/* packet-mbtcp.c * Routines for Modbus/TCP dissection * By Riaan Swart * Copyright 2001, Institute for Applied Computer Science * University of Stellenbosch * * See * * http://www.modicon.com/openmbus/ * * for information on Modbus/TCP. * * $Id: packet-mbtcp.c,v 1.14 2003/05/08 00:42:28 guy Exp $ * * Ethereal - Network traffic analyzer * By Gerald Combs * 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #ifdef HAVE_CONFIG_H # include "config.h" #endif #include #include #include #include #include #define DEBUG #define TCP_PORT_MBTCP 502 /* Modbus/TCP located on TCP port 502 */ /* Modbus protocol function codes */ #define read_coils 1 #define read_input_discretes 2 #define read_mult_regs 3 #define read_input_regs 4 #define write_coil 5 #define write_single_reg 6 #define read_except_stat 7 #define diagnostics 8 #define program_484 9 #define poll_484 10 #define get_comm_event_ctrs 11 #define get_comm_event_log 12 #define program_584_984 13 #define poll_584_984 14 #define force_mult_coils 15 #define write_mult_regs 16 #define report_slave_id 17 #define program_884_u84 18 #define reset_comm_link 19 #define read_genl_ref 20 #define write_genl_ref 21 #define mask_write_reg 22 #define read_write_reg 23 #define read_fifo_queue 24 #define program_ConCept 40 #define firmware_replace 125 #define program_584_984_2 126 #define report_local_addr_mb 127 /* Modbus protocol exception codes */ #define illegal_function 0x01 #define illegal_address 0x02 #define illegal_value 0x03 #define illegal_response 0x04 #define acknowledge 0x05 #define slave_busy 0x06 #define negative_ack 0x07 #define memory_err 0x08 #define gateway_unavailable 0x0a #define gateway_trgt_fail 0x0b /* return codes of function classifying packets as query/response */ #define query_packet 0 #define response_packet 1 #define cannot_classify 2 /* Modbus header */ typedef struct _modbus_hdr { guint8 unit_id; /* unit identifier (previously slave addr) */ guint8 function_code; /* Modbus function code */ } modbus_hdr; /* Modbus/TCP header, containing the Modbus header */ typedef struct _mbtcp_hdr { guint16 transaction_id; /* copied by svr, usually 0 */ guint16 protocol_id; /* always 0 */ guint16 len; /* len of data that follows */ modbus_hdr mdbs_hdr; /* mdbus hdr directly after mdbs/tcp hdr * * in packet */ } mbtcp_hdr; /* Initialize the protocol and registered fields */ static int proto_mbtcp = -1; static int hf_mbtcp_transid = -1; static int hf_mbtcp_protid = -1; static int hf_mbtcp_len = -1; static int hf_mbtcp_unitid = -1; static int hf_mbtcp_functioncode = -1; static int hf_modbus_reference = -1; static int hf_modbus_lreference = -1; static int hf_modbus_reftype = -1; static int hf_modbus_readref = -1; static int hf_modbus_writeref = -1; static int hf_modbus_wordcnt = -1; static int hf_modbus_readwordcnt = -1; static int hf_modbus_writewordcnt = -1; static int hf_modbus_bytecnt = -1; static int hf_modbus_lbytecnt = -1; static int hf_modbus_bitcnt = -1; static int hf_modbus_exceptioncode = -1; static int hf_modbus_andmask = -1; static int hf_modbus_ormask = -1; /* Initialize the subtree pointers */ static gint ett_mbtcp = -1; static gint ett_modbus_hdr = -1; static gint ett_group_hdr = -1; static int classify_packet(packet_info *pinfo) { /* see if nature of packets can be derived from src/dst ports */ /* if so, return as found */ if ( ( 502 == pinfo->srcport && 502 != pinfo->destport ) || ( 502 != pinfo->srcport && 502 == pinfo->destport ) ) { /* the slave is receiving queries on port 502 */ if ( 502 == pinfo->srcport ) return response_packet; else if ( 502 == pinfo->destport ) return query_packet; } /* else, cannot classify */ return cannot_classify; } /* Translate function to string, as given on p6 of * "Open Modbus/TCP Specification", release 1 by Andy Swales. */ static const value_string function_code_vals[] = { { read_coils, "Read coils" }, { read_input_discretes, "Read input discretes" }, { read_mult_regs, "Read multiple registers" }, { read_input_regs, "Read input registers" }, { write_coil, "Write coil" }, { write_single_reg, "Write single