summaryrefslogtreecommitdiffstats
path: root/tools/net/ynl/lib/ynl.c
blob: f830990b3f4ae95a733dde70976dca10dddac8ab (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
// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
#include <errno.h>
#include <poll.h>
#include <string.h>
#include <stdlib.h>
#include <linux/types.h>

#include <libmnl/libmnl.h>
#include <linux/genetlink.h>

#include "ynl.h"

#define ARRAY_SIZE(arr)		(sizeof(arr) / sizeof(*arr))

#define __yerr_msg(yse, _msg...)					\
	({								\
		struct ynl_error *_yse = (yse);				\
									\
		if (_yse) {						\
			snprintf(_yse->msg, sizeof(_yse->msg) - 1,  _msg); \
			_yse->msg[sizeof(_yse->msg) - 1] = 0;		\
		}							\
	})

#define __yerr_code(yse, _code...)		\
	({					\
		struct ynl_error *_yse = (yse);	\
						\
		if (_yse) {			\
			_yse->code = _code;	\
		}				\
	})

#define __yerr(yse, _code, _msg...)		\
	({					\
		__yerr_msg(yse, _msg);		\
		__yerr_code(yse, _code);	\
	})

#define __perr(yse, _msg)		__yerr(yse, errno, _msg)

#define yerr_msg(_ys, _msg...)		__yerr_msg(&(_ys)->err, _msg)
#define yerr(_ys, _code, _msg...)	__yerr(&(_ys)->err, _code, _msg)
#define perr(_ys, _msg)			__yerr(&(_ys)->err, errno, _msg)

/* -- Netlink boiler plate */
static int
ynl_err_walk_report_one(struct ynl_policy_nest *policy, unsigned int type,
			char *str, int str_sz, int *n)
{
	if (!policy) {
		if (*n < str_sz)
			*n += snprintf(str, str_sz, "!policy");
		return 1;
	}

	if (type > policy->max_attr) {
		if (*n < str_sz)
			*n += snprintf(str, str_sz, "!oob");
		return 1;
	}

	if (!policy->table[type].name) {
		if (*n < str_sz)
			*n += snprintf(str, str_sz, "!name");
		return 1;
	}

	if (*n < str_sz)
		*n += snprintf(str, str_sz - *n,
			       ".%s", policy->table[type].name);
	return 0;
}

static int
ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off,
	     struct ynl_policy_nest *policy, char *str, int str_sz,
	     struct ynl_policy_nest **nest_pol)
{
	unsigned int astart_off, aend_off;
	const struct nlattr *attr;
	unsigned int data_len;
	unsigned int type;
	bool found = false;
	int n = 0;

	if (!policy) {
		if (n < str_sz)
			n += snprintf(str, str_sz, "!policy");
		return n;
	}

	data_len = end - start;

	ynl_attr_for_each_payload(start, data_len, attr) {
		astart_off = (char *)attr - (char *)start;
		aend_off = astart_off + ynl_attr_data_len(attr);
		if (aend_off <= off)
			continue;

		found = true;
		break;
	}
	if (!found)
		return 0;

	off -= astart_off;

	type = ynl_attr_type(attr);

	if (ynl_err_walk_report_one(policy, type, str, str_sz, &n))
		return n;

	if (!off) {
		if (nest_pol)
			*nest_pol = policy->table[type].nest;
		return n;
	}

	if (!policy->table[type].nest) {
		if (n < str_sz)
			n += snprintf(str, str_sz, "!nest");
		return n;
	}

	off -= sizeof(struct nlattr);
	start =  ynl_attr_data(attr);
	end = start + ynl_attr_data_len(attr);

	return n + ynl_err_walk(ys, start, end, off, policy->table[type].nest,
				&str[n], str_sz - n, nest_pol);
}

