epan/dissectors/packet-ax25-kiss.c

   1 /* packet-ax25-kiss.c
   2  *
   3  * Routines for AX.25 KISS protocol dissection
   4  * Copyright 2010,2012 R.W. Stearn <richard@rns-stearn.demon.co.uk>
   5  *
   6  * $Id$
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@wireshark.org>
  10  * Copyright 1998 Gerald Combs
  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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  25  */
  26
  27 /*
  28  * This dissector handles the "KISS" protocol as implemented by the
  29  * Linux kernel.
  30  *
  31  * The original definition of the KISS protocol can be found here:
  32  *   http://www.ka9q.net/papers/kiss.html
  33  * and here:
  34  *   http://www.ax25.net/kiss.aspx
  35  *
  36  * The Linux implementation does not appear to attempt to implement that
  37  * protocol in full. It does provide the ability to send a KISS command via
  38  * ax25_kiss_cmd() and internally will send FULLDUPLEX KISS commands if
  39  * DAMA is enabled/disabled.
  40  * i.e.:
  41  *      ax25_dev_dama_on  sends FullDuplex ON
  42  *      ax25_dev_dama_off sends FullDuplex OFF
  43  *
  44  * Data frames are prefixed with a "Data Frame" command but the port appears to
  45  * be always 0.
  46  *
  47  * Abstract from http://www.ka9q.net/papers/kiss.html
  48  * --------------------------------------------------
  49  * For reference the first byte of a KISS frame is the frame type and the TNC
  50  * port number,
  51  *   LSB 4 bits = frame type,
  52  *   MSB 4 bits = port number.
  53  *
  54  * The frame types are:
  55  * Command        Function         Comments
  56  *    0           Data frame       The  rest  of the frame is data to
  57  *                                 be sent on the HDLC channel.
  58  *
  59  *    1           TXDELAY          The next  byte  is  the  transmitter
  60  *                                 keyup  delay  in  10 ms units.
  61  *                                 The default start-up value is 50
  62  *                                 (i.e., 500 ms).
  63  *
  64  *    2           P                The next byte  is  the  persistence
  65  *                                 parameter,  p, scaled to the range
  66  *                                 0 - 255 with the following
  67  *                                 formula:
  68  *
  69  *                                          P = p * 256 - 1
  70  *
  71  *                                 The  default  value  is  P  =  63
  72  *                                 (i.e.,  p  =  0.25).
  73  *
  74  *    3           SlotTime         The next byte is the slot interval
  75  *                                 in 10 ms units.
  76  *                                 The default is 10 (i.e., 100ms).
  77  *
  78  *    4           TXtail           The next byte is the time to hold
  79  *                                 up the TX after the FCS has been
  80  *                                 sent, in 10 ms units.  This command
  81  *                                 is obsolete, and is included  here
  82  *                                 only for  compatibility  with  some
  83  *                                 existing  implementations.
  84  *
  85  *    5          FullDuplex        The next byte is 0 for half duplex,
  86  *                                 nonzero  for full  duplex.
  87  *                                 The  default  is  0
  88  *                                 (i.e.,  half  duplex).
  89  *
  90  *    6          SetHardware       Specific for each TNC.  In the
  91  *                                 TNC-1, this command  sets  the
  92  *                                 modem speed.  Other implementations
  93  *                                 may use this function  for   other
  94  *                                 hardware-specific   functions.
  95  *
  96  *    FF         Return            Exit KISS and return control to a
  97  *                                 higher-level program. This is useful
  98  *                                 only when KISS is  incorporated
  99  *                                 into  the TNC along with other
 100  *                                 applications.
