/* NeoStats - IRC Statistical Services 
** Copyright (c) 1999-2004 Adam Rutter, Justin Hammond
** http://www.neostats.net/
**
**  This program is free software; you can redistribute it and/or modify
**  it under the terms of the GNU General Public License as published by
**  the Free Software Foundation; either version 2 of the License, or
**  (at your option) any later version.
**
**  This program is distributed in the hope that it will be useful,
**  but WITHOUT ANY WARRANTY; without even the implied warranty of
**  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
**  GNU General Public License for more details.
**
**  You should have received a copy of the GNU General Public License
**  along with this program; if not, write to the Free Software
**  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
**  USA
**
** NeoStats CVS Identification
** $Id: event.c 1241 2004-01-14 11:36:37Z Fish $
*/
/*
 * event.c
 * - event loop core
 * - TCP connection management
 * - user-visible check/wait and event-loop-related functions
 */
/*
 *  This file is
 *    Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
 *
 *  It is part of adns, which is
 *    Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
 *    Copyright (C) 1999-2000 Tony Finch <dot@dotat.at>
 *  
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software Foundation,
 *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 
 */

#include <errno.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/time.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "internal.h"
#include "tvarith.h"

/* TCP connection management. */

static void tcp_close(adns_state ads)
{
	int serv;

	serv = ads->tcpserver;
	close(ads->tcpsocket);
	ads->tcpsocket = -1;
	ads->tcprecv.used = ads->tcprecv_skip = ads->tcpsend.used = 0;
}

void adns__tcp_broken(adns_state ads, const char *what, const char *why)
{
	int serv;
	adns_query qu;

	assert(ads->tcpstate == server_connecting
	       || ads->tcpstate == server_ok);
	serv = ads->tcpserver;
	if (what)
		adns__warn(ads, serv, 0, "TCP connection failed: %s: %s",
			   what, why);

	if (ads->tcpstate == server_connecting) {
		/* Counts as a retry for all the queries waiting for TCP. */
		for (qu = ads->tcpw.head; qu; qu = qu->next)
			qu->retries++;
	}

	tcp_close(ads);
	ads->tcpstate = server_broken;
	ads->tcpserver = (serv + 1) % ads->nservers;
}

static void tcp_connected(adns_state ads, struct timeval now)
{
	adns_query qu, nqu;

	adns__debug(ads, ads->tcpserver, 0, "TCP connected");
	ads->tcpstate = server_ok;
	for (qu = ads->tcpw.head; qu && ads->tcpstate == server_ok;
	     qu = nqu) {
		nqu = qu->next;
		assert(qu->state == query_tcpw);
		adns__querysend_tcp(qu, now);
	}
}

void adns__tcp_tryconnect(adns_state ads, struct timeval now)
{
	int r, fd, tries;
	struct sockaddr_in addr;
	struct protoent *proto;

	for (tries = 0; tries < ads->nservers; tries++) {
		switch (ads->tcpstate) {
		case server_connecting:
		case server_ok:
		case server_broken:
			return;
		case server_disconnected:
			break;
		default:
			abort();
		}

		assert(!ads->tcpsend.used);
		assert(!ads->tcprecv.used);
		assert(!ads->tcprecv_skip);

		proto = getprotobyname("tcp");
		if (!proto) {
			adns__diag(ads, -1, 0,
				   "unable to find protocol no. for TCP !");
			return;
		}
		fd = socket(AF_INET, SOCK_STREAM, proto->p_proto);
		if (fd < 0) {
			adns__diag(ads, -1, 0,
				   "cannot create TCP socket: %s",
				   strerror(errno));
			return;
		}
		r = adns__setnonblock(ads, fd);
		if (r) {
			adns__diag(ads, -1, 0,
				   "cannot make TCP socket nonblocking: %s",
				   strerror(r));
			close(fd);
			return;
		}
		memset(&addr, 0, sizeof(addr));
		addr.sin_family = AF_INET;
		addr.sin_port = htons(DNS_PORT);
		addr.sin_addr = ads->servers[ads->tcpserver].addr;
		r = connect(fd, (const struct sockaddr *) &addr,
			    sizeof(addr));
		ads->tcpsocket = fd;
		ads->tcpstate = server_connecting;
		if (r == 0) {
			tcp_connected(ads, now);
			return;
		}
		if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
			ads->tcptimeout = now;
			timevaladd(&ads->tcptimeout, TCPCONNMS);
			return;
		}
		adns__tcp_broken(ads, "connect", strerror(errno));
		ads->tcpstate = server_disconnected;
	}
}