#define NLMSGERR_ATTR_MISS_TYPE (NLMSGERR_ATTR_POLICY + 1)
#define NLMSGERR_ATTR_MISS_NEST (NLMSGERR_ATTR_POLICY + 2)
#define NLMSGERR_ATTR_MAX (NLMSGERR_ATTR_MAX + 2)

static int
ynl_ext_ack_check(struct ynl_sock *ys, const struct nlmsghdr *nlh,
		  unsigned int hlen)
{
	const struct nlattr *tb[NLMSGERR_ATTR_MAX + 1] = {};
	char miss_attr[sizeof(ys->err.msg)];
	char bad_attr[sizeof(ys->err.msg)];
	const struct nlattr *attr;
	const char *str = NULL;

	if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS)) {
		yerr_msg(ys, "%s", strerror(ys->err.code));
		return MNL_CB_OK;
	}

	ynl_attr_for_each(attr, nlh, hlen) {
		unsigned int len, type;

		len = ynl_attr_data_len(attr);
		type = ynl_attr_type(attr);

		if (type > NLMSGERR_ATTR_MAX)
			continue;

		tb[type] = attr;

		switch (type) {
		case NLMSGERR_ATTR_OFFS:
		case NLMSGERR_ATTR_MISS_TYPE:
		case NLMSGERR_ATTR_MISS_NEST:
			if (len != sizeof(__u32))
				return MNL_CB_ERROR;
			break;
		case NLMSGERR_ATTR_MSG:
			str = ynl_attr_get_str(attr);
			if (str[len - 1])
				return MNL_CB_ERROR;
			break;
		default:
			break;
		}
	}

	bad_attr[0] = '\0';
	miss_attr[0] = '\0';

	if (tb[NLMSGERR_ATTR_OFFS]) {
		unsigned int n, off;
		void *start, *end;

		ys->err.attr_offs = ynl_attr_get_u32(tb[NLMSGERR_ATTR_OFFS]);

		n = snprintf(bad_attr, sizeof(bad_attr), "%sbad attribute: ",
			     str ? " (" : "");

		start = ynl_nlmsg_data_offset(ys->nlh, ys->family->hdr_len);
		end = ynl_nlmsg_end_addr(ys->nlh);

		off = ys->err.attr_offs;
		off -= sizeof(struct nlmsghdr);
		off -= ys->family->hdr_len;

		n += ynl_err_walk(ys, start, end, off, ys->req_policy,
				  &bad_attr[n], sizeof(bad_attr) - n, NULL);

		if (n >= sizeof(bad_attr))
			n = sizeof(bad_attr) - 1;
		bad_attr[n] = '\0';
	}
	if (tb[NLMSGERR_ATTR_MISS_TYPE]) {
		struct ynl_policy_nest *nest_pol = NULL;
		unsigned int n, off, type;
		void *start, *end;
		int n2;

		type = ynl_attr_get_u32(tb[NLMSGERR_ATTR_MISS_TYPE]);

		n = snprintf(miss_attr, sizeof(miss_attr), "%smissing attribute: ",
			     bad_attr[0] ? ", " : (str ? " (" : ""));

		start = ynl_nlmsg_data_offset(ys->nlh, ys->family->hdr_len);
		end = ynl_nlmsg_end_addr(ys->nlh);

		nest_pol = ys->req_policy;
		if (tb[NLMSGERR_ATTR_MISS_NEST]) {
			off = ynl_attr_get_u32(tb[NLMSGERR_ATTR_MISS_NEST]);
			off -= sizeof(struct nlmsghdr);
			off -= ys->family->hdr_len;

			n += ynl_err_walk(ys, start, end, off, ys->req_policy,
					  &miss_attr[n], sizeof(miss_attr) - n,
					  &nest_pol);
		}

		n2 = 0;
		ynl_err_walk_report_one(nest_pol, type, &miss_attr[n],
					sizeof(miss_attr) - n, &n2);
		n += n2;

		if (n >= sizeof(miss_attr))
			n = sizeof(miss_attr) - 1;
		miss_attr[n] = '\0';
	}

