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wireshark/epan/dissectors/packet-ixiatrailer.c

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/* packet-ixiatrailer.c
* Routines for Ixia trailer parsing
*
* Dissector for Ixia Network Visibility Solutions trailer
* Copyright Ixia 2012
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "config.h"
#include <epan/packet.h>
#include <wsutil/pint.h>
#include <epan/prefs.h>
#include <epan/in_cksum.h>
#include <epan/expert.h>
void proto_register_ixiatrailer(void);
void proto_reg_handoff_ixiatrailer(void);
/* Trailer "magic number". */
#define IXIA_PATTERN 0xAF12
/* Trailer TLV types.
TODO: which of these typestamp types are currently supported?
Should lose the rest!! */
#define IXIATRAILER_FTYPE_ORIGINAL_PACKET_SIZE 1
#define IXIATRAILER_FTYPE_TIMESTAMP_LOCAL 3
#define IXIATRAILER_FTYPE_TIMESTAMP_NTP 4
#define IXIATRAILER_FTYPE_TIMESTAMP_GPS 5
#define IXIATRAILER_FTYPE_TIMESTAMP_1588 6 /* PTP */
#define IXIATRAILER_FTYPE_TIMESTAMP_HOLDOVER 7
static const value_string ixiatrailer_ftype_timestamp[] = {
{ IXIATRAILER_FTYPE_TIMESTAMP_LOCAL, "Local" },
{ IXIATRAILER_FTYPE_TIMESTAMP_NTP, "NTP" },
{ IXIATRAILER_FTYPE_TIMESTAMP_GPS, "GPS" },
{ IXIATRAILER_FTYPE_TIMESTAMP_1588, "PTP" },
{ IXIATRAILER_FTYPE_TIMESTAMP_HOLDOVER, "Holdover" },
{ 0, NULL }
};
/* Preference settings */
static gboolean ixiatrailer_summary_in_tree = TRUE;
static int proto_ixiatrailer = -1;
static gint ett_ixiatrailer = -1;
static int hf_ixiatrailer_packetlen = -1;
static int hf_ixiatrailer_timestamp = -1;
static int hf_ixiatrailer_generic = -1;
static expert_field ei_ixiatrailer_field_length_invalid = EI_INIT;
/* The trailer begins with a sequence of TLVs, each of which has a
1-byte type, a 1-byte value length (not TLV length, so the TLV
length is the value length + 2), and a variable-length value.
Following the sequence of TLVs is:
a 1-byte field giving the length of the sequence of TLVs;
a 2-byte big-endian signature field with the value 0xAF12;
a 2-byte big-endian checksum field, covering the sequence
of TLVs, the sequence length, and the signature.
*/
static int
dissect_ixiatrailer(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void *data _U_)
{
proto_tree *ti;
guint tvblen, trailer_length, field_length;
gboolean matched_without_fcs, matched_with_fcs;
proto_tree *ixiatrailer_tree = NULL;
guint offset = 0;
guint16 cksum, comp_cksum;
vec_t vec;
guint8 field_type;
/* A trailer must, at minimum, include:
a "original packet size" TLV, with 1 byte of type, 1 byte of
value length, and 2 bytes of original packet ize;
1 byte of trailer length;
2 bytes of signature;
2 bytes of trailer checksum;
for a total of 9 bytes. */
tvblen = tvb_reported_length(tvb);
if (tvblen != tvb_captured_length(tvb)) {
/* The heuristic check includes a checksum check, so we need the
*entire* trailer to have been captured; if it wasn't, we don't
try to check it. */
return 0;
}
if (tvblen < 9) {
/* This is too short, so it cannot be a valid Ixia trailer. */
return 0;
}
/* Depending upon the ethernet preference "Assume packets have FCS", we
may be given those 4 bytes too.
Try checking two locations for our pattern. */
if (tvblen == 23) {
tvblen = 19;
}
/* 3rd & 4th bytes from the end must match our pattern.
