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/* packet-udld.c
* Routines for the disassembly of the "UniDirectional Link Detection"
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/expert.h>
#include <epan/cisco_pid.h>
/*
* See
*
* https://tools.ietf.org/rfc/rfc5171
*
* for some information on UDLD.
*/
/* Offsets in TLV structure. */
#define TLV_TYPE 0
#define TLV_LENGTH 2
void proto_register_udld(void);
void proto_reg_handoff_udld(void);
static dissector_handle_t udld_handle;
static int proto_udld;
static int hf_udld_version;
static int hf_udld_opcode;
static int hf_udld_flags;
static int hf_udld_flags_rt;
static int hf_udld_flags_rsy;
static int hf_udld_checksum;
static int hf_udld_tlvtype;
static int hf_udld_tlvlength;
static int hf_udld_device_id;
static int hf_udld_sent_through_interface;
static int hf_udld_data;
static expert_field ei_udld_tlvlength;
static int ett_udld;
static int ett_udld_flags;
static int ett_udld_tlv;
#define TYPE_DEVICE_ID 0x0001
#define TYPE_PORT_ID 0x0002
#define TYPE_ECHO 0x0003
#define TYPE_MESSAGE_INTERVAL 0x0004
#define TYPE_TIMEOUT_INTERVAL 0x0005
#define TYPE_DEVICE_NAME 0x0006
#define TYPE_SEQUENCE_NUMBER 0x0007
static const value_string type_vals[] = {
{ TYPE_DEVICE_ID, "Device ID" },
{ TYPE_PORT_ID, "Port ID" },
{ TYPE_ECHO, "Echo" },
{ TYPE_MESSAGE_INTERVAL, "Message interval" },
{ TYPE_TIMEOUT_INTERVAL, "Timeout interval" },
{ TYPE_DEVICE_NAME, "Device name" },
{ TYPE_SEQUENCE_NUMBER, "Sequence number" },
{ 0, NULL }
};
#define OPCODE_RESERVED 0x00
#define OPCODE_PROBE 0x01
#define OPCODE_ECHO 0x02
#define OPCODE_FLUSH 0x03
static const value_string opcode_vals[] = {
{ OPCODE_RESERVED, "Reserved" },
{ OPCODE_PROBE, "Probe" },
{ OPCODE_ECHO, "Echo" },
{ OPCODE_FLUSH, "Flush" },
{ 0, NULL }
};
static int
dissect_udld(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_item *ti;
proto_tree *udld_tree = NULL;
int offset = 0;
uint16_t type;
uint16_t length;
proto_tree *tlv_tree;
int real_length;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "UDLD");
col_clear(pinfo->cinfo, COL_INFO);
if (tree) {
proto_item *flags_ti;
proto_tree *flags_tree;
ti = proto_tree_add_item(tree, proto_udld, tvb, offset, -1, ENC_NA);
udld_tree = proto_item_add_subtree(ti, ett_udld);
/* UDLD header */
proto_tree_add_item(udld_tree, hf_udld_version, tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(udld_tree, hf_udld_opcode, tvb, offset, 1, ENC_BIG_ENDIAN);
offset += 1;
flags_ti = proto_tree_add_item(udld_tree, hf_udld_flags, tvb, offset, 1, ENC_BIG_ENDIAN);
flags_tree = proto_item_add_subtree(flags_ti, ett_udld_flags);
proto_tree_add_item(flags_tree, hf_udld_flags_rt, tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(flags_tree, hf_udld_flags_rsy, tvb, offset, 1, ENC_BIG_ENDIAN);
offset += 1;
proto_tree_add_checksum(udld_tree, tvb, offset, hf_udld_checksum, -1, NULL, pinfo, 0, ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);
offset += 2;
} else {
offset += 4; /* The version/opcode/flags/checksum fields from above */
}
while (tvb_reported_length_remaining(tvb, offset) != 0) {
type = tvb_get_ntohs(tvb, offset + TLV_TYPE);
length = tvb_get_ntohs(tvb, offset + TLV_LENGTH);
if (length < 4) {
tlv_tree = proto_tree_add_subtree_format(udld_tree, tvb, offset, 4,
ett_udld_tlv, NULL, "TLV with invalid length %u (< 4)", length);
proto_tree_add_uint(tlv_tree, hf_udld_tlvtype, tvb,
offset + TLV_TYPE, 2, type);
ti = proto_tree_add_uint(tlv_tree, hf_udld_tlvlength, tvb,
offset + TLV_LENGTH, 2, length);
expert_add_info(pinfo, ti, &ei_udld_tlvlength);
offset += 4;
break;
}
switch (type) {
case TYPE_DEVICE_ID:
/* Device ID */
col_append_fstr(pinfo->cinfo, COL_INFO,
"Device ID: %s ",
tvb_format_stringzpad(pinfo->pool, tvb, offset + 4,
length - 4));
if (tree) {
tlv_tree = proto_tree_add_subtree_format(udld_tree, tvb, offset,
length, ett_udld_tlv, NULL, "Device ID: %s",
tvb_format_stringzpad(pinfo->pool, tvb, offset + 4, length - 4));
proto_tree_add_uint(tlv_tree, hf_udld_tlvtype, tvb,
offset + TLV_TYPE, 2, type);
proto_tree_add_uint(tlv_tree, hf_udld_tlvlength, tvb,
