aboutsummaryrefslogtreecommitdiffstats
path: root/pcap-bpf.c
blob: 5da81b141df9eee821feab655010e9d174c5a9b3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
/*
 * Copyright (c) 1993, 1994, 1995, 1996, 1998
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
#ifndef lint
static const char rcsid[] _U_ =
    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.74 2004-03-23 19:18:04 guy Exp $ (LBL)";
#endif

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/param.h>			/* optionally get BSD define */
#include <sys/time.h>
#include <sys/timeb.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/utsname.h>

#include <net/if.h>

#ifdef _AIX

/*
 * Make "pcap.h" not include "pcap-bpf.h"; we are going to include the
 * native OS version, as we need "struct bpf_config" from it.
 */
#define PCAP_DONT_INCLUDE_PCAP_BPF_H

#include <sys/types.h>

/*
 * Prevent bpf.h from redefining the DLT_ values to their
 * IFT_ values, as we're going to return the standard libpcap
 * values, not IBM's non-standard IFT_ values.
 */
#undef _AIX
#include <net/bpf.h>
#define _AIX

#include <net/if_types.h>		/* for IFT_ values */
#include <sys/sysconfig.h>
#include <sys/device.h>
#include <odmi.h>
#include <cf.h>

#ifdef __64BIT__
#define domakedev makedev64
#define getmajor major64
#define bpf_hdr bpf_hdr32
#else /* __64BIT__ */
#define domakedev makedev
#define getmajor major
#endif /* __64BIT__ */

#define BPF_NAME "bpf"
#define BPF_MINORS 4
#define DRIVER_PATH "/usr/lib/drivers"
#define BPF_NODE "/dev/bpf"
static int bpfloadedflag = 0;
static int odmlockid = 0;

#else /* _AIX */

#include <net/bpf.h>

#endif /* _AIX */

#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "pcap-int.h"

#ifdef HAVE_DAG_API
#include "pcap-dag.h"
#endif /* HAVE_DAG_API */

#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif

#include "gencode.h"	/* for "no_optimize" */

static int pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp);
static int pcap_set_datalink_bpf(pcap_t *p, int dlt);

static int
pcap_stats_bpf(pcap_t *p, struct pcap_stat *ps)
{
	struct bpf_stat s;

	/*
	 * "ps_recv" counts packets handed to the filter, not packets
	 * that passed the filter.  This includes packets later dropped
	 * because we ran out of buffer space.
	 *
	 * "ps_drop" counts packets dropped inside the BPF device
	 * because we ran out of buffer space.  It doesn't count
	 * packets dropped by the interface driver.  It counts
	 * only packets that passed the filter.
	 *
	 * Both statistics include packets not yet read from the kernel
	 * by libpcap, and thus not yet seen by the application.
	 */
	if (ioctl(p->fd, BIOCGSTATS, (caddr_t)&s) < 0) {
		snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCGSTATS: %s",
		    pcap_strerror(errno));
		return (-1);
	}

	ps->ps_recv = s.bs_recv;
	ps->ps_drop = s.bs_drop;
	return (0);
}

static int
pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
{
	int cc;
	int n = 0;
	register u_char *bp, *ep;
	struct bpf_insn *fcode;

	fcode = p->md.use_bpf ? NULL : p->fcode.bf_insns;
 again:
	/*
	 * Has "pcap_breakloop()" been called?
	 */
	if (p->break_loop) {
		/*
		 * Yes - clear the flag that indicates that it
		 * has, and return -2 to indicate that we were
		 * told to break out of the loop.
		 */
		p->break_loop = 0;
		return (-2);
	}
	cc = p->cc;
	if (p->cc == 0) {
		cc = read(p->fd, (char *)p->buffer, p->bufsize);
		if (cc < 0) {
			/* Don't choke when we get ptraced */
			switch (errno) {

			case EINTR:
				goto again;