	/* Implicitly depend on ys->err.code already set */
	if (str)
		yerr_msg(ys, "Kernel %s: '%s'%s%s%s",
			 ys->err.code ? "error" : "warning",
			 str, bad_attr, miss_attr,
			 bad_attr[0] || miss_attr[0] ? ")" : "");
	else if (bad_attr[0] || miss_attr[0])
		yerr_msg(ys, "Kernel %s: %s%s",
			 ys->err.code ? "error" : "warning",
			 bad_attr, miss_attr);
	else
		yerr_msg(ys, "%s", strerror(ys->err.code));

	return MNL_CB_OK;
}

static int ynl_cb_error(const struct nlmsghdr *nlh, void *data)
{
	const struct nlmsgerr *err = ynl_nlmsg_data(nlh);
	struct ynl_parse_arg *yarg = data;
	unsigned int hlen;
	int code;

	code = err->error >= 0 ? err->error : -err->error;
	yarg->ys->err.code = code;
	errno = code;

	hlen = sizeof(*err);
	if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
		hlen += ynl_nlmsg_data_len(&err->msg);

	ynl_ext_ack_check(yarg->ys, nlh, hlen);

	return code ? MNL_CB_ERROR : MNL_CB_STOP;
}

static int ynl_cb_done(const struct nlmsghdr *nlh, void *data)
{
	struct ynl_parse_arg *yarg = data;
	int err;

	err = *(int *)NLMSG_DATA(nlh);
	if (err < 0) {
		yarg->ys->err.code = -err;
		errno = -err;

		ynl_ext_ack_check(yarg->ys, nlh, sizeof(int));

		return MNL_CB_ERROR;
	}
	return MNL_CB_STOP;
}

static int ynl_cb_noop(const struct nlmsghdr *nlh, void *data)
{
	return MNL_CB_OK;
}

static mnl_cb_t ynl_cb_array[NLMSG_MIN_TYPE] = {
	[NLMSG_NOOP]	= ynl_cb_noop,
	[NLMSG_ERROR]	= ynl_cb_error,
	[NLMSG_DONE]	= ynl_cb_done,
	[NLMSG_OVERRUN]	= ynl_cb_noop,
};

/* Attribute validation */

int ynl_attr_validate(struct ynl_parse_arg *yarg, const struct nlattr *attr)
{
	struct ynl_policy_attr *policy;
	unsigned int type, len;
	unsigned char *data;

	data = ynl_attr_data(attr);
	len = ynl_attr_data_len(attr);
	type = ynl_attr_type(attr);
	if (type > yarg->rsp_policy->max_attr) {
		yerr(yarg->ys, YNL_ERROR_INTERNAL,
		     "Internal error, validating unknown attribute");
		return -1;
	}

	policy = &yarg->rsp_policy->table[type];

	switch (policy->type) {
	case YNL_PT_REJECT:
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Rejected attribute (%s)", policy->name);
		return -1;
	case YNL_PT_IGNORE:
		break;
	case YNL_PT_U8:
		if (len == sizeof(__u8))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (u8 %s)", policy->name);
		return -1;
	case YNL_PT_U16:
		if (len == sizeof(__u16))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (u16 %s)", policy->name);
		return -1;
	case YNL_PT_U32:
		if (len == sizeof(__u32))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (u32 %s)", policy->name);
		return -1;
	case YNL_PT_U64:
		if (len == sizeof(__u64))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (u64 %s)", policy->name);
		return -1;
	case YNL_PT_UINT:
		if (len == sizeof(__u32) || len == sizeof(__u64))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (uint %s)", policy->name);
		return -1;
	case YNL_PT_FLAG:
		/* Let flags grow into real attrs, why not.. */
		break;
	case YNL_PT_NEST:
		if (!len || len >= sizeof(*attr))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (nest %s)", policy->name);
		return -1;
	case YNL_PT_BINARY:
		if (!policy->len || len == policy->len)
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (binary %s)", policy->name);
		return -1;
	case YNL_PT_NUL_STR:
		if ((!policy->len || len <= policy->len) && !data[len - 1])
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (string %s)", policy->name);
		return -1;
	case YNL_PT_BITFIELD32:
		if (len == sizeof(struct nla_bitfield32))
			break;
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (bitfield32 %s)", policy->name);
		return -1;
	default:
		yerr(yarg->ys, YNL_ERROR_ATTR_INVALID,
		     "Invalid attribute (unknown %s)", policy->name);
		return -1;
	}

