packet-lapd.c

   1 /* packet-lapd.c
   2  * Routines for LAPD frame disassembly
   3  * Gilbert Ramirez <gram@alumni.rice.edu>
   4  *
   5  * $Id: packet-lapd.c,v 1.37 2004/01/18 08:32:45 guy Exp $
   6  *
   7  * Ethereal - Network traffic analyzer
   8  * By Gerald Combs <gerald@ethereal.com>
   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 "xdlc.h"
  35
  36 /* ISDN/LAPD references:
  37  *
  38  * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm
  39  * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html
  40  * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm
  41  */
  42
  43 static int proto_lapd = -1;
  44 static int hf_lapd_address = -1;
  45 static int hf_lapd_sapi = -1;
  46 static int hf_lapd_cr = -1;
  47 static int hf_lapd_ea1 = -1;
  48 static int hf_lapd_tei = -1;
  49 static int hf_lapd_ea2 = -1;
  50 static int hf_lapd_control = -1;
  51 static int hf_lapd_n_r = -1;
  52 static int hf_lapd_n_s = -1;
  53 static int hf_lapd_p = -1;
  54 static int hf_lapd_p_ext = -1;
  55 static int hf_lapd_f = -1;
  56 static int hf_lapd_f_ext = -1;
  57 static int hf_lapd_s_ftype = -1;
  58 static int hf_lapd_u_modifier_cmd = -1;
  59 static int hf_lapd_u_modifier_resp = -1;
  60 static int hf_lapd_ftype_i = -1;
  61 static int hf_lapd_ftype_s_u = -1;
  62 static int hf_lapd_ftype_s_u_ext = -1;
  63
  64 static gint ett_lapd = -1;
  65 static gint ett_lapd_address = -1;
  66 static gint ett_lapd_control = -1;
  67
  68 static dissector_handle_t q931_handle;
  69 static dissector_handle_t data_handle;
  70
  71 /*
  72  * Bits in the address field.
  73  */
  74 #define LAPD_SAPI       0xfc00  /* Service Access Point Identifier */
  75 #define LAPD_SAPI_SHIFT 10
  76 #define LAPD_CR         0x0200  /* Command/Response bit */
  77 #define LAPD_EA1        0x0100  /* First Address Extension bit */
  78 #define LAPD_TEI        0x00fe  /* Terminal Endpoint Identifier */
  79 #define LAPD_EA2        0x0001  /* Second Address Extension bit */
  80
  81 #define LAPD_SAPI_Q931          0       /* Q.931 call control procedure */
  82 #define LAPD_SAPI_PM_Q931       1       /* Packet mode Q.931 call control procedure */
  83 #define LAPD_SAPI_X25           16      /* X.25 Level 3 procedures */
  84 #define LAPD_SAPI_L2            63      /* Layer 2 management procedures */
  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;
 128         gboolean        is_response;
 129         tvbuff_t        *next_tvb;
 130
 131         if (check_col(pinfo->cinfo, COL_PROTOCOL))
 132                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPD");
 133         if (check_col(pinfo->cinfo, COL_INFO))
 134                 col_clear(pinfo->cinfo, COL_INFO);
 135
 136         address = tvb_get_ntohs(tvb, 0);
 137         cr = address & LAPD_CR;
 138         sapi = (address & LAPD_SAPI) >> LAPD_SAPI_SHIFT;
 139         lapd_header_len = 2;    /* address */
 140
 141         if (pinfo->p2p_dir == P2P_DIR_SENT) {
 142                 is_response = cr ? TRUE : FALSE;
 143                 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 144                         col_set_str(pinfo->cinfo, COL_RES_DL_DST, "Network");
 145                 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 146                         col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "User");
 147         }
 148         else {
 149                 /* XXX - what if the direction is unknown? */
 150                 is_response = cr ? FALSE : TRUE;
 151                 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 152                     col_set_str(pinfo->cinfo, COL_RES_DL_DST, "User");
 153                 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 154                     col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "Network");
 155         }
 156
 157         if (tree) {
 158                 lapd_ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, -1,
 159                     FALSE);
 160                 lapd_tree = proto_item_add_subtree(lapd_ti, ett_lapd);
 161
 162                 addr_ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb,
 163                     0, 2, address);
 164                 addr_tree = proto_item_add_subtree(addr_ti, ett_lapd_address);
 165
 166                 proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, address);
 167                 proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, address);
 168                 proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, address);
 169                 proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, address);
 170                 proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, address);
 171         }
 172         else {
 173                 lapd_ti = NULL;
 174                 lapd_tree = NULL;
 175         }
 176
 177         control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,
 178             ett_lapd_control, &lapd_cf_items, &lapd_cf_items_ext, NULL, NULL,
 179             is_response, TRUE, FALSE);
 180         lapd_header_len += XDLC_CONTROL_LEN(control, TRUE);
 181
 182         if (tree)
 183                 proto_item_set_len(lapd_ti, lapd_header_len);
 184
 185         next_tvb = tvb_new_subset(tvb, lapd_header_len, -1, -1);
 186         if (XDLC_IS_INFORMATION(control)) {
 187                 /* call next protocol */
 188                 switch (sapi) {
 189
 190                 case LAPD_SAPI_Q931:
 191                         call_dissector(q931_handle, next_tvb, pinfo, tree);
 192                         break;
 193
 194                 default:
 195                         /*
 196                          * XXX - handle some of the others, such as
 197                          * LAPD_SAPI_L2.