 101  *
 102 */
 103
 104 #include "config.h"
 105
 106 #include <glib.h>
 107
 108 #include <epan/packet.h>
 109 #include <epan/emem.h>
 110
 111 #include "packet-ax25-kiss.h"
 112 #include "packet-ax25.h"
 113
 114 #define STRLEN  80
 115
 116 #define KISS_HEADER_SIZE         1 /* length of the KISS type header */
 117
 118 /* KISS frame types */
 119 #define KISS_DATA_FRAME          0
 120 #define KISS_TXDELAY             1
 121 #define KISS_PERSISTENCE         2
 122 #define KISS_SLOT_TIME           3
 123 #define KISS_TXTAIL              4
 124 #define KISS_FULLDUPLEX          5
 125 #define KISS_SETHARDWARE         6
 126 #define KISS_RETURN             15
 127
 128 #define KISS_CMD_MASK           0x0f
 129 #define KISS_PORT_MASK          0xf0
 130
 131 void proto_register_ax25_kiss(void);
 132 void proto_reg_handoff_ax25_kiss(void);
 133
 134 /* Initialize the protocol and registered fields */
 135 static int proto_ax25_kiss           = -1;
 136
 137 static int hf_ax25_kiss_cmd             = -1;
 138 static int hf_ax25_kiss_port            = -1;
 139 static int hf_ax25_kiss_txdelay         = -1;
 140 static int hf_ax25_kiss_persistence     = -1;
 141 static int hf_ax25_kiss_slottime        = -1;
 142 static int hf_ax25_kiss_txtail          = -1;
 143 static int hf_ax25_kiss_fullduplex      = -1;
 144 static int hf_ax25_kiss_sethardware     = -1;
 145
 146 /* Initialize the subtree pointers */
 147 static gint ett_ax25_kiss = -1;
 148
 149 static dissector_handle_t kiss_handle;
 150
 151 /* Dissector handles - all the possibles are listed */
 152 static dissector_handle_t ax25_handle;
 153
 154 static const value_string kiss_frame_types[] = {
 155         { KISS_DATA_FRAME,  "Data frame" },
 156         { KISS_TXDELAY,     "Tx Delay" },
 157         { KISS_PERSISTENCE, "Persistence" },
 158         { KISS_SLOT_TIME,   "Slot time" },
 159         { KISS_TXTAIL,      "Tx tail" },
 160         { KISS_FULLDUPLEX,  "Full duplex" },
 161         { KISS_SETHARDWARE, "Set hardware" },
 162         { KISS_RETURN,      "Return" },
 163         { 0, NULL }
 164 };
 165
 166 void
 167 capture_ax25_kiss( const guchar *pd, int offset, int len, packet_counts *ld)
 168 {
 169         int    l_offset;
 170         guint8 kiss_cmd;
 171
 172         if ( ! BYTES_ARE_IN_FRAME( offset, len, KISS_HEADER_SIZE ) )
 173                 {
 174                 ld->other++;
 175                 return;
 176                 }
 177
 178         l_offset  = offset;
 179         kiss_cmd  = pd[ l_offset ];
 180         l_offset += KISS_HEADER_SIZE; /* step over kiss header */
 181         switch ( kiss_cmd & KISS_CMD_MASK )
 182                 {
 183                 case KISS_DATA_FRAME    : capture_ax25( pd, l_offset, len, ld ); break;
 184                 case KISS_TXDELAY       : break;
 185                 case KISS_PERSISTENCE   : break;
 186                 case KISS_SLOT_TIME     : break;
 187                 case KISS_TXTAIL        : break;
 188                 case KISS_FULLDUPLEX    : break;
 189                 case KISS_SETHARDWARE   : break;
 190                 case KISS_RETURN        : break;
 191                 default                 : break;
 192                 }
 193 }
 194
 195 /* Code to actually dissect the packets */
 196 static void
 197 dissect_ax25_kiss( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree )
 198 {
 199         proto_item *ti;
 200         proto_tree *kiss_tree;
 201         int         offset;
 202         int         kiss_cmd;
 203         int         kiss_type;
 204         int         kiss_port;
 205         int         kiss_param;
 206         int         kiss_param_len;
 207         const char *frame_type_text;
 208         char       *info_buffer;
 209         void       *saved_private_data;
 210         tvbuff_t   *next_tvb = NULL;
 211
 212         info_buffer    = (char *)ep_alloc( STRLEN );
 213         info_buffer[0] = '\0';
 214
 215         col_set_str( pinfo->cinfo, COL_PROTOCOL, "AX.25 KISS" );
 216         col_clear( pinfo->cinfo, COL_INFO );
 217
 218         /* protocol offset for the KISS header */
 219         offset = 0;
 220
 221         kiss_cmd   = tvb_get_guint8( tvb, offset ) & 0xff;
 222         kiss_type  = kiss_cmd & KISS_CMD_MASK;
 223         kiss_port  = (kiss_cmd & KISS_PORT_MASK) >> 4;
 224         offset    += KISS_HEADER_SIZE;
 225
 226         kiss_param      = 0;
