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wireshark/epan/dissectors/packet-brdwlk.c
Jaap Keuter 3f0fc1b232 FC: use ETHERTYPE_UNK when applicable, no excuses 
Two interlocking problems cause the dissection of FC to fail in some cases,
as shown in the capture of the related issue.

The FC dissector assumes that ETHERTYPE_UNK in the data structure passed
to it is coming from the MDS header dissector only, and thus that header
sizes have to be taken into account. This is not / no longer the case.
It always passes down ETHERTYPE_FCFT. Therefore the MDS header size
checking does not apply to ETHERTYP_UNK, so is removed as condition.

The other FC related dissectors were forced to setup a data structure to
pass to FC for it to handle that part of the frame. Because these weren't
related to ethernet, these lazily set the ethertype field in the data
structure to 0. This unfortunately matches ETHERTYPE_UNK, triggering the
MDS header size checking in FC, leading to this issue. With the first
problem resolved, now make it explicit that unknown ethertype is indicated
by ETHERTYPE_UNK, not '0'.

Addresses primary part of issue #17084
2020-12-15 20:26:29 +00:00

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/* packet-brdwlk.c
* Routines for decoding MDS Port Analyzer Adapter (FC in Eth) Header
* Copyright 2001, Dinesh G Dutt <ddutt@andiamo.com>
*
* 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/proto_data.h>
#include "packet-fc.h"
#define BRDWLK_MAX_PACKET_CNT 0xFFFF
#define BRDWLK_TRUNCATED_BIT 0x8
#define BRDWLK_HAS_PLEN 0x1
#define FCM_DELIM_SOFC1 0x01
#define FCM_DELIM_SOFI1 0x02
#define FCM_DELIM_SOFI2 0x04
#define FCM_DELIM_SOFI3 0x06
#define FCM_DELIM_SOFN1 0x03
#define FCM_DELIM_SOFN2 0x05
#define FCM_DELIM_SOFN3 0x07
#define FCM_DELIM_SOFF 0x08
#define FCM_DELIM_SOFC4 0x09
#define FCM_DELIM_SOFI4 0x0A
#define FCM_DELIM_SOFN4 0x0B
#define FCM_DELIM_EOFT 0x01
#define FCM_DELIM_EOFDT 0x02
#define FCM_DELIM_EOFN 0x03
#define FCM_DELIM_EOFA 0x04
#define FCM_DELIM_EOFNI 0x07
#define FCM_DELIM_EOFDTI 0x06
#define FCM_DELIM_EOFRT 0x0A
#define FCM_DELIM_EOFRTI 0x0E
#define FCM_DELIM_NOEOF 0xF0
#define FCM_DELIM_EOFJUMBO 0xF1
void proto_register_brdwlk(void);
void proto_reg_handoff_brdwlk(void);
static const value_string brdwlk_sof_vals[] = {
{FCM_DELIM_SOFI1, "SOFi1"},
{FCM_DELIM_SOFI2, "SOFi2"},
{FCM_DELIM_SOFI3, "SOFi3"},
{FCM_DELIM_SOFN1, "SOFn1"},
{FCM_DELIM_SOFN2, "SOFn2"},
{FCM_DELIM_SOFN3, "SOFn3"},
{FCM_DELIM_SOFF, "SOFf"},
{0, NULL},
};
static const value_string brdwlk_eof_vals[] = {
{FCM_DELIM_EOFDT, "EOFdt"},
{FCM_DELIM_EOFA, "EOFa"},
{FCM_DELIM_EOFN, "EOFn"},
{FCM_DELIM_EOFT, "EOFt"},
{0, NULL},
};
static int hf_brdwlk_sof = -1;
static int hf_brdwlk_eof = -1;
static int hf_brdwlk_error = -1;
static int hf_brdwlk_vsan = -1;
static int hf_brdwlk_pktcnt = -1;
static int hf_brdwlk_drop = -1;
static int hf_brdwlk_plen = -1;
static int hf_brdwlk_error_plp = -1;
static int hf_brdwlk_error_ef = -1;
static int hf_brdwlk_error_nd = -1;
static int hf_brdwlk_error_tr = -1;
static int hf_brdwlk_error_badcrc = -1;
