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 1.10 2000/05/31 03:58:54 gram 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-lapd.h"
  40 #include "packet-q931.h"
  41 #include "xdlc.h"
  42
  43 /* ISDN/LAPD references:
  44  *
  45  * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm
  46  * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html
  47  * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm
  48  */
  49
  50 static int proto_lapd = -1;
  51 static int hf_lapd_address = -1;
  52 static int hf_lapd_sapi = -1;
  53 static int hf_lapd_cr = -1;
  54 static int hf_lapd_ea1 = -1;
  55 static int hf_lapd_tei = -1;
  56 static int hf_lapd_ea2 = -1;
  57 static int hf_lapd_control = -1;
  58
  59 static gint ett_lapd = -1;
  60 static gint ett_lapd_address = -1;
  61 static gint ett_lapd_control = -1;
  62
  63 /*
  64  * Bits in the address field.
  65  */
  66 #define LAPD_SAPI       0xfc00  /* Service Access Point Identifier */
  67 #define LAPD_SAPI_SHIFT 10
  68 #define LAPD_CR         0x0200  /* Command/Response bit */
  69 #define LAPD_EA1        0x0100  /* First Address Extension bit */
  70 #define LAPD_TEI        0x00fe  /* Terminal Endpoint Identifier */
  71 #define LAPD_EA2        0x0001  /* Second Address Extension bit */
  72
  73 #define LAPD_SAPI_Q931          0       /* Q.931 call control procedure */
  74 #define LAPD_SAPI_PM_Q931       1       /* Packet mode Q.931 call control procedure */
  75 #define LAPD_SAPI_X25           16      /* X.25 Level 3 procedures */
  76 #define LAPD_SAPI_L2            63      /* Layer 2 management procedures */
  77
  78 static const value_string lapd_sapi_vals[] = {
  79         { LAPD_SAPI_Q931,       "Q.931 Call control procedure" },
  80         { LAPD_SAPI_PM_Q931,    "Packet mode Q.931 Call control procedure" },
  81         { LAPD_SAPI_X25,        "X.25 Level 3 procedures" },
  82         { LAPD_SAPI_L2,         "Layer 2 management procedures" },
  83         { 0,                    NULL }
  84 };
  85
  86 void
  87 dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  88 {
  89         proto_tree      *lapd_tree, *addr_tree;
  90         proto_item      *ti;
  91         guint16         control;
  92         int             lapd_header_len;
  93         guint16         address, cr, sapi;
  94         gboolean        is_response;
  95         tvbuff_t        *next_tvb;
  96
  97         pinfo->current_proto = "LAPD";
  98
  99         if (check_col(pinfo->fd, COL_PROTOCOL))
 100                 col_add_str(pinfo->fd, COL_PROTOCOL, "LAPD");
 101
 102         address = tvb_get_ntohs(tvb, 0);
 103         cr = address & LAPD_CR;
 104         sapi = (address & LAPD_SAPI) >> LAPD_SAPI_SHIFT;
 105         lapd_header_len = 2;    /* address */
 106
 107         if (pinfo->pseudo_header->lapd.from_network_to_user) {
 108                 is_response = cr ? FALSE : TRUE;
 109                 if(check_col(pinfo->fd, COL_RES_DL_DST))
 110                     col_add_str(pinfo->fd, COL_RES_DL_DST, "User");
 111                 if(check_col(pinfo->fd, COL_RES_DL_SRC))
 112                     col_add_str(pinfo->fd, COL_RES_DL_SRC, "Network");
 113         }
 114         else {
 115                 is_response = cr ? TRUE : FALSE;
 116                 if(check_col(pinfo->fd, COL_RES_DL_DST))
 117                         col_add_str(pinfo->fd, COL_RES_DL_DST, "Network");
 118                 if(check_col(pinfo->fd, COL_RES_DL_SRC))
 119                         col_add_str(pinfo->fd, COL_RES_DL_SRC, "User");
 120         }
 121
 122
 123         if (tree) {
 124                 ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, 3, NULL);
 125                 lapd_tree = proto_item_add_subtree(ti, ett_lapd);
 126
 127                 ti = proto_tree_add_item(lapd_tree, hf_lapd_address, tvb, 0, 2, address);
 128                 addr_tree = proto_item_add_subtree(ti, ett_lapd_address);
 129
 130                 proto_tree_add_item(addr_tree, hf_lapd_sapi,tvb, 0, 1, address);
 131                 proto_tree_add_item(addr_tree, hf_lapd_cr,  tvb, 0, 1, address);
 132                 proto_tree_add_item(addr_tree, hf_lapd_ea1, tvb, 0, 1, address);
 133                 proto_tree_add_item(addr_tree, hf_lapd_tei, tvb, 1, 1, address);
 134                 proto_tree_add_item(addr_tree, hf_lapd_ea2, tvb, 1, 1, address);
 135         }
 136         else {
 137                 lapd_tree = NULL;
 138         }
 139
 140         control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,
 141             ett_lapd_control, is_response, TRUE);
 142         lapd_header_len += XDLC_CONTROL_LEN(control, TRUE);
 143
 144         next_tvb = tvb_new_subset(tvb, lapd_header_len, -1, -1);
 145         if (XDLC_IS_INFORMATION(control)) {
 146                 /* call next protocol */
 147                 switch (sapi) {
 148
 149                 case LAPD_SAPI_Q931:
 150                         dissect_q931(next_tvb, pinfo, tree);
 151                         break;
 152
 153                 default:
 154                         dissect_data_tvb(next_tvb, pinfo, tree);
 155                         break;
 156                 }
 157         } else
 158                 dissect_data_tvb(next_tvb, pinfo, tree);
 159 }
 160
 161 void
 162 proto_register_lapd(void)
 163 {
 164     static hf_register_info hf[] = {
 165         { &hf_lapd_address,
 166           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 167                 "" }},
 168
 169         { &hf_lapd_sapi,
 170           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 171                 "Service Access Point Identifier" }},
 172
 173         { &hf_lapd_cr,
 174           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 175                 "Command/Response bit" }},
 176
 177         { &hf_lapd_ea1,
 178           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 179                 "First Address Extension bit" }},
 180
 181         { &hf_lapd_tei,
 182           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 183                 "Terminal Endpoint Identifier" }},
 184
 185         { &hf_lapd_ea2,
 186           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 187                 "Second Address Extension bit" }},
 188
 189         { &hf_lapd_control,
 190           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 191                 "" }},
 192     };
 193     static gint *ett[] = {
 194         &ett_lapd,
 195         &ett_lapd_address,
 196         &ett_lapd_control,
 197     };
 198
 199     proto_lapd = proto_register_protocol ("Link Access Procedure, Channel D (LAPD)", "lapd");
 200     proto_register_field_array (proto_lapd, hf, array_length(hf));
 201     proto_register_subtree_array(ett, array_length(ett));
 202 }