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path: root/src/lib/ecore_con/dns.c
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/* ==========================================================================
 * dns.c - Recursive, Reentrant DNS Resolver.
 * --------------------------------------------------------------------------
 * Copyright (c) 2008, 2009, 2010, 2012, 2013  William Ahern
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to permit
 * persons to whom the Software is furnished to do so, subject to the
 * following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
 * NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 * ==========================================================================
 */
#if !defined(__FreeBSD__) && !defined(__sun)
#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE	600
#endif

#undef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE

#undef _BSD_SOURCE
#define _BSD_SOURCE

#undef _DARWIN_C_SOURCE
#define _DARWIN_C_SOURCE

#undef _NETBSD_SOURCE
#define _NETBSD_SOURCE
#endif

#include <stddef.h>		/* offsetof() */
#ifdef _WIN32
#define uint32_t unsigned int
#else
#include <stdint.h>		/* uint32_t */
#endif
#include <stdlib.h>		/* malloc(3) realloc(3) free(3) rand(3) random(3) arc4random(3) */
#include <stdio.h>		/* FILE fopen(3) fclose(3) getc(3) rewind(3) */

#include <string.h>		/* memcpy(3) strlen(3) memmove(3) memchr(3) memcmp(3) strchr(3) strsep(3) strcspn(3) */
#include <strings.h>		/* strcasecmp(3) strncasecmp(3) */

#include <ctype.h>		/* isspace(3) isdigit(3) */

#include <time.h>		/* time_t time(2) difftime(3) */

#include <signal.h>		/* SIGPIPE sigemptyset(3) sigaddset(3) sigpending(2) sigprocmask(2) pthread_sigmask(3) sigtimedwait(2) */

#include <errno.h>		/* errno EINVAL ENOENT */

#undef NDEBUG
#include <assert.h>		/* assert(3) */

#if _WIN32
#ifndef FD_SETSIZE
#define FD_SETSIZE 256
#endif
#include <winsock2.h>
#include <ws2tcpip.h>
#else
#include <sys/types.h>		/* FD_SETSIZE socklen_t */
#include <sys/select.h>		/* FD_ZERO FD_SET fd_set select(2) */
#include <sys/socket.h>		/* AF_INET AF_INET6 AF_UNIX struct sockaddr struct sockaddr_in struct sockaddr_in6 socket(2) */

#if defined(AF_UNIX)
#include <sys/un.h>		/* struct sockaddr_un */
#endif

#include <fcntl.h>		/* F_SETFD F_GETFL F_SETFL O_NONBLOCK fcntl(2) */

#include <unistd.h>		/* _POSIX_THREADS gethostname(3) close(2) */

#include <poll.h>		/* POLLIN POLLOUT */

#include <netinet/in.h>		/* struct sockaddr_in struct sockaddr_in6 */

#include <arpa/inet.h>		/* inet_pton(3) inet_ntop(3) htons(3) ntohs(3) */

#include <netdb.h>		/* struct addrinfo */
#endif

#include "dns.h"


/*
 * C O M P I L E R  A N N O T A T I O N S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if __GNUC__
#define DNS_NOTUSED __attribute__((unused))
#else
#define DNS_NOTUSED
#endif

#if __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-parameter"
#elif (__GNUC__ == 4 && __GNUC_MINOR__ >= 6) || __GNUC__ > 4
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#endif


/*
 * S T A N D A R D  M A C R O S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef MIN
#define MIN(a, b)	(((a) < (b))? (a) : (b))
#endif


#ifndef MAX
#define MAX(a, b)	(((a) > (b))? (a) : (b))
#endif


#ifndef lengthof
#define lengthof(a)	(sizeof (a) / sizeof (a)[0])
#endif

#ifndef endof
#define endof(a)	(&(a)[lengthof((a))])
#endif


/*
 * M I S C E L L A N E O U S  C O M P A T
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if _WIN32 || _WIN64
#define PRIuZ "Iu"
#else
#define PRIuZ "zu"
#endif

#ifndef DNS_THREAD_SAFE
#if (defined _REENTRANT || defined _THREAD_SAFE) && _POSIX_THREADS > 0
#define DNS_THREAD_SAFE 1
#else
#define DNS_THREAD_SAFE 0
#endif
#endif


/*
 * D E B U G  M A C R O S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

int dns_debug = 0;

#if DNS_DEBUG

#undef DNS_DEBUG
#define DNS_DEBUG dns_debug

#define DNS_SAY_(fmt, ...) \
	do { if (DNS_DEBUG > 0) fprintf(stderr, fmt "%.1s", __func__, __LINE__, __VA_ARGS__); } while (0)
#define DNS_SAY(...) DNS_SAY_("@@ (%s:%d) " __VA_ARGS__, "\n")
#define DNS_HAI DNS_SAY("HAI")

#define DNS_SHOW_(P, fmt, ...)	do {					\
	if (DNS_DEBUG > 1) {						\
	fprintf(stderr, "@@ BEGIN * * * * * * * * * * * *\n");		\
	fprintf(stderr, "@@ " fmt "%.0s\n", __VA_ARGS__);		\
	dns_p_dump((P), stderr);					\
	fprintf(stderr, "@@ END * * * * * * * * * * * * *\n\n");	\
	}								\
} while (0)

#define DNS_SHOW(...)	DNS_SHOW_(__VA_ARGS__, "")

#else /* !DNS_DEBUG */

#undef DNS_DEBUG
#define DNS_DEBUG 0

#define DNS_SAY(...)
#define DNS_HAI
#define DNS_SHOW(...)

#endif /* DNS_DEBUG */


/*
 * V E R S I O N  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

const char *dns_vendor(void) {
	return DNS_VENDOR;
} /* dns_vendor() */


int dns_v_rel(void) {
	return DNS_V_REL;
} /* dns_v_rel() */


int dns_v_abi(void) {
	return DNS_V_ABI;
} /* dns_v_abi() */


int dns_v_api(void) {
	return DNS_V_API;
} /* dns_v_api() */


/*
 * E R R O R  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if _WIN32

#define DNS_EINTR	WSAEINTR
#define DNS_EINPROGRESS	WSAEINPROGRESS
#define DNS_EISCONN	WSAEISCONN
#define DNS_EWOULDBLOCK	WSAEWOULDBLOCK
#define DNS_EALREADY	WSAEALREADY
#define DNS_EAGAIN	EAGAIN
#define DNS_ETIMEDOUT	WSAETIMEDOUT

#define dns_syerr()	((int)GetLastError())
#define dns_soerr()	((int)WSAGetLastError())

#else

#define DNS_EINTR	EINTR
#define DNS_EINPROGRESS	EINPROGRESS
#define DNS_EISCONN	EISCONN
#define DNS_EWOULDBLOCK	EWOULDBLOCK
#define DNS_EALREADY	EALREADY
#define DNS_EAGAIN	EAGAIN
#define DNS_ETIMEDOUT	ETIMEDOUT

#define dns_syerr()	errno
#define dns_soerr()	errno

#endif


const char *dns_strerror(int error) {
	switch (error) {
	case DNS_ENOBUFS:
		return "DNS packet buffer too small";
	case DNS_EILLEGAL:
		return "Illegal DNS RR name or data";
	case DNS_EORDER:
		return "Attempt to push RR out of section order";
	case DNS_ESECTION:
		return "Invalid section specified";
	case DNS_EUNKNOWN:
		return "Unknown DNS error";
	case DNS_EADDRESS:
		return "Invalid textual address form";
	default:
		return strerror(error);
	} /* switch() */
} /* dns_strerror() */


/*
 * A T O M I C  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

DNS_NOTUSED static void dns_atomic_fence(void) {
	return;
} /* dns_atomic_fence() */


static unsigned dns_atomic_inc(dns_atomic_t *i) {
	return (*i)++;
} /* dns_atomic_inc() */


static unsigned dns_atomic_dec(dns_atomic_t *i) {
	return (*i)--;
} /* dns_atomic_dec() */


static unsigned dns_atomic_load(dns_atomic_t *i) {
	return *i;
} /* dns_atomic_load() */


DNS_NOTUSED static unsigned dns_atomic_store(dns_atomic_t *i, unsigned n) {
	unsigned o;

	o	= dns_atomic_load(i);
	*i	= n;
	return o;
} /* dns_atomic_store() */


/*
 * C R Y P T O  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * P R N G 
 */

#ifndef DNS_RANDOM
#if defined(HAVE_ARC4RANDOM)	\
 || defined(__OpenBSD__)	\
 || defined(__FreeBSD__)	\
 || defined(__NetBSD__)		\
 || defined(__APPLE__)
#define DNS_RANDOM	arc4random
#elif __linux
#define DNS_RANDOM	random
#else
#define DNS_RANDOM	rand
#endif
#endif

#define DNS_RANDOM_arc4random	1
#define DNS_RANDOM_random	2
#define DNS_RANDOM_rand		3
#define DNS_RANDOM_RAND_bytes	4

#define DNS_RANDOM_OPENSSL	(DNS_RANDOM_RAND_bytes == DNS_PP_XPASTE(DNS_RANDOM_, DNS_RANDOM))

#if DNS_RANDOM_OPENSSL
#include <openssl/rand.h>
#endif

static unsigned dns_random_(void) {
#if DNS_RANDOM_OPENSSL
	unsigned r;

	assert(1 == RAND_bytes((unsigned char *)&r, sizeof r));

	return r;
#else
	return DNS_RANDOM();
#endif
} /* dns_random_() */

unsigned (*dns_random)(void) __attribute__((weak))	= &dns_random_;


/*
 * P E R M U T A T I O N  G E N E R A T O R
 */

#define DNS_K_TEA_KEY_SIZE	16
#define DNS_K_TEA_BLOCK_SIZE	8
#define DNS_K_TEA_CYCLES	32
#define DNS_K_TEA_MAGIC		0x9E3779B9U

struct dns_k_tea {
	uint32_t key[DNS_K_TEA_KEY_SIZE / sizeof (uint32_t)];
	unsigned cycles;
}; /* struct dns_k_tea */


static void dns_k_tea_init(struct dns_k_tea *tea, uint32_t key[], unsigned cycles) {
	memcpy(tea->key, key, sizeof tea->key);

	tea->cycles	= (cycles)? cycles : DNS_K_TEA_CYCLES;
} /* dns_k_tea_init() */


static void dns_k_tea_encrypt(struct dns_k_tea *tea, uint32_t v[], uint32_t *w) {
	uint32_t y, z, sum, n;

	y	= v[0];
	z	= v[1];
	sum	= 0;

	for (n = 0; n < tea->cycles; n++) {
		sum	+= DNS_K_TEA_MAGIC;
		y	+= ((z << 4) + tea->key[0]) ^ (z + sum) ^ ((z >> 5) + tea->key[1]);
		z	+= ((y << 4) + tea->key[2]) ^ (y + sum) ^ ((y >> 5) + tea->key[3]);
	}

	w[0]	= y;
	w[1]	= z;

	return /* void */;
} /* dns_k_tea_encrypt() */


/*
 * Permutation generator, based on a Luby-Rackoff Feistel construction.
 *
 * Specifically, this is a generic balanced Feistel block cipher using TEA
 * (another block cipher) as the pseudo-random function, F. At best it's as
 * strong as F (TEA), notwithstanding the seeding. F could be AES, SHA-1, or
 * perhaps Bernstein's Salsa20 core; I am naively trying to keep things
 * simple.
 *
 * The generator can create a permutation of any set of numbers, as long as
 * the size of the set is an even power of 2. This limitation arises either
 * out of an inherent property of balanced Feistel constructions, or by my
 * own ignorance. I'll tackle an unbalanced construction after I wrap my
 * head around Schneier and Kelsey's paper.
 *
 * CAVEAT EMPTOR. IANAC.
 */
#define DNS_K_PERMUTOR_ROUNDS	8

struct dns_k_permutor {
	unsigned stepi, length, limit;
	unsigned shift, mask, rounds;

	struct dns_k_tea tea;
}; /* struct dns_k_permutor */


static inline unsigned dns_k_permutor_powof(unsigned n) {
	unsigned m, i = 0;

	for (m = 1; m < n; m <<= 1, i++)
		;;

	return i;
} /* dns_k_permutor_powof() */

static void dns_k_permutor_init(struct dns_k_permutor *p, unsigned low, unsigned high) {
	uint32_t key[DNS_K_TEA_KEY_SIZE / sizeof (uint32_t)];
	unsigned width, i;

	p->stepi	= 0;

	p->length	= (high - low) + 1;
	p->limit	= high;

	width		= dns_k_permutor_powof(p->length);
	width		+= width % 2;

	p->shift	= width / 2;
	p->mask		= (1U << p->shift) - 1;
	p->rounds	= DNS_K_PERMUTOR_ROUNDS;

	for (i = 0; i < lengthof(key); i++)
		key[i]	= dns_random();

	dns_k_tea_init(&p->tea, key, 0);

	return /* void */;
} /* dns_k_permutor_init() */


static unsigned dns_k_permutor_F(struct dns_k_permutor *p, unsigned k, unsigned x) {
	uint32_t in[DNS_K_TEA_BLOCK_SIZE / sizeof (uint32_t)], out[DNS_K_TEA_BLOCK_SIZE / sizeof (uint32_t)];

	memset(in, '\0', sizeof in);

	in[0]	= k;
	in[1]	= x;

	dns_k_tea_encrypt(&p->tea, in, out);

	return p->mask & out[0];
} /* dns_k_permutor_F() */


static unsigned dns_k_permutor_E(struct dns_k_permutor *p, unsigned n) {
	unsigned l[2], r[2];
	unsigned i;

	i	= 0;
	l[i]	= p->mask & (n >> p->shift);
	r[i]	= p->mask & (n >> 0);

	do {
		l[(i + 1) % 2]	= r[i % 2];
		r[(i + 1) % 2]	= l[i % 2] ^ dns_k_permutor_F(p, i, r[i % 2]);

		i++;
	} while (i < p->rounds - 1);

	return ((l[i % 2] & p->mask) << p->shift) | ((r[i % 2] & p->mask) << 0);
} /* dns_k_permutor_E() */