/* Timeout handling functions. */

void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
			     struct timeval *tv_buf)
{
	const struct timeval *now;
	int r;

	now = *now_io;
	if (now)
		return;
	r = gettimeofday(tv_buf, 0);
	if (!r) {
		*now_io = tv_buf;
		return;
	}
	adns__diag(ads, -1, 0, "gettimeofday failed: %s", strerror(errno));
	adns_globalsystemfailure(ads);
	return;
}

static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf)
{
	struct timeval *rbuf;

	if (!tv_io)
		return;

	rbuf = *tv_io;
	if (!rbuf) {
		*tv_io = rbuf = tvbuf;
	}

	timerclear(rbuf);
}

static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
			struct timeval maxto)
{
	struct timeval *rbuf;

	if (!tv_io)
		return;
	rbuf = *tv_io;
	if (!rbuf) {
		*tvbuf = maxto;
		*tv_io = tvbuf;
	} else {
		if (timercmp(rbuf, &maxto, >))
			*rbuf = maxto;
	}
/*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
	maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
}

static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
			   struct timeval now, struct timeval maxtime)
{
	/* tv_io may be 0 */
	ldiv_t dr;

/*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
	now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
	if (!tv_io)
		return;
	maxtime.tv_sec -= (now.tv_sec + 2);
	maxtime.tv_usec -= (now.tv_usec - 2000000);
	dr = ldiv(maxtime.tv_usec, 1000000);
	maxtime.tv_sec += dr.quot;
	maxtime.tv_usec -= dr.quot * 1000000;
	if (maxtime.tv_sec < 0)
		timerclear(&maxtime);
	inter_maxto(tv_io, tvbuf, maxtime);
}

static void timeouts_queue(adns_state ads, int act,
			   struct timeval **tv_io, struct timeval *tvbuf,
			   struct timeval now, struct query_queue *queue)
{
	adns_query qu, nqu;

	for (qu = queue->head; qu; qu = nqu) {
		nqu = qu->next;
		if (!timercmp(&now, &qu->timeout, >)) {
			inter_maxtoabs(tv_io, tvbuf, now, qu->timeout);
		} else {
			if (!act) {
				inter_immed(tv_io, tvbuf);
				return;
			}
			LIST_UNLINK(*queue, qu);
			if (qu->state != query_tosend) {
				adns__query_fail(qu, adns_s_timeout);
			} else {
				adns__query_send(qu, now);
			}
			nqu = queue->head;
		}
	}
}

static void tcp_events(adns_state ads, int act,
		       struct timeval **tv_io, struct timeval *tvbuf,
		       struct timeval now)
{
	adns_query qu, nqu;

	for (;;) {
		switch (ads->tcpstate) {
		case server_broken:
			if (!act) {
				inter_immed(tv_io, tvbuf);
				return;
			}
			for (qu = ads->tcpw.head; qu; qu = nqu) {
				nqu = qu->next;
				assert(qu->state == query_tcpw);
				if (qu->retries > ads->nservers) {
					LIST_UNLINK(ads->tcpw, qu);
					adns__query_fail(qu,
							 adns_s_allservfail);
				}
			}
			ads->tcpstate = server_disconnected;
		case server_disconnected:	/* fall through */
			if (!ads->tcpw.head)
				return;
			if (!act) {
				inter_immed(tv_io, tvbuf);
				return;
			}
			adns__tcp_tryconnect(ads, now);
			break;
		case server_ok:
			if (ads->tcpw.head)
				return;
			if (!ads->tcptimeout.tv_sec) {
				assert(!ads->tcptimeout.tv_usec);
				ads->tcptimeout = now;
				timevaladd(&ads->tcptimeout, TCPIDLEMS);
			}
		case server_connecting:	/* fall through */
			if (!act || !timercmp(&now, &ads->tcptimeout, >)) {
				inter_maxtoabs(tv_io, tvbuf, now,
					       ads->tcptimeout);
				return;
			}
			{
				/* TCP timeout has happened */
				switch (ads->tcpstate) {
				case server_connecting:	/* failed to connect */
					adns__tcp_broken(ads,
							 "unable to make connection",
							 "timed out");
					break;
				case server_ok:	/* idle timeout */
					tcp_close(ads);
					ads->tcpstate =
					    server_disconnected;
					return;
				default:
					abort();
				}
			}
			break;
		default:
			abort();
		}
	}
	return;
}

