nexmon – Rev 1
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/* packet-lapdm.c
* Routines for LAPDm frame disassembly
* Duncan Salerno <duncan.salerno@googlemail.com>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998
*
* 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.
*/
/* LAPDm references:
*
* Mobile Station - Base Stations System (MS - BSS) Interface Data Link (DL) Layer Specification
* Base Station Controller - Base Transceiver Station (BSC - BTS) interface; Layer 2 specification
* http://www.3gpp.org/ftp/Specs/html-info/44006.htm
*
* From 3GPP TS 44.006:
*
* LAPDm is used for information sent on the control channels BCCH, AGCH, NCH,
* PCH, FACCH, SACCH and SDCCH as defined in 3GPP TS 44.003.
*
* AGCH, NCH and PCH are sometimes referred to by the collective name CCCH.
* FACCH, SACCH and SDCCH are, similarly, referred to by the collective name DCCH.
*
* Format A is used on DCCHs for frames where there is no information field.
* Formats B, Bter and B4 are used on DCCHs for frames containing an information field:
* Format Bter is used on request of higher layers if and only if short L2 header type 1 is
* supported and a UI command is to be transmitted on SAPI 0;
* Format B4 is used for UI frames transmitted by the network on SACCH;
* Format B is applied in all other cases.
* Format Bbis is used only on BCCH, PCH, NCH, and AGCH.
* In addition there is a Format C for transmission of random access signals.
*
* This module currently supports A, B, B4
* In the future will support Bter
* Bbis and C should be supported elsewhere
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/prefs.h>
#include <epan/xdlc.h>
#include <epan/reassemble.h>
void proto_register_lapdm(void);
static int proto_lapdm = -1;
static int hf_lapdm_address = -1;
static int hf_lapdm_ea = -1;
static int hf_lapdm_cr = -1;
static int hf_lapdm_sapi = -1;
static int hf_lapdm_lpd = -1;
static int hf_lapdm_control = -1;
static int hf_lapdm_n_r = -1;
static int hf_lapdm_n_s = -1;
static int hf_lapdm_p = -1;
static int hf_lapdm_f = -1;
static int hf_lapdm_s_ftype = -1;
static int hf_lapdm_u_modifier_cmd = -1;
static int hf_lapdm_u_modifier_resp = -1;
static int hf_lapdm_ftype_i = -1;
static int hf_lapdm_ftype_s_u = -1;
static int hf_lapdm_length = -1;
static int hf_lapdm_el = -1;
static int hf_lapdm_m = -1;
static int hf_lapdm_len = -1;
/*
* LAPDm fragment handling
*/
static int hf_lapdm_fragment_data = -1;
static int hf_lapdm_fragments = -1;
static int hf_lapdm_fragment = -1;
static int hf_lapdm_fragment_overlap = -1;
static int hf_lapdm_fragment_overlap_conflicts = -1;
static int hf_lapdm_fragment_multiple_tails = -1;
static int hf_lapdm_fragment_too_long_fragment = -1;
static int hf_lapdm_fragment_error = -1;
static int hf_lapdm_fragment_count = -1;
static int hf_lapdm_reassembled_in = -1;
static int hf_lapdm_reassembled_length = -1;
static gint ett_lapdm = -1;
static gint ett_lapdm_address = -1;
static gint ett_lapdm_control = -1;
static gint ett_lapdm_length = -1;
static gint ett_lapdm_fragment = -1;
static gint ett_lapdm_fragments = -1;
static reassembly_table lapdm_reassembly_table;
static wmem_map_t *lapdm_last_n_s_map;
static dissector_table_t lapdm_sapi_dissector_table;
static gboolean reassemble_lapdm = TRUE;
/*
* Bits in the address field.
*/
#define LAPDM_SAPI 0x1c /* Service Access Point Identifier */
#define LAPDM_SAPI_SHIFT 2
#define LAPDM_CR 0x02 /* Command/Response bit */
#define LAPDM_EA 0x01 /* First Address Extension bit */
#define LAPDM_LPD 0x60 /* Link Protocol Discriminator */
/*
* Bits in the length field.
