epan/dissectors/packet-lapd.c

   1 /* packet-lapd.c
   2  * Routines for LAPD frame disassembly
   3  * Gilbert Ramirez <gram@alumni.rice.edu>
   4  *
   5  * $Id$
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  24  */
  25
  26 #ifdef HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include <stdio.h>
  31 #include <glib.h>
  32 #include <string.h>
  33 #include <epan/packet.h>
  34 #include <epan/xdlc.h>
  35
  36 #include <epan/lapd_sapi.h>
  37
  38 /* ISDN/LAPD references:
  39  *
  40  * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm
  41  * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html
  42  * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm
  43  */
  44
  45 static int proto_lapd = -1;
  46 static int hf_lapd_address = -1;
  47 static int hf_lapd_sapi = -1;
  48 static int hf_lapd_cr = -1;
  49 static int hf_lapd_ea1 = -1;
  50 static int hf_lapd_tei = -1;
  51 static int hf_lapd_ea2 = -1;
  52 static int hf_lapd_control = -1;
  53 static int hf_lapd_n_r = -1;
  54 static int hf_lapd_n_s = -1;
  55 static int hf_lapd_p = -1;
  56 static int hf_lapd_p_ext = -1;
  57 static int hf_lapd_f = -1;
  58 static int hf_lapd_f_ext = -1;
  59 static int hf_lapd_s_ftype = -1;
  60 static int hf_lapd_u_modifier_cmd = -1;
  61 static int hf_lapd_u_modifier_resp = -1;
  62 static int hf_lapd_ftype_i = -1;
  63 static int hf_lapd_ftype_s_u = -1;
  64 static int hf_lapd_ftype_s_u_ext = -1;
  65
  66 static gint ett_lapd = -1;
  67 static gint ett_lapd_address = -1;
  68 static gint ett_lapd_control = -1;
  69
  70 static dissector_table_t lapd_sapi_dissector_table;
  71
  72 static dissector_handle_t data_handle;
  73 static dissector_handle_t tei_handle;
  74
  75 /*
  76  * Bits in the address field.
  77  */
  78 #define LAPD_SAPI       0xfc00  /* Service Access Point Identifier */
  79 #define LAPD_SAPI_SHIFT 10
  80 #define LAPD_CR         0x0200  /* Command/Response bit */
  81 #define LAPD_EA1        0x0100  /* First Address Extension bit */
  82 #define LAPD_TEI        0x00fe  /* Terminal Endpoint Identifier */
  83 #define LAPD_TEI_SHIFT  1
  84 #define LAPD_EA2        0x0001  /* Second Address Extension bit */
  85
  86 static const value_string lapd_sapi_vals[] = {
  87         { LAPD_SAPI_Q931,       "Q.931 Call control procedure" },
  88         { LAPD_SAPI_PM_Q931,    "Packet mode Q.931 Call control procedure" },
  89         { LAPD_SAPI_X25,        "X.25 Level 3 procedures" },
  90         { LAPD_SAPI_L2,         "Layer 2 management procedures" },
  91         { 0,                    NULL }
  92 };
  93
  94 /* Used only for U frames */
  95 static const xdlc_cf_items lapd_cf_items = {
  96         NULL,
  97         NULL,
  98         &hf_lapd_p,
  99         &hf_lapd_f,
 100         NULL,
 101         &hf_lapd_u_modifier_cmd,
 102         &hf_lapd_u_modifier_resp,
 103         NULL,
 104         &hf_lapd_ftype_s_u
 105 };
 106
 107 /* Used only for I and S frames */
 108 static const xdlc_cf_items lapd_cf_items_ext = {
 109         &hf_lapd_n_r,
 110         &hf_lapd_n_s,
 111         &hf_lapd_p_ext,
 112         &hf_lapd_f_ext,
 113         &hf_lapd_s_ftype,
 114         NULL,
 115         NULL,
 116         &hf_lapd_ftype_i,
 117         &hf_lapd_ftype_s_u_ext
 118 };
 119
 120 static void
 121 dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 122 {
 123         proto_tree      *lapd_tree, *addr_tree;
 124         proto_item      *lapd_ti, *addr_ti;
 125         guint16         control;
 126         int             lapd_header_len;
 127         guint16         address, cr, sapi, tei;
 128         gboolean        is_response = 0;
 129         tvbuff_t        *next_tvb;
 130         char            *srcname = "?";
 131         char            *dstname = "?";
 132
 133         if (check_col(pinfo->cinfo, COL_PROTOCOL))
 134                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPD");
 135         if (check_col(pinfo->cinfo, COL_INFO))
 136                 col_clear(pinfo->cinfo, COL_INFO);
 137
 138         address = tvb_get_ntohs(tvb, 0);
 139         cr = address & LAPD_CR;
 140         tei = (address & LAPD_TEI) >> LAPD_TEI_SHIFT;
 141         sapi = (address & LAPD_SAPI) >> LAPD_SAPI_SHIFT;
 142         lapd_header_len = 2;    /* address */
 143
 144         if (check_col(pinfo->cinfo, COL_TEI))
