This commit was generated by cvs2svn to compensate for changes in r2,

which included commits to RCS files with non-trunk default branches.

1 files changed, 699 insertions, 0 deletions

diff --git a/adns-0.6/src/event.c b/adns-0.6/src/event.c
new file mode 100644
index 0000000..a1641c6
--- /dev/null
+++ b/adns-0.6/src/event.c
@@ -0,0 +1,699 @@
+/*
+ * event.c
+ * - event loop core
+ * - TCP connection management
+ * - user-visible check/wait and event-loop-related functions
+ */
+/*
+ *  This file is
+ *    Copyright (C) 1997-1999 Ian Jackson <ian@davenant.greenend.org.uk>
+ *
+ *  It is part of adns, which is
+ *    Copyright (C) 1997-1999 Ian Jackson <ian@davenant.greenend.org.uk>
+ *    Copyright (C) 1999 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;
+  
+  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);
+
+  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_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) {
+	tvbuf->tv_sec= 0;
+	tvbuf->tv_usec= 0;
+	*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:
+      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;
+      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 (!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();
+    }
+  }
+}
+
+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:
+    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_connecting:
+    break;
+  case server_ok:
+    if (fd != ads->tcpsocket) break;
+    assert(!ads->tcprecv_skip);
+    for (;;) {
+      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");
+	r= 0; goto xit;
+      }
+    } /* never reached */
+  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 %d)", udpaddrlen,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:
+    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 (!(ads->tcpsend.used && fd == ads->tcpsocket)) break;
+    for (;;) {
+      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);
+      }
+    } /* not reached */
+  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:
+    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) goto xit;
+    adns__timeouts(ads, 1, 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;
+
+xit:
+  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:
+    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;
+  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);
+    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;
+}