/* packet-eth.c * Routines for ethernet packet disassembly * * $Id: packet-eth.c,v 1.89 2004/02/03 23:19:54 guy 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 #include #include #include "prefs.h" #include "etypes.h" #include #include "packet-eth.h" #include "packet-ieee8023.h" #include "packet-ipx.h" #include "packet-isl.h" #include "packet-llc.h" #include "crc32.h" #include "tap.h" /* Interpret capture file as FW1 monitor file */ static gboolean eth_interpret_as_fw1_monitor = FALSE; /* protocols and header fields */ static int proto_eth = -1; static int hf_eth_dst = -1; static int hf_eth_src = -1; static int hf_eth_len = -1; static int hf_eth_type = -1; static int hf_eth_addr = -1; static int hf_eth_trailer = -1; static gint ett_ieee8023 = -1; static gint ett_ether2 = -1; static dissector_handle_t isl_handle; static dissector_handle_t fw1_handle; static heur_dissector_list_t heur_subdissector_list; static int eth_tap = -1; #define ETH_HEADER_SIZE 14 /* These are the Netware-ish names for the different Ethernet frame types. EthernetII: The ethernet with a Type field instead of a length field Ethernet802.2: An 802.3 header followed by an 802.2 header Ethernet802.3: A raw 802.3 packet. IPX/SPX can be the only payload. There's no 802.2 hdr in this. EthernetSNAP: Basically 802.2, just with 802.2SNAP. For our purposes, there's no difference between 802.2 and 802.2SNAP, since we just pass it down to the LLC dissector. -- Gilbert */ #define ETHERNET_II 0 #define ETHERNET_802_2 1 #define ETHERNET_802_3 2 #define ETHERNET_SNAP 3 void capture_eth(const guchar *pd, int offset, int len, packet_counts *ld) { guint16 etype, length; int ethhdr_type; /* the type of ethernet frame */ if (!BYTES_ARE_IN_FRAME(offset, len, ETH_HEADER_SIZE)) { ld->other++; return; } etype = pntohs(&pd[offset+12]); /* * If the type/length field is <= the maximum 802.3 length, * and is not zero, this is an 802.3 frame, and it's a length * field; it might be an Novell "raw 802.3" frame, with no * 802.2 LLC header, or it might be a frame with an 802.2 LLC * header. * * If the type/length field is > the maximum 802.3 length, * this is an Ethernet II frame, and it's a type field. * * If the type/length field is zero (ETHERTYPE_UNK), this is * a frame used internally by the Cisco MDS switch to contain * Fibre Channel ("Vegas"). We treat that as an Ethernet II * frame; the dissector for those frames registers itself with * an ethernet type of ETHERTYPE_UNK. */ if (etype <= IEEE_802_3_MAX_LEN && etype != ETHERTYPE_UNK) { length = etype; /* Is there an 802.2 layer? I can tell by looking at the first 2 bytes after the 802.3 header. If they are 0xffff, then what follows the 802.3 header is an IPX payload, meaning no 802.2. (IPX/SPX is they only thing that can be contained inside a straight 802.3 packet). A non-0xffff value means that there's an 802.2 layer inside the 802.3 layer */ if (pd[offset+14] == 0xff && pd[offset+15] == 0xff) { ethhdr_type = ETHERNET_802_3; } else { ethhdr_type = ETHERNET_802_2; } /* Oh, yuck. Cisco ISL frames require special interpretation of the destination address field; fortunately, they can be recognized by checking the first 5 octets of the destination address, which are 01-00-0C-00-00 for ISL frames. */ if (pd[offset] == 0x01 && pd[offset+1] == 0x00 && pd[offset+2] == 0x0C && pd[offset+3] == 0x00 && pd[offset+4] == 0x00) { capture_isl(pd, offset, len, ld); return; } /* Convert the LLC length from the 802.3 header