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/* packet-gsm_l2rcop.c
* Routines for GSM L2RCOP (3GPP TS 27.002) dissection
* (C) 2023 Harald Welte <laforge@osmocom.org>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/prefs.h>
#include <epan/xdlc.h>
#include <epan/reassemble.h>
#include <epan/conversation.h>
void proto_register_gsm_l2rcop(void);
static int proto_l2rcop = -1;
static int hf_l2rcop_sa = -1;
static int hf_l2rcop_sb = -1;
static int hf_l2rcop_x = -1;
static int hf_l2rcop_addr = -1;
static int hf_l2rcop_break = -1;
static int hf_l2rcop_break_ack = -1;
static int ett_l2rcop = -1;
static const value_string addr_vals[] = {
{ 31, "last status change, remainder empty" },
{ 30, "last status change, remainder full of characters" },
{ 29, "destructive break signal, remainder empty" },
{ 28, "destructive break acknowledge, remainder empty" },
{ 27, "extended address in ext octet" },
{ 0, NULL }
};
static void
add_characters(proto_tree *tree, packet_info *pinfo, tvbuff_t *tvb, guint offset, guint len)
{
tvbuff_t *next_tvb = tvb_new_subset_length(tvb, offset, len);
call_data_dissector(next_tvb, pinfo, tree);
}
/* Dissect a L2RCOP message as described in 3GPP TS 27.002 */
static int
dissect_l2rcop(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
int reported_len = tvb_reported_length(tvb);
guint cur;
/* we currently support RLP v0 + v1 (first octet is always status octet) */
for (cur = 0; cur < (guint)reported_len; ) {
guint8 oct = tvb_get_guint8(tvb, cur);
guint8 addr = oct & 0x1f;
proto_tree *l2rcop_tree;
proto_item *ti;
const gchar *addr_str = val_to_str(addr, addr_vals, "%u characters");
ti = proto_tree_add_protocol_format(tree, proto_l2rcop, tvb, 0, reported_len,
"GSM L2RCOP Chunk Status=0x%02x (Addr: %s)", oct, addr_str);
l2rcop_tree = proto_item_add_subtree(ti, ett_l2rcop);
proto_tree_add_item(l2rcop_tree, hf_l2rcop_sa, tvb, cur, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(l2rcop_tree, hf_l2rcop_sb, tvb, cur, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(l2rcop_tree, hf_l2rcop_x, tvb, cur, 1, ENC_BIG_ENDIAN);
proto_tree_add_item(l2rcop_tree, hf_l2rcop_addr, tvb, cur, 1, ENC_BIG_ENDIAN);
switch (addr) {
case 31: /* last status change, remainder empty */
return reported_len;
case 30: /* last status change, remainder full of characters */
add_characters(l2rcop_tree, pinfo, tvb, cur+1, reported_len-cur-1);
return reported_len;
case 29: /* destructive break signal, remainder empty */
proto_tree_add_item(l2rcop_tree, hf_l2rcop_break, tvb, cur, 1, ENC_BIG_ENDIAN);
return reported_len;
case 28: /* destructive break acknowledge, remainder empty */
proto_tree_add_item(l2rcop_tree, hf_l2rcop_break_ack, tvb, cur, 1, ENC_BIG_ENDIAN);
return reported_len;
case 27: /* extended address in ext octet */
cur++;
addr = tvb_get_guint8(tvb, cur) & 0x3f;
/* This "cannot happen"; let's abort processing right now. */
if (addr == 0)
return reported_len;
proto_tree_add_uint(l2rcop_tree, hf_l2rcop_addr, tvb, cur, 1, addr);
add_characters(l2rcop_tree, pinfo, tvb, cur+1, addr);
cur += 1 + addr;
break;
case 0:
/* This "cannot happen"; let's abort processing right now. */
return reported_len;
default:
/* This "cannot happen"; let's abort processing right now. */
if (addr == 0)
return reported_len;
add_characters(l2rcop_tree, pinfo, tvb, cur+1, addr);
cur += 1 + addr;
break;
}
}
return reported_len;
}
static const true_false_string x_vals = {
"flow control ACTIVE", "flow control inactive"
};
static const true_false_string sab_vals = {
"OFF", "ON"
};
void
proto_register_gsm_l2rcop(void)
{
static hf_register_info hf[] = {
{ &hf_l2rcop_sa,
{ "SA", "gsm_l2rcop.sa", FT_BOOLEAN, 8, TFS(&sab_vals), 0x80,
NULL, HFILL }},
{ &hf_l2rcop_sb,
{ "SB", "gsm_l2rcop.sb", FT_BOOLEAN, 8, TFS(&sab_vals), 0x40,
NULL, HFILL }},
{ &hf_l2rcop_x,
{ "X", "gsm_l2rcop.x", FT_BOOLEAN, 8, TFS(&x_vals), 0x20,
NULL, HFILL }},
{ &hf_l2rcop_addr,
{ "Address", "gsm_l2rcop.addr", FT_UINT8, BASE_DEC|BASE_SPECIAL_VALS, VALS(addr_vals), 0x1f,
NULL, HFILL }},
{ &hf_l2rcop_break,
{ "Break", "gsm_l2rcop.break", FT_UINT8, BASE_DEC, NULL, 0x00,
NULL, HFILL }},
{ &hf_l2rcop_break_ack,
{ "Break Ack", "gsm_l2rcop.break_ack", FT_UINT8, BASE_DEC, NULL, 0x00,
NULL, HFILL }},
};
static gint *ett[] = {
&ett_l2rcop,
};
proto_l2rcop = proto_register_protocol("GSM L2R Character Oriented Protocol (L2RCOP)", "GSM-L2RCOP",
"gsm_l2rcop");
proto_register_field_array(proto_l2rcop, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
register_dissector("gsm_l2rcop", dissect_l2rcop, proto_l2rcop);
}
/*
* 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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