First, try under the assumption that the tvbuff doesn't include
the FCS. */
matched_without_fcs = (tvb_get_ntohs(tvb, tvblen-4) == IXIA_PATTERN);
/* If that didn't match, is the tvbuff big enough to include an Ixia
trailer *and* an FCS? If so, try under that assumption. */
if (!matched_without_fcs && tvblen >= 13)
matched_with_fcs = (tvb_get_ntohs(tvb, tvblen-(4+4)) == IXIA_PATTERN);
else
matched_with_fcs = FALSE;
if (!matched_without_fcs) {
if (!matched_with_fcs) {
/* Neither matched, so no Ixia trailer. */
return 0;
}
/* Matched under the assumption that we have an FCS, so let's
act as if that's the case. Remove the FCS length from the
tvbuff. */
tvblen -= 4;
}
/* Read Trailer-length field */
trailer_length = tvb_get_guint8(tvb, tvblen-5);
/* Should match overall length of trailer */
if ((tvblen-5) != trailer_length) {
return 0;
}
/* Last 2 bytes are the checksum */
cksum = tvb_get_ntohs(tvb, tvblen-2);
/* Verify the checksum; if not valid, it means that the trailer is not valid */
SET_CKSUM_VEC_TVB(vec, tvb, offset, trailer_length + 3);
comp_cksum = in_cksum(&vec, 1);
if (pntoh16(&comp_cksum) != cksum) {
return 0;
}
/* OK: We have our trailer - create protocol root */
ti = proto_tree_add_item(tree, proto_ixiatrailer, tvb, offset, trailer_length + 5, ENC_NA);
/* Append summary to item, if configured to */
if (ixiatrailer_summary_in_tree) {
proto_item_append_text(ti, ", Length: %u, Checksum: 0x%x", trailer_length, cksum);
}
/* Create subtree */
ixiatrailer_tree = proto_item_add_subtree(ti, ett_ixiatrailer);
while (offset < trailer_length - 2)
{
field_type = tvb_get_guint8(tvb, offset++);
field_length = tvb_get_guint8(tvb, offset++);
switch (field_type) {
case IXIATRAILER_FTYPE_ORIGINAL_PACKET_SIZE:
if (field_length != 2){
expert_add_info_format(pinfo, ti, &ei_ixiatrailer_field_length_invalid, "Field length %u invalid", field_length);
break;
}
ti = proto_tree_add_item(ixiatrailer_tree, hf_ixiatrailer_packetlen, tvb, offset, field_length, ENC_BIG_ENDIAN);
proto_item_append_text(ti, " bytes");
break;
case IXIATRAILER_FTYPE_TIMESTAMP_LOCAL:
case IXIATRAILER_FTYPE_TIMESTAMP_NTP:
case IXIATRAILER_FTYPE_TIMESTAMP_GPS:
case IXIATRAILER_FTYPE_TIMESTAMP_1588:
case IXIATRAILER_FTYPE_TIMESTAMP_HOLDOVER:
if (field_length != 8) {
expert_add_info_format(pinfo, ti, &ei_ixiatrailer_field_length_invalid, "Field length %u invalid", field_length);
break;
}
/* Timestamp */
ti = proto_tree_add_item(ixiatrailer_tree, hf_ixiatrailer_timestamp, tvb, offset, field_length, ENC_TIME_TIMESPEC|ENC_BIG_ENDIAN);
proto_item_append_text(ti, "; Source: %s", val_to_str_const(field_type, ixiatrailer_ftype_timestamp, "Unknown"));
break;
default:
/* Not a recognized time format - just show as bytes */
ti = proto_tree_add_item(ixiatrailer_tree, hf_ixiatrailer_generic, tvb, offset, field_length, ENC_NA);
proto_item_append_text(ti, " [Id: %u, Length: %u bytes]", field_type, field_length);
break;
};
offset += field_length;
}
/* We are claiming all of the bytes */
return tvblen;
}
void
proto_register_ixiatrailer(void)
{
static hf_register_info hf[] = {
{ &hf_ixiatrailer_packetlen, {
"Original packet length", "ixiatrailer.packetlen", FT_UINT16, BASE_DEC,
NULL, 0x0, NULL, HFILL }},
{ &hf_ixiatrailer_timestamp, {
"Time Stamp", "ixiatrailer.timestamp", FT_ABSOLUTE_TIME, ABSOLUTE_TIME_LOCAL,
NULL, 0x0, NULL, HFILL }},
{ &hf_ixiatrailer_generic, {
"Generic Field", "ixiatrailer.generic", FT_BYTES, BASE_NONE,
NULL, 0x0, NULL, HFILL }},
};
static gint *ixiatrailer_ett[] = {
&ett_ixiatrailer
};
static ei_register_info ei[] = {
{ &ei_ixiatrailer_field_length_invalid, { "ixiatrailer.field_length_invalid", PI_MALFORMED, PI_ERROR, "Field length invalid", EXPFILL }},
};
module_t *ixiatrailer_module;
expert_module_t* expert_ixiatrailer;
proto_ixiatrailer = proto_register_protocol("Ixia Trailer", "IXIATRAILER", "ixiatrailer");
proto_register_field_array(proto_ixiatrailer, hf, array_length(hf));
proto_register_subtree_array(ixiatrailer_ett, array_length(ixiatrailer_ett));
expert_ixiatrailer = expert_register_protocol(proto_ixiatrailer);
expert_register_field_array(expert_ixiatrailer, ei, array_length(ei));
ixiatrailer_module = prefs_register_protocol(proto_ixiatrailer, NULL);
prefs_register_bool_preference(ixiatrailer_module, "summary_in_tree",
"Show trailer summary in protocol tree",
"Whether the trailer summary line should be shown in the protocol tree",
&ixiatrailer_summary_in_tree);
}
void
proto_reg_handoff_ixiatrailer(void)
{
/* Check for Ixia format in the ethernet trailer */
heur_dissector_add("eth.trailer", dissect_ixiatrailer, "Ixia Trailer", "ixiatrailer_eth", proto_ixiatrailer, HEURISTIC_ENABLE);
}
/*
* Editor modelines - http://www.wireshark.org/tools/modelines.html
*
* Local Variables:
* c-basic-offset: 2
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* ex: set shiftwidth=2 tabstop=8 expandtab:
* :indentSize=2:tabSize=8:noTabs=true:
*/
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