epan/dissectors/packet-pw-fr.c

   1 /* packet-pw-fr.c
   2  * Routines for Frame Relay MPLS PW dissection as per RFC4619.
   3  * Copyright 2009, Dmitry Trebich, Artem Tamazov <artem.tamazov@tellabs.com>
   4  *
   5  * $Id$
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  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  * History:
  26  * ---------------------------------
  27  * 18.03.2009 initial implementation
  28  * - FR DLCI mode
  29  * Not supported yet:
  30  * - Correct FR decode for encapsulations which contain fragmented FR frames.
  31  * - FR DLCI Martini (legacy) mode (i.e. legacy CW).
  32  */
  33
  34 #ifdef HAVE_CONFIG_H
  35 # include "config.h"
  36 #endif
  37
  38 #include <glib.h>
  39 #include <epan/packet.h>
  40 #include <epan/expert.h>
  41
  42 #include "packet-mpls.h"
  43
  44 static gint proto_encaps = -1;
  45 static gint ett_encaps = -1;
  46
  47 /*static int hf_pw_fr = -1;*/
  48 static int hf_cw_bits03 = -1;
  49 static int hf_cw_fecn = -1;
  50 static int hf_cw_becn = -1;
  51 static int hf_cw_de = -1;
  52 static int hf_cw_cr = -1;
  53 static int hf_cw_frg = -1;
  54 static int hf_cw_len = -1;
  55 static int hf_cw_seq = -1;
  56
  57 static const value_string vals_frg[] = {
  58         { 0x0,  "Unfragmented" },
  59         { 0x1,  "First fragment" },
  60         { 0x2,  "Last fragment" },
  61         { 0x3,  "Intermediate fragment" },
  62         { 0,    NULL }
  63 };
  64
  65
  66 static dissector_handle_t fr_stripped_address_handle;
  67
  68
  69 static void
  70 dissect_pw_fr( tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree )
  71 {
  72         gint packet_size;
  73         gint payload_size;
  74         gint payload_padding;
  75         const int encaps_size = 4; /*encapsulation consists of mandatory CW only*/
  76         enum {
  77                 PQ_CW_BAD                               = 0x001
  78                     ,PQ_CW_BAD_BITS03                   = 0x002
  79                     ,PQ_CW_BAD_LEN_GT_PACKET            = 0x004
  80                     ,PQ_CW_BAD_LEN_MUST_BE_ZERO         = 0x008
  81                     ,PQ_CW_BAD_LEN_MUST_BE_NONZERO      = 0x010
  82                 ,PQ_PAYLOAD_SIZE_ZERO                   = 0x020
  83         } packet_quality;
  84
  85         packet_size = tvb_reported_length_remaining(tvb, 0);
  86         if (packet_size < encaps_size)
  87         {
  88                 if (tree)
  89                 {
  90                         proto_item  *item;
  91                         item = proto_tree_add_item(tree, proto_encaps, tvb, 0, -1, FALSE);
  92                         expert_add_info_format(pinfo, item, PI_MALFORMED, PI_ERROR,
  93                                 "PW packet (%d) is smaller than PW encapsulation header (%d)"
  94                                 ,(int)packet_size,(int)encaps_size);
  95                 }
  96                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
  97                 col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet < PW encapsulation header");
  98                 return;
  99         }
 100
 101         if (dissect_try_cw_first_nibble(tvb,pinfo,tree))
 102         {
 103                 return;
 104         }
 105
 106         /* check how "good" is this packet */
 107         /* also decide payload length from packet size and CW */
 108         packet_quality = 0;
 109         if (0 != (tvb_get_guint8(tvb, 0) & 0xf0 /*bits03*/))
 110         {
 111                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_BITS03;
 112         }
 113         {
 114                 /* RFC4619:
 115                  * [ If the frame's length (defined as the
 116                  * length of the layer 2 payload plus the length of the control word)
 117                  * is less than 64 octets, the length field MUST be set to the PW
 118                  * payload length.  Otherwise, the length field MUST be set to zero. ]
 119                  *
 120                  * Note difference from RFC4385 which states that:
 121                  * [..the length field MUST be set to the length of the PW payload
 122                  * *plus* the length of the *PWMCW*. ]
 123                  */
 124                 int cw_len;
 125                 gint payload_size_packet; /*derived from packet size*/
 126
 127                 cw_len = tvb_get_guint8(tvb, 1) & 0x3f;
 128                 payload_size_packet = packet_size - encaps_size;
 129
 130                 /*
 131                  * Initial assumptions.