DNS_NOTUSED static unsigned dns_k_permutor_D(struct dns_k_permutor *p, unsigned n) {
	unsigned l[2], r[2];
	unsigned i;

	i		= p->rounds - 1;
	l[i % 2]	= p->mask & (n >> p->shift);
	r[i % 2]	= p->mask & (n >> 0);

	do {
		i--;

		r[i % 2]	= l[(i + 1) % 2];
		l[i % 2]	= r[(i + 1) % 2] ^ dns_k_permutor_F(p, i, l[(i + 1) % 2]);
	} while (i > 0);

	return ((l[i % 2] & p->mask) << p->shift) | ((r[i % 2] & p->mask) << 0);
} /* dns_k_permutor_D() */


static unsigned dns_k_permutor_step(struct dns_k_permutor *p) {
	unsigned n;

	do {
		n	= dns_k_permutor_E(p, p->stepi++);
	} while (n >= p->length);

	return n + (p->limit + 1 - p->length);
} /* dns_k_permutor_step() */


/*
 * Simple permutation box. Useful for shuffling rrsets from an iterator.
 * Uses AES s-box to provide good diffusion.
 *
 * Seems to pass muster under runs test.
 *
 * $ for i in 0 1 2 3 4 5 6 7 8 9; do ./dns shuffle-16 > /tmp/out; done
 * $ R -q -f /dev/stdin 2>/dev/null <<-EOF | awk '/p-value/{ print $8 }'
 * 	library(lawstat)
 * 	runs.test(scan(file="/tmp/out"))
 * EOF
 */
static unsigned short dns_k_shuffle16(unsigned short n, unsigned s) {
	static const unsigned char sbox[256] =
	{ 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
	  0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
	  0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
	  0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
	  0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
	  0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
	  0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
	  0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
	  0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
	  0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
	  0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
	  0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
	  0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
	  0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
	  0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
	  0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
	  0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
	  0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
	  0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
	  0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
	  0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
	  0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
	  0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
	  0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
	  0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
	  0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
	  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
	  0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
	  0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
	  0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
	  0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
	  0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };
	unsigned char a, b;
	unsigned i;

	a = 0xff & (n >> 0);
	b = 0xff & (n >> 8);

	for (i = 0; i < 4; i++) {
		a ^= 0xff & s;
		a = sbox[a] ^ b;
		b = sbox[b] ^ a;
		s >>= 8;
	}

	return ((0xff00 & (a << 8)) | (0x00ff & (b << 0)));
} /* dns_k_shuffle16() */


/*
 * U T I L I T Y  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#define DNS_MAXINTERVAL 300

struct dns_clock {
	time_t sample, elapsed;
}; /* struct dns_clock */

static void dns_begin(struct dns_clock *clk) {
	clk->sample = time(0);
	clk->elapsed = 0;
} /* dns_begin() */

static time_t dns_elapsed(struct dns_clock *clk) {
	time_t curtime;

	if ((time_t)-1 == time(&curtime))
		return clk->elapsed;

	if (curtime > clk->sample)
		clk->elapsed += (time_t)MIN(difftime(curtime, clk->sample), DNS_MAXINTERVAL);

	clk->sample = curtime;

	return clk->elapsed;
} /* dns_elapsed() */


static size_t dns_af_len(int af) {
	static const size_t table[AF_MAX]	= {
		[AF_INET6]	= sizeof (struct sockaddr_in6),
		[AF_INET]	= sizeof (struct sockaddr_in),
#if defined(AF_UNIX) && !defined(_WIN32)
		[AF_UNIX]	= sizeof (struct sockaddr_un),
#endif
	};

	return table[af];
} /* dns_af_len() */

#define dns_sa_len(sa)		dns_af_len(dns_sa_family(sa))


#define DNS_SA_NOPORT	&dns_sa_noport
static unsigned short dns_sa_noport;

unsigned short *dns_sa_port(int af, void *sa) {
	switch (af) {
	case AF_INET6:
		return &((struct sockaddr_in6 *)sa)->sin6_port;
	case AF_INET:
		return &((struct sockaddr_in *)sa)->sin_port;
	default:
		return DNS_SA_NOPORT;
	}
} /* dns_sa_port() */


void *dns_sa_addr(int af, void *sa) {
	switch (af) {
	case AF_INET6:
		return &((struct sockaddr_in6 *)sa)->sin6_addr;
	case AF_INET:
		return &((struct sockaddr_in *)sa)->sin_addr;
	default:
		return 0;
	}
} /* dns_sa_addr() */


#if _WIN32
static int dns_inet_pton(int af, const void *src, void *dst) {
	union { struct sockaddr_in sin; struct sockaddr_in6 sin6; } u;

	u.sin.sin_family	= af;

	if (0 != WSAStringToAddressA((void *)src, af, (void *)0, (struct sockaddr *)&u, &(int){ sizeof u }))
		return -1;

	switch (af) {
	case AF_INET6:
		*(struct in6_addr *)dst	= u.sin6.sin6_addr;

		return 1;
	case AF_INET:
		*(struct in_addr *)dst	= u.sin.sin_addr;

		return 1;
	default:
		return 0;
	}
} /* dns_inet_pton() */

const char *dns_inet_ntop(int af, const void *src, void *dst, unsigned long lim) {
	union { struct sockaddr_in sin; struct sockaddr_in6 sin6; } u;

	/* NOTE: WSAAddressToString will print .sin_port unless zeroed. */
	memset(&u, 0, sizeof u);

	u.sin.sin_family	= af;

	switch (af) {
	case AF_INET6:
		u.sin6.sin6_addr	= *(struct in6_addr *)src;
		break;
	case AF_INET:
		u.sin.sin_addr		= *(struct in_addr *)src;

		break;
	default:
		return 0;
	}

	if (0 != WSAAddressToStringA((struct sockaddr *)&u, dns_sa_len(&u), (void *)0, dst, &lim))
		return 0;

	return dst;
} /* dns_inet_ntop() */
#endif


static dns_error_t dns_pton(int af, const void *src, void *dst) {
	switch (dns_inet_pton(af, src, dst)) {
	case 1:
		return 0;
	case -1:
		return dns_soerr();
	default:
		return DNS_EADDRESS;
	}
} /* dns_pton() */


static dns_error_t dns_ntop(int af, const void *src, void *dst, unsigned long lim) {
	return (dns_inet_ntop(af, src, dst, lim))? 0 : dns_soerr();
} /* dns_ntop() */


size_t dns_strlcpy(char *dst, const char *src, size_t lim) {
	char *d		= dst;
	char *e		= &dst[lim];
	const char *s	= src;

	if (d < e) {
		do {
			if ('\0' == (*d++ = *s++))
				return s - src - 1;
		} while (d < e);

		d[-1]	= '\0';
	}

	while (*s++ != '\0')
		;;

	return s - src - 1;
} /* dns_strlcpy() */


size_t dns_strlcat(char *dst, const char *src, size_t lim) {
	char *d = memchr(dst, '\0', lim);
	char *e = &dst[lim];
	const char *s = src;
	const char *p;

	if (d && d < e) {
		do {
			if ('\0' == (*d++ = *s++))
				return d - dst - 1;
		} while (d < e);

		d[-1] = '\0';
	}

	p = s;

	while (*s++ != '\0')
		;;

	return lim + (s - p - 1);
} /* dns_strlcat() */


#if _WIN32

static char *dns_strsep(char **sp, const char *delim) {
	char *p;

	if (!(p = *sp))
		return 0;

	*sp += strcspn(p, delim);

	if (**sp != '\0') {
		**sp = '\0';
		++*sp;
	} else
		*sp = NULL;

	return p;
} /* dns_strsep() */

#else
#define dns_strsep(...)	strsep(__VA_ARGS__)
#endif


#if _WIN32
#define strcasecmp(...)		_stricmp(__VA_ARGS__)
#define strncasecmp(...)	_strnicmp(__VA_ARGS__)
#endif


static int dns_poll(int fd, short events, int timeout) {
	fd_set rset, wset;

	if (!events)
		return 0;

	assert(fd >= 0 && (unsigned)fd < FD_SETSIZE);

	FD_ZERO(&rset);
	FD_ZERO(&wset);

	if (events & DNS_POLLIN)
		FD_SET(fd, &rset);

	if (events & DNS_POLLOUT)
		FD_SET(fd, &wset);

	select(fd + 1, &rset, &wset, 0, (timeout >= 0)? &(struct timeval){ timeout, 0 } : NULL);

	return 0;
} /* dns_poll() */


#if !_WIN32
DNS_NOTUSED static int dns_sigmask(int how, const sigset_t *set, sigset_t *oset) {
#if DNS_THREAD_SAFE
	return pthread_sigmask(how, set, oset);
#else
	return (0 == sigprocmask(how, set, oset))? 0 : errno;
#endif
} /* dns_sigmask() */
#endif


static long dns_send(int fd, const void *src, size_t lim, int flags) {
#if _WIN32 || !defined SIGPIPE || defined SO_NOSIGPIPE
	return send(fd, src, lim, flags);
#elif defined MSG_NOSIGNAL
	return send(fd, src, lim, flags|MSG_NOSIGNAL);
#elif _POSIX_REALTIME_SIGNALS > 0 /* require sigtimedwait */
	/*
	 * SIGPIPE handling similar to the approach described in
	 * http://krokisplace.blogspot.com/2010/02/suppressing-sigpipe-in-library.html
	 */
	sigset_t pending, blocked, piped;
	long count;
	int saved, error;

	sigemptyset(&pending);
	sigpending(&pending);

	if (!sigismember(&pending, SIGPIPE)) {
		sigemptyset(&piped);
		sigaddset(&piped, SIGPIPE);
		sigemptyset(&blocked);

		if ((error = dns_sigmask(SIG_BLOCK, &piped, &blocked)))
			goto error;
	}

	count = send(fd, src, lim, flags);

	if (!sigismember(&pending, SIGPIPE)) {
		saved = errno;

		if (count == -1 && errno == EPIPE) {
			while (-1 == sigtimedwait(&piped, NULL, &(struct timespec){ 0, 0 }) && errno == EINTR)
				;;
		}

		if ((error = dns_sigmask(SIG_SETMASK, &blocked, NULL)))
			goto error;

		errno = saved;
	}

	return count;
error:
	errno = error;

	return -1;
#else
#error "unable to suppress SIGPIPE"
	return send(fd, src, lim, flags);
#endif
} /* dns_send() */


/*
 * P A C K E T  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

unsigned dns_p_count(struct dns_packet *P, enum dns_section section) {
	unsigned count;

	switch (section) {
	case DNS_S_QD:
		return ntohs(dns_header(P)->qdcount);
	case DNS_S_AN:
		return ntohs(dns_header(P)->ancount);
	case DNS_S_NS:
		return ntohs(dns_header(P)->nscount);
	case DNS_S_AR:
		return ntohs(dns_header(P)->arcount);
	default:
		count = 0;

		if (section & DNS_S_QD)
			count += ntohs(dns_header(P)->qdcount);
		if (section & DNS_S_AN)
			count += ntohs(dns_header(P)->ancount);
		if (section & DNS_S_NS)
			count += ntohs(dns_header(P)->nscount);
		if (section & DNS_S_AR)
			count += ntohs(dns_header(P)->arcount);

		return count;
	}
} /* dns_p_count() */


struct dns_packet *dns_p_init(struct dns_packet *P, size_t size) {
	if (!P)
		return 0;

	assert(size >= offsetof(struct dns_packet, data) + 12);

	memset(P, 0, sizeof *P);
	P->size = size - offsetof(struct dns_packet, data);
	P->end  = 12;

	memset(P->data, '\0', 12);

	return P;
} /* dns_p_init() */


static unsigned short dns_p_qend(struct dns_packet *P) {
	unsigned short qend	= 12;
	unsigned i, count	= dns_p_count(P, DNS_S_QD);

	for (i = 0; i < count && qend < P->end; i++) {
		if (P->end == (qend = dns_d_skip(qend, P)))
			goto invalid;

		if (P->end - qend < 4)
			goto invalid;

		qend	+= 4;
	}

	return MIN(qend, P->end);
invalid:
	return P->end;
} /* dns_p_qend() */


struct dns_packet *dns_p_make(size_t len, int *error) {
	struct dns_packet *P;
	size_t size = dns_p_calcsize(len);

	if (!(P = dns_p_init(malloc(size), size)))
		*error = dns_syerr();

	return P;
} /* dns_p_make() */


int dns_p_grow(struct dns_packet **P) {
	struct dns_packet *tmp;
	size_t size;
	int error;

	if (!*P) {
		if (!(*P = dns_p_make(DNS_P_QBUFSIZ, &error)))
			return error;

		return 0;
	}

	size = dns_p_sizeof(*P);
	size |= size >> 1;
	size |= size >> 2;
	size |= size >> 4;
	size |= size >> 8;
	size++;

	if (size > 65536)
		return DNS_ENOBUFS;

	if (!(tmp = realloc(*P, dns_p_calcsize(size))))
		return dns_syerr();

	tmp->size = size;
	*P = tmp;

	return 0;
} /* dns_p_grow() */


struct dns_packet *dns_p_copy(struct dns_packet *P, const struct dns_packet *P0) {
	if (!P)
		return 0;

	P->end	= MIN(P->size, P0->end);

	memcpy(P->data, P0->data, P->end);

	return P;
} /* dns_p_copy() */


struct dns_packet *dns_p_merge(struct dns_packet *A, enum dns_section Amask, struct dns_packet *B, enum dns_section Bmask, int *error_) {
	size_t bufsiz = MIN(65535, ((A)? A->end : 0) + ((B)? B->end : 0));
	struct dns_packet *M;
	enum dns_section section;
	struct dns_rr rr, mr;
	int error, copy;

	if (!A && B) {
		A = B;
		Amask = Bmask;
		B = 0;
	}

merge:
	if (!(M = dns_p_make(bufsiz, &error)))
		goto error;

	for (section = DNS_S_QD; (DNS_S_ALL & section); section <<= 1) {
		if (A && (section & Amask)) {
			dns_rr_foreach(&rr, A, .section = section) {
				if ((error = dns_rr_copy(M, &rr, A)))
					goto error;
			}
		}

		if (B && (section & Bmask)) {
			dns_rr_foreach(&rr, B, .section = section) {
				copy = 1;

				dns_rr_foreach(&mr, M, .type = rr.type, .section = DNS_S_ALL) {
					if (!(copy = dns_rr_cmp(&rr, B, &mr, M)))
						break;
				}

				if (copy && (error = dns_rr_copy(M, &rr, B)))
					goto error;
			}
		}
	}

	return M;
error:
	free(M); M = 0;

	if (error == DNS_ENOBUFS && bufsiz < 65535) {
		bufsiz = MIN(65535, bufsiz * 2);

		goto merge;
	}

	*error_	= error;

	return 0;
} /* dns_p_merge() */


static unsigned short dns_l_skip(unsigned short, const unsigned char *, size_t);

void dns_p_dictadd(struct dns_packet *P, unsigned short dn) {
	unsigned short lp, lptr, i;

	lp	= dn;

	while (lp < P->end) {
		if (0xc0 == (0xc0 & P->data[lp]) && P->end - lp >= 2 && lp != dn) {
			lptr	= ((0x3f & P->data[lp + 0]) << 8)
				| ((0xff & P->data[lp + 1]) << 0);

			for (i = 0; i < lengthof(P->dict) && P->dict[i]; i++) {
				if (P->dict[i] == lptr) {
					P->dict[i]	= dn;

					return;
				}
			}
		}

		lp	= dns_l_skip(lp, P->data, P->end);
	}

	for (i = 0; i < lengthof(P->dict); i++) {
		if (!P->dict[i]) {
			P->dict[i]	= dn;

			break;
		}
	}
} /* dns_p_dictadd() */


int dns_p_push(struct dns_packet *P, enum dns_section section, const void *dn, size_t dnlen, enum dns_type type, enum dns_class class, unsigned ttl, const void *any) {
	size_t end = P->end;
	int error;

	if ((error = dns_d_push(P, dn, dnlen)))
		goto error;

	if (P->size - P->end < 4)
		goto nobufs;

	P->data[P->end++] = 0xff & (type >> 8);
	P->data[P->end++] = 0xff & (type >> 0);

	P->data[P->end++] = 0xff & (class >> 8);
	P->data[P->end++] = 0xff & (class >> 0);

	if (section == DNS_S_QD)
		goto update;

	if (P->size - P->end < 6)
		goto nobufs;

