/*
 * 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.
 */

/*	$OpenBSD: res_query.c,v 1.21 2003/06/02 20:18:36 millert Exp $	*/

/*
 * ++Copyright++ 1988, 1993
 * -
 * Copyright (c) 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/types.h>
#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 <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <err.h>
#include <event.h>

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

#ifndef HAVE_ISSETUGID
#define issetugid()	0
#endif

const char *hostalias(struct dnsres *, const char *);

struct res_search_state *
res_search_state_new(
	struct dnsres *_resp,
	const char *name,	/* domain name */
	struct dnsres_target *q,
	void (*cb)(int, void *),
	void *cb_arg
    )
{
	struct res_search_state *state = calloc(1, sizeof(*state));
	if (state == NULL)
		err(1, "%s: calloc", __func__);

	state->_resp = _resp;
	state->target = q;
	state->name = name;
	state->cb = cb;
	state->cb_arg = cb_arg;

	res_init_socket(&state->ds);

	return (state);
}

/*
 * Formulate a normal query, send, and await answer.
 * Returned answer is placed in supplied buffer "answer".
 * Perform preliminary check of answer, returning success only
 * if no error is indicated and the answer count is nonzero.
 * Return the size of the response on success, -1 on error.
 * Error number is left in dr_errno.
 *
 * Caller must parse answer and determine whether it answers the question.
 */

void res_query_cb(int, struct res_search_state *);
void res_query_next(struct res_search_state *state);

void
res_query(
	struct dnsres *_resp,
	const char *name,	/* domain name */
	struct dnsres_target *q,
	void (*cb)(int, void *),
	void *cb_arg
    )
{
	struct res_search_state *state;

	/* Create a copy of our current state for callbacks */
	state = res_search_state_new(_resp, name, q, cb, cb_arg);

	res_query_next(state);
}

void
res_query_next(struct res_search_state *state)
{
	struct dnsres *_resp = state->_resp;
	struct dnsres_target *q = state->target;
	DNSRES_HEADER *hp = (DNSRES_HEADER *) q->answer;
	int n;

	hp->rcode = DNSRES_NOERROR;	/* default */

#ifdef DEBUG
	if (_resp->options & RES_DEBUG)
		printf(";; res_query(%s, %d, %d)\n", name, class, type);
#endif

	n = res_mkquery(_resp, DNSRES_QUERY,
	    state->name, q->qclass, q->qtype, NULL, 0, NULL,
	    state->buf, sizeof(state->buf));
	if (n > 0 && ((_resp->options & RES_USE_EDNS0) ||
	    (_resp->options & RES_USE_DNSSEC))) {
		n = res_opt(_resp, n,
		    state->buf, sizeof(state->buf), q->anslen);
	}

	if (n <= 0) {
#ifdef DEBUG
		if (_resp->options & RES_DEBUG)
			printf(";; res_query: mkquery failed\n");
#endif
		_resp->dr_errno = DNSRES_NO_RECOVERY;
		(*state->cb)(n, state->cb_arg);
		free(state);
		return;
	}
	res_send(_resp, state->buf, n, q->answer, q->anslen,
	    res_query_cb, state); /* BLOCKING */
	return;
}

void
res_query_cb(int n, struct res_search_state *state)
{
	struct dnsres *_resp = state->_resp;
	DNSRES_HEADER *hp = (DNSRES_HEADER *) state->target->answer;

	/* Count our success */
	if (n > 0 && hp->rcode == DNSRES_NOERROR && ntohs(hp->ancount) != 0) {
		state->ancount += n;
		state->target->n = n;
	}

	/* Let's try again we if can */
	if (state->target->next != NULL) {
		state->target = state->target->next;
		res_query_next(state);
		return;
	}

	if (state->ancount == 0) {
#ifdef DEBUG
		if (_resp->options & RES_DEBUG)
			printf(";; rcode = %u, ancount=%u\n", hp->rcode,
			    ntohs(hp->ancount));
#endif
		switch (hp->rcode) {
		case DNSRES_NXDOMAIN:
			_resp->dr_errno = DNSRES_HOST_NOT_FOUND;
			break;
		case DNSRES_SERVFAIL:
			_resp->dr_errno = DNSRES_TRY_AGAIN;
			break;
		case DNSRES_NOERROR:
			_resp->dr_errno = DNSRES_NO_DATA;
			break;
		case DNSRES_FORMERR:
		case DNSRES_NOTIMP:
		case DNSRES_REFUSED:
		default:
			_resp->dr_errno = DNSRES_NO_RECOVERY;
			break;
		}
		(*state->cb)(-1, state->cb_arg);
		free(state);
		return;
	}

	(*state->cb)(state->ancount, state->cb_arg);
	free(state);
}

/*
 * WARNING:
 * The original res_search got split apart at all blocking points.  Due to
 * conditional branches that means that every blocking part needs to be split
 * into a separate function.  I realize that this is very ugly and proponents
 * of threading are going to say: See, I told you.  That is as it may be,
 * the goal is to make this non-blocking and the road to there is very ugly.
 *			- niels
 */