void adns__timeouts(adns_state ads, int act,
		    struct timeval **tv_io, struct timeval *tvbuf,
		    struct timeval now)
{
	timeouts_queue(ads, act, tv_io, tvbuf, now, &ads->udpw);
	timeouts_queue(ads, act, tv_io, tvbuf, now, &ads->tcpw);
	tcp_events(ads, act, tv_io, tvbuf, now);
}

void adns_firsttimeout(adns_state ads,
		       struct timeval **tv_io, struct timeval *tvbuf,
		       struct timeval now)
{
	adns__consistency(ads, 0, cc_entex);
	adns__timeouts(ads, 0, tv_io, tvbuf, now);
	adns__consistency(ads, 0, cc_entex);
}

void adns_processtimeouts(adns_state ads, const struct timeval *now)
{
	struct timeval tv_buf;

	adns__consistency(ads, 0, cc_entex);
	adns__must_gettimeofday(ads, &now, &tv_buf);
	if (now)
		adns__timeouts(ads, 1, 0, 0, *now);
	adns__consistency(ads, 0, cc_entex);
}

/* fd handling functions.  These are the top-level of the real work of
 * reception and often transmission.
 */

int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS])
{
	/* Returns the number of entries filled in.  Always zeroes revents. */

	assert(MAX_POLLFDS == 2);

	pollfds_buf[0].fd = ads->udpsocket;
	pollfds_buf[0].events = POLLIN;
	pollfds_buf[0].revents = 0;

	switch (ads->tcpstate) {
	case server_disconnected:
	case server_broken:
		return 1;
	case server_connecting:
		pollfds_buf[1].events = POLLOUT;
		break;
	case server_ok:
		pollfds_buf[1].events =
		    ads->tcpsend.
		    used ? POLLIN | POLLOUT | POLLPRI : POLLIN | POLLPRI;
		break;
	default:
		abort();
	}
	pollfds_buf[1].fd = ads->tcpsocket;
	return 2;
}

int adns_processreadable(adns_state ads, int fd, const struct timeval *now)
{
	int want, dgramlen, r, udpaddrlen, serv, old_skip;
	byte udpbuf[DNS_MAXUDP];
	struct sockaddr_in udpaddr;

	adns__consistency(ads, 0, cc_entex);