register" }, { read_except_stat, "Read exception status" }, { diagnostics, "Diagnostics" }, { program_484, "Program (484)" }, { poll_484, "Poll (484)" }, { get_comm_event_ctrs, "Get Comm. Event Counters" }, { get_comm_event_log, "Get Comm. Event Log" }, { program_584_984, "Program (584/984)" }, { poll_584_984, "Poll (584/984)" }, { force_mult_coils, "Force Multiple Coils" }, { write_mult_regs, "Write Multiple Registers" }, { report_slave_id, "Report Slave ID" }, { program_884_u84, "Program 884/u84" }, { reset_comm_link, "Reset Comm. Link (884/u84)" }, { read_genl_ref, "Read General Reference" }, { write_genl_ref, "Write General Reference" }, { mask_write_reg, "Mask Write Register" }, { read_write_reg, "Read Write Register" }, { read_fifo_queue, "Read FIFO Queue" }, { program_ConCept, "Program (ConCept)" }, { firmware_replace, "Firmware replacement" }, { program_584_984_2, "Program (584/984)" }, { report_local_addr_mb, "Report local address (Modbus)" }, { 0, NULL } }; static const value_string exception_code_vals[] = { { illegal_function, "Illegal function" }, { illegal_address, "Illegal data address" }, { illegal_value, "Illegal data value" }, { illegal_response, "Illegal response length" }, { acknowledge, "Acknowledge" }, { slave_busy, "Slave device busy" }, { negative_ack, "Negative acknowledge" }, { memory_err, "Memory parity error" }, { gateway_unavailable, "Gateway path unavailable" }, { gateway_trgt_fail, "Gateway target device failed to respond" }, { 0, NULL } }; /* Code to actually dissect the packets */ static void dissect_mbtcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) { /* Set up structures needed to add the protocol subtree and manage it */ mbtcp_hdr mh; proto_item *mi, *mf; proto_tree *mbtcp_tree, *modbus_tree, *group_tree; int offset, group_offset, packet_type; guint i; gint packet_len, payload_start, payload_len; char *func_string = "", pkt_type_str[9] = ""; char err_str[100] = ""; guint32 byte_cnt, group_byte_cnt, group_word_cnt; guint32 packet_num; /* num to uniquely identify different mbtcp * packets in one TCP packet */ guint8 exception_code; gboolean exception_returned; /* Make entries in Protocol column on summary display */ if (check_col(pinfo->cinfo, COL_PROTOCOL)) col_set_str(pinfo->cinfo, COL_PROTOCOL, "Modbus/TCP"); if (check_col(pinfo->cinfo, COL_INFO)) col_clear(pinfo->cinfo, COL_INFO); /* Make entries in Info column on summary display */ offset = 0; tvb_memcpy(tvb, (guint8 *)&mh, offset, sizeof(mbtcp_hdr)); mh.transaction_id = g_ntohs(mh.transaction_id); mh.protocol_id = g_ntohs(mh.protocol_id); mh.len = g_ntohs(mh.len); if ( mh.mdbs_hdr.function_code & 0x80 ) { exception_code = tvb_get_guint8(tvb, offset + sizeof(mbtcp_hdr)); mh.mdbs_hdr.function_code ^= 0x80; exception_returned = TRUE; } else { exception_code = 0; exception_returned = FALSE; } func_string = val_to_str(mh.mdbs_hdr.function_code, function_code_vals, "Unknown function (%u)"); if (check_col(pinfo->cinfo, COL_INFO)) { packet_type = classify_packet(pinfo); switch ( packet_type ) { case query_packet : strcpy(pkt_type_str, "query"); break; case response_packet : strcpy(pkt_type_str, "response"); break; case cannot_classify : strcpy(err_str, "Unable to classify as query or response."); strcpy(pkt_type_str, "unknown"); break; default : break; } if ( exception_returned ) strcpy(err_str, "Exception returned "); col_add_fstr(pinfo->cinfo, COL_INFO, "%8s [%2u pkt(s)]: trans: %5u; unit: %3u, func: %3u: %s. %s", pkt_type_str, 1, mh.transaction_id, (unsigned char) mh.mdbs_hdr.unit_id, (unsigned char) mh.mdbs_hdr.function_code, func_string, err_str); } /* build up protocol tree and iterate over multiple packets */ packet_num = 0; while (1) { packet_type = classify_packet(pinfo); packet_len = sizeof(mbtcp_hdr) - sizeof(modbus_hdr) + mh.len; /* if a tree exists, perform operations to add fields to it */ if (tree) { mi = proto_tree_add_protocol_format(tree, proto_mbtcp, tvb, offset, packet_len, "Modbus/TCP"); mbtcp_tree = proto_item_add_subtree(mi, ett_mbtcp); /* Add items to protocol tree specific to Modbus/TCP