 227         kiss_param_len  = 0;
 228         switch ( kiss_type )
 229                 {
 230                 case KISS_TXDELAY       : kiss_param_len = 1; kiss_param = tvb_get_guint8( tvb, offset ) & 0xff; break;
 231                 case KISS_PERSISTENCE   : kiss_param_len = 1; kiss_param = tvb_get_guint8( tvb, offset ) & 0xff; break;
 232                 case KISS_SLOT_TIME     : kiss_param_len = 1; kiss_param = tvb_get_guint8( tvb, offset ) & 0xff; break;
 233                 case KISS_TXTAIL        : kiss_param_len = 1; kiss_param = tvb_get_guint8( tvb, offset ) & 0xff; break;
 234                 case KISS_FULLDUPLEX    : kiss_param_len = 1; kiss_param = tvb_get_guint8( tvb, offset ) & 0xff; break;
 235                 case KISS_SETHARDWARE   : kiss_param_len = 1; kiss_param = tvb_get_guint8( tvb, offset ) & 0xff; break;
 236                 default                 : break;
 237                 }
 238         frame_type_text = val_to_str(kiss_type, kiss_frame_types, "Unknown (%u)");
 239         g_snprintf( info_buffer, STRLEN, "%s, Port %u", frame_type_text, kiss_port );
 240         if ( kiss_param_len > 0 )
 241                 g_snprintf( info_buffer, STRLEN, "%s %u, Port %u", frame_type_text, kiss_param, kiss_port );
 242
 243         offset += kiss_param_len;
 244
 245         col_add_str( pinfo->cinfo, COL_INFO, info_buffer );
 246
 247         if ( parent_tree )
 248                 {
 249                 /* protocol offset for the KISS header */
 250                 offset = 0;
 251
 252                 /* create display subtree for the protocol */
 253                 ti = proto_tree_add_protocol_format( parent_tree, proto_ax25_kiss, tvb, offset,
 254                         KISS_HEADER_SIZE + kiss_param_len,
 255                         "KISS: %s",
 256                         info_buffer
 257                         );
 258
 259                 kiss_tree = proto_item_add_subtree( ti, ett_ax25_kiss );
 260
 261                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_cmd,  tvb, offset, KISS_HEADER_SIZE,
 262                                         kiss_cmd );
 263                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_port, tvb, offset, KISS_HEADER_SIZE,
 264                                         kiss_cmd );
 265                 offset += KISS_HEADER_SIZE;
 266
 267                 switch ( kiss_type  )
 268                         {
 269                         case KISS_DATA_FRAME    : break;
 270                         case KISS_TXDELAY       :
 271                                                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_txdelay,
 272                                                         tvb, offset, kiss_param_len, kiss_param );
 273                                                 offset += kiss_param_len;
 274                                                 break;
 275                         case KISS_PERSISTENCE   :
 276                                                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_persistence,
 277                                                         tvb, offset, kiss_param_len, kiss_param );
 278                                                 offset += kiss_param_len;
 279                                                 break;
 280                         case KISS_SLOT_TIME     :
 281                                                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_slottime,
 282                                                         tvb, offset, kiss_param_len, kiss_param );
 283                                                 offset += kiss_param_len;
 284                                                 break;
 285                         case KISS_TXTAIL        :
 286                                                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_txtail,
 287                                                         tvb, offset, kiss_param_len, kiss_param );
 288                                                 offset += kiss_param_len;
 289                                                 break;
 290                         case KISS_FULLDUPLEX    :
 291                                                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_fullduplex,
 292                                                         tvb, offset, kiss_param_len, kiss_param );