#ifdef _AIX
			case EFAULT:
				/*
				 * Sigh.  More AIX wonderfulness.
				 *
				 * For some unknown reason the uiomove()
				 * operation in the bpf kernel extension
				 * used to copy the buffer into user 
				 * space sometimes returns EFAULT. I have
				 * no idea why this is the case given that
				 * a kernel debugger shows the user buffer 
				 * is correct. This problem appears to 
				 * be mostly mitigated by the memset of 
				 * the buffer before it is first used. 
				 * Very strange.... Shaun Clowes
				 *
				 * In any case this means that we shouldn't 
				 * treat EFAULT as a fatal error; as we
				 * don't have an API for returning
				 * a "some packets were dropped since
				 * the last packet you saw" indication,
				 * we just ignore EFAULT and keep reading.
				 */
				goto again;
#endif 
  
			case EWOULDBLOCK:
				return (0);
#if defined(sun) && !defined(BSD)
			/*
			 * Due to a SunOS bug, after 2^31 bytes, the kernel
			 * file offset overflows and read fails with EINVAL.
			 * The lseek() to 0 will fix things.
			 */
			case EINVAL:
				if (lseek(p->fd, 0L, SEEK_CUR) +
				    p->bufsize < 0) {
					(void)lseek(p->fd, 0L, SEEK_SET);
					goto again;
				}
				/* fall through */
#endif
			}
			snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "read: %s",
			    pcap_strerror(errno));
			return (-1);
		}
		bp = p->buffer;
	} else
		bp = p->bp;

	/*
	 * Loop through each packet.
	 */
#define bhp ((struct bpf_hdr *)bp)
	ep = bp + cc;
	while (bp < ep) {
		register int caplen, hdrlen;

		/*
		 * Has "pcap_breakloop()" been called?
		 * If so, return immediately - if we haven't read any
		 * packets, clear the flag and return -2 to indicate
		 * that we were told to break out of the loop, otherwise
		 * leave the flag set, so that the *next* call will break
		 * out of the loop without having read any packets, and
		 * return the number of packets we've processed so far.
		 */
		if (p->break_loop) {
			if (n == 0) {
				p->break_loop = 0;
				return (-2);
			} else {
				p->bp = bp;
				p->cc = ep - bp;
				return (n);
			}
		}

		caplen = bhp->bh_caplen;
		hdrlen = bhp->bh_hdrlen;
		/*
		 * Short-circuit evaluation: if using BPF filter
		 * in kernel, no need to do it now.
		 */
		if (fcode == NULL ||
		    bpf_filter(fcode, bp + hdrlen, bhp->bh_datalen, caplen)) {
#ifdef _AIX
			/*
			 * AIX's BPF returns seconds/nanoseconds time
			 * stamps, not seconds/microseconds time stamps.
			 *
			 * XXX - I'm guessing here that it's a "struct
			 * timestamp"; if not, this code won't compile,
			 * but, if not, you want to send us a bug report
			 * and fall back on using DLPI.  It's not as if
			 * BPF used to work right on AIX before this
			 * change; this change attempts to fix the fact
			 * that it didn't....
			 */
			bhp->bh_tstamp.tv_usec = bhp->bh_tstamp.tv_usec/1000;
#endif
			/*
			 * XXX A bpf_hdr matches a pcap_pkthdr.
			 */
			(*callback)(user, (struct pcap_pkthdr*)bp, bp + hdrlen);
			bp += BPF_WORDALIGN(caplen + hdrlen);
			if (++n >= cnt && cnt > 0) {
				p->bp = bp;
				p->cc = ep - bp;
				return (n);
			}
		} else {
			/*
			 * Skip this packet.
			 */
			bp += BPF_WORDALIGN(caplen + hdrlen);
		}
	}
#undef bhp
	p->cc = 0;
	return (n);
}

static int
pcap_inject_bpf(pcap_t *p, const void *buf, size_t size)
{
	int ret;

	/*
	 * Do a BIOCSHDRCMPLT, if defined, to turn that flag on, so
	 * the link-layer source address isn't forcibly overwritten?
	 * (Ignore errors?  Return errors if not "sorry, that ioctl
	 * isn't supported?)
	 *
	 * XXX - I seem to remember some packet-sending bug in some
	 * BSDs - check CVS log for "bpf.c"?
	 */
	ret = write(p->fd, buf, size);
	if (ret == -1) {
		snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
		    pcap_strerror(errno));
		return (-1);
	}
	return (ret);
}

