wireshark/doc/packet-PROTOABBREV.c

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/* packet-PROTOABBREV.c
* Routines for PROTONAME dissection
* Copyright YEARS, YOUR_NAME <YOUR_EMAIL_ADDRESS>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: LICENSE
*/
/*
* (A short description of the protocol including links to specifications,
* detailed documentation, etc.)
*/
#include "config.h"
/* Define the name for the logging domain (try to avoid collisions with existing domains) */
#define WS_LOG_DOMAIN "PROTOABBREV"
/* Global header providing a minimum base set of required macros and APIs */
#include <wireshark.h>
#if 0
/* "System" includes used only as needed */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
...
#endif
#include <epan/packet.h> /* Required dissection API header */
#include <epan/expert.h> /* Include only as needed */
#include <epan/prefs.h> /* Include only as needed */
#if 0
/* IF AND ONLY IF your protocol dissector exposes code to other dissectors
* (which most dissectors don't need to do) then the 'public' prototypes and
* data structures can go in the header file packet-PROTOABBREV.h. If not, then
* a header file is not needed at all and this #include statement can be
* removed. */
#include "packet-PROTOABBREV.h"
#endif
/* Some protocols may need code from other dissectors, as here for
* ssl_dissector_add()
*/
#include "packet-tls.h"
/* Prototypes */
/* (Required to prevent [-Wmissing-prototypes] warnings */
void proto_reg_handoff_PROTOABBREV(void);
void proto_register_PROTOABBREV(void);
/* Initialize the protocol and registered fields */
static int proto_PROTOABBREV = -1;
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static int hf_FIELDABBREV = -1;
static expert_field ei_PROTOABBREV_EXPERTABBREV = EI_INIT;
static dissector_handle_t PROTOABBREV_handle;
static dissector_handle_t PROTOABBREV_tls_handle;
/* Global sample preference ("controls" display of numbers) */
static gboolean pref_hex = FALSE;
/* Global sample port preference - real port preferences should generally
* default to "" (for a range) or 0 (for a single uint) unless there is an
* IANA-registered (or equivalent) port for your protocol. */
#define PROTOABBREV_TLS_PORT 5678
static guint tls_port_pref = PROTOABBREV_TLS_PORT;
#define PROTOABBREV_TCP_PORTS "1234"
static range_t *tcp_port_range = PROTOABBREV_TCP_PORTS;
/* Initialize the subtree pointers */
static gint ett_PROTOABBREV = -1;
/* A sample #define of the minimum length (in bytes) of the protocol data.
* If data is received with fewer than this many bytes it is rejected by
* the current dissector. */
#define PROTOABBREV_MIN_LENGTH 8
/* Code to actually dissect the packets */
static int
dissect_PROTOABBREV(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
/* Set up structures needed to add the protocol subtree and manage it */
proto_item *ti, *expert_ti;
proto_tree *PROTOABBREV_tree;
/* Other misc. local variables. */
guint offset = 0;
int len = 0;
/*** HEURISTICS ***/
/* 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 the packet is long enough for it to belong to us. */
if (tvb_reported_length(tvb) < PROTOABBREV_MIN_LENGTH)
return 0;
/* Check that there's enough data present to run the heuristics. If there
* isn't, reject the packet; it will probably be dissected as data and if
* the user wants it dissected despite it being short they can use the
* "Decode-As" functionality. If your heuristic needs to look very deep into
* the packet you may not want to require *all* data to be present, but you
* should ensure that the heuristic does not access beyond the captured
* length of the packet regardless. */
if (tvb_captured_length(tvb) < MAX_NEEDED_FOR_HEURISTICS)
return 0;
/* Fetch some values from the packet header using tvb_get_*(). If these
* values are not valid/possible in your protocol then return 0 to give
* some other dissector a chance to dissect it. */
if ( TEST_HEURISTICS_FAIL )
return 0;
/*** COLUMN DATA ***/
/* There are two normal columns to fill in: the 'Protocol' column which
* is narrow and generally just contains the constant string 'PROTOABBREV',
* and the 'Info' column which can be much wider and contain misc. summary
* information (for example, the port number for TCP packets).
*
* 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 may be appending to the column later OR
* - you have constructed the string locally OR
* - the string was returned from a call to val_to_str()
* then use "col_add_str()" instead, as that takes a copy of the string.
*
* The function "col_add_fstr()" can be used instead of "col_add_str()"; it
* takes "printf()"-like arguments. Don't use "col_add_fstr()" with a format
* string of "%s" - just use "col_add_str()" or "col_set_str()", as it's
* more efficient than "col_add_fstr()".
*
* For full details see section 1.4 of README.dissector.
*/
/* Set the Protocol column to the constant string of PROTOABBREV */
col_set_str(pinfo->cinfo, COL_PROTOCOL, "PROTOABBREV");
#if 0
/* If you will be fetching any data from the packet before filling in
* the Info column, clear that column first in case the calls to fetch
* data from the packet throw an exception so that the Info column doesn't
* contain data left over from the previous dissector: */
col_clear(pinfo->cinfo, COL_INFO);
#endif
/* Some protocols need to be parsed differently for packets sent to the
* registered (server) port versus packets sent from the server port
* to an ephemeral client port.
*/
if (value_is_in_range(tcp_port_range, pinfo->destport)) {
col_set_str(pinfo->cinfo, COL_INFO, "XXX Request");
} else {
col_set_str(pinfo->cinfo, COL_INFO, "XXX Reply");
}
/*** PROTOCOL TREE ***/
/* Now we will create a sub-tree for our protocol and start adding fields
* to display under that sub-tree. Most of the time the only functions you
* will need are proto_tree_add_item() and proto_item_add_subtree().
