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Add support for ModbusRTU over UDP. 

Bug: 12374
Change-Id: I2df806c902b932d87e82f6f097f7acce814e5040
Reviewed-on: https://code.wireshark.org/review/15126
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Graham Bloice <graham.bloice@trihedral.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This commit is contained in:
Michael Mann 2016-04-26 20:11:46 -04:00
parent 232b2de7bb
commit 3eef66b2c2
1 changed files with 56 additions and 46 deletions
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102
epan/dissectors/packet-mbtcp.c
View File

@ -215,59 +215,54 @@ classify_mbrtu_packet(packet_info *pinfo, tvbuff_t *tvb)
return QUERY_PACKET;
/* Special case for serial-captured packets that don't have an Ethernet header */
/* We may not have an Ethernet header or unique ports. */
/* Dig into these a little deeper to try to guess the message type */
if (!pinfo->srcport) {
/* The 'exception' bit is set, so this is a response */
if (func & 0x80) {
return RESPONSE_PACKET;
}
switch (func) {
case READ_COILS:
case READ_DISCRETE_INPUTS:
/* Only possible to get a response message of 8 bytes with Discrete or Coils */
if (len == 8) {
/* If this is, in fact, a response then the data byte count will be 3 */
/* This will correctly identify all messages except for those that are discrete or coil polls */
/* where the base address range happens to have 0x03 in the upper 16-bit address register */
if (tvb_get_guint8(tvb, 2) == 3) {
return RESPONSE_PACKET;
}
else {
return QUERY_PACKET;
}
}
else {
return RESPONSE_PACKET;
}
break;
case READ_HOLDING_REGS:
case READ_INPUT_REGS:
case WRITE_SINGLE_COIL:
case WRITE_SINGLE_REG:
if (len == 8) {
return QUERY_PACKET;
}
else {
return RESPONSE_PACKET;
}
break;
case WRITE_MULT_REGS:
case WRITE_MULT_COILS:
if (len == 8) {
/* The 'exception' bit is set, so this is a response */
if (func & 0x80) {
return RESPONSE_PACKET;
}
switch (func) {
case READ_COILS:
case READ_DISCRETE_INPUTS:
/* Only possible to get a response message of 8 bytes with Discrete or Coils */
if (len == 8) {
/* If this is, in fact, a response then the data byte count will be 3 */
/* This will correctly identify all messages except for those that are discrete or coil polls */
/* where the base address range happens to have 0x03 in the upper 16-bit address register */
if (tvb_get_guint8(tvb, 2) == 3) {
return RESPONSE_PACKET;
}
else {
return QUERY_PACKET;
}
break;
}
else {
return RESPONSE_PACKET;
}
break;
default:
return CANNOT_CLASSIFY;
break;
}
case READ_HOLDING_REGS:
case READ_INPUT_REGS:
case WRITE_SINGLE_COIL:
case WRITE_SINGLE_REG:
if (len == 8) {
return QUERY_PACKET;
}
else {
return RESPONSE_PACKET;
}
break;
case WRITE_MULT_REGS:
case WRITE_MULT_COILS:
if (len == 8) {
return RESPONSE_PACKET;
}
else {
return QUERY_PACKET;
}
break;
}
@ -782,6 +777,18 @@ dissect_mbrtu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
return tvb_captured_length(tvb);
}
static int
dissect_mbrtu_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
/* Make sure there's at least enough data to determine it's a Modbus packet */
/* 5 bytes is the smallest possible valid message (exception response) */
if (tvb_reported_length(tvb) < 5)
return 0;
return dissect_mbrtu_pdu(tvb, pinfo, tree, data);
}
/* Code to allow further dissection of Modbus data payload */
/* Common to both Modbus/TCP and Modbus RTU dissectors */
@ -1971,7 +1978,7 @@ proto_register_modbus(void)
/* Modbus RTU Preference - Default TCP Port, defaults to zero, allows custom user port. */
prefs_register_uint_preference(mbrtu_module, "tcp.port", "Modbus RTU Port",
"Set the TCP port for encapsulated Modbus RTU packets",
"Set the TCP/UDP port for encapsulated Modbus RTU packets",
10, &global_mbus_rtu_port);
/* Modbus Preference - Holding/Input Register format, this allows for deeper dissection of response data */
@ -2020,15 +2027,18 @@ void
proto_reg_handoff_mbrtu(void)
{
static unsigned int mbrtu_port = 0;
dissector_handle_t mbrtu_udp_handle = create_dissector_handle(dissect_mbrtu_udp, proto_mbrtu);
/* Make sure to use Modbus RTU Preferences field to determine default TCP port */
if(mbrtu_port != 0 && mbrtu_port != global_mbus_rtu_port){
dissector_delete_uint("tcp.port", mbrtu_port, mbrtu_handle);
dissector_delete_uint("udp.port", mbrtu_port, mbrtu_udp_handle);
}
if(global_mbus_rtu_port != 0 && mbrtu_port != global_mbus_rtu_port) {
dissector_add_uint("tcp.port", global_mbus_rtu_port, mbrtu_handle);
dissector_add_uint("udp.port", global_mbus_rtu_port, mbrtu_udp_handle);
}
mbrtu_port = global_mbus_rtu_port;