 145                 col_add_fstr(pinfo->cinfo, COL_TEI, "%u", tei);
 146
 147         if (pinfo->fd->lnk_t == WTAP_ENCAP_LINUX_LAPD) {
 148                 /* frame is captured via libpcap */
 149                 if (pinfo->pseudo_header->lapd.pkttype == 4 /*PACKET_OUTGOING*/) {
 150                         if (pinfo->pseudo_header->lapd.we_network) {
 151                                 is_response = cr ? FALSE : TRUE;
 152                                 srcname = "Local Network";
 153                                 dstname = "Remote User";
 154                         } else {
 155                                 srcname = "Local User";
 156                                 dstname = "Remote Network";
 157                         }
 158                 }
 159                 else if (pinfo->pseudo_header->lapd.pkttype == 3 /*PACKET_OTHERHOST*/) {
 160                         // We must be a TE, sniffing what other TE transmit
 161
 162                         is_response = cr ? TRUE : FALSE;
 163                         srcname = "Remote User";
 164                         dstname = "Remote Network";
 165                 }
 166                 else {
 167                         // The frame is incoming
 168                         if (pinfo->pseudo_header->lapd.we_network) {
 169                                 is_response = cr ? TRUE : FALSE;
 170                                 srcname = "Remote User";
 171                                 dstname = "Local Network";
 172                         } else {
 173                                 is_response = cr ? FALSE : TRUE;
 174                                 srcname = "Remote Network";
 175                                 dstname = "Local User";
 176                         }
 177                 }
 178         }
 179         else if (pinfo->p2p_dir == P2P_DIR_SENT) {
 180                 is_response = cr ? FALSE : TRUE;
 181                 srcname = "Network";
 182                 dstname = "User";
 183         }
 184         else if (pinfo->p2p_dir == P2P_DIR_RECV) {
 185                 is_response = cr ? TRUE : FALSE;
 186                 srcname = "User";
 187                 dstname = "Network";
 188         }
 189
 190         if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 191             col_set_str(pinfo->cinfo, COL_RES_DL_SRC, srcname);
 192         if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 193             col_set_str(pinfo->cinfo, COL_RES_DL_DST, dstname);
 194
 195         if (tree) {
 196                 lapd_ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, -1,
 197                     FALSE);
 198                 lapd_tree = proto_item_add_subtree(lapd_ti, ett_lapd);
 199
 200                 addr_ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb,
 201                     0, 2, address);
 202                 addr_tree = proto_item_add_subtree(addr_ti, ett_lapd_address);
 203
 204                 proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, address);
 205                 proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, address);
 206                 proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, address);
 207                 proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, address);
 208                 proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, address);
 209         }
 210         else {
 211                 lapd_ti = NULL;
 212                 lapd_tree = NULL;
 213         }
 214
 215         control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,
 216             ett_lapd_control, &lapd_cf_items, &lapd_cf_items_ext, NULL, NULL,
 217             is_response, TRUE, FALSE);
 218         lapd_header_len += XDLC_CONTROL_LEN(control, TRUE);
 219
 220         if (tree)
 221                 proto_item_set_len(lapd_ti, lapd_header_len);
 222
 223         next_tvb = tvb_new_subset(tvb, lapd_header_len, -1, -1);
 224         if (XDLC_IS_INFORMATION(control)) {
 225                 /* call next protocol */
 226                 if (!dissector_try_port(lapd_sapi_dissector_table, sapi,
 227                     next_tvb, pinfo, tree))
 228                         call_dissector(data_handle,next_tvb, pinfo, tree);
 229         } else
 230                 call_dissector(data_handle,next_tvb, pinfo, tree);
 231 }
 232
 233 void
 234 proto_register_lapd(void)
 235 {
