/*
 * Copyright 2005 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Niels Provos.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*-
 * Copyright (c) 1985, 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * -
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 * 
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 * -
 * --Copyright--
 */

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

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <syslog.h>
#include <stdlib.h>
#include <err.h>

#include <event.h>

#include "dnsres.h"
#include "dnsres-internal.h"
#include "resolv.h"

static void dnsres_gethostbyname2_internal(struct dnsres *_resp,
    void (*cb)(struct dnsres_hostent *, struct dnsres_cbstate *), 
    struct dnsres_cbstate *state);
static void dnsres_map_v4v6_address(const char *src, char *dst);
static void dnsres_map_v4v6_hostent(struct dnsres_hostent *hp,
    char **bp, char *);
struct dnsres_hostent *dnsres_gethtbyname2(struct dnsres *,
    struct dnsres_cbstate *, const char *, int);
struct dnsres_hostent *dnsres_gethtbyaddr(struct dnsres *,
    struct dnsres_cbstate *, const char *, int, int);

#ifdef RESOLVSORT
static void dnsres_addrsort(struct dnsres *, char **, int);
#endif

int _hokchar(const char *);

static const char AskedForGot[] =
			  "gethostby*.getanswer: asked for \"%s\", got \"%s\"";

typedef union {
	int32_t al;
	char ac;
} align;

static struct dnsres_hostent *getanswer(struct dnsres *,
    struct dnsres_cbstate *, const querybuf *, int, const char *, int);

int
_hokchar(const char *p)
{
	char c;

	/*
	 * Many people do not obey RFC 822 and 1035.  The valid
	 * characters are a-z, A-Z, 0-9, '-' and . But the others
	 * tested for below can happen, and we must be more permissive
	 * than the resolver until those idiots clean up their act.
	 * We let '/' through, but not '..'
	 */
	while ((c = *p++)) {
		if (('a' <= c && c <= 'z') ||
		    ('A' <= c && c <= 'Z') ||
		    ('0' <= c && c <= '9'))
			continue;
		if (strchr("-_/", c))
			continue;
		if (c == '.' && *p != '.')
			continue;
		return 0;
	}
	return 1;
}

static struct dnsres_hostent *
getanswer(struct dnsres *_resp, struct dnsres_cbstate *state,
    const querybuf *answer, int anslen, const char *qname, int qtype)
{
	const DNSRES_HEADER *hp;
	const u_char *cp, *eom;
	char tbuf[DNSRES_MAXDNAME];
	char *bp, **ap, **hap, *ep;
	int type, class, ancount, qdcount, n;
	int haveanswer, had_error, toobig = 0;
	const char *tname;
	int (*name_ok)(const char *);

