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wireshark/epan/dissectors/packet-pcomtcp.c

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/* packet-pcomtcp.c
* Routines for PCOM/TCP dissection
* Copyright 2018, Luis Rosa <lmrosa@dei.uc.pt>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
/*
* PCOM is a protocol to communicate with Unitronics PLCs either by serial or TCP.
* Two modes are available, ASCII and Binary.
*
* See https://unitronicsplc.com/Download/SoftwareUtilities/Unitronics%20PCOM%20Protocol.pdf
*
*/
#include <config.h>
#include <epan/packet.h>
#include <epan/expert.h>
void proto_reg_handoff_pcomtcp(void);
void proto_register_pcomtcp(void);
/* Initialize the protocol and registered fields */
static int proto_pcomtcp = -1;
static int proto_pcomascii = -1;
static int proto_pcombinary = -1;
static int hf_pcomtcp_transid = -1;
static int hf_pcomtcp_protocol = -1;
static int hf_pcomtcp_reserved = -1;
static int hf_pcomtcp_length = -1;
static int hf_pcomascii_stx = -1;
static int hf_pcomascii_unitid = -1;
static int hf_pcomascii_command = -1;
static int hf_pcomascii_checksum = -1;
static int hf_pcomascii_etx = -1;
static int hf_pcombinary_stx = -1;
static int hf_pcombinary_id = -1;
static int hf_pcombinary_reserved1 = -1;
static int hf_pcombinary_reserved2 = -1;
static int hf_pcombinary_reserved3 = -1;
static int hf_pcombinary_command = -1;
static int hf_pcombinary_reserved4 = -1;
static int hf_pcombinary_command_specific = -1;
static int hf_pcombinary_data_length = -1;
static int hf_pcombinary_header_checksum = -1;
static int hf_pcombinary_data = -1;
static int hf_pcombinary_footer_checksum = -1;
static int hf_pcombinary_etx = -1;
static expert_field ei_pcomtcp_reserved_bad_value = EI_INIT;
static expert_field ei_pcombinary_reserved1_bad_value = EI_INIT;
static expert_field ei_pcombinary_reserved2_bad_value = EI_INIT;
static expert_field ei_pcombinary_reserved3_bad_value = EI_INIT;
static expert_field ei_pcombinary_reserved4_bad_value = EI_INIT;
/* Initialize the subtree pointers */
static gint ett_pcomtcp = -1;
static gint ett_pcomascii = -1;
static gint ett_pcombinary = -1;
static dissector_handle_t pcomtcp_handle;
static dissector_handle_t pcomascii_handle;
static dissector_handle_t pcombinary_handle;
/* PCOM/TCP definitions */
#define PCOMTCP_MIN_LENGTH 6
#define PCOMTCP_TCP_PORT 20256
#define PCOM_ASCII 101
#define PCOM_BINARY 102
static guint global_pcomtcp_tcp_port = PCOMTCP_TCP_PORT; /* Port 20256, by default */
/* Translate pcomp_protocol to string */
static const value_string pcomp_protocol_vals[] = {
{ PCOM_ASCII, "ASCII mode" },
{ PCOM_BINARY, "Binary mode" },
{ 0, NULL },
};
/* Code to actually dissect the packets */
static int
dissect_pcomtcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
/* Set up structures needed to add the protocol subtree and manage it */
proto_item *ti;
proto_tree *pcomtcp_tree;
tvbuff_t *next_tvb;
guint offset = 0;
const char *pkt_type = "";
guint8 pcom_mode;
const char *pcom_mode_str = "";
proto_item *hf_pcomtcp_reserved_item = NULL;
/* Check that the packet is long enough for it to belong to us. */
if (tvb_reported_length(tvb) < PCOMTCP_MIN_LENGTH)
return 0;
pcom_mode = tvb_get_guint8(tvb, 2);
if ( pcom_mode != PCOM_ASCII && pcom_mode != PCOM_BINARY )
return 0;
pcom_mode_str = val_to_str(pcom_mode, pcomp_protocol_vals, "Unknown mode (%d)");
if (pinfo->srcport == global_pcomtcp_tcp_port )
pkt_type = "Reply";
else
pkt_type = "Query";
col_set_str(pinfo->cinfo, COL_PROTOCOL, "PCOM/TCP");
col_clear(pinfo->cinfo, COL_INFO);
col_add_fstr(pinfo->cinfo, COL_INFO, "%s in %s",
pkt_type, pcom_mode_str);
