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  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-or-later
  10  *
  11  * History:
  12  * ---------------------------------
  13  * 18.03.2009 initial implementation
  14  * - FR DLCI mode
  15  * Not supported yet:
  16  * - Correct FR decode for encapsulations which contain fragmented FR frames.
  17  * - FR DLCI Martini (legacy) mode (i.e. legacy CW).
  18  */
  19
  20 #include "config.h"
  21
  22 #include <epan/packet.h>
  23 #include <epan/expert.h>
  24
  25 #include "packet-mpls.h"
  26
  27 void proto_register_pw_fr(void);
  28 void proto_reg_handoff_pw_fr(void);
  29
  30 static int proto_encaps;
  31 static int ett_encaps;
  32
  33 /* static int hf_pw_fr; */
  34 static int hf_cw_bits03;
  35 static int hf_cw_fecn;
  36 static int hf_cw_becn;
  37 static int hf_cw_de;
  38 static int hf_cw_cr;
  39 static int hf_cw_frg;
  40 static int hf_cw_len;
  41 static int hf_cw_seq;
  42 static int hf_cw_padding;
  43
  44 static expert_field ei_payload_size_invalid;
  45 static expert_field ei_cw_bits03;
  46 static expert_field ei_cw_packet_size_too_small;
  47
  48 static const value_string vals_frg[] = {
  49         { 0x0,  "Unfragmented" },
  50         { 0x1,  "First fragment" },
  51         { 0x2,  "Last fragment" },
  52         { 0x3,  "Intermediate fragment" },
  53         { 0,    NULL }
  54 };
  55
  56
  57 static dissector_handle_t fr_stripped_address_handle;
  58 static dissector_handle_t pw_fr_mpls_handle;
  59
  60 static int
  61 dissect_pw_fr( tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree, void* data _U_ )
  62 {
  63         int packet_size;
  64         int payload_size;
  65         int payload_padding;
  66         const int encaps_size = 4; /*encapsulation consists of mandatory CW only*/
  67         enum {
  68                 PQ_CW_BAD                      = 0x001
  69                 ,PQ_CW_BAD_BITS03              = 0x002
  70                 ,PQ_CW_BAD_LEN_GT_PACKET       = 0x004
  71                 ,PQ_CW_BAD_LEN_MUST_BE_ZERO    = 0x008
  72                 ,PQ_CW_BAD_LEN_MUST_BE_NONZERO = 0x010
  73                 ,PQ_PAYLOAD_SIZE_ZERO          = 0x020
  74         };
  75         int packet_quality;
  76
  77         packet_size = tvb_reported_length_remaining(tvb, 0);
  78         if (packet_size < encaps_size)
  79         {
  80                 {
  81                         proto_item  *item;
  82                         item = proto_tree_add_item(tree, proto_encaps, tvb, 0, -1, ENC_NA);
  83                         expert_add_info_format(pinfo, item, &ei_cw_packet_size_too_small,
  84                                 "PW packet (%d) is smaller than PW encapsulation header (%d)",
  85                                 (int)packet_size,(int)encaps_size);
  86                 }
  87                 col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
  88                 col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet < PW encapsulation header");
  89                 return 1;
  90         }
  91
  92         if (dissect_try_cw_first_nibble(tvb,pinfo,tree))
  93         {
  94                 return tvb_captured_length(tvb);
  95         }
  96
  97         /* check how "good" is this packet */
  98         /* also decide payload length from packet size and CW */
  99         packet_quality = 0;
 100         if (0 != (tvb_get_uint8(tvb, 0) & 0xf0 /*bits03*/))
 101         {
 102                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_BITS03;
 103         }
 104         {
 105                 /* RFC4619:
 106                  * [ If the frame's length (defined as the
 107                  * length of the layer 2 payload plus the length of the control word)
 108                  * is less than 64 octets, the length field MUST be set to the PW
 109                  * payload length.  Otherwise, the length field MUST be set to zero. ]
 110                  *
 111                  * Note difference from RFC4385 which states that:
 112                  * [..the length field MUST be set to the length of the PW payload
 113                  * *plus* the length of the *PWMCW*. ]
 114                  */
 115                 int cw_len;
 116                 int payload_size_packet; /*derived from packet size*/
 117
 118                 cw_len = tvb_get_uint8(tvb, 1) & 0x3f;
 119                 payload_size_packet = packet_size - encaps_size;
 120
 121                 /*
 122                  * Initial assumptions.
