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wireshark/epan/dissectors/packet-mstp.c

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/* packet-mstp.c
* Routines for BACnet MS/TP datalink dissection
* Copyright 2008 Steve Karg <skarg@users.sourceforge.net> Alabama
*
* This is described in Clause 9 of ANSI/ASHRAE Standard 135-2004,
* BACnet - A Data Communication Protocol for Building Automation
* and Contrl Networks; clause 9 "describes a Master-Slave/Token-Passing
* (MS/TP) data link protocol, which provides the same services to the
* network layer as ISO 8802-2 Logical Link Control. It uses services
* provided by the EIA-485 physical layer." See section 9.3 for the
* frame format.
*
* 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"
#include <epan/packet.h>
#include <wiretap/wtap.h>
#include <epan/expert.h>
#include <epan/address_types.h>
#include <epan/to_str.h>
#include "packet-mstp.h"
void proto_register_mstp(void);
void proto_reg_handoff_mstp(void);
/* Probably should be a preference, but here for now */
#define BACNET_MSTP_SUMMARY_IN_TREE
#define BACNET_MSTP_CHECKSUM_VALIDATE
/* MS/TP Frame Type */
/* Frame Types 8 through 127 are reserved by ASHRAE. */
#define MSTP_TOKEN 0
#define MSTP_POLL_FOR_MASTER 1
#define MSTP_REPLY_TO_POLL_FOR_MASTER 2
#define MSTP_TEST_REQUEST 3
#define MSTP_TEST_RESPONSE 4
#define MSTP_BACNET_DATA_EXPECTING_REPLY 5
#define MSTP_BACNET_DATA_NOT_EXPECTING_REPLY 6
#define MSTP_REPLY_POSTPONED 7
static const value_string
bacnet_mstp_frame_type_name[] = {
{MSTP_TOKEN, "Token"},
{MSTP_POLL_FOR_MASTER, "Poll For Master"},
{MSTP_REPLY_TO_POLL_FOR_MASTER, "Reply To Poll For Master"},
{MSTP_TEST_REQUEST, "Test_Request"},
{MSTP_TEST_RESPONSE, "Test_Response"},
{MSTP_BACNET_DATA_EXPECTING_REPLY, "BACnet Data Expecting Reply"},
{MSTP_BACNET_DATA_NOT_EXPECTING_REPLY, "BACnet Data Not Expecting Reply"},
{MSTP_REPLY_POSTPONED, "Reply Postponed"},
/* Frame Types 128 through 255: Proprietary Frames */
{0, NULL }
};
static dissector_table_t subdissector_table;
static int proto_mstp = -1;
static gint ett_bacnet_mstp = -1;
static gint ett_bacnet_mstp_checksum = -1;
static int hf_mstp_preamble_55 = -1;
static int hf_mstp_preamble_FF = -1;
static int hf_mstp_frame_type = -1;
static int hf_mstp_frame_destination = -1;
static int hf_mstp_frame_source = -1;
static int hf_mstp_frame_vendor_id = -1;
static int hf_mstp_frame_pdu_len = -1;
static int hf_mstp_frame_crc8 = -1;
static int hf_mstp_frame_crc16 = -1;
static int hf_mstp_frame_checksum_status = -1;
static expert_field ei_mstp_frame_pdu_len = EI_INIT;
static expert_field ei_mstp_frame_checksum_bad = EI_INIT;
static int mstp_address_type = -1;
#if defined(BACNET_MSTP_CHECKSUM_VALIDATE)
/* Accumulate "dataValue" into the CRC in crcValue. */
/* Return value is updated CRC */
/* The ^ operator means exclusive OR. */
/* Note: This function is copied directly from the BACnet standard. */
static guint8
CRC_Calc_Header(
guint8 dataValue,
guint8 crcValue)
{
guint16 crc;
crc = crcValue ^ dataValue; /* XOR C7..C0 with D7..D0 */
/* Exclusive OR the terms in the table (top down) */
crc = crc ^ (crc << 1) ^ (crc << 2) ^ (crc << 3)
^ (crc << 4) ^ (crc << 5) ^ (crc << 6)
