sbin/dhclient/packet.c - freebsd in FreeBSD

/*	$OpenBSD: packet.c,v 1.9 2004/05/04 18:58:50 deraadt Exp $	*/

/* Packet assembly code, originally contributed by Archie Cobbs. */

/*
 * Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of The Internet Software Consortium nor the names
 *    of its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "dhcpd.h"

#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <netinet/if_ether.h>

#define ETHER_HEADER_SIZE (ETHER_ADDR_LEN * 2 + sizeof(u_int16_t))

u_int32_t	checksum(unsigned char *, unsigned, u_int32_t);
u_int32_t	wrapsum(u_int32_t);

void	assemble_ethernet_header(struct interface_info *, unsigned char *,
	    int *, struct hardware *);
ssize_t	decode_ethernet_header(struct interface_info *, unsigned char *,
	    int bufix, struct hardware *);

u_int32_t
checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
{
	int i;

	/* Checksum all the pairs of bytes first... */
	for (i = 0; i < (nbytes & ~1U); i += 2) {
		sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
		if (sum > 0xFFFF)
			sum -= 0xFFFF;
	}

	/*
	 * If there's a single byte left over, checksum it, too.
	 * Network byte order is big-endian, so the remaining byte is
	 * the high byte.
	 */
	if (i < nbytes) {
		sum += buf[i] << 8;
		if (sum > 0xFFFF)
			sum -= 0xFFFF;
	}

	return (sum);
}

u_int32_t
wrapsum(u_int32_t sum)
{
	sum = ~sum & 0xFFFF;
	return (htons(sum));
}

void
assemble_hw_header(struct interface_info *interface, unsigned char *buf,
    int *bufix, struct hardware *to)
{
	struct ether_header eh;

	if (to != NULL && to->hlen == 6) /* XXX */
		memcpy(eh.ether_dhost, to->haddr, sizeof(eh.ether_dhost));
	else
		memset(eh.ether_dhost, 0xff, sizeof(eh.ether_dhost));
	if (interface->hw_address.hlen == sizeof(eh.ether_shost))
		memcpy(eh.ether_shost, interface->hw_address.haddr,
		    sizeof(eh.ether_shost));
	else
		memset(eh.ether_shost, 0x00, sizeof(eh.ether_shost));

	eh.ether_type = htons(ETHERTYPE_IP);

	memcpy(&buf[*bufix], &eh, ETHER_HEADER_SIZE);
	*bufix += ETHER_HEADER_SIZE;
}

void
assemble_udp_ip_header(unsigned char *buf, int *bufix, u_int32_t from,
    u_int32_t to, unsigned int port, unsigned char *data, int len)
{
	struct ip ip;
	struct udphdr udp;

	ip.ip_v = 4;
	ip.ip_hl = 5;
	ip.ip_tos = IPTOS_LOWDELAY;
	ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
	ip.ip_id = 0;
	ip.ip_off = 0;
	ip.ip_ttl = 16;
	ip.ip_p = IPPROTO_UDP;
	ip.ip_sum = 0;
	ip.ip_src.s_addr = from;
	ip.ip_dst.s_addr = to;

	ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));

	/*
	 * While the BPF -- used for broadcasts -- expects a "true" IP header
	 * with all the bytes in network byte order, the raw socket interface
	 * which is used for unicasts expects the ip_len field to be in host
	 * byte order.  In both cases, the checksum has to be correct, so this
	 * is as good a place as any to turn the bytes around again.
	 */
	if (to != INADDR_BROADCAST)
		ip.ip_len = ntohs(ip.ip_len);

	memcpy(&buf[*bufix], &ip, sizeof(ip));
	*bufix += sizeof(ip);

	udp.uh_sport = htons(LOCAL_PORT);	/* XXX */
	udp.uh_dport = port;			/* XXX */
	udp.uh_ulen = htons(sizeof(udp) + len);
	memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));

	udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
	    checksum(data, len, checksum((unsigned char *)&ip.ip_src,
	    2 * sizeof(ip.ip_src),
	    IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));

	memcpy(&buf[*bufix], &udp, sizeof(udp));
	*bufix += sizeof(udp);
}

ssize_t
decode_hw_header(unsigned char *buf, int bufix, struct hardware *from)
{
	struct ether_header eh;

	memcpy(&eh, buf + bufix, ETHER_HEADER_SIZE);