#ifdef _AIX
static int 
bpf_odminit(char *errbuf)
{
	char *errstr;

	if (odm_initialize() == -1) {
		if (odm_err_msg(odmerrno, &errstr) == -1)
			errstr = "Unknown error";
		snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "bpf_load: odm_initialize failed: %s",
		    errstr);
		return (-1);
	}

	if ((odmlockid = odm_lock("/etc/objrepos/config_lock", ODM_WAIT)) == -1) {
		if (odm_err_msg(odmerrno, &errstr) == -1)
			errstr = "Unknown error";
		snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "bpf_load: odm_lock of /etc/objrepos/config_lock failed: %s",
		    errstr);
		return (-1);
	}

	return (0);
}

static int 
bpf_odmcleanup(char *errbuf)
{
	char *errstr;

	if (odm_unlock(odmlockid) == -1) {
		if (odm_err_msg(odmerrno, &errstr) == -1)
			errstr = "Unknown error";
		snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "bpf_load: odm_unlock failed: %s",
		    errstr);
		return (-1);
	}

	if (odm_terminate() == -1) {
		if (odm_err_msg(odmerrno, &errstr) == -1)
			errstr = "Unknown error";
		snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "bpf_load: odm_terminate failed: %s",
		    errstr);
		return (-1);
	}

	return (0);
}

static int
bpf_load(char *errbuf)
{
	long major;
	int *minors;
	int numminors, i, rc;
	char buf[1024];
	struct stat sbuf;
	struct bpf_config cfg_bpf;
	struct cfg_load cfg_ld;
	struct cfg_kmod cfg_km;

	/*
	 * This is very very close to what happens in the real implementation
	 * but I've fixed some (unlikely) bug situations.
	 */
	if (bpfloadedflag)
		return (0);

	if (bpf_odminit(errbuf) != 0)
		return (-1);

	major = genmajor(BPF_NAME);
	if (major == -1) {
		snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "bpf_load: genmajor failed: %s", pcap_strerror(errno));
		return (-1);
	}

	minors = getminor(major, &numminors, BPF_NAME);
	if (!minors) {
		minors = genminor("bpf", major, 0, BPF_MINORS, 1, 1);
		if (!minors) {
			snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "bpf_load: genminor failed: %s",
			    pcap_strerror(errno));
			return (-1);
		}
	}

	if (bpf_odmcleanup(errbuf))
		return (-1);

	rc = stat(BPF_NODE "0", &sbuf);
	if (rc == -1 && errno != ENOENT) {
		snprintf(errbuf, PCAP_ERRBUF_SIZE,
		    "bpf_load: can't stat %s: %s",
		    BPF_NODE "0", pcap_strerror(errno));
		return (-1);
	}

	if (rc == -1 || getmajor(sbuf.st_rdev) != major) {
		for (i = 0; i < BPF_MINORS; i++) {
			sprintf(buf, "%s%d", BPF_NODE, i);
			unlink(buf);
			if (mknod(buf, S_IRUSR | S_IFCHR, domakedev(major, i)) == -1) {
				snprintf(errbuf, PCAP_ERRBUF_SIZE,
				    "bpf_load: can't mknod %s: %s",
				    buf, pcap_strerror(errno));
				return (-1);
			}
		}
	}

	/* Check if the driver is loaded */
	memset(&cfg_ld, 0x0, sizeof(cfg_ld));
	cfg_ld.path = buf;
	sprintf(cfg_ld.path, "%s/%s", DRIVER_PATH, BPF_NAME);
	if ((sysconfig(SYS_QUERYLOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) ||
	    (cfg_ld.kmid == 0)) {
		/* Driver isn't loaded, load it now */
		if (sysconfig(SYS_SINGLELOAD, (void *)&cfg_ld, sizeof(cfg_ld)) == -1) {
			snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "bpf_load: could not load driver: %s",
			    strerror(errno));
			return (-1);
		}
	}

	/* Configure the driver */
	cfg_km.cmd = CFG_INIT;
	cfg_km.kmid = cfg_ld.kmid;
	cfg_km.mdilen = sizeof(cfg_bpf);
	cfg_km.mdiptr = (void *)&cfg_bpf; 
	for (i = 0; i < BPF_MINORS; i++) {
		cfg_bpf.devno = domakedev(major, i);
		if (sysconfig(SYS_CFGKMOD, (void *)&cfg_km, sizeof(cfg_km)) == -1) {
			snprintf(errbuf, PCAP_ERRBUF_SIZE,
			    "bpf_load: could not configure driver: %s",
			    strerror(errno));
			return (-1);
		}
	}
	
	bpfloadedflag = 1;

	return (0);
}
#endif

static inline int
bpf_open(pcap_t *p, char *errbuf)
{
	int fd;
	int n = 0;
	char device[sizeof "/dev/bpf0000000000"];

