I assume that what you mean to say is that you want Ethereal to decode
some particular xyz protocol, which may be running over a udp or tcp
port in the range of 50000-60000. If so, then here's what I did to
solve a similar problem for a given xyz protocol built on top of udp:
1) Add a port preference and range (not required, but could be useful):
#include "prefs.h"
static unsigned int xyz_base_port = 50000;
static unsigned int xyz_port_range = 10001;
void
proto_register_xyz(void)
{
module_t *xyz_module;
...
xyz_module = prefs_register_protocol(proto_xyz,
proto_reg_handoff_xyz);
prefs_register_uint_preference(xyz_module, "base_port",
"XYZ UDP base port",
"Set the UDP base port for XYZ (Default port is 50000)",
10, &xyz_base_port);
prefs_register_uint_preference(xyz_module, "port_range",
"XYZ UDP port range",
"Set the range of UDP ports for XYZ (Default range is 10001)",
10, &xyz_port_range);
...
} /* proto_register_xyz() */
2) Register your dissector as a heuristic dissector:
void
proto_reg_handoff_xyz(void)
{
static int xyz_prefs_initialized = FALSE;
if ( !xyz_prefs_initialized )
{
heur_dissector_add("udp", dissect_xyz, proto_xyz);
xyz_prefs_initialized = TRUE;
}
} /* proto_reg_handoff_xyz() */
3) Change the dissector code to accommodate the requirements of a
heuristic dissector:
#define PORT_RANGE(port,range) \
(((pinfo->srcport >= (port)) && (pinfo->srcport < ((port)+(range))))
|| \
((pinfo->destport >= (port)) && (pinfo->destport <
((port)+(range)))))
static gboolean
dissect_xyz(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
if ( !PORT_RANGE(xyz_base_port, xyz_port_range) )
{
/* Check other criteria here, if applicable */
return (FALSE);
}
pinfo->current_proto = "XYZ";
...
return (TRUE);
} /* dissect_xyz() */
I think that should be it. If I've left anything out, check the
README.developer.
Regards,
Chris
-----Original Message-----
From: ethereal-dev-bounces@xxxxxxxxxxxx
[mailto:ethereal-dev-bounces@xxxxxxxxxxxx] On Behalf Of Glenn D Blanford
Jr
Sent: Thursday, March 24, 2005 8:37 PM
To: ethereal-dev@xxxxxxxxxxxx
Subject: [Ethereal-dev] ethereal and src/dest port
Does anyone know how to force Ethereal to choose a specific port
or port order?
Specifically I want to decode particular ports in the 50000-60000 range
(for a private network application)
but dont know whether they will be src or dest.
The peer will usually have a smaller port number like 1200 or 6000 ish
so the port hash always fails me (if the other port corresponds to
a somewhat-well-known port (1024-44152?)).
The "decode As" would work but I want to do it permanently and for a
range of
ports. I guess I am looking for a way to reverse the port search order
in
the hash.
Has anyone worked with this.
I would be grateful for your help.
Thank you,
Glenn Blanford
Lucent
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