summaryrefslogtreecommitdiffstats
path: root/src/libnetfilter_queue.c
blob: 7e623175a528978d23ea55ee2c982394442c3009 (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
/* libnetfilter_queue.c: generic library for access to nf_queue
 *
 * (C) 2005 by Harald Welte <laforge@gnumonks.org>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 
 *  as published by the Free Software Foundation
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  2006-01-23 Andreas Florath <andreas@florath.net>
 *	Fix __set_verdict() that it can now handle payload.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
#include <errno.h>
#include <netinet/in.h>
#include <sys/socket.h>

#include <libnfnetlink/libnfnetlink.h>
#include <libnetfilter_queue/libnetfilter_queue.h>

/**
 * \mainpage
 *
 * libnetfilter_queue is a userspace library providing an API to packets that
 * have been queued by the kernel packet filter. It is is part of a system that
 * deprecates the old ip_queue / libipq mechanism.
 *
 * libnetfilter_queue homepage is:
 * 	http://netfilter.org/projects/libnetfilter_queue/
 *
 * \section Dependencies
 * libnetfilter_queue requires libnfnetlink and a kernel that includes the
 * nfnetlink_queue subsystem (i.e. 2.6.14 or later).
 *
 * \section Main Features
 *  - receiving queued packets from the kernel nfnetlink_queue subsystem
 *  - issuing verdicts and/or reinjecting altered packets to the kernel
 *  nfnetlink_queue subsystem
 * 
 * \section Git Tree
 * The current development version of libnetfilter_queue can be accessed
 * at https://git.netfilter.org/cgi-bin/gitweb.cgi?p=libnetfilter_queue.git;a=summary.
 *
 * \section Privileges
 * You need the CAP_NET_ADMIN capability in order to allow your application
 * to receive from and to send packets to kernel-space.
 *
 * \section Using libnetfilter_queue
 * 
 * To write your own program using libnetfilter_queue, you should start by reading
 * the doxygen documentation (start by \link LibrarySetup \endlink page) and nfqnl_test.c source file.
 * 
 */

struct nfq_handle
{
	struct nfnl_handle *nfnlh;
	struct nfnl_subsys_handle *nfnlssh;
	struct nfq_q_handle *qh_list;
};

struct nfq_q_handle
{
	struct nfq_q_handle *next;
	struct nfq_handle *h;
	u_int16_t id;

	nfq_callback *cb;
	void *data;
};

struct nfq_data {
	struct nfattr **data;
};

int nfq_errno;

/***********************************************************************
 * low level stuff 
 ***********************************************************************/

static void del_qh(struct nfq_q_handle *qh)
{
	struct nfq_q_handle *cur_qh, *prev_qh = NULL;

	for (cur_qh = qh->h->qh_list; cur_qh; cur_qh = cur_qh->next) {
		if (cur_qh == qh) {
			if (prev_qh)
				prev_qh->next = qh->next;
			else
				qh->h->qh_list = qh->next;
			return;
		}
		prev_qh = cur_qh;
	}
}

static void add_qh(struct nfq_q_handle *qh)
{
	qh->next = qh->h->qh_list;
	qh->h->qh_list = qh;
}

static struct nfq_q_handle *find_qh(struct nfq_handle *h, u_int16_t id)
{
	struct nfq_q_handle *qh;

	for (qh = h->qh_list; qh; qh = qh->next) {
		if (qh->id == id)
			return qh;
	}
	return NULL;
}

/* build a NFQNL_MSG_CONFIG message */
	static int
__build_send_cfg_msg(struct nfq_handle *h, u_int8_t command,
		u_int16_t queuenum, u_int16_t pf)
{
	union {
		char buf[NFNL_HEADER_LEN
			+NFA_LENGTH(sizeof(struct nfqnl_msg_config_cmd))];
		struct nlmsghdr nmh;
	} u;
	struct nfqnl_msg_config_cmd cmd;

	nfnl_fill_hdr(h->nfnlssh, &u.nmh, 0, AF_UNSPEC, queuenum,
			NFQNL_MSG_CONFIG, NLM_F_REQUEST|NLM_F_ACK);

	cmd.command = command;
	cmd.pf = htons(pf);
	nfnl_addattr_l(&u.nmh, sizeof(u), NFQA_CFG_CMD, &cmd, sizeof(cmd));