#ifdef _AIX
	/*
	 * Load the bpf driver, if it isn't already loaded,
	 * and create the BPF device entries, if they don't
	 * already exist.
	 */
	if (bpf_load(errbuf) == -1)
		return (-1);
#endif

	/*
	 * Go through all the minors and find one that isn't in use.
	 */
	do {
		(void)snprintf(device, sizeof(device), "/dev/bpf%d", n++);
		/*
		 * Initially try a read/write open (to allow the inject
		 * method to work).  If that fails due to permission
		 * issues, fall back to read-only.  This allows a
		 * non-root user to be granted specific access to pcap
		 * capabilities via file permissions.
		 *
		 * XXX - we should have an API that has a flag that
		 * controls whether to open read-only or read-write,
		 * so that denial of permission to send (or inability
		 * to send, if sending packets isn't supported on
		 * the device in question) can be indicated at open
		 * time.
		 */
		fd = open(device, O_RDWR);
		if (fd == -1 && errno == EACCES)
			fd = open(device, O_RDONLY);
	} while (fd < 0 && errno == EBUSY);

	/*
	 * XXX better message for all minors used
	 */
	if (fd < 0)
		snprintf(errbuf, PCAP_ERRBUF_SIZE, "(no devices found) %s: %s",
		    device, pcap_strerror(errno));

	return (fd);
}

static void
pcap_close_bpf(pcap_t *p)
{
	if (p->buffer != NULL)
		free(p->buffer);
	if (p->fd >= 0)
		close(p->fd);
}

/*
 * We include the OS's <net/bpf.h>, not our "pcap-bpf.h", so we probably
 * don't get DLT_DOCSIS defined.
 */
#ifndef DLT_DOCSIS
#define DLT_DOCSIS	143
#endif

/*
 * XXX - on AIX, IBM's tcpdump (and perhaps the incompatible-with-everybody-
 * else's libpcap in AIX 5.1) appears to forcibly load the BPF driver
 * if it's not already loaded, and to create the BPF devices if they
 * don't exist.
 *
 * It'd be nice if we could do the same, although the code to do so
 * might be version-dependent, alas (the way to do it isn't necessarily
 * documented).
 */
pcap_t *
pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
    char *ebuf)
{
	int fd;
	struct ifreq ifr;
	struct bpf_version bv;
#ifdef BIOCGDLTLIST
	struct bpf_dltlist bdl;
#endif
	u_int v;
	pcap_t *p;
	struct utsname osinfo;

#ifdef HAVE_DAG_API
	if (strstr(device, "dag")) {
		return dag_open_live(device, snaplen, promisc, to_ms, ebuf);
	}
#endif /* HAVE_DAG_API */

#ifdef BIOCGDLTLIST
	memset(&bdl, 0, sizeof(bdl));
#endif

	p = (pcap_t *)malloc(sizeof(*p));
	if (p == NULL) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
		    pcap_strerror(errno));
		return (NULL);
	}
	memset(p, 0, sizeof(*p));
	fd = bpf_open(p, ebuf);
	if (fd < 0)
		goto bad;

	p->fd = fd;
	p->snapshot = snaplen;

	if (ioctl(fd, BIOCVERSION, (caddr_t)&bv) < 0) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCVERSION: %s",
		    pcap_strerror(errno));
		goto bad;
	}
	if (bv.bv_major != BPF_MAJOR_VERSION ||
	    bv.bv_minor < BPF_MINOR_VERSION) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE,
		    "kernel bpf filter out of date");
		goto bad;
	}

	/*
	 * Try finding a good size for the buffer; 32768 may be too
	 * big, so keep cutting it in half until we find a size
	 * that works, or run out of sizes to try.  If the default
	 * is larger, don't make it smaller.
	 *
	 * XXX - there should be a user-accessible hook to set the
	 * initial buffer size.
	 */
	if ((ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) || v < 32768)
		v = 32768;
	for ( ; v != 0; v >>= 1) {
		/* Ignore the return value - this is because the call fails
		 * on BPF systems that don't have kernel malloc.  And if
		 * the call fails, it's no big deal, we just continue to
		 * use the standard buffer size.
		 */
		(void) ioctl(fd, BIOCSBLEN, (caddr_t)&v);

