forked from osmocom/wireshark
79e1fdb9e5
statements. Move the setting of the Protocol column in the Appletalk ARP and IPX dissectors before anything is fetched from the packet, and also clear the Info column at that point in those and some other dissectors, so that if an exception is thrown, the columns don't reflect the previous protocol. Fix the registration of the IPX RIP dissector to use the right protocol ID. svn path=/trunk/; revision=2928
323 lines
10 KiB
C
323 lines
10 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 1.40 2001/01/22 00:20:29 guy Exp $
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*
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* Ethereal - Network traffic analyzer
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* By Gerald Combs <gerald@zing.org>
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*
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* This file created and 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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#ifdef HAVE_SYS_TYPES_H
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#include <sys/types.h>
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#endif
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#include <glib.h>
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#ifdef HAVE_SYS_SOCKET_H
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#include <sys/socket.h>
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#endif
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#include <string.h>
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#include "packet.h"
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#include "packet-null.h"
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#include "packet-atalk.h"
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#include "packet-ip.h"
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#include "packet-ipv6.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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extern const value_string etype_vals[];
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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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{0, NULL }
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};
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static dissector_handle_t ppp_handle;
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void
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capture_null( const u_char *pd, 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 (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(pd, 0, 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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memcpy((char *)&null_header, (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, 4, pd, 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, 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_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->fd, COL_RES_DL_SRC))
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col_set_str(pinfo->fd, COL_RES_DL_SRC, "N/A" );
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if(check_col(pinfo->fd, COL_RES_DL_DST))
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col_set_str(pinfo->fd, COL_RES_DL_DST, "N/A" );
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if(check_col(pinfo->fd, COL_PROTOCOL))
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col_set_str(pinfo->fd, COL_PROTOCOL, "N/A" );
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if(check_col(pinfo->fd, COL_INFO))
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col_set_str(pinfo->fd, 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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dissect_data(next_tvb, 0, 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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"" }},
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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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"" }}
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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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}
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void
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proto_reg_handoff_null(void)
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{
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/*
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* Get a handle for the PPP dissector.
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*/
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ppp_handle = find_dissector("ppp");
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dissector_add("wtap_encap", WTAP_ENCAP_NULL, dissect_null, proto_null);
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}
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