summaryrefslogtreecommitdiffstats
path: root/src/meta.c
blob: 8c2eca270e0dcce073630c471fa902ef72997d1a (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
/*
 * Meta expression/statement related definition and types.
 *
 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
 *
 * 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.
 *
 * Development of this code funded by Astaro AG (http://www.astaro.com/)
 */

#include <errno.h>
#include <limits.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <pwd.h>
#include <grp.h>
#include <arpa/inet.h>
#include <linux/netfilter.h>
#include <linux/pkt_sched.h>
#include <linux/if_packet.h>

#include <nftables.h>
#include <expression.h>
#include <statement.h>
#include <datatype.h>
#include <meta.h>
#include <gmputil.h>
#include <utils.h>
#include <erec.h>
#include <iface.h>

static struct symbol_table *realm_tbl;
void realm_table_meta_init(void)
{
	realm_tbl = rt_symbol_table_init("/etc/iproute2/rt_realms");
}

void realm_table_meta_exit(void)
{
	rt_symbol_table_free(realm_tbl);
}

static void tchandle_type_print(const struct expr *expr,
				struct output_ctx *octx)
{
	uint32_t handle = mpz_get_uint32(expr->value);

	switch(handle) {
	case TC_H_ROOT:
		nft_print(octx, "root");
		break;
	case TC_H_UNSPEC:
		nft_print(octx, "none");
		break;
	default:
		nft_print(octx, "%0x:%0x",
			  TC_H_MAJ(handle) >> 16,
			  TC_H_MIN(handle));
		break;
	}
}

static struct error_record *tchandle_type_parse(const struct expr *sym,
						struct expr **res)
{
	uint32_t handle;
	char *str = NULL;

	if (strcmp(sym->identifier, "root") == 0)
		handle = TC_H_ROOT;
	else if (strcmp(sym->identifier, "none") == 0)
		handle = TC_H_UNSPEC;
	else if (strchr(sym->identifier, ':')) {
		uint16_t tmp;
		char *colon;

		str = xstrdup(sym->identifier);

		colon = strchr(str, ':');
		if (!colon)
			goto err;

		*colon = '\0';

		errno = 0;
		tmp = strtoull(str, NULL, 16);
		if (errno != 0)
			goto err;

		handle = (tmp << 16);
		if (str[strlen(str) - 1] == ':')
			goto out;

		errno = 0;
		tmp = strtoull(colon + 1, NULL, 16);
		if (errno != 0)
			goto err;

		handle |= tmp;
	} else {
		handle = strtoull(sym->identifier, NULL, 0);
	}
out:
	xfree(str);
	*res = constant_expr_alloc(&sym->location, sym->dtype,
				   BYTEORDER_HOST_ENDIAN,
				   sizeof(handle) * BITS_PER_BYTE, &handle);
	return NULL;
err:
	xfree(str);
	return error(&sym->location, "Could not parse %s", sym->dtype->desc);
}

const struct datatype tchandle_type = {
	.type		= TYPE_CLASSID,
	.name		= "classid",
	.desc		= "TC classid",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= 4 * BITS_PER_BYTE,
	.basetype	= &integer_type,
	.print		= tchandle_type_print,
	.parse		= tchandle_type_parse,
};

static void ifindex_type_print(const struct expr *expr, struct output_ctx *octx)
{
	char name[IFNAMSIZ];
	int ifindex;

	ifindex = mpz_get_uint32(expr->value);
	if (nft_if_indextoname(ifindex, name))
		nft_print(octx, "\"%s\"", name);
	else
		nft_print(octx, "%d", ifindex);
}

static struct error_record *ifindex_type_parse(const struct expr *sym,
					       struct expr **res)
{
	int ifindex;

	ifindex = nft_if_nametoindex(sym->identifier);
	if (ifindex == 0) {
		char *end;
		long res;

		errno = 0;
		res = strtol(sym->identifier, &end, 10);

		if (res < 0 || res > INT_MAX || *end || errno)
			return error(&sym->location, "Interface does not exist");

		ifindex = (int)res;
	}

	*res = constant_expr_alloc(&sym->location, sym->dtype,
				   BYTEORDER_HOST_ENDIAN,
				   sizeof(ifindex) * BITS_PER_BYTE, &ifindex);
	return NULL;
}

