster <jfoste@woodward.com>
-Olivier Abad <oabad@cybercable.fr>
-Laurent Deniel <laurent.deniel@free.fr>
-Gerald Combs <gerald@ethereal.com>
-Guy Harris <guy@alum.mit.edu>
git.samba.org / obnox / wireshark / wip.git / blobdiff