		(void)strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
		if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) >= 0)
			break;	/* that size worked; we're done */

		if (errno != ENOBUFS) {
			snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSETIF: %s: %s",
			    device, pcap_strerror(errno));
			goto bad;
		}
	}

	if (v == 0) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE,
			 "BIOCSBLEN: %s: No buffer size worked", device);
		goto bad;
	}

	/* Get the data link layer type. */
	if (ioctl(fd, BIOCGDLT, (caddr_t)&v) < 0) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGDLT: %s",
		    pcap_strerror(errno));
		goto bad;
	}
#ifdef _AIX
	/*
	 * AIX's BPF returns IFF_ types, not DLT_ types, in BIOCGDLT.
	 */
	switch (v) {

	case IFT_ETHER:
	case IFT_ISO88023:
		v = DLT_EN10MB;
		break;

	case IFT_FDDI:
		v = DLT_FDDI;
		break;

	case IFT_ISO88025:
		v = DLT_IEEE802;
		break;

	case IFT_LOOP:
		v = DLT_NULL;
		break;

	default:
		/*
		 * We don't know what to map this to yet.
		 */
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "unknown interface type %u",
		    v);
		goto bad;
	}
#endif
#if _BSDI_VERSION - 0 >= 199510
	/* The SLIP and PPP link layer header changed in BSD/OS 2.1 */
	switch (v) {

	case DLT_SLIP:
		v = DLT_SLIP_BSDOS;
		break;

	case DLT_PPP:
		v = DLT_PPP_BSDOS;
		break;

	case 11:	/*DLT_FR*/
		v = DLT_FRELAY;
		break;

	case 12:	/*DLT_C_HDLC*/
		v = DLT_CHDLC;
		break;
	}
#endif
	p->linktype = v;

#ifdef BIOCGDLTLIST
	/*
	 * We know the default link type -- now determine all the DLTs
	 * this interface supports.  If this fails with EINVAL, it's
	 * not fatal; we just don't get to use the feature later.
	 */
	if (ioctl(fd, BIOCGDLTLIST, (caddr_t)&bdl) == 0) {
		u_int i;
		int is_ethernet;

		bdl.bfl_list = (u_int *) malloc(sizeof(u_int) * bdl.bfl_len + 1);
		if (bdl.bfl_list == NULL) {
			(void)snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
			    pcap_strerror(errno));
			goto bad;
		}

		if (ioctl(fd, BIOCGDLTLIST, (caddr_t)&bdl) < 0) {
			(void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
			    "BIOCGDLTLIST: %s", pcap_strerror(errno));
			free(bdl.bfl_list);
			goto bad;
		}

		/*
		 * OK, for real Ethernet devices, add DLT_DOCSIS to the
		 * list, so that an application can let you choose it,
		 * in case you're capturing DOCSIS traffic that a Cisco
		 * Cable Modem Termination System is putting out onto
		 * an Ethernet (it doesn't put an Ethernet header onto
		 * the wire, it puts raw DOCSIS frames out on the wire
		 * inside the low-level Ethernet framing).
		 *
		 * A "real Ethernet device" is defined here as a device
		 * that has a link-layer type of DLT_EN10MB and that has
		 * no alternate link-layer types; that's done to exclude
		 * 802.11 interfaces (which might or might not be the
		 * right thing to do, but I suspect it is - Ethernet <->
		 * 802.11 bridges would probably badly mishandle frames
		 * that don't have Ethernet headers).
		 */
		if (p->linktype == DLT_EN10MB) {
			is_ethernet = 1;
			for (i = 0; i < bdl.bfl_len; i++) {
				if (bdl.bfl_list != DLT_EN10MB) {
					is_ethernet = 0;
					break;
				}
			}
			if (is_ethernet) {
				/*
				 * We reserved one more slot at the end of
				 * the list.
				 */
				bdl.bfl_list[bdl.bfl_len] = DLT_DOCSIS;
				bdl.bfl_len++;
			}
		}
		p->dlt_count = bdl.bfl_len;
		p->dlt_list = bdl.bfl_list;
	} else {
		if (errno != EINVAL) {
			(void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
			    "BIOCGDLTLIST: %s", pcap_strerror(errno));
			goto bad;
		}
	}
#endif