	return 0;
}

/* Generic code */

static void ynl_err_reset(struct ynl_sock *ys)
{
	ys->err.code = 0;
	ys->err.attr_offs = 0;
	ys->err.msg[0] = 0;
}

struct nlmsghdr *ynl_msg_start(struct ynl_sock *ys, __u32 id, __u16 flags)
{
	struct nlmsghdr *nlh;

	ynl_err_reset(ys);

	nlh = ys->nlh = ynl_nlmsg_put_header(ys->tx_buf);
	nlh->nlmsg_type	= id;
	nlh->nlmsg_flags = flags;
	nlh->nlmsg_seq = ++ys->seq;

	return nlh;
}

struct nlmsghdr *
ynl_gemsg_start(struct ynl_sock *ys, __u32 id, __u16 flags,
		__u8 cmd, __u8 version)
{
	struct genlmsghdr gehdr;
	struct nlmsghdr *nlh;
	void *data;

	nlh = ynl_msg_start(ys, id, flags);

	memset(&gehdr, 0, sizeof(gehdr));
	gehdr.cmd = cmd;
	gehdr.version = version;

	data = ynl_nlmsg_put_extra_header(nlh, sizeof(gehdr));
	memcpy(data, &gehdr, sizeof(gehdr));

	return nlh;
}

void ynl_msg_start_req(struct ynl_sock *ys, __u32 id)
{
	ynl_msg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK);
}

void ynl_msg_start_dump(struct ynl_sock *ys, __u32 id)
{
	ynl_msg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);
}

struct nlmsghdr *
ynl_gemsg_start_req(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version)
{
	return ynl_gemsg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK, cmd, version);
}

struct nlmsghdr *
ynl_gemsg_start_dump(struct ynl_sock *ys, __u32 id, __u8 cmd, __u8 version)
{
	return ynl_gemsg_start(ys, id, NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP,
			       cmd, version);
}

static int ynl_cb_null(const struct nlmsghdr *nlh, void *data)
{
	struct ynl_parse_arg *yarg = data;

	yerr(yarg->ys, YNL_ERROR_UNEXPECT_MSG,
	     "Received a message when none were expected");

	return MNL_CB_ERROR;
}

static int ynl_sock_read_msgs(struct ynl_parse_arg *yarg, mnl_cb_t cb)
{
	struct ynl_sock *ys = yarg->ys;
	ssize_t len;

	len = mnl_socket_recvfrom(ys->sock, ys->rx_buf, MNL_SOCKET_BUFFER_SIZE);
	if (len < 0)
		return len;

	return mnl_cb_run2(ys->rx_buf, len, ys->seq, ys->portid,
			   cb, yarg, ynl_cb_array, NLMSG_MIN_TYPE);
}

static int ynl_recv_ack(struct ynl_sock *ys, int ret)
{
	struct ynl_parse_arg yarg = { .ys = ys, };

	if (!ret) {
		yerr(ys, YNL_ERROR_EXPECT_ACK,
		     "Expecting an ACK but nothing received");
		return -1;
	}

	return ynl_sock_read_msgs(&yarg, ynl_cb_null);
}

/* Init/fini and genetlink boiler plate */
static int
ynl_get_family_info_mcast(struct ynl_sock *ys, const struct nlattr *mcasts)
{
	const struct nlattr *entry, *attr;
	unsigned int i;

	ynl_attr_for_each_nested(attr, mcasts)
		ys->n_mcast_groups++;

	if (!ys->n_mcast_groups)
		return 0;

	ys->mcast_groups = calloc(ys->n_mcast_groups,
				  sizeof(*ys->mcast_groups));
	if (!ys->mcast_groups)
		return MNL_CB_ERROR;