	return nfnl_query(h->nfnlh, &u.nmh);
}

static int __nfq_rcv_pkt(struct nlmsghdr *nlh, struct nfattr *nfa[],
		void *data)
{
	struct nfgenmsg *nfmsg = NLMSG_DATA(nlh);
	struct nfq_handle *h = data;
	u_int16_t queue_num = ntohs(nfmsg->res_id);
	struct nfq_q_handle *qh = find_qh(h, queue_num);
	struct nfq_data nfqa;

	if (!qh)
		return -ENODEV;

	if (!qh->cb)
		return -ENODEV;

	nfqa.data = nfa;

	return qh->cb(qh, nfmsg, &nfqa, qh->data);
}

static struct nfnl_callback pkt_cb = {
	.call		= &__nfq_rcv_pkt,
	.attr_count	= NFQA_MAX,
};

/* public interface */

struct nfnl_handle *nfq_nfnlh(struct nfq_handle *h)
{
	return h->nfnlh;
}

/**
 *
 * \defgroup Queue Queue handling
 *
 * Once libnetfilter_queue library has been initialised (See 
 * \link LibrarySetup \endlink), it is possible to bind the program to a
 * specific queue. This can be done by using nfq_create_queue().
 *
 * The queue can then be tuned via nfq_set_mode() or nfq_set_queue_maxlen().
 * 
 * Here's a little code snippet that create queue numbered 0:
 * \verbatim
	printf("binding this socket to queue '0'\n");
	qh = nfq_create_queue(h,  0, &cb, NULL);
	if (!qh) {
		fprintf(stderr, "error during nfq_create_queue()\n");
		exit(1);
	}

	printf("setting copy_packet mode\n");
	if (nfq_set_mode(qh, NFQNL_COPY_PACKET, 0xffff) < 0) {
		fprintf(stderr, "can't set packet_copy mode\n");
		exit(1);
	}
\endverbatim
 *
 * Next step is the handling of incoming packets which can be done via a loop:
 *
 * \verbatim
	fd = nfq_fd(h);

	while ((rv = recv(fd, buf, sizeof(buf), 0)) && rv >= 0) {
		printf("pkt received\n");
		nfq_handle_packet(h, buf, rv);
	}
\endverbatim
 * When the decision on a packet has been choosed, the verdict has to be given
 * by calling nfq_set_verdict() or nfq_set_verdict_mark().
 *
 * Data and information about the packet can be fetch by using message parsing
 * functions (See \link Parsing \endlink).
 * @{
 */

/**
 * nfq_fd - get the file descriptor associated with the nfqueue handler
 * \param h Netfilter queue connection handle obtained via call to nfq_open()
 *
 * \return a file descriptor for the netlink connection associated with the
 * given queue connection handle. The file descriptor can then be used for
 * receiving the queued packets for processing.
 *
  * This function returns a file descriptor that can be used for communication
 * over the netlink connection associated with the given queue connection
 * handle.
 */
int nfq_fd(struct nfq_handle *h)
{
	return nfnl_fd(nfq_nfnlh(h));
}

/**
 * @}
 */

/**
 * \defgroup LibrarySetup Library setup
 *
 * Library initialisation is made in two steps.
 *
 * First step is to call nfq_open() to open a NFQUEUE handler. 
 *
 * Second step is to tell the kernel that userspace queueing is handle by
 * NFQUEUE for the selected protocol. This is made by calling nfq_unbind_pf()
 * and nfq_bind_pf() with protocol information. The idea behind this is to
 * enable simultaneously loaded modules to be used for queuing.
 *
 * Here's a little code snippet that bind with AF_INET:
 * \verbatim
	h = nfq_open();
	if (!h) {
		fprintf(stderr, "error during nfq_open()\n");
		exit(1);
	}

	printf("unbinding existing nf_queue handler for AF_INET (if any)\n");
	if (nfq_unbind_pf(h, AF_INET) < 0) {
		fprintf(stderr, "error during nfq_unbind_pf()\n");
		exit(1);
	}

	printf("binding nfnetlink_queue as nf_queue handler for AF_INET\n");
	if (nfq_bind_pf(h, AF_INET) < 0) {
		fprintf(stderr, "error during nfq_bind_pf()\n");
		exit(1);
	}
\endverbatim
 * Once this is done, you can setup and use a \link Queue \endlink.
 * @{
 */

