epan/dissectors/packet-pw-eth.c

   1 /* packet-pw-eth.c
   2  * Routines for ethernet PW dissection: it should conform to RFC 4448.
   3  *
   4  * Copyright 2008 _FF_
   5  *
   6  * Francesco Fondelli <francesco dot fondelli, gmail dot com>
   7  *
   8  * $Id$
   9  *
  10  * Wireshark - Network traffic analyzer
  11  * By Gerald Combs <gerald@wireshark.org>
  12  * Copyright 1998 Gerald Combs
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License
  16  * as published by the Free Software Foundation; either version 2
  17  * of the License, or (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; if not, write to the Free Software
  26  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  27  */
  28
  29 #include "config.h"
  30
  31 #include <glib.h>
  32
  33 #include <epan/packet.h>
  34 #include <epan/addr_resolv.h>
  35
  36 #include "packet-mpls.h"
  37
  38 static gint proto_pw_eth_cw = -1;
  39 static gint proto_pw_eth_nocw = -1;
  40 static gint proto_pw_eth_heuristic = -1;
  41
  42 static gint ett_pw_eth = -1;
  43
  44 static int hf_pw_eth = -1;
  45 static int hf_pw_eth_cw = -1;
  46 static int hf_pw_eth_cw_sequence_number = -1;
  47
  48 static dissector_handle_t eth_withoutfcs_handle;
  49 static dissector_handle_t pw_eth_handle_cw;
  50 static dissector_handle_t pw_eth_handle_nocw;
  51
  52 static void
  53 dissect_pw_eth_cw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
  54 {
  55     tvbuff_t *next_tvb;
  56     guint16   sequence_number;
  57
  58     if (tvb_reported_length_remaining(tvb, 0) < 4) {
  59         if (tree)
  60             proto_tree_add_text(tree, tvb, 0, -1,
  61                                 "Error processing Message");
  62         return;
  63     }
  64
  65     if (dissect_try_cw_first_nibble(tvb, pinfo, tree))
  66         return;
  67
  68     sequence_number = tvb_get_ntohs(tvb, 2);
  69
  70     if (tree) {
  71         proto_tree *pw_eth_tree;
  72         proto_item *ti;
  73
  74         ti = proto_tree_add_boolean(tree, hf_pw_eth_cw,
  75                                     tvb, 0, 0, TRUE);
  76         PROTO_ITEM_SET_HIDDEN(ti);
  77         ti = proto_tree_add_item(tree, proto_pw_eth_cw,
  78                                  tvb, 0, 4, ENC_NA);
  79         pw_eth_tree = proto_item_add_subtree(ti, ett_pw_eth);
  80
  81         proto_tree_add_uint_format(pw_eth_tree,
  82                                    hf_pw_eth_cw_sequence_number,
  83                                    tvb, 2, 2, sequence_number,
  84                                    "Sequence Number: %d",
  85                                    sequence_number);
  86     }
  87
  88     next_tvb = tvb_new_subset_remaining(tvb, 4);
  89     {
  90         /*
  91          * When Ethernet frames being decoded, pinfo->ethertype is extracted
  92          * from the top-level Ethernet frame. Dissection of Ethernet PW payload
  93          * overwrites this value as the same dissector is invoked again.
  94          * This may lead to undesired behavior (like disappearance of "Link"
  95          * tab from the "Decode as" menu).
  96          *
  97          * Let's save/restore ethertype. --ATA
  98          *
  99          * XXX it looks that more pinfo members (or even the whole pinfo)
 100          * XXX should be saved/restored in PW cases. Multilayer encapsulations,
 101          * XXX like ethernet/mpls/ethernet-pw/ip/vlan, may lead to undesired
 102          * XXX changes if pinfo->ipproto, ptype etc.
 103          */
 104         guint32 etype_save = pinfo->ethertype;
 105         call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
 106         pinfo->ethertype = etype_save;
 107     }
 108 }
 109
 110 static void
 111 dissect_pw_eth_nocw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 112 {
 113     tvbuff_t *next_tvb;
 114
 115     if (tree) {
 116         proto_item *ti;
 117         ti = proto_tree_add_boolean(tree, hf_pw_eth, tvb, 0, 0, TRUE);
 118         PROTO_ITEM_SET_HIDDEN(ti);
 119     }
 120
 121     next_tvb = tvb_new_subset_remaining(tvb, 0);
 122     {
 123         guint32 etype_save = pinfo->ethertype;
 124         call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
 125         pinfo->ethertype = etype_save;
 126     }
 127 }
 128
 129 /*
 130  * FF: this function returns TRUE if the first 12 bytes in tvb looks like
 131  *     two valid ethernet addresses.  FALSE otherwise.