const struct datatype ifindex_type = {
	.type		= TYPE_IFINDEX,
	.name		= "iface_index",
	.desc		= "network interface index",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= 4 * BITS_PER_BYTE,
	.basetype	= &integer_type,
	.print		= ifindex_type_print,
	.parse		= ifindex_type_parse,
};

static const struct symbol_table arphrd_tbl = {
	.base		= BASE_HEXADECIMAL,
	.symbols	= {
		SYMBOL("ether",		ARPHRD_ETHER),
		SYMBOL("ppp",		ARPHRD_PPP),
		/* dummy types */
		SYMBOL("ipip",		ARPHRD_TUNNEL),
		SYMBOL("ipip6",		ARPHRD_TUNNEL6),
		SYMBOL("loopback",	ARPHRD_LOOPBACK),
		SYMBOL("sit",		ARPHRD_SIT),
		SYMBOL("ipgre",		ARPHRD_IPGRE),
		SYMBOL_LIST_END,
	},
};

const struct datatype arphrd_type = {
	.type		= TYPE_ARPHRD,
	.name		= "iface_type",
	.desc		= "network interface type",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= 2 * BITS_PER_BYTE,
	.basetype	= &integer_type,
	.sym_tbl	= &arphrd_tbl,
};

static void uid_type_print(const struct expr *expr, struct output_ctx *octx)
{
	struct passwd *pw;

	if (octx->numeric < NFT_NUMERIC_ALL) {
		uint32_t uid = mpz_get_uint32(expr->value);

		pw = getpwuid(uid);
		if (pw != NULL)
			nft_print(octx, "\"%s\"", pw->pw_name);
		else
			nft_print(octx, "%d", uid);
		return;
	}
	expr_basetype(expr)->print(expr, octx);
}

static struct error_record *uid_type_parse(const struct expr *sym,
					   struct expr **res)
{
	struct passwd *pw;
	uint64_t uid;
	char *endptr = NULL;

	pw = getpwnam(sym->identifier);
	if (pw != NULL)
		uid = pw->pw_uid;
	else {
		uid = strtoull(sym->identifier, &endptr, 10);
		if (uid > UINT32_MAX)
			return error(&sym->location, "Value too large");
		else if (*endptr)
			return error(&sym->location, "User does not exist");
	}

	*res = constant_expr_alloc(&sym->location, sym->dtype,
				   BYTEORDER_HOST_ENDIAN,
				   sizeof(pw->pw_uid) * BITS_PER_BYTE, &uid);
	return NULL;
}

const struct datatype uid_type = {
	.type		= TYPE_UID,
	.name		= "uid",
	.desc		= "user ID",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= sizeof(uid_t) * BITS_PER_BYTE,
	.basetype	= &integer_type,
	.print		= uid_type_print,
	.parse		= uid_type_parse,
};

static void gid_type_print(const struct expr *expr, struct output_ctx *octx)
{
	struct group *gr;

	if (octx->numeric < NFT_NUMERIC_ALL) {
		uint32_t gid = mpz_get_uint32(expr->value);

		gr = getgrgid(gid);
		if (gr != NULL)
			nft_print(octx, "\"%s\"", gr->gr_name);
		else
			nft_print(octx, "%u", gid);
		return;
	}
	expr_basetype(expr)->print(expr, octx);
}

static struct error_record *gid_type_parse(const struct expr *sym,
					   struct expr **res)
{
	struct group *gr;
	uint64_t gid;
	char *endptr = NULL;

	gr = getgrnam(sym->identifier);
	if (gr != NULL)
		gid = gr->gr_gid;
	else {
		gid = strtoull(sym->identifier, &endptr, 0);
		if (gid > UINT32_MAX)
			return error(&sym->location, "Value too large");
		else if (*endptr)
			return error(&sym->location, "Group does not exist");
	}

