$Id$
tapping with stats_tree

Let's suppose that you want to write a tap only to keep counters, and you
don't want to get involved with GUI programming or maybe you'd like to make
it a plugin. A stats_tree might be the way to go. The stats_tree module takes
care of the representation (GUI for wireshark and text for tshark) of the
tap data. So there's very little code to write to make a tap listener usable
from both wireshark and tshark.

First, you should add the TAP to the dissector in question as described in
README.tapping .

Once the dissector in question is "tapped" you have to write the stats tree
code which is made of three parts:

The init callback routine:
   which will be executed before any packet is passed to the tap. Here you
   should create the "static" nodes of your tree. As well as initialize your
   data.
   
The (per)packet callback routine:
   As the tap_packet callback is going to be called for every packet, it
   should be used to increment the counters.
   
The cleanup callback:
   It is called at the destruction of the stats_tree and might be used to
   free ....

Other than that the stats_tree should be registered.

If you want to make it a plugin, stats_tree_register() should be called by
plugin_register_tap_listener() read README.plugin for other information
regarding wireshark plugins.

If you want it as part of the dissector stats_tree_register() can be called
either by proto_register_xxx() or if you prefer by proto_reg_handoff_xxx().


A small example of a very basic stats_tree plugin follows.

----- example stats_tree plugin ------
/* udpterm_stats_tree.c
 * A small example of stats_tree plugin that counts udp packets by termination
 * 2005, Luis E. G. Ontanon
 *
 * $ ~Id:  $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"

#ifndef ENABLE_STATIC
#include <gmodule.h>
#else
#include <glib.h>
#endif

#include <epan/stats_tree.h>
#include <epan/dissectors/udp.h>

static int st_udp_term;
static gchar* st_str_udp_term = "UDP terminations";

/* this one initializes the tree, creating the root nodes */
extern void udp_term_stats_tree_init(stats_tree* st) {
	/* we create a node under which we'll add every termination */
	st_udp_term = stats_tree_create_node(st, st_str_udp_term, 0, TRUE);	
}

/* this one will be called with every udp packet */
extern int udp_term_stats_tree_packet(stats_tree *st, /* st as it was passed to us */ 
                                      packet_info *pinfo,  /* we'll fetch the addresses from here */
                                      epan_dissect_t *edt _U_, /* unused */ 
                                      const void *p) /* we'll use this to fetch the ports */
{
	static guint8 str[128];
	e_udphdr* udphdr = (e_udphdr*) p;
	
	/* we increment by one (tick) the root node */
	stats_tree_tick_node(st, st_udp_term, 0, FALSE);
	
	/* we then tick a node for this src_addr:src_port
	   if the node doesn't exists it will be created */
	g_snprintf(str, sizeof(str),"%s:%u",address_to_str(&pinfo->net_src),udphdr->sport);
	tick_stat_node(st, str, st_udp_term, FALSE);

	/* same thing for dst */
	g_snprintf(str, sizeof(str),"%s:%u",address_to_str(&pinfo->net_dst),udphdr->dport);
	tick_stat_node(st, str, st_udp_term, FALSE);
	
	return 1;
}

#ifndef ENABLE_STATIC
WS_DLL_PUBLIC_DEF const gchar version[] = "0.0";

WS_DLL_PUBLIC_DEF void plugin_register_tap_listener(void) {

    stats_tree_register("udp", /* the proto we are going to "tap" */
                        "udp_terms", /* the abbreviation for this tree (to be used as -z udp_terms,tree) */
                        st_str_udp_term, /* the name of the menu and window (use "/" for sub menus)*/
                        0, /* tap listener flags for per-packet callback */
                        udp_term_stats_tree_packet, /* the per packet callback */
                        udp_term_stats_tree_init, /* the init callback */
                        NULL ); /* the cleanup callback (in this case there isn't) */

}
#endif

----- END ------

the stats_tree API
==================
 every stats_tree callback has a stats_tree* parameter (st), stats_tree is an obscure
 data structure which should be passed to the api functions.

stats_tree_register( tapname, abbr, name, flags, packet_cb, init_cb, cleanup_cb);
 registers a new stats tree

stats_tree_parent_id_by_name( st, parent_name)
  returns the id of a candidate parent node given its name 


Node functions
==============

All the functions that operate on nodes return a parent_id

stats_tree_create_node(st, name, parent_id, with_children)
  Creates a node in the tree (to be used in the in init_cb)
    name: the name of the new node
    parent_id: the id of the parent_node (NULL for root)
    with_children: TRUE if this node will have "dynamically created" children
                   (i.e. it will be a candidate parent)


stats_tree_create_node_by_pname(st, name, parent_name, with_children);
  As before but creates a node using its parent's name


stats_tree_create_range_node(st, name, parent_id, ...)
stats_tree_create_range_node_string(st, name, parent_id, num_str_ranges, str_ranges)
stats_tree_range_node_with_pname(st, name, parent_name, ...)
  Creates a node in the tree, that will contain a ranges list.
    example:
       stats_tree_create_range_node(st,name,parent_id,
				"-99","100-199","200-299","300-399","400-", NULL);

stats_tree_tick_range( st, name,  parent_id, value_in_range);
stats_tree_tick_range_by_pname(st,name,parent_name,value_in_range)
   Increases by one the ranged node and the sub node to whose range the value belongs


stats_tree_create_pivot(st, name, parent_id);
stats_tree_create_pivot_by_pname(st, name, parent_name);
  Creates a "pivot node"

stats_tree_tick_pivot(st, pivot_id, pivoted_string);
 Each time a pivot node will be ticked it will get increased, and, it will
 increase (or create) the children named as pivoted_string


the following will either increase or create a node (with value 1) when called

tick_stat_node(st,name,parent_id,with_children)
increases by one a stat_node

increase_stat_node(st,name,parent_id,with_children,value)
increases by value a stat_node

set_stat_node(st,name,parent_id,with_children,value)
sets the value of a stat_node

zero_stat_node(st,name,parent_id,with_children)
resets to zero a stat_node


You can find more examples of these in $srcdir/plugins/stats_tree/pinfo_stats_tree.c

Luis E. G. Ontanon.