 236     static hf_register_info hf[] = {
 237         { &hf_lapd_address,
 238           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 239                 "Address", HFILL }},
 240
 241         { &hf_lapd_sapi,
 242           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 243                 "Service Access Point Identifier", HFILL }},
 244
 245         { &hf_lapd_cr,
 246           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 247                 "Command/Response bit", HFILL }},
 248
 249         { &hf_lapd_ea1,
 250           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 251                 "First Address Extension bit", HFILL }},
 252
 253         { &hf_lapd_tei,
 254           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 255                 "Terminal Endpoint Identifier", HFILL }},
 256
 257         { &hf_lapd_ea2,
 258           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 259                 "Second Address Extension bit", HFILL }},
 260
 261         { &hf_lapd_control,
 262           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 263                 "Control field", HFILL }},
 264
 265         { &hf_lapd_n_r,
 266             { "N(R)", "lapd.control.n_r", FT_UINT16, BASE_DEC,
 267                 NULL, XDLC_N_R_EXT_MASK, "", HFILL }},
 268
 269         { &hf_lapd_n_s,
 270             { "N(S)", "lapd.control.n_s", FT_UINT16, BASE_DEC,
 271                 NULL, XDLC_N_S_EXT_MASK, "", HFILL }},
 272
 273         { &hf_lapd_p,
 274             { "Poll", "lapd.control.p", FT_BOOLEAN, 8,
 275                 TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 276
 277         { &hf_lapd_p_ext,
 278             { "Poll", "lapd.control.p", FT_BOOLEAN, 16,
 279                 TFS(&flags_set_truth), XDLC_P_F_EXT, "", HFILL }},
 280
 281         { &hf_lapd_f,
 282             { "Final", "lapd.control.f", FT_BOOLEAN, 8,
 283                 TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 284
 285         { &hf_lapd_f_ext,
 286             { "Final", "lapd.control.f", FT_BOOLEAN, 16,
 287                 TFS(&flags_set_truth), XDLC_P_F_EXT, "", HFILL }},
 288
 289         { &hf_lapd_s_ftype,
 290             { "Supervisory frame type", "lapd.control.s_ftype", FT_UINT16, BASE_HEX,
 291                 VALS(stype_vals), XDLC_S_FTYPE_MASK, "", HFILL }},
 292
 293         { &hf_lapd_u_modifier_cmd,
 294             { "Command", "lapd.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 295                 VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, "", HFILL }},
 296
 297         { &hf_lapd_u_modifier_resp,
 298             { "Response", "lapd.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 299                 VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, "", HFILL }},
 300
 301         { &hf_lapd_ftype_i,
 302             { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,
 303                 VALS(ftype_vals), XDLC_I_MASK, "", HFILL }},
 304
 305         { &hf_lapd_ftype_s_u,
 306             { "Frame type", "lapd.control.ftype", FT_UINT8, BASE_HEX,
 307                 VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
 308
 309         { &hf_lapd_ftype_s_u_ext,
 310             { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,
 311                 VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
 312     };
 313     static gint *ett[] = {
 314         &ett_lapd,
 315         &ett_lapd_address,
 316         &ett_lapd_control,
 317     };
 318
 319     proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",
 320                                          "LAPD", "lapd");
 321     proto_register_field_array (proto_lapd, hf, array_length(hf));
 322     proto_register_subtree_array(ett, array_length(ett));
 323
 324     register_dissector("lapd", dissect_lapd, proto_lapd);
 325
 326     lapd_sapi_dissector_table = register_dissector_table("lapd.sapi",
 327             "LAPD SAPI", FT_UINT16, BASE_DEC);
 328 }
 329
 330 void
 331 proto_reg_handoff_lapd(void)
 332 {
 333         dissector_handle_t lapd_handle;
 334
 335         data_handle = find_dissector("data");
 336         tei_handle = find_dissector("tei");
 337
 338
 339         lapd_handle = create_dissector_handle(dissect_lapd, proto_lapd);
 340         dissector_add("wtap_encap", WTAP_ENCAP_LINUX_LAPD, lapd_handle);
 341 }