	P->data[P->end++] = 0x7f & (ttl >> 24);
	P->data[P->end++] = 0xff & (ttl >> 16);
	P->data[P->end++] = 0xff & (ttl >> 8);
	P->data[P->end++] = 0xff & (ttl >> 0);

	if ((error = dns_any_push(P, (union dns_any *)any, type)))
		goto error;

update:
	switch (section) {
	case DNS_S_QD:
		if (dns_p_count(P, DNS_S_AN|DNS_S_NS|DNS_S_AR))
			goto order;

		if (!P->qd.base && (error = dns_p_study(P)))
			goto error;

		dns_header(P)->qdcount = htons(ntohs(dns_header(P)->qdcount) + 1);

		P->qd.end  = P->end;
		P->an.base = P->end;
		P->an.end  = P->end;
		P->ns.base = P->end;
		P->ns.end  = P->end;
		P->ar.base = P->end;
		P->ar.end  = P->end;

		break;
	case DNS_S_AN:
		if (dns_p_count(P, DNS_S_NS|DNS_S_AR))
			goto order;

		if (!P->an.base && (error = dns_p_study(P)))
			goto error;

		dns_header(P)->ancount = htons(ntohs(dns_header(P)->ancount) + 1);

		P->an.end  = P->end;
		P->ns.base = P->end;
		P->ns.end  = P->end;
		P->ar.base = P->end;
		P->ar.end  = P->end;

		break;
	case DNS_S_NS:
		if (dns_p_count(P, DNS_S_AR))
			goto order;

		if (!P->ns.base && (error = dns_p_study(P)))
			goto error;

		dns_header(P)->nscount = htons(ntohs(dns_header(P)->nscount) + 1);

		P->ns.end  = P->end;
		P->ar.base = P->end;
		P->ar.end  = P->end;

		break;
	case DNS_S_AR:
		if (!P->ar.base && (error = dns_p_study(P)))
			goto error;

		dns_header(P)->arcount = htons(ntohs(dns_header(P)->arcount) + 1);

		P->ar.end = P->end;

		break;
	default:
		error = DNS_ESECTION;

		goto error;
	} /* switch() */

	return 0;
nobufs:
	error = DNS_ENOBUFS;

	goto error;
order:
	error = DNS_EORDER;

	goto error;
error:
	P->end = end;

	return error;
} /* dns_p_push() */


static void dns_p_dump3(struct dns_packet *P, struct dns_rr_i *I, FILE *fp) {
	enum dns_section section;
	struct dns_rr rr;
	int error;
	union dns_any any;
	char pretty[sizeof any * 2];
	size_t len;

	fputs(";; [HEADER]\n", fp);
	fprintf(fp, ";;     qr : %s(%d)\n", (dns_header(P)->qr)? "RESPONSE" : "QUERY", dns_header(P)->qr);
	fprintf(fp, ";; opcode : %s(%d)\n", dns_stropcode(dns_header(P)->opcode), dns_header(P)->opcode);
	fprintf(fp, ";;     aa : %s(%d)\n", (dns_header(P)->aa)? "AUTHORITATIVE" : "NON-AUTHORITATIVE", dns_header(P)->aa);
	fprintf(fp, ";;     tc : %s(%d)\n", (dns_header(P)->tc)? "TRUNCATED" : "NOT-TRUNCATED", dns_header(P)->tc);
	fprintf(fp, ";;     rd : %s(%d)\n", (dns_header(P)->rd)? "RECURSION-DESIRED" : "RECURSION-NOT-DESIRED", dns_header(P)->rd);
	fprintf(fp, ";;     ra : %s(%d)\n", (dns_header(P)->ra)? "RECURSION-ALLOWED" : "RECURSION-NOT-ALLOWED", dns_header(P)->ra);
	fprintf(fp, ";;  rcode : %s(%d)\n", dns_strrcode(dns_header(P)->rcode), dns_header(P)->rcode);

	section	= 0;

	while (dns_rr_grep(&rr, 1, I, P, &error)) {
		if (section != rr.section)
			fprintf(fp, "\n;; [%s:%d]\n", dns_strsection(rr.section), dns_p_count(P, rr.section));

		if ((len = dns_rr_print(pretty, sizeof pretty, &rr, P, &error)))
			fprintf(fp, "%s\n", pretty);

		section	= rr.section;
	}
} /* dns_p_dump3() */


void dns_p_dump(struct dns_packet *P, FILE *fp) {
	dns_p_dump3(P, dns_rr_i_new(P, .section = 0), fp);
} /* dns_p_dump() */


static void dns_s_unstudy(struct dns_s_memo *m)
	{ m->base = 0; m->end = 0; }

static void dns_p_unstudy(struct dns_packet *P) {
	dns_s_unstudy(&P->qd);
	dns_s_unstudy(&P->an);
	dns_s_unstudy(&P->ns);
	dns_s_unstudy(&P->ar);
} /* dns_p_unstudy() */

static int dns_s_study(struct dns_s_memo *m, enum dns_section section, unsigned base, struct dns_packet *P) {
	unsigned short count, rp;

	count = dns_p_count(P, section);

	for (rp = base; count && rp < P->end; count--)
		rp = dns_rr_skip(rp, P);

	m->base = base;
	m->end  = rp;

	return 0;
} /* dns_s_study() */

int dns_p_study(struct dns_packet *P) {
	int error;

	if ((error = dns_s_study(&P->qd, DNS_S_QD, 12, P)))
		goto error;

	if ((error = dns_s_study(&P->an, DNS_S_AN, P->qd.end, P)))
		goto error;

	if ((error = dns_s_study(&P->ns, DNS_S_NS, P->an.end, P)))
		goto error;

	if ((error = dns_s_study(&P->ar, DNS_S_AR, P->ns.end, P)))
		goto error;

	return 0;
error:
	dns_p_unstudy(P);

	return error;
} /* dns_p_study() */


/*
 * D O M A I N  N A M E  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef DNS_D_MAXPTRS
#define DNS_D_MAXPTRS	127	/* Arbitrary; possible, valid depth is something like packet size / 2 + fudge. */
#endif

static size_t dns_l_expand(unsigned char *dst, size_t lim, unsigned short src, unsigned short *nxt, const unsigned char *data, size_t end) {
	unsigned short len;
	unsigned nptrs	= 0;

retry:
	if (src >= end)
		goto invalid;

	switch (0x03 & (data[src] >> 6)) {
	case 0x00:
		len	= (0x3f & (data[src++]));

		if (end - src < len)
			goto invalid;

		if (lim > 0) {
			memcpy(dst, &data[src], MIN(lim, len));

			dst[MIN(lim - 1, len)]	= '\0';
		}

		*nxt	= src + len;

		return len;
	case 0x01:
		goto invalid;
	case 0x02:
		goto invalid;
	case 0x03:
		if (++nptrs > DNS_D_MAXPTRS)
			goto invalid;

		if (end - src < 2)
			goto invalid;

		src	= ((0x3f & data[src + 0]) << 8)
			| ((0xff & data[src + 1]) << 0);

		goto retry;
	} /* switch() */

	/* NOT REACHED */
invalid:
	*nxt	= end;

	return 0;
} /* dns_l_expand() */


static unsigned short dns_l_skip(unsigned short src, const unsigned char *data, size_t end) {
	unsigned short len;

	if (src >= end)
		goto invalid;

	switch (0x03 & (data[src] >> 6)) {
	case 0x00:
		len	= (0x3f & (data[src++]));

		if (end - src < len)
			goto invalid;

		return (len)? src + len : end;
	case 0x01:
		goto invalid;
	case 0x02:
		goto invalid;
	case 0x03:
		return end;
	} /* switch() */

	/* NOT REACHED */
invalid:
	return end;
} /* dns_l_skip() */


size_t dns_d_trim(void *dst_, size_t lim, const void *src_, size_t len, int flags) {
	unsigned char *dst = dst_;
	const unsigned char *src = src_;
	size_t dp = 0, sp = 0;
	int lc;

	/* trim any leading dot(s) */
	while (sp < len && src[sp] == '.')
		sp++;

	for (lc = 0; sp < len; lc = src[sp++]) {
		/* trim extra dot(s) */
		if (src[sp] == '.' && lc == '.')
			continue;

		if (dp < lim)
			dst[dp] = src[sp];

		dp++;
	}

	if ((flags & DNS_D_ANCHOR) && lc != '.') {
		if (dp < lim)
			dst[dp] = '.';

		dp++;
	}

	if (lim > 0)
		dst[MIN(dp, lim - 1)] = '\0';

	return dp;
} /* dns_d_trim() */


char *dns_d_init(void *dst, size_t lim, const void *src, size_t len, int flags) {
	if (flags & DNS_D_TRIM) {
		dns_d_trim(dst, lim, src, len, flags);
	} if (flags & DNS_D_ANCHOR) {
		dns_d_anchor(dst, lim, src, len);
	} else {
		memmove(dst, src, MIN(lim, len));

		if (lim > 0)
			((char *)dst)[MIN(len, lim - 1)]	= '\0';
	}

	return dst;
} /* dns_d_init() */


size_t dns_d_anchor(void *dst, size_t lim, const void *src, size_t len) {
	if (len == 0)
		return 0;

	memmove(dst, src, MIN(lim, len));

	if (((const char *)src)[len - 1] != '.') {
		if (len < lim)
			((char *)dst)[len]	= '.';
		len++;
	}

	if (lim > 0)
		((char *)dst)[MIN(lim - 1, len)]	= '\0';

	return len;
} /* dns_d_anchor() */


size_t dns_d_cleave(void *dst, size_t lim, const void *src, size_t len) {
	const char *dot;

	/* XXX: Skip any leading dot. Handles cleaving root ".". */
	if (len == 0 || !(dot = memchr((const char *)src + 1, '.', len - 1)))
		return 0;

	len	-= dot - (const char *)src;

	/* XXX: Unless root, skip the label's trailing dot. */
	if (len > 1) {
		src	= ++dot;
		len--;
	} else
		src	= dot;

	memmove(dst, src, MIN(lim, len));

	if (lim > 0)
		((char *)dst)[MIN(lim - 1, len)]	= '\0';

	return len;
} /* dns_d_cleave() */


size_t dns_d_comp(void *dst_, size_t lim, const void *src_, size_t len, struct dns_packet *P, int *error DNS_NOTUSED) {
	struct { unsigned char *b; size_t p, x; } dst, src;
	unsigned char ch	= '.';

	dst.b	= dst_;
	dst.p	= 0;
	dst.x	= 1;

	src.b	= (unsigned char *)src_;
	src.p	= 0;
	src.x	= 0;

	while (src.x < len) {
		ch	= src.b[src.x];

		if (ch == '.') {
			if (dst.p < lim)
				dst.b[dst.p]	= (0x3f & (src.x - src.p));

			dst.p	= dst.x++;
			src.p	= ++src.x;
		} else {
			if (dst.x < lim)
				dst.b[dst.x]	= ch;

			dst.x++;
			src.x++;
		}
	} /* while() */

	if (src.x > src.p) {
		if (dst.p < lim)
			dst.b[dst.p]	= (0x3f & (src.x - src.p));

		dst.p	= dst.x;
	}

	if (dst.p > 1) {
		if (dst.p < lim)
			dst.b[dst.p]	= 0x00;

		dst.p++;
	}

#if 1
	if (dst.p < lim) {
		struct { unsigned char label[DNS_D_MAXLABEL + 1]; size_t len; unsigned short p, x, y; } a, b;
		unsigned i;

		a.p	= 0;

		while ((a.len = dns_l_expand(a.label, sizeof a.label, a.p, &a.x, dst.b, lim))) {
			for (i = 0; i < lengthof(P->dict) && P->dict[i]; i++) {
				b.p	= P->dict[i];

				while ((b.len = dns_l_expand(b.label, sizeof b.label, b.p, &b.x, P->data, P->end))) {
					a.y	= a.x;
					b.y	= b.x;

					while (a.len && b.len && 0 == strcasecmp((char *)a.label, (char *)b.label)) {
						a.len = dns_l_expand(a.label, sizeof a.label, a.y, &a.y, dst.b, lim);
						b.len = dns_l_expand(b.label, sizeof b.label, b.y, &b.y, P->data, P->end);
					}

					if (a.len == 0 && b.len == 0 && b.p <= 0x3fff) {
						dst.b[a.p++]	= 0xc0
								| (0x3f & (b.p >> 8));
						dst.b[a.p++]	= (0xff & (b.p >> 0));

						return a.p;
					}

					b.p	= b.x;
				} /* while() */
			} /* for() */

			a.p	= a.x;
		} /* while() */
	} /* if () */
#endif

	return dst.p;
} /* dns_d_comp() */


unsigned short dns_d_skip(unsigned short src, struct dns_packet *P) {
	unsigned short len;

	while (src < P->end) {
		switch (0x03 & (P->data[src] >> 6)) {
		case 0x00:	/* FOLLOWS */
			len	= (0x3f & P->data[src++]);

			if (0 == len) {
/* success ==> */		return src;
			} else if (P->end - src > len) {
				src	+= len;

				break;
			} else
				goto invalid;

			/* NOT REACHED */
		case 0x01:	/* RESERVED */
			goto invalid;
		case 0x02:	/* RESERVED */
			goto invalid;
		case 0x03:	/* POINTER */
			if (P->end - src < 2)
				goto invalid;

			src	+= 2;

/* success ==> */	return src;
		} /* switch() */
	} /* while() */

invalid:
//assert(0);
	return P->end;
} /* dns_d_skip() */


#include <stdio.h>

size_t dns_d_expand(void *dst, size_t lim, unsigned short src, struct dns_packet *P, int *error) {
	size_t dstp	= 0;
	unsigned nptrs	= 0;
	unsigned char len;

	while (src < P->end) {
		switch ((0x03 & (P->data[src] >> 6))) {
		case 0x00:	/* FOLLOWS */
			len	= (0x3f & P->data[src]);

			if (0 == len) {
				if (dstp == 0) {
					if (dstp < lim)
						((unsigned char *)dst)[dstp]	= '.';

					dstp++;
				}

				/* NUL terminate */
				if (lim > 0)
					((unsigned char *)dst)[MIN(dstp, lim - 1)]	= '\0';

/* success ==> */		return dstp;
			}

			src++;

			if (P->end - src < len)
				goto toolong;

			if (dstp < lim)
				memcpy(&((unsigned char *)dst)[dstp], &P->data[src], MIN(len, lim - dstp));

			src	+= len;
			dstp	+= len;

			if (dstp < lim)
				((unsigned char *)dst)[dstp]	= '.';

			dstp++;

			nptrs	= 0;

			continue;
		case 0x01:	/* RESERVED */
			goto reserved;
		case 0x02:	/* RESERVED */
			goto reserved;
		case 0x03:	/* POINTER */
			if (++nptrs > DNS_D_MAXPTRS)
				goto toolong;

			if (P->end - src < 2)
				goto toolong;

			src	= ((0x3f & P->data[src + 0]) << 8)
				| ((0xff & P->data[src + 1]) << 0);

			continue;
		} /* switch() */
	} /* while() */

toolong:
	*error	= DNS_EILLEGAL;

	if (lim > 0)
		((unsigned char *)dst)[MIN(dstp, lim - 1)]	= '\0';

	return 0;
reserved:
	*error	= DNS_EILLEGAL;

	if (lim > 0)
		((unsigned char *)dst)[MIN(dstp, lim - 1)]	= '\0';

	return 0;
} /* dns_d_expand() */


int dns_d_push(struct dns_packet *P, const void *dn, size_t len) {
	size_t lim	= P->size - P->end;
	unsigned dp	= P->end;
	int error;

	len	= dns_d_comp(&P->data[dp], lim, dn, len, P, &error);

	if (len == 0)
		return error;
	if (len > lim)
		return DNS_ENOBUFS;

