mdw@git.distorted.org.uk Git - adns/blob - src/event.c

   1 /*
   2  * event.c
   3  * - event loop core
   4  * - TCP connection management
   5  * - user-visible check/wait and event-loop-related functions
   6  */
   7 /*
   8  *  This file is
   9  *    Copyright (C) 1997-1999 Ian Jackson <ian@davenant.greenend.org.uk>
  10  *
  11  *  It is part of adns, which is
  12  *    Copyright (C) 1997-1999 Ian Jackson <ian@davenant.greenend.org.uk>
  13  *    Copyright (C) 1999 Tony Finch <dot@dotat.at>
  14  *
  15  *  This program is free software; you can redistribute it and/or modify
  16  *  it under the terms of the GNU General Public License as published by
  17  *  the Free Software Foundation; either version 2, or (at your option)
  18  *  any later version.
  19  *
  20  *  This program is distributed in the hope that it will be useful,
  21  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23  *  GNU General Public License for more details.
  24  *
  25  *  You should have received a copy of the GNU General Public License
  26  *  along with this program; if not, write to the Free Software Foundation,
  27  *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  28  */
  29
  30 #include <errno.h>
  31 #include <stdlib.h>
  32 #include <unistd.h>
  33
  34 #include <sys/types.h>
  35 #include <sys/time.h>
  36 #include <netdb.h>
  37 #include <sys/socket.h>
  38 #include <netinet/in.h>
  39 #include <arpa/inet.h>
  40
  41 #include "internal.h"
  42
  43 /* TCP connection management. */
  44
  45 static void tcp_close(adns_state ads) {
  46   int serv;
  47
  48   serv= ads->tcpserver;
  49   close(ads->tcpsocket);
  50   ads->tcpsocket= -1;
  51   ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
  52 }
  53
  54 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  55   int serv;
  56
  57   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  58   serv= ads->tcpserver;
  59   if (what) adns__warn(ads,serv,0,"TCP connection failed: %s: %s",what,why);
  60
  61   tcp_close(ads);
  62   ads->tcpstate= server_broken;
  63   ads->tcpserver= (serv+1)%ads->nservers;
  64 }
  65
  66 static void tcp_connected(adns_state ads, struct timeval now) {
  67   adns_query qu, nqu;
  68
  69   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  70   ads->tcpstate= server_ok;
  71   for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
  72     nqu= qu->next;
  73     assert(qu->state == query_tcpw);
  74     adns__querysend_tcp(qu,now);
  75   }
  76 }
  77
  78 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  79   int r, fd, tries;
  80   struct sockaddr_in addr;
  81   struct protoent *proto;
  82
  83   for (tries=0; tries<ads->nservers; tries++) {
  84     switch (ads->tcpstate) {
  85     case server_connecting:
  86     case server_ok:
  87     case server_broken:
  88       return;
  89     case server_disconnected:
  90       break;
  91     default:
  92       abort();
  93     }
  94
  95     assert(!ads->tcpsend.used);
  96     assert(!ads->tcprecv.used);
  97     assert(!ads->tcprecv_skip);
  98
  99     proto= getprotobyname("tcp");
 100     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
 101     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 102     if (fd<0) {
 103       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 104       return;
 105     }
 106     r= adns__setnonblock(ads,fd);
 107     if (r) {
 108       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
 109       close(fd);
 110       return;
 111     }
 112     memset(&addr,0,sizeof(addr));
 113     addr.sin_family= AF_INET;
 114     addr.sin_port= htons(DNS_PORT);
 115     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 116     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 117     ads->tcpsocket= fd;
 118     ads->tcpstate= server_connecting;
 119     if (r==0) { tcp_connected(ads,now); return; }
 120     if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
 121       ads->tcptimeout= now;
 122       timevaladd(&ads->tcptimeout,TCPCONNMS);
 123       return;
 124     }
 125     adns__tcp_broken(ads,"connect",strerror(errno));
 126     ads->tcpstate= server_disconnected;
 127   }
 128 }
 129
 130 /* Timeout handling functions. */
 131