^ (crc << 7);
/* Combine bits shifted out left hand end */
return (crc & 0xfe) ^ ((crc >> 8) & 1);
}
#endif
#if defined(BACNET_MSTP_CHECKSUM_VALIDATE)
/* Accumulate "dataValue" into the CRC in crcValue. */
/* Return value is updated CRC */
/* The ^ operator means exclusive OR. */
/* Note: This function is copied directly from the BACnet standard. */
static guint16
CRC_Calc_Data(
guint8 dataValue,
guint16 crcValue)
{
guint16 crcLow;
crcLow = (crcValue & 0xff) ^ dataValue; /* XOR C7..C0 with D7..D0 */
/* Exclusive OR the terms in the table (top down) */
return (crcValue >> 8) ^ (crcLow << 8) ^ (crcLow << 3)
^ (crcLow << 12) ^ (crcLow >> 4)
^ (crcLow & 0x0f) ^ ((crcLow & 0x0f) << 7);
}
#endif
/* Common frame type text */
const gchar *
mstp_frame_type_text(guint32 val)
{
return val_to_str(val,
bacnet_mstp_frame_type_name,
"Unknown Frame Type (%u)");
}
static int mstp_str_len(const address* addr _U_)
{
return 5;
}
static int mstp_to_str(const address* addr, gchar *buf, int buf_len _U_)
{
*buf++ = '0';
*buf++ = 'x';
buf = bytes_to_hexstr(buf, (const guint8 *)addr->data, 1);
*buf = '\0'; /* NULL terminate */
return mstp_str_len(addr);
}
static const char* mstp_col_filter_str(const address* addr _U_, gboolean is_src)
{
if (is_src)
return "mstp.src";
return "mstp.dst";
}
static int mstp_len(void)
{
return 1;
}
/* dissects a BACnet MS/TP frame */
/* preamble 0x55 0xFF is not included in Cimetrics U+4 output */
void
dissect_mstp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
proto_tree *subtree, gint offset)
{
guint8 mstp_frame_type = 0;
guint16 mstp_frame_pdu_len = 0;
guint16 mstp_tvb_pdu_len = 0;
guint16 vendorid = 0;
tvbuff_t *next_tvb = NULL;
proto_item *item;
#if defined(BACNET_MSTP_CHECKSUM_VALIDATE)
/* used to calculate the crc value */
guint8 crc8 = 0xFF;
guint16 crc16 = 0xFFFF;
guint8 crcdata;
guint16 i; /* loop counter */
guint16 max_len = 0;
#endif
col_set_str(pinfo->cinfo, COL_PROTOCOL, "BACnet");
col_set_str(pinfo->cinfo, COL_INFO, "BACnet MS/TP");
mstp_frame_type = tvb_get_guint8(tvb, offset);
mstp_frame_pdu_len = tvb_get_ntohs(tvb, offset+3);
col_append_fstr(pinfo->cinfo, COL_INFO, " %s",
mstp_frame_type_text(mstp_frame_type));
/* Add the items to the tree */
proto_tree_add_item(subtree, hf_mstp_frame_type, tvb,
offset, 1, ENC_LITTLE_ENDIAN);
proto_tree_add_item(subtree, hf_mstp_frame_destination, tvb,
offset+1, 1, ENC_LITTLE_ENDIAN);
proto_tree_add_item(subtree, hf_mstp_frame_source, tvb,
offset+2, 1, ENC_LITTLE_ENDIAN);
item = proto_tree_add_item(subtree, hf_mstp_frame_pdu_len, tvb,
offset+3, 2, ENC_BIG_ENDIAN);
mstp_tvb_pdu_len = tvb_reported_length_remaining(tvb, offset+6);
/* check the length - which does not include the crc16 checksum */
if (mstp_tvb_pdu_len > 2) {
if (mstp_frame_pdu_len > (mstp_tvb_pdu_len-2)) {
expert_add_info(pinfo, item, &ei_mstp_frame_pdu_len);
}
}
#if defined(BACNET_MSTP_CHECKSUM_VALIDATE)
/* calculate checksum to validate */
for (i = 0; i < 5; i++) {
crcdata = tvb_get_guint8(tvb, offset+i);
crc8 = CRC_Calc_Header(crcdata, crc8);
}
crc8 = ~crc8;
proto_tree_add_checksum(subtree, tvb, offset+5, hf_mstp_frame_crc8, hf_mstp_frame_checksum_status, &ei_mstp_frame_checksum_bad, pinfo, crc8,
ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
#else
proto_tree_add_checksum(subtree, tvb, offset+5, hf_mstp_frame_crc8, hf_mstp_frame_checksum_status, &ei_mstp_frame_checksum_bad, pinfo, 0,
PROTO_CHECKSUM_NO_FLAGS);
#endif
/* dissect BACnet PDU if there is one */
offset += 6;
if (mstp_tvb_pdu_len > 2) {
/* remove the 16-bit crc checksum bytes */
mstp_tvb_pdu_len -= 2;
if (mstp_frame_type < 128) {
vendorid = 0;
next_tvb = tvb_new_subset_length(tvb, offset,
mstp_tvb_pdu_len);
} else {
/* With Vendor ID */
vendorid = tvb_get_ntohs(tvb, offset);
/* Write Vendor ID as tree */
proto_tree_add_item(subtree, hf_mstp_frame_vendor_id, tvb,
offset, 2, ENC_BIG_ENDIAN);
/* NPDU - call the Vendor specific dissector */
next_tvb = tvb_new_subset(tvb, offset+2,
mstp_tvb_pdu_len-2, mstp_frame_pdu_len);
}
if (!(dissector_try_uint(subdissector_table, (vendorid<<16) + mstp_frame_type,
next_tvb, pinfo, tree))) {
/* Unknown function - dissect the payload as data */
call_data_dissector(next_tvb, pinfo, tree);
}
#if defined(BACNET_MSTP_CHECKSUM_VALIDATE)
/* 16-bit checksum - calculate to validate */
max_len = MIN(mstp_frame_pdu_len, mstp_tvb_pdu_len);
for (i = 0; i < max_len; i++) {
crcdata = tvb_get_guint8(tvb, offset+i);
crc16 = CRC_Calc_Data(crcdata, crc16);
}
crc16 = ~crc16;
/* convert it to on-the-wire format */
crc16 = g_htons(crc16);
proto_tree_add_checksum(subtree, tvb, offset+mstp_frame_pdu_len, hf_mstp_frame_crc16, hf_mstp_frame_checksum_status, &ei_mstp_frame_checksum_bad, pinfo, crc16,
ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
#else
proto_tree_add_checksum(subtree, tvb, offset+mstp_frame_pdu_len, hf_mstp_frame_crc16, hf_mstp_frame_checksum_status, &ei_mstp_frame_checksum_bad, pinfo, 0,
ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);
#endif
}
}
static int
dissect_mstp_wtap(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_item *ti;
proto_tree *subtree;
gint offset = 0;
#ifdef BACNET_MSTP_SUMMARY_IN_TREE
guint8 mstp_frame_type = 0;
guint8 mstp_frame_source = 0;
guint8 mstp_frame_destination = 0;
#endif
/* set the MS/TP MAC address in the source/destination */
set_address_tvb(&pinfo->dl_dst, mstp_address_type, 1, tvb, offset+3);
copy_address_shallow(&pinfo->dst, &pinfo->dl_dst);
set_address_tvb(&pinfo->dl_src, mstp_address_type, 1, tvb, offset+4);
copy_address_shallow(&pinfo->src, &pinfo->dl_src);
#ifdef BACNET_MSTP_SUMMARY_IN_TREE
mstp_frame_type = tvb_get_guint8(tvb, offset+2);
mstp_frame_destination = tvb_get_guint8(tvb, offset+3);
mstp_frame_source = tvb_get_guint8(tvb, offset+4);
ti = proto_tree_add_protocol_format(tree, proto_mstp, tvb, offset, 8,
"BACnet MS/TP, Src (%u), Dst (%u), %s",
mstp_frame_source, mstp_frame_destination,
mstp_frame_type_text(mstp_frame_type));
#else
ti = proto_tree_add_item(tree, proto_mstp, tvb, offset, 8, ENC_NA);
#endif
subtree = proto_item_add_subtree(ti, ett_bacnet_mstp);
proto_tree_add_item(subtree, hf_mstp_preamble_55, tvb,
offset, 1, ENC_LITTLE_ENDIAN);
proto_tree_add_item(subtree, hf_mstp_preamble_FF, tvb,
offset+1, 1, ENC_LITTLE_ENDIAN);
dissect_mstp(tvb, pinfo, tree, subtree, offset+2);
return tvb_captured_length(tvb);
}
void
proto_register_mstp(void)
{
