GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: usr.sbin/dhcrelay/bpf.c Lines: 0 98 0.0 %
Date: 2017-11-13 Branches: 0 54 0.0 %

Line Branch Exec Source
1
/*	$OpenBSD: bpf.c,v 1.19 2017/04/19 05:36:12 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
/*
65
 * Called by get_interface_list for each interface that's discovered.
66
 * Opens a packet filter for each interface and adds it to the select
67
 * mask.
68
 */
69
int
70
if_register_bpf(struct interface_info *info)
71
{
72
	int sock;
73
74
	/* Open the BPF device */
75
	if ((sock = open("/dev/bpf", O_RDWR)) == -1)
76
		fatal("Can't open bpf device");
77
78
	/* Set the BPF device to point at this interface. */
79
	if (ioctl(sock, BIOCSETIF, &info->ifr) == -1)
80
		fatal("Can't attach interface %s to bpf device", info->name);
81
82
	return (sock);
83
}
84
85
void
86
if_register_send(struct interface_info *info)
87
{
88
	/*
89
	 * If we're using the bpf API for sending and receiving, we
90
	 * don't need to register this interface twice.
91
	 */
92
	info->wfdesc = info->rfdesc;
93
}
94
95
/*
96
 * Packet filter program: 'ip and udp and dst port CLIENT_PORT'
97
 */
98
struct bpf_insn dhcp_bpf_sfilter[] = {
99
	/* Make sure this is an IP packet... */
100
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
101
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
102
103
	/* Make sure it's a UDP packet... */
104
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
105
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
106
107
	/* Make sure this isn't a fragment... */
108
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
109
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
110
111
	/* Get the IP header length... */
112
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
113
114
	/* Make sure it's to the right port... */
115
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
116
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_PORT, 0, 1),
117
118
	/* If we passed all the tests, ask for the whole packet. */
119
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
120
121
	/* Otherwise, drop it. */
122
	BPF_STMT(BPF_RET+BPF_K, 0),
123
};
124
125
int dhcp_bpf_sfilter_len = sizeof(dhcp_bpf_sfilter) / sizeof(struct bpf_insn);
126
127
/*
128
 * Packet filter program: 'ip and udp and dst port SERVER_PORT'
129
 */
130
struct bpf_insn dhcp_bpf_filter[] = {
131
	/* Make sure this is an IP packet... */
132
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
133
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
134
135
	/* Make sure it's a UDP packet... */
136
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
137
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
138
139
	/* Make sure this isn't a fragment... */
140
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
141
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
142
143
	/* Get the IP header length... */
144
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
145
146
	/* Make sure it's to the right port... */
147
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
148
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
149
150
	/* If we passed all the tests, ask for the whole packet. */
151
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
152
153
	/* Otherwise, drop it. */
154
	BPF_STMT(BPF_RET+BPF_K, 0),
155
};
156
157
int dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn);
158
159
/*
160
 * Packet filter program: encapsulated 'ip and udp and dst port SERVER_PORT'
161
 */
162
struct bpf_insn dhcp_bpf_efilter[] = {
163
	/* Make sure this is an encapsulated AF_INET packet... */
164
	BPF_STMT(BPF_LD + BPF_W + BPF_ABS, 0),
165
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, AF_INET << 24, 0, 10),
166
167
	/* Make sure it's an IPIP packet... */
168
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 21),
169
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_IPIP, 0, 8),
170
171
	/* Make sure it's an encapsulated UDP packet... */
172
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 41),
173
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
174
175
	/* Make sure this isn't a fragment... */
176
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 38),
177
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
178
179
	/* Get the IP header length... */
180
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 32),
181
182
	/* Make sure it's to the right port... */
183
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 34),
184
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
185
186
	/* If we passed all the tests, ask for the whole packet. */
187
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
188
189
	/* Otherwise, drop it. */
190
	BPF_STMT(BPF_RET+BPF_K, 0),
191
};
192
193
int dhcp_bpf_efilter_len = sizeof(dhcp_bpf_efilter) / sizeof(struct bpf_insn);
194
195
/*
196
 * Packet write filter program: 'ip and udp and src port CLIENT_PORT'
197
 */
198
struct bpf_insn dhcp_bpf_swfilter[] = {
199
	/* Make sure this is an IP packet... */
200
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
201
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
202
203
	/* Make sure it's a UDP packet... */
204
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
205
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
206
207
	/* Make sure this isn't a fragment... */
208
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
209
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
210
211
	/* Get the IP header length... */
212
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
213
214
	/* Make sure it's from the right port... */
215