*/
#define LAPDM_EL 0x01 /* Extended Length = 1 */
#define LAPDM_M 0x02 /* More fragments */
#define LAPDM_M_SHIFT 1
#define LAPDM_LEN 0xfc /* Length */
#define LAPDM_LEN_SHIFT 2
#define LAPDM_HEADER_LEN 3
#define LAPDM_SAPI_RR_CC_MM 0
#define LAPDM_SAPI_SMS 3
/* Used only for U frames */
static const xdlc_cf_items lapdm_cf_items = {
&hf_lapdm_n_r,
&hf_lapdm_n_s,
&hf_lapdm_p,
&hf_lapdm_f,
&hf_lapdm_s_ftype,
&hf_lapdm_u_modifier_cmd,
&hf_lapdm_u_modifier_resp,
&hf_lapdm_ftype_i,
&hf_lapdm_ftype_s_u
};
static const value_string lapdm_ea_vals[] = {
{ 0, "More octets" },
{ 1, "Final octet" },
{ 0, NULL }
};
static const value_string lapdm_sapi_vals[] = {
{ LAPDM_SAPI_RR_CC_MM, "RR/MM/CC" },
{ LAPDM_SAPI_SMS, "SMS/SS" },
{ 0, NULL }
};
static const value_string lapdm_lpd_vals[] = {
{ 0, "Normal GSM" },
{ 1, "Cell broadcast service" },
{ 0, NULL }
};
static const value_string lapdm_m_vals[] = {
{ 0, "Last segment" },
{ 1, "More segments" },
{ 0, NULL }
};
static const value_string lapdm_el_vals[] = {
{ 0, "More octets" },
{ 1, "Final octet" },
{ 0, NULL }
};
static const fragment_items lapdm_frag_items = {
/* Fragment subtrees */
&ett_lapdm_fragment,
&ett_lapdm_fragments,
/* Fragment fields */
&hf_lapdm_fragments,
&hf_lapdm_fragment,
&hf_lapdm_fragment_overlap,
&hf_lapdm_fragment_overlap_conflicts,
&hf_lapdm_fragment_multiple_tails,
&hf_lapdm_fragment_too_long_fragment,
&hf_lapdm_fragment_error,
&hf_lapdm_fragment_count,
/* Reassembled in field */
&hf_lapdm_reassembled_in,
/* Reassembled length field */
&hf_lapdm_reassembled_length,
/* Reassembled data field */
NULL,
/* Tag */
"fragments"
};
static void
lapdm_defragment_init (void)
{
reassembly_table_init (&lapdm_reassembly_table,
&addresses_reassembly_table_functions);
lapdm_last_n_s_map = wmem_map_new(wmem_file_scope(), g_direct_hash, g_direct_equal);
}
static void
lapdm_defragment_cleanup (void)
{
reassembly_table_destroy(&lapdm_reassembly_table);
}
static int
dissect_lapdm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
proto_tree *lapdm_tree, *addr_tree, *length_tree;
proto_item *lapdm_ti, *addr_ti, *length_ti;
guint8 addr, length, cr, sapi, len, n_s;
int control;
gboolean m;
tvbuff_t *payload;
int available_length;
gboolean is_response = FALSE;
/* Check that there's enough data */
if (tvb_captured_length(tvb) < LAPDM_HEADER_LEN)
return 0;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPDm");
addr = tvb_get_guint8(tvb, 0);
length = tvb_get_guint8(tvb, 2);
cr = addr & LAPDM_CR;
if (pinfo->p2p_dir == P2P_DIR_RECV) {
is_response = cr ? FALSE : TRUE;
}
else if (pinfo->p2p_dir == P2P_DIR_SENT) {
is_response = cr ? TRUE : FALSE;
}
if (tree) {