	P->end	+= len;

	dns_p_dictadd(P, dp);

	return 0;
} /* dns_d_push() */


size_t dns_d_cname(void *dst, size_t lim, const void *dn, size_t len, struct dns_packet *P, int *error_) {
	char host[DNS_D_MAXNAME + 1];
	struct dns_rr_i i;
	struct dns_rr rr;
	unsigned depth;
	int error;

	if (sizeof host <= dns_d_anchor(host, sizeof host, dn, len))
		{ error = ENAMETOOLONG; goto error; }

	for (depth = 0; depth < 7; depth++) {
		dns_rr_i_init(memset(&i, 0, sizeof i), P);

		i.section	= DNS_S_ALL & ~DNS_S_QD;
		i.name		= host;
		i.type		= DNS_T_CNAME;

		if (!dns_rr_grep(&rr, 1, &i, P, &error))
			break;

		if ((error = dns_cname_parse((struct dns_cname *)host, &rr, P)))
			goto error;
	}

	return dns_strlcpy(dst, host, lim);
error:
	*error_	= error;

	return 0;
} /* dns_d_cname() */


/*
 * R E S O U R C E  R E C O R D  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

int dns_rr_copy(struct dns_packet *P, struct dns_rr *rr, struct dns_packet *Q) {
	unsigned char dn[DNS_D_MAXNAME + 1];
	union dns_any any;
	size_t len;
	int error;

	if (!(len = dns_d_expand(dn, sizeof dn, rr->dn.p, Q, &error)))
		return error;
	else if (len >= sizeof dn)
		return DNS_EILLEGAL;

	if (rr->section != DNS_S_QD && (error = dns_any_parse(dns_any_init(&any, sizeof any), rr, Q)))
		return error;

	return dns_p_push(P, rr->section, dn, len, rr->type, rr->class, rr->ttl, &any);
} /* dns_rr_copy() */


int dns_rr_parse(struct dns_rr *rr, unsigned short src, struct dns_packet *P) {
	unsigned short p	= src;

	if (src >= P->end)
		goto invalid;

	rr->dn.p	= p;
	rr->dn.len	= (p = dns_d_skip(p, P)) - rr->dn.p;

	if (P->end - p < 4)
		goto invalid;

	rr->type	= ((0xff & P->data[p + 0]) << 8)
			| ((0xff & P->data[p + 1]) << 0);

	rr->class	= ((0xff & P->data[p + 2]) << 8)
			| ((0xff & P->data[p + 3]) << 0);

	p	+= 4;

	if (src < dns_p_qend(P)) {
		rr->section	= DNS_S_QUESTION;

		rr->ttl		= 0;
		rr->rd.p	= 0;
		rr->rd.len	= 0;

		return 0;
	}

	if (P->end - p < 4)
		goto invalid;

	rr->ttl		= ((0x7f & P->data[p + 0]) << 24)
			| ((0xff & P->data[p + 1]) << 16)
			| ((0xff & P->data[p + 2]) << 8)
			| ((0xff & P->data[p + 3]) << 0);

	p	+= 4;

	if (P->end - p < 2)
		goto invalid;

	rr->rd.len	= ((0xff & P->data[p + 0]) << 8)
			| ((0xff & P->data[p + 1]) << 0);
	rr->rd.p	= p + 2;

	p	+= 2;

	if (P->end - p < rr->rd.len)
		goto invalid;

	return 0;
invalid:
//assert(0);
	return DNS_EILLEGAL;
} /* dns_rr_parse() */


static unsigned short dns_rr_len(const unsigned short src, struct dns_packet *P) {
	unsigned short rp, rdlen;

	rp	= dns_d_skip(src, P);

	if (P->end - rp < 4)
		return P->end - src;

	rp	+= 4;	/* TYPE, CLASS */

	if (rp <= dns_p_qend(P))
		return rp - src;

	if (P->end - rp < 6)
		return P->end - src;

	rp	+= 6;	/* TTL, RDLEN */

	rdlen	= ((0xff & P->data[rp - 2]) << 8)
		| ((0xff & P->data[rp - 1]) << 0);

	if (P->end - rp < rdlen)
		return P->end - src;

	rp	+= rdlen;

	return rp - src;
} /* dns_rr_len() */


unsigned short dns_rr_skip(unsigned short src, struct dns_packet *P) {
	return src + dns_rr_len(src, P);
} /* dns_rr_skip() */


static enum dns_section dns_rr_section(unsigned short src, struct dns_packet *P) {
	enum dns_section section;
	unsigned count, ind;
	unsigned short rp;

	if (src >= P->qd.base && src < P->qd.end)
		return DNS_S_QD;
	if (src >= P->an.base && src < P->an.end)
		return DNS_S_AN;
	if (src >= P->ns.base && src < P->ns.end)
		return DNS_S_NS;
	if (src >= P->ar.base && src < P->ar.end)
		return DNS_S_AR;

	/* NOTE: Possibly bad memoization. Try it the hard-way. */

	for (rp = 12, ind = 0; rp < src && rp < P->end; ind++)
		rp = dns_rr_skip(rp, P);

	section = DNS_S_QD;
	count   = dns_p_count(P, section);

	while (ind >= count && section <= DNS_S_AR) {
		section <<= 1;
		count += dns_p_count(P, section);
	}

	return DNS_S_ALL & section;
} /* dns_rr_section() */


static enum dns_type dns_rr_type(unsigned short src, struct dns_packet *P) {
	struct dns_rr rr;
	int error;

	if ((error = dns_rr_parse(&rr, src, P)))
		return 0;

	return rr.type;
} /* dns_rr_type() */


int dns_rr_cmp(struct dns_rr *r0, struct dns_packet *P0, struct dns_rr *r1, struct dns_packet *P1) {
	char host0[DNS_D_MAXNAME + 1], host1[DNS_D_MAXNAME + 1];
	union dns_any any0, any1;
	int cmp, error;
	size_t len;

	if ((cmp = r0->type - r1->type))
		return cmp;

	if ((cmp = r0->class - r1->class))
		return cmp;

	/*
	 * FIXME: Do label-by-label comparison to handle illegally long names?
	 */

	if (!(len = dns_d_expand(host0, sizeof host0, r0->dn.p, P0, &error))
	||  len >= sizeof host0)
		return -1;

	if (!(len = dns_d_expand(host1, sizeof host1, r1->dn.p, P1, &error))
	||  len >= sizeof host1)
		return 1;

	if ((cmp = strcasecmp(host0, host1)))
		return cmp;

	if (DNS_S_QD & (r0->section | r1->section)) {
		if (r0->section == r1->section)
			return 0;

		return (r0->section == DNS_S_QD)? -1 : 1;
	}

	if ((error = dns_any_parse(&any0, r0, P0)))
		return -1;

	if ((error = dns_any_parse(&any1, r1, P1)))
		return 1;

	return dns_any_cmp(&any0, r0->type, &any1, r1->type);
} /* dns_rr_cmp() */


static _Bool dns_rr_exists(struct dns_rr *rr0, struct dns_packet *P0, struct dns_packet *P1) {
	struct dns_rr rr1;

	dns_rr_foreach(&rr1, P1, .section = rr0->section, .type = rr0->type) {
		if (0 == dns_rr_cmp(rr0, P0, &rr1, P1))
			return 1;
	}

	return 0;
} /* dns_rr_exists() */


static unsigned short dns_rr_offset(struct dns_rr *rr) {
	return rr->dn.p;
} /* dns_rr_offset() */


static _Bool dns_rr_i_match(struct dns_rr *rr, struct dns_rr_i *i, struct dns_packet *P) {
	if (i->section && !(rr->section & i->section))
		return 0;

	if (i->type && rr->type != i->type && i->type != DNS_T_ALL)
		return 0;

	if (i->class && rr->class != i->class && i->class != DNS_C_ANY)
		return 0;

	if (i->name) {
		char dn[DNS_D_MAXNAME + 1];
		size_t len;
		int error;

		if (!(len = dns_d_expand(dn, sizeof dn, rr->dn.p, P, &error))
		||  len >= sizeof dn)
			return 0;

		if (0 != strcasecmp(dn, i->name))
			return 0;
	}

	if (i->data && i->type && rr->section > DNS_S_QD) {
		union dns_any rd;
		int error;

		if ((error = dns_any_parse(&rd, rr, P)))
			return 0;

		if (0 != dns_any_cmp(&rd, rr->type, i->data, i->type))
			return 0;
	}

	return 1;
} /* dns_rr_i_match() */


static unsigned short dns_rr_i_start(struct dns_rr_i *i, struct dns_packet *P) {
	unsigned short rp;
	struct dns_rr r0, rr;
	int error;

	if ((i->section & DNS_S_QD) && P->qd.base)
		rp = P->qd.base;
	else if ((i->section & DNS_S_AN) && P->an.base)
		rp = P->an.base;
	else if ((i->section & DNS_S_NS) && P->ns.base)
		rp = P->ns.base;
	else if ((i->section & DNS_S_AR) && P->ar.base)
		rp = P->ar.base;
	else
		rp = 12;

	for (; rp < P->end; rp = dns_rr_skip(rp, P)) {
		if ((error = dns_rr_parse(&rr, rp, P)))
			continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P))
			continue;

		r0 = rr;

		goto lower;
	}

	return P->end;
lower:
	if (i->sort == &dns_rr_i_packet)
		return dns_rr_offset(&r0);

	while ((rp = dns_rr_skip(rp, P)) < P->end) {
		if ((error = dns_rr_parse(&rr, rp, P)))
			continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P))
			continue;

		if (i->sort(&rr, &r0, i, P) < 0)
			r0 = rr;
	}

	return dns_rr_offset(&r0);
} /* dns_rr_i_start() */


static unsigned short dns_rr_i_skip(unsigned short rp, struct dns_rr_i *i, struct dns_packet *P) {
	struct dns_rr r0, r1, rr;
	int error;

	if ((error = dns_rr_parse(&r0, rp, P)))
		return P->end;

	r0.section = dns_rr_section(rp, P);

	rp = (i->sort == &dns_rr_i_packet)? dns_rr_skip(rp, P) : 12;

	for (; rp < P->end; rp = dns_rr_skip(rp, P)) {
		if ((error = dns_rr_parse(&rr, rp, P)))
			continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P))
			continue;

		if (i->sort(&rr, &r0, i, P) <= 0)
			continue;

		r1 = rr;

		goto lower;
	}

	return P->end;
lower:
	if (i->sort == &dns_rr_i_packet)
		return dns_rr_offset(&r1);

	while ((rp = dns_rr_skip(rp, P)) < P->end) {
		if ((error = dns_rr_parse(&rr, rp, P)))
			continue;

		rr.section = dns_rr_section(rp, P);

		if (!dns_rr_i_match(&rr, i, P))
			continue;

		if (i->sort(&rr, &r0, i, P) <= 0)
			continue;

		if (i->sort(&rr, &r1, i, P) >= 0)
			continue;

		r1 = rr;
	}

	return dns_rr_offset(&r1);
} /* dns_rr_i_skip() */


int dns_rr_i_packet(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i DNS_NOTUSED, struct dns_packet *P DNS_NOTUSED) {
	return (int)a->dn.p - (int)b->dn.p;
} /* dns_rr_i_packet() */


int dns_rr_i_order(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i DNS_NOTUSED, struct dns_packet *P) {
	int cmp;

	if ((cmp = a->section - b->section))
		return cmp;

	if (a->type != b->type)
		return (int)a->dn.p - (int)b->dn.p;

	return dns_rr_cmp(a, P, b, P);
} /* dns_rr_i_order() */


int dns_rr_i_shuffle(struct dns_rr *a, struct dns_rr *b, struct dns_rr_i *i, struct dns_packet *P DNS_NOTUSED) {
	int cmp;

	while (!i->state.regs[0])
		i->state.regs[0]	= dns_random();

	if ((cmp = a->section - b->section))
		return cmp;

	return dns_k_shuffle16(a->dn.p, i->state.regs[0]) - dns_k_shuffle16(b->dn.p, i->state.regs[0]);
} /* dns_rr_i_shuffle() */


struct dns_rr_i *dns_rr_i_init(struct dns_rr_i *i, struct dns_packet *P DNS_NOTUSED) {
	static const struct dns_rr_i i_initializer;

	i->state	= i_initializer.state;
	i->saved	= i->state;

	return i;
} /* dns_rr_i_init() */


unsigned dns_rr_grep(struct dns_rr *rr, unsigned lim, struct dns_rr_i *i, struct dns_packet *P, int *error_) {
	unsigned count	= 0;
	int error;

	switch (i->state.exec) {
	case 0:
		if (!i->sort)
			i->sort	= &dns_rr_i_packet;

		i->state.next	= dns_rr_i_start(i, P);
		i->state.exec++;

		/* FALL THROUGH */
	case 1:
		while (count < lim && i->state.next < P->end) {
			if ((error = dns_rr_parse(rr, i->state.next, P)))
				goto error;

			rr->section	= dns_rr_section(i->state.next, P);

			rr++;
			count++;
			i->state.count++;

			i->state.next	= dns_rr_i_skip(i->state.next, i, P);
		} /* while() */

		break;
	} /* switch() */

	return count;
error:
	*error_	= error;

	return count;
} /* dns_rr_grep() */


static size_t dns__printchar(void *dst, size_t lim, size_t cp, unsigned char ch) {
	if (cp < lim)
		((unsigned char *)dst)[cp]	= ch;

	return 1;
} /* dns__printchar() */


static size_t dns__printstring(void *dst, size_t lim, size_t cp, const void *src, size_t len) {
	if (cp < lim)
		memcpy(&((unsigned char *)dst)[cp], src, MIN(len, lim - cp));

	return len;
} /* dns__printstring() */

#define dns__printstring5(a, b, c, d, e)	dns__printstring((a), (b), (c), (d), (e))
#define dns__printstring4(a, b, c, d)		dns__printstring((a), (b), (c), (d), strlen((d)))
#define dns__printstring(...)			DNS_PP_CALL(DNS_PP_XPASTE(dns__printstring, DNS_PP_NARG(__VA_ARGS__)), __VA_ARGS__)


static void dns__printnul(void *dst, size_t lim, size_t off) {
	if (lim > 0)
		((unsigned char *)dst)[MIN(off, lim - 1)]	= '\0';
} /* dns__printnul() */


static size_t dns__print10(void *dst, size_t lim, size_t off, unsigned n, unsigned pad) {
	unsigned char tmp[32];
	unsigned dp	= off;
	unsigned cp	= 0;
	unsigned d	= 1000000000;
	unsigned ch;

	pad	= MAX(1, pad);
	
	while (d) {
		if ((ch = n / d) || cp > 0) {
			n	-= ch * d;

			tmp[cp]	= '0' + ch;

			cp++;
		}

		d	/= 10;
	}

	while (cp < pad) {
		dp	+= dns__printchar(dst, lim, dp, '0');
		pad--;
	}

	dp	+= dns__printstring(dst, lim, dp, tmp, cp);

	return dp - off;
} /* dns__print10() */


size_t dns_rr_print(void *dst, size_t lim, struct dns_rr *rr, struct dns_packet *P, int *error_) {
	union dns_any any;
	size_t cp, n, rdlen;
	void *rd;
	int error;

	cp	= 0;

	if (rr->section == DNS_S_QD)
		cp	+= dns__printchar(dst, lim, cp, ';');

	if (!(n = dns_d_expand(&((unsigned char *)dst)[cp], (cp < lim)? lim - cp : 0, rr->dn.p, P, &error)))
		goto error;

	cp	+= n;

	if (rr->section != DNS_S_QD) {
		cp	+= dns__printchar(dst, lim, cp, ' ');
		cp	+= dns__print10(dst, lim, cp, rr->ttl, 0);
	}