	tname = qname;
	state->host.h_name = NULL;
	eom = answer->buf + anslen;
	switch (qtype) {
	case DNSRES_T_A:
	case DNSRES_T_AAAA:
#ifdef USE_RESOLV_NAME_OK
		name_ok = res_hnok;
		break;
#endif
	case DNSRES_T_PTR:
#ifdef USE_RESOLV_NAME_OK
		name_ok = res_dnok;
#else
		name_ok = _hokchar;
#endif
		break;
	default:
		return (NULL);
	}
	/*
	 * find first satisfactory answer
	 */
	hp = &answer->hdr;
	ancount = ntohs(hp->ancount);
	qdcount = ntohs(hp->qdcount);
	bp = state->hostbuf;
	ep = state->hostbuf + sizeof(state->hostbuf);
	cp = answer->buf + DNSRES_HFIXEDSZ;
	if (qdcount != 1) {
		_resp->dr_errno = DNSRES_NO_RECOVERY;
		return (NULL);
	}
	n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
	if ((n < 0) || !(*name_ok)(bp)) {
		_resp->dr_errno = DNSRES_NO_RECOVERY;
		return (NULL);
	}
	cp += n + DNSRES_QFIXEDSZ;
	if (qtype == DNSRES_T_A || qtype == DNSRES_T_AAAA) {
		/* res_send() has already verified that the query name is the
		 * same as the one we sent; this just gets the expanded name
		 * (i.e., with the succeeding search-domain tacked on).
		 */
		n = strlen(bp) + 1;		/* for the \0 */
		state->host.h_name = bp;
		bp += n;
		/* The qname can be abbreviated, but h_name is now absolute. */
		qname = state->host.h_name;
	}
	ap = state->host_aliases;
	*ap = NULL;
	state->host.h_aliases = state->host_aliases;
	hap = state->h_addr_ptrs;
	*hap = NULL;
	state->host.h_addr_list = state->h_addr_ptrs;
	haveanswer = 0;
	had_error = 0;
	while (ancount-- > 0 && cp < eom && !had_error) {
		n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
		if ((n < 0) || !(*name_ok)(bp)) {
			had_error++;
			continue;
		}
		cp += n;			/* name */
		if (cp >= eom)
			break;
		type = getshort(cp);
		cp += DNSRES_INT16SZ;			/* type */
		if (cp >= eom)
			break;
		class = getshort(cp);
 		cp += DNSRES_INT16SZ + DNSRES_INT32SZ;	/* class, TTL */
		if (cp >= eom)
			break;
		n = getshort(cp);
		cp += DNSRES_INT16SZ;			/* len */
		if (cp >= eom)
			break;
		if (type == DNSRES_T_SIG) {
			/* XXX - ignore signatures as we don't use them yet */
			cp += n;
			continue;
		}
		if (class != DNSRES_C_IN) {
			/* XXX - debug? syslog? */
			cp += n;
			continue;		/* XXX - had_error++ ? */
		}
		if ((qtype == DNSRES_T_A || qtype == DNSRES_T_AAAA) && type == DNSRES_T_CNAME) {
			if (ap >= &state->host_aliases[MAXALIASES-1])
				continue;
			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
			if ((n < 0) || !(*name_ok)(tbuf)) {
				had_error++;
				continue;
			}
			cp += n;
			/* Store alias. */
			*ap++ = bp;
			n = strlen(bp) + 1;	/* for the \0 */
			bp += n;
			/* Get canonical name. */
			n = strlen(tbuf) + 1;	/* for the \0 */
			if (n > ep - bp) {
				had_error++;
				continue;
			}
			strlcpy(bp, tbuf, ep - bp);
			state->host.h_name = bp;
			bp += n;
			continue;
		}
		if (qtype == DNSRES_T_PTR && type == DNSRES_T_CNAME) {
			n = dn_expand(answer->buf, eom, cp, tbuf, sizeof tbuf);
#ifdef USE_RESOLV_NAME_OK
			if ((n < 0) || !res_hnok(tbuf)) {
#else
			if ((n < 0) || !_hokchar(tbuf)) {
#endif
				had_error++;
				continue;
			}
			cp += n;
			/* Get canonical name. */
			n = strlen(tbuf) + 1;	/* for the \0 */
			if (n > ep - bp) {
				had_error++;
				continue;
			}
			strlcpy(bp, tbuf, ep - bp);
			tname = bp;
			bp += n;
			continue;
		}
		if (type != qtype) {
			syslog(LOG_NOTICE|LOG_AUTH,
	       "gethostby*.getanswer: asked for \"%s %s %s\", got type \"%s\"",
			       qname, p_class(DNSRES_C_IN), p_type(qtype),
			       p_type(type));
			cp += n;
			continue;		/* XXX - had_error++ ? */
		}
		switch (type) {
		case DNSRES_T_PTR:
			if (strcasecmp(tname, bp) != 0) {
				syslog(LOG_NOTICE|LOG_AUTH,
				       AskedForGot, qname, bp);
				cp += n;
				continue;	/* XXX - had_error++ ? */
			}
			n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
#ifdef USE_RESOLV_NAME_OK
			if ((n < 0) || !res_hnok(bp)) {
#else
			if ((n < 0) || !_hokchar(bp)) {
#endif
				had_error++;
				break;
			}
#if MULTI_PTRS_ARE_ALIASES
			cp += n;
			if (!haveanswer)
				state->host.h_name = bp;
			else if (ap < &state->host_aliases[MAXALIASES-1])
				*ap++ = bp;
			else
				n = -1;
			if (n != -1) {
				n = strlen(bp) + 1;	/* for the \0 */
				bp += n;
			}
			break;
#else
			state->host.h_name = bp;
			if (_resp->options & RES_USE_INET6) {
				n = strlen(bp) + 1;	/* for the \0 */
				bp += n;
				dnsres_map_v4v6_hostent(&host, &bp, ep);
			}
			_resp->dr_errno = DNSRES_NETDB_SUCCESS;
			return (&host);
#endif
		case DNSRES_T_A:
		case DNSRES_T_AAAA:
			if (strcasecmp(state->host.h_name, bp) != 0) {
				syslog(LOG_NOTICE|LOG_AUTH,
				       AskedForGot, state->host.h_name, bp);
				cp += n;
				continue;	/* XXX - had_error++ ? */
			}
			if (n != state->host.h_length) {
				cp += n;
				continue;
			}
			if (type == DNSRES_T_AAAA) {
				struct in6_addr in6;
				memcpy(&in6, cp, IN6ADDRSZ);
				if (IN6_IS_ADDR_V4MAPPED(&in6)) {
					cp += n;
					continue;
				}
			}
			if (!haveanswer) {
				int nn;