	switch (ads->tcpstate) {
	case server_disconnected:
	case server_broken:
	case server_connecting:
		break;
	case server_ok:
		if (fd != ads->tcpsocket)
			break;
		assert(!ads->tcprecv_skip);
		do {
			if (ads->tcprecv.used >= ads->tcprecv_skip + 2) {
				dgramlen =
				    ((ads->tcprecv.
				      buf[ads->tcprecv_skip] << 8) | ads->
				     tcprecv.buf[ads->tcprecv_skip + 1]);
				if (ads->tcprecv.used >=
				    ads->tcprecv_skip + 2 + dgramlen) {
					old_skip = ads->tcprecv_skip;
					ads->tcprecv_skip += 2 + dgramlen;
					adns__procdgram(ads,
							ads->tcprecv.buf +
							old_skip + 2,
							dgramlen,
							ads->tcpserver, 1,
							*now);
					continue;
				} else {
					want = 2 + dgramlen;
				}
			} else {
				want = 2;
			}
			ads->tcprecv.used -= ads->tcprecv_skip;
			memmove(ads->tcprecv.buf,
				ads->tcprecv.buf + ads->tcprecv_skip,
				ads->tcprecv.used);
			ads->tcprecv_skip = 0;
			if (!adns__vbuf_ensure(&ads->tcprecv, want)) {
				r = ENOMEM;
				goto xit;
			}
			assert(ads->tcprecv.used <= ads->tcprecv.avail);
			if (ads->tcprecv.used == ads->tcprecv.avail)
				continue;
			r = read(ads->tcpsocket,
				 ads->tcprecv.buf + ads->tcprecv.used,
				 ads->tcprecv.avail - ads->tcprecv.used);
			if (r > 0) {
				ads->tcprecv.used += r;
			} else {
				if (r) {
					if (errno == EAGAIN
					    || errno == EWOULDBLOCK) {
						r = 0;
						goto xit;
					}
					if (errno == EINTR)
						continue;
					if (errno_resources(errno)) {
						r = errno;
						goto xit;
					}
				}
				adns__tcp_broken(ads, "read",
						 r ? strerror(errno) :
						 "closed");
			}
		} while (ads->tcpstate == server_ok);
		r = 0;
		goto xit;
	default:
		abort();
	}
	if (fd == ads->udpsocket) {
		for (;;) {
			udpaddrlen = sizeof(udpaddr);
			r = recvfrom(ads->udpsocket, udpbuf,
				     sizeof(udpbuf), 0,
				     (struct sockaddr *) &udpaddr,
				     &udpaddrlen);
			if (r < 0) {
				if (errno == EAGAIN
				    || errno == EWOULDBLOCK) {
					r = 0;
					goto xit;
				}
				if (errno == EINTR)
					continue;
				if (errno_resources(errno)) {
					r = errno;
					goto xit;
				}
				adns__warn(ads, -1, 0,
					   "datagram receive error: %s",
					   strerror(errno));
				r = 0;
				goto xit;
			}
			if (udpaddrlen != sizeof(udpaddr)) {
				adns__diag(ads, -1, 0,
					   "datagram received with wrong address length %d"
					   " (expected %lu)", udpaddrlen,
					   (unsigned long)
					   sizeof(udpaddr));
				continue;
			}
			if (udpaddr.sin_family != AF_INET) {
				adns__diag(ads, -1, 0,
					   "datagram received with wrong protocol family"
					   " %u (expected %u)",
					   udpaddr.sin_family, AF_INET);
				continue;
			}
			if (ntohs(udpaddr.sin_port) != DNS_PORT) {
				adns__diag(ads, -1, 0,
					   "datagram received from wrong port %u (expected %u)",
					   ntohs(udpaddr.sin_port),
					   DNS_PORT);
				continue;
			}
			for (serv = 0;
			     serv < ads->nservers &&
			     ads->servers[serv].addr.s_addr !=
			     udpaddr.sin_addr.s_addr; serv++);
			if (serv >= ads->nservers) {
				adns__warn(ads, -1, 0,
					   "datagram received from unknown nameserver %s",
					   inet_ntoa(udpaddr.sin_addr));
				continue;
			}
			adns__procdgram(ads, udpbuf, r, serv, 0, *now);
		}
	}
	r = 0;
      xit:
	adns__consistency(ads, 0, cc_entex);
	return r;
}

int adns_processwriteable(adns_state ads, int fd,
			  const struct timeval *now)
{
	int r;

	adns__consistency(ads, 0, cc_entex);

	switch (ads->tcpstate) {
	case server_disconnected:
	case server_broken:
		break;
	case server_connecting:
		if (fd != ads->tcpsocket)
			break;
		assert(ads->tcprecv.used == 0);
		assert(ads->tcprecv_skip == 0);
		for (;;) {
			if (!adns__vbuf_ensure(&ads->tcprecv, 1)) {
				r = ENOMEM;
				goto xit;
			}
			r = read(ads->tcpsocket, &ads->tcprecv.buf, 1);
			if (r == 0
			    || (r < 0
				&& (errno == EAGAIN
				    || errno == EWOULDBLOCK))) {
				tcp_connected(ads, *now);
				r = 0;
				goto xit;
			}
			if (r > 0) {
				adns__tcp_broken(ads, "connect/read",
						 "sent data before first request");
				r = 0;
				goto xit;
			}
			if (errno == EINTR)
				continue;
			if (errno_resources(errno)) {
				r = errno;
				goto xit;
			}
			adns__tcp_broken(ads, "connect/read",
					 strerror(errno));
			r = 0;
			goto xit;
		}		/* not reached */
	case server_ok:
		if (fd != ads->tcpsocket)
			break;
		while (ads->tcpsend.used) {
			adns__sigpipe_protect(ads);
			r = write(ads->tcpsocket, ads->tcpsend.buf,
				  ads->tcpsend.used);
			adns__sigpipe_unprotect(ads);
			if (r < 0) {
				if (errno == EINTR)
					continue;
				if (errno == EAGAIN
				    || errno == EWOULDBLOCK) {
					r = 0;
					goto xit;
				}
				if (errno_resources(errno)) {
					r = errno;
					goto xit;
				}
				adns__tcp_broken(ads, "write",
						 strerror(errno));
				r = 0;
				goto xit;
			} else if (r > 0) {
				ads->tcpsend.used -= r;
				memmove(ads->tcpsend.buf,
					ads->tcpsend.buf + r,
					ads->tcpsend.used);
			}
		}
		r = 0;
		goto xit;
	default:
		abort();
	}
	r = 0;
      xit:
	adns__consistency(ads, 0, cc_entex);
	return r;
}

