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 1.29 2002/02/22 08:54:54 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 #ifdef HAVE_SYS_TYPES_H
  31 # include <sys/types.h>
  32 #endif
  33
  34 #include <stdio.h>
  35 #include <glib.h>
  36 #include <string.h>
  37 #include <epan/packet.h>
  38 #include "xdlc.h"
  39
  40 /* ISDN/LAPD references:
  41  *
  42  * http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm
  43  * http://www.ece.wpi.edu/courses/ee535/hwk11cd95/agrebe/agrebe.html
  44  * http://www.acacia-net.com/Clarinet/Protocol/q9213o84.htm
  45  */
  46
  47 static int proto_lapd = -1;
  48 static int hf_lapd_address = -1;
  49 static int hf_lapd_sapi = -1;
  50 static int hf_lapd_cr = -1;
  51 static int hf_lapd_ea1 = -1;
  52 static int hf_lapd_tei = -1;
  53 static int hf_lapd_ea2 = -1;
  54 static int hf_lapd_control = -1;
  55
  56 static gint ett_lapd = -1;
  57 static gint ett_lapd_address = -1;
  58 static gint ett_lapd_control = -1;
  59
  60 static dissector_handle_t q931_handle;
  61 static dissector_handle_t data_handle;
  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 static void
  87 dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  88 {
  89         proto_tree      *lapd_tree, *addr_tree;
  90         proto_item      *lapd_ti, *addr_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         if (check_col(pinfo->cinfo, COL_PROTOCOL))
  98                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPD");
  99         if (check_col(pinfo->cinfo, COL_INFO))
 100                 col_clear(pinfo->cinfo, COL_INFO);
 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->p2p.sent) {
 108                 is_response = cr ? TRUE : FALSE;
 109                 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 110                         col_set_str(pinfo->cinfo, COL_RES_DL_DST, "Network");
 111                 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 112                         col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "User");
 113         }
 114         else {
 115                 is_response = cr ? FALSE : TRUE;
 116                 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 117                     col_set_str(pinfo->cinfo, COL_RES_DL_DST, "User");
 118                 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 119                     col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "Network");
 120         }
 121
 122         if (tree) {
 123                 lapd_ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, -1,
 124                     FALSE);
 125                 lapd_tree = proto_item_add_subtree(lapd_ti, ett_lapd);
 126
 127                 addr_ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb,
 128                     0, 2, address);
 129                 addr_tree = proto_item_add_subtree(addr_ti, ett_lapd_address);
 130
 131                 proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, address);
 132                 proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, address);
 133                 proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, address);
 134                 proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, address);
 135                 proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, address);
 136         }
 137         else {
 138                 lapd_ti = NULL;
 139                 lapd_tree = NULL;
 140         }
 141
 142         control = dissect_xdlc_control(tvb, 2, pinfo, lapd_tree, hf_lapd_control,
 143             ett_lapd_control, is_response, TRUE);
 144         lapd_header_len += XDLC_CONTROL_LEN(control, TRUE);
 145
 146         if (tree)
 147                 proto_item_set_len(lapd_ti, lapd_header_len);
 148
 149         next_tvb = tvb_new_subset(tvb, lapd_header_len, -1, -1);
 150         if (XDLC_IS_INFORMATION(control)) {
 151                 /* call next protocol */
 152                 switch (sapi) {
 153
 154                 case LAPD_SAPI_Q931:
 155                         call_dissector(q931_handle, next_tvb, pinfo, tree);
 156                         break;
 157
 158                 default:
 159                         call_dissector(data_handle,next_tvb, pinfo, tree);
 160                         break;
 161                 }
 162         } else
 163                 call_dissector(data_handle,next_tvb, pinfo, tree);
 164 }
 165
 166 void
 167 proto_register_lapd(void)
 168 {
 169     static hf_register_info hf[] = {
 170         { &hf_lapd_address,
 171           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 172                 "Address", HFILL }},
 173
 174         { &hf_lapd_sapi,
 175           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 176                 "Service Access Point Identifier", HFILL }},
 177
 178         { &hf_lapd_cr,
 179           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 180                 "Command/Response bit", HFILL }},
 181
 182         { &hf_lapd_ea1,
 183           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 184                 "First Address Extension bit", HFILL }},
 185
 186         { &hf_lapd_tei,
 187           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 188                 "Terminal Endpoint Identifier", HFILL }},
 189
 190         { &hf_lapd_ea2,
 191           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 192                 "Second Address Extension bit", HFILL }},
 193
 194         { &hf_lapd_control,
 195           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 196                 "Control field", HFILL }},
 197     };
 198     static gint *ett[] = {
 199         &ett_lapd,
 200         &ett_lapd_address,
 201         &ett_lapd_control,
 202     };
 203
 204     proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",
 205                                          "LAPD", "lapd");
 206     proto_register_field_array (proto_lapd, hf, array_length(hf));
 207     proto_register_subtree_array(ett, array_length(ett));
 208 }
 209
 210 void
 211 proto_reg_handoff_lapd(void)
 212 {
 213         dissector_handle_t lapd_handle;
 214
 215         /*
 216          * Get handle for the Q.931 dissector.
 217          */
 218         q931_handle = find_dissector("q931");
 219         data_handle = find_dissector("data");
 220
 221         lapd_handle = create_dissector_handle(dissect_lapd, proto_lapd);
 222         dissector_add("wtap_encap", WTAP_ENCAP_LAPD, lapd_handle);
 223 }