				state->host.h_name = bp;
				nn = strlen(bp) + 1;	/* for the \0 */
				bp += nn;
			}

			bp += sizeof(align) - ((u_long)bp % sizeof(align));

			if (bp + n >= &state->hostbuf[sizeof(state->hostbuf)]){
#ifdef DEBUG
				if (_resp->options & RES_DEBUG)
					printf("size (%d) too big\n", n);
#endif
				had_error++;
				continue;
			}
			if (hap >= &state->h_addr_ptrs[MAXADDRS-1]) {
				if (!toobig++)
#ifdef DEBUG
					if (_resp->options & RES_DEBUG)
						printf("Too many addresses (%d)\n", MAXADDRS);
#endif
				cp += n;
				continue;
			}
			bcopy(cp, *hap++ = bp, n);
			bp += n;
			cp += n;
			break;
		}
		if (!had_error)
			haveanswer++;
	}
	if (haveanswer) {
		*ap = NULL;
		*hap = NULL;
# if defined(RESOLVSORT)
		/*
		 * Note: we sort even if host can take only one address
		 * in its return structures - should give it the "best"
		 * address in that case, not some random one
		 */
		if (_resp->nsort && haveanswer > 1 && qtype == DNSRES_T_A)
			dnsres_addrsort(_resp, state->h_addr_ptrs, haveanswer);
# endif /*RESOLVSORT*/
		if (!state->host.h_name) {
			n = strlen(qname) + 1;	/* for the \0 */
			if (n > ep - bp)
				goto try_again;
			strlcpy(bp, qname, ep - bp);
			state->host.h_name = bp;
			bp += n;
		}
		if (_resp->options & RES_USE_INET6)
			dnsres_map_v4v6_hostent(&state->host, &bp, ep);
		_resp->dr_errno = DNSRES_NETDB_SUCCESS;
		return (&state->host);
	}
 try_again:
	_resp->dr_errno = DNSRES_TRY_AGAIN;
	return (NULL);
}

struct dnsres_cbstate *
dnsres_cbstate_new(struct dnsres *_resp, const char *name, size_t len,
        void (*cb)(struct dnsres_hostent *, int, void *), void *arg)
{
	struct dnsres_cbstate *state;

	state = calloc(1, sizeof(struct dnsres_cbstate));
	if (state == NULL)
		err(1, "%s: calloc", __func__);

	/* Set up all of our call back state */
	state->cb = cb;
	state->cb_arg = arg;
	state->_resp = _resp;
	state->name = malloc(len);
	if (state->name == NULL)
		err(1, "%s: strdup", __func__);
	memcpy(state->name, name, len);
	state->name_len = len;

	state->buf = malloc(sizeof(querybuf));
	if (state->buf == NULL)
		err(1, "%s: malloc", __func__);

	return (state);
}

void
dnsres_cbstate_free(struct dnsres_cbstate *state)
{
	free(state->buf);
	state->buf = NULL;
	free(state->name);
	free(state);
}

void
dnsres_cancel_lookup(void *arg)
{
	struct dnsres_cbstate *state = arg;

	/* Indicates that the callback has been cancelled */
	state->cb = NULL;
}

static void
dnsres_usercb(int fd, short what, void *arg)
{
	struct dnsres_cbstate *state = arg;
	struct dnsres_hostent *hp = state->hp;

	if (state->cb != NULL)
		(*state->cb)(hp, state->_resp->dr_errno, state->cb_arg);

	/* Free the dnsres callback state */
	dnsres_cbstate_free(state);
}

void
dnsres_gethostbyname_cb(struct dnsres_hostent *hp,
    struct dnsres_cbstate *state)
{
	if (hp == NULL && state->af == AF_INET6) {
		/* Retry by looking for IPv4 addresses */
		state->af = AF_INET;
		dnsres_gethostbyname2_internal(state->_resp,
		    dnsres_gethostbyname_cb, state);
		return;
	}