to a total frame length, by adding in the size of any data that preceded the Ethernet header, and adding in the Ethernet header size, and set the payload and captured-payload lengths to the minima of the total length and the frame lengths. */ length += offset + ETH_HEADER_SIZE; if (len > length) len = length; } else { ethhdr_type = ETHERNET_II; } offset += ETH_HEADER_SIZE; switch (ethhdr_type) { case ETHERNET_802_3: capture_ipx(ld); break; case ETHERNET_802_2: capture_llc(pd, offset, len, ld); break; case ETHERNET_II: capture_ethertype(etype, pd, offset, len, ld); break; } } static void dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int fcs_len) { proto_item *ti; eth_hdr *ehdr; volatile gboolean is_802_2; proto_tree *volatile fh_tree = NULL; const char *src_addr, *dst_addr; static eth_hdr ehdrs[4]; static int ehdr_num=0; ehdr_num++; if(ehdr_num>=4){ ehdr_num=0; } ehdr=&ehdrs[ehdr_num]; if (check_col(pinfo->cinfo, COL_PROTOCOL)) col_set_str(pinfo->cinfo, COL_PROTOCOL, "Ethernet"); src_addr=tvb_get_ptr(tvb, 6, 6); SET_ADDRESS(&pinfo->dl_src, AT_ETHER, 6, src_addr); SET_ADDRESS(&pinfo->src, AT_ETHER, 6, src_addr); SET_ADDRESS(&ehdr->src, AT_ETHER, 6, src_addr); dst_addr=tvb_get_ptr(tvb, 0, 6); SET_ADDRESS(&pinfo->dl_dst, AT_ETHER, 6, dst_addr); SET_ADDRESS(&pinfo->dst, AT_ETHER, 6, dst_addr); SET_ADDRESS(&ehdr->dst, AT_ETHER, 6, dst_addr); ehdr->type = tvb_get_ntohs(tvb, 12); /* * In case the packet is a non-Ethernet packet inside * Ethernet framing, allow heuristic dissectors to take * a first look before we assume that it's actually an * Ethernet packet. */ if (dissector_try_heuristic(heur_subdissector_list, tvb, pinfo, tree)) goto end_of_eth; /* * If the type/length field is <= the maximum 802.3 length, * and is not zero, this is an 802.3 frame, and it's a length * field; it might be an Novell "raw 802.3" frame, with no * 802.2 LLC header, or it might be a frame with an 802.2 LLC * header. * * If the type/length field is > the maximum 802.3 length, * this is an Ethernet II frame, and it's a type field. * * If the type/length field is zero (ETHERTYPE_UNK), this is * a frame used internally by the Cisco MDS switch to contain * Fibre Channel ("Vegas"). We treat that as an Ethernet II * frame; the dissector for those frames registers itself with * an ethernet type of ETHERTYPE_UNK. */ if (ehdr->type <= IEEE_802_3_MAX_LEN && ehdr->type != ETHERTYPE_UNK) { /* Oh, yuck. Cisco ISL frames require special interpretation of the destination address field; fortunately, they can be recognized by checking the first 5 octets of the destination address, which are 01-00-0C-00-00 for ISL frames. */ if ( tvb_get_guint8(tvb, 0) == 0x01 && tvb_get_guint8(tvb, 1) == 0x00 && tvb_get_guint8(tvb, 2) == 0x0C && tvb_get_guint8(tvb, 3) == 0x00 && tvb_get_guint8(tvb, 4) == 0x00 ) { call_dissector(isl_handle, tvb, pinfo, tree); goto end_of_eth; } /* Is there an 802.2 layer? I can tell by looking at the first 2 bytes after the 802.3 header. If they are 0xffff, then what follows the 802.3 header is an IPX payload, meaning no 802.2. (IPX/SPX is they only thing that can be contained inside a straight 802.3 packet). A non-0xffff value means that there's an 802.2 layer inside the 802.3 layer */ is_802_2 = TRUE; TRY { if (tvb_get_ntohs(tvb, 14) == 0xffff) { is_802_2 = FALSE; } } CATCH2(BoundsError, ReportedBoundsError) { ; /* do nothing */ } ENDTRY; if (check_col(pinfo->cinfo, COL_INFO)) { col_add_fstr(pinfo->cinfo, COL_INFO, "IEEE 