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 1.1 1999/06/11 15:30:37 gram 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 #include <netinet/in.h>
  36 #include <glib.h>
  37 #include "packet.h"
  38
  39 /* bit positions for flags in header */
  40 #define GH_B_C          0x8000
  41 #define GH_B_R          0x4000
  42 #define GH_B_K          0x2000
  43 #define GH_B_S          0x1000
  44 #define GH_B_s          0x0800
  45 #define GH_B_RECUR      0x0700
  46 #define GH_P_A          0x0080  /* only in special PPTPized GRE header */
  47 #define GH_P_FLAGS      0x0078  /* only in special PPTPized GRE header */
  48 #define GH_R_FLAGS      0x00F8
  49 #define GH_B_VER        0x0007
  50
  51 #define GRE_PPP         0x880B
  52
  53 static int calc_len(guint16, int);
  54 static void add_flags_and_ver(proto_tree *, guint16, int, int);
  55
  56 void
  57 dissect_gre(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
  58
  59   guint16       flags_and_ver = pntohs(pd + offset);
  60   guint16       type          = pntohs(pd + offset + sizeof(flags_and_ver));
  61   static const value_string typevals[] = {
  62     { GRE_PPP, "PPP" },
  63     { 0,       NULL  }
  64   };
  65
  66   if (check_col(fd, COL_PROTOCOL))
  67     col_add_str(fd, COL_PROTOCOL, "GRE");
  68
  69   if (check_col(fd, COL_INFO)) {
  70     if (type == GRE_PPP)
  71       col_add_str(fd, COL_INFO, "Encapsulated PPP");
  72     else
  73       col_add_str(fd, COL_INFO, "Encapsulated unknown");
  74   }
  75
  76   if (fd->cap_len > offset && tree) {
  77     int                 is_ppp;
  78     proto_item *        ti;
  79     proto_tree *        gre_tree;
  80
  81     if (type == GRE_PPP) {
  82       is_ppp = 1;
  83       ti = proto_tree_add_item(tree, offset, calc_len(flags_and_ver, 1),
  84         "Generic Routing Encapsulation (PPP)");
  85       gre_tree = proto_tree_new();
  86       proto_item_add_subtree(ti, gre_tree, ETT_GRE);
  87       add_flags_and_ver(gre_tree, flags_and_ver, offset, 1);
  88     }
  89     else {
  90       is_ppp = 0;
  91       ti = proto_tree_add_item(tree, offset, calc_len(flags_and_ver, 1),
  92         "Generic Routing Encapsulation");
  93       gre_tree = proto_tree_new();
  94       proto_item_add_subtree(ti, gre_tree, ETT_GRE);
  95       add_flags_and_ver(gre_tree, flags_and_ver, offset, 0);
  96     }
  97
  98     offset += sizeof(flags_and_ver);
  99
 100     proto_tree_add_item(gre_tree, offset, sizeof(type),
 101                         "Protocol Type: %s (%#04x)",
 102                         val_to_str(type, typevals, "Unknown"), type);
 103     offset += sizeof(type);
 104
 105     if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
 106       guint16 checksum = pntohs(pd + offset);
 107       proto_tree_add_item(gre_tree, offset, sizeof(checksum),
 108                           "Checksum: %u", checksum);
 109       offset += sizeof(checksum);
 110     }
 111
 112     if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) {
 113       guint16 rtoffset = pntohs(pd + offset);
 114       proto_tree_add_item(gre_tree, offset, sizeof(rtoffset),
 115                           "Offset: %u", rtoffset);
 116       offset += sizeof(rtoffset);
 117     }
 118
 119     if (flags_and_ver & GH_B_K) {
 120       if (is_ppp) {
 121         guint16 paylen;
 122         guint16 callid;
 123
 124         paylen = pntohs(pd + offset);
 125         proto_tree_add_item(gre_tree, offset, sizeof(paylen),
 126                             "Payload length: %u", paylen);
 127         offset += sizeof(paylen);
 128
 129         callid = pntohs(pd + offset);
 130         proto_tree_add_item(gre_tree, offset, sizeof(callid),
 131                             "Call ID: %u", callid);
 132         offset += sizeof(callid);
 133       }
 134       else {
 135         guint32 key = pntohl(pd + offset);
 136         proto_tree_add_item(gre_tree, offset, sizeof(key),
 137                             "Key: %u", key);
 138         offset += sizeof(key);
 139       }
 140     }
 141
 142     if (flags_and_ver & GH_B_S) {
 143       guint32 seqnum = pntohl(pd + offset);
 144       proto_tree_add_item(gre_tree, offset, sizeof(seqnum),
 145                           "Sequence number: %u", seqnum);