	/* Callout to libevent */
	state->hp = hp;
	event_once(-1, EV_TIMEOUT, dnsres_usercb, state, NULL);
}

/* BLOCKING */
void *
dnsres_gethostbyname(struct dnsres *_resp, const char *name,
    void (*cb)(struct dnsres_hostent *, int, void *), void *arg)
{
	struct dnsres_cbstate *state;

	state = dnsres_cbstate_new(_resp, name, strlen(name) + 1, cb, arg);

	if (_resp->options & RES_USE_INET6) {
		state->af = AF_INET6;	/* retry AF_INET on failure */
		dnsres_gethostbyname2_internal(_resp,
		    dnsres_gethostbyname_cb, state);
	} else {
		state->af = AF_INET;
		dnsres_gethostbyname2_internal(_resp,
		    dnsres_gethostbyname_cb, state);
	}

	return (state);
}

void
dnsres_reset_state(struct dnsres_cbstate *state, const char *name)
{
	strlcpy(state->hostbuf, name, MAXHOSTNAMELEN);
	state->host.h_name = state->hostbuf;
	state->host.h_aliases = state->host_aliases;
	state->host_aliases[0] = NULL;
	state->h_addr_ptrs[0] = (char *)state->host_addr;
	state->h_addr_ptrs[1] = NULL;
	state->host.h_addr_list = state->h_addr_ptrs;
}

/*
 * Callback that res_search is going to use to get back to us
 * n contains the length of the result and is negative on error.
 */

void dnsres_search_caller(struct dnsres_cbstate *state);

void
dnsres_search_cb(int n, void *arg)
{
	struct dnsres_cbstate *state = arg;
	struct dnsres_hostent *hp = NULL;
	struct dnsres *_resp = state->_resp;
	if ( n >= 0 ) {
		hp = getanswer(_resp, state, state->buf, n,
		    state->name, state->q.qtype);
	}
#ifdef DEBUG
	else {
		if (_resp->options & RES_DEBUG)
			printf("res_search failed\n");
	}
#endif

	state->hp = hp;

	/* continue on to next iteration */
	dnsres_search_caller(state);
}

/* 
 * This callback fakes the iteration through the different lookup
 * methods.
 */

void
dnsres_search_caller(struct dnsres_cbstate *state)
{
	struct dnsres_hostent *hp = NULL;
	struct dnsres *_resp = state->_resp;
	const char *name = state->name;

 again:
	if (state->hp != NULL || state->lookup_index == MAXDNSLUS) {
		/* We either got a result or we have reached our end of live */
		(*state->internal_cb)(state->hp, state);
		return;
	}

	switch (state->lookups[state->lookup_index++]) {
	case 'f':
		hp = dnsres_gethtbyname2(_resp, state, name, state->af);
		if (hp == NULL)
			dnsres_search_caller(state);
		else
			(*state->internal_cb)(hp, state);
		break;
	case 'b':
		/* BLOCKING */
		res_search(_resp, name, &state->q, dnsres_search_cb, state);
		break;
	default:
		/* Try the loop again */
		goto again;
	}

}

void
dnsres_gethostbyname2_cb(struct dnsres_hostent *hp,
    struct dnsres_cbstate *state)
{
	/* Callout to libevent */
	state->hp = hp;
	event_once(-1, EV_TIMEOUT, dnsres_usercb, state, NULL);
}

void *
dnsres_gethostbyname2(struct dnsres *_resp, const char *name, int af,
    void (*cb)(struct dnsres_hostent *, int, void *), void *cb_arg)
{
	struct dnsres_cbstate *state;

	state = dnsres_cbstate_new(_resp, name, strlen(name) + 1, cb, cb_arg);
	state->af = af;
	dnsres_gethostbyname2_internal(_resp, dnsres_gethostbyname2_cb, state);

	return (state);
}

/* BLOCKING */
static void
dnsres_gethostbyname2_internal(struct dnsres *_resp,
    void (*cb)(struct dnsres_hostent *, struct dnsres_cbstate *), 
    struct dnsres_cbstate *state)
{
	unsigned char *name = state->name;
	int af = state->af;
	const unsigned char *cp;
	char *bp, *ep;