 123                  */
 124                 payload_size = payload_size_packet;
 125                 payload_padding = 0;
 126
 127                 if (payload_size_packet < 64)
 128                 {
 129                         int payload_size_cw; /*derived from cw*/
 130                         payload_size_cw = cw_len; /*RFC4619-specific*/
 131                         if (payload_size_cw == 0)
 132                         {
 133                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_NONZERO;
 134                         }
 135                         else if (payload_size_cw > payload_size_packet)
 136                         {
 137                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_GT_PACKET;
 138                         }
 139                         else /* ok */
 140                         {
 141                                 payload_size = payload_size_cw;
 142                                 payload_padding = payload_size_packet - payload_size_cw; /* >=0 */
 143                         }
 144                 }
 145                 else /* payload_size_packet >= 64 */
 146                 {
 147                         if (cw_len != 0)
 148                         {
 149                                 packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_ZERO;
 150                         }
 151                 }
 152         }
 153         if (payload_size == 0)
 154         {
 155                 packet_quality |= PQ_PAYLOAD_SIZE_ZERO;
 156         }
 157
 158         col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
 159         col_clear(pinfo->cinfo, COL_INFO);
 160         if (packet_quality & PQ_CW_BAD)
 161         {
 162                 col_set_str(pinfo->cinfo, COL_INFO, "CW:Malformed, ");
 163         }
 164         col_append_fstr(pinfo->cinfo, COL_INFO, "%d payload octets", (int)payload_size);
 165
 166         if (payload_padding != 0)
 167         {
 168                 col_append_fstr(pinfo->cinfo, COL_INFO, ", %d padding", (int)payload_padding);
 169         }
 170
 171         {
 172                 proto_tree* subtree;
 173                 proto_item* item_headline;
 174                 proto_item* item;
 175
 176                 item_headline = proto_tree_add_item(tree, proto_encaps, tvb, 0, 4, ENC_NA);
 177                 proto_item_append_text(item_headline, ": 0x%.8" PRIx32, tvb_get_ntohl(tvb, 0));
 178                 subtree = proto_item_add_subtree(item_headline, ett_encaps);
 179
 180                 if (packet_quality & PQ_CW_BAD_BITS03) /*display only if value is wrong*/
 181                 {
 182                         item = proto_tree_add_item(subtree, hf_cw_bits03, tvb, 0, 1, ENC_BIG_ENDIAN);
 183                         expert_add_info(pinfo, item, &ei_cw_bits03);
 184                 }
 185
 186                 proto_tree_add_item( subtree, hf_cw_fecn, tvb, 0, 1, ENC_BIG_ENDIAN );
 187                 proto_tree_add_item( subtree, hf_cw_becn, tvb, 0, 1, ENC_BIG_ENDIAN );
 188                 proto_tree_add_item( subtree, hf_cw_de,   tvb, 0, 1, ENC_BIG_ENDIAN );
 189                 proto_tree_add_item( subtree, hf_cw_cr,   tvb, 0, 1, ENC_BIG_ENDIAN );
 190                 proto_tree_add_item( subtree, hf_cw_frg,  tvb, 1, 1, ENC_BIG_ENDIAN );
 191
 192                 item = proto_tree_add_item( subtree, hf_cw_len, tvb, 1, 1, ENC_BIG_ENDIAN );
 193                 if (packet_quality & PQ_CW_BAD_LEN_GT_PACKET)
 194                 {
 195                         expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
 196                                 "Bad Length: greater than FR payload size (%d)",
 197                                 (int)payload_size);
 198                 }
 199                 if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_NONZERO)
 200                 {
 201                         expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
 202                                 "Bad Length: must be non-zero if FR PW packet size (%d) is < 64",
 203                                 (int)(payload_size+encaps_size));
 204                 }
 205                 if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_ZERO)
 206                 {
 207                         expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
 208                                 "Bad Length: must be 0 if FR PW packet size (%d) is >= 64",
 209                                 (int)(payload_size+encaps_size));
 210                 }
 211
 212                 proto_tree_add_item( subtree, hf_cw_seq, tvb, 2, 2, ENC_BIG_ENDIAN );
 213
 214                 if (payload_padding > 0)
 215                 {
 216                         proto_tree_add_item(subtree, hf_cw_padding, tvb,
 217                                 encaps_size+payload_size, payload_padding, ENC_NA);
