GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: usr.sbin/dhcrelay6/bpf.c Lines: 0 135 0.0 %
Date: 2017-11-13 Branches: 0 56 0.0 %

Line Branch Exec Source
1
/*	$OpenBSD: bpf.c,v 1.2 2017/04/19 05:36:13 natano Exp $ 	*/
2
3
/* BPF socket interface code, originally contributed by Archie Cobbs. */
4
5
/*
6
 * Copyright (c) 1995, 1996, 1998, 1999
7
 * The Internet Software Consortium.    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/types.h>
44
#include <sys/ioctl.h>
45
#include <sys/socket.h>
46
47
#include <net/bpf.h>
48
#include <net/if.h>
49
50
#include <netinet/in.h>
51
#include <netinet/if_ether.h>
52
53
#include <errno.h>
54
#include <fcntl.h>
55
#include <stdio.h>
56
#include <stdlib.h>
57
#include <string.h>
58
#include <unistd.h>
59
60
#include "dhcp.h"
61
#include "dhcpd.h"
62
#include "log.h"
63
64
ssize_t send_packet_layer3(struct interface_info *,
65
    void *, size_t, struct packet_ctx *);
66
67
/*
68
 * Called by get_interface_list for each interface that's discovered.
69
 * Opens a packet filter for each interface and adds it to the select
70
 * mask.
71
 */
72
int
73
if_register_bpf(struct interface_info *info)
74
{
75
	int sock;
76
77
	/* Open the BPF device */
78
	if ((sock = open("/dev/bpf", O_RDWR)) == -1)
79
		fatal("Can't open bpf device");
80
81
	/* Set the BPF device to point at this interface. */
82
	if (ioctl(sock, BIOCSETIF, &info->ifr) == -1)
83
		fatal("Can't attach interface %s to bpf device", info->name);
84
85
	return (sock);
86
}
87
88
void
89
if_register_send(struct interface_info *info)
90
{
91
	/*
92
	 * If we're using the bpf API for sending and receiving, we
93
	 * don't need to register this interface twice.
94
	 */
95
	info->wfdesc = info->rfdesc;
96
}
97
98
/* DHCPv6 BPF filters. */
99
100
/*
101
 * Packet filter program: 'ip6 and udp and dst port DHCP6_SERVER_PORT'
102
 */
103
struct bpf_insn dhcp6_bpf_sfilter[] = {
104
	/* Make sure this is an IP packet... */
105
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
106
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IPV6, 0, 5),
107
108
	/* Make sure this is an UDP packet. */
109
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 20),
110
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 3),
111
112
	/* Make sure it is the right port. */
113
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 56),
114
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP6_SERVER_PORT, 0, 1),
115
116
	/* If we passed all the tests, ask for the whole packet. */
117
	BPF_STMT(BPF_RET + BPF_K, (u_int)-1),
118
119
	/* Otherwise, drop it. */
120
	BPF_STMT(BPF_RET + BPF_K, 0),
121
};
122
123
int dhcp6_bpf_sfilter_len = sizeof(dhcp6_bpf_sfilter) / sizeof(struct bpf_insn);
124
125
/*
126
 * Packet filter program: 'ip6 and udp'
127
 */
128
struct bpf_insn dhcp6_bpf_wfilter[] = {
129
	/* Make sure this is an IP packet... */
130
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
131
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IPV6, 0, 3),
132
133
	/* Make sure this is an UDP packet. */
134
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 20),
135
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 1),
136
137
	/* If we passed all the tests, ask for the whole packet. */
138
	BPF_STMT(BPF_RET + BPF_K, (u_int)-1),
139
140
	/* Otherwise, drop it. */
141
	BPF_STMT(BPF_RET + BPF_K, 0),
142
};
143
144
int dhcp6_bpf_wfilter_len = sizeof(dhcp6_bpf_wfilter) / sizeof(struct bpf_insn);
145
146
147
void
148
if_register_receive(struct interface_info *info)
149
{
150
	struct bpf_version v;
151
	struct bpf_program p;
152
	int flag = 1, sz, cmplt = 0;
153
154
	/* Open a BPF device and hang it on this interface... */
155
	info->rfdesc = if_register_bpf(info);
156
157
	/* Make sure the BPF version is in range... */
158
	if (ioctl(info->rfdesc, BIOCVERSION, &v) == -1)
159
		fatal("Can't get BPF version");
160
161
	if (v.bv_major != BPF_MAJOR_VERSION ||
162
	    v.bv_minor < BPF_MINOR_VERSION)
163
		fatalx("Kernel BPF version out of range - recompile dhcpd!");
164
165
	/*
166
	 * Set immediate mode so that reads return as soon as a packet
167
	 * comes in, rather than waiting for the input buffer to fill
168
	 * with packets.