/**
 * nfq_open - open a nfqueue handler
 *
 * This function obtains a netfilter queue connection handle. When you are
 * finished with the handle returned by this function, you should destroy
 * it by calling nfq_close(). A new netlink connection is obtained internally
 * and associated with the queue connection handle returned.
 *
 * \return a pointer to a new queue handle or NULL on failure.
 */
struct nfq_handle *nfq_open(void)
{
	struct nfnl_handle *nfnlh = nfnl_open();
	struct nfq_handle *qh;

	if (!nfnlh)
		return NULL;

	/* unset netlink sequence tracking by default */
	nfnl_unset_sequence_tracking(nfnlh);

	qh = nfq_open_nfnl(nfnlh);
	if (!qh)
		nfnl_close(nfnlh);

	return qh;
}

/**
 * @}
 */

/**
 * nfq_open_nfnl - open a nfqueue handler from a existing nfnetlink handler
 * \param nfnlh Netfilter netlink connection handle obtained by calling nfnl_open()
 *
 * This function obtains a netfilter queue connection handle using an existing
 * netlink connection. This function is used internally to implement 
 * nfq_open(), and should typically not be called directly.
 *
 * \return a pointer to a new queue handle or NULL on failure.
 */
struct nfq_handle *nfq_open_nfnl(struct nfnl_handle *nfnlh)
{
	struct nfq_handle *h;
	int err;

	h = malloc(sizeof(*h));
	if (!h)
		return NULL;

	memset(h, 0, sizeof(*h));
	h->nfnlh = nfnlh;

	h->nfnlssh = nfnl_subsys_open(h->nfnlh, NFNL_SUBSYS_QUEUE, 
				      NFQNL_MSG_MAX, 0);
	if (!h->nfnlssh) {
		/* FIXME: nfq_errno */
		goto out_free;
	}

	pkt_cb.data = h;
	err = nfnl_callback_register(h->nfnlssh, NFQNL_MSG_PACKET, &pkt_cb);
	if (err < 0) {
		nfq_errno = err;
		goto out_close;
	}

	return h;
out_close:
	nfnl_subsys_close(h->nfnlssh);
out_free:
	free(h);
	return NULL;
}

/**
 * \addtogroup LibrarySetup
 *
 * When the program has finished with libnetfilter_queue, it has to call
 * the nfq_close() function to free all associated resources.
 *
 * @{
 */

/**
 * nfq_close - close a nfqueue handler
 * \param h Netfilter queue connection handle obtained via call to nfq_open()
 *
 * This function closes the nfqueue handler and free associated resources.
 *
 * \return 0 on success, non-zero on failure. 
 */
int nfq_close(struct nfq_handle *h)
{
	int ret;
	
	ret = nfnl_close(h->nfnlh);
	if (ret == 0)
		free(h);
	return ret;
}

/**
 * nfq_bind_pf - bind a nfqueue handler to a given protocol family
 * \param h Netfilter queue connection handle obtained via call to nfq_open()
 * \param pf protocol family to bind to nfqueue handler obtained from nfq_open()
 *
 * Binds the given queue connection handle to process packets belonging to 
 * the given protocol family (ie. PF_INET, PF_INET6, etc).
 *
 * \return integer inferior to 0 in case of failure
 */
int nfq_bind_pf(struct nfq_handle *h, u_int16_t pf)
{
	return __build_send_cfg_msg(h, NFQNL_CFG_CMD_PF_BIND, 0, pf);
}

/**
 * nfq_unbind_pf - unbind nfqueue handler from a protocol family
 * \param h Netfilter queue connection handle obtained via call to nfq_open()
 * \param pf protocol family to unbind family from
 *
 * Unbinds the given queue connection handle from processing packets belonging
 * to the given protocol family.
 */
int nfq_unbind_pf(struct nfq_handle *h, u_int16_t pf)
{
	return __build_send_cfg_msg(h, NFQNL_CFG_CMD_PF_UNBIND, 0, pf);
}