/* create display subtree for the protocol */
ti = proto_tree_add_item(tree, proto_pcomtcp, tvb, 0, -1, ENC_NA);
pcomtcp_tree = proto_item_add_subtree(ti, ett_pcomtcp);
proto_tree_add_item(pcomtcp_tree, hf_pcomtcp_transid, tvb,
offset, 2, ENC_LITTLE_ENDIAN);
offset += 2;
proto_tree_add_item(pcomtcp_tree, hf_pcomtcp_protocol, tvb,
offset, 1, ENC_NA);
offset += 1;
hf_pcomtcp_reserved_item = proto_tree_add_item(pcomtcp_tree, hf_pcomtcp_reserved, tvb,
offset, 1, ENC_NA);
if(tvb_get_guint8(tvb, offset) !=0){
expert_add_info_format(pinfo, hf_pcomtcp_reserved_item,
&ei_pcomtcp_reserved_bad_value,"Isn't 0");
}
offset += 1;
proto_tree_add_item(pcomtcp_tree, hf_pcomtcp_length, tvb,
offset, 2, ENC_LITTLE_ENDIAN);
/* dissect the PCOM Data */
offset += 2;
next_tvb = tvb_new_subset_length( tvb, offset, tvb_captured_length(tvb)-1);
if( tvb_reported_length_remaining(tvb, offset) > 0 ){
if ( pcom_mode == PCOM_ASCII)
call_dissector_with_data(pcomascii_handle, next_tvb, pinfo, tree, &pcom_mode);
else
call_dissector_with_data(pcombinary_handle, next_tvb, pinfo, tree, &pcom_mode);
}
return tvb_captured_length(tvb);
}
static int
dissect_pcomascii(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
/* Set up structures needed to add the protocol subtree and manage it */
proto_item *ti;
proto_tree *pcomascii_tree;
guint offset = 0;
/* Create protocol tree */
ti = proto_tree_add_item(tree, proto_pcomascii, tvb, offset, 0, ENC_NA);
pcomascii_tree = proto_item_add_subtree(ti, ett_pcomascii);
if (pinfo->srcport == global_pcomtcp_tcp_port ){ // Reply
proto_tree_add_item(pcomascii_tree, hf_pcomascii_stx, tvb,
offset, 2, ENC_ASCII|ENC_NA); // "/A"
offset += 2;
}else{
proto_tree_add_item(pcomascii_tree, hf_pcomascii_stx, tvb,
offset, 1, ENC_ASCII|ENC_NA); // "/"
offset += 1;
}
proto_tree_add_item(pcomascii_tree, hf_pcomascii_unitid, tvb,
offset, 2, ENC_ASCII|ENC_NA);
offset += 2;
if (pinfo->srcport == global_pcomtcp_tcp_port ){ // Reply
// (-2 stx -2 unitid -2 checksum -1 etx)
proto_tree_add_item(pcomascii_tree, hf_pcomascii_command, tvb,
offset, tvb_captured_length(tvb)-7, ENC_ASCII|ENC_NA);
offset += tvb_captured_length(tvb)-7;
}else{
// (-1 stx -2 unitid -2 checksum -1 etx)
proto_tree_add_item(pcomascii_tree, hf_pcomascii_command, tvb,
offset, tvb_captured_length(tvb)-6, ENC_ASCII|ENC_NA);
offset += tvb_captured_length(tvb)-6;
}
proto_tree_add_item(pcomascii_tree, hf_pcomascii_checksum, tvb,
offset, 2, ENC_LITTLE_ENDIAN);
offset += 2;
proto_tree_add_item(pcomascii_tree, hf_pcomascii_etx, tvb,
offset, 1, ENC_ASCII|ENC_NA);
return tvb_captured_length(tvb);
}
static int
dissect_pcombinary(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
void *data _U_)
{
/* Set up structures needed to add the protocol subtree and manage it */
proto_item *ti;
proto_tree *pcombinary_tree;
guint offset = 0;
proto_item *hf_pcombinary_reserved1_item = NULL;
proto_item *hf_pcombinary_reserved2_item = NULL;
proto_item *hf_pcombinary_reserved3_item = NULL;
proto_item *hf_pcombinary_reserved4_item = NULL;
/* Create protocol tree */
ti = proto_tree_add_item(tree, proto_pcombinary, tvb, offset, 0, ENC_NA);
pcombinary_tree = proto_item_add_subtree(ti, ett_pcombinary);
proto_tree_add_item(pcombinary_tree, hf_pcombinary_stx, tvb,
offset, 6, ENC_ASCII|ENC_NA);
offset += 6;
if (pinfo->srcport == global_pcomtcp_tcp_port){ //these bytes are transposed
hf_pcombinary_reserved1_item = proto_tree_add_item(pcombinary_tree,
hf_pcombinary_reserved1, tvb, offset, 1, ENC_NA);
if(tvb_get_guint8(tvb, offset) !=254){
expert_add_info_format(pinfo, hf_pcombinary_reserved1_item,
&ei_pcombinary_reserved1_bad_value,"Isn't 0xfe");
}
offset += 1;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_id, tvb,
