packet-lapb.c

   1 /* packet-lapb.c
   2  * Routines for lapb frame disassembly
   3  * Olivier Abad <oabad@noos.fr>
   4  *
   5  * $Id: packet-lapb.c,v 1.42 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 static int proto_lapb = -1;
  37 static int hf_lapb_address = -1;
  38 static int hf_lapb_control = -1;
  39 static int hf_lapb_n_r = -1;
  40 static int hf_lapb_n_s = -1;
  41 static int hf_lapb_p = -1;
  42 static int hf_lapb_f = -1;
  43 static int hf_lapb_s_ftype = -1;
  44 static int hf_lapb_u_modifier_cmd = -1;
  45 static int hf_lapb_u_modifier_resp = -1;
  46 static int hf_lapb_ftype_i = -1;
  47 static int hf_lapb_ftype_s_u = -1;
  48
  49 static gint ett_lapb = -1;
  50 static gint ett_lapb_control = -1;
  51
  52 static dissector_handle_t x25_dir_handle;
  53 static dissector_handle_t x25_handle;
  54
  55 static const xdlc_cf_items lapb_cf_items = {
  56         &hf_lapb_n_r,
  57         &hf_lapb_n_s,
  58         &hf_lapb_p,
  59         &hf_lapb_f,
  60         &hf_lapb_s_ftype,
  61         &hf_lapb_u_modifier_cmd,
  62         &hf_lapb_u_modifier_resp,
  63         &hf_lapb_ftype_i,
  64         &hf_lapb_ftype_s_u
  65 };
  66
  67 static void
  68 dissect_lapb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  69 {
  70     proto_tree          *lapb_tree, *ti;
  71     int                 is_response;
  72     guint8              byte0;
  73     tvbuff_t            *next_tvb;
  74
  75     if (check_col(pinfo->cinfo, COL_PROTOCOL))
  76         col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPB");
  77     if (check_col(pinfo->cinfo, COL_INFO))
  78         col_clear(pinfo->cinfo, COL_INFO);
  79
  80     switch (pinfo->p2p_dir) {
  81
  82     case P2P_DIR_SENT:
  83         if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
  84             col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
  85         if(check_col(pinfo->cinfo, COL_RES_DL_DST))
  86             col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
  87         break;
  88
  89     case P2P_DIR_RECV:
  90         if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
  91             col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
  92         if(check_col(pinfo->cinfo, COL_RES_DL_DST))
  93             col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
  94         break;
  95
  96     default:
  97         if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
  98             col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A");
  99         if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 100             col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A");
 101         break;
 102     }
 103
 104     byte0 = tvb_get_guint8(tvb, 0);
 105
 106     if (byte0 != 0x01 && byte0 != 0x03) /* invalid LAPB frame */
 107     {
 108         if (check_col(pinfo->cinfo, COL_INFO))
 109             col_set_str(pinfo->cinfo, COL_INFO, "Invalid LAPB frame");
 110         if (tree)
 111             ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, -1,
 112                             "Invalid LAPB frame");
 113         return;
 114     }
 115
 116     switch (pinfo->p2p_dir) {
 117
 118     case P2P_DIR_SENT:
 119         if (byte0 == 0x03)
 120             is_response = TRUE;
 121         else
 122             is_response = FALSE;
 123         break;
 124
 125     case P2P_DIR_RECV:
 126         if (byte0 == 0x01)
 127             is_response = TRUE;
 128         else
 129             is_response = FALSE;
 130         break;
 131
 132     default:
 133         /*
 134          * XXX - should we base this on the source and destination
 135          * addresses?  The problem is that we can tell one direction
 136          * from another with that, but we can't say which is DTE->DCE
 137          * and which is DCE->DTE.