169
	 */
170
	if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) == -1)
171
		fatal("Can't set immediate mode on bpf device");
172
173
	/* make sure kernel fills in the source ethernet address */
174
	if (ioctl(info->rfdesc, BIOCSHDRCMPLT, &cmplt) == -1)
175
		fatal("Can't set header complete flag on bpf device");
176
177
	/* Get the required BPF buffer length from the kernel. */
178
	if (ioctl(info->rfdesc, BIOCGBLEN, &sz) == -1)
179
		fatal("Can't get bpf buffer length");
180
	info->rbuf_max = sz;
181
	info->rbuf = malloc(info->rbuf_max);
182
	if (!info->rbuf)
183
		fatalx("Can't allocate %lu bytes for bpf input buffer.",
184
		    (unsigned long)info->rbuf_max);
185
	info->rbuf_offset = 0;
186
	info->rbuf_len = 0;
187
188
	/* Set up the bpf filter program structure. */
189
	p.bf_len = dhcp6_bpf_sfilter_len;
190
	p.bf_insns = dhcp6_bpf_sfilter;
191
	if (ioctl(info->rfdesc, BIOCSETF, &p) == -1)
192
		fatal("Can't install packet filter program");
193
194
	/* Set up the bpf write filter program structure. */
195
	p.bf_len = dhcp6_bpf_wfilter_len;
196
	p.bf_insns = dhcp6_bpf_wfilter;
197
	if (ioctl(info->rfdesc, BIOCSETWF, &p) == -1)
198
		fatal("Can't install write filter program");
199
200
	/* Only get input packets. */
201
	flag = BPF_DIRECTION_OUT;
202
	if (ioctl(info->rfdesc, BIOCSDIRFILT , &flag) == -1)
203
		fatal("Can't set BPF direction capture");
204
205
	/* Drop them so they don't go up in the network stack. */
206
	flag = 1;
207
	if (ioctl(info->rfdesc, BIOCSFILDROP, &flag) == -1)
208
		fatal("Can't set BPF filter drop");
209
210
	/* make sure these settings cannot be changed after dropping privs */
211
	if (ioctl(info->rfdesc, BIOCLOCK) == -1)
212
		fatal("Failed to lock bpf descriptor");
213
}
214
215
ssize_t
216
send_packet_layer3(struct interface_info *intf, void *raw, size_t len,
217
    struct packet_ctx *pc)
218
{
219
	struct cmsghdr		*cmsg;
220
	ssize_t			 sendlen;
221
	struct msghdr		 msg;
222
	struct in6_pktinfo	*ipi6;
223
	struct sockaddr_storage	 ss;
224
	struct iovec		 iov[2];
225
	uint8_t			 cmsgbuf[
226
	    CMSG_SPACE(sizeof(struct in6_pktinfo))
227
	];
228
229
	log_debug("  sending %ld bytes to %s:%d via %s",
230
	    len, v6addr2str(&ss2sin6(&pc->pc_dst)->sin6_addr),
231
	    ntohs(ss2sin6(&pc->pc_dst)->sin6_port), intf->name);
232
233
	memset(&msg, 0, sizeof(msg));
234
	iov[0].iov_base = raw;
235
	iov[0].iov_len = len;
236
	msg.msg_iov = iov;
237
	msg.msg_iovlen = 1;
238
239
	ss = pc->pc_dst;
240
	ss2sin6(&ss)->sin6_scope_id = intf->index;
241
	msg.msg_name = &ss;
242
	msg.msg_namelen = ss.ss_len;
243
244
	/* If binded to multicast we should select an interface. */
245
	if (IN6_IS_ADDR_MULTICAST(&ss2sin6(&ss)->sin6_addr)) {
246
		memset(cmsgbuf, 0, sizeof(cmsgbuf));
247
		msg.msg_control = cmsgbuf;
248
		msg.msg_controllen = sizeof(cmsgbuf);
249
250
		/* Use the IPV6_PKTINFO to select the interface. */
251
		cmsg = (struct cmsghdr *)CMSG_FIRSTHDR(&msg);
252
		cmsg->cmsg_len = CMSG_LEN(sizeof(*ipi6));
253
		cmsg->cmsg_level = IPPROTO_IPV6;
254
		cmsg->cmsg_type = IPV6_PKTINFO;
255
256
		ipi6 = (struct in6_pktinfo *)CMSG_DATA(cmsg);
257
		ipi6->ipi6_ifindex = intf->index;
258
	}
259
260
	if ((sendlen = sendmsg(pc->pc_sd, &msg, 0)) == -1) {
261
		log_warn("  failed to send message");
262
		return -1;
263
	}
264
	if (sendlen < (ssize_t)len)
265
		log_warnx("  sent less bytes than expected (%ld < %ld)",
266
		    sendlen, len);
267
268
	return sendlen;
269
}
270
271
ssize_t
272
send_packet(struct interface_info *interface,
273
    void *raw, size_t len, struct packet_ctx *pc)
274
{
275
	unsigned char buf[256];
276
	struct iovec iov[2];
277
	int result, bufp = 0;
278
279
	if (pc->pc_sd != 0)
280
		return send_packet_layer3(interface, raw, len, pc);
281
282
	/* Assemble the headers... */
283
	assemble_hw_header(buf, &bufp, pc);
284
	assemble_udp_ip6_header(buf, &bufp, pc, raw, len);
285
286
	/* Fire it off */
287
	iov[0].iov_base = (char *)buf;
288
	iov[0].iov_len = bufp;
289
	iov[1].iov_base = (char *)raw;
290
	iov[1].iov_len = len;
291
292
	result = writev(interface->wfdesc, iov, 2);
293
	if (result == -1)
294
		log_warn("send_packet");
295
296
	return (result);
297
}
298
299
ssize_t
300
receive_packet(struct interface_info *interface, unsigned char *buf,
301
    size_t len, struct packet_ctx *pc)
302
{
303
	int length = 0, offset = 0;
304
	struct bpf_hdr hdr;
305
306
	/*
307
	 * All this complexity is because BPF doesn't guarantee that
308
	 * only one packet will be returned at a time.  We're getting
309
	 * what we deserve, though - this is a terrible abuse of the BPF
310
	 * interface.  Sigh.