 218                 }
 219
 220                 if (packet_quality & PQ_PAYLOAD_SIZE_ZERO)
 221                 {
 222                         expert_add_info_format(pinfo, item_headline, &ei_payload_size_invalid,
 223                                 "FR payload size must be non-zero");
 224                 }
 225
 226         }
 227         if (payload_size > 0)
 228         {
 229                 tvbuff_t *tvb_payload;
 230                 tvb_payload = tvb_new_subset_length(tvb, encaps_size, payload_size);
 231                 call_dissector( fr_stripped_address_handle, tvb_payload, pinfo, tree );
 232         }
 233         return tvb_captured_length(tvb);
 234 }
 235
 236
 237 void
 238 proto_register_pw_fr(void)
 239 {
 240 static hf_register_info hf[] = {
 241         {&hf_cw_bits03  ,{"Bits 0 to 3"         ,"pwfr.bits03"  ,FT_UINT8       ,BASE_HEX
 242                           ,NULL                 ,0xf0           ,NULL
 243                           ,HFILL }},
 244
 245         {&hf_cw_fecn    ,{"FR FECN"             ,"pwfr.fecn"    ,FT_UINT8       ,BASE_DEC
 246                           ,NULL                 ,0x08           ,"FR Forward Explicit Congestion Notification bit"
 247                           ,HFILL}},
 248
 249         {&hf_cw_becn    ,{"FR BECN"             ,"pwfr.becn"    ,FT_UINT8       ,BASE_DEC
 250                           ,NULL                 ,0x04           ,"FR Backward Explicit Congestion Notification bit"
 251                           ,HFILL}},
 252
 253         {&hf_cw_de      ,{"FR DE bit"           ,"pwfr.de"      ,FT_UINT8       ,BASE_DEC
 254                           ,NULL                 ,0x02           ,"FR Discard Eligibility bit"
 255                           ,HFILL}},
 256
 257         {&hf_cw_cr      ,{"FR Frame C/R"        ,"pwfr.cr"      ,FT_UINT8       ,BASE_DEC
 258                           ,NULL                 ,0x01           ,"FR frame Command/Response bit"
 259                           ,HFILL}},
 260
 261         {&hf_cw_frg     ,{"Fragmentation"       ,"pwfr.frag"    ,FT_UINT8       ,BASE_DEC
 262                           ,VALS(vals_frg)       ,0xc0           ,NULL
 263                           ,HFILL}},
 264
 265         {&hf_cw_len     ,{"Length"              ,"pwfr.length"  ,FT_UINT8       ,BASE_DEC
 266                           ,NULL                 ,0x3f           ,NULL
 267                           ,HFILL}},
 268
 269         {&hf_cw_seq     ,{"Sequence number"     ,"pwfr.seqno"   ,FT_UINT16      ,BASE_DEC
 270                           ,NULL                 ,0              ,NULL
 271                           ,HFILL}},
 272
 273         {&hf_cw_padding,{"Padding"      ,"pwfr.padding" ,FT_BYTES, BASE_NONE
 274                           ,NULL                 ,0              ,NULL
 275                           ,HFILL}}
 276 };
 277
 278         static int *ett[] = {
 279                 &ett_encaps
 280         };
 281
 282         static ei_register_info ei[] = {
 283                 { &ei_cw_packet_size_too_small, { "pwfr.packet_size_too_small", PI_MALFORMED, PI_ERROR, "PW packet is smaller than PW encapsulation header", EXPFILL }},
 284                 { &ei_cw_bits03, { "pwfr.cw.bits03.not_zero", PI_MALFORMED, PI_ERROR, "Bits 0..3 of Control Word must be 0", EXPFILL }},
 285                 { &ei_payload_size_invalid, { "pwfr.payload.size_invalid", PI_MALFORMED, PI_ERROR, "Bad Length: greater than FR payload size", EXPFILL }},
 286         };
 287         expert_module_t* expert_pwfr;
 288
 289         proto_encaps = proto_register_protocol( "PW Frame Relay DLCI Control Word",
 290                                                 "Frame Relay DLCI PW",
 291                                                 "pwfr");
 292         proto_register_field_array(proto_encaps, hf, array_length(hf));
 293         proto_register_subtree_array(ett, array_length(ett));
 294         expert_pwfr = expert_register_protocol(proto_encaps);
 295         expert_register_field_array(expert_pwfr, ei, array_length(ei));
 296         pw_fr_mpls_handle = register_dissector("pw_fr", dissect_pw_fr, proto_encaps );
 297 }
 298
 299
 300 void
 301 proto_reg_handoff_pw_fr(void)
 302 {
 303         dissector_add_for_decode_as("mpls.label", pw_fr_mpls_handle);
 304         dissector_add_for_decode_as("mpls.pfn", pw_fr_mpls_handle);
 305         fr_stripped_address_handle = find_dissector_add_dependency("fr_stripped_address", proto_encaps);
 306 }
 307
 308 /*
 309  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 310  *
 311  * Local variables:
 312  * c-basic-offset: 8
 313  * tab-width: 8
 314  * indent-tabs-mode: t
 315  * End:
 316  *
 317  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 318  * :indentSize=8:tabSize=8:noTabs=false:
 319  */