	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__printstring(dst, lim, cp, dns_strclass(rr->class), strlen(dns_strclass(rr->class)));
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__printstring(dst, lim, cp, dns_strtype(rr->type), strlen(dns_strtype(rr->type)));

	if (rr->section == DNS_S_QD)
		goto epilog;

	cp	+= dns__printchar(dst, lim, cp, ' ');

	if ((error = dns_any_parse(dns_any_init(&any, sizeof any), rr, P)))
		goto error;

	if (cp < lim) {
		rd	= &((unsigned char *)dst)[cp];
		rdlen	= lim - cp;
	} else {
		rd	= 0;
		rdlen	= 0;
	}

	cp	+= dns_any_print(rd, rdlen, &any, rr->type);

epilog:
	dns__printnul(dst, lim, cp);

	return cp;
error:
	*error_	= error;

	return 0;
} /* dns_rr_print() */


int dns_a_parse(struct dns_a *a, struct dns_rr *rr, struct dns_packet *P) {
	unsigned long addr;

	if (rr->rd.len != 4)
		return DNS_EILLEGAL;

	addr	= ((0xff & P->data[rr->rd.p + 0]) << 24)
		| ((0xff & P->data[rr->rd.p + 1]) << 16)
		| ((0xff & P->data[rr->rd.p + 2]) << 8)
		| ((0xff & P->data[rr->rd.p + 3]) << 0);

	a->addr.s_addr	= htonl(addr);

	return 0;
} /* dns_a_parse() */


int dns_a_push(struct dns_packet *P, struct dns_a *a) {
	unsigned long addr;

	if (P->size - P->end < 6)
		return DNS_ENOBUFS;

	P->data[P->end++]	= 0x00;
	P->data[P->end++]	= 0x04;

	addr	= ntohl(a->addr.s_addr);

	P->data[P->end++]	= 0xff & (addr >> 24);
	P->data[P->end++]	= 0xff & (addr >> 16);
	P->data[P->end++]	= 0xff & (addr >> 8);
	P->data[P->end++]	= 0xff & (addr >> 0);

	return 0;
} /* dns_a_push() */


size_t dns_a_arpa(void *dst, size_t lim, const struct dns_a *a) {
	unsigned long a4	= ntohl(a->addr.s_addr);
	size_t cp		= 0;
	unsigned i;

	for (i = 4; i > 0; i--) {
		cp	+= dns__print10(dst, lim, cp, (0xff & a4), 0);
		cp	+= dns__printchar(dst, lim, cp, '.');
		a4	>>= 8;
	}

	cp	+= dns__printstring(dst, lim, cp, "in-addr.arpa.");

	dns__printnul(dst, lim, cp);

	return cp;
} /* dns_a_arpa() */


int dns_a_cmp(const struct dns_a *a, const struct dns_a *b) {
	if (ntohl(a->addr.s_addr) < ntohl(b->addr.s_addr))
		return -1;
	if (ntohl(a->addr.s_addr) > ntohl(b->addr.s_addr))
		return 1;

	return 0;
} /* dns_a_cmp() */


size_t dns_a_print(void *dst, size_t lim, struct dns_a *a) {
	char addr[INET_ADDRSTRLEN + 1]	= "0.0.0.0";
	size_t len;

	dns_inet_ntop(AF_INET, &a->addr, addr, sizeof addr);

	dns__printnul(dst, lim, (len = dns__printstring(dst, lim, 0, addr)));

	return len;
} /* dns_a_print() */


int dns_aaaa_parse(struct dns_aaaa *aaaa, struct dns_rr *rr, struct dns_packet *P) {
	if (rr->rd.len != sizeof aaaa->addr.s6_addr)
		return DNS_EILLEGAL;

	memcpy(aaaa->addr.s6_addr, &P->data[rr->rd.p], sizeof aaaa->addr.s6_addr);

	return 0;
} /* dns_aaaa_parse() */


int dns_aaaa_push(struct dns_packet *P, struct dns_aaaa *aaaa) {
	if (P->size - P->end < 2 + sizeof aaaa->addr.s6_addr)
		return DNS_ENOBUFS;

	P->data[P->end++]	= 0x00;
	P->data[P->end++]	= 0x10;

	memcpy(&P->data[P->end], aaaa->addr.s6_addr, sizeof aaaa->addr.s6_addr);

	P->end	+= sizeof aaaa->addr.s6_addr;

	return 0;
} /* dns_aaaa_push() */


int dns_aaaa_cmp(const struct dns_aaaa *a, const struct dns_aaaa *b) {
	unsigned i;
	int cmp;

	for (i = 0; i < lengthof(a->addr.s6_addr); i++) {
		if ((cmp = (a->addr.s6_addr[i] - b->addr.s6_addr[i])))
			return cmp;
	}

	return 0;
} /* dns_aaaa_cmp() */


size_t dns_aaaa_arpa(void *dst, size_t lim, const struct dns_aaaa *aaaa) {
	static const unsigned char hex[16]	= "0123456789abcdef";
	size_t cp		= 0;
	unsigned nyble;
	int i, j;

	for (i = sizeof aaaa->addr.s6_addr - 1; i >= 0; i--) {
		nyble	= aaaa->addr.s6_addr[i];

		for (j = 0; j < 2; j++) {
			cp	+= dns__printchar(dst, lim, cp, hex[0x0f & nyble]);
			cp	+= dns__printchar(dst, lim, cp, '.');
			nyble	>>= 4;
		}
	}

	cp	+= dns__printstring(dst, lim, cp, "ip6.arpa.");

	dns__printnul(dst, lim, cp);

	return cp;
} /* dns_aaaa_arpa() */


size_t dns_aaaa_print(void *dst, size_t lim, struct dns_aaaa *aaaa) {
	char addr[INET6_ADDRSTRLEN + 1]	= "::";
	size_t len;

	dns_inet_ntop(AF_INET6, &aaaa->addr, addr, sizeof addr);

	dns__printnul(dst, lim, (len = dns__printstring(dst, lim, 0, addr)));

	return len;
} /* dns_aaaa_print() */


int dns_mx_parse(struct dns_mx *mx, struct dns_rr *rr, struct dns_packet *P) {
	size_t len;
	int error;

	if (rr->rd.len < 3)
		return DNS_EILLEGAL;

	mx->preference	= (0xff00 & (P->data[rr->rd.p + 0] << 8))
			| (0x00ff & (P->data[rr->rd.p + 1] << 0));

	if (!(len = dns_d_expand(mx->host, sizeof mx->host, rr->rd.p + 2, P, &error)))
		return error;
	else if (len >= sizeof mx->host)
		return DNS_EILLEGAL;

	return 0;
} /* dns_mx_parse() */


int dns_mx_push(struct dns_packet *P, struct dns_mx *mx) {
	size_t end, len;
	int error;

	if (P->size - P->end < 5)
		return DNS_ENOBUFS;

	end	= P->end;
	P->end	+= 2;

	P->data[P->end++]	= 0xff & (mx->preference >> 8);
	P->data[P->end++]	= 0xff & (mx->preference >> 0);

	if ((error = dns_d_push(P, mx->host, strlen(mx->host))))
		goto error;

	len	= P->end - end - 2;

	P->data[end + 0]	= 0xff & (len >> 8);
	P->data[end + 1]	= 0xff & (len >> 0);

	return 0;
error:
	P->end	= end;

	return error;
} /* dns_mx_push() */


int dns_mx_cmp(const struct dns_mx *a, const struct dns_mx *b) {
	int cmp;

	if ((cmp = a->preference - b->preference))
		return cmp;

	return strcasecmp(a->host, b->host);
} /* dns_mx_cmp() */


size_t dns_mx_print(void *dst, size_t lim, struct dns_mx *mx) {
	size_t cp	= 0;

	cp	+= dns__print10(dst, lim, cp, mx->preference, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__printstring(dst, lim, cp, mx->host, strlen(mx->host));

	dns__printnul(dst, lim, cp);

	return cp;
} /* dns_mx_print() */


size_t dns_mx_cname(void *dst, size_t lim, struct dns_mx *mx) {
	return dns_strlcpy(dst, mx->host, lim);
} /* dns_mx_cname() */


int dns_ns_parse(struct dns_ns *ns, struct dns_rr *rr, struct dns_packet *P) {
	size_t len;
	int error;

	if (!(len = dns_d_expand(ns->host, sizeof ns->host, rr->rd.p, P, &error)))
		return error;
	else if (len >= sizeof ns->host)
		return DNS_EILLEGAL;

	return 0;
} /* dns_ns_parse() */


int dns_ns_push(struct dns_packet *P, struct dns_ns *ns) {
	size_t end, len;
	int error;

	if (P->size - P->end < 3)
		return DNS_ENOBUFS;

	end	= P->end;
	P->end	+= 2;

	if ((error = dns_d_push(P, ns->host, strlen(ns->host))))
		goto error;

	len	= P->end - end - 2;

	P->data[end + 0]	= 0xff & (len >> 8);
	P->data[end + 1]	= 0xff & (len >> 0);

	return 0;
error:
	P->end	= end;

	return error;
} /* dns_ns_push() */


int dns_ns_cmp(const struct dns_ns *a, const struct dns_ns *b) {
	return strcasecmp(a->host, b->host);
} /* dns_ns_cmp() */


size_t dns_ns_print(void *dst, size_t lim, struct dns_ns *ns) {
	size_t cp;

	cp	= dns__printstring(dst, lim, 0, ns->host, strlen(ns->host));

	dns__printnul(dst, lim, cp);

	return cp;
} /* dns_ns_print() */


size_t dns_ns_cname(void *dst, size_t lim, struct dns_ns *ns) {
	return dns_strlcpy(dst, ns->host, lim);
} /* dns_ns_cname() */


int dns_cname_parse(struct dns_cname *cname, struct dns_rr *rr, struct dns_packet *P) {
	return dns_ns_parse((struct dns_ns *)cname, rr, P);
} /* dns_cname_parse() */


int dns_cname_push(struct dns_packet *P, struct dns_cname *cname) {
	return dns_ns_push(P, (struct dns_ns *)cname);
} /* dns_cname_push() */


int dns_cname_cmp(const struct dns_cname *a, const struct dns_cname *b) {
	return strcasecmp(a->host, b->host);
} /* dns_cname_cmp() */


size_t dns_cname_print(void *dst, size_t lim, struct dns_cname *cname) {
	return dns_ns_print(dst, lim, (struct dns_ns *)cname);
} /* dns_cname_print() */


size_t dns_cname_cname(void *dst, size_t lim, struct dns_cname *cname) {
	return dns_strlcpy(dst, cname->host, lim);
} /* dns_cname_cname() */


int dns_soa_parse(struct dns_soa *soa, struct dns_rr *rr, struct dns_packet *P) {
	struct { void *dst; size_t lim; } dn[] =
		{ { soa->mname, sizeof soa->mname },
		  { soa->rname, sizeof soa->rname } };
	unsigned *ts[] =
		{ &soa->serial, &soa->refresh, &soa->retry, &soa->expire, &soa->minimum };
	unsigned short rp;
	unsigned i, j, n;
	int error;

	/* MNAME / RNAME */
	if ((rp = rr->rd.p) >= P->end)
		return DNS_EILLEGAL;

	for (i = 0; i < lengthof(dn); i++) {
		if (!(n = dns_d_expand(dn[i].dst, dn[i].lim, rp, P, &error)))
			return error;
		else if (n >= dn[i].lim)
			return DNS_EILLEGAL;

		if ((rp = dns_d_skip(rp, P)) >= P->end)
			return DNS_EILLEGAL;
	}

	/* SERIAL / REFRESH / RETRY / EXPIRE / MINIMUM */
	for (i = 0; i < lengthof(ts); i++) {
		for (j = 0; j < 4; j++, rp++) {
			if (rp >= P->end)
				return DNS_EILLEGAL;

			*ts[i]	<<= 8;
			*ts[i]	|= (0xff & P->data[rp]);
		}
	}

	return 0;
} /* dns_soa_parse() */


int dns_soa_push(struct dns_packet *P, struct dns_soa *soa) {
	void *dn[]	= { soa->mname, soa->rname };
	unsigned ts[]	= { (0xffffffff & soa->serial),
			    (0x7fffffff & soa->refresh),
			    (0x7fffffff & soa->retry),
			    (0x7fffffff & soa->expire),
			    (0xffffffff & soa->minimum) };
	unsigned i, j;
	size_t end, len;
	int error;

	end	= P->end;

	if ((P->end += 2) >= P->size)
		goto toolong;

	/* MNAME / RNAME */
	for (i = 0; i < lengthof(dn); i++) {
		if ((error = dns_d_push(P, dn[i], strlen(dn[i]))))
			goto error;
	}

	/* SERIAL / REFRESH / RETRY / EXPIRE / MINIMUM */
	for (i = 0; i < lengthof(ts); i++) {
		if ((P->end += 4) >= P->size)
			goto toolong;

		for (j = 1; j <= 4; j++) {
			P->data[P->end - j]	= (0xff & ts[i]);
			ts[i]			>>= 8;
		}
	}

	len			= P->end - end - 2;
	P->data[end + 0]	= (0xff & (len >> 8));
	P->data[end + 1]	= (0xff & (len >> 0));

	return 0;
toolong:
	error	= DNS_ENOBUFS;

	/* FALL THROUGH */
error:
	P->end	= end;

	return error;
} /* dns_soa_push() */


int dns_soa_cmp(const struct dns_soa *a, const struct dns_soa *b) {
	int cmp;
	
	if ((cmp = strcasecmp(a->mname, b->mname)))
		return cmp;

	if ((cmp = strcasecmp(a->rname, b->rname)))
		return cmp;

	if (a->serial > b->serial)
		return -1;
	else if (a->serial < b->serial)
		return 1;

	if (a->refresh > b->refresh)
		return -1;
	else if (a->refresh < b->refresh)
		return 1;

	if (a->retry > b->retry)
		return -1;
	else if (a->retry < b->retry)
		return 1;

	if (a->expire > b->expire)
		return -1;
	else if (a->expire < b->expire)
		return 1;

	if (a->minimum > b->minimum)
		return -1;
	else if (a->minimum < b->minimum)
		return 1;

	return 0;
} /* dns_soa_cmp() */


size_t dns_soa_print(void *dst, size_t lim, struct dns_soa *soa) {
	size_t cp	= 0;

	cp	+= dns__printstring(dst, lim, cp, soa->mname, strlen(soa->mname));
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__printstring(dst, lim, cp, soa->rname, strlen(soa->rname));
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, soa->serial, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, soa->refresh, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, soa->retry, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, soa->expire, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, soa->minimum, 0);

	dns__printnul(dst, lim, cp);

	return cp;
} /* dns_soa_print() */


int dns_srv_parse(struct dns_srv *srv, struct dns_rr *rr, struct dns_packet *P) {
	unsigned short rp;
	unsigned i;
	size_t n;
	int error;

	memset(srv, '\0', sizeof *srv);

	rp	= rr->rd.p;

	if (P->size - P->end < 6)
		return DNS_EILLEGAL;

	for (i = 0; i < 2; i++, rp++) {
		srv->priority	<<= 8;
		srv->priority	|= (0xff & P->data[rp]);
	}

	for (i = 0; i < 2; i++, rp++) {
		srv->weight	<<= 8;
		srv->weight	|= (0xff & P->data[rp]);
	}

	for (i = 0; i < 2; i++, rp++) {
		srv->port	<<= 8;
		srv->port	|= (0xff & P->data[rp]);
	}

	if (!(n = dns_d_expand(srv->target, sizeof srv->target, rp, P, &error)))
		return error;
	else if (n >= sizeof srv->target)
		return DNS_EILLEGAL;

	return 0;
} /* dns_srv_parse() */


int dns_srv_push(struct dns_packet *P, struct dns_srv *srv) {
	size_t end, len;
	int error;

	end	= P->end;

	if (P->size - P->end < 2)
		goto toolong;