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
216
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_PORT, 0, 1),
217
218
	/* If we passed all the tests, ask for the whole packet. */
219
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
220
221
	/* Otherwise, drop it. */
222
	BPF_STMT(BPF_RET+BPF_K, 0),
223
};
224
225
int dhcp_bpf_swfilter_len = sizeof(dhcp_bpf_swfilter) /
226
	sizeof(struct bpf_insn);
227
228
/*
229
 * Packet write filter program: 'ip and udp and src port SERVER_PORT'
230
 */
231
struct bpf_insn dhcp_bpf_wfilter[] = {
232
	/* Make sure this is an IP packet... */
233
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
234
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
235
236
	/* Make sure it's a UDP packet... */
237
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
238
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
239
240
	/* Make sure this isn't a fragment... */
241
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
242
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
243
244
	/* Get the IP header length... */
245
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
246
247
	/* Make sure it's from the right port... */
248
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
249
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
250
251
	/* If we passed all the tests, ask for the whole packet. */
252
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
253
254
	/* Otherwise, drop it. */
255
	BPF_STMT(BPF_RET+BPF_K, 0),
256
};
257
258
int dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn);
259
260
void
261
if_register_receive(struct interface_info *info, int isserver)
262
{
263
	struct bpf_version v;
264
	struct bpf_program p;
265
	int flag = 1, sz, cmplt = 0;
266
267
	/* Open a BPF device and hang it on this interface... */
268
	info->rfdesc = if_register_bpf(info);
269
270
	/* Make sure the BPF version is in range... */
271
	if (ioctl(info->rfdesc, BIOCVERSION, &v) == -1)
272
		fatal("Can't get BPF version");
273
274
	if (v.bv_major != BPF_MAJOR_VERSION ||
275
	    v.bv_minor < BPF_MINOR_VERSION)
276
		fatalx("Kernel BPF version out of range - recompile dhcpd!");
277
278
	/*
279
	 * Set immediate mode so that reads return as soon as a packet
280
	 * comes in, rather than waiting for the input buffer to fill
281
	 * with packets.
282
	 */
283
	if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) == -1)
284
		fatal("Can't set immediate mode on bpf device");
285
286
	/* make sure kernel fills in the source ethernet address */
287
	if (ioctl(info->rfdesc, BIOCSHDRCMPLT, &cmplt) == -1)
288
		fatal("Can't set header complete flag on bpf device");
289
290
	/* Get the required BPF buffer length from the kernel. */
291
	if (ioctl(info->rfdesc, BIOCGBLEN, &sz) == -1)
292
		fatal("Can't get bpf buffer length");
293
	info->rbuf_max = sz;
294
	info->rbuf = malloc(info->rbuf_max);
295
	if (!info->rbuf)
296
		fatalx("Can't allocate %lu bytes for bpf input buffer.",
297
		    (unsigned long)info->rbuf_max);
298
	info->rbuf_offset = 0;
299
	info->rbuf_len = 0;
300
301
	/* Set up the bpf filter program structure. */
302
	if (isserver) {
303
		p.bf_len = dhcp_bpf_sfilter_len;
304
		p.bf_insns = dhcp_bpf_sfilter;
305
	} else if (info->hw_address.htype == HTYPE_IPSEC_TUNNEL) {
306
		p.bf_len = dhcp_bpf_efilter_len;
307
		p.bf_insns = dhcp_bpf_efilter;
308
	} else {
309
		p.bf_len = dhcp_bpf_filter_len;
310
		p.bf_insns = dhcp_bpf_filter;
311
	}
312
	if (ioctl(info->rfdesc, BIOCSETF, &p) == -1)
313
		fatal("Can't install packet filter program");
314
315
	/* Set up the bpf write filter program structure. */
316
	if (isserver) {
317
		p.bf_len = dhcp_bpf_swfilter_len;
318
		p.bf_insns = dhcp_bpf_swfilter;
319
	} else {
320
		p.bf_len = dhcp_bpf_wfilter_len;
321
		p.bf_insns = dhcp_bpf_wfilter;
322
	}
323
324
	if (ioctl(info->rfdesc, BIOCSETWF, &p) == -1)
325
		fatal("Can't install write filter program");
326
327
	/* make sure these settings cannot be changed after dropping privs */
328
	if (ioctl(info->rfdesc, BIOCLOCK) == -1)
329
		fatal("Failed to lock bpf descriptor");
330
}
331
332
ssize_t
333
send_packet(struct interface_info *interface,
334
    struct dhcp_packet *raw, size_t len, struct packet_ctx *pc)
335
{
336
	unsigned char buf[256];
337
	struct iovec iov[2];
338
	ssize_t bufp;
339
	int result;
340
341
	result = -1;
342
343
	if (interface->hw_address.htype == HTYPE_IPSEC_TUNNEL) {
344
		socklen_t slen = pc->pc_dst.ss_len;
345
		result = sendto(server_fd, raw, len, 0,
346
		    (struct sockaddr *)&pc->pc_dst, slen);
347
		goto done;
348
	}
349
350
	/* Assemble the headers... */
351
	if ((bufp = assemble_hw_header(buf, sizeof(buf), 0, pc,
352
	    interface->hw_address.htype)) == -1)
353
		goto done;
354
	if ((bufp = assemble_udp_ip_header(buf, sizeof(buf), bufp, pc,
355
	    (unsigned char *)raw, len)) == -1)
356
		goto done;
357
358
	/* Fire it off */
359
	iov[0].iov_base = (char *)buf;
360
	iov[0].iov_len = bufp;
361
	iov[1].iov_base = (char *)raw;
362
	iov[1].iov_len = len;
363
364
	result = writev(interface->wfdesc, iov, 2);
365
 done:
366
	if (result == -1)
367
		log_warn("send_packet");
368
	return (result);
369
}
370
371
ssize_t
372
receive_packet(struct interface_info *interface, unsigned char *buf,
373
    size_t len, struct packet_ctx *pc)
374
{
375
	int length = 0;
376
	ssize_t offset = 0;
377
	struct bpf_hdr hdr;
378
379
	/*
380
	 * All this complexity is because BPF doesn't guarantee that
381
	 * only one packet will be returned at a time.  We're getting
382
	 * what we deserve, though - this is a terrible abuse of the BPF
383
	 * interface.  Sigh.