	/*
	 * If this is an Ethernet device, and we don't have a DLT_ list,
	 * give it a list with DLT_EN10MB and DLT_DOCSIS.  (That'd give
	 * 802.11 interfaces DLT_DOCSIS, which isn't the right thing to
	 * do, but there's not much we can do about that without finding
	 * some other way of determining whether it's an Ethernet or 802.11
	 * device.)
	 */
	if (p->linktype == DLT_EN10MB && p->dlt_count == 0) {
		p->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
		/*
		 * If that fails, just leave the list empty.
		 */
		if (p->dlt_list != NULL) {
			p->dlt_list[0] = DLT_EN10MB;
			p->dlt_list[1] = DLT_DOCSIS;
			p->dlt_count = 2;
		}
	}
		
	/* set timeout */
	if (to_ms != 0) {
		/*
		 * XXX - is this seconds/nanoseconds in AIX?
		 * (Treating it as such doesn't fix the timeout
		 * problem described below.)
		 */
		struct timeval to;
		to.tv_sec = to_ms / 1000;
		to.tv_usec = (to_ms * 1000) % 1000000;
		if (ioctl(p->fd, BIOCSRTIMEOUT, (caddr_t)&to) < 0) {
			snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCSRTIMEOUT: %s",
			    pcap_strerror(errno));
			goto bad;
		}
	}

#ifdef _AIX
#ifdef	BIOCIMMEDIATE
	/*
	 * Darren Reed notes that
	 *
	 *	On AIX (4.2 at least), if BIOCIMMEDIATE is not set, the
	 *	timeout appears to be ignored and it waits until the buffer
	 *	is filled before returning.  The result of not having it
	 *	set is almost worse than useless if your BPF filter
	 *	is reducing things to only a few packets (i.e. one every
	 *	second or so).
	 *
	 * so we turn BIOCIMMEDIATE mode on if this is AIX.
	 *
	 * We don't turn it on for other platforms, as that means we
	 * get woken up for every packet, which may not be what we want;
	 * in the Winter 1993 USENIX paper on BPF, they say:
	 *
	 *	Since a process might want to look at every packet on a
	 *	network and the time between packets can be only a few
	 *	microseconds, it is not possible to do a read system call
	 *	per packet and BPF must collect the data from several
	 *	packets and return it as a unit when the monitoring
	 *	application does a read.
	 *
	 * which I infer is the reason for the timeout - it means we
	 * wait that amount of time, in the hopes that more packets
	 * will arrive and we'll get them all with one read.
	 *
	 * Setting BIOCIMMEDIATE mode on FreeBSD (and probably other
	 * BSDs) causes the timeout to be ignored.
	 *
	 * On the other hand, some platforms (e.g., Linux) don't support
	 * timeouts, they just hand stuff to you as soon as it arrives;
	 * if that doesn't cause a problem on those platforms, it may
	 * be OK to have BIOCIMMEDIATE mode on BSD as well.
	 *
	 * (Note, though, that applications may depend on the read
	 * completing, even if no packets have arrived, when the timeout
	 * expires, e.g. GUI applications that have to check for input
	 * while waiting for packets to arrive; a non-zero timeout
	 * prevents "select()" from working right on FreeBSD and
	 * possibly other BSDs, as the timer doesn't start until a
	 * "read()" is done, so the timer isn't in effect if the
	 * application is blocked on a "select()", and the "select()"
	 * doesn't get woken up for a BPF device until the buffer
	 * fills up.)
	 */
	v = 1;
	if (ioctl(p->fd, BIOCIMMEDIATE, &v) < 0) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCIMMEDIATE: %s",
		    pcap_strerror(errno));
		goto bad;
	}
#endif	/* BIOCIMMEDIATE */
#endif	/* _AIX */

	if (promisc) {
		/* set promiscuous mode, okay if it fails */
		if (ioctl(p->fd, BIOCPROMISC, NULL) < 0) {
			snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCPROMISC: %s",
			    pcap_strerror(errno));
		}
	}

	if (ioctl(fd, BIOCGBLEN, (caddr_t)&v) < 0) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "BIOCGBLEN: %s",
		    pcap_strerror(errno));
		goto bad;
	}
	p->bufsize = v;
	p->buffer = (u_char *)malloc(p->bufsize);
	if (p->buffer == NULL) {
		snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
		    pcap_strerror(errno));
		goto bad;
	}
#ifdef _AIX
	/* For some strange reason this seems to prevent the EFAULT 
	 * problems we have experienced from AIX BPF. */
	memset(p->buffer, 0x0, p->bufsize);
#endif

