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wireshark/epan/dissectors/packet-prp.c

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/* packet-prp.c
* Routines for PRP (Parallel Redundancy Protocol; IEC62439 Part 3) dissection
* Copyright 2007, Sven Meier <msv[AT]zhwin.ch>
* Copyright 2011, Martin Renold <reld[AT]zhaw.ch>
* Copyright 2011, Florian Reichert <refl [AT] zhaw.ch>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald[AT]wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/etypes.h>
#include <epan/prefs.h>
#define PRP_LAN_A 10
#define PRP_LAN_B 11
static const value_string prp_lan_vals[] = {
{PRP_LAN_A, "LAN A"},
{PRP_LAN_B, "LAN B"},
{0, NULL}
};
/**********************************************************/
/* Initialize the protocol and registered fields */
/**********************************************************/
void proto_register_prp(void);
static int proto_prp = -1;
/* Initialize trailer fields */
static int hf_prp_redundancy_control_trailer_sequence_nr = -1;
static int hf_prp_redundancy_control_trailer_lan = -1;
static int hf_prp_redundancy_control_trailer_size = -1;
static int hf_prp_redundancy_control_trailer_suffix = -1;
static int hf_prp_redundancy_control_trailer_version = -1;
/* Initialize the subtree pointers */
static gint ett_prp_redundancy_control_trailer = -1;
/* Code to actually dissect the packets */
static int
dissect_prp_redundancy_control_trailer(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void* data _U_)
{
proto_item *ti;
proto_tree *prp_tree;
guint i;
guint length;
guint offset;
guint16 lan_id;
guint16 lsdu_size;
guint16 prp1_suffix;
guint trailer_start;
guint trailer_length;
trailer_start = 0;
trailer_length = 0;
length = tvb_reported_length(tvb);
if(length < 14)
return 0;
/*
* This is horribly broken. It assumes the frame is an Ethernet
* frame, with a type field at an offset of 12 bytes from the header.
* That is not guaranteed to be true.
*
* Ideally, this should be a heuristic dissector registered in
* the "eth.trailer" heuristic dissector table (and it can
* be registered as "disabled by default" there); unfortunately,
* it needs to know the length of the entire frame for the
* PRP-0 heuristic, so it'd have to be passed that length
* out of band.
*/
if (!tvb_bytes_exist(tvb, 12, 2))
return 0;
if(ETHERTYPE_VLAN == tvb_get_ntohs(tvb, 12)) /* tagged frame */
{
offset = 18;
}
else /* untagged */
{
offset = 14;
}
if (!tree)
return tvb_captured_length(tvb);
/*
* Is there enough data in the packet to every try to search for a
* trailer?
*/
if (!tvb_bytes_exist(tvb, (length-4)+2, 2))
return 0; /* no */
/* search for PRP-0 trailer */
/* If the frame is > 64 bytes, the PRP-0 trailer is always at the end. */
/* If the frame is <= 64 bytes, the PRP-0 trailer may be anywhere (before the padding) */
for(i=length-4; i>=offset; i--)
{
lan_id = tvb_get_ntohs(tvb, (i+2)) >> 12;
lsdu_size = tvb_get_ntohs(tvb, (i+2)) & 0x0fff;
if(lsdu_size == i+4-offset && (lan_id == 0xa || lan_id == 0xb))
{
trailer_start = i;
trailer_length = 4;
break;
}
if (length > 64) {
break; /* don't search, just check the last position */
}
}
/* check for PRP-1 trailer */
/* PRP-1 trailer is always at the end of the frame, after any padding. */
{
lan_id = tvb_get_ntohs(tvb, length-4) >> 12;
lsdu_size = tvb_get_ntohs(tvb, length-4) & 0x0fff;
prp1_suffix = tvb_get_ntohs(tvb, length-2);
if(prp1_suffix == ETHERTYPE_PRP && (lan_id == 0xa || lan_id == 0xb))
{
/* We don't check the lsdu_size, we just display whether