lapdm_ti = proto_tree_add_item(tree, proto_lapdm, tvb, 0, LAPDM_HEADER_LEN, ENC_NA);
lapdm_tree = proto_item_add_subtree(lapdm_ti, ett_lapdm);
addr_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_address, tvb, 0, 1, addr);
addr_tree = proto_item_add_subtree(addr_ti, ett_lapdm_address);
proto_tree_add_uint(addr_tree, hf_lapdm_lpd, tvb, 0, 1, addr);
proto_tree_add_uint(addr_tree, hf_lapdm_sapi, tvb, 0, 1, addr);
proto_tree_add_uint(addr_tree, hf_lapdm_cr, tvb, 0, 1, addr);
proto_tree_add_uint(addr_tree, hf_lapdm_ea, tvb, 0, 1, addr);
}
else {
lapdm_ti = NULL;
lapdm_tree = NULL;
}
control = dissect_xdlc_control(tvb, 1, pinfo, lapdm_tree, hf_lapdm_control,
ett_lapdm_control, &lapdm_cf_items, NULL /* LAPDm doesn't support extended */, NULL, NULL,
is_response, FALSE, FALSE);
if (tree) {
length_ti = proto_tree_add_uint(lapdm_tree, hf_lapdm_length, tvb,
2, 1, length);
length_tree = proto_item_add_subtree(length_ti, ett_lapdm_length);
proto_tree_add_uint(length_tree, hf_lapdm_len, tvb, 2, 1, length);
proto_tree_add_uint(length_tree, hf_lapdm_m, tvb, 2, 1, length);
proto_tree_add_uint(length_tree, hf_lapdm_el, tvb, 2, 1, length);
}
sapi = (addr & LAPDM_SAPI) >> LAPDM_SAPI_SHIFT;
len = (length & LAPDM_LEN) >> LAPDM_LEN_SHIFT;
n_s = (control & XDLC_N_S_MASK) >> XDLC_N_S_SHIFT;
m = (length & LAPDM_M) >> LAPDM_M_SHIFT;
available_length = tvb_captured_length(tvb) - LAPDM_HEADER_LEN;
/* No point in doing anything if no payload
*/
if( !MIN(len, available_length) )
return 2;
payload = tvb_new_subset(tvb, LAPDM_HEADER_LEN, MIN(len,available_length), len);
/* Potentially segmented I frame
*/
if( (control & XDLC_I_MASK) == XDLC_I && reassemble_lapdm && !pinfo->flags.in_error_pkt )
{
fragment_head *fd_m = NULL;
tvbuff_t *reassembled = NULL;
guint32 fragment_id;
gboolean save_fragmented = pinfo->fragmented, add_frag;
pinfo->fragmented = m;
/* Rely on caller to provide a way to group fragments */
fragment_id = (pinfo->circuit_id << 4) | (sapi << 1) | pinfo->p2p_dir;
if (!PINFO_FD_VISITED(pinfo)) {
/* Check if new N(S) is equal to previous N(S) (to avoid adding retransmissions in reassembly table)
As GUINT_TO_POINTER macro does not allow to differentiate NULL from 0, use 1-8 range instead of 0-7 */
guint *p_last_n_s = (guint*)wmem_map_lookup(lapdm_last_n_s_map, GUINT_TO_POINTER(fragment_id));
if (GPOINTER_TO_UINT(p_last_n_s) == (guint)(n_s+1)) {
add_frag = FALSE;
} else {
add_frag = TRUE;
wmem_map_insert(lapdm_last_n_s_map, GUINT_TO_POINTER(fragment_id), GUINT_TO_POINTER(n_s+1));
}
} else {
add_frag = TRUE;
}
if (add_frag) {
/* This doesn't seem the best way of doing it as doesn't
take N(S) into account, but N(S) isn't always 0 for
the first fragment!