/* This callback means we are done and supposed to return to the upper level */

void
res_search_cb_done(int ret, void *arg)
{
	struct res_search_state *res_state = arg;
	(*res_state->cb)(ret, res_state->cb_arg);
	free(res_state);
}

void res_search_cb_eval(int ret, void *arg);
void res_search_continue(struct res_search_state *res_state);
void res_search_domain_loop(struct res_search_state *res_state);
void res_search_domain_loopbottom(struct res_search_state *res_state);
void res_search_almostbottom(struct res_search_state *res_state);
void res_search_bottom(struct res_search_state *res_state);

/*
 * Formulate a normal query, send, and retrieve answer in supplied buffer.
 * Return the size of the response on success, -1 on error.
 * If enabled, implement search rules until answer or unrecoverable failure
 * is detected.  Error code, if any, is left in dr_errno.
 *
 * The callback and callback argument are opaque to this function.
 *
 * This is a BLOCKING call.
 */
void
res_search(
	struct dnsres *_resp,
	const char *name,	/* domain name */
	struct dnsres_target *q,
	void (*cb)(int, void *),
	void *state
    )
{
	const char *cp;
	u_int dots;
	int trailing_dot;
	struct res_search_state *res_state;

	/* Create the callback state for this part */
	res_state = res_search_state_new(_resp, name, q, cb, state);

	errno = 0;
	/* default, if we never query */
	_resp->dr_errno = DNSRES_HOST_NOT_FOUND;
	dots = 0;
	for (cp = name; *cp; cp++)
		dots += (*cp == '.');
	trailing_dot = 0;
	if (cp > name && *--cp == '.')
		trailing_dot++;

	res_state->trailing_dot = trailing_dot;
	res_state->dots = dots;

	/*
	 * if there aren't any dots, it could be a user-level alias
	 */
	if (!dots && (cp = hostalias(_resp, name)) != NULL) {
		/* BLOCKING */
		res_query(_resp, cp, q, res_search_cb_done, res_state);
		return;
	}

	/*
	 * If there are dots in the name already, let's just give it a try
	 * 'as is'.  The threshold can be set with the "ndots" option.
	 */
	res_state->saved_herrno = -1;
	if (dots >= _resp->ndots) {
		/* BLOCKING */

		/* We have a primitive form of conditional here */
		res_state->res_conditional_cb = res_search_continue;
		res_state->tried_as_is++;

		res_querydomain(_resp, name, NULL, q,
		    res_search_cb_eval, res_state);
		return;
	}

	res_search_continue(res_state);
}

/* This callback is called when we tried the name as is because it got dots */
void
res_search_cb_eval(int ret, void *arg)
{
	struct res_search_state *res_state = arg;
	struct dnsres *_resp = res_state->_resp;
	if (ret > 0) {
		/* We are done */
		(*res_state->cb)(ret, res_state->cb_arg);
		free(res_state);
		return;
	}

	/* The second time we try-as-is we don't want to save the errno */
	if (!res_state->dont_save_errno)
		res_state->saved_herrno = _resp->dr_errno;

	(*res_state->res_conditional_cb)(res_state);
}

void
res_search_continue(struct res_search_state *res_state)
{
	struct dnsres *_resp = res_state->_resp;
	u_int dots = res_state->dots;
	int trailing_dot = res_state->trailing_dot;

	/*
	 * We do at least one level of search if
	 *	- there is no dot and RES_DEFNAME is set, or
	 *	- there is at least one dot, there is no trailing dot,
	 *	  and RES_DNSRCH is set.
	 */
	if ((!dots && (_resp->options & RES_DEFNAMES)) ||
	    (dots && !trailing_dot && (_resp->options & RES_DNSRCH))) {
		/* Setup the variable for the loop */
		res_state->dont_save_errno = 1;
		res_state->done = 0;
		res_state->domain = (const char * const *)_resp->dnsrch;

		res_search_domain_loop(res_state);
		return;
	}

	res_search_almostbottom(res_state);
}

void
res_search_domain_loop(struct res_search_state *res_state)
{
	const char *cur_domain;
	struct dnsres_target *target = res_state->target;
	
	/* Check termination of the loop */
	if (!*res_state->domain || res_state->done) {
		res_search_almostbottom(res_state);
		return;
	}

	cur_domain = *res_state->domain;

	/* Prepare for next loop */
	res_state->domain++;

	/* BLOCKING */
	res_state->res_conditional_cb = res_search_domain_loopbottom;

	res_querydomain(res_state->_resp,
	    res_state->name, cur_domain, target,
	    res_search_cb_eval, res_state);
	return;
}

void
res_search_domain_loopbottom(struct res_search_state *res_state)
{
	struct dnsres *_resp = res_state->_resp;

