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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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 #include "config.h"
  35
  36 #include <glib.h>
  37 #include <epan/packet.h>
  38 #include <epan/expert.h>
  39
  40 #include "packet-mpls.h"
  41
  42 static gint proto_encaps = -1;
  43 static gint ett_encaps = -1;
  44
  45 /* static int hf_pw_fr = -1; */
  46 static int hf_cw_bits03 = -1;
  47 static int hf_cw_fecn = -1;
  48 static int hf_cw_becn = -1;
  49 static int hf_cw_de = -1;
  50 static int hf_cw_cr = -1;
  51 static int hf_cw_frg = -1;
  52 static int hf_cw_len = -1;
  53 static int hf_cw_seq = -1;
  54
  55 static expert_field ei_payload_size_invalid = EI_INIT;
  56 static expert_field ei_cw_bits03 = EI_INIT;
  57 static expert_field ei_cw_packet_size_too_small = EI_INIT;
  58
  59 static const value_string vals_frg[] = {
  60         { 0x0,  "Unfragmented" },
  61         { 0x1,  "First fragment" },
  62         { 0x2,  "Last fragment" },
  63         { 0x3,  "Intermediate fragment" },
  64         { 0,    NULL }
  65 };
  66
  67
  68 static dissector_handle_t fr_stripped_address_handle;
  69
  70
  71 static void
  72 dissect_pw_fr( tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree )
  73 {
  74         gint packet_size;
  75         gint payload_size;
  76         gint payload_padding;
  77         const int encaps_size = 4; /*encapsulation consists of mandatory CW only*/
  78         enum {
  79                 PQ_CW_BAD                      = 0x001
  80                 ,PQ_CW_BAD_BITS03              = 0x002
  81                 ,PQ_CW_BAD_LEN_GT_PACKET       = 0x004
  82                 ,PQ_CW_BAD_LEN_MUST_BE_ZERO    = 0x008
  83                 ,PQ_CW_BAD_LEN_MUST_BE_NONZERO = 0x010
  84                 ,PQ_PAYLOAD_SIZE_ZERO          = 0x020
  85         };
  86         int packet_quality;
  87
  88         packet_size = tvb_reported_length_remaining(tvb, 0);
  89         if (packet_size < encaps_size)
  90         {
  91                 {
  92                         proto_item  *item;
  93                         item = proto_tree_add_item(tree, proto_encaps, tvb, 0, -1, ENC_NA);
  94                         expert_add_info_format(pinfo, item, &ei_cw_packet_size_too_small,
  95                                 "PW packet (%d) is smaller than PW encapsulation header (%d)",
  96                                 (int)packet_size,(int)encaps_size);
  97                 }
  98                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
  99                 col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet < PW encapsulation header");
 100                 return;
 101         }
 102
 103         if (dissect_try_cw_first_nibble(tvb,pinfo,tree))
 104         {
 105                 return;
 106         }
 107
 108         /* check how "good" is this packet */
 109         /* also decide payload length from packet size and CW */
 110         packet_quality = 0;
 111         if (0 != (tvb_get_guint8(tvb, 0) & 0xf0 /*bits03*/))
 112         {
 113                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_BITS03;
 114         }
 115         {
 116                 /* RFC4619:
 117                  * [ If the frame's length (defined as the
 118                  * length of the layer 2 payload plus the length of the control word)
 119                  * is less than 64 octets, the length field MUST be set to the PW
 120                  * payload length.  Otherwise, the length field MUST be set to zero. ]
 121                  *
 122                  * Note difference from RFC4385 which states that:
 123                  * [..the length field MUST be set to the length of the PW payload
 124                  * *plus* the length of the *PWMCW*. ]
 125                  */
 126                 int cw_len;
 127                 gint payload_size_packet; /*derived from packet size*/
 128
 129                 cw_len = tvb_get_guint8(tvb, 1) & 0x3f;
 130                 payload_size_packet = packet_size - encaps_size;
 131
 132                 /*
 133                  * Initial assumptions.