offset, 1, ENC_NA);
offset += 1;
}else{
proto_tree_add_item(pcombinary_tree, hf_pcombinary_id, tvb,
offset, 1, ENC_NA);
offset += 1;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_reserved1, tvb,
offset, 1, ENC_NA);
offset += 1;
}
hf_pcombinary_reserved2_item = proto_tree_add_item(pcombinary_tree,
hf_pcombinary_reserved2, tvb, offset, 1, ENC_NA);
if( tvb_get_guint8(tvb, offset) !=1)
expert_add_info_format(pinfo, hf_pcombinary_reserved2_item,
&ei_pcombinary_reserved2_bad_value,"Isn't 1");
offset += 1;
hf_pcombinary_reserved3_item = proto_tree_add_item(pcombinary_tree,
hf_pcombinary_reserved3, tvb, offset, 3, ENC_LITTLE_ENDIAN);
if( tvb_get_letoh24(tvb,offset) != 0)
expert_add_info_format(pinfo, hf_pcombinary_reserved3_item,
&ei_pcombinary_reserved3_bad_value,"Isn't 0");
offset += 3;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_command, tvb,
offset, 1, ENC_NA);
offset += 1;
hf_pcombinary_reserved4_item = proto_tree_add_item(pcombinary_tree,
hf_pcombinary_reserved4, tvb, offset, 1, ENC_NA);
if( tvb_get_guint8(tvb, offset) !=0)
expert_add_info_format(pinfo, hf_pcombinary_reserved4_item,
&ei_pcombinary_reserved4_bad_value,"Isn't 0");
offset += 1;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_command_specific, tvb,
offset, 6, ENC_NA);
offset += 6;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_data_length, tvb,
offset, 2, ENC_LITTLE_ENDIAN);
offset += 2;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_header_checksum, tvb,
offset, 2, ENC_NA);
offset += 2;
if ((tvb_captured_length(tvb) - 27) > 0) // ( -3 footer - 24 header)
proto_tree_add_item(pcombinary_tree, hf_pcombinary_data, tvb,
offset, tvb_captured_length(tvb)-27, ENC_NA);
offset += (tvb_captured_length(tvb)-27);
proto_tree_add_item(pcombinary_tree, hf_pcombinary_footer_checksum, tvb,
offset, 2, ENC_LITTLE_ENDIAN);
offset += 2;
proto_tree_add_item(pcombinary_tree, hf_pcombinary_etx, tvb,
offset, 1, ENC_ASCII|ENC_NA);
return tvb_captured_length(tvb);
}
static void
apply_pcomtcp_prefs(void)
{
global_pcomtcp_tcp_port = prefs_get_uint_value("pcomtcp", "tcp.port");
}
void
proto_register_pcomtcp(void)
{
static hf_register_info hf_pcomtcp[] = {
{ &hf_pcomtcp_transid,
{ "Transaction Identifier", "pcomtcp.trans_id",
FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcomtcp_protocol,
{ "Protocol Mode", "pcomtcp.protocol",
FT_UINT8, BASE_DEC, VALS(pcomp_protocol_vals), 0x0,
NULL, HFILL }
},
{ &hf_pcomtcp_reserved,
{ "Reserved", "pcomtcp.reserved",
FT_UINT8, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcomtcp_length,
{ "Length (bytes)", "pcomtcp.length",
FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
};
static hf_register_info hf_pcomascii[] = {
{ &hf_pcomascii_stx,
{ "STX", "pcomascii.stx",
FT_STRING, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcomascii_unitid,
{ "Unit Identifier", "pcomascii.unitid",
FT_UINT16, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcomascii_command,
{ "Command", "pcomascii.command",
FT_STRING, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcomascii_checksum,
{ "Checksum", "pcomascii.checksum",
FT_UINT16, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcomascii_etx,
{ "ETX", "pcomascii.etx",
FT_STRING, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
};
static hf_register_info hf_pcombinary[] = {
{ &hf_pcombinary_stx,
{ "STX", "pcombinary.stx",
FT_STRING, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_id,
{ "ID (CANBUS or RS485)", "pcombinary.id",
FT_UINT8, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_reserved1,
{ "Reserved", "pcombinary.reserved1",
FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_reserved2,
