dhclient - Print out debug messages only when DEBUG is defined.
[dragonfly.git] / sbin / dhclient / packet.c
CommitLineData
4cada237 1/* $OpenBSD: src/sbin/dhclient/packet.c,v 1.13 2009/06/06 04:02:42 krw Exp $ */
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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 "dhcpd.h"
44
45#include <netinet/if_ether.h>
46#include <netinet/in_systm.h>
47#include <netinet/ip.h>
48#include <netinet/udp.h>
49
50#define ETHER_HEADER_SIZE (ETHER_ADDR_LEN * 2 + sizeof(u_int16_t))
51
52u_int32_t checksum(unsigned char *, unsigned, u_int32_t);
53u_int32_t wrapsum(u_int32_t);
54
55u_int32_t
56checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
57{
58 uint i;
59
60 /* Checksum all the pairs of bytes first... */
61 for (i = 0; i < (nbytes & ~1U); i += 2) {
62 sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
63 if (sum > 0xFFFF)
64 sum -= 0xFFFF;
65 }
66
67 /*
68 * If there's a single byte left over, checksum it, too.
69 * Network byte order is big-endian, so the remaining byte is
70 * the high byte.
71 */
72 if (i < nbytes) {
73 sum += buf[i] << 8;
74 if (sum > 0xFFFF)
75 sum -= 0xFFFF;
76 }
77
78 return (sum);
79}
80
81u_int32_t
82wrapsum(u_int32_t sum)
83{
84 sum = ~sum & 0xFFFF;
85 return (htons(sum));
86}
87
88void
89assemble_hw_header(unsigned char *buf, int *bufix, struct hardware *to)
90{
91 struct ether_header eh;
92
93 if (to != NULL && to->hlen == 6) /* XXX */
94 memcpy(eh.ether_dhost, to->haddr, sizeof(eh.ether_dhost));
95 else
96 memset(eh.ether_dhost, 0xff, sizeof(eh.ether_dhost));
97 if (ifi->hw_address.hlen == sizeof(eh.ether_shost))
98 memcpy(eh.ether_shost, ifi->hw_address.haddr,
99 sizeof(eh.ether_shost));
100 else
101 memset(eh.ether_shost, 0x00, sizeof(eh.ether_shost));
102
103 eh.ether_type = htons(ETHERTYPE_IP);
104
105 memcpy(&buf[*bufix], &eh, ETHER_HEADER_SIZE);
106 *bufix += ETHER_HEADER_SIZE;
107}
108
109void
110assemble_udp_ip_header(unsigned char *buf, int *bufix, u_int32_t from,
111 u_int32_t to, unsigned int port, unsigned char *data, int len)
112{
113 struct ip ip;
114 struct udphdr udp;
115
116 ip.ip_v = 4;
117 ip.ip_hl = 5;
118 ip.ip_tos = IPTOS_LOWDELAY;
119 ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
120 ip.ip_id = 0;
121 ip.ip_off = 0;
122 ip.ip_ttl = 16;
123 ip.ip_p = IPPROTO_UDP;
124 ip.ip_sum = 0;
125 ip.ip_src.s_addr = from;
126 ip.ip_dst.s_addr = to;
127
128 ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
129 memcpy(&buf[*bufix], &ip, sizeof(ip));
130 *bufix += sizeof(ip);
131
132 udp.uh_sport = htons(LOCAL_PORT); /* XXX */
133 udp.uh_dport = port; /* XXX */
134 udp.uh_ulen = htons(sizeof(udp) + len);
135 memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));
136
137 udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
138 checksum(data, len, checksum((unsigned char *)&ip.ip_src,
139 2 * sizeof(ip.ip_src),
140 IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
141
142 memcpy(&buf[*bufix], &udp, sizeof(udp));
143 *bufix += sizeof(udp);
144}
145
146ssize_t
147decode_hw_header(unsigned char *buf, int bufix, struct hardware *from)
148{
149 struct ether_header eh;
150
151 memcpy(&eh, buf + bufix, ETHER_HEADER_SIZE);
152
153 memcpy(from->haddr, eh.ether_shost, sizeof(eh.ether_shost));