	switch (af) {
	case AF_INET:
		state->size = INADDRSZ;
		state->q.qclass = DNSRES_C_IN;
		state->q.qtype = DNSRES_T_A;
		state->q.answer = state->buf->buf;
		state->q.anslen = sizeof(state->buf->buf);
		break;
	case AF_INET6:
		state->size = IN6ADDRSZ;
		state->q.qclass = DNSRES_C_IN;
		state->q.qtype = DNSRES_T_AAAA;
		state->q.answer = state->buf->buf;
		state->q.anslen = sizeof(state->buf->buf);
		break;
	default:
		_resp->dr_errno = DNSRES_NETDB_INTERNAL;
		errno = EAFNOSUPPORT;  /* How do deal with this? */
		(*cb)(NULL, state);
		return;
	}

	state->host.h_addrtype = af;
	state->host.h_length = state->size;
	state->internal_cb = cb;
	state->hp = NULL;

	/*
	 * if there aren't any dots, it could be a user-level alias.
	 * this is also done in res_query() since we are not the only
	 * function that looks up host names.
	 */
	if (!strchr(name, '.') && (cp = hostalias(_resp, name))) {
		/* Update the name that we use for the lookup */
		state->name_len = strlen(cp) + 1;
		state->name = strdup(cp);
		if (state->name == NULL)
			err(1, "%s: strdup", __func__);
		free(name);
		name = state->name;
	}

	/*
	 * disallow names consisting only of digits/dots, unless
	 * they end in a dot.
	 */
	if (isdigit(name[0]))
		for (cp = name;; ++cp) {
			if (!*cp) {
				if (*--cp == '.')
					break;
				/*
				 * All-numeric, no dot at the end.
				 * Fake up a hostent as if we'd actually
				 * done a lookup.
				 */
				if (inet_pton(af, name,
					state->host_addr) <= 0) {
					_resp->dr_errno = DNSRES_HOST_NOT_FOUND;
					(*cb)(NULL, state);
					return;
				}
				dnsres_reset_state(state, name);
				bp = state->hostbuf + MAXHOSTNAMELEN;
				ep = state->hostbuf + sizeof(state->hostbuf);
				if (_resp->options & RES_USE_INET6)
					dnsres_map_v4v6_hostent(&state->host,
					    &bp, ep);
				_resp->dr_errno = DNSRES_NETDB_SUCCESS;
				(*cb)(&state->host, state);
				return;
			}
			if (!isdigit(*cp) && *cp != '.') 
				break;
		}
	if ((isxdigit(name[0]) && strchr(name, ':') != NULL) ||
	    name[0] == ':')
		for (cp = name;; ++cp) {
			if (!*cp) {
				if (*--cp == '.')
					break;
				/*
				 * All-IPv6-legal, no dot at the end.
				 * Fake up a hostent as if we'd actually
				 * done a lookup.
				 */
				if (inet_pton(af, name,
					state->host_addr) <= 0) {
					_resp->dr_errno = DNSRES_HOST_NOT_FOUND;
					(*cb)(NULL, state);
					return;
				}
				dnsres_reset_state(state, name);
				bp = state->hostbuf + MAXHOSTNAMELEN;
				ep = state->hostbuf + sizeof(state->hostbuf);
				_resp->dr_errno = DNSRES_NETDB_SUCCESS;
				(*cb)(&state->host, state);
				return;
			}
			if (!isxdigit(*cp) && *cp != ':' && *cp != '.') 
				break;
		}

	bcopy(_resp->lookups, state->lookups, sizeof(state->lookups));
	if (state->lookups[0] == '\0')
		strlcpy(state->lookups, "bf", sizeof(state->lookups));
	state->lookup_index = 0;

	/* This used to be a loop, now the callback keeps it's own logic */
	dnsres_search_caller(state);

	return;
}

/* This call is BLOCKING */
void dnsres_gethostbyaddr_loop_cb(int n, void *state);
void dnsres_gethostbyaddr_loop(struct dnsres_cbstate *state);

void *
dnsres_gethostbyaddr(struct dnsres *_resp, const char *addr, int len, int af,
    void (*cb)(struct dnsres_hostent *, int, void *), void *arg)
{
	struct dnsres_cbstate *state;
	const u_char *uaddr = (const u_char *)addr;
	int n, size, i;
	char *qp, *ep;

	state = dnsres_cbstate_new(_resp, addr, len, cb, arg);
	state->af = af;
	
