/* packet-gre.c * Routines for the Generic Routing Encapsulation (GRE) protocol * Brad Robel-Forrest * * $Id: packet-gre.c,v 1.25 2000/08/13 14:08:11 deniel Exp $ * * Ethereal - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #ifdef HAVE_CONFIG_H # include "config.h" #endif #ifdef HAVE_SYS_TYPES_H # include #endif #ifdef HAVE_NETINET_IN_H #include #endif #include #include "packet.h" #include "packet-ip.h" #include "packet-ppp.h" #include "packet-ipx.h" static int proto_gre = -1; static int hf_gre_proto = -1; static gint ett_gre = -1; static gint ett_gre_flags = -1; /* bit positions for flags in header */ #define GH_B_C 0x8000 #define GH_B_R 0x4000 #define GH_B_K 0x2000 #define GH_B_S 0x1000 #define GH_B_s 0x0800 #define GH_B_RECUR 0x0700 #define GH_P_A 0x0080 /* only in special PPTPized GRE header */ #define GH_P_FLAGS 0x0078 /* only in special PPTPized GRE header */ #define GH_R_FLAGS 0x00F8 #define GH_B_VER 0x0007 #define GRE_PPP 0x880B #define GRE_IP 0x0800 #define GRE_WCCP 0x883E #define GRE_IPX 0x8137 static void add_flags_and_ver(proto_tree *, guint16, int, int); static const value_string typevals[] = { { GRE_PPP, "PPP" }, { GRE_IP, "IP" }, { GRE_WCCP, "WCCP"}, { GRE_IPX, "IPX"}, { 0, NULL } }; static void dissect_gre(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) { guint16 flags_and_ver = pntohs(pd + offset); guint16 type = pntohs(pd + offset + sizeof(flags_and_ver)); guint16 sre_af; guint8 sre_length; tvbuff_t *next_tvb; OLD_CHECK_DISPLAY_AS_DATA(proto_gre, pd, offset, fd, tree); if (check_col(fd, COL_PROTOCOL)) col_add_str(fd, COL_PROTOCOL, "GRE"); if (check_col(fd, COL_INFO)) { col_add_fstr(fd, COL_INFO, "Encapsulated %s", val_to_str(type, typevals, "0x%04X (unknown)")); } if (IS_DATA_IN_FRAME(offset) && tree) { gboolean is_ppp = FALSE; gboolean is_wccp2 = FALSE; proto_item * ti; proto_tree * gre_tree; guint len = 4; if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) len += 4; if (flags_and_ver & GH_B_K) len += 4; if (flags_and_ver & GH_B_S) len += 4; switch (type) { case GRE_PPP: if (flags_and_ver & GH_P_A) len += 4; is_ppp = TRUE; break; case GRE_WCCP: /* WCCP2 apparently puts an extra 4 octets into the header, but uses the same encapsulation type; if it looks as if the first octet of the packet isn't the beginning of an IPv4 header, assume it's WCCP2. */ if ((pd[offset + sizeof(flags_and_ver) + sizeof(type)] & 0xF0) != 0x40) { len += 4; is_wccp2 = TRUE; } break; } ti = proto_tree_add_protocol_format(tree, proto_gre, NullTVB, offset, len, "Generic Routing Encapsulation (%s)", val_to_str(type, typevals, "0x%04X - unknown")); gre_tree = proto_item_add_subtree(ti, ett_gre); add_flags_and_ver(gre_tree, flags_and_ver, offset, is_ppp); offset += sizeof(flags_and_ver); proto_tree_add_uint(gre_tree, hf_gre_proto, NullTVB, offset, sizeof(type), type); offset += sizeof(type); if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) { guint16 checksum = pntohs(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(checksum), "Checksum: %u", checksum); offset += sizeof(checksum); } if (flags_and_ver & GH_B_C || flags_and_ver & GH_B_R) { guint16 rtoffset = pntohs(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(rtoffset), "Offset: %u", rtoffset); offset += sizeof(rtoffset); } if (flags_and_ver & GH_B_K) { if (is_ppp) { guint16 paylen; guint16 callid; paylen = pntohs(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(paylen), "Payload length: %u", paylen); offset += sizeof(paylen); callid = pntohs(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(callid), "Call ID: %u", callid); offset += sizeof(callid); } else { guint32 key = pntohl(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(key), "Key: %u", key); offset += sizeof(key); } } if (flags_and_ver & GH_B_S) { guint32 seqnum = pntohl(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(seqnum), "Sequence number: %u", seqnum); offset += sizeof(seqnum); } if (is_ppp && flags_and_ver & GH_P_A) { guint32 acknum = pntohl(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(acknum), "Acknowledgement number: %u", acknum); offset += sizeof(acknum); } if (flags_and_ver & GH_B_R) { for (;;) { sre_af = pntohs(pd + offset); proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(guint16), "Address family: %u", sre_af); offset += sizeof(guint16); proto_tree_add_text(gre_tree, NullTVB, offset, 1, "SRE offset: %u", pd[offset++]); sre_length = pd[offset]; proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(guint8), "SRE length: %u", sre_length); offset += sizeof(guint8); if (sre_af == 0 && sre_length == 0) break; offset += sre_length; } } switch (type) { case GRE_PPP: next_tvb = tvb_create_from_top(offset); dissect_ppp(next_tvb, &pi, tree); break; case GRE_IP: dissect_ip(pd, offset, fd, tree); break; case GRE_WCCP: if (is_wccp2) { proto_tree_add_text(gre_tree, NullTVB, offset, sizeof(guint32), "WCCPv2 Data"); offset += 4; } dissect_ip(pd, offset, fd, tree); break; case GRE_IPX: next_tvb = tvb_create_from_top(offset); dissect_ipx(next_tvb, &pi, tree); break; default: next_tvb = tvb_create_from_top(offset); dissect_data(next_tvb, &pi, gre_tree); break; } } } static void add_flags_and_ver(proto_tree *tree, guint16 flags_and_ver, int offset, int is_ppp) { proto_item * ti; proto_tree * fv_tree; int nbits = sizeof(flags_and_ver) * 8; ti = proto_tree_add_text(tree, NullTVB, offset, 2, "Flags and version: %#04x", flags_and_ver); fv_tree = proto_item_add_subtree(ti, ett_gre_flags); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_boolean_bitfield(flags_and_ver, GH_B_C, nbits, "Checksum", "No checksum")); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_boolean_bitfield(flags_and_ver, GH_B_R, nbits, "Routing", "No routing")); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_boolean_bitfield(flags_and_ver, GH_B_K, nbits, "Key", "No key")); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_boolean_bitfield(flags_and_ver, GH_B_S, nbits, "Sequence number", "No sequence number")); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_boolean_bitfield(flags_and_ver, GH_B_s, nbits, "Strict source route", "No strict source route")); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_numeric_bitfield(flags_and_ver, GH_B_RECUR, nbits, "Recursion control: %u")); if (is_ppp) { proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_boolean_bitfield(flags_and_ver, GH_P_A, nbits, "Acknowledgment number", "No acknowledgment number")); proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_numeric_bitfield(flags_and_ver, GH_P_FLAGS, nbits, "Flags: %u")); } else { proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_numeric_bitfield(flags_and_ver, GH_R_FLAGS, nbits, "Flags: %u")); } proto_tree_add_text(fv_tree, NullTVB, offset, sizeof(flags_and_ver), "%s", decode_numeric_bitfield(flags_and_ver, GH_B_VER, nbits, "Version: %u")); } void proto_register_gre(void) { static hf_register_info hf[] = { { &hf_gre_proto, { "Protocol Type", "gre.proto", FT_UINT16, BASE_HEX, VALS(typevals), 0x0, "The protocol that is GRE encapsulated"} }, }; static gint *ett[] = { &ett_gre, &ett_gre_flags, }; proto_gre = proto_register_protocol("Generic Routing Encapsulation", "gre"); proto_register_field_array(proto_gre, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); } void proto_reg_handoff_gre(void) { old_dissector_add("ip.proto", IP_PROTO_GRE, dissect_gre); }