802.3 Ethernet %s", (is_802_2 ? "" : "Raw ")); } if (tree) { ti = proto_tree_add_protocol_format(tree, proto_eth, tvb, 0, ETH_HEADER_SIZE, "IEEE 802.3 Ethernet %s", (is_802_2 ? "" : "Raw ")); fh_tree = proto_item_add_subtree(ti, ett_ieee8023); } proto_tree_add_ether(fh_tree, hf_eth_dst, tvb, 0, 6, dst_addr); proto_tree_add_ether(fh_tree, hf_eth_src, tvb, 6, 6, src_addr); /* add items for eth.addr filter */ proto_tree_add_ether_hidden(fh_tree, hf_eth_addr, tvb, 0, 6, dst_addr); proto_tree_add_ether_hidden(fh_tree, hf_eth_addr, tvb, 6, 6, src_addr); dissect_802_3(ehdr->type, is_802_2, tvb, ETH_HEADER_SIZE, pinfo, tree, fh_tree, hf_eth_len, hf_eth_trailer, fcs_len); } else { if (eth_interpret_as_fw1_monitor) { call_dissector(fw1_handle, tvb, pinfo, tree); goto end_of_eth; } if (check_col(pinfo->cinfo, COL_INFO)) col_set_str(pinfo->cinfo, COL_INFO, "Ethernet II"); if (tree) { ti = proto_tree_add_protocol_format(tree, proto_eth, tvb, 0, ETH_HEADER_SIZE, "Ethernet II, Src: %s, Dst: %s", ether_to_str(src_addr), ether_to_str(dst_addr)); fh_tree = proto_item_add_subtree(ti, ett_ether2); } proto_tree_add_ether(fh_tree, hf_eth_dst, tvb, 0, 6, dst_addr); proto_tree_add_ether(fh_tree, hf_eth_src, tvb, 6, 6, src_addr); /* add items for eth.addr filter */ proto_tree_add_ether_hidden(fh_tree, hf_eth_addr, tvb, 0, 6, dst_addr); proto_tree_add_ether_hidden(fh_tree, hf_eth_addr, tvb, 6, 6, src_addr); ethertype(ehdr->type, tvb, ETH_HEADER_SIZE, pinfo, tree, fh_tree, hf_eth_type, hf_eth_trailer, fcs_len); } end_of_eth: tap_queue_packet(eth_tap, pinfo, ehdr); return; } /* * Add an Ethernet trailer - which, for some captures, might be the FCS * rather than a pad-to-60-bytes trailer. * * If fcs_len is 0, we assume the frame has no FCS; if it's 4, we assume * it has an FCS; if it's anything else (such as -1, which means "maybe * it does, maybe it doesn't"), we try to infer whether it has an FCS. */ void add_ethernet_trailer(proto_tree *fh_tree, int trailer_id, tvbuff_t *tvb, tvbuff_t *trailer_tvb, int fcs_len) { /* If there're some bytes left over, show those bytes as a trailer. However, if the Ethernet frame was claimed to have had 64 or more bytes - i.e., it was at least an FCS worth of data longer than the minimum payload size - assume the last 4 bytes of the trailer are an FCS. */ if (trailer_tvb && fh_tree) { guint trailer_length, trailer_reported_length; gboolean has_fcs = FALSE; trailer_length = tvb_length(trailer_tvb); trailer_reported_length = tvb_reported_length(trailer_tvb); if (fcs_len != 0) { /* If fcs_len is 4, we assume we definitely have an FCS. Otherwise, then, if the frame is big enough that, if we have a trailer, it probably inclues an FCS, and we have enough space in the trailer for the FCS, we assume we have an FCS. "Big enough" means 64 bytes or more; any frame that big needs no trailer, as there's no need to pad an Ethernet packet past 60 bytes. The trailer must be at least 4 bytes long to have enough space for an FCS. */ if (fcs_len == 4 || (tvb_reported_length(tvb) >= 64 && trailer_reported_length >= 4)) { /* Either we know we have an FCS, or we believe we have an FCS. */ if (trailer_length < trailer_reported_length) { /* The packet is claimed to have enough data for a 4-byte FCS, but we didn't capture all of the packet. Slice off the 4-byte FCS from the reported length, and trim the captured length so it's no more than the reported length; that will slice off what of the FCS, if any, is in the