	if (af == AF_INET6 && len == IN6ADDRSZ &&
	    (IN6_IS_ADDR_LINKLOCAL((struct in6_addr *)uaddr) ||
	     IN6_IS_ADDR_SITELOCAL((struct in6_addr *)uaddr))) {
		_resp->dr_errno = DNSRES_HOST_NOT_FOUND;
		state->hp = NULL;
		event_once(-1, EV_TIMEOUT, dnsres_usercb, state, NULL);
		return (state);
	}
	if (af == AF_INET6 && len == IN6ADDRSZ &&
	    (IN6_IS_ADDR_V4MAPPED((struct in6_addr *)uaddr) ||
	     IN6_IS_ADDR_V4COMPAT((struct in6_addr *)uaddr))) {
		/* Unmap. */
		addr += IN6ADDRSZ - INADDRSZ;
		uaddr += IN6ADDRSZ - INADDRSZ;
		af = AF_INET;
		len = INADDRSZ;
	}
	switch (af) {
	case AF_INET:
		size = INADDRSZ;
		state->q.qclass = DNSRES_C_IN;
		state->q.qtype = DNSRES_T_PTR;
		state->q.answer = state->buf->buf;
		state->q.anslen = sizeof(state->buf->buf);
		break;
	case AF_INET6:
		size = IN6ADDRSZ;
		state->q.qclass = DNSRES_C_IN;
		state->q.qtype = DNSRES_T_PTR;
		state->q.answer = state->buf->buf;
		state->q.anslen = sizeof(state->buf->buf);
		break;
	default:
		errno = EAFNOSUPPORT;
		_resp->dr_errno = DNSRES_NETDB_INTERNAL;
		event_once(-1, EV_TIMEOUT, dnsres_usercb, state, NULL);
		return (state);
	}
	if (size != len) {
		errno = EINVAL;
		_resp->dr_errno = DNSRES_NETDB_INTERNAL;
		event_once(-1, EV_TIMEOUT, dnsres_usercb, state, NULL);
		return (state);
	}
	ep = state->qbuf + sizeof(state->qbuf);
	switch (af) {
	case AF_INET:
		(void) snprintf(state->qbuf, sizeof state->qbuf,
		    "%u.%u.%u.%u.in-addr.arpa",
		    (uaddr[3] & 0xff), (uaddr[2] & 0xff),
		    (uaddr[1] & 0xff), (uaddr[0] & 0xff));
		break;
	case AF_INET6:
		qp = state->qbuf;
		for (n = IN6ADDRSZ - 1; n >= 0; n--) {
			i = snprintf(qp, ep - qp, "%x.%x.",
			    uaddr[n] & 0xf, (uaddr[n] >> 4) & 0xf);
			if (i <= 0) {
				errno = EINVAL;
				_resp->dr_errno = DNSRES_NETDB_INTERNAL;
				event_once(-1, EV_TIMEOUT, dnsres_usercb,
				    state, NULL);
				return (state);
			}
			qp += i;
		}
		strlcpy(qp, "ip6.arpa", ep - qp);
		break;
	}

	bcopy(_resp->lookups, state->lookups, sizeof(state->lookups));
	if (state->lookups[0] == '\0')
		strlcpy(state->lookups, "bf", sizeof(state->lookups));

	state->hp = NULL;
	state->lookup_index = 0;
	dnsres_gethostbyaddr_loop(state);

	return (state);
}

void
dnsres_gethostbyaddr_loop(struct dnsres_cbstate *state)
{
	struct dnsres *_resp = state->_resp;

	/* Check look termination */
	if (state->lookup_index >= MAXDNSLUS ||
	    state->hp != NULL ||
	    !state->lookups[state->lookup_index]) {
		/* XXX dr_errno not correct in all cases... */
		event_once(-1, EV_TIMEOUT, dnsres_usercb, state, NULL);
		return;
	}

	switch (state->lookups[state->lookup_index++]) {
	case 'b':
		/* BLOCKING */
		res_query(_resp, state->qbuf, &state->q,
		    dnsres_gethostbyaddr_loop_cb, state);
		return;
	case 'f':
		state->hp = dnsres_gethtbyaddr(_resp, state,
		    state->name, state->name_len, state->af);
		break;
	}

