forked from osmocom/wireshark
326 lines
11 KiB
C
326 lines
11 KiB
C
/* packet-null.c
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* Routines for null packet disassembly
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*
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* $Id: packet-null.c,v 1.57 2002/12/02 23:43:28 guy Exp $
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*
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* Ethereal - Network traffic analyzer
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* By Gerald Combs <gerald@ethereal.com>
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*
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* This file created by Mike Hall <mlh@io.com>
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* Copyright 1998
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifdef HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <glib.h>
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#include <string.h>
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#include <epan/packet.h>
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#include "packet-null.h"
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#include <epan/atalk-utils.h>
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#include "packet-ip.h"
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#include "packet-ipx.h"
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#include "packet-osi.h"
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#include "packet-ppp.h"
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#include "etypes.h"
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#include "aftypes.h"
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static dissector_table_t null_dissector_table;
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/* protocols and header fields */
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static int proto_null = -1;
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static int hf_null_etype = -1;
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static int hf_null_family = -1;
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static gint ett_null = -1;
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/* Null/loopback structs and definitions */
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/* Family values. */
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static const value_string family_vals[] = {
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{BSD_AF_INET, "IP" },
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{BSD_AF_ISO, "OSI" },
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{BSD_AF_APPLETALK, "Appletalk" },
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{BSD_AF_IPX, "Netware IPX/SPX"},
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{BSD_AF_INET6_BSD, "IPv6" },
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{BSD_AF_INET6_FREEBSD, "IPv6" },
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{BSD_AF_INET6_DARWIN, "IPv6" },
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{0, NULL }
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};
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static dissector_handle_t ppp_hdlc_handle;
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static dissector_handle_t data_handle;
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void
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capture_null( const guchar *pd, int len, packet_counts *ld )
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{
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guint32 null_header;
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/*
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* BSD drivers that use DLT_NULL - including the FreeBSD 3.2 ISDN-for-BSD
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* drivers, as well as the 4.4-Lite and FreeBSD loopback drivers -
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* appear to stuff the AF_ value for the protocol, in *host* byte
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* order, in the first four bytes.
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*
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* However, according to Gerald Combs, a FreeBSD ISDN PPP dump that
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* Andreas Klemm sent to ethereal-dev has a packet type of DLT_NULL,
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* and the family bits look like PPP's protocol field. (Was this an
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* older, or different, ISDN driver?) Looking at what appears to be
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* that capture file, it appears that it's using PPP in HDLC framing,
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* RFC 1549, wherein the first two octets of the frame are 0xFF
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* (address) and 0x03 (control), so the header bytes are, in order:
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*
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* 0xFF
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* 0x03
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* high-order byte of a PPP protocol field
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* low-order byte of a PPP protocol field
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*
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* when reading it on a little-endian machine; that means it's
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* PPPP03FF, where PPPP is a byte-swapped PPP protocol field.
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*
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* "libpcap" for Linux uses DLT_NULL only for the loopback device.
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* The loopback driver in Linux 2.0.36, at least, puts an *Ethernet*
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* header at the beginning of loopback packets; however, "libpcap"
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* for Linux compensates for this by skipping the source and
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* destination MAC addresses, replacing them with 2 bytes of 0.
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* This means that if we're reading the capture on a little-endian
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* machine, the header, treated as a 32-bit integer, looks like
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*
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* EEEEEEEEEEEEEEEE0000000000000000
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*
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* where "EEEEEEEEEEEEEEEE" is the Ethernet type, and if we're reading
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* it on a big-endian machine, it looks like
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*
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* 0000000000000000EEEEEEEEEEEEEEEE
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*
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* The Ethernet type might or might not be byte-swapped; I haven't
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* bothered thinking about that yet.
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*
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* AF_ values are (relatively) small integers, and shouldn't have their
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* upper 16 bits zero; Ethernet types have to fit in 16 bits and
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* thus must have their upper 16 bits zero. Therefore, if the upper
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* 16 bits of the field aren't zero, it's in the wrong byte order.
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*
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* Ethernet types are bigger than 1536, and AF_ values are smaller
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* than 1536, so we needn't worry about one being mistaken for
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* the other. (There may be a problem if the 16-bit Ethernet
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* type is byte-swapped as a 16-bit quantity, but if when treated
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* as a 32-bit quantity its upper 16 bits are zero, but I'll think
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* about that one later.)
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*
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* As for the PPP protocol field values:
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*
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* 0x0000 does not appear to be a valid PPP protocol field value,
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* so the upper 16 bits will be non-zero, and we'll byte swap it.
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* It'll then be
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*
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* 0xFF03PPPP
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*
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* where PPPP is a non-byte-swapped PPP protocol field; we'll
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* check for the upper 16 bits of the byte-swapped field being
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* non-zero and, if so, assume the lower 16 bits are a PPP
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* protocol field (AF_ and Ethernet protocol fields should leave
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* the upper 16 bits zero - unless somebody stuff something else
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* there; see below).
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*
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* So, to compensate for this mess, we:
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*
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* check if the first two octets are 0xFF and 0x03 and, if so,
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* treat it as a PPP frame;
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*
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* otherwise, byte-swap the value if its upper 16 bits aren't zero,
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* and compare the lower 16 bits of the value against Ethernet
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* and AF_ types.
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*
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* If, as implied by an earlier version of the "e_nullhdr" structure,
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* the family is only 16 bits, and there are "next" and "len" fields
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* before it, that all goes completely to hell. (Note that, for
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* the BSD header, we could byte-swap it if the capture was written
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* on a machine with the opposite byte-order to ours - the "libpcap"
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* header lets us determine that - but it's more of a mess for Linux,
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* given that the effect of inserting the two 0 bytes depends only
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* on the byte order of the machine reading the file.)