*/
fd_m = fragment_add_seq_next (&lapdm_reassembly_table, payload, 0,
pinfo,
fragment_id, /* guint32 ID for fragments belonging together */
NULL,
/*n_s guint32 fragment sequence number */
len, /* guint32 fragment length */
m); /* More fragments? */
reassembled = process_reassembled_data(payload, 0, pinfo,
"Reassembled LAPDm", fd_m, &lapdm_frag_items,
NULL, lapdm_tree);
/* Reassembled into this packet
*/
if (fd_m && pinfo->num == fd_m->reassembled_in) {
if (!dissector_try_uint(lapdm_sapi_dissector_table, sapi,
reassembled, pinfo, tree))
call_data_dissector(reassembled, pinfo, tree);
}
else {
col_append_str(pinfo->cinfo, COL_INFO, " (Fragment)");
proto_tree_add_item(lapdm_tree, hf_lapdm_fragment_data, payload, 0, -1, ENC_NA);
}
}
/* Now reset fragmentation information in pinfo
*/
pinfo->fragmented = save_fragmented;
}
else
{
if (!PINFO_FD_VISITED(pinfo) && ((control & XDLC_S_U_MASK) == XDLC_U) && ((control & XDLC_U_MODIFIER_MASK) == XDLC_SABM)) {
/* SABM frame; reset the last N(S) to an invalid value */
guint32 fragment_id = (pinfo->circuit_id << 4) | (sapi << 1) | pinfo->p2p_dir;
wmem_map_insert(lapdm_last_n_s_map, GUINT_TO_POINTER(fragment_id), GUINT_TO_POINTER(0));
}
/* Whole packet
If we have some data, try and dissect it (only happens for UI, SABM, UA or I frames)
*/
if (!dissector_try_uint(lapdm_sapi_dissector_table, sapi,
payload, pinfo, tree))
call_data_dissector(payload, pinfo, tree);
}
return tvb_captured_length(tvb);
}
void
proto_register_lapdm(void)
{
static hf_register_info hf[] = {
{ &hf_lapdm_address,
{ "Address Field", "lapdm.address_field", FT_UINT8, BASE_HEX, NULL, 0x0,
"Address", HFILL }},
{ &hf_lapdm_ea,
{ "EA", "lapdm.ea", FT_UINT8, BASE_DEC, VALS(lapdm_ea_vals), LAPDM_EA,
"Address field extension bit", HFILL }},
{ &hf_lapdm_cr,
{ "C/R", "lapdm.cr", FT_UINT8, BASE_DEC, NULL, LAPDM_CR,
"Command/response field bit", HFILL }},
{ &hf_lapdm_lpd,
{ "LPD", "lapdm.lpd", FT_UINT8, BASE_DEC, VALS(lapdm_lpd_vals), LAPDM_LPD,
"Link Protocol Discriminator", HFILL }},
{ &hf_lapdm_sapi,
{ "SAPI", "lapdm.sapi", FT_UINT8, BASE_DEC, VALS(lapdm_sapi_vals), LAPDM_SAPI,
"Service access point identifier", HFILL }},
{ &hf_lapdm_control,
{ "Control Field", "lapdm.control_field", FT_UINT8, BASE_HEX, NULL, 0x0,
NULL, HFILL }},
{ &hf_lapdm_n_r,
{ "N(R)", "lapdm.control.n_r", FT_UINT8, BASE_DEC,
NULL, XDLC_N_R_MASK, NULL, HFILL }},
{ &hf_lapdm_n_s,
{ "N(S)", "lapdm.control.n_s", FT_UINT8, BASE_DEC,
NULL, XDLC_N_S_MASK, NULL, HFILL }},
{ &hf_lapdm_p,
{ "Poll", "lapdm.control.p", FT_BOOLEAN, 8,
TFS(&tfs_true_false), XDLC_P_F, NULL, HFILL }},
{ &hf_lapdm_f,
{ "Final", "lapdm.control.f", FT_BOOLEAN, 8,
TFS(&tfs_true_false), XDLC_P_F, NULL, HFILL }},
{ &hf_lapdm_s_ftype,
{ "Supervisory frame type", "lapdm.control.s_ftype", FT_UINT8, BASE_HEX,
VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
{ &hf_lapdm_u_modifier_cmd,
{ "Command", "lapdm.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
{ &hf_lapdm_u_modifier_resp,
{ "Response", "lapdm.control.u_modifier_resp", FT_UINT8, BASE_HEX,
VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
{ &hf_lapdm_ftype_i,
{ "Frame type", "lapdm.control.ftype", FT_UINT8, BASE_HEX,
VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
{ &hf_lapdm_ftype_s_u,
{ "Frame type", "lapdm.control.ftype", FT_UINT8, BASE_HEX,
VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