	/* We are done or not */
	dnsres_gethostbyaddr_loop(state);
}

void
dnsres_gethostbyaddr_loop_cb(int n, void *arg)
{
	struct dnsres_cbstate *state = arg;
	struct dnsres* _resp = state->_resp;

	if (n < 0) {
#ifdef DEBUG
		if (_resp->options & RES_DEBUG)
			printf("res_query failed\n");
#endif
	} else {
		struct dnsres_hostent *hp;
		hp = state->hp = getanswer(_resp, state,
		    state->buf, n, state->qbuf, DNSRES_T_PTR);
		if (hp != NULL ) {
			hp->h_addrtype = state->af;
			hp->h_length = state->name_len;
			bcopy(state->name, state->host_addr, state->name_len);
			state->h_addr_ptrs[0] = (char *)state->host_addr;
			state->h_addr_ptrs[1] = NULL;
			if (state->af == AF_INET && (_resp->options & RES_USE_INET6)) {
				dnsres_map_v4v6_address(
					(char*)state->host_addr,
					(char*)state->host_addr);
				hp->h_addrtype = AF_INET6;
				hp->h_length = IN6ADDRSZ;
			}
			_resp->dr_errno = DNSRES_NETDB_SUCCESS;
		}
	}

	/* Continue in the loop if we still can */
	dnsres_gethostbyaddr_loop(state);
}

void
dnsres_sethtent(struct dnsres_hostent_state *state, int f)
{
	if (state->hostf == NULL)
		state->hostf = fopen(DNSRES_PATH_HOSTS, "r" );
	else
		rewind(state->hostf);
	state->stayopen = f;
}

void
dnsres_endhtent(struct dnsres_hostent_state *state)
{
	if (state->hostf && !state->stayopen) {
		(void) fclose(state->hostf);
		state->hostf = NULL;
	}
}

struct dnsres_hostent *
dnsres_gethtent(struct dnsres *_resp, struct dnsres_cbstate *state)
{
	struct dnsres_hostent_state *hostent = &_resp->hostent_state;
	char *p, *cp, **q;
	int af;
	size_t len;

	if (!hostent->hostf &&
	    !(hostent->hostf = fopen(DNSRES_PATH_HOSTS, "r" ))) {
		_resp->dr_errno = DNSRES_NETDB_INTERNAL;
		return (NULL);
	}
 again:
	if ((p = fgetln(hostent->hostf, &len)) == NULL) {
		_resp->dr_errno = DNSRES_HOST_NOT_FOUND;
		return (NULL);
	}
	if (p[len-1] == '\n')
		len--;
	if (len >= sizeof(state->hostbuf) || len == 0)
		goto again;
	p = memcpy(state->hostbuf, p, len);
	state->hostbuf[len] = '\0';
	if (*p == '#')
		goto again;
	if ((cp = strchr(p, '#')))
		*cp = '\0';
	if (!(cp = strpbrk(p, " \t")))
		goto again;
	*cp++ = '\0';
	if (inet_pton(AF_INET6, p, state->host_addr) > 0) {
		af = AF_INET6;
		len = IN6ADDRSZ;
	} else if (inet_pton(AF_INET, p, state->host_addr) > 0) {
		if (_resp->options & RES_USE_INET6) {
			dnsres_map_v4v6_address(
				(char*)state->host_addr,
				(char*)state->host_addr);
			af = AF_INET6;
			len = IN6ADDRSZ;
		} else {
			af = AF_INET;
			len = INADDRSZ;
		}
	} else {
		goto again;
	}
	/* if this is not something we're looking for, skip it. */
	if (state->host.h_addrtype != af)
		goto again;
	if (state->host.h_length != len)
		goto again;
	state->h_addr_ptrs[0] = (char *)state->host_addr;
	state->h_addr_ptrs[1] = NULL;
	state->host.h_addr_list = state->h_addr_ptrs;
	state->host.h_length = len;
	state->host.h_addrtype = af;
	while (*cp == ' ' || *cp == '\t')
		cp++;
	state->host.h_name = cp;
	q = state->host.h_aliases = state->host_aliases;
	if ((cp = strpbrk(cp, " \t")))
		*cp++ = '\0';
	while (cp && *cp) {
		if (*cp == ' ' || *cp == '\t') {
			cp++;
			continue;
		}
		if (q < &state->host_aliases[MAXALIASES - 1])
			*q++ = cp;
		if ((cp = strpbrk(cp, " \t")))
			*cp++ = '\0';
	}
	*q = NULL;
	if (_resp->options & RES_USE_INET6) {
		char *bp = state->hostbuf;
		char *ep = state->hostbuf + sizeof(state->hostbuf);

		dnsres_map_v4v6_hostent(&state->host, &bp, ep);
	}
	_resp->dr_errno = DNSRES_NETDB_SUCCESS;
	return (&state->host);
}