	i = 0;
	ynl_attr_for_each_nested(entry, mcasts) {
		ynl_attr_for_each_nested(attr, entry) {
			if (ynl_attr_type(attr) == CTRL_ATTR_MCAST_GRP_ID)
				ys->mcast_groups[i].id = ynl_attr_get_u32(attr);
			if (ynl_attr_type(attr) == CTRL_ATTR_MCAST_GRP_NAME) {
				strncpy(ys->mcast_groups[i].name,
					ynl_attr_get_str(attr),
					GENL_NAMSIZ - 1);
				ys->mcast_groups[i].name[GENL_NAMSIZ - 1] = 0;
			}
		}
	}

	return 0;
}

static int ynl_get_family_info_cb(const struct nlmsghdr *nlh, void *data)
{
	struct ynl_parse_arg *yarg = data;
	struct ynl_sock *ys = yarg->ys;
	const struct nlattr *attr;
	bool found_id = true;

	ynl_attr_for_each(attr, nlh, sizeof(struct genlmsghdr)) {
		if (ynl_attr_type(attr) == CTRL_ATTR_MCAST_GROUPS)
			if (ynl_get_family_info_mcast(ys, attr))
				return MNL_CB_ERROR;

		if (ynl_attr_type(attr) != CTRL_ATTR_FAMILY_ID)
			continue;

		if (ynl_attr_data_len(attr) != sizeof(__u16)) {
			yerr(ys, YNL_ERROR_ATTR_INVALID, "Invalid family ID");
			return MNL_CB_ERROR;
		}

		ys->family_id = ynl_attr_get_u16(attr);
		found_id = true;
	}

	if (!found_id) {
		yerr(ys, YNL_ERROR_ATTR_MISSING, "Family ID missing");
		return MNL_CB_ERROR;
	}
	return MNL_CB_OK;
}

static int ynl_sock_read_family(struct ynl_sock *ys, const char *family_name)
{
	struct ynl_parse_arg yarg = { .ys = ys, };
	struct nlmsghdr *nlh;
	int err;

	nlh = ynl_gemsg_start_req(ys, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, 1);
	ynl_attr_put_str(nlh, CTRL_ATTR_FAMILY_NAME, family_name);

	err = mnl_socket_sendto(ys->sock, nlh, nlh->nlmsg_len);
	if (err < 0) {
		perr(ys, "failed to request socket family info");
		return err;
	}

	err = ynl_sock_read_msgs(&yarg, ynl_get_family_info_cb);
	if (err < 0) {
		free(ys->mcast_groups);
		perr(ys, "failed to receive the socket family info - no such family?");
		return err;
	}

	err = ynl_recv_ack(ys, err);
	if (err < 0) {
		free(ys->mcast_groups);
		return err;
	}

	return 0;
}

struct ynl_sock *
ynl_sock_create(const struct ynl_family *yf, struct ynl_error *yse)
{
	struct ynl_sock *ys;
	int one = 1;

	ys = malloc(sizeof(*ys) + 2 * MNL_SOCKET_BUFFER_SIZE);
	if (!ys)
		return NULL;
	memset(ys, 0, sizeof(*ys));

	ys->family = yf;
	ys->tx_buf = &ys->raw_buf[0];
	ys->rx_buf = &ys->raw_buf[MNL_SOCKET_BUFFER_SIZE];
	ys->ntf_last_next = &ys->ntf_first;

	ys->sock = mnl_socket_open(NETLINK_GENERIC);
	if (!ys->sock) {
		__perr(yse, "failed to create a netlink socket");
		goto err_free_sock;
	}

	if (mnl_socket_setsockopt(ys->sock, NETLINK_CAP_ACK,
				  &one, sizeof(one))) {
		__perr(yse, "failed to enable netlink ACK");
		goto err_close_sock;
	}
	if (mnl_socket_setsockopt(ys->sock, NETLINK_EXT_ACK,
				  &one, sizeof(one))) {
		__perr(yse, "failed to enable netlink ext ACK");
		goto err_close_sock;
	}