 132 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 133                              struct timeval *tv_buf) {
 134   const struct timeval *now;
 135   int r;
 136
 137   now= *now_io;
 138   if (now) return;
 139   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 140   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 141   adns_globalsystemfailure(ads);
 142   return;
 143 }
 144
 145 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 146                         struct timeval maxto) {
 147   struct timeval *rbuf;
 148
 149   if (!tv_io) return;
 150   rbuf= *tv_io;
 151   if (!rbuf) {
 152     *tvbuf= maxto; *tv_io= tvbuf;
 153   } else {
 154     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 155   }
 156 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 157         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 158 }
 159
 160 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 161                            struct timeval now, struct timeval maxtime) {
 162   /* tv_io may be 0 */
 163   ldiv_t dr;
 164
 165 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 166         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 167   if (!tv_io) return;
 168   maxtime.tv_sec -= (now.tv_sec+2);
 169   maxtime.tv_usec -= (now.tv_usec-2000000);
 170   dr= ldiv(maxtime.tv_usec,1000000);
 171   maxtime.tv_sec += dr.quot;
 172   maxtime.tv_usec -= dr.quot*1000000;
 173   if (maxtime.tv_sec<0) timerclear(&maxtime);
 174   inter_maxto(tv_io,tvbuf,maxtime);
 175 }
 176
 177 static void timeouts_queue(adns_state ads, int act,
 178                            struct timeval **tv_io, struct timeval *tvbuf,
 179                            struct timeval now, struct query_queue *queue) {
 180   adns_query qu, nqu;
 181
 182   for (qu= queue->head; qu; qu= nqu) {
 183     nqu= qu->next;
 184     if (!timercmp(&now,&qu->timeout,>)) {
 185       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 186     } else {
 187       if (!act) {
 188         tvbuf->tv_sec= 0;
 189         tvbuf->tv_usec= 0;
 190         *tv_io= tvbuf;
 191         return;
 192       }
 193       LIST_UNLINK(*queue,qu);
 194       if (qu->state != query_tosend) {
 195         adns__query_fail(qu,adns_s_timeout);
 196       } else {
 197         adns__query_send(qu,now);
 198       }
 199       nqu= queue->head;
 200     }
 201   }
 202 }
 203
 204 static void tcp_events(adns_state ads, int act,
 205                        struct timeval **tv_io, struct timeval *tvbuf,
 206                        struct timeval now) {
 207   adns_query qu, nqu;
 208
 209   for (;;) {
 210     switch (ads->tcpstate) {
 211     case server_broken:
 212       for (qu= ads->tcpw.head; qu; qu= nqu) {
 213         nqu= qu->next;
 214         assert(qu->state == query_tcpw);
 215         if (qu->retries > ads->nservers) {
 216           LIST_UNLINK(ads->tcpw,qu);
 217           adns__query_fail(qu,adns_s_allservfail);
 218         }
 219       }
 220       ads->tcpstate= server_disconnected;
 221     case server_disconnected: /* fall through */
 222       if (!ads->tcpw.head) return;
 223       adns__tcp_tryconnect(ads,now);
 224       break;
 225     case server_ok:
 226       if (ads->tcpw.head) return;
 227       if (!ads->tcptimeout.tv_sec) {
 228         assert(!ads->tcptimeout.tv_usec);
 229         ads->tcptimeout= now;
 230         timevaladd(&ads->tcptimeout,TCPIDLEMS);
 231       }
 232     case server_connecting: /* fall through */
 233       if (!timercmp(&now,&ads->tcptimeout,>)) {
 234         inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
 235         return;
 236       } {
 237         /* TCP timeout has happened */
 238         switch (ads->tcpstate) {
 239         case server_connecting: /* failed to connect */
 240           adns__tcp_broken(ads,"unable to make connection","timed out");
 241           break;
 242         case server_ok: /* idle timeout */
 243           tcp_close(ads);
 244           ads->tcpstate= server_disconnected;
 245           return;
 246         default:
 247           abort();
 248         }
 249       }
 250       break;
 251     default:
 252       abort();
 253     }
 254   }
 255 }
 256
 257 void adns__timeouts(adns_state ads, int act,
 258                     struct timeval **tv_io, struct timeval *tvbuf,