static int hf_brdwlk_error_ff = -1;
static int hf_brdwlk_error_jumbo = -1;
static int hf_brdwlk_error_ctrl = -1;
/* Initialize the subtree pointers */
static gint ett_brdwlk = -1;
static gint ett_brdwlk_error = -1;
static gint proto_brdwlk = -1;
static guint16 packet_count = 0;
static gboolean first_pkt = TRUE; /* start of capture */
static dissector_handle_t fc_dissector_handle;
static const true_false_string tfs_error_plp = {
"Packet Length is PRESENT",
"Packet length is NOT present"
};
static const true_false_string tfs_error_ef = {
"This is an Empty Frame",
"Frame is NOT empty"
};
static const true_false_string tfs_error_nd = {
"This Frame has NO Data",
"This frame carries data"
};
static const true_false_string tfs_error_tr = {
"This frame is TRUNCATED",
"This frame is NOT truncated"
};
static const true_false_string tfs_error_crc = {
"This Frame has a BAD FC CRC",
"This frame has a valid crc"
};
static const true_false_string tfs_error_ff = {
"Fifo is Full",
"Fifo is NOT full"
};
static const true_false_string tfs_error_jumbo = {
"This is a JUMBO FC Frame",
"This is a NORMAL FC Frame"
};
static const true_false_string tfs_error_ctrl = {
"Ctrl Characters inside the frame",
"No ctrl chars inside the frame"
};
static void
dissect_brdwlk_err(proto_tree *parent_tree, tvbuff_t *tvb, int offset)
{
static int * const flags[] = {
&hf_brdwlk_error_plp,
&hf_brdwlk_error_ef,
&hf_brdwlk_error_nd,
&hf_brdwlk_error_tr,
&hf_brdwlk_error_badcrc,
&hf_brdwlk_error_ff,
&hf_brdwlk_error_jumbo,
&hf_brdwlk_error_ctrl,
NULL
};
proto_tree_add_bitmask_with_flags(parent_tree, tvb, offset, hf_brdwlk_error, ett_brdwlk_error, flags, ENC_NA, BMT_NO_FALSE|BMT_NO_TFS);
}
/* Code to actually dissect the packets */
static int
dissect_brdwlk(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, *hidden_item;
proto_tree *brdwlk_tree;
tvbuff_t *next_tvb;
guint8 error, eof, sof;
int hdrlen = 2,
offset = 0;
gint len, reported_len, plen;
guint16 pkt_cnt;
gboolean dropped_packets;
fc_data_t fc_data;
/* Make entries in Protocol column and Info column on summary display */
col_set_str(pinfo->cinfo, COL_PROTOCOL, "Boardwalk");
col_clear(pinfo->cinfo, COL_INFO);
sof = (tvb_get_guint8(tvb, offset) & 0xF0) >> 4;
fc_data.sof_eof = 0;
if ((sof == FCM_DELIM_SOFI3) || (sof == FCM_DELIM_SOFI2) || (sof == FCM_DELIM_SOFI1)
|| (sof == FCM_DELIM_SOFI4)) {
fc_data.sof_eof = FC_DATA_SOF_FIRST_FRAME;
}
else if (sof == FCM_DELIM_SOFF) {
fc_data.sof_eof = FC_DATA_SOF_SOFF;
}
ti = proto_tree_add_protocol_format(tree, proto_brdwlk, tvb, 0,
hdrlen, "Boardwalk");
brdwlk_tree = proto_item_add_subtree(ti, ett_brdwlk);
proto_tree_add_item(brdwlk_tree, hf_brdwlk_sof, tvb, offset, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(brdwlk_tree, hf_brdwlk_vsan, tvb, offset, 2, ENC_BIG_ENDIAN);
/* Locate EOF which is the last 4 bytes of the frame */
len = tvb_captured_length_remaining(tvb, hdrlen);
reported_len = tvb_reported_length_remaining(tvb, hdrlen);
if (reported_len < 4) {
/*
* This packet is claimed not to even have enough data for
* a 4-byte EOF.