{ &hf_lapdm_length,
{ "Length Field", "lapdm.length_field", FT_UINT8, BASE_HEX,
NULL, 0x0, NULL, HFILL }},
{ &hf_lapdm_el,
{ "EL", "lapdm.el", FT_UINT8, BASE_DEC,
VALS(lapdm_el_vals), LAPDM_EL, "Length indicator field extension bit", HFILL }},
{ &hf_lapdm_m,
{ "M", "lapdm.m", FT_UINT8, BASE_DEC,
VALS(lapdm_m_vals), LAPDM_M, "More data bit", HFILL }},
{ &hf_lapdm_len,
{ "Length", "lapdm.length", FT_UINT8, BASE_DEC,
NULL, LAPDM_LEN, "Length indicator", HFILL }},
/* Fragment reassembly
*/
{ &hf_lapdm_fragment_data,
{ "Fragment Data", "lapdm.fragment_data", FT_NONE, BASE_NONE,
NULL, 0x00, NULL, HFILL }},
{ &hf_lapdm_fragments,
{ "Message fragments", "lapdm.fragments", FT_NONE, BASE_NONE,
NULL, 0x00, "LAPDm Message fragments", HFILL }},
{ &hf_lapdm_fragment,
{ "Message fragment", "lapdm.fragment", FT_FRAMENUM, BASE_NONE,
NULL, 0x00, "LAPDm Message fragment", HFILL }},
{ &hf_lapdm_fragment_overlap,
{ "Message fragment overlap", "lapdm.fragment.overlap", FT_BOOLEAN, BASE_NONE,
NULL, 0x0, "LAPDm Message fragment overlaps with other fragment(s)", HFILL }},
{ &hf_lapdm_fragment_overlap_conflicts,
{ "Message fragment overlapping with conflicting data", "lapdm.fragment.overlap.conflicts", FT_BOOLEAN, BASE_NONE,
NULL, 0x0, "LAPDm Message fragment overlaps with conflicting data", HFILL }},
{ &hf_lapdm_fragment_multiple_tails,
{ "Message has multiple tail fragments", "lapdm.fragment.multiple_tails", FT_BOOLEAN, BASE_NONE,
NULL, 0x0, "LAPDm Message fragment has multiple tail fragments", HFILL }},
{ &hf_lapdm_fragment_too_long_fragment,
{ "Message fragment too long", "lapdm.fragment.too_long_fragment", FT_BOOLEAN, BASE_NONE,
NULL, 0x0, "LAPDm Message fragment data goes beyond the packet end", HFILL }},
{ &hf_lapdm_fragment_error,
{ "Message defragmentation error", "lapdm.fragment.error", FT_FRAMENUM, BASE_NONE,
NULL, 0x00, "LAPDm Message defragmentation error due to illegal fragments", HFILL }},
{ &hf_lapdm_fragment_count,
{ "Message fragment count", "lapdm.fragment.count", FT_UINT32, BASE_DEC,
NULL, 0x00, NULL, HFILL }},
{ &hf_lapdm_reassembled_in,
{ "Reassembled in", "lapdm.reassembled.in", FT_FRAMENUM, BASE_NONE,
NULL, 0x00, "LAPDm Message has been reassembled in this packet.", HFILL }},
{ &hf_lapdm_reassembled_length,
{ "Reassembled LAPDm length", "lapdm.reassembled.length", FT_UINT32, BASE_DEC,
NULL, 0x00, "The total length of the reassembled payload", HFILL }}
};
static gint *ett[] = {
&ett_lapdm,
&ett_lapdm_address,
&ett_lapdm_control,
&ett_lapdm_length,
&ett_lapdm_fragment,
&ett_lapdm_fragments
};
module_t *lapdm_module;
proto_lapdm = proto_register_protocol("Link Access Procedure, Channel Dm (LAPDm)", "LAPDm", "lapdm");
proto_register_field_array (proto_lapdm, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
register_dissector("lapdm", dissect_lapdm, proto_lapdm);
lapdm_sapi_dissector_table = register_dissector_table("lapdm.sapi", "LAPDm SAPI", proto_lapdm, FT_UINT8, BASE_DEC);
lapdm_module = prefs_register_protocol(proto_lapdm, NULL);
prefs_register_bool_preference(lapdm_module, "reassemble",
"Reassemble fragmented LAPDm packets",
"Whether the dissector should defragment LAPDm messages spanning multiple packets.",
&reassemble_lapdm);
register_init_routine (lapdm_defragment_init);
register_cleanup_routine (lapdm_defragment_cleanup);
}
/*
* Editor modelines - http://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:
*/