	ys->seq = random();
	ys->portid = mnl_socket_get_portid(ys->sock);

	if (ynl_sock_read_family(ys, yf->name)) {
		if (yse)
			memcpy(yse, &ys->err, sizeof(*yse));
		goto err_close_sock;
	}

	return ys;

err_close_sock:
	mnl_socket_close(ys->sock);
err_free_sock:
	free(ys);
	return NULL;
}

void ynl_sock_destroy(struct ynl_sock *ys)
{
	struct ynl_ntf_base_type *ntf;

	mnl_socket_close(ys->sock);
	while ((ntf = ynl_ntf_dequeue(ys)))
		ynl_ntf_free(ntf);
	free(ys->mcast_groups);
	free(ys);
}

/* YNL multicast handling */

void ynl_ntf_free(struct ynl_ntf_base_type *ntf)
{
	ntf->free(ntf);
}

int ynl_subscribe(struct ynl_sock *ys, const char *grp_name)
{
	unsigned int i;
	int err;

	for (i = 0; i < ys->n_mcast_groups; i++)
		if (!strcmp(ys->mcast_groups[i].name, grp_name))
			break;
	if (i == ys->n_mcast_groups) {
		yerr(ys, ENOENT, "Multicast group '%s' not found", grp_name);
		return -1;
	}

	err = mnl_socket_setsockopt(ys->sock, NETLINK_ADD_MEMBERSHIP,
				    &ys->mcast_groups[i].id,
				    sizeof(ys->mcast_groups[i].id));
	if (err < 0) {
		perr(ys, "Subscribing to multicast group failed");
		return -1;
	}

	return 0;
}

int ynl_socket_get_fd(struct ynl_sock *ys)
{
	return mnl_socket_get_fd(ys->sock);
}

struct ynl_ntf_base_type *ynl_ntf_dequeue(struct ynl_sock *ys)
{
	struct ynl_ntf_base_type *ntf;

	if (!ynl_has_ntf(ys))
		return NULL;

	ntf = ys->ntf_first;
	ys->ntf_first = ntf->next;
	if (ys->ntf_last_next == &ntf->next)
		ys->ntf_last_next = &ys->ntf_first;

	return ntf;
}

static int ynl_ntf_parse(struct ynl_sock *ys, const struct nlmsghdr *nlh)
{
	struct ynl_parse_arg yarg = { .ys = ys, };
	const struct ynl_ntf_info *info;
	struct ynl_ntf_base_type *rsp;
	struct genlmsghdr *gehdr;
	int ret;

	gehdr = ynl_nlmsg_data(nlh);
	if (gehdr->cmd >= ys->family->ntf_info_size)
		return MNL_CB_ERROR;
	info = &ys->family->ntf_info[gehdr->cmd];
	if (!info->cb)
		return MNL_CB_ERROR;

	rsp = calloc(1, info->alloc_sz);
	rsp->free = info->free;
	yarg.data = rsp->data;
	yarg.rsp_policy = info->policy;

	ret = info->cb(nlh, &yarg);
	if (ret <= MNL_CB_STOP)
		goto err_free;

	rsp->family = nlh->nlmsg_type;
	rsp->cmd = gehdr->cmd;

	*ys->ntf_last_next = rsp;
	ys->ntf_last_next = &rsp->next;

	return MNL_CB_OK;

err_free:
	info->free(rsp);
	return MNL_CB_ERROR;
}

static int ynl_ntf_trampoline(const struct nlmsghdr *nlh, void *data)
{
	struct ynl_parse_arg *yarg = data;

	return ynl_ntf_parse(yarg->ys, nlh);
}

int ynl_ntf_check(struct ynl_sock *ys)
{
	struct ynl_parse_arg yarg = { .ys = ys, };
	int err;