* Don't try to process the EOF.
*/
;
}
else if (len < reported_len) {
/*
* This packet is claimed to have enough data for a 4-byte EOF,
* but we didn't capture all of the packet.
* Slice off the 4-byte EOF from the reported length, and trim
* the captured length so it's no more than the reported length;
* that will slice off what of the EOF, if any, is in the
* captured length.
*/
reported_len -= 4;
if (len > reported_len)
len = reported_len;
}
else {
/*
* We have the entire packet, and it includes a 4-byte EOF.
* Slice it off, and put it into the tree if we're building
* a tree.
*/
len -= 4;
reported_len -= 4;
offset = tvb_reported_length(tvb) - 4;
pkt_cnt = tvb_get_ntohs(tvb, offset);
if (tree) {
proto_tree_add_uint(brdwlk_tree, hf_brdwlk_pktcnt, tvb, offset,
2, pkt_cnt);
}
dropped_packets = FALSE;
if (pinfo->fd->visited) {
/*
* This isn't the first pass, so we can't use the global
* "packet_count" variable to determine whether there were
* any dropped frames or not.
* We therefore attach a non-null pointer as frame data to
* any frame preceded by dropped packets.
*/
if (p_get_proto_data(wmem_file_scope(), pinfo, proto_brdwlk, 0) != NULL)
dropped_packets = TRUE;
} else {
/*
* This is the first pass, so we have to use the global
* "packet_count" variable to determine whether there were
* any dropped frames or not.
*
* XXX - can there be more than one stream of packets, so that
* we can't just use a global variable?
*/
if (pkt_cnt != packet_count + 1) {
if (!first_pkt &&
(pkt_cnt != 0 || (packet_count != BRDWLK_MAX_PACKET_CNT))) {
dropped_packets = TRUE;
/*
* Mark this frame as having been preceded by dropped
* packets. (The data we use as the frame data doesn't
* matter - it just matters that it's non-null.)
*/
p_add_proto_data(wmem_file_scope(), pinfo, proto_brdwlk, 0, &packet_count);
}
}
}
hidden_item = proto_tree_add_boolean(brdwlk_tree, hf_brdwlk_drop,
tvb, offset, 0, dropped_packets);
proto_item_set_hidden(hidden_item);
packet_count = pkt_cnt;
error=tvb_get_guint8(tvb, offset+2);
dissect_brdwlk_err(brdwlk_tree, tvb, offset+2);
eof = tvb_get_guint8(tvb, offset+3);
if (eof != FCM_DELIM_EOFN) {
fc_data.sof_eof |= FC_DATA_EOF_LAST_FRAME;
}
else if (eof != FCM_DELIM_EOFT) {
fc_data.sof_eof |= FC_DATA_EOF_INVALID;
}
proto_tree_add_item(brdwlk_tree, hf_brdwlk_eof, tvb, offset+3,
1, ENC_BIG_ENDIAN);
if ((error & BRDWLK_HAS_PLEN) && tree) {
/* In newer Boardwalks, if this bit is set, the actual frame length
* is also provided. This length is the size between SOF & EOF
* including FC CRC.
*/
plen = tvb_get_ntohl(tvb, offset-4);
plen *= 4;
proto_tree_add_uint(brdwlk_tree, hf_brdwlk_plen, tvb, offset-4,
4, plen);
#if 0
/* XXX - this would throw an exception if it would increase
* the reported length.
*/
if (error & BRDWLK_TRUNCATED_BIT) {
tvb_set_reported_length(tvb, plen);
}
#endif
}
}
fc_data.ethertype = ETHERTYPE_BRDWALK;
next_tvb = tvb_new_subset_length_caplen(tvb, 2, len, reported_len);
call_dissector_with_data(fc_dissector_handle, next_tvb, pinfo, tree, &fc_data);
return tvb_captured_length(tvb);
}
static void
brdwlk_init(void)
{
packet_count = 0;
first_pkt = TRUE;
}
/* Register the protocol with Wireshark */
/* this format is require because a script is used to build the C function
that calls all the protocol registration.