 259                     struct timeval now) {
 260   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
 261   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
 262   tcp_events(ads,act,tv_io,tvbuf,now);
 263 }
 264
 265 void adns_firsttimeout(adns_state ads,
 266                        struct timeval **tv_io, struct timeval *tvbuf,
 267                        struct timeval now) {
 268   adns__consistency(ads,0,cc_entex);
 269   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 270   adns__consistency(ads,0,cc_entex);
 271 }
 272
 273 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 274   struct timeval tv_buf;
 275
 276   adns__consistency(ads,0,cc_entex);
 277   adns__must_gettimeofday(ads,&now,&tv_buf);
 278   if (now) adns__timeouts(ads, 1, 0,0, *now);
 279   adns__consistency(ads,0,cc_entex);
 280 }
 281
 282 /* fd handling functions.  These are the top-level of the real work of
 283  * reception and often transmission.
 284  */
 285
 286 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 287   /* Returns the number of entries filled in.  Always zeroes revents. */
 288
 289   assert(MAX_POLLFDS==2);
 290
 291   pollfds_buf[0].fd= ads->udpsocket;
 292   pollfds_buf[0].events= POLLIN;
 293   pollfds_buf[0].revents= 0;
 294
 295   switch (ads->tcpstate) {
 296   case server_disconnected:
 297     return 1;
 298   case server_connecting:
 299     pollfds_buf[1].events= POLLOUT;
 300     break;
 301   case server_ok:
 302     pollfds_buf[1].events= ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 303     break;
 304   default:
 305     abort();
 306   }
 307   pollfds_buf[1].fd= ads->tcpsocket;
 308   return 2;
 309 }
 310
 311 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 312   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 313   byte udpbuf[DNS_MAXUDP];
 314   struct sockaddr_in udpaddr;
 315
 316   adns__consistency(ads,0,cc_entex);
 317
 318   switch (ads->tcpstate) {
 319   case server_disconnected:
 320   case server_connecting:
 321     break;
 322   case server_ok:
 323     if (fd != ads->tcpsocket) break;
 324     assert(!ads->tcprecv_skip);
 325     for (;;) {
 326       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 327         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 328                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 329         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 330           old_skip= ads->tcprecv_skip;
 331           ads->tcprecv_skip += 2+dgramlen;
 332           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 333                           dgramlen, ads->tcpserver, 1,*now);
 334           continue;
 335         } else {
 336           want= 2+dgramlen;
 337         }
 338       } else {
 339         want= 2;
 340       }
 341       ads->tcprecv.used -= ads->tcprecv_skip;
 342       memmove(ads->tcprecv.buf,ads->tcprecv.buf+ads->tcprecv_skip,ads->tcprecv.used);
 343       ads->tcprecv_skip= 0;
 344       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 345       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 346       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 347       r= read(ads->tcpsocket,
 348               ads->tcprecv.buf+ads->tcprecv.used,
 349               ads->tcprecv.avail-ads->tcprecv.used);
 350       if (r>0) {
 351         ads->tcprecv.used+= r;
 352       } else {
 353         if (r) {
 354           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 355           if (errno==EINTR) continue;
 356           if (errno_resources(errno)) { r= errno; goto xit; }
 357         }
 358         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 359         r= 0; goto xit;
 360       }
 361     } /* never reached */
 362   default:
 363     abort();
 364   }
 365   if (fd == ads->udpsocket) {
 366     for (;;) {
 367       udpaddrlen= sizeof(udpaddr);
 368       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 369                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 370       if (r<0) {
 371         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 372         if (errno == EINTR) continue;
 373         if (errno_resources(errno)) { r= errno; goto xit; }
 374         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 375         r= 0; goto xit;