offset + TLV_LENGTH, 2, length);
proto_tree_add_item(tlv_tree, hf_udld_device_id, tvb, offset + 4,
length - 4, ENC_ASCII);
}
offset += length;
break;
case TYPE_PORT_ID:
real_length = length;
if (tvb_get_uint8(tvb, offset + real_length) != 0x00) {
/* The length in the TLV doesn't appear to be the
length of the TLV, as the byte just past it
isn't the first byte of a 2-byte big-endian
small integer; make the length of the TLV the length
in the TLV, plus 4 bytes for the TLV type and length,
minus 1 because that's what makes one capture work. */
real_length = length + 3;
}
col_append_fstr(pinfo->cinfo, COL_INFO,
"Port ID: %s ",
tvb_format_stringzpad(pinfo->pool, tvb, offset + 4, length - 4));
if (tree) {
tlv_tree = proto_tree_add_subtree_format(udld_tree, tvb, offset,
real_length, ett_udld_tlv, NULL, "Port ID: %s",
tvb_format_text(pinfo->pool, tvb, offset + 4, real_length - 4));
proto_tree_add_uint(tlv_tree, hf_udld_tlvtype, tvb,
offset + TLV_TYPE, 2, type);
proto_tree_add_uint(tlv_tree, hf_udld_tlvlength, tvb,
offset + TLV_LENGTH, 2, length);
proto_tree_add_item(tlv_tree, hf_udld_sent_through_interface, tvb, offset + 4,
real_length - 4, ENC_ASCII);
}
offset += real_length;
break;
case TYPE_ECHO:
case TYPE_MESSAGE_INTERVAL:
case TYPE_TIMEOUT_INTERVAL:
case TYPE_DEVICE_NAME:
case TYPE_SEQUENCE_NUMBER:
default:
tlv_tree = proto_tree_add_subtree_format(udld_tree, tvb, offset,
length, ett_udld_tlv, NULL, "Type: %s, length: %u",
val_to_str(type, type_vals, "Unknown (0x%04x)"),
length);
proto_tree_add_uint(tlv_tree, hf_udld_tlvtype, tvb,
offset + TLV_TYPE, 2, type);
proto_tree_add_uint(tlv_tree, hf_udld_tlvlength, tvb,
offset + TLV_LENGTH, 2, length);
if (length > 4) {
proto_tree_add_item(tlv_tree, hf_udld_data, tvb, offset + 4,
length - 4, ENC_NA);
} else {
return offset;
}
offset += length;
}
}
call_data_dissector(tvb_new_subset_remaining(tvb, offset), pinfo, udld_tree);
return tvb_captured_length(tvb);
}
void
proto_register_udld(void)
{
static hf_register_info hf[] = {
{ &hf_udld_version,
{ "Version", "udld.version", FT_UINT8, BASE_DEC, NULL, 0xE0,
NULL, HFILL }},
{ &hf_udld_opcode,
{ "Opcode", "udld.opcode", FT_UINT8, BASE_DEC, VALS(opcode_vals), 0x1F,
NULL, HFILL }},
{ &hf_udld_flags,
{ "Flags", "udld.flags", FT_UINT8, BASE_DEC, NULL, 0x0,
NULL, HFILL }},
{ &hf_udld_flags_rt,
{ "Recommended timeout", "udld.flags.rt", FT_UINT8, BASE_HEX, NULL, 0x01,
NULL, HFILL }},
{ &hf_udld_flags_rsy,
{ "ReSynch", "udld.flags.rsy", FT_UINT8, BASE_HEX, NULL, 0x02,
NULL, HFILL }},
{ &hf_udld_checksum,
{ "Checksum", "udld.checksum", FT_UINT16, BASE_HEX, NULL, 0x0,
NULL, HFILL }},
{ &hf_udld_tlvtype,
{ "Type", "udld.tlv.type", FT_UINT16, BASE_HEX, VALS(type_vals), 0x0,
NULL, HFILL }},
{ &hf_udld_tlvlength,
{ "Length", "udld.tlv.len", FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL }},
{ &hf_udld_device_id,
{ "Device ID", "udld.device_id", FT_STRINGZ, BASE_NONE, NULL, 0x0,
NULL, HFILL }},
{ &hf_udld_sent_through_interface,
{ "Sent through Interface", "udld.sent_through_interface", FT_STRING, BASE_NONE, NULL, 0x0,
NULL, HFILL }},
{ &hf_udld_data,
{ "Data", "udld.data", FT_BYTES, BASE_NONE, NULL, 0x0,
NULL, HFILL }},
};
static int *ett[] = {
&ett_udld,
&ett_udld_flags,
&ett_udld_tlv
};
static ei_register_info ei[] = {
{ &ei_udld_tlvlength, { "udld.tlv.len.invalid", PI_PROTOCOL, PI_WARN, "TLV with invalid length (< 4)", EXPFILL }},
};
expert_module_t* expert_udld;
proto_udld = proto_register_protocol("Unidirectional Link Detection",
"UDLD", "udld");
proto_register_field_array(proto_udld, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
expert_udld = expert_register_protocol(proto_udld);
expert_register_field_array(expert_udld, ei, array_length(ei));
udld_handle = register_dissector("udld", dissect_udld, proto_udld);
}
void
proto_reg_handoff_udld(void)
{
dissector_add_uint("llc.cisco_pid", CISCO_PID_UDLD, udld_handle);
dissector_add_uint("chdlc.protocol", 0x0111, udld_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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