*/
void
proto_register_brdwlk(void)
{
/* Setup list of header fields See Section 1.6.1 for details*/
static hf_register_info hf[] = {
{ &hf_brdwlk_sof,
{"SOF", "brdwlk.sof", FT_UINT8, BASE_HEX, VALS(brdwlk_sof_vals),
0xF0, NULL, HFILL}},
{ &hf_brdwlk_eof,
{"EOF", "brdwlk.eof", FT_UINT8, BASE_HEX, VALS(brdwlk_eof_vals),
0x0F, NULL, HFILL}},
{ &hf_brdwlk_error,
{"Error", "brdwlk.error", FT_UINT8, BASE_HEX, NULL, 0x0, NULL,
HFILL}},
{ &hf_brdwlk_pktcnt,
{"Packet Count", "brdwlk.pktcnt", FT_UINT16, BASE_DEC, NULL, 0x0,
NULL, HFILL}},
{ &hf_brdwlk_drop,
{"Packet Dropped", "brdwlk.drop", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
NULL, HFILL}},
{ &hf_brdwlk_vsan,
{"VSAN", "brdwlk.vsan", FT_UINT16, BASE_DEC, NULL, 0xFFF, NULL,
HFILL}},
{ &hf_brdwlk_plen,
{"Original Packet Length", "brdwlk.plen", FT_UINT32, BASE_DEC, NULL, 0x0, NULL,
HFILL}},
{ &hf_brdwlk_error_plp,
{"Packet Length Present", "brdwlk.error.plp", FT_BOOLEAN, 8, TFS(&tfs_error_plp), 0x01, NULL,
HFILL}},
{ &hf_brdwlk_error_ef,
{"Empty Frame", "brdwlk.error.ef", FT_BOOLEAN, 8, TFS(&tfs_error_ef), 0x02, NULL,
HFILL}},
{ &hf_brdwlk_error_nd,
{"No Data", "brdwlk.error.nd", FT_BOOLEAN, 8, TFS(&tfs_error_nd), 0x04, NULL,
HFILL}},
{ &hf_brdwlk_error_tr,
{"Truncated", "brdwlk.error.tr", FT_BOOLEAN, 8, TFS(&tfs_error_tr), 0x08, NULL,
HFILL}},
{ &hf_brdwlk_error_badcrc,
{"CRC", "brdwlk.error.crc", FT_BOOLEAN, 8, TFS(&tfs_error_crc), 0x10, NULL,
HFILL}},
{ &hf_brdwlk_error_ff,
{"Fifo Full", "brdwlk.error.ff", FT_BOOLEAN, 8, TFS(&tfs_error_ff), 0x20, NULL,
HFILL}},
{ &hf_brdwlk_error_jumbo,
{"Jumbo FC Frame", "brdwlk.error.jumbo", FT_BOOLEAN, 8, TFS(&tfs_error_jumbo), 0x40, NULL,
HFILL}},
{ &hf_brdwlk_error_ctrl,
{"Ctrl Char Inside Frame", "brdwlk.error.ctrl", FT_BOOLEAN, 8, TFS(&tfs_error_ctrl), 0x80, NULL,
HFILL}},
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_brdwlk,
&ett_brdwlk_error,
};
/* Register the protocol name and description */
proto_brdwlk = proto_register_protocol("Boardwalk",
"Boardwalk", "brdwlk");
/* Required function calls to register the header fields and subtrees used */
proto_register_field_array(proto_brdwlk, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
register_init_routine(&brdwlk_init);
}
void
proto_reg_handoff_brdwlk(void)
{
dissector_handle_t brdwlk_handle;
brdwlk_handle = create_dissector_handle(dissect_brdwlk, proto_brdwlk);
dissector_add_uint("ethertype", ETHERTYPE_BRDWALK, brdwlk_handle);
dissector_add_uint("ethertype", 0xABCD, brdwlk_handle);
fc_dissector_handle = find_dissector_add_dependency("fc", proto_brdwlk);
}
/*
* 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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