 293                                                 offset += kiss_param_len;
 294                                                 break;
 295                         case KISS_SETHARDWARE   :
 296                                                 proto_tree_add_uint( kiss_tree, hf_ax25_kiss_sethardware,
 297                                                         tvb, offset, kiss_param_len, kiss_param );
 298                                                 offset += kiss_param_len;
 299                                                 break;
 300                         case KISS_RETURN        : break;
 301                         default                 : break;
 302                         }
 303
 304         }
 305         /* Call sub-dissectors here */
 306
 307         if ( kiss_type == KISS_DATA_FRAME )
 308                 {
 309                 saved_private_data = pinfo->private_data;
 310                 next_tvb = tvb_new_subset_remaining( tvb, offset );
 311                 call_dissector( ax25_handle, next_tvb, pinfo, parent_tree );
 312                 pinfo->private_data = saved_private_data;
 313                 }
 314 }
 315
 316 void
 317 proto_register_ax25_kiss(void)
 318 {
 319         /* Setup list of header fields */
 320         static hf_register_info hf[] = {
 321                 { &hf_ax25_kiss_cmd,
 322                         { "Cmd",                        "ax25_kiss.cmd",
 323                         FT_UINT8, BASE_DEC, VALS(kiss_frame_types), KISS_CMD_MASK,
 324                         NULL, HFILL }
 325                 },
 326                 { &hf_ax25_kiss_port,
 327                         { "Port",                       "ax25_kiss.port",
 328                         FT_UINT8, BASE_DEC, NULL, KISS_PORT_MASK,
 329                         NULL, HFILL }
 330                 },
 331                 { &hf_ax25_kiss_txdelay,
 332                         { "Tx delay",                   "ax25_kiss.txdelay",
 333                         FT_UINT8, BASE_DEC, NULL, 0x0,
 334                         NULL, HFILL }
 335                 },
 336                 { &hf_ax25_kiss_persistence,
 337                         { "Persistence",                "ax25_kiss.persistence",
 338                         FT_UINT8, BASE_DEC, NULL, 0x0,
 339                         NULL, HFILL }
 340                 },
 341                 { &hf_ax25_kiss_slottime,
 342                         { "Slot time",                  "ax25_kiss.slottime",
 343                         FT_UINT8, BASE_DEC, NULL, 0x0,
 344                         NULL, HFILL }
 345                 },
 346                 { &hf_ax25_kiss_txtail,
 347                         { "Tx tail",                    "ax25_kiss.txtail",
 348                         FT_UINT8, BASE_DEC, NULL, 0x0,
 349                         NULL, HFILL }
 350                 },
 351                 { &hf_ax25_kiss_fullduplex,
 352                         { "Full duplex",                "ax25_kiss.fullduplex",
 353                         FT_UINT8, BASE_DEC, NULL, 0x0,
 354                         NULL, HFILL }
 355                 },
 356                 { &hf_ax25_kiss_sethardware,
 357                         { "Set hardware",               "ax25_kiss.sethardware",
 358                         FT_UINT8, BASE_DEC, NULL, 0x0,
 359                         NULL, HFILL }
 360                 },
 361         };
 362
 363         /* Setup protocol subtree array */
 364         static gint *ett[] = {
 365                 &ett_ax25_kiss,
 366         };
 367
 368         /* Register the protocol name and description */
 369         proto_ax25_kiss = proto_register_protocol( "AX.25 KISS", "AX.25 KISS", "ax25_kiss" );
 370
 371         /* Register the dissector */
 372         kiss_handle = register_dissector( "ax25_kiss", dissect_ax25_kiss, proto_ax25_kiss );
 373
 374         /* Required function calls to register the header fields and subtrees used */
 375         proto_register_field_array( proto_ax25_kiss, hf, array_length( hf ) );
 376         proto_register_subtree_array( ett, array_length( ett ) );
 377 }
 378
 379 void
 380 proto_reg_handoff_ax25_kiss(void)
 381 {
 382         dissector_add_uint( "wtap_encap", WTAP_ENCAP_AX25_KISS, kiss_handle );
 383
 384         /* only currently implemented for AX.25 */
 385         ax25_handle = find_dissector( "ax25" );
 386 }
 387