	do {
		/* libmnl doesn't let us pass flags to the recv to make
		 * it non-blocking so we need to poll() or peek() :|
		 */
		struct pollfd pfd = { };

		pfd.fd = mnl_socket_get_fd(ys->sock);
		pfd.events = POLLIN;
		err = poll(&pfd, 1, 1);
		if (err < 1)
			return err;

		err = ynl_sock_read_msgs(&yarg, ynl_ntf_trampoline);
		if (err < 0)
			return err;
	} while (err > 0);

	return 0;
}

/* YNL specific helpers used by the auto-generated code */

struct ynl_dump_list_type *YNL_LIST_END = (void *)(0xb4d123);

void ynl_error_unknown_notification(struct ynl_sock *ys, __u8 cmd)
{
	yerr(ys, YNL_ERROR_UNKNOWN_NTF,
	     "Unknown notification message type '%d'", cmd);
}

int ynl_error_parse(struct ynl_parse_arg *yarg, const char *msg)
{
	yerr(yarg->ys, YNL_ERROR_INV_RESP, "Error parsing response: %s", msg);
	return MNL_CB_ERROR;
}

static int
ynl_check_alien(struct ynl_sock *ys, const struct nlmsghdr *nlh, __u32 rsp_cmd)
{
	struct genlmsghdr *gehdr;

	if (ynl_nlmsg_data_len(nlh) < sizeof(*gehdr)) {
		yerr(ys, YNL_ERROR_INV_RESP,
		     "Kernel responded with truncated message");
		return -1;
	}

	gehdr = ynl_nlmsg_data(nlh);
	if (gehdr->cmd != rsp_cmd)
		return ynl_ntf_parse(ys, nlh);

	return 0;
}

static int ynl_req_trampoline(const struct nlmsghdr *nlh, void *data)
{
	struct ynl_req_state *yrs = data;
	int ret;

	ret = ynl_check_alien(yrs->yarg.ys, nlh, yrs->rsp_cmd);
	if (ret)
		return ret < 0 ? MNL_CB_ERROR : MNL_CB_OK;

	return yrs->cb(nlh, &yrs->yarg);
}

int ynl_exec(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
	     struct ynl_req_state *yrs)
{
	int err;

	err = mnl_socket_sendto(ys->sock, req_nlh, req_nlh->nlmsg_len);
	if (err < 0)
		return err;

	do {
		err = ynl_sock_read_msgs(&yrs->yarg, ynl_req_trampoline);
	} while (err > 0);

	return err;
}

static int ynl_dump_trampoline(const struct nlmsghdr *nlh, void *data)
{
	struct ynl_dump_state *ds = data;
	struct ynl_dump_list_type *obj;
	struct ynl_parse_arg yarg = {};
	int ret;

	ret = ynl_check_alien(ds->yarg.ys, nlh, ds->rsp_cmd);
	if (ret)
		return ret < 0 ? MNL_CB_ERROR : MNL_CB_OK;

	obj = calloc(1, ds->alloc_sz);
	if (!obj)
		return MNL_CB_ERROR;

	if (!ds->first)
		ds->first = obj;
	if (ds->last)
		ds->last->next = obj;
	ds->last = obj;

	yarg = ds->yarg;
	yarg.data = &obj->data;

	return ds->cb(nlh, &yarg);
}

static void *ynl_dump_end(struct ynl_dump_state *ds)
{
	if (!ds->first)
		return YNL_LIST_END;

	ds->last->next = YNL_LIST_END;
	return ds->first;
}

int ynl_exec_dump(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
		  struct ynl_dump_state *yds)
{
	int err;

	err = mnl_socket_sendto(ys->sock, req_nlh, req_nlh->nlmsg_len);
	if (err < 0)
		return err;

	do {
		err = ynl_sock_read_msgs(&yds->yarg, ynl_dump_trampoline);
		if (err < 0)
			goto err_close_list;
	} while (err > 0);

	yds->first = ynl_dump_end(yds);
	return 0;

err_close_list:
	yds->first = ynl_dump_end(yds);
	return -1;
}