Modbus/TCP */ proto_tree_add_uint(mbtcp_tree, hf_mbtcp_transid, tvb, offset, 2, mh.transaction_id); proto_tree_add_uint(mbtcp_tree, hf_mbtcp_protid, tvb, offset + 2, 2, mh.protocol_id); proto_tree_add_uint(mbtcp_tree, hf_mbtcp_len, tvb, offset + 4, 2, mh.len); /* Add items to protocol tree specific to Modbus generic */ mf = proto_tree_add_text(mbtcp_tree, tvb, offset + 6, mh.len, "Modbus"); modbus_tree = proto_item_add_subtree(mf, ett_modbus_hdr); proto_tree_add_uint(modbus_tree, hf_mbtcp_unitid, tvb, offset + 6, 1, mh.mdbs_hdr.unit_id); mi = proto_tree_add_uint(modbus_tree, hf_mbtcp_functioncode, tvb, offset + 7, 1, mh.mdbs_hdr.function_code); /** detail payload as a function of exception/function code */ func_string = val_to_str(mh.mdbs_hdr.function_code, function_code_vals, "Unknown function"); payload_start = offset + 8; payload_len = mh.len - sizeof(modbus_hdr); if (exception_returned) { proto_item_set_text(mi, "function %u: %s. Exception: %s", mh.mdbs_hdr.function_code, func_string, val_to_str(exception_code, exception_code_vals, "Unknown exception code (%u)")); proto_tree_add_uint(modbus_tree, hf_modbus_exceptioncode, tvb, payload_start, 1, exception_code); } else { proto_item_set_text(mi, "function %u: %s", mh.mdbs_hdr.function_code, func_string); switch (mh.mdbs_hdr.function_code) { case read_coils: case read_input_discretes: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_bitcnt, tvb, payload_start + 2, 2, FALSE); } else if (packet_type == response_packet) { byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start, 1, byte_cnt); proto_tree_add_text(modbus_tree, tvb, payload_start + 1, byte_cnt, "Data"); } break; case read_mult_regs: case read_input_regs: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_wordcnt, tvb, payload_start + 2, 2, FALSE); } else if (packet_type == response_packet) { byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start, 1, byte_cnt); proto_tree_add_text(modbus_tree, tvb, payload_start + 1, byte_cnt, "Data"); } break; case write_coil: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_text(modbus_tree, tvb, payload_start + 2, 1, "Data"); proto_tree_add_text(modbus_tree, tvb, payload_start + 3, 1, "Padding"); } else if (packet_type == response_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_text(modbus_tree, tvb, payload_start + 2, 1, "Data"); proto_tree_add_text(modbus_tree, tvb, payload_start + 3, 1, "Padding"); } break; case write_single_reg: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_text(modbus_tree, tvb, payload_start + 2, 2, "Data"); } else if (packet_type == response_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_text(modbus_tree, tvb, payload_start + 2, 2, "Data"); } break; case read_except_stat: if (packet_type == response_packet) proto_tree_add_text(modbus_tree, tvb, payload_start, 1, "Data"); break; case force_mult_coils: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_bitcnt, tvb, payload_start + 2, 2, FALSE); byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start + 4); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start + 4, 1, byte_cnt); proto_tree_add_text(modbus_tree, tvb, payload_start + 5, byte_cnt, "Data"); } else if (packet_type == response_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_bitcnt, tvb, payload_start + 2, 2, FALSE); } break; case write_mult_regs: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_wordcnt, tvb, payload_start + 2, 2, FALSE); byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start + 4); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start + 4, 1, byte_cnt); proto_tree_add_text(modbus_tree, tvb, payload_start + 5, byte_cnt, "Data"); } else if (packet_type == response_packet) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_wordcnt, tvb, payload_start + 2, 2, FALSE); } break; case read_genl_ref: if (packet_type == query_packet) { byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start, 1, byte_cnt); /* add subtrees to describe each group of packet */ group_offset = payload_start + 1; for (i = 0; i < byte_cnt / 7; i++) { mi = proto_tree_add_text( modbus_tree, tvb, group_offset, 7, "Group %u", i); group_tree = proto_item_add_subtree(mi, ett_group_hdr); proto_tree_add_item(group_tree, hf_modbus_reftype, tvb, group_offset, 1, FALSE); proto_tree_add_item(group_tree, hf_modbus_lreference, tvb, group_offset + 1, 4, FALSE); proto_tree_add_item(group_tree, hf_modbus_wordcnt, tvb, group_offset + 5, 2, FALSE); group_offset += 7; } } else if (packet_type == response_packet) { byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start, 1, byte_cnt); /* add subtrees to describe each group of packet */ group_offset = payload_start + 1; i = 0; while (byte_cnt > 0) { group_byte_cnt = (guint32)tvb_get_guint8(tvb, group_offset); mi = proto_tree_add_text( modbus_tree, tvb, group_offset, group_byte_cnt + 1, "Group %u", i); group_tree = proto_item_add_subtree(mi, ett_group_hdr); proto_tree_add_uint(group_tree, hf_modbus_bytecnt, tvb, group_offset, 1, group_byte_cnt); proto_tree_add_item(group_tree, hf_modbus_reftype, tvb, group_offset + 1, 1, FALSE); proto_tree_add_text(group_tree, tvb, group_offset + 2, group_byte_cnt - 1, "Data"); group_offset += (group_byte_cnt + 1); byte_cnt -= (group_byte_cnt + 1); i++; } } break; case write_genl_ref: if ((packet_type == query_packet) || (packet_type == response_packet)) { byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start, 1, byte_cnt); /* add subtrees to describe each group of packet */ group_offset = payload_start + 1; i = 0; while (byte_cnt > 0) { group_word_cnt = tvb_get_ntohs(tvb, group_offset + 5); group_byte_cnt = (2 * group_word_cnt) + 7; mi = proto_tree_add_text( modbus_tree, tvb, group_offset, group_byte_cnt, "Group %u", i); group_tree = proto_item_add_subtree(mi, ett_group_hdr); proto_tree_add_item(group_tree, hf_modbus_reftype, tvb, group_offset, 1, FALSE); proto_tree_add_item(group_tree, hf_modbus_lreference, tvb, group_offset + 1, 4, FALSE); proto_tree_add_uint(group_tree, hf_modbus_wordcnt, tvb, group_offset + 5, 2, group_word_cnt); proto_tree_add_text(group_tree, tvb, group_offset + 7, group_byte_cnt - 7, "Data"); group_offset += group_byte_cnt; byte_cnt -= group_byte_cnt; i++; } } break; case mask_write_reg: if ((packet_type == query_packet) || (packet_type == response_packet)) { proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_andmask, tvb, payload_start + 2, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_ormask, tvb, payload_start + 4, 2, FALSE); } break; case read_write_reg: if (packet_type == query_packet) { proto_tree_add_item(modbus_tree, hf_modbus_readref, tvb, payload_start, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_readwordcnt, tvb, payload_start + 2, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_writeref, tvb, payload_start + 4, 2, FALSE); proto_tree_add_item(modbus_tree, hf_modbus_writewordcnt, tvb, payload_start + 6, 2, FALSE); byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start + 8); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start + 8, 1, byte_cnt); proto_tree_add_text(modbus_tree, tvb, payload_start + 9, byte_cnt, "Data"); } else if (packet_type == response_packet) { byte_cnt = (guint32)tvb_get_guint8(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_bytecnt, tvb, payload_start, 1, byte_cnt); proto_tree_add_text(modbus_tree, tvb, payload_start + 1, byte_cnt, "Data"); } break; case read_fifo_queue: if (packet_type == query_packet) proto_tree_add_item(modbus_tree, hf_modbus_reference, tvb, payload_start, 2, FALSE); else if (packet_type == response_packet) { byte_cnt = (guint32)tvb_get_ntohs(tvb, payload_start); proto_tree_add_uint(modbus_tree, hf_modbus_lbytecnt, tvb, payload_start, 2, byte_cnt); proto_tree_add_item(modbus_tree, hf_modbus_wordcnt, tvb, payload_start + 2, 2, FALSE); proto_tree_add_text(modbus_tree, tvb, payload_start + 4, byte_cnt - 2, "Data"); } break; case diagnostics: case program_484: case poll_484: case get_comm_event_ctrs: case get_comm_event_log: case program_584_984: case poll_584_984: case report_slave_id: case program_884_u84: case reset_comm_link: case program_ConCept: case firmware_replace: case program_584_984_2: case report_local_addr_mb: /* these function codes are not part of the Modbus/TCP specification */ default: if (payload_len > 0) proto_tree_add_text(modbus_tree, tvb, payload_start, payload_len, "Data"); break; } } } /* move onto next packet (if there) */ offset += packet_len; packet_num++; if (tvb_reported_length_remaining(tvb, offset) > 0) { /* load header structure for next packet */ tvb_memcpy(tvb, (guint8 *)&mh, offset, sizeof(mbtcp_hdr)); mh.transaction_id = g_ntohs(mh.transaction_id); mh.protocol_id = g_ntohs(mh.protocol_id); mh.len = g_ntohs(mh.len); if ( mh.mdbs_hdr.function_code & 0x80 ) { exception_code = tvb_get_guint8(tvb, offset + sizeof(mbtcp_hdr)); mh.mdbs_hdr.function_code ^= 0x80; exception_returned = TRUE; } else exception_returned = FALSE; } else break; } } /* Register the protocol with Ethereal */ void proto_register_modbus(void) { /* Setup list of header fields See Section 1.6.1 for details*/ static hf_register_info hf[] = { /* Modbus/TCP header fields */ { &hf_mbtcp_transid, { "transaction identifier", "modbus_tcp.trans_id", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_mbtcp_protid, { "protocol identifier", "modbus_tcp.prot_id", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_mbtcp_len, { "length", "modbus_tcp.len", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, /* Modbus header fields */ { &hf_mbtcp_unitid, { "unit identifier", "modbus_tcp.unit_id", FT_UINT8, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_mbtcp_functioncode, { "function code", "modbus_tcp.func_code", FT_UINT8, BASE_DEC, VALS(function_code_vals), 0x0, "", HFILL } }, { &hf_modbus_reference, { "reference number", "modbus_tcp.reference_num", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_lreference, { "reference number (32 bit)", "modbus_tcp.reference_num_32", FT_UINT32, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_reftype, { "reference type", "modbus_tcp.reference_type", FT_UINT8, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_readref, { "read reference number", "modbus_tcp.read_reference_num", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_writeref, { "write reference number", "modbus_tcp.write_reference_num", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_wordcnt, { "word count", "modbus_tcp.word_cnt", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_readwordcnt, { "read word count", "modbus_tcp.read_word_cnt", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_writewordcnt, { "write word count", "modbus_tcp.write_word_cnt", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_bitcnt, { "bit count", "modbus_tcp.bit_cnt", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_bytecnt, { "byte count", "modbus_tcp.byte_cnt", FT_UINT8, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_lbytecnt, { "byte count (16-bit)", "modbus_tcp.byte_cnt_16", FT_UINT8, BASE_DEC, NULL, 0x0, "", HFILL } }, { &hf_modbus_exceptioncode, { "exception code", "modbus_tcp.exception_code", FT_UINT8, BASE_DEC, VALS(exception_code_vals), 0x0, "", HFILL } }, { &hf_modbus_andmask, { "AND mask", "modbus_tcp.and_mask", FT_UINT16, BASE_HEX, NULL, 0x0, "", HFILL } }, { &hf_modbus_ormask, { "OR mask", "modbus_tcp.or_mask", FT_UINT16, BASE_HEX, NULL, 0x0, "", HFILL } } }; /* Setup protocol subtree array */ static gint *ett[] = { &ett_mbtcp, &ett_modbus_hdr, &ett_group_hdr }; /* Register the protocol name and description */ proto_mbtcp = proto_register_protocol("Modbus/TCP", "Modbus/TCP", "mbtcp"); /* Required function calls to register the header fields and subtrees used */ proto_register_field_array(proto_mbtcp, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); } /* If this dissector uses sub-dissector registration add a registration routine. This format is required because a script is used to find these routines and create the code that calls these routines. */ void proto_reg_handoff_mbtcp(void) { dissector_handle_t mbtcp_handle; mbtcp_handle = create_dissector_handle(dissect_mbtcp, proto_mbtcp); dissector_add("tcp.port", TCP_PORT_MBTCP, mbtcp_handle); }