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wireshark/epan/dissectors/packet-cl3.c
Tomasz Moń 7b82110092 USB HID: Parse bit fields with correct bit order 
Implement little endian support for tvb_get_bits family of functions.
The big/little endian refers to bit numbering within an octet. In big
endian, the most significant bit is considered bit 0, while in little
endian the least significant bit is considered bit 0.

Add encoding parameters to proto tree bits format family functions.
Specify ENC_BIG_ENDIAN in all dissectors using these functions except in
USB HID that requires ENC_LITTLE_ENDIAN to work correctly.

When formatting bits values, always display most significant bit on the
leftmost position regardless of the encoding. This results in no gaps
between octets and makes the displayed value comprehensible.

Close #4478
Fix #17014
2021-09-26 18:16:28 +02:00

216 lines
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/* packet-cl3.c
* Routines for CableLabs Layer-3 Protocol Dissection
* Copyright 2019 Jon Dennis <j.dennis[at]cablelabs.com>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*
* Dissector for IEEE-Registered CableLabs EtherType 0xB4E3
*
* IEEE EtherType List
* http://standards-oui.ieee.org/ethertype/eth.txt
*
* CableLabs Specifications Can Be Found At:
* https://www.cablelabs.com/specs
* Note: As of writing this, the spec is in the process of being published.
* Initially, this will be published under the Dual Channel Wi-Fi spec,
* but may split off into its own spec in the future.
* Eventually a direct link to the spec should be put here.
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/expert.h>
#include <epan/etypes.h>
#include <wsutil/str_util.h>
void proto_register_cl3(void);
void proto_reg_handoff_cl3(void);
/* persistent handles for this dissector */
static int proto_cl3 = -1;
static dissector_table_t cl3_command_table;
static gint ett_cl3 = -1;
static int hf_cl3_version = -1;
static int hf_cl3_headerlen = -1;
static int hf_cl3_subproto = -1;
static int hf_cl3_payload = -1;
static expert_field ei_cl3_badheaderlen = EI_INIT;
static expert_field ei_cl3_unsup_ver = EI_INIT;
/* Known CL3 (sub-)protocol type strings: */
static const value_string cl3_protocols[] = {
{0x00DC, "Dual-Channel Wi-Fi Messaging" },
{0, NULL}
};
/* called for each incomming framing matching the CL3 ethertype with a version number of 1: */
static void
dissect_cl3_v1(
tvbuff_t *tvb,
packet_info *pinfo,
proto_tree *tree,
proto_item *ti,
proto_tree *cl3_tree,
guint16 header_length
) {
dissector_handle_t dh;
tvbuff_t *tvb_sub;
guint16 subprotocol_id;
/* ensure the header length is valid for version 1 */
if (header_length != 4) {
expert_add_info(pinfo, ti, &ei_cl3_badheaderlen);
}
/* parse the sub-protocol id */
subprotocol_id = tvb_get_ntohs(tvb, 2);
/* append the subprotocol id to the "packet summary view" fields */
col_append_sep_fstr(pinfo->cinfo, COL_INFO, " ", "[Subprotocol 0x%04X]", (guint)subprotocol_id);
/* add elements to the CL3 tree...
CL3 version 1 fields: (pretty much just the sub protocol id) */
proto_tree_add_uint(cl3_tree, hf_cl3_subproto, tvb, 2, 2, subprotocol_id);
/* call CL (sub-)protocol dissector */
dh = dissector_get_uint_handle(cl3_command_table, subprotocol_id);
if (dh != NULL) {
tvb_sub = tvb_new_subset_remaining(tvb, header_length);
call_dissector(dh, tvb_sub, pinfo, tree);
}
}
/* called for each incomming framing matching the CL3 ethertype: */
static int
dissect_cl3(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) {
proto_item *ti;
proto_tree *cl3_tree;
guint16 version;