 198                          */
 199                         call_dissector(data_handle, next_tvb, pinfo, tree);
 200                         break;
 201                 }
 202         } else
 203                 call_dissector(data_handle,next_tvb, pinfo, tree);
 204 }
 205
 206 void
 207 proto_register_lapd(void)
 208 {
 209     static hf_register_info hf[] = {
 210         { &hf_lapd_address,
 211           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 212                 "Address", HFILL }},
 213
 214         { &hf_lapd_sapi,
 215           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 216                 "Service Access Point Identifier", HFILL }},
 217
 218         { &hf_lapd_cr,
 219           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 220                 "Command/Response bit", HFILL }},
 221
 222         { &hf_lapd_ea1,
 223           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 224                 "First Address Extension bit", HFILL }},
 225
 226         { &hf_lapd_tei,
 227           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 228                 "Terminal Endpoint Identifier", HFILL }},
 229
 230         { &hf_lapd_ea2,
 231           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 232                 "Second Address Extension bit", HFILL }},
 233
 234         { &hf_lapd_control,
 235           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 236                 "Control field", HFILL }},
 237
 238         { &hf_lapd_n_r,
 239             { "N(R)", "lapd.control.n_r", FT_UINT16, BASE_DEC,
 240                 NULL, XDLC_N_R_EXT_MASK, "", HFILL }},
 241
 242         { &hf_lapd_n_s,
 243             { "N(S)", "lapd.control.n_s", FT_UINT16, BASE_DEC,
 244                 NULL, XDLC_N_S_EXT_MASK, "", HFILL }},
 245
 246         { &hf_lapd_p,
 247             { "Poll", "lapd.control.p", FT_BOOLEAN, 8,
 248                 TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 249
 250         { &hf_lapd_p_ext,
 251             { "Poll", "lapd.control.p", FT_BOOLEAN, 16,
 252                 TFS(&flags_set_truth), XDLC_P_F_EXT, "", HFILL }},
 253
 254         { &hf_lapd_f,
 255             { "Final", "lapd.control.f", FT_BOOLEAN, 8,
 256                 TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 257
 258         { &hf_lapd_f_ext,
 259             { "Final", "lapd.control.f", FT_BOOLEAN, 16,
 260                 TFS(&flags_set_truth), XDLC_P_F_EXT, "", HFILL }},
 261
 262         { &hf_lapd_s_ftype,
 263             { "Supervisory frame type", "lapd.control.s_ftype", FT_UINT16, BASE_HEX,
 264                 VALS(stype_vals), XDLC_S_FTYPE_MASK, "", HFILL }},
 265
 266         { &hf_lapd_u_modifier_cmd,
 267             { "Command", "lapd.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 268                 VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, "", HFILL }},
 269
 270         { &hf_lapd_u_modifier_resp,
 271             { "Response", "lapd.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 272                 VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, "", HFILL }},
 273
 274         { &hf_lapd_ftype_i,
 275             { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,
 276                 VALS(ftype_vals), XDLC_I_MASK, "", HFILL }},
 277
 278         { &hf_lapd_ftype_s_u,
 279             { "Frame type", "lapd.control.ftype", FT_UINT8, BASE_HEX,
 280                 VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
 281
 282         { &hf_lapd_ftype_s_u_ext,
 283             { "Frame type", "lapd.control.ftype", FT_UINT16, BASE_HEX,
 284                 VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
 285     };
 286     static gint *ett[] = {
 287         &ett_lapd,
 288         &ett_lapd_address,
 289         &ett_lapd_control,
 290     };
 291
 292     proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",
 293                                          "LAPD", "lapd");
 294     proto_register_field_array (proto_lapd, hf, array_length(hf));
 295     proto_register_subtree_array(ett, array_length(ett));
 296
 297     register_dissector("lapd", dissect_lapd, proto_lapd);
 298 }
 299
 300 void
 301 proto_reg_handoff_lapd(void)
 302 {
 303         /*
 304          * Get handle for the Q.931 dissector.
 305          */
 306         q931_handle = find_dissector("q931");
 307         data_handle = find_dissector("data");
 308 }