captured packet. */ trailer_reported_length -= 4; if (trailer_length > trailer_reported_length) trailer_length = trailer_reported_length; has_fcs = TRUE; } else { /* We captured all of the packet, including what appears to be a 4-byte FCS. Slice it off. */ trailer_length -= 4; trailer_reported_length -= 4; has_fcs = TRUE; } } } if (trailer_length != 0) { proto_tree_add_item(fh_tree, trailer_id, trailer_tvb, 0, trailer_length, FALSE); } if (has_fcs) { guint32 sent_fcs = tvb_get_ntohl(trailer_tvb, trailer_length); guint32 fcs = crc32_tvb_802(tvb, tvb_length(tvb) - 4); if (fcs == sent_fcs) { proto_tree_add_text(fh_tree, trailer_tvb, trailer_length, 4, "Frame check sequence: 0x%08x (correct)", sent_fcs); } else { proto_tree_add_text(fh_tree, trailer_tvb, trailer_length, 4, "Frame check sequence: 0x%08x (incorrect, should be 0x%08x)", sent_fcs, fcs); } } } } /* Called for the Ethernet Wiretap encapsulation type; pass the FCS length reported to us. */ static void dissect_eth_maybefcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) { dissect_eth_common(tvb, pinfo, tree, pinfo->pseudo_header->eth.fcs_len); } /* Called by other dissectors - for now, we assume Ethernet encapsulated inside other protocols doesn't include the FCS. */ static void dissect_eth(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) { dissect_eth_common(tvb, pinfo, tree, 0); } void proto_register_eth(void) { static hf_register_info hf[] = { { &hf_eth_dst, { "Destination", "eth.dst", FT_ETHER, BASE_NONE, NULL, 0x0, "Destination Hardware Address", HFILL }}, { &hf_eth_src, { "Source", "eth.src", FT_ETHER, BASE_NONE, NULL, 0x0, "Source Hardware Address", HFILL }}, { &hf_eth_len, { "Length", "eth.len", FT_UINT16, BASE_DEC, NULL, 0x0, "", HFILL }}, /* registered here but handled in ethertype.c */ { &hf_eth_type, { "Type", "eth.type", FT_UINT16, BASE_HEX, VALS(etype_vals), 0x0, "", HFILL }}, { &hf_eth_addr, { "Source or Destination Address", "eth.addr", FT_ETHER, BASE_NONE, NULL, 0x0, "Source or Destination Hardware Address", HFILL }}, { &hf_eth_trailer, { "Trailer", "eth.trailer", FT_BYTES, BASE_NONE, NULL, 0x0, "Ethernet Trailer or Checksum", HFILL }}, }; static gint *ett[] = { &ett_ieee8023, &ett_ether2, }; module_t *eth_module; proto_eth = proto_register_protocol("Ethernet", "Ethernet", "eth"); proto_register_field_array(proto_eth, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); /* subdissector code */ register_heur_dissector_list("eth", &heur_subdissector_list); /* Register configuration preferences */ eth_module = prefs_register_protocol(proto_eth, NULL); prefs_register_bool_preference(eth_module, "interpret_as_fw1_monitor", "Interpret as FireWall-1 monitor file", "Whether the capture file should be interpreted as a CheckPoint FireWall-1 monitor file", ð_interpret_as_fw1_monitor); register_dissector("eth", dissect_eth, proto_eth); eth_tap = register_tap("eth"); } void proto_reg_handoff_eth(void) { dissector_handle_t eth_handle, eth_maybefcs_handle; /* * Get a handle for the ISL dissector. */ isl_handle = find_dissector("isl"); fw1_handle = find_dissector("fw1"); eth_maybefcs_handle = create_dissector_handle(dissect_eth_maybefcs, proto_eth); dissector_add("wtap_encap", WTAP_ENCAP_ETHERNET, eth_maybefcs_handle); eth_handle = find_dissector("eth"); dissector_add("ethertype", ETHERTYPE_ETHBRIDGE, eth_handle); dissector_add("chdlctype", ETHERTYPE_ETHBRIDGE, eth_handle); dissector_add("gre.proto", ETHERTYPE_ETHBRIDGE, eth_handle); }