wireshark/epan/dissectors/packet-rlm.c

/* packet-rlm.c
 * Routines for RLM dissection
 * Copyright 2004, Duncan Sargeant <dunc-ethereal@rcpt.to>
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

/*
 * RLM is a proprietary Cisco protocol used for centralling managing
 * many redundant NASes.  I don't know much about the format, but you
 * can read about the feature here:
 *
 * http://www.cisco.com/en/US/docs/ios/12_0t/12_0t3/feature/guide/rlm_123.html
 *
 * RLM runs on a UDP port (default 3000) between the MGC and the NAS.
 * On port N+1 (default 3001), a Q.931/LAPD/UDP connection is maintained.
 * Both sides use the same local port number for the connection, so source
 * and dest port are always the same.
 *
 * In large networks, the links are typically split onto higher ports,
 * so anything up to 3015 (or higher) could either be RLM or Q.931 traffic,
 * although always the RLM has the one lower port number for that RLM group.
 *
 * Multiple RLM groups are possible on a single NAS.
 *
 * I haven't been able to find the protocol documented, so I've
 * guessed some of the fields based on the output of debug commands on
 * cisco NASes.
 *
 */

#include "config.h"

#include <epan/packet.h>

void proto_register_rlm(void);
void proto_reg_handoff_rlm(void);

/* Initialize the protocol and registered fields */
static int proto_rlm = -1;

static int hf_rlm_version = -1;
static int hf_rlm_type = -1;
static int hf_rlm_unknown = -1;
static int hf_rlm_tid = -1;
static int hf_rlm_unknown2 = -1;

/* Initialize the subtree pointers */
static gint ett_rlm = -1;


/* RLM definitions - missing some! */

#define RLM_START_REQUEST	1
#define RLM_START_ACK		2
/* #define ???	3 */
/* #define ???	4 */
#define RLM_ECHO_REQUEST	5
#define RLM_ECHO_REPLY		6
/* #define ???	?? */

/* Code to actually dissect the packets */
static gboolean
dissect_rlm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
	proto_item *ti;
	proto_tree *rlm_tree;
	guint8 rlm_type, version;
	const char *type_str = NULL;

	if (pinfo->srcport < 3000 || pinfo->srcport > 3015
			|| pinfo->destport < 3000 || pinfo->destport > 3015
			|| pinfo->destport != pinfo->srcport)
		return FALSE;

	if (tvb_captured_length(tvb) < 2)
		return FALSE;

	version  = tvb_get_guint8(tvb, 0);
	rlm_type = tvb_get_guint8(tvb, 1);

	/* we only know about version 2, and I've only seen 8 byte packets */
	if (tvb_captured_length(tvb) != 8 || version != 2) {
		return FALSE;
	}

	col_set_str(pinfo->cinfo, COL_PROTOCOL, "RLM");

	switch (rlm_type) {
		case RLM_START_REQUEST:
			type_str = "Start request";
			break;

		case RLM_START_ACK:
			type_str = "Start acknowledgement";
			break;

		case RLM_ECHO_REQUEST:
			type_str = "Echo request";
			break;

		case RLM_ECHO_REPLY:
			type_str = "Echo reply";
			break;

		default:
			type_str = "Unknown type";
			break;
	}

	col_set_str(pinfo->cinfo, COL_INFO, type_str);

	if (tree) {
		/* proto_tree_add_protocol_format(tree, proto_rlm, tvb, 0,
			16, "Cisco Session Management"); */
		ti = proto_tree_add_item(tree, proto_rlm, tvb, 0, 8, ENC_NA);
		rlm_tree = proto_item_add_subtree(ti, ett_rlm);
		proto_tree_add_item(rlm_tree, hf_rlm_version, tvb, 0, 1, ENC_BIG_ENDIAN);
		proto_tree_add_uint_format_value(rlm_tree, hf_rlm_type, tvb, 1, 1, rlm_type, "%u (%s)", rlm_type, type_str);
		proto_tree_add_item(rlm_tree, hf_rlm_unknown, tvb, 2, 2, ENC_BIG_ENDIAN);
		proto_tree_add_item(rlm_tree, hf_rlm_tid, tvb, 4, 2, ENC_BIG_ENDIAN);
		proto_tree_add_item(rlm_tree, hf_rlm_unknown2, tvb, 6, 2, ENC_BIG_ENDIAN);
	}

	return TRUE;
}


/* 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_reg_handoff_rlm(void)
{
	heur_dissector_add("udp", dissect_rlm, "Redundant Link Management over UDP", "rlm_udp", proto_rlm, HEURISTIC_ENABLE);
}

void
proto_register_rlm(void)
{

/* Setup list of header fields  See Section 1.6.1 for details*/
	static hf_register_info hf[] = {
		{ &hf_rlm_version,
			{ "Version",           "rlm.version",
			FT_UINT8, BASE_DEC, NULL, 0x0,
			NULL, HFILL }
		},
		{ &hf_rlm_type,
			{ "Type",           "rlm.type",
			FT_UINT8, BASE_DEC, NULL, 0x0,
			NULL, HFILL }
		},
		{ &hf_rlm_unknown,
			{ "Unknown",           "rlm.unknown",
			FT_UINT16, BASE_HEX, NULL, 0x0,
			NULL, HFILL }
		},
		{ &hf_rlm_tid,
			{ "Transaction ID",           "rlm.tid",
			FT_UINT16, BASE_DEC, NULL, 0x0,
			NULL, HFILL }
		},
		{ &hf_rlm_unknown2,
			{ "Unknown",           "rlm.unknown2",
			FT_UINT16, BASE_HEX, NULL, 0x0,
			NULL, HFILL }
		},
	};

/* Setup protocol subtree array */
	static gint *ett[] = {
		&ett_rlm,
	};

/* Register the protocol name and description */
	proto_rlm = proto_register_protocol("Redundant Link Management Protocol",
	    "RLM", "rlm");

/* Required function calls to register the header fields and subtrees used */
	proto_register_field_array(proto_rlm, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 8
 * tab-width: 8
 * indent-tabs-mode: t
 * End:
 *
 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 * :indentSize=8:tabSize=8:noTabs=false:
 */