print-null.c revision 1.9 
1/*
2 * Copyright (c) 1991, 1993, 1994, 1995, 1996, 1997
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that: (1) source code distributions
7 * retain the above copyright notice and this paragraph in its entirety, (2)
8 * distributions including binary code include the above copyright notice and
9 * this paragraph in its entirety in the documentation or other materials
10 * provided with the distribution, and (3) all advertising materials mentioning
11 * features or use of this software display the following acknowledgement:
12 * ``This product includes software developed by the University of California,
13 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
14 * the University nor the names of its contributors may be used to endorse
15 * or promote products derived from this software without specific prior
16 * written permission.
17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20 */
21
22#include <sys/cdefs.h>
23#ifndef lint
24__RCSID("$NetBSD: print-null.c,v 1.9 2023/08/17 20:19:40 christos Exp $");
25#endif
26
27/* \summary: BSD loopback device printer */
28
29#ifdef HAVE_CONFIG_H
30#include <config.h>
31#endif
32
33#include "netdissect-stdinc.h"
34
35#define ND_LONGJMP_FROM_TCHECK
36#include "netdissect.h"
37#include "extract.h"
38#include "af.h"
39
40
41/*
42 * The DLT_NULL packet header is 4 bytes long. It contains a host-byte-order
43 * 32-bit integer that specifies the family, e.g. AF_INET.
44 *
45 * Note here that "host" refers to the host on which the packets were
46 * captured; that isn't necessarily *this* host.
47 *
48 * The OpenBSD DLT_LOOP packet header is the same, except that the integer
49 * is in network byte order.
50 */
51#define	NULL_HDRLEN 4
52
53/*
54 * Byte-swap a 32-bit number.
55 * ("htonl()" or "ntohl()" won't work - we want to byte-swap even on
56 * big-endian platforms.)
57 */
58#define	SWAPLONG(y) \
59((((y)&0xff)<<24) | (((y)&0xff00)<<8) | (((y)&0xff0000)>>8) | (((y)>>24)&0xff))
60
61static void
62null_hdr_print(netdissect_options *ndo, uint32_t family, u_int length)
63{
64	if (!ndo->ndo_qflag) {
65		ND_PRINT("AF %s (%u)",
66			tok2str(bsd_af_values,"Unknown",family),family);
67	} else {
68		ND_PRINT("%s",
69			tok2str(bsd_af_values,"Unknown AF %u",family));
70	}
71
72	ND_PRINT(", length %u: ", length);
73}
74
75/*
76 * This is the top level routine of the printer.  'p' points
77 * to the ether header of the packet, 'h->ts' is the timestamp,
78 * 'h->len' is the length of the packet off the wire, and 'h->caplen'
79 * is the number of bytes actually captured.
80 */
81void
82null_if_print(netdissect_options *ndo, const struct pcap_pkthdr *h, const u_char *p)
83{
84	u_int length = h->len;
85	u_int caplen = h->caplen;
86	uint32_t family;
87
88	ndo->ndo_protocol = "null";
89	ND_TCHECK_LEN(p, NULL_HDRLEN);
90	ndo->ndo_ll_hdr_len += NULL_HDRLEN;
91
92	family = GET_HE_U_4(p);
93
94	/*
95	 * This isn't necessarily in our host byte order; if this is
96	 * a DLT_LOOP capture, it's in network byte order, and if
97	 * this is a DLT_NULL capture from a machine with the opposite
98	 * byte-order, it's in the opposite byte order from ours.
99	 *
100	 * If the upper 16 bits aren't all zero, assume it's byte-swapped.
101	 */
102	if ((family & 0xFFFF0000) != 0)
103		family = SWAPLONG(family);
104
105	if (ndo->ndo_eflag)
106		null_hdr_print(ndo, family, length);
107
108	length -= NULL_HDRLEN;
109	caplen -= NULL_HDRLEN;
110	p += NULL_HDRLEN;
111
112	switch (family) {
113
114	case BSD_AFNUM_INET:
115		ip_print(ndo, p, length);
116		break;
117
118	case BSD_AFNUM_INET6_BSD:
119	case BSD_AFNUM_INET6_FREEBSD:
120	case BSD_AFNUM_INET6_DARWIN:
121		ip6_print(ndo, p, length);
122		break;
123
124	case BSD_AFNUM_ISO:
125		isoclns_print(ndo, p, length);
126		break;
127
128	case BSD_AFNUM_APPLETALK:
129		atalk_print(ndo, p, length);
130		break;
131
132	case BSD_AFNUM_IPX:
133		ipx_print(ndo, p, length);
134		break;
135
136	default:
137		/* unknown AF_ value */
138		if (!ndo->ndo_eflag)
139			null_hdr_print(ndo, family, length + NULL_HDRLEN);
140		if (!ndo->ndo_suppress_default_print)
141			ND_DEFAULTPRINT(p, caplen);
142	}
143}
144