 132                  */
 133                 payload_size = payload_size_packet;
 134                 payload_padding = 0;
 135
 136                 if (payload_size_packet < 64)
 137                 {
 138                         gint payload_size_cw; /*derived from cw*/
 139                         payload_size_cw = cw_len; /*RFC4619-specific*/
 140                         if (payload_size_cw == 0)
 141                         {
 142                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_NONZERO;
 143                         }
 144                         else if (payload_size_cw > payload_size_packet)
 145                         {
 146                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_GT_PACKET;
 147                         }
 148                         else /* ok */
 149                         {
 150                                 payload_size = payload_size_cw;
 151                                 payload_padding = payload_size_packet - payload_size_cw; /* >=0 */
 152                         }
 153                 }
 154                 else /* payload_size_packet >= 64 */
 155                 {
 156                         if (cw_len != 0)
 157                         {
 158                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_ZERO;
 159                         }
 160                 }
 161         }
 162         if ((payload_size == 0))
 163         {
 164                 packet_quality |= PQ_PAYLOAD_SIZE_ZERO;
 165         }
 166
 167         col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
 168         if (check_col(pinfo->cinfo, COL_INFO))
 169         {
 170                 col_clear(pinfo->cinfo, COL_INFO);
 171                 if (packet_quality & PQ_CW_BAD)
 172                 {
 173                         col_append_str(pinfo->cinfo, COL_INFO, "CW:Malformed, ");
 174                 }
 175                 col_append_fstr(pinfo->cinfo, COL_INFO, "%d payload octets", (int)payload_size);
 176
 177                 if (payload_padding != 0)
 178                 {
 179                         col_append_fstr(pinfo->cinfo, COL_INFO, ", %d padding", (int)payload_padding);
 180                 }
 181         }
 182
 183         if (tree)
 184         {
 185                 proto_tree* subtree;
 186                 proto_item* item_headline;
 187                 proto_item* item;
 188
 189                 item_headline = proto_tree_add_item(tree, proto_encaps, tvb, 0, 4, FALSE);
 190                 proto_item_append_text(item_headline, ": 0x%.8" G_GINT32_MODIFIER "x", tvb_get_ntohl(tvb, 0));
 191                 subtree = proto_item_add_subtree(item_headline, ett_encaps);
 192
 193                 if (packet_quality & PQ_CW_BAD_BITS03) /*display only if value is wrong*/
 194                 {
 195                         item = proto_tree_add_item(subtree, hf_cw_bits03, tvb, 0, 1, FALSE);
 196                         expert_add_info_format(pinfo, item, PI_MALFORMED, PI_ERROR,
 197                                 "Bits 0..3 of Control Word must be 0");
 198                 }
 199
 200                 (void)proto_tree_add_item( subtree, hf_cw_fecn, tvb, 0, 1, FALSE );
 201                 (void)proto_tree_add_item( subtree, hf_cw_becn, tvb, 0, 1, FALSE );
 202                 (void)proto_tree_add_item( subtree, hf_cw_de, tvb, 0, 1, FALSE );
 203                 (void)proto_tree_add_item( subtree, hf_cw_cr, tvb, 0, 1, FALSE );
 204                 (void)proto_tree_add_item( subtree, hf_cw_frg, tvb, 1, 1, FALSE );
 205
 206                 item = proto_tree_add_item( subtree, hf_cw_len, tvb, 1, 1, FALSE );
 207                 if (packet_quality & PQ_CW_BAD_LEN_GT_PACKET)
 208                 {
 209                         expert_add_info_format(pinfo, item, PI_MALFORMED, PI_ERROR,
 210                                 "Bad Length: greater than FR payload size (%d)",
 211                                 (int)payload_size);
 212                 }
 213                 if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_NONZERO)
 214                 {
 215                         expert_add_info_format(pinfo, item, PI_MALFORMED, PI_ERROR,
 216                                 "Bad Length: must be non-zero if FR PW packet size (%d) is < 64",
 217                                 (int)(payload_size+encaps_size));
 218                 }