{ "Reserved", "pcombinary.reserved2",
FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_reserved3,
{ "Reserved", "pcombinary.reserved3",
FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_command,
{ "Command", "pcombinary.command",
FT_BYTES, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_reserved4,
{ "Reserved", "pcombinary.reserved0",
FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_command_specific,
{ "Command Details", "pcombinary.command_specific",
FT_BYTES, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_data_length,
{ "Data Length", "pcombinary.data_length",
FT_UINT8, BASE_DEC, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_header_checksum,
{ "(Header) Checksum", "pcombinary.header_checksum",
FT_UINT16, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_data,
{ "Data", "pcombinary.data",
FT_BYTES, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_footer_checksum,
{ "(Footer) Checksum", "pcombinary.footer_checksum",
FT_UINT16, BASE_HEX, NULL, 0x0,
NULL, HFILL }
},
{ &hf_pcombinary_etx,
{ "ETX", "pcombinary.etx",
FT_STRING, BASE_NONE, NULL, 0x0,
NULL, HFILL }
},
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_pcomtcp,
&ett_pcomascii,
&ett_pcombinary
};
static ei_register_info pcomtcp_ei[] = {
{ &ei_pcomtcp_reserved_bad_value,
{ "pcombinary.reserved.bad_value", PI_PROTOCOL, PI_CHAT,
"Isn't 0", EXPFILL }
},
};
static ei_register_info pcombinary_ei[] = {
{ &ei_pcombinary_reserved1_bad_value,
{ "pcombinary.reserved1.bad_value", PI_PROTOCOL, PI_CHAT,
"Isn't 0xfe", EXPFILL }
},
{ &ei_pcombinary_reserved2_bad_value,
{ "pcombinary.reserved2.bad_value", PI_PROTOCOL, PI_CHAT,
"Isn't 1", EXPFILL }
},
{ &ei_pcombinary_reserved3_bad_value,
{ "pcombinary.reserved3.bad_value", PI_PROTOCOL, PI_CHAT,
"Isn't 0", EXPFILL }
},
{ &ei_pcombinary_reserved4_bad_value,
{ "pcombinary.reserved4.bad_value", PI_PROTOCOL, PI_CHAT,
"Isn't 0", EXPFILL }
},
};
expert_module_t* expert_pcomtcp;
expert_module_t* expert_pcombinary;
/* Register the protocol name and description */
proto_pcomtcp = proto_register_protocol("PCOM/TCP","PCOM/TCP", "pcomtcp");
proto_pcomascii = proto_register_protocol("PCOM ASCII","PCOM ASCII", "pcomascii");
proto_pcombinary = proto_register_protocol("PCOM BINARY","PCOM BINARY", "pcombinary");
pcomtcp_handle = register_dissector("pcomtcp", dissect_pcomtcp, proto_pcomtcp);
pcomascii_handle = register_dissector("pcomascii", dissect_pcomascii, proto_pcomascii);
pcombinary_handle = register_dissector("pcombinary", dissect_pcombinary, proto_pcombinary);
/* Required function calls to register the header fields and subtrees */
proto_register_field_array(proto_pcomtcp, hf_pcomtcp, array_length(hf_pcomtcp));
proto_register_field_array(proto_pcomascii, hf_pcomascii, array_length(hf_pcomascii));
proto_register_field_array(proto_pcombinary, hf_pcombinary, array_length(hf_pcombinary));
proto_register_subtree_array(ett, array_length(ett));
expert_pcomtcp = expert_register_protocol(proto_pcomtcp);
expert_pcombinary = expert_register_protocol(proto_pcombinary);
expert_register_field_array(expert_pcomtcp, pcomtcp_ei, array_length(pcomtcp_ei));
expert_register_field_array(expert_pcombinary, pcombinary_ei, array_length(pcombinary_ei));
prefs_register_protocol(proto_pcomtcp, apply_pcomtcp_prefs);
}
void
proto_reg_handoff_pcomtcp(void)
{
dissector_add_uint_with_preference("tcp.port", PCOMTCP_TCP_PORT, pcomtcp_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 4
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=4 tabstop=8 expandtab:
* :indentSize=4:tabSize=8:noTabs=true:
*/
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