	/*
	 * On most BPF platforms, either you can do a "select()" or
	 * "poll()" on a BPF file descriptor and it works correctly,
	 * or you can do it and it will return "readable" if the
	 * hold buffer is full but not if the timeout expires *and*
	 * a non-blocking read will, if the hold buffer is empty
	 * but the store buffer isn't empty, rotate the buffers
	 * and return what packets are available.
	 *
	 * In the latter case, the fact that a non-blocking read
	 * will give you the available packets means you can work
	 * around the failure of "select()" and "poll()" to wake up
	 * and return "readable" when the timeout expires by using
	 * the timeout as the "select()" or "poll()" timeout, putting
	 * the BPF descriptor into non-blocking mode, and read from
	 * it regardless of whether "select()" reports it as readable
	 * or not.
	 *
	 * However, in FreeBSD 4.3 and 4.4, "select()" and "poll()"
	 * won't wake up and return "readable" if the timer expires
	 * and non-blocking reads return EWOULDBLOCK if the hold
	 * buffer is empty, even if the store buffer is non-empty.
	 *
	 * This means the workaround in question won't work.
	 *
	 * Therefore, on FreeBSD 4.3 and 4.4, we set "p->selectable_fd"
	 * to -1, which means "sorry, you can't use 'select()' or 'poll()'
	 * here".  On all other BPF platforms, we set it to the FD for
	 * the BPF device; in NetBSD, OpenBSD, and Darwin, a non-blocking
	 * read will, if the hold buffer is empty and the store buffer
	 * isn't empty, rotate the buffers and return what packets are
	 * there (and in sufficiently recent versions of OpenBSD
	 * "select()" and "poll()" should work correctly).
	 *
	 * XXX - what about AIX?
	 */
	if (uname(&osinfo) == 0) {
		/*
		 * We can check what OS this is.
		 */
		if (strcmp(osinfo.sysname, "FreeBSD") == 0 &&
		    (strcmp(osinfo.release, "4.3") == 0 ||
		     strcmp(osinfo.release, "4.4") == 0))
			p->selectable_fd = -1;
		else
			p->selectable_fd = p->fd;
	} else {
		/*
		 * We can't find out what OS this is, so assume we can
		 * do a "select()" or "poll()".
		 */
		p->selectable_fd = p->fd;
	}

	p->read_op = pcap_read_bpf;
	p->inject_op = pcap_inject_bpf;
	p->setfilter_op = pcap_setfilter_bpf;
	p->set_datalink_op = pcap_set_datalink_bpf;
	p->getnonblock_op = pcap_getnonblock_fd;
	p->setnonblock_op = pcap_setnonblock_fd;
	p->stats_op = pcap_stats_bpf;
	p->close_op = pcap_close_bpf;

	return (p);
 bad:
	(void)close(fd);
	if (p->dlt_list != NULL)
		free(p->dlt_list);
	free(p);
	return (NULL);
}

int
pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
{
#ifdef HAVE_DAG_API
	if (dag_platform_finddevs(alldevsp, errbuf) < 0)
		return (-1);
#endif /* HAVE_DAG_API */

	return (0);
}

static int
pcap_setfilter_bpf(pcap_t *p, struct bpf_program *fp)
{
	/*
	 * It looks that BPF code generated by gen_protochain() is not
	 * compatible with some of kernel BPF code (for example BSD/OS 3.1).
	 * Take a safer side for now.
	 */
	if (no_optimize) {
		/*
		 * XXX - what if we already have a filter in the kernel?
		 */
		if (install_bpf_program(p, fp) < 0)
			return (-1);
		p->md.use_bpf = 0;	/* filtering in userland */
		return (0);
	}

	/*
	 * Free any user-mode filter we might happen to have installed.
	 */
	pcap_freecode(&p->fcode);

	/*
	 * Try to install the kernel filter.
	 */
	if (ioctl(p->fd, BIOCSETF, (caddr_t)fp) < 0) {
		snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "BIOCSETF: %s",
		    pcap_strerror(errno));
		return (-1);
	}
	p->md.use_bpf = 1;	/* filtering in the kernel */
	return (0);
}

static int
pcap_set_datalink_bpf(pcap_t *p, int dlt)
{
#ifdef BIOCSDLT
	if (ioctl(p->fd, BIOCSDLT, &dlt) == -1) {
		(void) snprintf(p->errbuf, sizeof(p->errbuf),
		    "Cannot set DLT %d: %s", dlt, strerror(errno));
		return (-1);
	}
#endif
	return (0);
}