/**
 * @}
 */

/**
 * \addtogroup Queue
 * @{
 */

/**
 * nfq_create_queue - create a new queue handle and return it.
 *
 * \param h Netfilter queue connection handle obtained via call to nfq_open()
 * \param num the number of the queue to bind to
 * \param cb callback function to call for each queued packet
 * \param data custom data to pass to the callback function
 *
 * \return a nfq_q_handle pointing to the newly created queue
 *
 * Creates a new queue handle, and returns it.  The new queue is identified by
 * #num, and the callback specified by #cb will be called for each enqueued
 * packet.  The #data argument will be passed unchanged to the callback.  If
 * a queue entry with id #num already exists, this function will return failure
 * and the existing entry is unchanged.
 *
 * The nfq_callback type is defined in libnetfilter_queue.h as:
 * \verbatim
typedef int nfq_callback(struct nfq_q_handle *qh,
		    	 struct nfgenmsg *nfmsg,
			 struct nfq_data *nfad, void *data);
\endverbatim
 *
 * Parameters:
 *  - qh The queue handle returned by nfq_create_queue
 *  - nfmsg message objetc that contains the packet
 *  - nfad Netlink packet data handle
 *  - data the value passed to the data parameter of nfq_create_queue
 *
 * The callback should return < 0 to stop processing.
 */

struct nfq_q_handle *nfq_create_queue(struct nfq_handle *h, 
		u_int16_t num,
		nfq_callback *cb,
		void *data)
{
	int ret;
	struct nfq_q_handle *qh;

	if (find_qh(h, num))
		return NULL;

	qh = malloc(sizeof(*qh));

	memset(qh, 0, sizeof(*qh));
	qh->h = h;
	qh->id = num;
	qh->cb = cb;
	qh->data = data;

	ret = __build_send_cfg_msg(h, NFQNL_CFG_CMD_BIND, num, 0);
	if (ret < 0) {
		nfq_errno = ret;
		free(qh);
		return NULL;
	}

	add_qh(qh);
	return qh;
}

/**
 * @}
 */

/**
 * \addtogroup Queue
 * @{
 */

/**
 * nfq_destroy_queue - destroy a queue handle
 * \param qh queue handle that we want to destroy created via nfq_create_queue
 *
 * Removes the binding for the specified queue handle. This call also unbind
 * from the nfqueue handler, so you don't have to call nfq_unbind_pf.
 */
int nfq_destroy_queue(struct nfq_q_handle *qh)
{
	int ret = __build_send_cfg_msg(qh->h, NFQNL_CFG_CMD_UNBIND, qh->id, 0);
	if (ret == 0) {
		del_qh(qh);
		free(qh);
	}

	return ret;
}

/**
 * nfq_handle_packet - handle a packet received from the nfqueue subsystem
 * \param h Netfilter queue connection handle obtained via call to nfq_open()
 * \param buf data to pass to the callback
 * \param len length of packet data in buffer
 *
 * Triggers an associated callback for the given packet received from the
 * queue. Packets can be read from the queue using nfq_fd() and recv(). See
 * example code for nfq_fd().
 *
 * \return 0 on success, non-zero on failure.
 */
int nfq_handle_packet(struct nfq_handle *h, char *buf, int len)
{
	return nfnl_handle_packet(h->nfnlh, buf, len);
}

/**
 * nfq_set_mode - set the amount of packet data that nfqueue copies to userspace
 * \param qh Netfilter queue handle obtained by call to nfq_create_queue().
 * \param mode the part of the packet that we are interested in
 * \param range size of the packet that we want to get
 *
 * Sets the amount of data to be copied to userspace for each packet queued
 * to the given queue.
 *
 * - NFQNL_COPY_NONE - do not copy any data
 * - NFQNL_COPY_META - copy only packet metadata
 * - NFQNL_COPY_PACKET - copy entire packet
 */
int nfq_set_mode(struct nfq_q_handle *qh,
		u_int8_t mode, u_int32_t range)
{
	union {
		char buf[NFNL_HEADER_LEN
			+NFA_LENGTH(sizeof(struct nfqnl_msg_config_params))];
		struct nlmsghdr nmh;
	} u;
	struct nfqnl_msg_config_params params;

