packet-gre.c

   1 /* packet-gre.c
   2  * Routines for the Generic Routing Encapsulation (GRE) protocol
   3  * Brad Robel-Forrest <brad.robel-forrest@watchguard.com>
   4  *
   5  * $Id: packet-gre.c,v 1.11 1999/12/10 21:27:13 guy Exp $
   6  *
   7  * Ethereal - Network traffic analyzer
   8  * By Gerald Combs <gerald@unicom.net>
   9  * Copyright 1998 Gerald Combs
  10  *
  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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  25  */
  26
  27 #ifdef HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #ifdef HAVE_SYS_TYPES_H
  32 # include <sys/types.h>
  33 #endif
  34
  35 #ifdef HAVE_NETINET_IN_H
  36 #include <netinet/in.h>
  37 #endif
  38 #include <glib.h>
  39 #include "packet.h"
  40
  41 static int proto_gre = -1;
  42
  43 static gint ett_gre = -1;
  44 static gint ett_gre_flags = -1;
  45
  46 /* bit positions for flags in header */
  47 #define GH_B_C          0x8000
  48 #define GH_B_R          0x4000
  49 #define GH_B_K          0x2000
  50 #define GH_B_S          0x1000
  51 #define GH_B_s          0x0800
  52 #define GH_B_RECUR      0x0700
  53 #define GH_P_A          0x0080  /* only in special PPTPized GRE header */
  54 #define GH_P_FLAGS      0x0078  /* only in special PPTPized GRE header */
  55 #define GH_R_FLAGS      0x00F8
  56 #define GH_B_VER        0x0007
  57
  58 #define GRE_PPP         0x880B
  59 #define GRE_IP          0x0800
  60
  61 static int calc_len(guint16, int);
  62 static void add_flags_and_ver(proto_tree *, guint16, int, int);
  63
  64 void
  65 dissect_gre(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
  66
  67   guint16       flags_and_ver = pntohs(pd + offset);
  68   guint16       type          = pntohs(pd + offset + sizeof(flags_and_ver));
  69   static const value_string typevals[] = {
  70     { GRE_PPP, "PPP" },
  71     { GRE_IP,  "IP" },
  72     { 0,       NULL  }
  73   };
  74   guint16       sre_af;
  75   guint8        sre_length;
  76
  77   if (check_col(fd, COL_PROTOCOL))
  78     col_add_str(fd, COL_PROTOCOL, "GRE");
  79
  80   if (check_col(fd, COL_INFO)) {
  81     col_add_fstr(fd, COL_INFO, "Encapsulated %s",
  82         val_to_str(type, typevals, "0x%04X (unknown)"));
  83   }
  84
  85   if (IS_DATA_IN_FRAME(offset) && tree) {
  86     gboolean            is_ppp;
  87     proto_item *        ti;
  88     proto_tree *        gre_tree;
  89
  90     is_ppp = (type == GRE_PPP);
  91
  92     ti = proto_tree_add_item_format(tree, proto_gre, offset,
  93       calc_len(flags_and_ver, type), NULL,
  94       "Generic Routing Encapsulation (%s)",
  95       val_to_str(type, typevals, "0x%04X - unknown"));
  96     gre_tree = proto_item_add_subtree(ti, ett_gre);
  97     add_flags_and_ver(gre_tree, flags_and_ver, offset, is_ppp);
  98
  99     offset += sizeof(flags_and_ver);
 100
 101     proto_tree_add_text(gre_tree, offset, sizeof(type),
 102                         "Protocol Type: %s (%#04x)",
 103                         val_to_str(type, typevals, "Unknown"), type);
 104     offset += sizeof(type);
 105
 106     if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
 107       guint16 checksum = pntohs(pd + offset);
 108       proto_tree_add_text(gre_tree, offset, sizeof(checksum),
 109                           "Checksum: %u", checksum);
 110       offset += sizeof(checksum);
 111     }
 112
 113     if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
 114       guint16 rtoffset = pntohs(pd + offset);
 115       proto_tree_add_text(gre_tree, offset, sizeof(rtoffset),
 116                           "Offset: %u", rtoffset);
 117       offset += sizeof(rtoffset);
 118     }
 119
 120     if (flags_and_ver & GH_B_K) {
 121       if (is_ppp) {
 122         guint16 paylen;
 123         guint16 callid;
 124
 125         paylen = pntohs(pd + offset);
 126         proto_tree_add_text(gre_tree, offset, sizeof(paylen),
 127                             "Payload length: %u", paylen);
 128         offset += sizeof(paylen);
 129
 130         callid = pntohs(pd + offset);
 131         proto_tree_add_text(gre_tree, offset, sizeof(callid),
 132                             "Call ID: %u", callid);
 133         offset += sizeof(callid);
 134       }
 135       else {
 136         guint32 key = pntohl(pd + offset);
 137         proto_tree_add_text(gre_tree, offset, sizeof(key),
 138                             "Key: %u", key);
 139         offset += sizeof(key);
 140       }
 141     }
 142
 143     if (flags_and_ver & GH_B_S) {
 144       guint32 seqnum = pntohl(pd + offset);
 145       proto_tree_add_text(gre_tree, offset, sizeof(seqnum),
 146                           "Sequence number: %u", seqnum);
 147       offset += sizeof(seqnum);
 148     }
 149
 150     if (is_ppp && flags_and_ver & GH_P_A) {
 151       guint32 acknum = pntohl(pd + offset);
 152       proto_tree_add_text(gre_tree, offset, sizeof(acknum),
 153                           "Acknowledgement number: %u", acknum);