311
	 */
312
313
	/* Process packets until we get one we can return or until we've
314
	 * done a read and gotten nothing we can return...
315
	 */
316
	do {
317
		/* If the buffer is empty, fill it. */
318
		if (interface->rbuf_offset == interface->rbuf_len) {
319
			length = read(interface->rfdesc, interface->rbuf,
320
			    interface->rbuf_max);
321
			if (length <= 0)
322
				return (length);
323
			interface->rbuf_offset = 0;
324
			interface->rbuf_len = length;
325
		}
326
327
		/*
328
		 * If there isn't room for a whole bpf header, something
329
		 * went wrong, but we'll ignore it and hope it goes
330
		 * away... XXX
331
		 */
332
		if (interface->rbuf_len - interface->rbuf_offset <
333
		    sizeof(hdr)) {
334
			interface->rbuf_offset = interface->rbuf_len;
335
			continue;
336
		}
337
338
		/* Copy out a bpf header... */
339
		memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
340
		    sizeof(hdr));
341
342
		/*
343
		 * If the bpf header plus data doesn't fit in what's
344
		 * left of the buffer, stick head in sand yet again...
345
		 */
346
		if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen >
347
		    interface->rbuf_len) {
348
			interface->rbuf_offset = interface->rbuf_len;
349
			continue;
350
		}
351
352
		/*
353
		 * If the captured data wasn't the whole packet, or if
354
		 * the packet won't fit in the input buffer, all we can
355
		 * do is drop it.
356
		 */
357
		if (hdr.bh_caplen != hdr.bh_datalen) {
358
			interface->rbuf_offset += hdr.bh_hdrlen =
359
			    hdr.bh_caplen;
360
			continue;
361
		}
362
363
		/* Skip over the BPF header... */
364
		interface->rbuf_offset += hdr.bh_hdrlen;
365
366
		/* Decode the physical header... */
367
		offset = decode_hw_header(interface->rbuf,
368
		    interface->rbuf_offset, pc);
369
370
		/*
371
		 * If a physical layer checksum failed (dunno of any
372
		 * physical layer that supports this, but WTH), skip
373
		 * this packet.
374
		 */
375
		if (offset < 0) {
376
			interface->rbuf_offset += hdr.bh_caplen;
377
			continue;
378
		}
379
		interface->rbuf_offset += offset;
380
		hdr.bh_caplen -= offset;
381
382
		/* Decode the IP and UDP headers... */
383
		offset = decode_udp_ip6_header(interface->rbuf,
384
		    interface->rbuf_offset, pc, hdr.bh_caplen);
385
386
		/* If the IP or UDP checksum was bad, skip the packet... */
387
		if (offset < 0) {
388
			interface->rbuf_offset += hdr.bh_caplen;
389
			continue;
390
		}
391
		interface->rbuf_offset += offset;
392
		hdr.bh_caplen -= offset;
393
394
		/*
395
		 * If there's not enough room to stash the packet data,
396
		 * we have to skip it (this shouldn't happen in real
397
		 * life, though).
398
		 */
399
		if (hdr.bh_caplen > len) {
400
			interface->rbuf_offset += hdr.bh_caplen;
401
			continue;
402
		}
403
404
		/* Copy out the data in the packet... */
405
		memcpy(buf, interface->rbuf + interface->rbuf_offset,
406
		    hdr.bh_caplen);
407
		interface->rbuf_offset += hdr.bh_caplen;
408
		return (hdr.bh_caplen);
409
	} while (!length);
410
	return (0);
411
}