	*res = constant_expr_alloc(&sym->location, sym->dtype,
				   BYTEORDER_HOST_ENDIAN,
				   sizeof(gr->gr_gid) * BITS_PER_BYTE, &gid);
	return NULL;
}

const struct datatype gid_type = {
	.type		= TYPE_GID,
	.name		= "gid",
	.desc		= "group ID",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= sizeof(gid_t) * BITS_PER_BYTE,
	.basetype	= &integer_type,
	.print		= gid_type_print,
	.parse		= gid_type_parse,
};

static const struct symbol_table pkttype_type_tbl = {
	.base		= BASE_DECIMAL,
	.symbols	= {
		SYMBOL("host", PACKET_HOST),
		SYMBOL("unicast", PACKET_HOST), /* backwards compat */
		SYMBOL("broadcast", PACKET_BROADCAST),
		SYMBOL("multicast", PACKET_MULTICAST),
		SYMBOL("other", PACKET_OTHERHOST),
		SYMBOL_LIST_END,
	},
};

static void pkttype_type_print(const struct expr *expr, struct output_ctx *octx)
{
	return symbolic_constant_print(&pkttype_type_tbl, expr, false, octx);
}

const struct datatype pkttype_type = {
	.type		= TYPE_PKTTYPE,
	.name		= "pkt_type",
	.desc		= "packet type",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= BITS_PER_BYTE,
	.basetype	= &integer_type,
	.print		= pkttype_type_print,
	.sym_tbl	= &pkttype_type_tbl,
};

static struct symbol_table *devgroup_tbl;
void devgroup_table_init(void)
{
	devgroup_tbl = rt_symbol_table_init("/etc/iproute2/group");
}

void devgroup_table_exit(void)
{
	rt_symbol_table_free(devgroup_tbl);
}

static void devgroup_type_print(const struct expr *expr,
				 struct output_ctx *octx)
{
	return symbolic_constant_print(devgroup_tbl, expr, true, octx);
}

static struct error_record *devgroup_type_parse(const struct expr *sym,
						struct expr **res)
{
	return symbolic_constant_parse(sym, devgroup_tbl, res);
}

const struct datatype devgroup_type = {
	.type		= TYPE_DEVGROUP,
	.name		= "devgroup",
	.desc		= "devgroup name",
	.byteorder	= BYTEORDER_HOST_ENDIAN,
	.size		= 4 * BITS_PER_BYTE,
	.basetype	= &integer_type,
	.print		= devgroup_type_print,
	.parse		= devgroup_type_parse,
	.flags		= DTYPE_F_PREFIX,
};

static const struct meta_template meta_templates[] = {
	[NFT_META_LEN]		= META_TEMPLATE("length",    &integer_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_PROTOCOL]	= META_TEMPLATE("protocol",  &ethertype_type,
						2 * 8, BYTEORDER_BIG_ENDIAN),
	[NFT_META_NFPROTO]	= META_TEMPLATE("nfproto",   &nfproto_type,
						1 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_L4PROTO]	= META_TEMPLATE("l4proto",   &inet_protocol_type,
						1 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_PRIORITY]	= META_TEMPLATE("priority",  &tchandle_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_MARK]		= META_TEMPLATE("mark",      &mark_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_IIF]		= META_TEMPLATE("iif",       &ifindex_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_IIFNAME]	= META_TEMPLATE("iifname",   &string_type,
						IFNAMSIZ * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_IIFTYPE]	= META_TEMPLATE("iiftype",   &arphrd_type,
						2 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_OIF]		= META_TEMPLATE("oif",	     &ifindex_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_OIFNAME]	= META_TEMPLATE("oifname",   &string_type,
						IFNAMSIZ * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_OIFTYPE]	= META_TEMPLATE("oiftype",   &arphrd_type,
						2 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_SKUID]	= META_TEMPLATE("skuid",     &uid_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_SKGID]	= META_TEMPLATE("skgid",     &gid_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_NFTRACE]	= META_TEMPLATE("nftrace",   &integer_type,
						1    , BYTEORDER_HOST_ENDIAN),
	[NFT_META_RTCLASSID]	= META_TEMPLATE("rtclassid", &realm_type,
						4 * 8, BYTEORDER_HOST_ENDIAN),
	[NFT_META_BRI_IIFNAME]	= META_TEMPLATE("ibriport",  &string_type,
						IFNAMSIZ * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_BRI_OIFNAME]	= META_TEMPLATE("obriport",  &string_type,
						IFNAMSIZ * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_PKTTYPE]	= META_TEMPLATE("pkttype",   &pkttype_type,
						BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_CPU]		= META_TEMPLATE("cpu",	     &integer_type,
						4 * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_IIFGROUP]	= META_TEMPLATE("iifgroup",  &devgroup_type,
						4 * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_OIFGROUP]	= META_TEMPLATE("oifgroup",  &devgroup_type,
						4 * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_CGROUP]	= META_TEMPLATE("cgroup",    &integer_type,
						4 * BITS_PER_BYTE,
						BYTEORDER_HOST_ENDIAN),
	[NFT_META_PRANDOM]	= META_TEMPLATE("random",    &integer_type,
						4 * BITS_PER_BYTE,
						BYTEORDER_BIG_ENDIAN), /* avoid conversion; doesn't have endianess */
	[NFT_META_SECPATH]	= META_TEMPLATE("secpath", &boolean_type,
						BITS_PER_BYTE, BYTEORDER_HOST_ENDIAN),
};

