packet-sdlc.c

   1 /* packet-sdlc.c
   2  * Routines for SDLC frame disassembly
   3  *
   4  * $Id: packet-sdlc.c,v 1.4 2004/01/18 08:32:46 guy Exp $
   5  *
   6  * Ethereal - Network traffic analyzer
   7  * By Gerald Combs <gerald@ethereal.com>
   8  * Copyright 1998
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License
  12  * as published by the Free Software Foundation; either version 2
  13  * of the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  23  */
  24
  25 #ifdef HAVE_CONFIG_H
  26 # include "config.h"
  27 #endif
  28
  29 #include <stdio.h>
  30 #include <glib.h>
  31 #include <string.h>
  32 #include <epan/packet.h>
  33 #include "xdlc.h"
  34
  35 /*
  36  * See
  37  *
  38  *      http://www.protocols.com/pbook/sna.htm
  39  */
  40
  41 static int proto_sdlc = -1;
  42 static int hf_sdlc_address = -1;
  43 static int hf_sdlc_control = -1;
  44 static int hf_sdlc_n_r = -1;
  45 static int hf_sdlc_n_s = -1;
  46 static int hf_sdlc_p = -1;
  47 static int hf_sdlc_f = -1;
  48 static int hf_sdlc_s_ftype = -1;
  49 static int hf_sdlc_u_modifier_cmd = -1;
  50 static int hf_sdlc_u_modifier_resp = -1;
  51 static int hf_sdlc_ftype_i = -1;
  52 static int hf_sdlc_ftype_s_u = -1;
  53
  54 static gint ett_sdlc = -1;
  55 static gint ett_sdlc_control = -1;
  56
  57 static dissector_handle_t sna_handle;
  58 static dissector_handle_t data_handle;
  59
  60 static const xdlc_cf_items sdlc_cf_items = {
  61         &hf_sdlc_n_r,
  62         &hf_sdlc_n_s,
  63         &hf_sdlc_p,
  64         &hf_sdlc_f,
  65         &hf_sdlc_s_ftype,
  66         &hf_sdlc_u_modifier_cmd,
  67         &hf_sdlc_u_modifier_resp,
  68         &hf_sdlc_ftype_i,
  69         &hf_sdlc_ftype_s_u
  70 };
  71
  72 static void
  73 dissect_sdlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  74 {
  75         proto_tree      *sdlc_tree;
  76         proto_item      *sdlc_ti;
  77         guint8          address;
  78         guint16         control;
  79         int             sdlc_header_len;
  80         gboolean        is_response;
  81         tvbuff_t        *next_tvb;
  82
  83         if (check_col(pinfo->cinfo, COL_PROTOCOL))
  84                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "SDLC");
  85         if (check_col(pinfo->cinfo, COL_INFO))
  86                 col_clear(pinfo->cinfo, COL_INFO);
  87
  88         address = tvb_get_guint8(tvb, 0);
  89         sdlc_header_len = 1;    /* address */
  90
  91         /*
  92          * XXX - is there something in the SDLC header that indicates
  93          * how to interpret "command vs. response" based on the
  94          * direction?
  95          */
  96         if (pinfo->p2p_dir == P2P_DIR_SENT) {
  97                 is_response = FALSE;
  98                 if (check_col(pinfo->cinfo, COL_RES_DL_DST))
  99                         col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
 100                 if (check_col(pinfo->cinfo, COL_RES_DL_SRC))
 101                         col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
 102         }
 103         else {
 104                 /* XXX - what if the direction is unknown? */
 105                 is_response = TRUE;
 106                 if (check_col(pinfo->cinfo, COL_RES_DL_DST))
 107                     col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
 108                 if (check_col(pinfo->cinfo, COL_RES_DL_SRC))
 109                     col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
 110         }
 111
 112         if (tree) {
 113                 sdlc_ti = proto_tree_add_item(tree, proto_sdlc, tvb, 0, -1,
 114                     FALSE);
 115                 sdlc_tree = proto_item_add_subtree(sdlc_ti, ett_sdlc);
 116
 117                 proto_tree_add_uint(sdlc_tree, hf_sdlc_address, tvb, 0, 1,
 118                     address);
 119         } else {
 120                 sdlc_ti = NULL;
 121                 sdlc_tree = NULL;
 122         }
 123
 124         /*
 125          * XXX - SDLC has a mod-128 mode as well as a mod-7 mode.
 126          * We can infer the mode from an SNRM/SRME frame, but if
 127          * we don't see one of them, we may have to have a preference
 128          * to control what to use.
