packet-lapd.c

   1 /* packet-lapd.c
   2  * Routines for LAPD frame disassembly
   3  * Gilbert Ramirez <gram@xiexie.org>
   4  *
   5  * $Id: packet-lapd.c,v 1.20 2001/01/22 00:20:29 guy Exp $
   6  *
   7  * Ethereal - Network traffic analyzer
   8  * By Gerald Combs <gerald@zing.org>
   9  * Copyright 1998
  10  *
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  25  */
  26
  27 #ifdef HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #ifdef HAVE_SYS_TYPES_H
  32 # include <sys/types.h>
  33 #endif
  34
  35 #include <stdio.h>
  36 #include <glib.h>
  37 #include <string.h>
  38 #include "packet.h"
  39 #include "packet-q931.h"
  40 #include "xdlc.h"
  41
  42 /* ISDN/LAPD references:
  43  *
  44  * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm
  45  * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html
  46  * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm
  47  */
  48
  49 static int proto_lapd = -1;
  50 static int hf_lapd_address = -1;
  51 static int hf_lapd_sapi = -1;
  52 static int hf_lapd_cr = -1;
  53 static int hf_lapd_ea1 = -1;
  54 static int hf_lapd_tei = -1;
  55 static int hf_lapd_ea2 = -1;
  56 static int hf_lapd_control = -1;
  57
  58 static gint ett_lapd = -1;
  59 static gint ett_lapd_address = -1;
  60 static gint ett_lapd_control = -1;
  61
  62 /*
  63  * Bits in the address field.
  64  */
  65 #define LAPD_SAPI       0xfc00  /* Service Access Point Identifier */
  66 #define LAPD_SAPI_SHIFT 10
  67 #define LAPD_CR         0x0200  /* Command/Response bit */
  68 #define LAPD_EA1        0x0100  /* First Address Extension bit */
  69 #define LAPD_TEI        0x00fe  /* Terminal Endpoint Identifier */
  70 #define LAPD_EA2        0x0001  /* Second Address Extension bit */
  71
  72 #define LAPD_SAPI_Q931          0       /* Q.931 call control procedure */
  73 #define LAPD_SAPI_PM_Q931       1       /* Packet mode Q.931 call control procedure */
  74 #define LAPD_SAPI_X25           16      /* X.25 Level 3 procedures */
  75 #define LAPD_SAPI_L2            63      /* Layer 2 management procedures */
  76
  77 static const value_string lapd_sapi_vals[] = {
  78         { LAPD_SAPI_Q931,       "Q.931 Call control procedure" },
  79         { LAPD_SAPI_PM_Q931,    "Packet mode Q.931 Call control procedure" },
  80         { LAPD_SAPI_X25,        "X.25 Level 3 procedures" },
  81         { LAPD_SAPI_L2,         "Layer 2 management procedures" },
  82         { 0,                    NULL }
  83 };
  84
  85 static void
  86 dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  87 {
  88         proto_tree      *lapd_tree, *addr_tree;
  89         proto_item      *ti;
  90         guint16         control;
  91         int             lapd_header_len;
  92         guint16         address, cr, sapi;
  93         gboolean        is_response;
  94         tvbuff_t        *next_tvb;
  95
  96         if (check_col(pinfo->fd, COL_PROTOCOL))
  97                 col_set_str(pinfo->fd, COL_PROTOCOL, "LAPD");
  98         if (check_col(pinfo->fd, COL_INFO))
  99                 col_clear(pinfo->fd, COL_INFO);
 100
 101         address = tvb_get_ntohs(tvb, 0);
 102         cr = address & LAPD_CR;
 103         sapi = (address & LAPD_SAPI) >> LAPD_SAPI_SHIFT;
 104         lapd_header_len = 2;    /* address */
 105
 106         if (pinfo->pseudo_header->p2p.sent) {
 107                 is_response = cr ? TRUE : FALSE;
 108                 if(check_col(pinfo->fd, COL_RES_DL_DST))
 109                         col_set_str(pinfo->fd, COL_RES_DL_DST, "Network");
 110                 if(check_col(pinfo->fd, COL_RES_DL_SRC))
 111                         col_set_str(pinfo->fd, COL_RES_DL_SRC, "User");
 112         }
 113         else {
 114                 is_response = cr ? FALSE : TRUE;
 115                 if(check_col(pinfo->fd, COL_RES_DL_DST))
 116                     col_set_str(pinfo->fd, COL_RES_DL_DST, "User");
 117                 if(check_col(pinfo->fd, COL_RES_DL_SRC))
 118                     col_set_str(pinfo->fd, COL_RES_DL_SRC, "Network");
 119         }
 120
 121         if (tree) {
 122                 ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, 3, FALSE);
 123                 lapd_tree = proto_item_add_subtree(ti, ett_lapd);
 124
 125                 ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb, 0, 2, address);
 126                 addr_tree = proto_item_add_subtree(ti, ett_lapd_address);
 127
 128                 proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, address);
 129                 proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, address);
 130                 proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, address);
 131                 proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, address);
 132                 proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, address);
 133         }
 134         else {
 135                 lapd_tree = NULL;
 136         }
 137
 138         control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,
 139             ett_lapd_control, is_response, TRUE);
 140         lapd_header_len += XDLC_CONTROL_LEN(control, TRUE);
 141
 142         next_tvb = tvb_new_subset(tvb, lapd_header_len, -1, -1);
 143         if (XDLC_IS_INFORMATION(control)) {
 144                 /* call next protocol */
 145                 switch (sapi) {
 146
 147                 case LAPD_SAPI_Q931:
 148                         dissect_q931(next_tvb, pinfo, tree);
 149                         break;
 150
 151                 default:
 152                         dissect_data(next_tvb, 0, pinfo, tree);
 153                         break;
 154                 }
 155         } else
 156                 dissect_data(next_tvb, 0, pinfo, tree);
 157 }
 158
 159 void
 160 proto_register_lapd(void)
 161 {
 162     static hf_register_info hf[] = {
 163         { &hf_lapd_address,
 164           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 165                 "Address" }},
 166
 167         { &hf_lapd_sapi,
 168           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 169                 "Service Access Point Identifier" }},
 170
 171         { &hf_lapd_cr,
 172           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 173                 "Command/Response bit" }},
 174
 175         { &hf_lapd_ea1,
 176           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 177                 "First Address Extension bit" }},
 178
 179         { &hf_lapd_tei,
 180           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 181                 "Terminal Endpoint Identifier" }},
 182
 183         { &hf_lapd_ea2,
 184           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 185                 "Second Address Extension bit" }},
 186
 187         { &hf_lapd_control,
 188           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 189                 "Control field" }},
 190     };
 191     static gint *ett[] = {
 192         &ett_lapd,
 193         &ett_lapd_address,
 194         &ett_lapd_control,
 195     };
 196
 197     proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",
 198                                          "LAPD", "lapd");
 199     proto_register_field_array (proto_lapd, hf, array_length(hf));
 200     proto_register_subtree_array(ett, array_length(ett));
 201 }
 202
 203 void
 204 proto_reg_handoff_lapd(void)
 205 {
 206         dissector_add("wtap_encap", WTAP_ENCAP_LAPD, dissect_lapd, proto_lapd);
 207 }