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*/
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if (!BYTES_ARE_IN_FRAME(0, len, 2)) {
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ld->other++;
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return;
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}
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if (pd[0] == 0xFF && pd[1] == 0x03) {
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/*
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* Hand it to PPP.
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*/
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capture_ppp_hdlc(pd, 0, len, ld);
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} else {
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/*
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* Treat it as a normal DLT_NULL header.
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*/
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if (!BYTES_ARE_IN_FRAME(0, len, (int)sizeof(null_header))) {
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ld->other++;
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return;
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}
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memcpy((char *)&null_header, (const char *)&pd[0], sizeof(null_header));
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if ((null_header & 0xFFFF0000) != 0) {
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/* Byte-swap it. */
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null_header = BSWAP32(null_header);
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}
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/*
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* The null header value must be greater than the IEEE 802.3 maximum
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* frame length to be a valid Ethernet type; if it is, hand it
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* to "ethertype()", otherwise treat it as a BSD AF_type (we wire
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* in the values of the BSD AF_ types, because the values
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* in the file will be BSD values, and the OS on which
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* we're building this might not have the same values or
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* might not have them defined at all; XXX - what if different
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* BSD derivatives have different values?).
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*/
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if (null_header > IEEE_802_3_MAX_LEN)
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capture_ethertype(null_header, pd, 4, len, ld);
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else {
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switch (null_header) {
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case BSD_AF_INET:
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capture_ip(pd, 4, len, ld);
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break;
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default:
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ld->other++;
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break;
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}
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}
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}
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}
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static void
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dissect_null(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
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{
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guint32 null_header;
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proto_tree *fh_tree;
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proto_item *ti;
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tvbuff_t *next_tvb;
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/*
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* See comment in "capture_null()" for an explanation of what we're
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* doing.
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*/
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if (tvb_get_ntohs(tvb, 0) == 0xFF03) {
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/*
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* Hand it to PPP.
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*/
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call_dissector(ppp_hdlc_handle, tvb, pinfo, tree);
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} else {
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/* load the top pane info. This should be overwritten by
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the next protocol in the stack */
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if(check_col(pinfo->cinfo, COL_RES_DL_SRC))
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col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A" );
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if(check_col(pinfo->cinfo, COL_RES_DL_DST))
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col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A" );
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if(check_col(pinfo->cinfo, COL_PROTOCOL))
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col_set_str(pinfo->cinfo, COL_PROTOCOL, "N/A" );
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if(check_col(pinfo->cinfo, COL_INFO))
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col_set_str(pinfo->cinfo, COL_INFO, "Null/Loopback" );
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/*
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* Treat it as a normal DLT_NULL header.
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*/
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tvb_memcpy(tvb, (guint8 *)&null_header, 0, sizeof(null_header));
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if ((null_header & 0xFFFF0000) != 0) {
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/* Byte-swap it. */
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null_header = BSWAP32(null_header);
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}
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/*
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* The null header value must be greater than the IEEE 802.3 maximum
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* frame length to be a valid Ethernet type; if it is, hand it
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* to "ethertype()", otherwise treat it as a BSD AF_type (we wire
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* in the values of the BSD AF_ types, because the values
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* in the file will be BSD values, and the OS on which
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* we're building this might not have the same values or
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* might not have them defined at all; XXX - what if different
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* BSD derivatives have different values?).
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*/
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if (null_header > IEEE_802_3_MAX_LEN) {
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if (tree) {
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ti = proto_tree_add_item(tree, proto_null, tvb, 0, 4, FALSE);
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fh_tree = proto_item_add_subtree(ti, ett_null);
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} else
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fh_tree = NULL;
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ethertype(null_header, tvb, 4, pinfo, tree, fh_tree, hf_null_etype, -1);
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} else {
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/* populate a tree in the second pane with the status of the link
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layer (ie none) */
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if (tree) {
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ti = proto_tree_add_item(tree, proto_null, tvb, 0, 4, FALSE);
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fh_tree = proto_item_add_subtree(ti, ett_null);
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proto_tree_add_uint(fh_tree, hf_null_family, tvb, 0, 4, null_header);
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}
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next_tvb = tvb_new_subset(tvb, 4, -1, -1);
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if (!dissector_try_port(null_dissector_table, null_header,
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next_tvb, pinfo, tree)) {
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/* No sub-dissector found. Label rest of packet as "Data" */
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call_dissector(data_handle,next_tvb, pinfo, tree);
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}
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}
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}
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}
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void
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proto_register_null(void)
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{
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static hf_register_info hf[] = {
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/* registered here but handled in ethertype.c */
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{ &hf_null_etype,
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{ "Type", "null.type", FT_UINT16, BASE_HEX, VALS(etype_vals), 0x0,
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"", HFILL }},
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{ &hf_null_family,
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{ "Family", "null.family", FT_UINT32, BASE_HEX, VALS(family_vals), 0x0,
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"", HFILL }}
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};
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static gint *ett[] = {
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&ett_null,
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};
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proto_null = proto_register_protocol("Null/Loopback", "Null", "null");
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proto_register_field_array(proto_null, hf, array_length(hf));
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proto_register_subtree_array(ett, array_length(ett));
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/* subdissector code */
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null_dissector_table = register_dissector_table("null.type",
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"BSD AF_ type", FT_UINT32, BASE_DEC);
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}
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void
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proto_reg_handoff_null(void)
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{
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dissector_handle_t null_handle;
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/*
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* Get a handle for the PPP-in-HDLC-like-framing dissector.
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*/
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ppp_hdlc_handle = find_dissector("ppp_hdlc");
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data_handle = find_dissector("data");
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null_handle = create_dissector_handle(dissect_null, proto_null);
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dissector_add("wtap_encap", WTAP_ENCAP_NULL, null_handle);
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}
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