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Diffstat (limited to 'epan/dissectors/packet-null.c')
| -rw-r--r-- | epan/dissectors/packet-null.c | 487 |
1 files changed, 487 insertions, 0 deletions
diff --git a/epan/dissectors/packet-null.c b/epan/dissectors/packet-null.c new file mode 100644 index 0000000000..cf0dc20af6 --- /dev/null +++ b/epan/dissectors/packet-null.c @@ -0,0 +1,487 @@ +/* packet-null.c + * Routines for null packet disassembly + * + * $Id$ + * + * Ethereal - Network traffic analyzer + * By Gerald Combs <gerald@ethereal.com> + * + * This file created by Mike Hall <mlh@io.com> + * Copyright 1998 + * + * 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 <glib.h> + +#include <string.h> +#include <epan/packet.h> +#include "packet-null.h" +#include <epan/atalk-utils.h> +#include "prefs.h" +#include "packet-ip.h" +#include "packet-ipx.h" +#include "packet-osi.h" +#include "packet-ppp.h" +#include "etypes.h" +#include "aftypes.h" + +static dissector_table_t null_dissector_table; + +/* protocols and header fields */ +static int proto_null = -1; +static int hf_null_etype = -1; +static int hf_null_family = -1; + +static gint ett_null = -1; + +/* Null/loopback structs and definitions */ + +/* Family values. */ +static const value_string family_vals[] = { + {BSD_AF_INET, "IP" }, + {BSD_AF_ISO, "OSI" }, + {BSD_AF_APPLETALK, "Appletalk" }, + {BSD_AF_IPX, "Netware IPX/SPX"}, + {BSD_AF_INET6_BSD, "IPv6" }, + {BSD_AF_INET6_FREEBSD, "IPv6" }, + {BSD_AF_INET6_DARWIN, "IPv6" }, + {0, NULL } +}; + +static dissector_handle_t ppp_hdlc_handle; +static dissector_handle_t data_handle; +void +capture_null( const guchar *pd, int len, packet_counts *ld ) +{ + guint32 null_header; + + /* + * BSD drivers that use DLT_NULL - including the FreeBSD 3.2 ISDN-for-BSD + * drivers, as well as the 4.4-Lite and FreeBSD loopback drivers - + * stuff the AF_ value for the protocol, in *host* byte order, in the + * first four bytes. (BSD drivers that use DLT_LOOP, such as recent + * OpenBSD loopback drivers, stuff it in *network* byte order in the + * first four bytes.) + * + * However, the IRIX and UNICOS/mp snoop socket mechanism supplies, + * on loopback devices, a 4-byte header that has a 2 byte (big-endian) + * AF_ value and 2 bytes of 0, so it's + * + * 0000AAAA + * + * when read on a little-endian machine and + * + * AAAA0000 + * + * when read on a big-endian machine. The current CVS version of libpcap + * compensates for this by converting it to standard 4-byte format before + * processing the packet, but snoop captures from IRIX or UNICOS/mp + * have the 2-byte+2-byte header, as might tcpdump or libpcap captures + * with older versions of libpcap. + * + * AF_ values are small integers, and probably fit in 8 bits (current + * values on the BSDs do), and have their upper 24 bits zero. + * This means that, in practice, if you look at the header as a 32-bit + * integer in host byte order: + * + * on a little-endian machine: + * + * a little-endian DLT_NULL header looks like + * + * 000000AA + * + * a big-endian DLT_NULL header, or a DLT_LOOP header, looks + * like + * + * AA000000 + * + * an IRIX or UNICOS/mp DLT_NULL header looks like + * + * 0000AA00 + * + * on a big-endian machine: + * + * a big-endian DLT_NULL header, or a DLT_LOOP header, looks + * like + * + * 000000AA + * + * a little-endian DLT_NULL header looks like + * + * AA000000 + * + * an IRIX or UNICOS/mp DLT_NULL header looks like + * + * 00AA0000 + * + * However, according to Gerald Combs, a FreeBSD ISDN PPP dump that + * Andreas Klemm sent to ethereal-dev has a packet type of DLT_NULL, + * and the family bits look like PPP's protocol field. (Was this an + * older, or different, ISDN driver?) Looking at what appears to be + * that capture file, it appears that it's using PPP in HDLC framing, + * RFC 1549, wherein the first two octets of the frame are 0xFF + * (address) and 0x03 (control), so the header bytes are, in order: + * + * 0xFF + * 0x03 + * high-order byte of a PPP protocol field + * low-order byte of a PPP protocol field + * + * If we treat that as a 32-bit host-byte-order value, it looks like + * + * PPPP03FF + * + * where PPPP is a byte-swapped PPP protocol type if we read it on + * a little-endian machine and + * + * FF03PPPP + * + * where PPPP is a PPP protocol type if we read it on a big-endian + * machine. 