	P->end	+= 2;

	if (P->size - P->end < 6)
		goto toolong;

	P->data[P->end++]	= 0xff & (srv->priority >> 8);
	P->data[P->end++]	= 0xff & (srv->priority >> 0);

	P->data[P->end++]	= 0xff & (srv->weight >> 8);
	P->data[P->end++]	= 0xff & (srv->weight >> 0);

	P->data[P->end++]	= 0xff & (srv->port >> 8);
	P->data[P->end++]	= 0xff & (srv->port >> 0);

	if (0 == (len = dns_d_comp(&P->data[P->end], P->size - P->end, srv->target, strlen(srv->target), P, &error)))
		goto error;
	else if (P->size - P->end < len)
		goto toolong;

	P->end	+= len;

	if (P->end > 65535)
		goto toolong;

	len	= P->end - end - 2;

	P->data[end + 0]	= 0xff & (len >> 8);
	P->data[end + 1]	= 0xff & (len >> 0);

	return 0;
toolong:
	error	= DNS_ENOBUFS;

	/* FALL THROUGH */
error:
	P->end	= end;

	return error;
} /* dns_srv_push() */


int dns_srv_cmp(const struct dns_srv *a, const struct dns_srv *b) {
	int cmp;
	
	if ((cmp = a->priority - b->priority))
		return cmp;

	/*
	 * FIXME: We need some sort of random seed to implement the dynamic
	 * weighting required by RFC 2782.
	 */
	if ((cmp = a->weight - b->weight))
		return cmp;

	if ((cmp = a->port - b->port))
		return cmp;

	return strcasecmp(a->target, b->target);
} /* dns_srv_cmp() */


size_t dns_srv_print(void *dst, size_t lim, struct dns_srv *srv) {
	size_t cp	= 0;

	cp	+= dns__print10(dst, lim, cp, srv->priority, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, srv->weight, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__print10(dst, lim, cp, srv->port, 0);
	cp	+= dns__printchar(dst, lim, cp, ' ');
	cp	+= dns__printstring(dst, lim, cp, srv->target, strlen(srv->target));

	dns__printnul(dst, lim, cp);

	return cp;
} /* dns_srv_print() */


size_t dns_srv_cname(void *dst, size_t lim, struct dns_srv *srv) {
	return dns_strlcpy(dst, srv->target, lim);
} /* dns_srv_cname() */


unsigned int dns_opt_ttl(const struct dns_opt *opt) {
	unsigned int ttl = 0;

	ttl |= (0xffU & opt->rcode) << 24U;
	ttl |= (0xffU & opt->version) << 16U;

	return ttl;
} /* dns_opt_ttl() */


unsigned short dns_opt_class(const struct dns_opt *opt) {
	return opt->maxsize;
} /* dns_opt_class() */


struct dns_opt *dns_opt_init(struct dns_opt *opt, size_t size) {
	assert(size >= offsetof(struct dns_opt, data));

	opt->size = size - offsetof(struct dns_opt, data);
	opt->len  = 0;

	opt->rcode   = 0;
	opt->version = 0;
	opt->maxsize = 512;

	return opt;
} /* dns_opt_init() */


int dns_opt_parse(struct dns_opt *opt, struct dns_rr *rr, struct dns_packet *P) {
	opt->len = 0;

	return 0;
} /* dns_opt_parse() */


int dns_opt_push(struct dns_packet *P, struct dns_opt *opt) {
	return 0;
} /* dns_opt_push() */


int dns_opt_cmp(const struct dns_opt *a, const struct dns_opt *b) {
	return 0;
} /* dns_opt_cmp() */


size_t dns_opt_print(void *dst, size_t lim, struct dns_opt *opt) {
	size_t p = 0, src;

	p += dns__printchar(dst, lim, p, '"');

	for (src = 0; src < opt->len; src++) {
		p += dns__printchar(dst, lim, p, '\\');
		p += dns__print10(dst, lim, p, opt->data[src], 3);
	}

	p += dns__printchar(dst, lim, p, '"');

	dns__printnul(dst, lim, p);

	return p;
} /* dns_opt_print() */


int dns_ptr_parse(struct dns_ptr *ptr, struct dns_rr *rr, struct dns_packet *P) {
	return dns_ns_parse((struct dns_ns *)ptr, rr, P);
} /* dns_ptr_parse() */


int dns_ptr_push(struct dns_packet *P, struct dns_ptr *ptr) {
	return dns_ns_push(P, (struct dns_ns *)ptr);
} /* dns_ptr_push() */


size_t dns_ptr_qname(void *dst, size_t lim, int af, void *addr) {
	unsigned len	= (af == AF_INET6)
			? dns_aaaa_arpa(dst, lim, addr)
			: dns_a_arpa(dst, lim, addr);

	dns__printnul(dst, lim, len);

	return len;
} /* dns_ptr_qname() */


int dns_ptr_cmp(const struct dns_ptr *a, const struct dns_ptr *b) {
	return strcasecmp(a->host, b->host);
} /* dns_ptr_cmp() */


size_t dns_ptr_print(void *dst, size_t lim, struct dns_ptr *ptr) {
	return dns_ns_print(dst, lim, (struct dns_ns *)ptr);
} /* dns_ptr_print() */


size_t dns_ptr_cname(void *dst, size_t lim, struct dns_ptr *ptr) {
	return dns_strlcpy(dst, ptr->host, lim);
} /* dns_ptr_cname() */


int dns_sshfp_parse(struct dns_sshfp *fp, struct dns_rr *rr, struct dns_packet *P) {
	unsigned p = rr->rd.p, pe = rr->rd.p + rr->rd.len;

	if (pe - p < 2)
		return DNS_EILLEGAL;

	fp->algo = P->data[p++];
	fp->type = P->data[p++];

	switch (fp->type) {
	case DNS_SSHFP_SHA1:
		if (pe - p < sizeof fp->digest.sha1)
			return DNS_EILLEGAL;

		memcpy(fp->digest.sha1, &P->data[p], sizeof fp->digest.sha1);

		break;
	default:
		break;
	} /* switch() */

	return 0;
} /* dns_sshfp_parse() */


int dns_sshfp_push(struct dns_packet *P, struct dns_sshfp *fp) {
	unsigned p = P->end, pe = P->size, n;

	if (pe - p < 4)
		return DNS_ENOBUFS;

	p += 2;
	P->data[p++] = 0xff & fp->algo;
	P->data[p++] = 0xff & fp->type;

	switch (fp->type) {
	case DNS_SSHFP_SHA1:
		if (pe - p < sizeof fp->digest.sha1)
			return DNS_ENOBUFS;

		memcpy(&P->data[p], fp->digest.sha1, sizeof fp->digest.sha1);
		p += sizeof fp->digest.sha1;

		break;
	default:
		return DNS_EILLEGAL;
	} /* switch() */

	n = p - P->end - 2;
	P->data[P->end++] = 0xff & (n >> 8);
	P->data[P->end++] = 0xff & (n >> 0);
	P->end = p;

	return 0;
} /* dns_sshfp_push() */


int dns_sshfp_cmp(const struct dns_sshfp *a, const struct dns_sshfp *b) {
	int cmp;

	if ((cmp = a->algo - b->algo) || (cmp = a->type - b->type))
		return cmp;

	switch (a->type) {
	case DNS_SSHFP_SHA1:
		return memcmp(a->digest.sha1, b->digest.sha1, sizeof a->digest.sha1);
	default:
		return 0;
	} /* switch() */

	/* NOT REACHED */
} /* dns_sshfp_cmp() */


size_t dns_sshfp_print(void *dst, size_t lim, struct dns_sshfp *fp) {
	static const unsigned char hex[16] = "0123456789abcdef";
	size_t i, p = 0;

	p += dns__print10(dst, lim, p, fp->algo, 0);
	p += dns__printchar(dst, lim, p, ' ');
	p += dns__print10(dst, lim, p, fp->type, 0);
	p += dns__printchar(dst, lim, p, ' ');

	switch (fp->type) {
	case DNS_SSHFP_SHA1:
		for (i = 0; i < sizeof fp->digest.sha1; i++) {
			p += dns__printchar(dst, lim, p, hex[0x0f & (fp->digest.sha1[i] >> 4)]);
			p += dns__printchar(dst, lim, p, hex[0x0f & (fp->digest.sha1[i] >> 0)]);
		}

		break;
	default:
		p += dns__printchar(dst, lim, p, '0');

		break;
	} /* switch() */

	dns__printnul(dst, lim, p);

	return p;
} /* dns_sshfp_print() */


struct dns_txt *dns_txt_init(struct dns_txt *txt, size_t size) {
	assert(size > offsetof(struct dns_txt, data));

	txt->size	= size - offsetof(struct dns_txt, data);
	txt->len	= 0;

	return txt;
} /* dns_txt_init() */


int dns_txt_parse(struct dns_txt *txt, struct dns_rr *rr, struct dns_packet *P) {
	struct { unsigned char *b; size_t p, end; } dst, src;
	unsigned n;

	dst.b	= txt->data;
	dst.p	= 0;
	dst.end	= txt->size;

	src.b	= P->data;
	src.p	= rr->rd.p;
	src.end	= src.p + rr->rd.len;

	while (src.p < src.end) {
		n	= 0xff & P->data[src.p++];

		if (src.end - src.p < n || dst.end - dst.p < n)
			return DNS_EILLEGAL;

		memcpy(&dst.b[dst.p], &src.b[src.p], n);

		dst.p	+= n;
		src.p	+= n;
	}

	txt->len	= dst.p;

	return 0;
} /* dns_txt_parse() */


int dns_txt_push(struct dns_packet *P, struct dns_txt *txt) {
	struct { unsigned char *b; size_t p, end; } dst, src;
	unsigned n;

	dst.b	= P->data;
	dst.p	= P->end;
	dst.end	= P->size;

	src.b	= txt->data;
	src.p	= 0;
	src.end	= txt->len;

	if (dst.end - dst.p < 2)
		return DNS_ENOBUFS;

	n	= txt->len + ((txt->len + 254) / 255);

	dst.b[dst.p++]	= 0xff & (n >> 8);
	dst.b[dst.p++]	= 0xff & (n >> 0);

	while (src.p < src.end) {
		n	= MIN(255, src.end - src.p);

		if (dst.p >= dst.end)
			return DNS_ENOBUFS;

		dst.b[dst.p++]	= n;

		if (dst.end - dst.p < n)
			return DNS_ENOBUFS;

		memcpy(&dst.b[dst.p], &src.b[src.p], n);

		dst.p	+= n;
		src.p	+= n;
	}

	P->end	= dst.p;

	return 0;
} /* dns_txt_push() */


int dns_txt_cmp(const struct dns_txt *a DNS_NOTUSED, const struct dns_txt *b DNS_NOTUSED) {
	return -1;
} /* dns_txt_cmp() */


size_t dns_txt_print(void *dst_, size_t lim, struct dns_txt *txt) {
	struct { unsigned char *b; size_t p, end; } dst, src;
	unsigned ch;

	dst.b	= dst_;
	dst.end	= lim;
	dst.p	= 0;

	src.b	= txt->data;
	src.end	= txt->len;
	src.p	= 0;

	dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '"');

	while (src.p < src.end) {
		ch	= src.b[src.p];

		if (0 == (src.p++ % 255) && src.p != 1) {
			dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '"');
			dst.p	+= dns__printchar(dst.b, dst.end, dst.p, ' ');
			dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '"');
		}

		if (ch < 32 || ch > 126 || ch == '"' || ch == '\\') {
			dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '\\');
			dst.p	+= dns__print10(dst.b, dst.end, dst.p, ch, 3);
		} else {
			dst.p	+= dns__printchar(dst.b, dst.end, dst.p, ch);
		}
	}

	dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '"');

	dns__printnul(dst.b, dst.end, dst.p);

	return dst.p;
} /* dns_txt_print() */


static const struct {
	enum dns_type type;
	const char *name;
	int (*parse)();
	int (*push)();
	int (*cmp)();
	size_t (*print)();
	size_t (*cname)();
} dns_rrtypes[]	= {
	{ DNS_T_A,      "A",      &dns_a_parse,      &dns_a_push,      &dns_a_cmp,      &dns_a_print,      0                },
	{ DNS_T_AAAA,   "AAAA",   &dns_aaaa_parse,   &dns_aaaa_push,   &dns_aaaa_cmp,   &dns_aaaa_print,   0                },
	{ DNS_T_MX,     "MX",     &dns_mx_parse,     &dns_mx_push,     &dns_mx_cmp,     &dns_mx_print,     &dns_mx_cname    },
	{ DNS_T_NS,     "NS",     &dns_ns_parse,     &dns_ns_push,     &dns_ns_cmp,     &dns_ns_print,     &dns_ns_cname    },
	{ DNS_T_CNAME,  "CNAME",  &dns_cname_parse,  &dns_cname_push,  &dns_cname_cmp,  &dns_cname_print,  &dns_cname_cname },
	{ DNS_T_SOA,    "SOA",    &dns_soa_parse,    &dns_soa_push,    &dns_soa_cmp,    &dns_soa_print,    0                },
	{ DNS_T_SRV,    "SRV",    &dns_srv_parse,    &dns_srv_push,    &dns_srv_cmp,    &dns_srv_print,    &dns_srv_cname   },
	{ DNS_T_OPT,    "OPT",    &dns_opt_parse,    &dns_opt_push,    &dns_opt_cmp,    &dns_opt_print,    0                },
	{ DNS_T_PTR,    "PTR",    &dns_ptr_parse,    &dns_ptr_push,    &dns_ptr_cmp,    &dns_ptr_print,    &dns_ptr_cname   },
	{ DNS_T_TXT,    "TXT",    &dns_txt_parse,    &dns_txt_push,    &dns_txt_cmp,    &dns_txt_print,    0                },
	{ DNS_T_SPF,    "SPF",    &dns_txt_parse,    &dns_txt_push,    &dns_txt_cmp,    &dns_txt_print,    0                },
	{ DNS_T_SSHFP,  "SSHFP",  &dns_sshfp_parse,  &dns_sshfp_push,  &dns_sshfp_cmp,  &dns_sshfp_print,  0                },
}; /* dns_rrtypes[] */


union dns_any *dns_any_init(union dns_any *any, size_t size) {
	return (union dns_any *)dns_txt_init(&any->rdata, size);
} /* dns_any_init() */


int dns_any_parse(union dns_any *any, struct dns_rr *rr, struct dns_packet *P) {
	unsigned i;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (dns_rrtypes[i].type == rr->type)
			return dns_rrtypes[i].parse(any, rr, P);
	}

	if (rr->rd.len > any->rdata.size)
		return DNS_EILLEGAL;

	memcpy(any->rdata.data, &P->data[rr->rd.p], rr->rd.len);
	any->rdata.len	= rr->rd.len;

	return 0;
} /* dns_any_parse() */


int dns_any_push(struct dns_packet *P, union dns_any *any, enum dns_type type) {
	unsigned i;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (dns_rrtypes[i].type == type)
			return dns_rrtypes[i].push(P, any);
	}

	if (P->size - P->end < any->rdata.len + 2)
		return DNS_ENOBUFS;