	memcpy(from->haddr, eh.ether_shost, sizeof(eh.ether_shost));
	from->htype = ARPHRD_ETHER;
	from->hlen = sizeof(eh.ether_shost);

	return (sizeof(eh));
}

ssize_t
decode_udp_ip_header(unsigned char *buf, int bufix, struct sockaddr_in *from,
    unsigned char *data, int buflen)
{
	struct ip *ip;
	struct udphdr *udp;
	u_int32_t ip_len = (buf[bufix] & 0xf) << 2;
	u_int32_t sum, usum;
	static int ip_packets_seen;
	static int ip_packets_bad_checksum;
	static int udp_packets_seen;
	static int udp_packets_bad_checksum;
	static int udp_packets_length_checked;
	static int udp_packets_length_overflow;
	int len = 0;

	ip = (struct ip *)(buf + bufix);
	udp = (struct udphdr *)(buf + bufix + ip_len);

	/* Check the IP header checksum - it should be zero. */
	ip_packets_seen++;
	if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
		ip_packets_bad_checksum++;
		if (ip_packets_seen > 4 &&
		    (ip_packets_seen / ip_packets_bad_checksum) < 2) {
			note("%d bad IP checksums seen in %d packets",
			    ip_packets_bad_checksum, ip_packets_seen);
			ip_packets_seen = ip_packets_bad_checksum = 0;
		}
		return (-1);
	}

	if (ntohs(ip->ip_len) != buflen)
		debug("ip length %d disagrees with bytes received %d.",
		    ntohs(ip->ip_len), buflen);

	memcpy(&from->sin_addr, &ip->ip_src, 4);

	/*
	 * Compute UDP checksums, including the ``pseudo-header'', the
	 * UDP header and the data.   If the UDP checksum field is zero,
	 * we're not supposed to do a checksum.
	 */
	if (!data) {
		data = buf + bufix + ip_len + sizeof(*udp);
		len = ntohs(udp->uh_ulen) - sizeof(*udp);
		udp_packets_length_checked++;
		if (len + data > buf + bufix + buflen) {
			udp_packets_length_overflow++;
			if (udp_packets_length_checked > 4 &&
			    (udp_packets_length_checked /
			    udp_packets_length_overflow) < 2) {
				note("%d udp packets in %d too long - dropped",
				    udp_packets_length_overflow,
				    udp_packets_length_checked);
				udp_packets_length_overflow =
				    udp_packets_length_checked = 0;
			}
			return (-1);
		}
		if (len + data != buf + bufix + buflen)
			debug("accepting packet with data after udp payload.");
	}

	usum = udp->uh_sum;
	udp->uh_sum = 0;

	sum = wrapsum(checksum((unsigned char *)udp, sizeof(*udp),
	    checksum(data, len, checksum((unsigned char *)&ip->ip_src,
	    2 * sizeof(ip->ip_src),
	    IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));

	udp_packets_seen++;
	if (usum && usum != sum) {
		udp_packets_bad_checksum++;
		if (udp_packets_seen > 4 &&
		    (udp_packets_seen / udp_packets_bad_checksum) < 2) {
			note("%d bad udp checksums in %d packets",
			    udp_packets_bad_checksum, udp_packets_seen);
			udp_packets_seen = udp_packets_bad_checksum = 0;
		}
		return (-1);
	}

	memcpy(&from->sin_port, &udp->uh_sport, sizeof(udp->uh_sport));