384
	 */
385
386
	/* Process packets until we get one we can return or until we've
387
	 * done a read and gotten nothing we can return...
388
	 */
389
	do {
390
		/* If the buffer is empty, fill it. */
391
		if (interface->rbuf_offset == interface->rbuf_len) {
392
			length = read(interface->rfdesc, interface->rbuf,
393
			    interface->rbuf_max);
394
			if (length <= 0)
395
				return (length);
396
			interface->rbuf_offset = 0;
397
			interface->rbuf_len = length;
398
		}
399
400
		/*
401
		 * If there isn't room for a whole bpf header, something
402
		 * went wrong, but we'll ignore it and hope it goes
403
		 * away... XXX
404
		 */
405
		if (interface->rbuf_len - interface->rbuf_offset <
406
		    sizeof(hdr)) {
407
			interface->rbuf_offset = interface->rbuf_len;
408
			continue;
409
		}
410
411
		/* Copy out a bpf header... */
412
		memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
413
		    sizeof(hdr));
414
415
		/*
416
		 * If the bpf header plus data doesn't fit in what's
417
		 * left of the buffer, stick head in sand yet again...
418
		 */
419
		if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen >
420
		    interface->rbuf_len) {
421
			interface->rbuf_offset = interface->rbuf_len;
422
			continue;
423
		}
424
425
		/*
426
		 * If the captured data wasn't the whole packet, or if
427
		 * the packet won't fit in the input buffer, all we can
428
		 * do is drop it.
429
		 */
430
		if (hdr.bh_caplen != hdr.bh_datalen) {
431
			interface->rbuf_offset += hdr.bh_hdrlen =
432
			    hdr.bh_caplen;
433
			continue;
434
		}
435
436
		/* Skip over the BPF header... */
437
		interface->rbuf_offset += hdr.bh_hdrlen;
438
439
		/* Decode the physical header... */
440
		offset = decode_hw_header(interface->rbuf,
441
		    interface->rbuf_len, interface->rbuf_offset, pc,
442
		    interface->hw_address.htype);
443
444
		/*
445
		 * If decoding or a physical layer checksum failed
446
		 * (dunno of any physical layer that supports this, but WTH),
447
		 * skip this packet.
448
		 */
449
		if (offset < 0) {
450
			interface->rbuf_offset += hdr.bh_caplen;
451
			continue;
452
		}
453
454
		/* Decode the IP and UDP headers... */
455
		offset = decode_udp_ip_header(interface->rbuf,
456
		    interface->rbuf_len, offset, pc);
457
458
		/* If the IP or UDP checksum was bad, skip the packet... */
459
		if (offset < 0) {
460
			interface->rbuf_offset += hdr.bh_caplen;
461
			continue;
462
		}
463
464
		hdr.bh_caplen -= offset - interface->rbuf_offset;
465
		interface->rbuf_offset = offset;
466
467
		/*
468
		 * If there's not enough room to stash the packet data,
469
		 * we have to skip it (this shouldn't happen in real
470
		 * life, though).
471
		 */
472
		if (hdr.bh_caplen > len) {
473
			interface->rbuf_offset += hdr.bh_caplen;
474
			continue;
475
		}
476
477
		/* Copy out the data in the packet... */
478
		memcpy(buf, interface->rbuf + interface->rbuf_offset,
479
		    hdr.bh_caplen);
480
		interface->rbuf_offset += hdr.bh_caplen;
481
		return (hdr.bh_caplen);
482
	} while (!length);
483
	return (0);
484
}