static bool meta_key_is_qualified(enum nft_meta_keys key)
{
	switch (key) {
	case NFT_META_LEN:
	case NFT_META_NFPROTO:
	case NFT_META_L4PROTO:
	case NFT_META_PROTOCOL:
	case NFT_META_PRIORITY:
	case NFT_META_PRANDOM:
	case NFT_META_SECPATH:
		return true;
	default:
		return false;
	}
}

static void meta_expr_print(const struct expr *expr, struct output_ctx *octx)
{
	if (meta_key_is_qualified(expr->meta.key))
		nft_print(octx, "meta %s",
			  meta_templates[expr->meta.key].token);
	else
		nft_print(octx, "%s",
			  meta_templates[expr->meta.key].token);
}

static bool meta_expr_cmp(const struct expr *e1, const struct expr *e2)
{
	return e1->meta.key == e2->meta.key;
}

static void meta_expr_clone(struct expr *new, const struct expr *expr)
{
	new->meta.key = expr->meta.key;
	new->meta.base = expr->meta.base;
}

/**
 * meta_expr_pctx_update - update protocol context based on meta match
 *
 * @ctx:	protocol context
 * @expr:	relational meta expression
 *
 * Update LL protocol context based on IIFTYPE meta match in non-LL hooks.
 */
static void meta_expr_pctx_update(struct proto_ctx *ctx,
				  const struct expr *expr)
{
	const struct hook_proto_desc *h = &hook_proto_desc[ctx->family];
	const struct expr *left = expr->left, *right = expr->right;
	const struct proto_desc *desc;
	uint8_t protonum;

	switch (left->meta.key) {
	case NFT_META_IIFTYPE:
		if (h->base < PROTO_BASE_NETWORK_HDR &&
		    ctx->family != NFPROTO_INET &&
		    ctx->family != NFPROTO_NETDEV)
			return;

		desc = proto_dev_desc(mpz_get_uint16(right->value));
		if (desc == NULL)
			desc = &proto_unknown;

		proto_ctx_update(ctx, PROTO_BASE_LL_HDR, &expr->location, desc);
		break;
	case NFT_META_NFPROTO:
		protonum = mpz_get_uint8(right->value);
		desc = proto_find_upper(h->desc, protonum);
		if (desc == NULL) {
			desc = &proto_unknown;

			if (protonum == ctx->family &&
			    h->base == PROTO_BASE_NETWORK_HDR)
				desc = h->desc;
		}

		proto_ctx_update(ctx, PROTO_BASE_NETWORK_HDR, &expr->location, desc);
		break;
	case NFT_META_L4PROTO:
		desc = proto_find_upper(&proto_inet_service,
					mpz_get_uint8(right->value));
		if (desc == NULL)
			desc = &proto_unknown;

		proto_ctx_update(ctx, PROTO_BASE_TRANSPORT_HDR, &expr->location, desc);
		break;
	case NFT_META_PROTOCOL:
		if (h->base < PROTO_BASE_NETWORK_HDR && ctx->family != NFPROTO_NETDEV)
			return;