 132  */
 133 static gboolean
 134 looks_like_plain_eth(tvbuff_t *tvb _U_)
 135 {
 136     const gchar *manuf_name_da;
 137     const gchar *manuf_name_sa;
 138
 139     if (tvb_reported_length_remaining(tvb, 0) < 14) {
 140         return FALSE;
 141     }
 142
 143     manuf_name_da = tvb_get_manuf_name_if_known(tvb, 0);
 144     manuf_name_sa = tvb_get_manuf_name_if_known(tvb, 6);
 145
 146     if (manuf_name_da && manuf_name_sa) {
 147         return TRUE;
 148     }
 149
 150     return FALSE;
 151 }
 152
 153 static void
 154 dissect_pw_eth_heuristic(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 155 {
 156     guint8 first_nibble = (tvb_get_guint8(tvb, 0) >> 4) & 0x0F;
 157
 158     if (looks_like_plain_eth(tvb))
 159         call_dissector(pw_eth_handle_nocw, tvb, pinfo, tree);
 160     else if (first_nibble == 0)
 161         call_dissector(pw_eth_handle_cw, tvb, pinfo, tree);
 162     else
 163         call_dissector(pw_eth_handle_nocw, tvb, pinfo, tree);
 164 }
 165
 166 void
 167 proto_register_pw_eth(void)
 168 {
 169     static hf_register_info hf[] = {
 170         {
 171             &hf_pw_eth,
 172             {
 173                 "PW (ethernet)",
 174                 "pweth", FT_BOOLEAN,
 175                 BASE_NONE, NULL, 0x0, NULL, HFILL
 176             }
 177         },
 178         {
 179             &hf_pw_eth_cw,
 180             {
 181                 "PW Control Word (ethernet)",
 182                 "pweth.cw", FT_BOOLEAN,
 183                 BASE_NONE, NULL, 0x0, NULL, HFILL
 184             }
 185         },
 186         {
 187             &hf_pw_eth_cw_sequence_number,
 188             {
 189                 "PW sequence number (ethernet)",
 190                 "pweth.cw.sequence_number", FT_UINT16,
 191                 BASE_DEC, NULL, 0x0, NULL, HFILL
 192             }
 193         }
 194     };
 195
 196     static gint *ett[] = {
 197         &ett_pw_eth
 198     };
 199
 200     proto_pw_eth_cw =
 201         proto_register_protocol("PW Ethernet Control Word",
 202                                 "Ethernet PW (with CW)",
 203                                 "pwethcw");
 204     proto_pw_eth_nocw =
 205         proto_register_protocol("Ethernet PW (no CW)", /* not displayed */
 206                                 "Ethernet PW (no CW)",
 207                                 "pwethnocw");
 208     proto_pw_eth_heuristic =
 209         proto_register_protocol("Ethernet PW (CW heuristic)", /* not disp. */
 210                                 "Ethernet PW (CW heuristic)",
 211                                 "pwethheuristic");
 212     proto_register_field_array(proto_pw_eth_cw, hf, array_length(hf));
 213     proto_register_subtree_array(ett, array_length(ett));
 214     register_dissector("pw_eth_cw", dissect_pw_eth_cw, proto_pw_eth_cw);
 215     register_dissector("pw_eth_nocw", dissect_pw_eth_nocw,
 216                        proto_pw_eth_nocw);
 217     register_dissector("pw_eth_heuristic", dissect_pw_eth_heuristic,
 218                        proto_pw_eth_heuristic);
 219 }
 220
 221 void
 222 proto_reg_handoff_pw_eth(void)
 223 {
 224     dissector_handle_t pw_eth_handle_heuristic;
 225
 226     eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
 227
 228     pw_eth_handle_cw = find_dissector("pw_eth_cw");
 229     dissector_add_uint("mpls.label", MPLS_LABEL_INVALID, pw_eth_handle_cw);
 230
 231     pw_eth_handle_nocw = find_dissector("pw_eth_nocw");
 232     dissector_add_uint("mpls.label", MPLS_LABEL_INVALID, pw_eth_handle_nocw);
 233
 234     pw_eth_handle_heuristic = find_dissector("pw_eth_heuristic");
 235     dissector_add_uint("mpls.label", MPLS_LABEL_INVALID, pw_eth_handle_heuristic);
 236 }
 237
 238 /*
 239  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 240  *
 241  * Local variables:
 242  * c-basic-offset: 4
 243  * tab-width: 8
 244  * indent-tabs-mode: nil
 245  * End:
 246  *
 247  * vi: set shiftwidth=4 tabstop=8 expandtab:
 248  * :indentSize=4:tabSize=8:noTabs=true:
 249  */