 219                 if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_ZERO)
 220                 {
 221                         expert_add_info_format(pinfo, item, PI_MALFORMED, PI_ERROR,
 222                                 "Bad Length: must be 0 if FR PW packet size (%d) is >= 64",
 223                                 (int)(payload_size+encaps_size));
 224                 }
 225
 226                 proto_tree_add_item( subtree, hf_cw_seq, tvb, 2, 2, FALSE );
 227
 228                 if (payload_padding > 0)
 229                 {
 230                         proto_tree_add_text(subtree, tvb,
 231                                 encaps_size+payload_size, payload_padding,
 232                                 "[Padding: %d octets]",(int)payload_padding);
 233                 }
 234
 235                 if (packet_quality & PQ_PAYLOAD_SIZE_ZERO)
 236                 {
 237                         expert_add_info_format(pinfo, item_headline, PI_MALFORMED, PI_WARN,
 238                                 "FR payload size must be non-zero");
 239                 }
 240
 241         }
 242         if (payload_size > 0)
 243         {
 244                 tvbuff_t *tvb_payload;
 245                 tvb_payload = tvb_new_subset(tvb, encaps_size, payload_size, payload_size);
 246                 call_dissector( fr_stripped_address_handle, tvb_payload, pinfo, tree );
 247         }
 248         return;
 249 }
 250
 251
 252 void
 253 proto_register_pw_fr(void)
 254 {
 255         static hf_register_info hf[] = {
 256                 {&hf_cw_bits03  ,{"Bits 0 to 3"         ,"pwfr.bits03"  ,FT_UINT8       ,BASE_HEX
 257                                   ,NULL                 ,0xf0           ,NULL
 258                                   ,HFILL }}
 259                 ,{&hf_cw_fecn   ,{"FR FECN"             ,"pwfr.fecn"    ,FT_UINT8       ,BASE_DEC
 260                                   ,NULL                 ,0x08           ,"FR Forward Explicit Congestion Notification bit"
 261                                   ,HFILL}}
 262                 ,{&hf_cw_becn   ,{"FR BECN"             ,"pwfr.becn"    ,FT_UINT8       ,BASE_DEC
 263                                   ,NULL                 ,0x04           ,"FR Backward Explicit Congestion Notification bit"
 264                                   ,HFILL}}
 265                 ,{&hf_cw_de     ,{"FR DE bit"           ,"pwfr.de"      ,FT_UINT8       ,BASE_DEC
 266                                   ,NULL                 ,0x02           ,"FR Discard Eligibility bit"
 267                                   ,HFILL}}
 268                 ,{&hf_cw_cr     ,{"FR Frame C/R"        ,"pwfr.cr"      ,FT_UINT8       ,BASE_DEC
 269                                   ,NULL                 ,0x01           ,"FR frame Command/Response bit"
 270                                   ,HFILL}}
 271                 ,{&hf_cw_frg    ,{"Fragmentation"       ,"pwfr.frag"    ,FT_UINT8       ,BASE_DEC
 272                                   ,vals_frg             ,0xc0           ,NULL
 273                                   ,HFILL}}
 274                 ,{&hf_cw_len    ,{"Length"              ,"pwfr.length"  ,FT_UINT8       ,BASE_DEC
 275                                   ,NULL                 ,0x3f           ,NULL
 276                                   ,HFILL}}
 277                 ,{&hf_cw_seq    ,{"Sequence number"     ,"pwfr.length"  ,FT_UINT16      ,BASE_DEC
 278                                   ,NULL                 ,0              ,NULL
 279                                   ,HFILL}}
 280         };
 281
 282         static gint *ett[] = {
 283                 &ett_encaps
 284         };
 285
 286         proto_encaps = proto_register_protocol( "PW Frame Relay DLCI Control Word",
 287                                                 "Frame Relay DLCI PW",
 288                                                 "pwfr");
 289         proto_register_field_array(proto_encaps, hf, array_length(hf));
 290         proto_register_subtree_array(ett, array_length(ett));
 291         register_dissector("pw_fr", dissect_pw_fr, proto_encaps );
 292 }
 293
 294
 295 void
 296 proto_reg_handoff_pw_fr(void)
 297 {
 298         dissector_handle_t h;
 299         h = find_dissector("pw_fr");
 300         dissector_add("mpls.label", LABEL_INVALID, h);
 301         fr_stripped_address_handle = find_dissector("fr_stripped_address");
 302 }