		desc = proto_find_upper(h->desc, ntohs(mpz_get_uint16(right->value)));
		if (desc == NULL)
			desc = &proto_unknown;

		proto_ctx_update(ctx, PROTO_BASE_NETWORK_HDR, &expr->location, desc);
		break;
	default:
		break;
	}
}

static const struct expr_ops meta_expr_ops = {
	.type		= EXPR_META,
	.name		= "meta",
	.print		= meta_expr_print,
	.cmp		= meta_expr_cmp,
	.clone		= meta_expr_clone,
	.pctx_update	= meta_expr_pctx_update,
};

struct expr *meta_expr_alloc(const struct location *loc, enum nft_meta_keys key)
{
	const struct meta_template *tmpl = &meta_templates[key];
	struct expr *expr;

	expr = expr_alloc(loc, &meta_expr_ops, tmpl->dtype,
			  tmpl->byteorder, tmpl->len);
	expr->meta.key = key;

	switch (key) {
	case NFT_META_IIFTYPE:
		expr->flags |= EXPR_F_PROTOCOL;
		break;
	case NFT_META_NFPROTO:
		expr->flags |= EXPR_F_PROTOCOL;
		expr->meta.base = PROTO_BASE_LL_HDR;
		break;
	case NFT_META_L4PROTO:
		expr->flags |= EXPR_F_PROTOCOL;
		expr->meta.base = PROTO_BASE_NETWORK_HDR;
		break;
	case NFT_META_PROTOCOL:
		expr->flags |= EXPR_F_PROTOCOL;
		expr->meta.base = PROTO_BASE_LL_HDR;
		break;
	default:
		break;
	}

	return expr;
}

static void meta_stmt_print(const struct stmt *stmt, struct output_ctx *octx)
{
	if (meta_key_is_qualified(stmt->meta.key))
		nft_print(octx, "meta %s set ",
			  meta_templates[stmt->meta.key].token);
	else
		nft_print(octx, "%s set ",
			  meta_templates[stmt->meta.key].token);

	expr_print(stmt->meta.expr, octx);
}

static const struct stmt_ops meta_stmt_ops = {
	.type		= STMT_META,
	.name		= "meta",
	.print		= meta_stmt_print,
};

struct stmt *meta_stmt_alloc(const struct location *loc, enum nft_meta_keys key,
			     struct expr *expr)
{
	struct stmt *stmt;

	stmt = stmt_alloc(loc, &meta_stmt_ops);
	stmt->meta.key	= key;
	stmt->meta.tmpl	= &meta_templates[key];
	stmt->meta.expr	= expr;
	return stmt;
}

/*
 * @expr:	payload expression
 * @res:	dependency expression
 *
 * Generate a NFT_META_IIFTYPE expression to check for ethernet frames.
 * Only works on input path.
 */
struct stmt *meta_stmt_meta_iiftype(const struct location *loc, uint16_t type)
{
	struct expr *dep, *left, *right;

	left = meta_expr_alloc(loc, NFT_META_IIFTYPE);
	right = constant_expr_alloc(loc, &arphrd_type,
				    BYTEORDER_HOST_ENDIAN,
				    2 * BITS_PER_BYTE, &type);

	dep = relational_expr_alloc(loc, OP_EQ, left, right);
	return expr_stmt_alloc(&dep->location, dep);
}

struct error_record *meta_key_parse(const struct location *loc,
                                    const char *str,
                                    unsigned int *value)
{
	int ret, len, offset = 0;
	const char *sep = "";
	unsigned int i;
	char buf[1024];
	size_t size;

	for (i = 0; i < array_size(meta_templates); i++) {
		if (!meta_templates[i].token || strcmp(meta_templates[i].token, str))
			continue;

		*value = i;
		return NULL;
	}

	len = (int)sizeof(buf);
	size = sizeof(buf);

	for (i = 0; i < array_size(meta_templates); i++) {
		if (!meta_templates[i].token)
			continue;

		if (offset)
			sep = ", ";

		ret = snprintf(buf+offset, len, "%s%s", sep, meta_templates[i].token);
		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
		assert(offset < (int)sizeof(buf));
	}

	return error(loc, "syntax error, unexpected %s, known keys are %s", str, buf);
}