	P->data[P->end++]	= 0xff & (any->rdata.len >> 8);
	P->data[P->end++]	= 0xff & (any->rdata.len >> 0);

	memcpy(&P->data[P->end], any->rdata.data, any->rdata.len);
	P->end	+= any->rdata.len;

	return 0;
} /* dns_any_push() */


int dns_any_cmp(const union dns_any *a, enum dns_type x, const union dns_any *b, enum dns_type y) {
	unsigned i;
	int cmp;

	if ((cmp = x - y))
		return cmp;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (dns_rrtypes[i].type == x)
			return dns_rrtypes[i].cmp(a, b);
	}

	return -1;
} /* dns_any_cmp() */


size_t dns_any_print(void *dst_, size_t lim, union dns_any *any, enum dns_type type) {
	struct { unsigned char *b; size_t p, end; } dst, src;
	unsigned i, ch;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (dns_rrtypes[i].type == type)
			return dns_rrtypes[i].print(dst_, lim, any);
	}

	dst.b	= dst_;
	dst.end	= lim;
	dst.p	= 0;

	src.b	= any->rdata.data;
	src.end	= any->rdata.len;
	src.p	= 0;

	dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '"');

	while (src.p < src.end) {
		ch	= src.b[src.p++];

		dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '\\');
		dst.p	+= dns__print10(dst.b, dst.end, dst.p, ch, 3);
	}

	dst.p	+= dns__printchar(dst.b, dst.end, dst.p, '"');

	dns__printnul(dst.b, dst.end, dst.p);

	return dst.p;
} /* dns_any_print() */


size_t dns_any_cname(void *dst, size_t lim, union dns_any *any, enum dns_type type) {
	unsigned i;

	for (i = 0; i < lengthof(dns_rrtypes); i++) {
		if (dns_rrtypes[i].type == type)
			return (dns_rrtypes[i].cname)? dns_rrtypes[i].cname(dst, lim, any) : 0;
	}

	return 0;
} /* dns_any_cname() */


/*
 * H O S T S  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

struct dns_hosts {
	struct dns_hosts_entry {
		char host[DNS_D_MAXNAME + 1];
		char arpa[73 + 1];

		int af;

		union {
			struct in_addr a4;
			struct in6_addr a6;
		} addr;

		_Bool alias;

		struct dns_hosts_entry *next;
	} *head, **tail;

	dns_atomic_t refcount;
}; /* struct dns_hosts */


struct dns_hosts *dns_hosts_open(int *error) {
	static const struct dns_hosts hosts_initializer	= { .refcount = 1 };
	struct dns_hosts *hosts;

	if (!(hosts = malloc(sizeof *hosts)))
		goto syerr;

	*hosts	= hosts_initializer;

	hosts->tail	= &hosts->head;

	return hosts;
syerr:
	*error	= dns_syerr();

	free(hosts);

	return 0;
} /* dns_hosts_open() */


void dns_hosts_close(struct dns_hosts *hosts) {
	struct dns_hosts_entry *ent, *xnt;

	if (!hosts || 1 != dns_hosts_release(hosts))
		return;

	for (ent = hosts->head; ent; ent = xnt) {
		xnt	= ent->next;

		free(ent);
	}

	free(hosts);

	return;
} /* dns_hosts_close() */


unsigned dns_hosts_acquire(struct dns_hosts *hosts) {
	return dns_atomic_inc(&hosts->refcount);
} /* dns_hosts_acquire() */


unsigned dns_hosts_release(struct dns_hosts *hosts) {
	return dns_atomic_dec(&hosts->refcount);
} /* dns_hosts_release() */


struct dns_hosts *dns_hosts_mortal(struct dns_hosts *hosts) {
	if (hosts)
		dns_hosts_release(hosts);

	return hosts;
} /* dns_hosts_mortal() */


struct dns_hosts *dns_hosts_local(int *error_) {
	struct dns_hosts *hosts;
	int error;

	if (!(hosts = dns_hosts_open(&error)))
		goto error;

#ifndef _WIN32
	if ((error = dns_hosts_loadpath(hosts, "/etc/hosts")))
		goto error;
#endif
	return hosts;
error:
	*error_	= error;

	dns_hosts_close(hosts);

	return 0;
} /* dns_hosts_local() */


#define dns_hosts_issep(ch)	(isspace(ch))
#define dns_hosts_iscom(ch)	((ch) == '#' || (ch) == ';')

int dns_hosts_loadfile(struct dns_hosts *hosts, FILE *fp) {
	struct dns_hosts_entry ent;
	char word[MAX(INET6_ADDRSTRLEN, DNS_D_MAXNAME) + 1];
	unsigned wp, wc, skip;
	int ch, error;

	rewind(fp);

	do {
		memset(&ent, '\0', sizeof ent);
		wc	= 0;
		skip	= 0;

		do {
			memset(word, '\0', sizeof word);
			wp	= 0;

			while (EOF != (ch = fgetc(fp)) && ch != '\n') {
				skip	|= !!dns_hosts_iscom(ch);

				if (skip)
					continue;

				if (dns_hosts_issep(ch))
					break;

				if (wp < sizeof word - 1)
					word[wp]	= ch;
				wp++;
			}

			if (!wp)
				continue;

			wc++;

			switch (wc) {
			case 1:
				ent.af	= (strchr(word, ':'))? AF_INET6 : AF_INET;
				skip	= (1 != dns_inet_pton(ent.af, word, &ent.addr));

				break;
			default:
				dns_d_anchor(ent.host, sizeof ent.host, word, wp);

				if ((error = dns_hosts_insert(hosts, ent.af, &ent.addr, ent.host, (wc > 2))))
					return error;

				break;
			} /* switch() */
		} while (ch != EOF && ch != '\n');
	} while (ch != EOF);

	return 0;
} /* dns_hosts_loadfile() */


int dns_hosts_loadpath(struct dns_hosts *hosts, const char *path) {
	FILE *fp;
	int error;

	if (!(fp = fopen(path, "r")))
		return dns_syerr();

	error	= dns_hosts_loadfile(hosts, fp);

	fclose(fp);

	return error;
} /* dns_hosts_loadpath() */


int dns_hosts_dump(struct dns_hosts *hosts, FILE *fp) {
	struct dns_hosts_entry *ent, *xnt;
	char addr[INET6_ADDRSTRLEN + 1];
	unsigned i;

	for (ent = hosts->head; ent; ent = xnt) {
		xnt	= ent->next;

		dns_inet_ntop(ent->af, &ent->addr, addr, sizeof addr);

		fputs(addr, fp);

		for (i = strlen(addr); i < INET_ADDRSTRLEN; i++)
			fputc(' ', fp);

		fputc(' ', fp);

		fputs(ent->host, fp);
		fputc('\n', fp);
	}

	return 0;
} /* dns_hosts_dump() */


int dns_hosts_insert(struct dns_hosts *hosts, int af, const void *addr, const void *host, _Bool alias) {
	struct dns_hosts_entry *ent;
	int error;

	if (!(ent = malloc(sizeof *ent)))
		goto syerr;

	dns_d_anchor(ent->host, sizeof ent->host, host, strlen(host));

	switch ((ent->af = af)) {
	case AF_INET6:
		memcpy(&ent->addr.a6, addr, sizeof ent->addr.a6);

		dns_aaaa_arpa(ent->arpa, sizeof ent->arpa, addr);

		break;
	case AF_INET:
		memcpy(&ent->addr.a4, addr, sizeof ent->addr.a4);

		dns_a_arpa(ent->arpa, sizeof ent->arpa, addr);

		break;
	default:
		error	= EINVAL;

		goto error;
	} /* switch() */

	ent->alias	= alias;

	ent->next	= 0;
	*hosts->tail	= ent;
	hosts->tail	= &ent->next;

	return 0;
syerr:
	error	= dns_syerr();
error:
	free(ent);

	return error;
} /* dns_hosts_insert() */


struct dns_packet *dns_hosts_query(struct dns_hosts *hosts, struct dns_packet *Q, int *error_) {
	struct dns_packet *P	= dns_p_new(512);
	struct dns_packet *A	= 0;
	struct dns_rr rr;
	struct dns_hosts_entry *ent;
	int error, af;
	char qname[DNS_D_MAXNAME + 1];
	size_t qlen;

	if ((error = dns_rr_parse(&rr, 12, Q)))
		goto error;

	if (!(qlen = dns_d_expand(qname, sizeof qname, rr.dn.p, Q, &error)))
		goto error;
	else if (qlen >= sizeof qname)
		goto toolong;

	if ((error = dns_p_push(P, DNS_S_QD, qname, qlen, rr.type, rr.class, 0, 0)))
		goto error;

	switch (rr.type) {
	case DNS_T_PTR:
		for (ent = hosts->head; ent; ent = ent->next) {
			if (ent->alias || 0 != strcasecmp(qname, ent->arpa))
				continue;

			if ((error = dns_p_push(P, DNS_S_AN, qname, qlen, rr.type, rr.class, 0, ent->host)))
				goto error;
		}

		break;
	case DNS_T_AAAA:
		af	= AF_INET6;

		goto loop;
	case DNS_T_A:
		af	= AF_INET;

loop:		for (ent = hosts->head; ent; ent = ent->next) {
			if (ent->af != af || 0 != strcasecmp(qname, ent->host))
				continue;

			if ((error = dns_p_push(P, DNS_S_AN, qname, qlen, rr.type, rr.class, 0, &ent->addr)))
				goto error;
		}

		break;
	default:
		break;
	} /* switch() */


	if (!(A = dns_p_copy(dns_p_make(P->end, &error), P)))
		goto error;

	return A;
toolong:
	error = DNS_EILLEGAL;
error:
	*error_	= error;

	free(A);

	return 0;
} /* dns_hosts_query() */


/*
 * R E S O L V . C O N F  R O U T I N E S
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

struct dns_resolv_conf *dns_resconf_open(int *error) {
	static const struct dns_resolv_conf resconf_initializer
		= { .lookup = "bf", .options = { .ndots = 1, .timeout = 5, .attempts = 2, .tcp = DNS_RESCONF_TCP_ENABLE, },
		    .iface = { .ss_family = AF_INET }, };
	struct dns_resolv_conf *resconf;
	struct sockaddr_in *sin;

	if (!(resconf = malloc(sizeof *resconf)))
		goto syerr;

	*resconf = resconf_initializer;

	sin = (struct sockaddr_in *)&resconf->nameserver[0];
	sin->sin_family      = AF_INET;
	sin->sin_addr.s_addr = INADDR_ANY;
	sin->sin_port        = htons(53);
#if defined(SA_LEN)
	sin->sin_len         = sizeof *sin;
#endif

	if (0 != gethostname(resconf->search[0], sizeof resconf->search[0]))
		goto syerr;

	dns_d_anchor(resconf->search[0], sizeof resconf->search[0], resconf->search[0], strlen(resconf->search[0]));
	dns_d_cleave(resconf->search[0], sizeof resconf->search[0], resconf->search[0], strlen(resconf->search[0]));

	/*
	 * XXX: If gethostname() returned a string without any label
	 *      separator, then search[0][0] should be NUL.
	 */

	dns_resconf_acquire(resconf);

	return resconf;
syerr:
	*error	= dns_syerr();

	free(resconf);

	return 0;
} /* dns_resconf_open() */


void dns_resconf_close(struct dns_resolv_conf *resconf) {
	if (!resconf || 1 != dns_resconf_release(resconf))
		return /* void */;

	free(resconf);
} /* dns_resconf_close() */


unsigned dns_resconf_acquire(struct dns_resolv_conf *resconf) {
	return dns_atomic_inc(&resconf->_.refcount);
} /* dns_resconf_acquire() */


unsigned dns_resconf_release(struct dns_resolv_conf *resconf) {
	return dns_atomic_dec(&resconf->_.refcount);
} /* dns_resconf_release() */


struct dns_resolv_conf *dns_resconf_mortal(struct dns_resolv_conf *resconf) {
	if (resconf)
		dns_resconf_release(resconf);

	return resconf;
} /* dns_resconf_mortal() */


struct dns_resolv_conf *dns_resconf_local(int *error_) {
	struct dns_resolv_conf *resconf;
	int error;

	if (!(resconf = dns_resconf_open(&error)))
		goto error;

#ifndef _WIN32
	if ((error = dns_resconf_loadpath(resconf, "/etc/resolv.conf")))
		goto error;

	if ((error = dns_nssconf_loadpath(resconf, "/etc/nsswitch.conf"))) {
		if (error != ENOENT)
			goto error;
	}
#endif

	return resconf;
error:
	*error_	= error;

	dns_resconf_close(resconf);

	return 0;
} /* dns_resconf_local() */


struct dns_resolv_conf *dns_resconf_root(int *error) {
	struct dns_resolv_conf *resconf;

	if ((resconf = dns_resconf_local(error)))
		resconf->options.recurse = 1;

	return resconf;
} /* dns_resconf_root() */


enum dns_resconf_keyword {
	DNS_RESCONF_NAMESERVER,
	DNS_RESCONF_DOMAIN,
	DNS_RESCONF_SEARCH,
	DNS_RESCONF_LOOKUP,
	DNS_RESCONF_FILE,
	DNS_RESCONF_BIND,
	DNS_RESCONF_CACHE,
	DNS_RESCONF_OPTIONS,
	DNS_RESCONF_EDNS0,
	DNS_RESCONF_NDOTS,
	DNS_RESCONF_TIMEOUT,
	DNS_RESCONF_ATTEMPTS,
	DNS_RESCONF_ROTATE,
	DNS_RESCONF_RECURSE,
	DNS_RESCONF_SMART,
	DNS_RESCONF_TCP,
	DNS_RESCONF_TCPx,
	DNS_RESCONF_INTERFACE,
	DNS_RESCONF_ZERO,
	DNS_RESCONF_ONE,
	DNS_RESCONF_ENABLE,
	DNS_RESCONF_ONLY,
	DNS_RESCONF_DISABLE,
}; /* enum dns_resconf_keyword */ 

static enum dns_resconf_keyword dns_resconf_keyword(const char *word) {
	static const char *words[]	= {
		[DNS_RESCONF_NAMESERVER]	= "nameserver",
		[DNS_RESCONF_DOMAIN]		= "domain",
		[DNS_RESCONF_SEARCH]		= "search",
		[DNS_RESCONF_LOOKUP]		= "lookup",
		[DNS_RESCONF_FILE]		= "file",
		[DNS_RESCONF_BIND]		= "bind",
		[DNS_RESCONF_CACHE]		= "cache",
		[DNS_RESCONF_OPTIONS]		= "options",
		[DNS_RESCONF_EDNS0]		= "edns0",
		[DNS_RESCONF_ROTATE]		= "rotate",
		[DNS_RESCONF_RECURSE]		= "recurse",
		[DNS_RESCONF_SMART]		= "smart",
		[DNS_RESCONF_TCP]		= "tcp",
		[DNS_RESCONF_INTERFACE]		= "interface",
		[DNS_RESCONF_ZERO]		= "0",
		[DNS_RESCONF_ONE]		= "1",
		[DNS_RESCONF_ENABLE]		= "enable",
		[DNS_RESCONF_ONLY]		= "only",
		[DNS_RESCONF_DISABLE]		= "disable",
	};
	unsigned i;

	for (i = 0; i < lengthof(words); i++) {
		if (words[i] && 0 == strcasecmp(words[i], word))
			return i;
	}

	if (0 == strncasecmp(word, "ndots:", sizeof "ndots:" - 1))
		return DNS_RESCONF_NDOTS;

	if (0 == strncasecmp(word, "timeout:", sizeof "timeout:" - 1))
		return DNS_RESCONF_TIMEOUT;

	if (0 == strncasecmp(word, "attempts:", sizeof "attempts:" - 1))
		return DNS_RESCONF_ATTEMPTS;

	if (0 == strncasecmp(word, "tcp:", sizeof "tcp:" - 1))
		return DNS_RESCONF_TCPx;

	return -1;
} /* dns_resconf_keyword() */


/** OpenBSD-style "[1.2.3.4]:53" nameserver syntax */
static int dns_resconf_pton(struct sockaddr_storage *ss, const char *src) {
	struct { char buf[128], *p; } addr = { "", addr.buf };
	unsigned short port = 0;
	int ch, af = AF_INET, error;

	while ((ch = *src++)) {
		switch (ch) {
		case ' ':
			/* FALL THROUGH */
		case '\t':
			break;
		case '[':
			break;
		case ']':
			while ((ch = *src++)) {
				if (isdigit((unsigned char)ch)) {
					port *= 10;
					port += ch - '0';
				}
			}

			goto inet;
		case ':':
			af = AF_INET6;