int adns_processexceptional(adns_state ads, int fd,
			    const struct timeval *now)
{
	adns__consistency(ads, 0, cc_entex);
	switch (ads->tcpstate) {
	case server_disconnected:
	case server_broken:
		break;
	case server_connecting:
	case server_ok:
		if (fd != ads->tcpsocket)
			break;
		adns__tcp_broken(ads, "poll/select",
				 "exceptional condition detected");
		break;
	default:
		abort();
	}
	adns__consistency(ads, 0, cc_entex);
	return 0;
}

static void fd_event(adns_state ads, int fd,
		     int revent, int pollflag,
		     int maxfd, const fd_set * fds,
		     int (*func) (adns_state, int fd,
				  const struct timeval * now),
		     struct timeval now, int *r_r)
{
	int r;

	if (!(revent & pollflag))
		return;
	if (fds && !(fd < maxfd && FD_ISSET(fd, fds)))
		return;
	r = func(ads, fd, &now);
	if (r) {
		if (r_r) {
			*r_r = r;
		} else {
			adns__diag(ads, -1, 0,
				   "process fd failed after select: %s",
				   strerror(errno));
			adns_globalsystemfailure(ads);
		}
	}
}

void adns__fdevents(adns_state ads,
		    const struct pollfd *pollfds, int npollfds,
		    int maxfd, const fd_set * readfds,
		    const fd_set * writefds, const fd_set * exceptfds,
		    struct timeval now, int *r_r)
{
	int i, fd, revents;

	for (i = 0; i < npollfds; i++) {
		fd = pollfds[i].fd;
		if (fd >= maxfd)
			maxfd = fd + 1;
		revents = pollfds[i].revents;
		fd_event(ads, fd, revents, POLLIN, maxfd, readfds,
			 adns_processreadable, now, r_r);
		fd_event(ads, fd, revents, POLLOUT, maxfd, writefds,
			 adns_processwriteable, now, r_r);
		fd_event(ads, fd, revents, POLLPRI, maxfd, exceptfds,
			 adns_processexceptional, now, r_r);
	}
}

/* Wrappers for select(2). */

void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set * readfds_io,
		       fd_set * writefds_io, fd_set * exceptfds_io,
		       struct timeval **tv_mod, struct timeval *tv_tobuf,
		       const struct timeval *now)
{
	struct timeval tv_nowbuf;
	struct pollfd pollfds[MAX_POLLFDS];
	int i, fd, maxfd, npollfds;

	adns__consistency(ads, 0, cc_entex);

	if (tv_mod
	    && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
		/* The caller is planning to sleep. */
		adns__must_gettimeofday(ads, &now, &tv_nowbuf);
		if (!now) {
			inter_immed(tv_mod, tv_tobuf);
			adns__consistency(ads, 0, cc_entex);
			return;
#if 0
			goto xit;
#endif
		}
		adns__timeouts(ads, 0, tv_mod, tv_tobuf, *now);
	}

	npollfds = adns__pollfds(ads, pollfds);
	maxfd = *maxfd_io;
	for (i = 0; i < npollfds; i++) {
		fd = pollfds[i].fd;
		if (fd >= maxfd)
			maxfd = fd + 1;
		if (pollfds[i].events & POLLIN)
			FD_SET(fd, readfds_io);
		if (pollfds[i].events & POLLOUT)
			FD_SET(fd, writefds_io);
		if (pollfds[i].events & POLLPRI)
			FD_SET(fd, exceptfds_io);
	}
	*maxfd_io = maxfd;
#if 0
      xit:
#endif
	adns__consistency(ads, 0, cc_entex);
}

void adns_afterselect(adns_state ads, int maxfd, const fd_set * readfds,
		      const fd_set * writefds, const fd_set * exceptfds,
		      const struct timeval *now)
{
	struct timeval tv_buf;
	struct pollfd pollfds[MAX_POLLFDS];
	int npollfds, i;

	adns__consistency(ads, 0, cc_entex);
	adns__must_gettimeofday(ads, &now, &tv_buf);
	if (!now)
		goto xit;
	adns_processtimeouts(ads, now);

	npollfds = adns__pollfds(ads, pollfds);
	for (i = 0; i < npollfds; i++)
		pollfds[i].revents = POLLIN | POLLOUT | POLLPRI;
	adns__fdevents(ads,
		       pollfds, npollfds,
		       maxfd, readfds, writefds, exceptfds, *now, 0);
      xit:
	adns__consistency(ads, 0, cc_entex);
}