0x0000 does not appear to be a valid PPP protocol type + * value, so at least one of those hex digits is guaranteed not to + * be 0. + * + * Old versions of libpcap for Linux used DLT_NULL for loopback devices, + * but not any other devices. (Current versions use DLT_EN10MB for it.) + * The Linux loopback driver puts an *Ethernet* header at the beginning + * of loopback packets, with fake source and destination addresses and + * the appropriate Ethernet type value; however, those older versions of + * libpcap for Linux compensated for this by skipping the source and + * destination MAC addresses, replacing them with 2 bytes of 0. + * This means that if we're reading the capture on a little-endian + * machine, the header, treated as a 32-bit integer, looks like + * + * EEEE0000 + * + * where EEEE is a byte-swapped Ethernet type, and if we're reading it + * on a big-endian machine, it looks like + * + * 0000EEEE + * + * where EEEE is an Ethernet type. + * + * If the first 2 bytes of the header are FF 03: + * + * it can't be a big-endian BSD DLT_NULL header, or a DLT_LOOP + * header, as AF_ values are small so the first 2 bytes of the + * header would be 0; + * + * it can't be a little-endian BSD DLT_NULL header, as the + * resulting AF_ value would be >= 0x03FF, which is too big + * for an AF_ value; + * + * it can't be an IRIX or UNICOS/mp DLT_NULL header, as the + * resulting AF_ value with be 0x03FF. + * + * So the first thing we do is check the first two bytes of the + * header; if it's FF 03, we treat the packet as a PPP frame. + * + * Otherwise, if the upper 16 bits are non-zero, either: + * + * it's a BSD DLT_NULL or DLT_LOOP header whose AF_ value + * is not in our byte order; + * + * it's an IRIX or UNICOS/mp DLT_NULL header being read on + * a big-endian machine; + * + * it's a Linux DLT_NULL header being read on a little-endian + * machine. + * + * In all those cases except for the IRIX or UNICOS/mp DLT_NULL header, + * we should byte-swap it (if it's a Linux DLT_NULL header, that'll + * put the Ethernet type in the right byte order). In the case + * of the IRIX or UNICOS/mp DLT_NULL header, we should just get + * the upper 16 bits as an AF_ value. + * + * If it's a BSD DLT_NULL or DLT_LOOP header whose AF_ value is not + * in our byte order, then the upper 2 hex digits would be non-zero + * and the next 2 hex digits down would be zero, as AF_ values fit in + * 8 bits, and the upper 2 hex digits are the *lower* 8 bits of the value. + * + * If it's an IRIX or UNICOS/mp DLT_NULL header, the upper 2 hex digits + * would be zero and the next 2 hex digits down would be non-zero, as + * the upper 16 bits are a big-endian AF_ value. Furthermore, the + * next 2 hex digits down are likely to be < 0x60, as 0x60 is 96, + * and, so far, we're far from requiring AF_ values that high. + * + * If it's a Linux DLT_NULL header, the third hex digit from the top + * will be >= 6, as Ethernet types are >= 1536, or 0x0600, and + * it's byte-swapped, so the second 2 hex digits from the top are + * >= 0x60. + * + * So, if the upper 16 bits are non-zero: + * + * if the upper 2 hex digits are 0 and the next 2 hex digits are + * in the range 0x00-0x5F, we treat it as a big-endian IRIX or + * UNICOS/mp DLT_NULL header; + * + * otherwise, we