it's correct. Helpful for testing, because different
definitions of the lsdu_size did exist. */
trailer_start = length-6;
trailer_length = 6;
}
}
if(trailer_length != 0)
{
/* create display subtree for the protocol */
ti = proto_tree_add_item(tree, proto_prp, tvb, trailer_start,
trailer_length, ENC_NA);
prp_tree = proto_item_add_subtree(ti, ett_prp_redundancy_control_trailer);
if (trailer_length == 4) {
ti = proto_tree_add_string(prp_tree, hf_prp_redundancy_control_trailer_version,
tvb, trailer_start, trailer_length, "PRP-0");
} else {
ti = proto_tree_add_string(prp_tree, hf_prp_redundancy_control_trailer_version,
tvb, trailer_start, trailer_length, "PRP-1");
}
proto_item_set_generated(ti);
proto_tree_add_item(prp_tree, hf_prp_redundancy_control_trailer_sequence_nr,
tvb, trailer_start, 2, ENC_BIG_ENDIAN);
proto_tree_add_item(prp_tree, hf_prp_redundancy_control_trailer_lan,
tvb, trailer_start+2, 2, ENC_BIG_ENDIAN);
if (trailer_length == 4) {
/* PRP-0 */
proto_tree_add_item(prp_tree, hf_prp_redundancy_control_trailer_size,
tvb, trailer_start+2, 2, ENC_BIG_ENDIAN);
} else {
/* PRP-1 */
int lsdu_size_correct = length-offset;
if (lsdu_size == lsdu_size_correct) {
proto_tree_add_uint_format(prp_tree, hf_prp_redundancy_control_trailer_size,
tvb, trailer_start+2, 2, lsdu_size,
"LSDU size: %d [correct]", lsdu_size);
} else {
proto_tree_add_uint_format(prp_tree, hf_prp_redundancy_control_trailer_size,
tvb, trailer_start+2, 2, lsdu_size,
"LSDU size: %d [WRONG, should be %d]", lsdu_size, lsdu_size_correct);
}
/* suffix */
proto_tree_add_item(prp_tree, hf_prp_redundancy_control_trailer_suffix,
tvb, trailer_start+4, 2, ENC_BIG_ENDIAN);
}
}
return tvb_captured_length(tvb);
}
/* Register the protocol with Wireshark */
void proto_register_prp(void)
{
static hf_register_info hf[] = {
/*trailer*/
{ &hf_prp_redundancy_control_trailer_sequence_nr,
{ "Sequence number", "prp.trailer.prp_sequence_nr",
FT_UINT16, BASE_DEC, NULL, 0x00,
NULL, HFILL }
},
{ &hf_prp_redundancy_control_trailer_lan,
{ "LAN", "prp.trailer.prp_lan",
FT_UINT16, BASE_DEC, VALS(prp_lan_vals), 0xf000,
NULL, HFILL }
},
{ &hf_prp_redundancy_control_trailer_size,
{ "Size", "prp.trailer.prp_size",
FT_UINT16, BASE_DEC, NULL, 0x0fff,
NULL, HFILL }
},
{ &hf_prp_redundancy_control_trailer_suffix,
{ "Suffix", "prp.trailer.prp1_suffix",
FT_UINT16, BASE_HEX, NULL, 0x00,
NULL, HFILL }
},
{ &hf_prp_redundancy_control_trailer_version,
{ "PRP Version", "prp.trailer.version",
FT_STRING, BASE_NONE, NULL, 0x00,
NULL, HFILL }
}
};
static gint *ett[] = {
&ett_prp_redundancy_control_trailer,
};
module_t *prp_module;
dissector_handle_t prp_handle;
/* Register the protocol name and description */
proto_prp = proto_register_protocol("Parallel Redundancy Protocol (IEC62439 Part 3)", "PRP", "prp");
/* Post dissectors (such as the trailer dissector for this protocol)
* get called for every single frame anyone loads into Wireshark.
* Since this protocol is not of general interest we disable this
* protocol by default.
*/
proto_disable_by_default(proto_prp);
prp_module = prefs_register_protocol(proto_prp, NULL);
prefs_register_obsolete_preference(prp_module, "enable");
/* Required function calls to register the header fields and subtree used */
proto_register_field_array(proto_prp, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
prp_handle = register_dissector("prp", dissect_prp_redundancy_control_trailer, proto_prp);
register_postdissector(prp_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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