static hf_register_info hf[] = {
{ &hf_mstp_preamble_55,
{ "Preamble 55", "mstp.preamble_55",
FT_UINT8, BASE_HEX, NULL, 0,
"MS/TP Preamble 55", HFILL }
},
{ &hf_mstp_preamble_FF,
{ "Preamble FF", "mstp.preamble_FF",
FT_UINT8, BASE_HEX, NULL, 0,
"MS/TP Preamble FF", HFILL }
},
{ &hf_mstp_frame_type,
{ "Frame Type", "mstp.frame_type",
FT_UINT8, BASE_DEC, VALS(bacnet_mstp_frame_type_name), 0,
"MS/TP Frame Type", HFILL }
},
{ &hf_mstp_frame_destination,
{ "Destination Address", "mstp.dst",
FT_UINT8, BASE_DEC, NULL, 0,
"Destination MS/TP MAC Address", HFILL }
},
{ &hf_mstp_frame_source,
{ "Source Address", "mstp.src",
FT_UINT8, BASE_DEC, NULL, 0,
"Source MS/TP MAC Address", HFILL }
},
{ &hf_mstp_frame_vendor_id,
{ "VendorID", "mstp.vendorid",
FT_UINT16, BASE_DEC, NULL, 0,
"MS/TP Vendor ID of proprietary frametypes", HFILL }
},
{ &hf_mstp_frame_pdu_len,
{ "Length", "mstp.len",
FT_UINT16, BASE_DEC, NULL, 0,
"MS/TP Data Length", HFILL }
},
{ &hf_mstp_frame_crc8,
{ "Header CRC", "mstp.hdr_crc",
FT_UINT8, BASE_HEX, NULL, 0,
"MS/TP Header CRC", HFILL }
},
{ &hf_mstp_frame_crc16,
{ "Data CRC", "mstp.data_crc",
FT_UINT16, BASE_HEX, NULL, 0,
"MS/TP Data CRC", HFILL }
},
{ &hf_mstp_frame_checksum_status,
{ "Checksum status", "mstp.checksum.status",
FT_UINT8, BASE_NONE, VALS(proto_checksum_vals), 0x0,
NULL, HFILL }
},
};
static gint *ett[] = {
&ett_bacnet_mstp,
&ett_bacnet_mstp_checksum
};
static ei_register_info ei[] = {
{ &ei_mstp_frame_pdu_len, { "mstp.len.bad", PI_MALFORMED, PI_ERROR, "Length field value goes past the end of the payload", EXPFILL }},
{ &ei_mstp_frame_checksum_bad, { "mstp.checksum_bad.expert", PI_CHECKSUM, PI_WARN, "Bad Checksum", EXPFILL }},
};
expert_module_t* expert_mstp;
proto_mstp = proto_register_protocol("BACnet MS/TP",
"BACnet MS/TP", "mstp");
proto_register_field_array(proto_mstp, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
expert_mstp = expert_register_protocol(proto_mstp);
expert_register_field_array(expert_mstp, ei, array_length(ei));
register_dissector("mstp", dissect_mstp_wtap, proto_mstp);
subdissector_table = register_dissector_table("mstp.vendor_frame_type",
"MSTP Vendor specific Frametypes", proto_mstp, FT_UINT24, BASE_DEC, DISSECTOR_TABLE_NOT_ALLOW_DUPLICATE);
/* Table_type: (Vendor ID << 16) + Frametype */
mstp_address_type = address_type_dissector_register("AT_MSTP", "BACnet MS/TP Address", mstp_to_str, mstp_str_len, NULL, mstp_col_filter_str, mstp_len, NULL, NULL);
}
void
proto_reg_handoff_mstp(void)
{
dissector_handle_t mstp_handle;
dissector_handle_t bacnet_handle;
mstp_handle = find_dissector("mstp");
dissector_add_uint("wtap_encap", WTAP_ENCAP_BACNET_MS_TP, mstp_handle);
dissector_add_uint("wtap_encap", WTAP_ENCAP_BACNET_MS_TP_WITH_PHDR, mstp_handle);
bacnet_handle = find_dissector("bacnet");
dissector_add_uint("mstp.vendor_frame_type", (0/*VendorID ASHRAE*/ << 16) + MSTP_BACNET_DATA_EXPECTING_REPLY, bacnet_handle);
dissector_add_uint("mstp.vendor_frame_type", (0/*VendorID ASHRAE*/ << 16) + MSTP_BACNET_DATA_NOT_EXPECTING_REPLY, bacnet_handle);
}
/*
* Editor modelines - http://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:
*/
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