 134                  */
 135                 payload_size = payload_size_packet;
 136                 payload_padding = 0;
 137
 138                 if (payload_size_packet < 64)
 139                 {
 140                         gint payload_size_cw; /*derived from cw*/
 141                         payload_size_cw = cw_len; /*RFC4619-specific*/
 142                         if (payload_size_cw == 0)
 143                         {
 144                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_NONZERO;
 145                         }
 146                         else if (payload_size_cw > payload_size_packet)
 147                         {
 148                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_GT_PACKET;
 149                         }
 150                         else /* ok */
 151                         {
 152                                 payload_size = payload_size_cw;
 153                                 payload_padding = payload_size_packet - payload_size_cw; /* >=0 */
 154                         }
 155                 }
 156                 else /* payload_size_packet >= 64 */
 157                 {
 158                         if (cw_len != 0)
 159                         {
 160                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_ZERO;
 161                         }
 162                 }
 163         }
 164         if (payload_size == 0)
 165         {
 166                 packet_quality |= PQ_PAYLOAD_SIZE_ZERO;
 167         }
 168
 169         col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
 170         col_clear(pinfo->cinfo, COL_INFO);
 171         if (packet_quality & PQ_CW_BAD)
 172         {
 173                 col_set_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                 proto_tree* subtree;
 184                 proto_item* item_headline;
 185                 proto_item* item;
 186
 187                 item_headline = proto_tree_add_item(tree, proto_encaps, tvb, 0, 4, ENC_NA);
 188                 proto_item_append_text(item_headline, ": 0x%.8" G_GINT32_MODIFIER "x", tvb_get_ntohl(tvb, 0));
 189                 subtree = proto_item_add_subtree(item_headline, ett_encaps);
 190
 191                 if (packet_quality & PQ_CW_BAD_BITS03) /*display only if value is wrong*/
 192                 {
 193                         item = proto_tree_add_item(subtree, hf_cw_bits03, tvb, 0, 1, ENC_BIG_ENDIAN);
 194                         expert_add_info(pinfo, item, &ei_cw_bits03);
 195                 }
 196
 197                 (void)proto_tree_add_item( subtree, hf_cw_fecn, tvb, 0, 1, ENC_BIG_ENDIAN );
 198                 (void)proto_tree_add_item( subtree, hf_cw_becn, tvb, 0, 1, ENC_BIG_ENDIAN );
 199                 (void)proto_tree_add_item( subtree, hf_cw_de,   tvb, 0, 1, ENC_BIG_ENDIAN );
 200                 (void)proto_tree_add_item( subtree, hf_cw_cr,   tvb, 0, 1, ENC_BIG_ENDIAN );
 201                 (void)proto_tree_add_item( subtree, hf_cw_frg,  tvb, 1, 1, ENC_BIG_ENDIAN );
 202
 203                 item = proto_tree_add_item( subtree, hf_cw_len, tvb, 1, 1, ENC_BIG_ENDIAN );
 204                 if (packet_quality & PQ_CW_BAD_LEN_GT_PACKET)
 205                 {
 206                         expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
 207                                 "Bad Length: greater than FR payload size (%d)",
 208                                 (int)payload_size);
 209                 }
 210                 if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_NONZERO)
 211                 {
 212                         expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
 213                                 "Bad Length: must be non-zero if FR PW packet size (%d) is < 64",
 214                                 (int)(payload_size+encaps_size));
 215                 }
 216                 if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_ZERO)
 217                 {
 218                         expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
 219                                 "Bad Length: must be 0 if FR PW packet size (%d) is >= 64",
 220                                 (int)(payload_size+encaps_size));
 221                 }
 222
 223                 proto_tree_add_item( subtree, hf_cw_seq, tvb, 2, 2, ENC_BIG_ENDIAN );
 224
 225                 if (payload_padding > 0)
 226                 {