 146       offset += sizeof(seqnum);
 147     }
 148
 149     if (is_ppp && flags_and_ver & GH_P_A) {
 150       guint32 acknum = pntohl(pd + offset);
 151       proto_tree_add_item(gre_tree, offset, sizeof(acknum),
 152                           "Acknowledgement number: %u", acknum);
 153       offset += sizeof(acknum);
 154     }
 155
 156     if (flags_and_ver & GH_B_R) {
 157       proto_tree_add_item(gre_tree, offset, sizeof(guint16),
 158                           "Address family: %u", pntohs(pd + offset));
 159       offset += sizeof(guint16);
 160       proto_tree_add_item(gre_tree, offset, 1,
 161                           "SRE offset: %u", pd[offset++]);
 162       proto_tree_add_item(gre_tree, offset, 1,
 163                           "SRE length: %u", pd[offset++]);
 164     }
 165
 166     switch (type) {
 167        case GRE_PPP:
 168         dissect_payload_ppp(pd, offset, fd, tree);
 169         break;
 170       default:
 171         dissect_data(pd, offset, fd, gre_tree);
 172     }
 173   }
 174 }
 175
 176 static int
 177 calc_len(guint16 flags_and_ver, int is_ppp) {
 178
 179   int   len = 4;
 180
 181   if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) len += 4;
 182   if (flags_and_ver & GH_B_K) len += 4;
 183   if (flags_and_ver & GH_B_S) len += 4;
 184   if (is_ppp && flags_and_ver & GH_P_A) len += 4;
 185
 186   return len;
 187 }
 188
 189 static void
 190 add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, int offset, int is_ppp) {
 191
 192   proto_item *  ti;
 193   proto_tree *  fv_tree;
 194   int           nbits = sizeof(flags_and_ver) * 8;
 195
 196   ti = proto_tree_add_item(tree, offset, 2,
 197                            "Flags and version: %#08x", flags_and_ver);
 198   fv_tree = proto_tree_new();
 199   proto_item_add_subtree(ti, fv_tree, ETT_GRE_FLAGS);
 200
 201   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 202                       decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits,
 203                                               "Checksum", "No checksum"));
 204   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 205                       decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits,
 206                                               "Routing", "No routing"));
 207   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 208                       decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits,
 209                                               "Key", "No key"));
 210   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 211                       decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits,
 212                                               "Sequence number", "No sequence number"));
 213   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 214                       decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits,
 215                                               "Strict source route", "No strict source route"));
 216   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 217                       decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits,
 218                                               "Recursion control: %u"));
 219   if (is_ppp) {
 220     proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 221                         decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits,
 222                                                 "Acknowledgment number", "No acknowledgment number"));
 223     proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 224                         decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits,
 225                                                 "Flags: %u"));
 226   }
 227   else {
 228     proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 229                         decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits,
 230                                                 "Flags: %u"));
 231   }
 232
 233   proto_tree_add_item(fv_tree, offset, sizeof(flags_and_ver), "%s",
 234                       decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits,
 235                                               "Version: %u"));
 236  }
 237