 154       offset += sizeof(acknum);
 155     }
 156
 157     if (flags_and_ver & GH_B_R) {
 158       for (;;) {
 159         sre_af = pntohs(pd + offset);
 160         proto_tree_add_text(gre_tree, offset, sizeof(guint16),
 161                           "Address family: %u", sre_af);
 162         offset += sizeof(guint16);
 163         proto_tree_add_text(gre_tree, offset, 1,
 164                           "SRE offset: %u", pd[offset++]);
 165         sre_length = pd[offset];
 166         proto_tree_add_text(gre_tree, offset, sizeof(guint8),
 167                           "SRE length: %u", sre_length);
 168         offset += sizeof(guint8);
 169         if (sre_af == 0 && sre_length == 0)
 170           break;
 171         offset += sre_length;
 172       }
 173     }
 174
 175     switch (type) {
 176       case GRE_PPP:
 177         dissect_payload_ppp(pd, offset, fd, tree);
 178         break;
 179       case GRE_IP:
 180         dissect_ip(pd, offset, fd, tree);
 181         break;
 182       default:
 183         dissect_data(pd, offset, fd, gre_tree);
 184     }
 185   }
 186 }
 187
 188 static int
 189 calc_len(guint16 flags_and_ver, int type)
 190 {
 191   int   len = 4;
 192
 193   if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R)
 194     len += 4;
 195   if (flags_and_ver & GH_B_K)
 196     len += 4;
 197   if (flags_and_ver & GH_B_S)
 198     len += 4;
 199   switch (type) {
 200
 201   case GRE_PPP:
 202     if (flags_and_ver & GH_P_A)
 203       len += 4;
 204     break;
 205   }
 206
 207   return len;
 208 }
 209
 210 static void
 211 add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, int offset, int is_ppp) {
 212
 213   proto_item *  ti;
 214   proto_tree *  fv_tree;
 215   int           nbits = sizeof(flags_and_ver) * 8;
 216
 217   ti = proto_tree_add_text(tree, offset, 2,
 218                            "Flags and version: %#04x", flags_and_ver);
 219   fv_tree = proto_item_add_subtree(ti, ett_gre_flags);
 220
 221   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 222                       decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
 223                                               "Checksum", "No checksum"));
 224   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 225                       decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
 226                                               "Routing", "No routing"));
 227   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 228                       decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
 229                                               "Key", "No key"));
 230   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 231                       decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
 232                                               "Sequence number", "No sequence number"));
 233   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 234                       decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
 235                                               "Strict source route", "No strict source route"));
 236   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 237                       decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
 238                                               "Recursion control: %u"));
 239   if (is_ppp) {
 240     proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 241                         decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
 242                                                 "Acknowledgment number", "No acknowledgment number"));
 243     proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 244                         decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
 245                                                 "Flags: %u"));
 246   }
 247   else {
 248     proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 249                         decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
 250                                                 "Flags: %u"));
 251   }
 252
 253   proto_tree_add_text(fv_tree, offset, sizeof(flags_and_ver), "%s",
 254                       decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
 255                                               "Version: %u"));
 256  }
 257
 258 void
 259 proto_register_gre(void)
 260 {
 261 /*        static hf_register_info hf[] = {
 262                 { &variable,
 263                 { "Name",           "gre.abbreviation", TYPE, VALS_POINTER }},
 264         };*/
 265         static gint *ett[] = {
 266                 &ett_gre,
 267                 &ett_gre_flags,
 268         };
 269
 270         proto_gre = proto_register_protocol("Generic Routing Encapsulation", "gre");
 271  /*       proto_register_field_array(proto_gre, hf, array_length(hf));*/
 272         proto_register_subtree_array(ett, array_length(ett));
 273 }