2 * Routines for ethernet packet disassembly
4 * $Id: packet-eth.c,v 1.25 1999/11/30 23:56:35 gram Exp $
6 * Ethereal - Network traffic analyzer
7 * By Gerald Combs <gerald@zing.org>
8 * Copyright 1998 Gerald Combs
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version 2
14 * of the License, or (at your option) any later version.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
30 #ifdef HAVE_SYS_TYPES_H
31 # include <sys/types.h>
39 extern const value_string etype_vals[];
41 /* protocols and header fields */
42 static int proto_eth = -1;
43 static int hf_eth_dst = -1;
44 static int hf_eth_src = -1;
45 static int hf_eth_len = -1;
46 static int hf_eth_type = -1;
48 static gint ett_ieee8023 = -1;
49 static gint ett_ether2 = -1;
51 #define ETH_HEADER_SIZE 14
53 /* These are the Netware-ish names for the different Ethernet frame types.
54 EthernetII: The ethernet with a Type field instead of a length field
55 Ethernet802.2: An 802.3 header followed by an 802.3 header
56 Ethernet802.3: A raw 802.3 packet. IPX/SPX can be the only payload.
57 There's not 802.2 hdr in this.
58 EthernetSNAP: Basically 802.2, just with 802.2SNAP. For our purposes,
59 there's no difference between 802.2 and 802.2SNAP, since we just
60 pass it down to dissect_llc(). -- Gilbert
63 #define ETHERNET_802_2 1
64 #define ETHERNET_802_3 2
65 #define ETHERNET_SNAP 3
68 capture_eth(const u_char *pd, guint32 cap_len, packet_counts *ld) {
70 int offset = ETH_HEADER_SIZE;
71 int ethhdr_type; /* the type of ethernet frame */
73 if (cap_len < ETH_HEADER_SIZE) {
78 etype = (pd[12] << 8) | pd[13];
80 /* either ethernet802.3 or ethernet802.2 */
81 if (etype <= IEEE_802_3_MAX_LEN) {
83 /* Is there an 802.2 layer? I can tell by looking at the first 2
84 bytes after the 802.3 header. If they are 0xffff, then what
85 follows the 802.3 header is an IPX payload, meaning no 802.2.
86 (IPX/SPX is they only thing that can be contained inside a
87 straight 802.3 packet). A non-0xffff value means that there's an
88 802.2 layer inside the 802.3 layer */
89 if (pd[14] == 0xff && pd[15] == 0xff) {
90 ethhdr_type = ETHERNET_802_3;
93 ethhdr_type = ETHERNET_802_2;
96 ethhdr_type = ETHERNET_II;
99 switch (ethhdr_type) {
101 capture_ipx(pd, offset, cap_len, ld);
104 capture_llc(pd, offset, cap_len, ld);
107 capture_ethertype(etype, offset, pd, cap_len, ld);
113 dissect_eth(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
114 guint16 etype, length;
115 proto_tree *fh_tree = NULL;
117 int ethhdr_type; /* the type of ethernet frame */
119 if (fd->cap_len < ETH_HEADER_SIZE) {
120 dissect_data(pd, offset, fd, tree);
124 SET_ADDRESS(&pi.dl_src, AT_ETHER, 6, &pd[offset+6]);
125 SET_ADDRESS(&pi.src, AT_ETHER, 6, &pd[offset+6]);
126 SET_ADDRESS(&pi.dl_dst, AT_ETHER, 6, &pd[offset+0]);
127 SET_ADDRESS(&pi.dst, AT_ETHER, 6, &pd[offset+0]);
129 if (check_col(fd, COL_PROTOCOL))
130 col_add_str(fd, COL_PROTOCOL, "Ethernet");
132 etype = pntohs(&pd[offset+12]);
134 /* either ethernet802.3 or ethernet802.2 */
135 if (etype <= IEEE_802_3_MAX_LEN) {
138 /* Is there an 802.2 layer? I can tell by looking at the first 2
139 bytes after the 802.3 header. If they are 0xffff, then what
140 follows the 802.3 header is an IPX payload, meaning no 802.2.
141 (IPX/SPX is they only thing that can be contained inside a
142 straight 802.3 packet). A non-0xffff value means that there's an
143 802.2 layer inside the 802.3 layer */
144 if (pd[offset+14] == 0xff && pd[offset+15] == 0xff) {
145 ethhdr_type = ETHERNET_802_3;
148 ethhdr_type = ETHERNET_802_2;
151 if (check_col(fd, COL_INFO)) {
152 col_add_fstr(fd, COL_INFO, "IEEE 802.3 %s",
153 (ethhdr_type == ETHERNET_802_3 ? "Raw " : ""));
157 ti = proto_tree_add_item_format(tree, proto_eth, offset, ETH_HEADER_SIZE,
158 NULL, "IEEE 802.3 %s", (ethhdr_type == ETHERNET_802_3 ? "Raw " : ""));
160 fh_tree = proto_item_add_subtree(ti, ett_ieee8023);
162 proto_tree_add_item(fh_tree, hf_eth_dst, offset+0, 6, &pd[offset+0]);
163 proto_tree_add_item(fh_tree, hf_eth_src, offset+6, 6, &pd[offset+6]);
164 proto_tree_add_item(fh_tree, hf_eth_len, offset+12, 2, length);
166 /* Convert the LLC length from the 802.3 header to a total
167 length, by adding in the Ethernet header size, and set
168 the payload and captured-payload lengths to the minima
169 of the total length and the frame lengths. */
170 length += ETH_HEADER_SIZE;
173 if (pi.captured_len > length)
174 pi.captured_len = length;
178 ethhdr_type = ETHERNET_II;
179 if (check_col(fd, COL_INFO))
180 col_add_str(fd, COL_INFO, "Ethernet II");
183 ti = proto_tree_add_item_format(tree, proto_eth, offset, ETH_HEADER_SIZE,
184 NULL, "Ethernet II");
186 fh_tree = proto_item_add_subtree(ti, ett_ether2);
188 proto_tree_add_item(fh_tree, hf_eth_dst, offset+0, 6, &pd[offset+0]);
189 proto_tree_add_item(fh_tree, hf_eth_src, offset+6, 6, &pd[offset+6]);
192 offset += ETH_HEADER_SIZE;
194 switch (ethhdr_type) {
196 dissect_ipx(pd, offset, fd, tree);
199 dissect_llc(pd, offset, fd, tree);
202 ethertype(etype, offset, pd, fd, tree, fh_tree, hf_eth_type);
208 proto_register_eth(void)
210 static hf_register_info hf[] = {
213 { "Destination", "eth.dst", FT_ETHER, BASE_NONE, NULL, 0x0,
214 "Destination Hardware Address" }},
217 { "Source", "eth.src", FT_ETHER, BASE_NONE, NULL, 0x0,
218 "Source Hardware Address" }},
221 { "Length", "eth.len", FT_UINT16, BASE_DEC, NULL, 0x0,
224 /* registered here but handled in ethertype.c */
226 { "Type", "eth.type", FT_UINT16, BASE_HEX, VALS(etype_vals), 0x0,
229 static gint *ett[] = {
234 proto_eth = proto_register_protocol ("Ethernet", "eth" );
235 proto_register_field_array(proto_eth, hf, array_length(hf));
236 proto_register_subtree_array(ett, array_length(ett));