 138          */
 139         is_response = FALSE;
 140         break;
 141     }
 142
 143     if (tree) {
 144         ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, 2,
 145                                             "LAPB");
 146         lapb_tree = proto_item_add_subtree(ti, ett_lapb);
 147         proto_tree_add_uint_format(lapb_tree, hf_lapb_address, tvb, 0, 1, byte0,
 148                                        "Address: 0x%02X", byte0);
 149     }
 150     else
 151         lapb_tree = NULL;
 152
 153     dissect_xdlc_control(tvb, 1, pinfo, lapb_tree, hf_lapb_control,
 154             ett_lapb_control, &lapb_cf_items, NULL, NULL, NULL,
 155             is_response, FALSE, FALSE);
 156
 157     /* not end of frame ==> X.25 */
 158     if (tvb_reported_length(tvb) > 2) {
 159         next_tvb = tvb_new_subset(tvb, 2, -1, -1);
 160         switch (pinfo->p2p_dir) {
 161
 162         case P2P_DIR_SENT:
 163         case P2P_DIR_RECV:
 164             call_dissector(x25_dir_handle, next_tvb, pinfo, tree);
 165             break;
 166
 167         default:
 168             call_dissector(x25_handle, next_tvb, pinfo, tree);
 169             break;
 170         }
 171     }
 172 }
 173
 174 void
 175 proto_register_lapb(void)
 176 {
 177     static hf_register_info hf[] = {
 178         { &hf_lapb_address,
 179           { "Address Field", "lapb.address", FT_UINT8, BASE_HEX, NULL, 0x0,
 180                 "Address", HFILL }},
 181
 182         { &hf_lapb_control,
 183           { "Control Field", "lapb.control", FT_UINT8, BASE_HEX, NULL, 0x0,
 184                 "Control field", HFILL }},
 185
 186         { &hf_lapb_n_r,
 187             { "N(R)", "lapb.control.n_r", FT_UINT8, BASE_DEC,
 188               NULL, XDLC_N_R_MASK, "", HFILL }},
 189
 190         { &hf_lapb_n_s,
 191             { "N(S)", "lapb.control.n_s", FT_UINT8, BASE_DEC,
 192               NULL, XDLC_N_S_MASK, "", HFILL }},
 193
 194         { &hf_lapb_p,
 195             { "Poll", "lapb.control.p", FT_BOOLEAN, 8,
 196               TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 197
 198         { &hf_lapb_f,
 199             { "Final", "lapb.control.f", FT_BOOLEAN, 8,
 200               TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 201
 202         { &hf_lapb_s_ftype,
 203             { "Supervisory frame type", "lapb.control.s_ftype", FT_UINT8, BASE_HEX,
 204               VALS(stype_vals), XDLC_S_FTYPE_MASK, "", HFILL }},
 205
 206         { &hf_lapb_u_modifier_cmd,
 207             { "Command", "lapb.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 208               VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, "", HFILL }},
 209
 210         { &hf_lapb_u_modifier_resp,
 211             { "Response", "lapb.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 212               VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, "", HFILL }},
 213
 214         { &hf_lapb_ftype_i,
 215             { "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX,
 216               VALS(ftype_vals), XDLC_I_MASK, "", HFILL }},
 217
 218         { &hf_lapb_ftype_s_u,
 219             { "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX,
 220               VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
 221     };
 222     static gint *ett[] = {
 223         &ett_lapb,
 224         &ett_lapb_control,
 225     };
 226
 227     proto_lapb = proto_register_protocol("Link Access Procedure Balanced (LAPB)",
 228                                          "LAPB", "lapb");
 229     proto_register_field_array (proto_lapb, hf, array_length(hf));
 230     proto_register_subtree_array(ett, array_length(ett));
 231
 232     register_dissector("lapb", dissect_lapb, proto_lapb);
 233 }
 234
 235 void
 236 proto_reg_handoff_lapb(void)
 237 {
 238     dissector_handle_t lapb_handle;
 239
 240     /*
 241      * Get handles for the X.25 dissectors; we don't get an X.25
 242      * pseudo-header for LAPB-over-Ethernet, but we do get it
 243      * for raw LAPB.
 244      */
 245     x25_dir_handle = find_dissector("x.25_dir");
 246     x25_handle = find_dissector("x.25");
 247
 248     lapb_handle = find_dissector("lapb");
 249     dissector_add("wtap_encap", WTAP_ENCAP_LAPB, lapb_handle);
 250 }