struct dnsres_hostent *
dnsres_gethtbyname(struct dnsres *_resp, struct dnsres_cbstate *state,
    const char *name)
{
	struct dnsres_hostent *hp;

	if (_resp->options & RES_USE_INET6) {
		hp = dnsres_gethtbyname2(_resp, state, name, AF_INET6);
		if (hp)
			return (hp);
	}
	return (dnsres_gethtbyname2(_resp, state, name, AF_INET));
}

struct dnsres_hostent *
dnsres_gethtbyname2(struct dnsres *_resp, struct dnsres_cbstate *state,
    const char *name, int af)
{
	struct dnsres_hostent *p;
	char **cp;
	
	dnsres_sethtent(&_resp->hostent_state, 0);
	while ((p = dnsres_gethtent(_resp, state))) {
		if (p->h_addrtype != af)
			continue;
		if (strcasecmp(p->h_name, name) == 0)
			break;
		for (cp = p->h_aliases; *cp != 0; cp++)
			if (strcasecmp(*cp, name) == 0)
				goto found;
	}
 found:
	dnsres_endhtent(&_resp->hostent_state);
	return (p);
}

struct dnsres_hostent *
dnsres_gethtbyaddr(struct dnsres *_resp, struct dnsres_cbstate *state,
    const char *addr, int len, int af)
{
	struct dnsres_hostent *p;

	state->host.h_length = len;
	state->host.h_addrtype = af;

	dnsres_sethtent(&_resp->hostent_state, 0);
	while ((p = dnsres_gethtent(_resp, state)))
		if (p->h_addrtype == af && !bcmp(p->h_addr_list[0], addr, len))
			break;
	dnsres_endhtent(&_resp->hostent_state);
	return (p);
}


static void
dnsres_map_v4v6_address(const char *src, char *dst)
{
	u_char *p = (u_char *)dst;
	char tmp[INADDRSZ];
	int i;

	/* Stash a temporary copy so our caller can update in place. */
	bcopy(src, tmp, INADDRSZ);
	/* Mark this ipv6 addr as a mapped ipv4. */
	for (i = 0; i < 10; i++)
		*p++ = 0x00;
	*p++ = 0xff;
	*p++ = 0xff;
	/* Retrieve the saved copy and we're done. */
	bcopy(tmp, (void*)p, INADDRSZ);
}

static void
dnsres_map_v4v6_hostent(struct dnsres_hostent *hp, char **bpp, char *ep)
{
	char **ap;

	if (hp->h_addrtype != AF_INET || hp->h_length != INADDRSZ)
		return;
	hp->h_addrtype = AF_INET6;
	hp->h_length = IN6ADDRSZ;
	for (ap = hp->h_addr_list; *ap; ap++) {
		int i = sizeof(align) - ((u_long)*bpp % sizeof(align));

		if (ep - *bpp < (i + IN6ADDRSZ)) {
			/* Out of memory.  Truncate address list here.  XXX */
			*ap = NULL;
			return;
		}
		*bpp += i;
		dnsres_map_v4v6_address(*ap, *bpp);
		*ap = *bpp;
		*bpp += IN6ADDRSZ;
	}
}

struct dnsres_hostent *
dnsres_gethostent(struct dnsres *_resp, struct dnsres_cbstate *state)
{
	return (dnsres_gethtent(_resp, state));
}

#ifdef RESOLVSORT
static void
dnsres_addrsort(struct dnsres *_resp, char **ap, int num)
{
	int i, j;
	char **p;
	short aval[MAXADDRS];
	int needsort = 0;

	p = ap;
	for (i = 0; i < num; i++, p++) {
		for (j = 0 ; (unsigned)j < _resp->nsort; j++)
			if (_resp->sort_list[j].addr.s_addr == 
			    (((struct in_addr *)(*p))->s_addr & 
			    _resp->sort_list[j].mask))
				break;
		aval[i] = j;
		if (needsort == 0 && i > 0 && j < aval[i-1])
			needsort = i;
	}
	if (!needsort)
		return;

	while (needsort < num) {
		for (j = needsort - 1; j >= 0; j--) {
			if (aval[j] > aval[j+1]) {
				char *hp;

				i = aval[j];
				aval[j] = aval[j+1];
				aval[j+1] = i;

				hp = ap[j];
				ap[j] = ap[j+1];
				ap[j+1] = hp;
			} else
				break;
		}
		needsort++;
	}
}
#endif