 129          */
 130         control = dissect_xdlc_control(tvb, 1, pinfo, sdlc_tree, hf_sdlc_control,
 131             ett_sdlc_control, &sdlc_cf_items, NULL, NULL, NULL,
 132             is_response, FALSE, FALSE);
 133         sdlc_header_len += XDLC_CONTROL_LEN(control, FALSE);
 134
 135         if (tree)
 136                 proto_item_set_len(sdlc_ti, sdlc_header_len);
 137
 138         /*
 139          * XXX - is there an FCS at the end, at least in Sniffer
 140          * captures?  (There doesn't appear to be.)
 141          */
 142         next_tvb = tvb_new_subset(tvb, sdlc_header_len, -1, -1);
 143         if (XDLC_IS_INFORMATION(control)) {
 144                 /* call the SNA dissector */
 145                 call_dissector(sna_handle, next_tvb, pinfo, tree);
 146         } else
 147                 call_dissector(data_handle, next_tvb, pinfo, tree);
 148 }
 149
 150 void
 151 proto_register_sdlc(void)
 152 {
 153         static hf_register_info hf[] = {
 154                 { &hf_sdlc_address,
 155                   { "Address Field", "sdlc.address", FT_UINT8, BASE_HEX,
 156                      NULL, 0x0, "Address", HFILL }},
 157
 158                 { &hf_sdlc_control,
 159                   { "Control Field", "sdlc.control", FT_UINT16, BASE_HEX,
 160                     NULL, 0x0, "Control field", HFILL }},
 161
 162                 { &hf_sdlc_n_r,
 163                     { "N(R)", "sdlc.control.n_r", FT_UINT8, BASE_DEC,
 164                       NULL, XDLC_N_R_MASK, "", HFILL }},
 165
 166                 { &hf_sdlc_n_s,
 167                     { "N(S)", "sdlc.control.n_s", FT_UINT8, BASE_DEC,
 168                       NULL, XDLC_N_S_MASK, "", HFILL }},
 169
 170                 { &hf_sdlc_p,
 171                     { "Poll", "sdlc.control.p", FT_BOOLEAN, 8,
 172                       TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 173
 174                 { &hf_sdlc_f,
 175                     { "Final", "sdlc.control.f", FT_BOOLEAN, 8,
 176                       TFS(&flags_set_truth), XDLC_P_F, "", HFILL }},
 177
 178                 { &hf_sdlc_s_ftype,
 179                     { "Supervisory frame type", "sdlc.control.s_ftype", FT_UINT8, BASE_HEX,
 180                       VALS(stype_vals), XDLC_S_FTYPE_MASK, "", HFILL }},
 181
 182                 { &hf_sdlc_u_modifier_cmd,
 183                     { "Command", "sdlc.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 184                       VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, "", HFILL }},
 185
 186                 { &hf_sdlc_u_modifier_resp,
 187                     { "Response", "sdlc.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 188                       VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, "", HFILL }},
 189
 190                 { &hf_sdlc_ftype_i,
 191                     { "Frame type", "sdlc.control.ftype", FT_UINT8, BASE_HEX,
 192                       VALS(ftype_vals), XDLC_I_MASK, "", HFILL }},
 193
 194                 { &hf_sdlc_ftype_s_u,
 195                     { "Frame type", "sdlc.control.ftype", FT_UINT8, BASE_HEX,
 196                       VALS(ftype_vals), XDLC_S_U_MASK, "", HFILL }},
 197         };
 198         static gint *ett[] = {
 199                 &ett_sdlc,
 200                 &ett_sdlc_control,
 201         };
 202
 203         proto_sdlc = proto_register_protocol(
 204             "Synchronous Data Link Control (SDLC)", "SDLC", "sdlc");
 205         proto_register_field_array(proto_sdlc, hf, array_length(hf));
 206         proto_register_subtree_array(ett, array_length(ett));
 207 }
 208
 209 void
 210 proto_reg_handoff_sdlc(void)
 211 {
 212         dissector_handle_t sdlc_handle;
 213
 214         /*
 215          * Get handle for the SNA dissector.
 216          */
 217         sna_handle = find_dissector("sna");
 218         data_handle = find_dissector("data");
 219
 220         sdlc_handle = create_dissector_handle(dissect_sdlc, proto_sdlc);
 221         dissector_add("wtap_encap", WTAP_ENCAP_SDLC, sdlc_handle);
 222 }