	return (ip_len + sizeof(*udp));
}

1	/* $OpenBSD: packet.c,v 1.9 2004/05/04 18:58:50 deraadt Exp $ */
2
3	/* Packet assembly code, originally contributed by Archie Cobbs. */
4
5	/*
6	* Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
7	* All rights reserved.
8	*
9	* Redistribution and use in source and binary forms, with or without
10	* modification, are permitted provided that the following conditions
11	* are met:
12	*
13	* 1. Redistributions of source code must retain the above copyright
14	* notice, this list of conditions and the following disclaimer.
15	* 2. Redistributions in binary form must reproduce the above copyright
16	* notice, this list of conditions and the following disclaimer in the
17	* documentation and/or other materials provided with the distribution.
18	* 3. Neither the name of The Internet Software Consortium nor the names
19	* of its contributors may be used to endorse or promote products derived
20	* from this software without specific prior written permission.
21	*
22	* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
23	* CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
24	* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
25	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
26	* DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
27	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
29	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
30	* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
31	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34	* SUCH DAMAGE.
35	*
36	* This software has been written for the Internet Software Consortium
37	* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
38	* Enterprises. To learn more about the Internet Software Consortium,
39	* see ``http://www.vix.com/isc''. To learn more about Vixie
40	* Enterprises, see ``http://www.vix.com''.
41	*/
42
43	#include <sys/cdefs.h>
44	__FBSDID("$FreeBSD$");
45
46	#include "dhcpd.h"
47
48	#include <netinet/in_systm.h>
49	#include <netinet/ip.h>
50	#include <netinet/udp.h>
51	#include <netinet/if_ether.h>
52
53	#define ETHER_HEADER_SIZE (ETHER_ADDR_LEN * 2 + sizeof(u_int16_t))
54
55	u_int32_t checksum(unsigned char *, unsigned, u_int32_t);
56	u_int32_t wrapsum(u_int32_t);
57
58	void assemble_ethernet_header(struct interface_info , unsigned char ,
59	int , struct hardware );
60	ssize_t decode_ethernet_header(struct interface_info , unsigned char ,
61	int bufix, struct hardware *);
62
63	u_int32_t
64	checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
65	{
66	int i;
67
68	/* Checksum all the pairs of bytes first... */
69	for (i = 0; i < (nbytes & ~1U); i += 2) {
70	sum += (u_int16_t)ntohs(((u_int16_t )(buf + i)));
71	if (sum > 0xFFFF)
72	sum -= 0xFFFF;
73	}
74
75	/*
76	* If there's a single byte left over, checksum it, too.
77	* Network byte order is big-endian, so the remaining byte is
78	* the high byte.
79	*/
80	if (i < nbytes) {
81	sum += buf[i] << 8;
82	if (sum > 0xFFFF)
83	sum -= 0xFFFF;
84	}
85
86	return (sum);
87	}
88
89	u_int32_t
90	wrapsum(u_int32_t sum)
91	{
92	sum = ~sum & 0xFFFF;
93	return (htons(sum));
94	}
95
96	void
97	assemble_hw_header(struct interface_info interface, unsigned char buf,
98	int bufix, struct hardware to)
99	{
100	struct ether_header eh;
101
102	if (to != NULL && to->hlen == 6) /* XXX */
103	memcpy(eh.ether_dhost, to->haddr, sizeof(eh.ether_dhost));
104	else
105	memset(eh.ether_dhost, 0xff, sizeof(eh.ether_dhost));
106	if (interface->hw_address.hlen == sizeof(eh.ether_shost))
107	memcpy(eh.ether_shost, interface->hw_address.haddr,
108	sizeof(eh.ether_shost));
109	else
110	memset(eh.ether_shost, 0x00, sizeof(eh.ether_shost));
111
112	eh.ether_type = htons(ETHERTYPE_IP);
113
114	memcpy(&buf[*bufix], &eh, ETHER_HEADER_SIZE);
115	*bufix += ETHER_HEADER_SIZE;
116	}
117
118	void
119	assemble_udp_ip_header(unsigned char buf, int bufix, u_int32_t from,
120	u_int32_t to, unsigned int port, unsigned char *data, int len)
121	{
122	struct ip ip;
123	struct udphdr udp;
124
125	ip.ip_v = 4;
126	ip.ip_hl = 5;
127	ip.ip_tos = IPTOS_LOWDELAY;
128	ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
129	ip.ip_id = 0;
130	ip.ip_off = 0;
131	ip.ip_ttl = 16;
132	ip.ip_p = IPPROTO_UDP;
133	ip.ip_sum = 0;
134	ip.ip_src.s_addr = from;
