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 1.31 2002/08/28 21:00:19 jmayer 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
  52 static gint ett_lapd = -1;
  53 static gint ett_lapd_address = -1;
  54 static gint ett_lapd_control = -1;
  55
  56 static dissector_handle_t q931_handle;
  57 static dissector_handle_t data_handle;
  58
  59 /*
  60  * Bits in the address field.
  61  */
  62 #define LAPD_SAPI       0xfc00  /* Service Access Point Identifier */
  63 #define LAPD_SAPI_SHIFT 10
  64 #define LAPD_CR         0x0200  /* Command/Response bit */
  65 #define LAPD_EA1        0x0100  /* First Address Extension bit */
  66 #define LAPD_TEI        0x00fe  /* Terminal Endpoint Identifier */
  67 #define LAPD_EA2        0x0001  /* Second Address Extension bit */
  68
  69 #define LAPD_SAPI_Q931          0       /* Q.931 call control procedure */
  70 #define LAPD_SAPI_PM_Q931       1       /* Packet mode Q.931 call control procedure */
  71 #define LAPD_SAPI_X25           16      /* X.25 Level 3 procedures */
  72 #define LAPD_SAPI_L2            63      /* Layer 2 management procedures */
  73
  74 static const value_string lapd_sapi_vals[] = {
  75         { LAPD_SAPI_Q931,       "Q.931 Call control procedure" },
  76         { LAPD_SAPI_PM_Q931,    "Packet mode Q.931 Call control procedure" },
  77         { LAPD_SAPI_X25,        "X.25 Level 3 procedures" },
  78         { LAPD_SAPI_L2,         "Layer 2 management procedures" },
  79         { 0,                    NULL }
  80 };
  81
  82 static void
  83 dissect_lapd(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  84 {
  85         proto_tree      *lapd_tree, *addr_tree;
  86         proto_item      *lapd_ti, *addr_ti;
  87         guint16         control;
  88         int             lapd_header_len;
  89         guint16         address, cr, sapi;
  90         gboolean        is_response;
  91         tvbuff_t        *next_tvb;
  92
  93         if (check_col(pinfo->cinfo, COL_PROTOCOL))
  94                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPD");
  95         if (check_col(pinfo->cinfo, COL_INFO))
  96                 col_clear(pinfo->cinfo, COL_INFO);
  97
  98         address = tvb_get_ntohs(tvb, 0);
  99         cr = address & LAPD_CR;
 100         sapi = (address & LAPD_SAPI) >> LAPD_SAPI_SHIFT;
 101         lapd_header_len = 2;    /* address */
 102
 103         if (pinfo->pseudo_header->p2p.sent) {
 104                 is_response = cr ? TRUE : FALSE;
 105                 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 106                         col_set_str(pinfo->cinfo, COL_RES_DL_DST, "Network");
 107                 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 108                         col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "User");
 109         }
 110         else {
 111                 is_response = cr ? FALSE : TRUE;
 112                 if(check_col(pinfo->cinfo, COL_RES_DL_DST))
 113                     col_set_str(pinfo->cinfo, COL_RES_DL_DST, "User");
 114                 if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
 115                     col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "Network");
 116         }
 117
 118         if (tree) {
 119                 lapd_ti = proto_tree_add_item(tree, proto_lapd, tvb, 0, -1,
 120                     FALSE);
 121                 lapd_tree = proto_item_add_subtree(lapd_ti, ett_lapd);
 122
 123                 addr_ti = proto_tree_add_uint(lapd_tree, hf_lapd_address, tvb,
 124                     0, 2, address);
 125                 addr_tree = proto_item_add_subtree(addr_ti, ett_lapd_address);
 126
 127                 proto_tree_add_uint(addr_tree, hf_lapd_sapi,tvb, 0, 1, address);
 128                 proto_tree_add_uint(addr_tree, hf_lapd_cr,  tvb, 0, 1, address);
 129                 proto_tree_add_uint(addr_tree, hf_lapd_ea1, tvb, 0, 1, address);
 130                 proto_tree_add_uint(addr_tree, hf_lapd_tei, tvb, 1, 1, address);
 131                 proto_tree_add_uint(addr_tree, hf_lapd_ea2, tvb, 1, 1, address);
 132         }
 133         else {
 134                 lapd_ti = NULL;
 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         if (tree)
 143                 proto_item_set_len(lapd_ti, lapd_header_len);
 144
 145         next_tvb = tvb_new_subset(tvb, lapd_header_len, -1, -1);
 146         if (XDLC_IS_INFORMATION(control)) {
 147                 /* call next protocol */
 148                 switch (sapi) {
 149
 150                 case LAPD_SAPI_Q931:
 151                         call_dissector(q931_handle, next_tvb, pinfo, tree);
 152                         break;
 153
 154                 default:
 155                         call_dissector(data_handle,next_tvb, pinfo, tree);
 156                         break;
 157                 }
 158         } else
 159                 call_dissector(data_handle,next_tvb, pinfo, tree);
 160 }
 161
 162 void
 163 proto_register_lapd(void)
 164 {
 165     static hf_register_info hf[] = {
 166         { &hf_lapd_address,
 167           { "Address Field", "lapd.address", FT_UINT16, BASE_HEX, NULL, 0x0,
 168                 "Address", HFILL }},
 169
 170         { &hf_lapd_sapi,
 171           { "SAPI", "lapd.sapi", FT_UINT16, BASE_DEC, VALS(lapd_sapi_vals), LAPD_SAPI,
 172                 "Service Access Point Identifier", HFILL }},
 173
 174         { &hf_lapd_cr,
 175           { "C/R", "lapd.cr", FT_UINT16, BASE_DEC, NULL, LAPD_CR,
 176                 "Command/Response bit", HFILL }},
 177
 178         { &hf_lapd_ea1,
 179           { "EA1", "lapd.ea1", FT_UINT16, BASE_DEC, NULL, LAPD_EA1,
 180                 "First Address Extension bit", HFILL }},
 181
 182         { &hf_lapd_tei,
 183           { "TEI", "lapd.tei", FT_UINT16, BASE_DEC, NULL, LAPD_TEI,
 184                 "Terminal Endpoint Identifier", HFILL }},
 185
 186         { &hf_lapd_ea2,
 187           { "EA2", "lapd.ea2", FT_UINT16, BASE_DEC, NULL, LAPD_EA2,
 188                 "Second Address Extension bit", HFILL }},
 189
 190         { &hf_lapd_control,
 191           { "Control Field", "lapd.control", FT_UINT16, BASE_HEX, NULL, 0x0,
 192                 "Control field", HFILL }},
 193     };
 194     static gint *ett[] = {
 195         &ett_lapd,
 196         &ett_lapd_address,
 197         &ett_lapd_control,
 198     };
 199
 200     proto_lapd = proto_register_protocol("Link Access Procedure, Channel D (LAPD)",
 201                                          "LAPD", "lapd");
 202     proto_register_field_array (proto_lapd, hf, array_length(hf));
 203     proto_register_subtree_array(ett, array_length(ett));
 204 }
 205
 206 void
 207 proto_reg_handoff_lapd(void)
 208 {
 209         dissector_handle_t lapd_handle;
 210
 211         /*
 212          * Get handle for the Q.931 dissector.
 213          */
 214         q931_handle = find_dissector("q931");
 215         data_handle = find_dissector("data");
 216
 217         lapd_handle = create_dissector_handle(dissect_lapd, proto_lapd);
 218         dissector_add("wtap_encap", WTAP_ENCAP_LAPD, lapd_handle);
 219 }