154 from->htype = ARPHRD_ETHER;
155 from->hlen = sizeof(eh.ether_shost);
156
157 return (sizeof(eh));
158}
159
160ssize_t
161decode_udp_ip_header(unsigned char *buf, int bufix, struct sockaddr_in *from,
162 unsigned char *data, int buflen)
163{
164 struct ip *ip;
165 struct udphdr *udp;
166 u_int32_t ip_len = (buf[bufix] & 0xf) << 2;
167 u_int32_t sum, usum;
168 static int ip_packets_seen;
169 static int ip_packets_bad_checksum;
170 static int udp_packets_seen;
171 static int udp_packets_bad_checksum;
172 static int udp_packets_length_checked;
173 static int udp_packets_length_overflow;
174 int len = 0;
175
176 ip = (struct ip *)(buf + bufix);
177 udp = (struct udphdr *)(buf + bufix + ip_len);
178
179 /* Check the IP header checksum - it should be zero. */
180 ip_packets_seen++;
181 if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
182 ip_packets_bad_checksum++;
183 if (ip_packets_seen > 4 &&
184 (ip_packets_seen / ip_packets_bad_checksum) < 2) {
185 note("%d bad IP checksums seen in %d packets",
186 ip_packets_bad_checksum, ip_packets_seen);
187 ip_packets_seen = ip_packets_bad_checksum = 0;
188 }
189 return (-1);
190 }
191
4cada237 192#ifdef DEBUG
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193 if (ntohs(ip->ip_len) != buflen)
194 debug("ip length %d disagrees with bytes received %d.",
195 ntohs(ip->ip_len), buflen);
4cada237 196#endif
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197 memcpy(&from->sin_addr, &ip->ip_src, 4);
198
199 /*
200 * Compute UDP checksums, including the ``pseudo-header'', the
201 * UDP header and the data. If the UDP checksum field is zero,
202 * we're not supposed to do a checksum.
203 */
204 if (!data) {
205 data = buf + bufix + ip_len + sizeof(*udp);
206 len = ntohs(udp->uh_ulen) - sizeof(*udp);
207 udp_packets_length_checked++;
208 if (len + data > buf + bufix + buflen) {
209 udp_packets_length_overflow++;
210 if (udp_packets_length_checked > 4 &&
211 (udp_packets_length_checked /
212 udp_packets_length_overflow) < 2) {
213 note("%d udp packets in %d too long - dropped",
214 udp_packets_length_overflow,
215 udp_packets_length_checked);
216 udp_packets_length_overflow =
217 udp_packets_length_checked = 0;
218 }
219 return (-1);
220 }
4cada237 221#ifdef DEBUG
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222 if (len + data != buf + bufix + buflen)
223 debug("accepting packet with data after udp payload.");
4cada237 224#endif
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225 }
226
227 usum = udp->uh_sum;
228 udp->uh_sum = 0;
229
230 sum = wrapsum(checksum((unsigned char *)udp, sizeof(*udp),
231 checksum(data, len, checksum((unsigned char *)&ip->ip_src,
232 2 * sizeof(ip->ip_src),
233 IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
234
235 udp_packets_seen++;
236 if (usum && usum != sum) {
237 udp_packets_bad_checksum++;
238 if (udp_packets_seen > 4 &&
239 (udp_packets_seen / udp_packets_bad_checksum) < 2) {
240 note("%d bad udp checksums in %d packets",
241 udp_packets_bad_checksum, udp_packets_seen);
242 udp_packets_seen = udp_packets_bad_checksum = 0;
243 }
244 return (-1);
245 }
246
247 memcpy(&from->sin_port, &udp->uh_sport, sizeof(udp->uh_sport));
248
249 return (ip_len + sizeof(*udp));
250}