*
* NOTE: The offset and length values in the call to proto_tree_add_item()
* define what data bytes to highlight in the hex display window when the
* line in the protocol tree display corresponding to that item is selected.
*
* Supplying a length of -1 tells Wireshark to highlight all data from the
* offset to the end of the packet.
*/
/* create display subtree for the protocol */
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 1.5 of README.dissector for more
* information. */
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expert_ti = proto_tree_add_item(PROTOABBREV_tree, hf_FIELDABBREV, tvb,
offset, len, ENC_xxx);
offset += len;
/* Some fields or situations may require "expert" analysis that can be
* specifically highlighted. */
if ( TEST_EXPERT_condition )
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/* value of hf_FIELDABBREV isn't what's expected */
expert_add_info(pinfo, expert_ti, &ei_PROTOABBREV_EXPERTABBREV);
/* Continue adding tree items to process the packet here... */
/* If this protocol has a sub-dissector call it here, see section 1.8 of
* README.dissector for more information. */
/* Return the amount of data this dissector was able to dissect (which may
* or may not be the total captured packet as we return here). */
return tvb_captured_length(tvb);
}
/* Register the protocol with Wireshark.
*
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* This format is required 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;
expert_module_t *expert_PROTOABBREV;
/* Setup list of header fields See Section 1.5 of README.dissector for
* details. */
static hf_register_info hf[] = {
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{ &hf_FIELDABBREV,
{ "FIELDNAME", "FIELDFILTERNAME",
FT_FIELDTYPE, FIELDDISPLAY, FIELDCONVERT, BITMASK,
"FIELDDESCR", HFILL }
}
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_PROTOABBREV
};
/* Setup protocol expert items */
static ei_register_info ei[] = {
{ &ei_PROTOABBREV_EXPERTABBREV,
{ "PROTOABBREV.EXPERTABBREV", PI_GROUP, PI_SEVERITY,
"EXPERTDESCR", EXPFILL }
}
};
/* Register the protocol name and description */
proto_PROTOABBREV = proto_register_protocol("PROTONAME",
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"PROTOSHORTNAME", "PROTOFILTERNAME");
/* Required function calls to register the header fields and subtrees */
proto_register_field_array(proto_PROTOABBREV, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
/* Required function calls to register expert items */
expert_PROTOABBREV = expert_register_protocol(proto_PROTOABBREV);
expert_register_field_array(expert_PROTOABBREV, ei, array_length(ei));
/* Use register_dissector() here so that the dissector can be
* found by name by other protocols, by Lua, by Export PDU,
* by custom User DLT dissection, etc. Some protocols may require
* multiple uniquely named dissectors that behave differently
* depending on the caller, e.g. over TCP directly vs over TLS.
*/
PROTOABBREV_handle = register_dissector("PROTOABBREV", dissect_PROTOABBREV,
proto_PROTOABBREV);
PROTOABBREV_tls_handle = register_dissector("PROTOABBREV.tls",
dissect_PROTOABBREV_tls, proto_PROTOABBREV);
/* Register a preferences module (see section 2.6 of README.dissector
* for more details). Registration of a prefs callback is not required
* if there are no preferences that affect protocol registration (an example
* of a preference that would affect registration is a port preference).
* If the 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 a preferences module under the preferences subtree.
* Only use this function instead of prefs_register_protocol (above) 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 using 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 simple example preference */
prefs_register_bool_preference(PROTOABBREV_module, "show_hex",
"Display numbers in Hex",
"Enable to display numerical values in hexadecimal.",
&pref_hex);
/* Register an example port preference */
prefs_register_uint_preference(PROTOABBREV_module, "tls.port", "PROTOABBREV TLS Port",
" PROTOABBREV TLS port if other than the default",
10, &tls_port_pref);
}
/* If this dissector uses sub-dissector registration add a registration routine.
* 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 Wireshark's
* preferences manager whenever "Apply" or "OK" are pressed. In that case, it
* should accommodate being called more than once by use of the static
* 'initialized' variable included below.
*
* This form of the reg_handoff function is used if you perform registration
* functions which are dependent upon prefs. See below this function 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 int current_tls_port_pref;
if (!initialized) {
/* Simple port preferences like TCP can be registered as automatic
* Decode As preferences.
*/
dissector_add_uint_range_with_preference("tcp.port", PROTOABBREV_TCP_PORTS, PROTOABBREV_handle);
initialized = TRUE;
} else {
/* If you perform registration functions which are dependent upon
* prefs then 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 value the preference had at the time you registered, which
* can be saved using local statics in this function (proto_reg_handoff).
*/
ssl_dissector_delete(current_tls_port_pref, PROTOABBREV_tls_handle);
}
/* Some port preferences, like TLS, are more complicated and cannot
* be done with auto preferences, because the TCP dissector has to call
* TLS for the particular port as well as TLS calling this dissector.
*/
ssl_dissector_add(tls_port_pref, PROTOABBREV_tls_handle);
current_tls_port = tls_port_pref;
/* Some protocols dissect packets going to the server port differently
* than packets coming from the server port. The current Decode As
* value can be retrieved here. Note that auto preferences are always
* a range, even if registered with dissector_add_uint_with_preference.
*/
tcp_port_range = prefs_get_range_value("PROTOABBREV", "tcp.port");
}
#if 0
/* Simpler 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_add_uint_range_with_preference("tcp.port", PROTOABBREV_TCP_PORTS, PROTOABBREV_handle);
}
#endif
/*
* Editor modelines - https://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:
*/