	nfnl_fill_hdr(qh->h->nfnlssh, &u.nmh, 0, AF_UNSPEC, qh->id,
			NFQNL_MSG_CONFIG, NLM_F_REQUEST|NLM_F_ACK);

	params.copy_range = htonl(range);
	params.copy_mode = mode;
	nfnl_addattr_l(&u.nmh, sizeof(u), NFQA_CFG_PARAMS, &params,
			sizeof(params));

	return nfnl_query(qh->h->nfnlh, &u.nmh);
}

/**
 * nfq_set_queue_maxlen - Set kernel queue maximum length parameter
 * \param qh Netfilter queue handle obtained by call to nfq_create_queue().
 * \param queuelen the length of the queue
 *
 * Sets the size of the queue in kernel. This fixes the maximum number
 * of packets the kernel will store before internally before dropping
 * upcoming packets.
 */
int nfq_set_queue_maxlen(struct nfq_q_handle *qh,
				u_int32_t queuelen)
{
	union {
		char buf[NFNL_HEADER_LEN
			+NFA_LENGTH(sizeof(struct nfqnl_msg_config_params))];
		struct nlmsghdr nmh;
	} u;
	u_int32_t queue_maxlen = htonl(queuelen);

	nfnl_fill_hdr(qh->h->nfnlssh, &u.nmh, 0, AF_UNSPEC, qh->id,
			NFQNL_MSG_CONFIG, NLM_F_REQUEST|NLM_F_ACK);

	nfnl_addattr_l(&u.nmh, sizeof(u), NFQA_CFG_QUEUE_MAXLEN, &queue_maxlen,
			sizeof(queue_maxlen));

	return nfnl_query(qh->h->nfnlh, &u.nmh);
}

/**
 * @}
 */

static int __set_verdict(struct nfq_q_handle *qh, u_int32_t id,
		u_int32_t verdict, u_int32_t mark, int set_mark,
		u_int32_t data_len, unsigned char *data)
{
	struct nfqnl_msg_verdict_hdr vh;
	union {
		char buf[NFNL_HEADER_LEN
			+NFA_LENGTH(sizeof(mark))
			+NFA_LENGTH(sizeof(vh))];
		struct nlmsghdr nmh;
	} u;

	struct iovec iov[3];
	int nvecs;

	/* This must be declared here (and not inside the data
	 * handling block) because the iovec points to this. */
	struct nfattr data_attr;

	memset(iov, 0, sizeof(iov));

	vh.verdict = htonl(verdict);
	vh.id = htonl(id);

	nfnl_fill_hdr(qh->h->nfnlssh, &u.nmh, 0, AF_UNSPEC, qh->id,
			NFQNL_MSG_VERDICT, NLM_F_REQUEST);

	/* add verdict header */
	nfnl_addattr_l(&u.nmh, sizeof(u), NFQA_VERDICT_HDR, &vh, sizeof(vh));

	if (set_mark)
		nfnl_addattr32(&u.nmh, sizeof(u), NFQA_MARK, mark);

	iov[0].iov_base = &u.nmh;
	iov[0].iov_len = NLMSG_TAIL(&u.nmh) - (void *)&u.nmh;
	nvecs = 1;

	if (data_len) {
		nfnl_build_nfa_iovec(&iov[1], &data_attr, NFQA_PAYLOAD,
				data_len, data);
		nvecs += 2;
		/* Add the length of the appended data to the message
		 * header.  The size of the attribute is given in the
		 * nfa_len field and is set in the nfnl_build_nfa_iovec()
		 * function. */
		u.nmh.nlmsg_len += data_attr.nfa_len;
	}