	/*
	 * If no server present, give up.
	 * If name isn't found in this domain, keep trying higher
	 * domains in the search list (if that's enabled).
	 * On a NO_DATA error, keep trying, otherwise a wildcard
	 * entry of another type could keep us from finding this
	 * entry higher in the domain.
	 * If we get some other error (negative answer or server
	 * failure), then stop searching up, but try the input name
	 * below in case it's fully-qualified.
	 */
	if (errno == ECONNREFUSED) {
		_resp->dr_errno = DNSRES_TRY_AGAIN;
		(*res_state->cb)(-1, res_state->cb_arg);
		free(res_state);
		return;
	}

	switch (_resp->dr_errno) {
	case DNSRES_NO_DATA:
		res_state->got_nodata++;
		/* FALLTHROUGH */
	case DNSRES_HOST_NOT_FOUND:
		/* keep trying */
		break;
	case DNSRES_TRY_AGAIN: {
		DNSRES_HEADER *hp = (DNSRES_HEADER *) res_state->target->answer;
		if (hp->rcode == DNSRES_SERVFAIL) {
			/* try next search element, if any */
			res_state->got_servfail++;
			break;
		}
		/* FALLTHROUGH */
	}
	default:
		/* anything else implies that we're done */
		res_state->done++;
	}

	/* if we got here for some reason other than DNSRCH,
	 * we only wanted one iteration of the loop, so stop.
	 */
	if (!(_resp->options & RES_DNSRCH))
		res_state->done++;

	/* Continue execution of the loop - termination is handled there */
	res_search_domain_loop(res_state);
}

void
res_search_almostbottom(struct res_search_state *res_state)
{
	/* if we have not already tried the name "as is", do that now.
	 * note that we do this regardless of how many dots were in the
	 * name or whether it ends with a dot.
	 */
	if (!res_state->tried_as_is) {
		struct dnsres_target *target = res_state->target;
		res_state->res_conditional_cb = res_search_bottom;
		res_state->dont_save_errno = 1;

		/* BLOCKING */
		res_querydomain(res_state->_resp,
		    res_state->name, NULL, target,
		    res_search_cb_eval, res_state);
		return;
	}

	res_search_bottom(res_state);
}

void
res_search_bottom(struct res_search_state *res_state)
{
	struct dnsres *_resp = res_state->_resp;

	/* if we got here, we didn't satisfy the search.
	 * if we did an initial full query, return that query's dr_errno
	 * (note that we wouldn't be here if that query had succeeded).
	 * else if we ever got a nodata, send that back as the reason.
	 * else send back meaningless dr_errno, that being the one from
	 * the last DNSRCH we did.
	 */
	if (res_state->saved_herrno != -1)
		_resp->dr_errno = res_state->saved_herrno;
	else if (res_state->got_nodata)
		_resp->dr_errno = DNSRES_NO_DATA;
	else if (res_state->got_servfail)
		_resp->dr_errno = DNSRES_TRY_AGAIN;

	(*res_state->cb)(-1, res_state->cb_arg);
	free(res_state);
}

/*
 * Perform a call on res_query on the concatenation of name and domain,
 * removing a trailing dot from name if domain is NULL.
 */
void
res_querydomain(
	struct dnsres *_resp,
	const char *name,
	const char *domain,
	struct dnsres_target *q,
	void (*cb)(int, void *),
	void *cb_arg
    )
{
	char nbuf[DNSRES_MAXDNAME*2+1+1];
	const char *longname = nbuf;
	int n;

#ifdef DEBUG
	if (_resp->options & RES_DEBUG)
		printf(";; res_querydomain(%s, %s, %d, %d)\n",
		       name, domain?domain:"<Nil>", class, type);
#endif
	if (domain == NULL) {
		/*
		 * Check for trailing '.';
		 * copy without '.' if present.
		 */
		n = strlen(name) - 1;
		if (n != (0 - 1) && name[n] == '.' && n < sizeof(nbuf) - 1) {
			bcopy(name, nbuf, n);
			nbuf[n] = '\0';
		} else
			longname = name;
	} else
		snprintf(nbuf, sizeof nbuf, "%.*s.%.*s",
		    DNSRES_MAXDNAME, name, DNSRES_MAXDNAME, domain);

	/* BLOCKING */
	res_query(_resp, longname, q, cb, cb_arg);
}

const char *
hostalias(struct dnsres* _resp, const char *name)
{
	unsigned char *cp1, *cp2;
	FILE *fp;
	char *file;
	char buf[BUFSIZ];
	static char abuf[DNSRES_MAXDNAME];
	size_t len;

	if (_resp->options & RES_NOALIASES)
		return (NULL);
	file = getenv("HOSTALIASES");
	if (issetugid() != 0 || file == NULL || (fp = fopen(file, "r")) == NULL)
		return (NULL);
	setbuf(fp, NULL);
	while ((cp1 = fgetln(fp, &len)) != NULL) {
		if (cp1[len-1] == '\n')
			len--;
		if (len >= sizeof(buf) || len == 0)
			continue;
		(void)memcpy(buf, cp1, len);
		buf[len] = '\0';
		
		for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
			;
		if (!*cp1)
			break;
		*cp1 = '\0';
		if (!strcasecmp(buf, name)) {
			while (isspace(*++cp1))
				;
			if (!*cp1)
				break;
			for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
				;
			*cp2 = '\0';
			strlcpy(abuf, cp1, sizeof(abuf));
			fclose(fp);
			return (abuf);
		}
	}
	fclose(fp);
	return (NULL);
}