byte-swap it and do the next stage. + * + * If the upper 16 bits are zero, either: + * + * it's a BSD DLT_NULLor DLT_LOOP header whose AF_ value is in + * our byte order; + * + * it's an IRIX or UNICOS/mp DLT_NULL header being read on + * a little-endian machine; + * + * it's a Linux DLT_NULL header being read on a big-endian + * machine. + * + * In all of those cases except for the IRIX or UNICOS/mp DLT_NULL header, + * we should *not* byte-swap it. In the case of the IRIX or UNICOS/mp + * DLT_NULL header, we should extract the AF_ value and byte-swap it. + * + * If it's a BSD DLT_NULL or DLT_LOOP header whose AF_ value is + * in our byte order, the upper 6 hex digits would all be zero. + * + * If it's an IRIX or UNICOS/mp DLT_NULL header, the upper 4 hex + * digits would be zero and the next 2 hex digits would not be zero. + * Furthermore, the third hex digit from the bottom would be < + */ + if (!BYTES_ARE_IN_FRAME(0, len, 2)) { + ld->other++; + return; + } + if (pd[0] == 0xFF && pd[1] == 0x03) { + /* + * Hand it to PPP. + */ + capture_ppp_hdlc(pd, 0, len, ld); + } else { + /* + * Treat it as a normal DLT_NULL header. + */ + if (!BYTES_ARE_IN_FRAME(0, len, (int)sizeof(null_header))) { + ld->other++; + return; + } + memcpy((char *)&null_header, (const char *)&pd[0], sizeof(null_header)); + + if ((null_header & 0xFFFF0000) != 0) { + /* + * It is possible that the AF_ type was only a 16 bit value. + * IRIX and UNICOS/mp loopback snoop use a 4 byte header with + * AF_ type in the first 2 bytes! + * BSD AF_ types will always have the upper 8 bits as 0. + */ + if ((null_header & 0xFF000000) == 0 && + (null_header & 0x00FF0000) < 0x00060000) { + /* + * Looks like a IRIX or UNICOS/mp loopback header, in the + * correct byte order. Set the null header value to the + * AF_ type, which is in the upper 16 bits of "null_header". + */ + null_header >>= 16; + } else { + /* Byte-swap it. */ + null_header = BSWAP32(null_header); + } + } else { + /* + * Check for an IRIX or UNICOS/mp snoop header. + */ + if ((null_header & 0x000000FF) == 0 && + (null_header & 0x0000FF00) < 0x00000600) { + /* + * Looks like a IRIX or UNICOS/mp loopback header, in the + * wrong byte order. Set the null header value to the AF_ + * type; that's in the lower 16 bits of "null_header", but + * is byte-swapped. + */ + null_header = BSWAP16(null_header & 0xFFFF); + } + } + + /* + * The null header value must be greater than the IEEE 802.3 maximum + * frame length to be a valid Ethernet type; if it is, hand it + * to "ethertype()", otherwise treat it as a BSD AF_type (we wire + * in the values of the BSD AF_ types, because the values + * in the file will be BSD values, and the OS on which + * we're building this might not have the same values or + * might not have them defined at all; XXX - what if different + * BSD derivatives have different values?). + */ + if (null_header > IEEE_802_3_MAX_LEN) + capture_ethertype((guint16) null_header, pd, 4, len, ld); + else { + + switch (null_header) { + + case BSD_AF_INET: + capture_ip(pd, 4, len, ld); + break; + + default: + ld->other++; + break; + } + } + } +} + +static void +dissect_null(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) +{ + guint32 null_header; + proto_tree *fh_tree; + proto_item *ti; + tvbuff_t *next_tvb; + + /* + * See comment in "capture_null()" for an explanation of what we're + * doing. + */ + if (tvb_get_ntohs(tvb, 0) == 0xFF03) { + /* + * Hand it to PPP. + */ + call_dissector(ppp_hdlc_handle, tvb, pinfo, tree); + } else { + + /* load the top pane info. This should be overwritten by + the next protocol in the stack */ + if(check_col(pinfo->cinfo, COL_RES_DL_SRC)) + col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A" ); + if(check_col(pinfo->cinfo, COL_RES_DL_DST)) + col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A" ); + if(check_col(pinfo->cinfo, COL_PROTOCOL)) + col_set_str(pinfo->cinfo, COL_PROTOCOL, "N/A" ); + if(check_col(pinfo->cinfo, COL_INFO)) + col_set_str(pinfo->cinfo, COL_INFO, "Null/Loopback" ); + + /* + * Treat it as a normal DLT_NULL header. + */ + tvb_memcpy(tvb, (guint8 *)&null_header, 0, sizeof(null_header)); + + if ((null_header & 0xFFFF0000) != 0) { + /* + * It is possible that the AF_ type was only a 16 bit value. + * IRIX and UNICOS/mp loopback snoop use a 4 byte header with + * AF_ type in the first 2 bytes! + * BSD AF_ types will always have the upper 8 bits as 0. + */ + if ((null_header & 0xFF000000) == 0 && + (null_header & 0x00FF0000) < 0x00060000) { + /* + * Looks like a IRIX or UNICOS/mp loopback header, in the + * correct byte order. Set the null header value to the + * AF_ type, which is in the upper 16 bits of "null_header". + */ + null_header >>= 16; + } else { + /* Byte-swap it. */ + null_header = BSWAP32(null_header); + } + } else { + /* + * Check for an IRIX or UNICOS/mp snoop header. + */ + if ((null_header & 0x000000FF) == 0 && + (null_header & 0x0000FF00) < 0x00000600) { + /* + * Looks like a IRIX or UNICOS/mp loopback header, in the + * wrong byte order. Set the null header value to the AF_ + * type; that's in the lower 16 bits of "null_header", but + * is byte-swapped. + */ + null_header = BSWAP16(null_header & 0xFFFF); + } + } + + /* + * The null header value must be greater than the IEEE 802.3 maximum + * frame length to be a valid Ethernet type; if it is, hand it + * to "ethertype()", otherwise treat it as a BSD AF_type (we wire + * in the values of the BSD AF_ types, because the values + * in the file will be BSD values, and the OS on which + * we're building this might not have the same values or + * might not have them defined at all; XXX - what if different + * BSD derivatives have different values?). + */ + if (null_header > IEEE_802_3_MAX_LEN) { + if (tree) { + ti = proto_tree_add_item(tree, proto_null, tvb, 0, 4, FALSE); + fh_tree = proto_item_add_subtree(ti, ett_null); + } else + fh_tree = NULL; + ethertype((guint16) null_header, tvb, 4, pinfo, tree, fh_tree, hf_null_etype, -1, + 0); + } else { + /* populate a tree in the second pane with the status of the link + layer (ie none) */ + if (tree) { + ti = proto_tree_add_item(tree, proto_null, tvb, 0, 4, FALSE); + fh_tree = proto_item_add_subtree(ti, ett_null); + proto_tree_add_uint(fh_tree, hf_null_family, tvb, 0, 4, null_header); + } + + next_tvb = tvb_new_subset(tvb, 4, -1, -1); + if (!dissector_try_port(null_dissector_table, null_header, + next_tvb, pinfo, tree)) { + /* No sub-dissector found. Label rest of packet as "Data" */ + call_dissector(data_handle,next_tvb, pinfo, tree); + } + } + } +} + +void +proto_register_null(void) +{ + static hf_register_info hf[] = { + + /* registered here but handled in ethertype.c */ + { &hf_null_etype, + { "Type", "null.type", FT_UINT16, BASE_HEX, VALS(etype_vals), 0x0, + "", HFILL }}, + + { &hf_null_family, + { "Family", "null.family", FT_UINT32, BASE_DEC, VALS(family_vals), 0x0, + "", HFILL }} + }; + static gint *ett[] = { + &ett_null, + }; + + proto_null = proto_register_protocol("Null/Loopback", "Null", "null"); + proto_register_field_array(proto_null, hf, array_length(hf)); + proto_register_subtree_array(ett, array_length(ett)); + + /* subdissector code */ + null_dissector_table = register_dissector_table("null.type", + "BSD AF_ type", FT_UINT32, BASE_DEC); +} + +void +proto_reg_handoff_null(void) +{ + dissector_handle_t null_handle; + + /* + * Get a handle for the PPP-in-HDLC-like-framing dissector. + */ + ppp_hdlc_handle = find_dissector("ppp_hdlc"); + data_handle = find_dissector("data"); + null_handle = create_dissector_handle(dissect_null, proto_null); + dissector_add("wtap_encap", WTAP_ENCAP_NULL, null_handle); +} |