	return nfnl_sendiov(qh->h->nfnlh, iov, nvecs, 0);
}

/**
 * \addtogroup Queue
 * @{
 */

/**
 * nfq_set_verdict - issue a verdict on a packet 
 * \param qh Netfilter queue handle obtained by call to nfq_create_queue().
 * \param id	ID assigned to packet by netfilter.
 * \param verdict verdict to return to netfilter (NF_ACCEPT, NF_DROP)
 * \param data_len number of bytes of data pointed to by #buf
 * \param buf the buffer that contains the packet data
 *
 * Can be obtained by: 
 * \verbatim
	int id;
	struct nfqnl_msg_packet_hdr *ph = nfq_get_msg_packet_hdr(tb);
	if (ph)
 		id = ntohl(ph->packet_id);
\endverbatim
 *
 * Notifies netfilter of the userspace verdict for the given packet.  Every
 * queued packet _must_ have a verdict specified by userspace, either by
 * calling this function, or by calling the nfq_set_verdict_mark() function.
 */
int nfq_set_verdict(struct nfq_q_handle *qh, u_int32_t id,
		u_int32_t verdict, u_int32_t data_len, 
		unsigned char *buf)
{
	return __set_verdict(qh, id, verdict, 0, 0, data_len, buf);
}	

/**
 * nfq_set_verdict2 - like nfq_set_verdict, but you can set the mark.
 * \param qh Netfilter queue handle obtained by call to nfq_create_queue().
 * \param id	ID assigned to packet by netfilter.
 * \param verdict verdict to return to netfilter (NF_ACCEPT, NF_DROP)
 * \param mark mark to put on packet
 * \param data_len number of bytes of data pointed to by #buf
 * \param buf the buffer that contains the packet data
 */
int nfq_set_verdict2(struct nfq_q_handle *qh, u_int32_t id,
		     u_int32_t verdict, u_int32_t mark,
		     u_int32_t data_len, unsigned char *buf)
{
	return __set_verdict(qh, id, verdict, htonl(mark), 1, data_len, buf);
}

/**
 * nfq_set_verdict_mark - like nfq_set_verdict, but you can set the mark.
 * \param qh Netfilter queue handle obtained by call to nfq_create_queue().
 * \param id	ID assigned to packet by netfilter.
 * \param verdict verdict to return to netfilter (NF_ACCEPT, NF_DROP)
 * \param mark mark to put on packet
 * \param data_len number of bytes of data pointed to by #buf
 * \param buf the buffer that contains the packet data
 *
 * This function is deprecated since it is broken, its use is highly
 * discouraged. Please, use nfq_set_verdict2 instead.
 */
int nfq_set_verdict_mark(struct nfq_q_handle *qh, u_int32_t id,
		u_int32_t verdict, u_int32_t mark,
		u_int32_t data_len, unsigned char *buf)
{
	return __set_verdict(qh, id, verdict, mark, 1, data_len, buf);
}

/**
 * @}
 */



/*************************************************************
 * Message parsing functions 
 *************************************************************/

/**
 * \defgroup Parsing Message parsing functions
 * @{
 */

/**
 * nfqnl_msg_packet_hdr - return the metaheader that wraps the packet
 * \param nfad Netlink packet data handle passed to callback function
 *
 * \return the netfilter queue netlink packet header for the given
 * nfq_data argument.  Typically, the nfq_data value is passed as the 3rd
 * parameter to the callback function set by a call to nfq_create_queue().
 *
 * The nfqnl_msg_packet_hdr structure is defined in libnetfilter_queue.h as:
 *
 * \verbatim
	struct nfqnl_msg_packet_hdr {
		u_int32_t	packet_id;	// unique ID of packet in queue
		u_int16_t	hw_protocol;	// hw protocol (network order)
		u_int8_t	hook;		// netfilter hook
	} __attribute__ ((packed));
\endverbatim
 */
struct nfqnl_msg_packet_hdr *nfq_get_msg_packet_hdr(struct nfq_data *nfad)
{
	return nfnl_get_pointer_to_data(nfad->data, NFQA_PACKET_HDR,
					struct nfqnl_msg_packet_hdr);
}

/**
 * nfq_get_nfmark - get the packet mark
 * \param nfad Netlink packet data handle passed to callback function
 *
 * \return the netfilter mark currently assigned to the given queued packet.
 */
uint32_t nfq_get_nfmark(struct nfq_data *nfad)
{
	return ntohl(nfnl_get_data(nfad->data, NFQA_MARK, u_int32_t));
}