			/* FALL THROUGH */
		default:
			if (addr.p < endof(addr.buf) - 1)
				*addr.p++ = ch;

			break;
		} /* switch() */
	} /* while() */
inet:

	if ((error = dns_pton(af, addr.buf, dns_sa_addr(af, ss))))
		return error;

	port = (!port)? 53 : port;
	*dns_sa_port(af, ss) = htons(port);
	dns_sa_family(ss) = af;

	return 0;
} /* dns_resconf_pton() */

#define dns_resconf_issep(ch)	(isspace(ch) || (ch) == ',')
#define dns_resconf_iscom(ch)	((ch) == '#' || (ch) == ';')

int dns_resconf_loadfile(struct dns_resolv_conf *resconf, FILE *fp) {
	unsigned sa_count	= 0;
	char words[6][DNS_D_MAXNAME + 1];
	unsigned wp, wc, i, j, n;
	int ch, error;

	rewind(fp);

	do {
		memset(words, '\0', sizeof words);
		wp	= 0;
		wc	= 0;

		while (EOF != (ch = getc(fp)) && ch != '\n') {
			if (dns_resconf_issep(ch)) {
				if (wp > 0) {
					wp	= 0;

					if (++wc >= lengthof(words))
						goto skip;
				}
			} else if (dns_resconf_iscom(ch)) {
skip:
				do {
					ch	= getc(fp);
				} while (ch != EOF && ch != '\n');

				break;
			} else {
				dns__printchar(words[wc], sizeof words[wc], wp, ch);
				wp++;
			}
		}

		if (wp > 0)
			wc++;

		if (wc < 2)
			continue;

		switch (dns_resconf_keyword(words[0])) {
		case DNS_RESCONF_NAMESERVER:
			if (sa_count >= lengthof(resconf->nameserver))
				continue;

			if ((error = dns_resconf_pton(&resconf->nameserver[sa_count], words[1])))
				continue;

			sa_count++;

			break;
		case DNS_RESCONF_DOMAIN:
		case DNS_RESCONF_SEARCH:
			memset(resconf->search, '\0', sizeof resconf->search);

			for (i = 1, j = 0; i < wc && j < lengthof(resconf->search); i++, j++)
				dns_d_anchor(resconf->search[j], sizeof resconf->search[j], words[i], strlen(words[i]));

			break;
		case DNS_RESCONF_LOOKUP:
			for (i = 1, j = 0; i < wc && j < lengthof(resconf->lookup); i++) {
				switch (dns_resconf_keyword(words[i])) {
				case DNS_RESCONF_FILE:
					resconf->lookup[j++]	= 'f';

					break;
				case DNS_RESCONF_BIND:
					resconf->lookup[j++]	= 'b';

					break;
				case DNS_RESCONF_CACHE:
					resconf->lookup[j++]	= 'c';

					break;
				default:
					break;
				} /* switch() */
			} /* for() */

			break;
		case DNS_RESCONF_OPTIONS:
			for (i = 1; i < wc; i++) {
				switch (dns_resconf_keyword(words[i])) {
				case DNS_RESCONF_EDNS0:
					resconf->options.edns0	= 1;

					break;
				case DNS_RESCONF_NDOTS:
					for (j = sizeof "ndots:" - 1, n = 0; isdigit((int)words[i][j]); j++) {
						n	*= 10;
						n	+= words[i][j] - '0';
					} /* for() */

					resconf->options.ndots	= n;

					break;
				case DNS_RESCONF_TIMEOUT:
					for (j = sizeof "timeout:" - 1, n = 0; isdigit((int)words[i][j]); j++) {
						n	*= 10;
						n	+= words[i][j] - '0';
					} /* for() */

					resconf->options.timeout	= n;

					break;
				case DNS_RESCONF_ATTEMPTS:
					for (j = sizeof "attempts:" - 1, n = 0; isdigit((int)words[i][j]); j++) {
						n	*= 10;
						n	+= words[i][j] - '0';
					} /* for() */

					resconf->options.attempts	= n;

					break;
				case DNS_RESCONF_ROTATE:
					resconf->options.rotate		= 1;

					break;
				case DNS_RESCONF_RECURSE:
					resconf->options.recurse	= 1;

					break;
				case DNS_RESCONF_SMART:
					resconf->options.smart		= 1;

					break;
				case DNS_RESCONF_TCP:
					resconf->options.tcp		= DNS_RESCONF_TCP_ONLY;

					break;
				case DNS_RESCONF_TCPx:
					switch (dns_resconf_keyword(&words[i][sizeof "tcp:" - 1])) {
					case DNS_RESCONF_ENABLE:
						resconf->options.tcp	= DNS_RESCONF_TCP_ENABLE;

						break;
					case DNS_RESCONF_ONE:
					case DNS_RESCONF_ONLY:
						resconf->options.tcp	= DNS_RESCONF_TCP_ONLY;

						break;
					case DNS_RESCONF_ZERO:
					case DNS_RESCONF_DISABLE:
						resconf->options.tcp	= DNS_RESCONF_TCP_DISABLE;

						break;
					default:
						break;
					} /* switch() */

					break;
				default:
					break;
				} /* switch() */
			} /* for() */

			break;
		case DNS_RESCONF_INTERFACE:
			for (i = 0, n = 0; isdigit((int)words[2][i]); i++) {
				n	*= 10;
				n	+= words[2][i] - '0';
			}

			dns_resconf_setiface(resconf, words[1], n);

			break;
		default:
			break;
		} /* switch() */
	} while (ch != EOF);

	return 0;
} /* dns_resconf_loadfile() */


int dns_resconf_loadpath(struct dns_resolv_conf *resconf, const char *path) {
	FILE *fp;
	int error;

	if (!(fp = fopen(path, "r")))
		return dns_syerr();

	error	= dns_resconf_loadfile(resconf, fp);

	fclose(fp);

	return error;
} /* dns_resconf_loadpath() */


struct dns_anyconf {
	char *token[16];
	unsigned count;
	char buffer[1024], *tp, *cp;
}; /* struct dns_anyconf */


static void dns_anyconf_reset(struct dns_anyconf *cf) {
	cf->count = 0;
	cf->tp = cf->cp = cf->buffer;
} /* dns_anyconf_reset() */


static int dns_anyconf_push(struct dns_anyconf *cf) {
	if (!(cf->cp < endof(cf->buffer) && cf->count < lengthof(cf->token)))
		return ENOMEM;

	*cf->cp++ = '\0';
	cf->token[cf->count++] = cf->tp;
	cf->tp = cf->cp;

	return 0;
} /* dns_anyconf_push() */


static void dns_anyconf_pop(struct dns_anyconf *cf) {
	if (cf->count > 0) {
		--cf->count;
		cf->tp = cf->cp = cf->token[cf->count];
		cf->token[cf->count] = 0;
	}
} /* dns_anyconf_pop() */


static int dns_anyconf_addc(struct dns_anyconf *cf, int ch) {
	if (!(cf->cp < endof(cf->buffer)))
		return ENOMEM;

	*cf->cp++ = ch;

	return 0;
} /* dns_anyconf_addc() */


static _Bool dns_anyconf_match(const char *pat, int mc) {
	_Bool match;
	int pc;

	if (*pat == '^') {
		match = 0;
		++pat;
	} else {
		match = 1;
	}

	while ((pc = *(const unsigned char *)pat++)) {
		switch (pc) {
		case '%':
			if (!(pc = *(const unsigned char *)pat++))
				return !match;

			switch (pc) {
			case 'a':
				if (isalpha(mc))
					return match;
				break;
			case 'd':
				if (isdigit(mc))
					return match;
				break;
			case 'w':
				if (isalnum(mc))
					return match;
				break;
			case 's':
				if (isspace(mc))
					return match;
				break;
			default:
				if (mc == pc)
					return match;
				break;
			} /* switch() */

			break;
		default:
			if (mc == pc)
				return match;
			break;
		} /* switch() */
	} /* while() */

	return !match;
} /* dns_anyconf_match() */


static int dns_anyconf_peek(FILE *fp) {
	int ch;
	ch = getc(fp);
	ungetc(ch, fp);
	return ch;
} /* dns_anyconf_peek() */


static size_t dns_anyconf_skip(const char *pat, FILE *fp) {
	size_t count = 0;
	int ch;

	while (EOF != (ch = getc(fp))) {
		if (dns_anyconf_match(pat, ch)) {
			count++;
			continue;
		}

		ungetc(ch, fp);

		break;
	}

	return count;
} /* dns_anyconf_skip() */


static size_t dns_anyconf_scan(struct dns_anyconf *cf, const char *pat, FILE *fp, int *error) {
	size_t len;
	int ch;

	while (EOF != (ch = getc(fp))) {
		if (dns_anyconf_match(pat, ch)) {
			if ((*error = dns_anyconf_addc(cf, ch)))
				return 0;

			continue;
		} else {
			ungetc(ch, fp);

			break;
		}
	}

	if ((len = cf->cp - cf->tp)) {
		if ((*error = dns_anyconf_push(cf)))
			return 0;

		return len;
	} else {
		*error = 0;

		return 0; 
	}
} /* dns_anyconf_scan() */


DNS_NOTUSED static void dns_anyconf_dump(struct dns_anyconf *cf, FILE *fp) {
	unsigned i;

	fprintf(fp, "tokens:");

	for (i = 0; i < cf->count; i++) {
		fprintf(fp, " %s", cf->token[i]);
	}

	fputc('\n', fp);
} /* dns_anyconf_dump() */


enum dns_nssconf_keyword {
	DNS_NSSCONF_INVALID = 0,
	DNS_NSSCONF_HOSTS   = 1,
	DNS_NSSCONF_SUCCESS,
	DNS_NSSCONF_NOTFOUND,
	DNS_NSSCONF_UNAVAIL,
	DNS_NSSCONF_TRYAGAIN,
	DNS_NSSCONF_CONTINUE,
	DNS_NSSCONF_RETURN,
	DNS_NSSCONF_FILES,
	DNS_NSSCONF_DNS,
	DNS_NSSCONF_MDNS,

	DNS_NSSCONF_LAST,
}; /* enum dns_nssconf_keyword */

static enum dns_nssconf_keyword dns_nssconf_keyword(const char *word) {
	static const char *list[] = {
		[DNS_NSSCONF_HOSTS]    = "hosts",
		[DNS_NSSCONF_SUCCESS]  = "success",
		[DNS_NSSCONF_NOTFOUND] = "notfound",
		[DNS_NSSCONF_UNAVAIL]  = "unavail",
		[DNS_NSSCONF_TRYAGAIN] = "tryagain",
		[DNS_NSSCONF_CONTINUE] = "continue",
		[DNS_NSSCONF_RETURN]   = "return",
		[DNS_NSSCONF_FILES]    = "files",
		[DNS_NSSCONF_DNS]      = "dns",
		[DNS_NSSCONF_MDNS]     = "mdns",
	};
	unsigned i;

	for (i = 1; i < lengthof(list); i++) {
		if (list[i] && 0 == strcasecmp(list[i], word))
			return i;
	}

	return DNS_NSSCONF_INVALID;
} /* dns_nssconf_keyword() */


static enum dns_nssconf_keyword dns_nssconf_c2k(int ch) {
	static const char map[] = {
		['S'] = DNS_NSSCONF_SUCCESS,
		['N'] = DNS_NSSCONF_NOTFOUND,
		['U'] = DNS_NSSCONF_UNAVAIL,
		['T'] = DNS_NSSCONF_TRYAGAIN,
		['C'] = DNS_NSSCONF_CONTINUE,
		['R'] = DNS_NSSCONF_RETURN,
		['f'] = DNS_NSSCONF_FILES,
		['F'] = DNS_NSSCONF_FILES,
		['d'] = DNS_NSSCONF_DNS,
		['D'] = DNS_NSSCONF_DNS,
		['b'] = DNS_NSSCONF_DNS,
		['B'] = DNS_NSSCONF_DNS,
		['m'] = DNS_NSSCONF_MDNS,
		['M'] = DNS_NSSCONF_MDNS,
	};

	return (ch >= 0 && ch < (int)lengthof(map))? map[ch] : DNS_NSSCONF_INVALID;
} /* dns_nssconf_c2k() */


DNS_PRAGMA_PUSH
DNS_PRAGMA_QUIET

static int dns_nssconf_k2c(int k) {
	static const char map[DNS_NSSCONF_LAST] = {
		[DNS_NSSCONF_SUCCESS]  = 'S',
		[DNS_NSSCONF_NOTFOUND] = 'N',
		[DNS_NSSCONF_UNAVAIL]  = 'U',
		[DNS_NSSCONF_TRYAGAIN] = 'T',
		[DNS_NSSCONF_CONTINUE] = 'C',
		[DNS_NSSCONF_RETURN]   = 'R',
		[DNS_NSSCONF_FILES]    = 'f',
		[DNS_NSSCONF_DNS]      = 'b',
		[DNS_NSSCONF_MDNS]     = 'm',
	};

	return (k >= 0 && k < (int)lengthof(map))? (map[k]? map[k] : '?') : '?';
} /* dns_nssconf_k2c() */

static const char *dns_nssconf_k2s(int k) {
	static const char *const map[DNS_NSSCONF_LAST] = {
		[DNS_NSSCONF_SUCCESS]  = "SUCCESS",
		[DNS_NSSCONF_NOTFOUND] = "NOTFOUND",
		[DNS_NSSCONF_UNAVAIL]  = "UNAVAIL",
		[DNS_NSSCONF_TRYAGAIN] = "TRYAGAIN",
		[DNS_NSSCONF_CONTINUE] = "continue",
		[DNS_NSSCONF_RETURN]