 227                         proto_tree_add_text(subtree, tvb,
 228                                 encaps_size+payload_size, payload_padding,
 229                                 "[Padding: %d octets]",(int)payload_padding);
 230                 }
 231
 232                 if (packet_quality & PQ_PAYLOAD_SIZE_ZERO)
 233                 {
 234                         expert_add_info_format(pinfo, item_headline, &ei_payload_size_invalid,
 235                                 "FR payload size must be non-zero");
 236                 }
 237
 238         }
 239         if (payload_size > 0)
 240         {
 241                 tvbuff_t *tvb_payload;
 242                 tvb_payload = tvb_new_subset(tvb, encaps_size, payload_size, payload_size);
 243                 call_dissector( fr_stripped_address_handle, tvb_payload, pinfo, tree );
 244         }
 245         return;
 246 }
 247
 248
 249 void
 250 proto_register_pw_fr(void)
 251 {
 252 static hf_register_info hf[] = {
 253         {&hf_cw_bits03  ,{"Bits 0 to 3"         ,"pwfr.bits03"  ,FT_UINT8       ,BASE_HEX
 254                           ,NULL                 ,0xf0           ,NULL
 255                           ,HFILL }},
 256
 257         {&hf_cw_fecn    ,{"FR FECN"             ,"pwfr.fecn"    ,FT_UINT8       ,BASE_DEC
 258                           ,NULL                 ,0x08           ,"FR Forward Explicit Congestion Notification bit"
 259                           ,HFILL}},
 260
 261         {&hf_cw_becn    ,{"FR BECN"             ,"pwfr.becn"    ,FT_UINT8       ,BASE_DEC
 262                           ,NULL                 ,0x04           ,"FR Backward Explicit Congestion Notification bit"
 263                           ,HFILL}},
 264
 265         {&hf_cw_de      ,{"FR DE bit"           ,"pwfr.de"      ,FT_UINT8       ,BASE_DEC
 266                           ,NULL                 ,0x02           ,"FR Discard Eligibility bit"
 267                           ,HFILL}},
 268
 269         {&hf_cw_cr      ,{"FR Frame C/R"        ,"pwfr.cr"      ,FT_UINT8       ,BASE_DEC
 270                           ,NULL                 ,0x01           ,"FR frame Command/Response bit"
 271                           ,HFILL}},
 272
 273         {&hf_cw_frg     ,{"Fragmentation"       ,"pwfr.frag"    ,FT_UINT8       ,BASE_DEC
 274                           ,vals_frg             ,0xc0           ,NULL
 275                           ,HFILL}},
 276
 277         {&hf_cw_len     ,{"Length"              ,"pwfr.length"  ,FT_UINT8       ,BASE_DEC
 278                           ,NULL                 ,0x3f           ,NULL
 279                           ,HFILL}},
 280
 281         {&hf_cw_seq     ,{"Sequence number"     ,"pwfr.length"  ,FT_UINT16      ,BASE_DEC
 282                           ,NULL                 ,0              ,NULL
 283                           ,HFILL}}
 284 };
 285
 286         static gint *ett[] = {
 287                 &ett_encaps
 288         };
 289
 290         static ei_register_info ei[] = {
 291                 { &ei_cw_packet_size_too_small, { "pwfr.packet_size_too_small", PI_MALFORMED, PI_ERROR, "PW packet is smaller than PW encapsulation header", EXPFILL }},
 292                 { &ei_cw_bits03, { "pwfr.cw.bits03.not_zero", PI_MALFORMED, PI_ERROR, "Bits 0..3 of Control Word must be 0", EXPFILL }},
 293                 { &ei_payload_size_invalid, { "pwfr.payload.size_invalid", PI_MALFORMED, PI_ERROR, "Bad Length: greater than FR payload size", EXPFILL }},
 294         };
 295         expert_module_t* expert_pwfr;
 296
 297         proto_encaps = proto_register_protocol( "PW Frame Relay DLCI Control Word",
 298                                                 "Frame Relay DLCI PW",
 299                                                 "pwfr");
 300         proto_register_field_array(proto_encaps, hf, array_length(hf));
 301         proto_register_subtree_array(ett, array_length(ett));
 302         expert_pwfr = expert_register_protocol(proto_encaps);
 303         expert_register_field_array(expert_pwfr, ei, array_length(ei));
 304         register_dissector("pw_fr", dissect_pw_fr, proto_encaps );
 305 }
 306
 307
 308 void
 309 proto_reg_handoff_pw_fr(void)
 310 {
 311         dissector_handle_t h;
 312         h = find_dissector("pw_fr");
 313         dissector_add_uint("mpls.label", MPLS_LABEL_INVALID, h);
 314         fr_stripped_address_handle = find_dissector("fr_stripped_address");
 315 }