/**
 * nfq_get_timestamp - get the packet timestamp
 * \param nfad Netlink packet data handle passed to callback function
 * \param tv structure to fill with timestamp info
 *
 * Retrieves the received timestamp when the given queued packet.
 *
 * \return 0 on success, non-zero on failure.
 */
int nfq_get_timestamp(struct nfq_data *nfad, struct timeval *tv)
{
	struct nfqnl_msg_packet_timestamp *qpt;
	qpt = nfnl_get_pointer_to_data(nfad->data, NFQA_TIMESTAMP,
					struct nfqnl_msg_packet_timestamp);
	if (!qpt)
		return -1;

	tv->tv_sec = __be64_to_cpu(qpt->sec);
	tv->tv_usec = __be64_to_cpu(qpt->usec);

	return 0;
}

/**
 * nfq_get_indev - get the interface that the packet was received through
 * \param nfad Netlink packet data handle passed to callback function
 *
 * \return The index of the device the queued packet was received via.  If the
 * returned index is 0, the packet was locally generated or the input
 * interface is not known (ie. POSTROUTING?).
 *
 * \warning all nfq_get_dev() functions return 0 if not set, since linux
 * only allows ifindex >= 1, see net/core/dev.c:2600  (in 2.6.13.1)
 */
u_int32_t nfq_get_indev(struct nfq_data *nfad)
{
	return ntohl(nfnl_get_data(nfad->data, NFQA_IFINDEX_INDEV, u_int32_t));
}

/**
 * nfq_get_physindev - get the physical interface that the packet was received
 * \param nfad Netlink packet data handle passed to callback function
 *
 * \return The index of the physical device the queued packet was received via.
 * If the returned index is 0, the packet was locally generated or the
 * physical input interface is no longer known (ie. POSTROUTING?).
 */
u_int32_t nfq_get_physindev(struct nfq_data *nfad)
{
	return ntohl(nfnl_get_data(nfad->data, NFQA_IFINDEX_PHYSINDEV, u_int32_t));
}

/**
 * nfq_get_outdev - gets the interface that the packet will be routed out
 * \param nfad Netlink packet data handle passed to callback function
 *
 * \return The index of the device the queued packet will be sent out.  If the
 * returned index is 0, the packet is destined for localhost or the output
 * interface is not yet known (ie. PREROUTING?).
 */
u_int32_t nfq_get_outdev(struct nfq_data *nfad)
{
	return ntohl(nfnl_get_data(nfad->data, NFQA_IFINDEX_OUTDEV, u_int32_t));
}

/**
 * nfq_get_physoutdev - get the physical interface that the packet output
 * \param nfad Netlink packet data handle passed to callback function
 *
 * The index of the physical device the queued packet will be sent out.
 * If the returned index is 0, the packet is destined for localhost or the
 * physical output interface is not yet known (ie. PREROUTING?).
 * 
 * \return The index of physical interface that the packet output will be routed out.
 */
u_int32_t nfq_get_physoutdev(struct nfq_data *nfad)
{
	return ntohl(nfnl_get_data(nfad->data, NFQA_IFINDEX_PHYSOUTDEV, u_int32_t));
}

/**
 * nfq_get_indev_name - get the name of the interface the packet
 * was received through
 * \param nlif_handle pointer to a nlif interface resolving handle
 * \param nfad Netlink packet data handle passed to callback function
 * \param name pointer that will be set to the interface name string 
 * \return -1 in case of error, >0 if it succeed. 
 *
 * The #name variable will point to the name of the input interface.
 *
 * To use a nlif_handle, You need first to call nlif_open() and to open
 * an handler. Don't forget to store the result as it will be used 
 * during all your program life:
 * \verbatim
	h = nlif_open();
 	if (h == NULL) {
 		perror("nlif_open");
 		exit(EXIT_FAILURE);
 	}
\endverbatim
 * Once the handler is open, you need to fetch the interface table at a
 * whole via a call to nlif_query.
 * \verbatim
  	nlif_query(h);
\endverbatim
 * libnfnetlink is able to update the interface mapping when a new interface
 * appears. To do so, you need to call nlif_catch() on the handler after each
 * interface related event. The simplest way to get and treat event is to run
 * a select() or poll() against the nlif file descriptor. To get this file 
 * descriptor, you need to use nlif_fd:
 * \verbatim
 	if_fd = nlif_fd(h);
\endverbatim
 * Don't forget to close the handler when you don't need the feature anymore:
 * \verbatim
 	nlif_close(h);
\endverbatim
 *
 */
int nfq_get_indev_name(struct nlif_handle *nlif_handle,
			struct nfq_data *nfad, char *name)
{
	u_int32_t ifindex = nfq_get_indev(nfad);
	return nlif_index2name(nlif_handle, ifindex, name);
}