guint16 header_length;
guint32 payload_length;
/* parse the header fields */
version = header_length = tvb_get_ntohs(tvb, 0);
version >>= 12;
header_length >>= 8;
header_length &= 0x0F;
header_length *= 4;
payload_length = tvb_captured_length(tvb) - header_length;
/* setup the "packet summary view" fields */
col_set_str(pinfo->cinfo, COL_PROTOCOL, "CL3");
col_clear(pinfo->cinfo, COL_INFO);
col_add_fstr(pinfo->cinfo, COL_INFO, "CableLabs Layer-3 Protocol (Ver %u)", (guint)version);
/* create a tree node for us... */
ti = proto_tree_add_protocol_format(tree, proto_cl3, tvb, 0, header_length, "CableLabs Layer-3 Protocol (CL3) Version %u", (guint)version);
cl3_tree = proto_item_add_subtree(ti, ett_cl3);
/* CL3 version agnostic fields: (pretty much just the first byte; like ipv4, version + length) */
proto_tree_add_item(cl3_tree, hf_cl3_version, tvb, 0, 1, ENC_NA);
proto_tree_add_uint_bits_format_value(cl3_tree, hf_cl3_headerlen, tvb, 0 + 4, 4, header_length,
ENC_BIG_ENDIAN, "%u bytes (%u)", header_length, header_length >> 2);
/* validate the header length... */
if ((header_length < 1) || (header_length > tvb_captured_length(tvb))) {
expert_add_info(pinfo, ti, &ei_cl3_badheaderlen);
}
/* version-specific disscection... */
switch (version) {
case 1:
dissect_cl3_v1(tvb, pinfo, tree, ti, cl3_tree, header_length);
break;
default:
expert_add_info(pinfo, ti, &ei_cl3_unsup_ver);
break;
}
/* add a byte reference to the payload we are carrying */
proto_tree_add_item(cl3_tree, hf_cl3_payload, tvb, header_length, payload_length, ENC_NA);
return tvb_captured_length(tvb);
}
/* initializes this dissector */
void
proto_register_cl3(void) {
static hf_register_info hf[] = {
{ &hf_cl3_version,
{ "Version", "cl3.version",
FT_UINT8, BASE_DEC, NULL, 0xF0,
"The CableLabs layer-3 protocol version number", HFILL }},
{ &hf_cl3_headerlen,
{ "Header Length", "cl3.headerlen",
FT_UINT8, BASE_DEC, NULL, 0x0,
"The length of the CableLabs layer-3 protocol header", HFILL }},
{ &hf_cl3_subproto,
{ "Subprotocol", "cl3.subprotocol",
FT_UINT16, BASE_HEX, VALS(cl3_protocols), 0x0,
"The subprotocol number the CableLabs layer-3 protocol is carrying", HFILL }},
{ &hf_cl3_payload,
{ "CL3 Payload", "cl3.payload",
FT_BYTES, BASE_NONE, NULL, 0x0,
"The payload carried by this CableLabs layer-3 protocol packet", HFILL}},
};
static gint *ett[] = {
&ett_cl3,
};
static ei_register_info ei[] = {
{ &ei_cl3_badheaderlen, { "cl3.badheaderlen", PI_MALFORMED, PI_ERROR, "Bad Header Length", EXPFILL }},
{ &ei_cl3_unsup_ver, { "cl3.unsup_ver", PI_UNDECODED, PI_WARN, "Unknown protocol version", EXPFILL }},
};
expert_module_t* expert_cl3;
proto_cl3 = proto_register_protocol(
"CableLabs Layer 3 Protocol", /* name */
"CL3", /* short name */
"cl3" /* abbrev */
);
proto_register_field_array(proto_cl3, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
expert_cl3 = expert_register_protocol(proto_cl3);
expert_register_field_array(expert_cl3, ei, array_length(ei));
/* subdissector code... */
cl3_command_table = register_dissector_table("cl3.subprotocol", "CableLabs Subprotocol", proto_cl3, FT_UINT16, BASE_DEC);
}
/* hooks in our dissector to be called on matching ethertype */
void
proto_reg_handoff_cl3(void) {
dissector_handle_t cl3_handle;
cl3_handle = create_dissector_handle(&dissect_cl3, proto_cl3);
dissector_add_uint("ethertype", ETHERTYPE_CABLELABS, cl3_handle);
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 2
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=2 tabstop=8 expandtab:
* :indentSize=2:tabSize=8:noTabs=true:
*/
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