/* General helpful functions. */

void adns_globalsystemfailure(adns_state ads)
{
	adns__consistency(ads, 0, cc_entex);

	while (ads->udpw.head)
		adns__query_fail(ads->udpw.head, adns_s_systemfail);
	while (ads->tcpw.head)
		adns__query_fail(ads->tcpw.head, adns_s_systemfail);

	switch (ads->tcpstate) {
	case server_connecting:
	case server_ok:
		adns__tcp_broken(ads, 0, 0);
		break;
	case server_disconnected:
	case server_broken:
		break;
	default:
		abort();
	}
	adns__consistency(ads, 0, cc_entex);
}

int adns_processany(adns_state ads)
{
	int r, i;
	struct timeval now;
	struct pollfd pollfds[MAX_POLLFDS];
	int npollfds;

	adns__consistency(ads, 0, cc_entex);

	r = gettimeofday(&now, 0);
	if (!r)
		adns_processtimeouts(ads, &now);

	/* We just use adns__fdevents to loop over the fd's trying them.
	 * This seems more sensible than calling select, since we're most
	 * likely just to want to do a read on one or two fds anyway.
	 */
	npollfds = adns__pollfds(ads, pollfds);
	for (i = 0; i < npollfds; i++)
		pollfds[i].revents = pollfds[i].events & ~POLLPRI;
	adns__fdevents(ads, pollfds, npollfds, 0, 0, 0, 0, now, &r);

	adns__consistency(ads, 0, cc_entex);
	return 0;
}

void adns__autosys(adns_state ads, struct timeval now)
{
	if (ads->iflags & adns_if_noautosys)
		return;
	adns_processany(ads);
}

int adns__internal_check(adns_state ads,
			 adns_query * query_io,
			 adns_answer ** answer, void **context_r)
{
	adns_query qu;

	qu = *query_io;
	if (!qu) {
		if (ads->output.head) {
			qu = ads->output.head;
		} else if (ads->udpw.head || ads->tcpw.head) {
			return EAGAIN;
		} else {
			return ESRCH;
		}
	} else {
		if (qu->id >= 0)
			return EAGAIN;
	}
	LIST_UNLINK(ads->output, qu);
	*answer = qu->answer;
	if (context_r)
		*context_r = qu->ctx.ext;
	*query_io = qu;
	free(qu);
	return 0;
}

int adns_wait(adns_state ads,
	      adns_query * query_io,
	      adns_answer ** answer_r, void **context_r)
{
	int r, maxfd, rsel;
	fd_set readfds, writefds, exceptfds;
	struct timeval tvbuf, *tvp;

	adns__consistency(ads, *query_io, cc_entex);
	for (;;) {
		r = adns__internal_check(ads, query_io, answer_r,
					 context_r);
		if (r != EAGAIN)
			break;
		maxfd = 0;
		tvp = 0;
		FD_ZERO(&readfds);
		FD_ZERO(&writefds);
		FD_ZERO(&exceptfds);
		adns_beforeselect(ads, &maxfd, &readfds, &writefds,
				  &exceptfds, &tvp, &tvbuf, 0);
		assert(tvp);
		rsel = select(maxfd, &readfds, &writefds, &exceptfds, tvp);
		if (rsel == -1) {
			if (errno == EINTR) {
				if (ads->iflags & adns_if_eintr) {
					r = EINTR;
					break;
				}
			} else {
				adns__diag(ads, -1, 0,
					   "select failed in wait: %s",
					   strerror(errno));
				adns_globalsystemfailure(ads);
			}
		} else {
			assert(rsel >= 0);
			adns_afterselect(ads, maxfd, &readfds, &writefds,
					 &exceptfds, 0);
		}
	}
	adns__consistency(ads, 0, cc_entex);
	return r;
}

int adns_check(adns_state ads,
	       adns_query * query_io,
	       adns_answer ** answer_r, void **context_r)
{
	struct timeval now;
	int r;

	adns__consistency(ads, *query_io, cc_entex);
	r = gettimeofday(&now, 0);
	if (!r)
		adns__autosys(ads, now);

	r = adns__internal_check(ads, query_io, answer_r, context_r);
	adns__consistency(ads, 0, cc_entex);
	return r;
}