/**
 * nfq_get_physindev_name - get the name of the physical interface the
 * packet was received through
 * \param nlif_handle pointer to a nlif interface resolving handle
 * \param nfad Netlink packet data handle passed to callback function
 * \param name pointer that will be set to the interface name string 
 *
 * The #name variable will point to the name of the input physical
 * interface.
 *
 * See nfq_get_indev_name() documentation for nlif_handle usage.
 *
 * \return  -1 in case of error, > 0 if it succeed. 
 */
int nfq_get_physindev_name(struct nlif_handle *nlif_handle,
			   struct nfq_data *nfad, char *name)
{
	u_int32_t ifindex = nfq_get_physindev(nfad);
	return nlif_index2name(nlif_handle, ifindex, name);
}

/**
 * nfq_get_outdev_name - get the name of the physical interface the
 * packet will be sent to
 * \param nlif_handle pointer to a nlif interface resolving handle
 * \param nfad Netlink packet data handle passed to callback function
 * \param name pointer that will be set to the interface name string 
 *
 * The #name variable will point to the name of the output interface.
 *
 * See nfq_get_indev_name() documentation for nlif_handle usage.
 *
 * \return  -1 in case of error, > 0 if it succeed. 
 */
int nfq_get_outdev_name(struct nlif_handle *nlif_handle,
			struct nfq_data *nfad, char *name)
{
	u_int32_t ifindex = nfq_get_outdev(nfad);
	return nlif_index2name(nlif_handle, ifindex, name);
}

/**
 * nfq_get_physoutdev_name - get the name of the interface the
 * packet will be sent to
 * \param nlif_handle pointer to a nlif interface resolving handle
 * \param nfad Netlink packet data handle passed to callback function
 * \param name pointer that will be set to the interface name string 
 * The #name variable will point to the name of the physical
 * output interface.
 *
 * See nfq_get_indev_name() documentation for nlif_handle usage.
 *
 * \return  -1 in case of error, > 0 if it succeed. 
 */

int nfq_get_physoutdev_name(struct nlif_handle *nlif_handle,
			    struct nfq_data *nfad, char *name)
{
	u_int32_t ifindex = nfq_get_physoutdev(nfad);
	return nlif_index2name(nlif_handle, ifindex, name);
}

/**
 * nfq_get_packet_hw
 *
 * get hardware address 
 *
 * \param nfad Netlink packet data handle passed to callback function
 *
 * Retrieves the hardware address associated with the given queued packet.
 * For ethernet packets, the hardware address returned (if any) will be the
 * MAC address of the packet source host.  The destination MAC address is not
 * known until after POSTROUTING and a successful ARP request, so cannot
 * currently be retrieved.
 *
 * The nfqnl_msg_packet_hw structure is defined in libnetfilter_queue.h as:
 * \verbatim
	struct nfqnl_msg_packet_hw {
		u_int16_t	hw_addrlen;
		u_int16_t	_pad;
		u_int8_t	hw_addr[8];
	} __attribute__ ((packed));
\endverbatim
 */
struct nfqnl_msg_packet_hw *nfq_get_packet_hw(struct nfq_data *nfad)
{
	return nfnl_get_pointer_to_data(nfad->data, NFQA_HWADDR,
					struct nfqnl_msg_packet_hw);
}

/**
 * nfq_get_payload - get payload 
 * \param nfad Netlink packet data handle passed to callback function
 * \param data Pointer of pointer that will be pointed to the payload
 *
 * Retrieve the payload for a queued packet. The actual amount and type of
 * data retrieved by this function will depend on the mode set with the
 * nfq_set_mode() function.
 *
 * \return -1 on error, otherwise > 0.
 */
int nfq_get_payload(struct nfq_data *nfad, char **data)
{
	*data = nfnl_get_pointer_to_data(nfad->data, NFQA_PAYLOAD, char);
	if (*data)
		return NFA_PAYLOAD(nfad->data[NFQA_PAYLOAD-1]);

	return -1;
}

/**
 * @}
 */