135	ip.ip_dst.s_addr = to;
136
137	ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
138
139	/*
140	* While the BPF -- used for broadcasts -- expects a "true" IP header
141	* with all the bytes in network byte order, the raw socket interface
142	* which is used for unicasts expects the ip_len field to be in host
143	* byte order. In both cases, the checksum has to be correct, so this
144	* is as good a place as any to turn the bytes around again.
145	*/
146	if (to != INADDR_BROADCAST)
147	ip.ip_len = ntohs(ip.ip_len);
148
149	memcpy(&buf[*bufix], &ip, sizeof(ip));
150	*bufix += sizeof(ip);
151
152	udp.uh_sport = htons(LOCAL_PORT); /* XXX */
153	udp.uh_dport = port; /* XXX */
154	udp.uh_ulen = htons(sizeof(udp) + len);
155	memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));
156
157	udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
158	checksum(data, len, checksum((unsigned char *)&ip.ip_src,
159	2 * sizeof(ip.ip_src),
160	IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
161
162	memcpy(&buf[*bufix], &udp, sizeof(udp));
163	*bufix += sizeof(udp);
164	}
165
166	ssize_t
167	decode_hw_header(unsigned char buf, int bufix, struct hardware from)
168	{
169	struct ether_header eh;
170
171	memcpy(&eh, buf + bufix, ETHER_HEADER_SIZE);
172
173	memcpy(from->haddr, eh.ether_shost, sizeof(eh.ether_shost));
174	from->htype = ARPHRD_ETHER;
175	from->hlen = sizeof(eh.ether_shost);
176
177	return (sizeof(eh));
178	}
179
180	ssize_t
181	decode_udp_ip_header(unsigned char buf, int bufix, struct sockaddr_in from,
182	unsigned char *data, int buflen)
183	{
184	struct ip *ip;
185	struct udphdr *udp;
186	u_int32_t ip_len = (buf[bufix] & 0xf) << 2;
187	u_int32_t sum, usum;
188	static int ip_packets_seen;
189	static int ip_packets_bad_checksum;
190	static int udp_packets_seen;
191	static int udp_packets_bad_checksum;
192	static int udp_packets_length_checked;
193	static int udp_packets_length_overflow;
194	int len = 0;
195
196	ip = (struct ip *)(buf + bufix);
197	udp = (struct udphdr *)(buf + bufix + ip_len);
198
199	/* Check the IP header checksum - it should be zero. */
200	ip_packets_seen++;
201	if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
202	ip_packets_bad_checksum++;
203	if (ip_packets_seen > 4 &&
204	(ip_packets_seen / ip_packets_bad_checksum) < 2) {
205	note("%d bad IP checksums seen in %d packets",
206	ip_packets_bad_checksum, ip_packets_seen);
207	ip_packets_seen = ip_packets_bad_checksum = 0;
208	}
209	return (-1);
210	}
211
212	if (ntohs(ip->ip_len) != buflen)
213	debug("ip length %d disagrees with bytes received %d.",
214	ntohs(ip->ip_len), buflen);
215
216	memcpy(&from->sin_addr, &ip->ip_src, 4);
217
218	/*
219	* Compute UDP checksums, including the ``pseudo-header'', the
220	* UDP header and the data. If the UDP checksum field is zero,
221	* we're not supposed to do a checksum.
222	*/
223	if (!data) {
224	data = buf + bufix + ip_len + sizeof(*udp);
225	len = ntohs(udp->uh_ulen) - sizeof(*udp);
226	udp_packets_length_checked++;
227	if (len + data > buf + bufix + buflen) {
228	udp_packets_length_overflow++;
229	if (udp_packets_length_checked > 4 &&
230	(udp_packets_length_checked /
231	udp_packets_length_overflow) < 2) {
232	note("%d udp packets in %d too long - dropped",
233	udp_packets_length_overflow,
234	udp_packets_length_checked);
235	udp_packets_length_overflow =
236	udp_packets_length_checked = 0;
237	}
238	return (-1);
239	}
240	if (len + data != buf + bufix + buflen)
241	debug("accepting packet with data after udp payload.");
242	}
243
244	usum = udp->uh_sum;
245	udp->uh_sum = 0;
246
247	sum = wrapsum(checksum((unsigned char )udp, sizeof(udp),
248	checksum(data, len, checksum((unsigned char *)&ip->ip_src,
249	2 * sizeof(ip->ip_src),
250	IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
251
252	udp_packets_seen++;
253	if (usum && usum != sum) {
254	udp_packets_bad_checksum++;
255	if (udp_packets_seen > 4 &&
256	(udp_packets_seen / udp_packets_bad_checksum) < 2) {
257	note("%d bad udp checksums in %d packets",
258	udp_packets_bad_checksum, udp_packets_seen);
259	udp_packets_seen = udp_packets_bad_checksum = 0;
260	}
261	return (-1);
262	}
263
264	memcpy(&from->sin_port, &udp->uh_sport, sizeof(udp->uh_sport));
265
266	return (ip_len + sizeof(*udp));
267	}

Gitorious