 376       }
 377       if (udpaddrlen != sizeof(udpaddr)) {
 378         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 379                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 380         continue;
 381       }
 382       if (udpaddr.sin_family != AF_INET) {
 383         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 384                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 385         continue;
 386       }
 387       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 388         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 389                    ntohs(udpaddr.sin_port),DNS_PORT);
 390         continue;
 391       }
 392       for (serv= 0;
 393            serv < ads->nservers &&
 394              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 395            serv++);
 396       if (serv >= ads->nservers) {
 397         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 398                    inet_ntoa(udpaddr.sin_addr));
 399         continue;
 400       }
 401       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 402     }
 403   }
 404   r= 0;
 405 xit:
 406   adns__consistency(ads,0,cc_entex);
 407   return r;
 408 }
 409
 410 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 411   int r;
 412
 413   adns__consistency(ads,0,cc_entex);
 414
 415   switch (ads->tcpstate) {
 416   case server_disconnected:
 417     break;
 418   case server_connecting:
 419     if (fd != ads->tcpsocket) break;
 420     assert(ads->tcprecv.used==0);
 421     assert(ads->tcprecv_skip==0);
 422     for (;;) {
 423       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 424       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 425       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 426         tcp_connected(ads,*now);
 427         r= 0; goto xit;
 428       }
 429       if (r>0) {
 430         adns__tcp_broken(ads,"connect/read","sent data before first request");
 431         r= 0; goto xit;
 432       }
 433       if (errno==EINTR) continue;
 434       if (errno_resources(errno)) { r= errno; goto xit; }
 435       adns__tcp_broken(ads,"connect/read",strerror(errno));
 436       r= 0; goto xit;
 437     } /* not reached */
 438   case server_ok:
 439     if (!(ads->tcpsend.used && fd == ads->tcpsocket)) break;
 440     for (;;) {
 441       adns__sigpipe_protect(ads);
 442       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 443       adns__sigpipe_unprotect(ads);
 444       if (r<0) {
 445         if (errno==EINTR) continue;
 446         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 447         if (errno_resources(errno)) { r= errno; goto xit; }
 448         adns__tcp_broken(ads,"write",strerror(errno));
 449         r= 0; goto xit;
 450       } else if (r>0) {
 451         ads->tcpsend.used -= r;
 452         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 453       }
 454     } /* not reached */
 455   default:
 456     abort();
 457   }
 458   r= 0;
 459 xit:
 460   adns__consistency(ads,0,cc_entex);
 461   return r;
 462 }
 463
 464 int adns_processexceptional(adns_state ads, int fd, const struct timeval *now) {
 465   adns__consistency(ads,0,cc_entex);
 466   switch (ads->tcpstate) {
 467   case server_disconnected:
 468     break;
 469   case server_connecting:
 470   case server_ok:
 471     if (fd != ads->tcpsocket) break;
 472     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 473     break;
 474   default:
 475     abort();
 476   }
 477   adns__consistency(ads,0,cc_entex);
 478   return 0;
 479 }
 480
 481 static void fd_event(adns_state ads, int fd,
 482                      int revent, int pollflag,
 483                      int maxfd, const fd_set *fds,
 484                      int (*func)(adns_state, int fd, const struct timeval *now),
 485                      struct timeval now, int *r_r) {
 486   int r;
 487
 488   if (!(revent & pollflag)) return;
 489   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 490   r= func(ads,fd,&now);
 491   if (r) {
 492     if (r_r) {
 493       *r_r= r;
 494     } else {
 495       adns__diag(ads,-1,0,"process fd failed after select: %s",strerror(errno));
 496       adns_globalsystemfailure(ads);
 497     }
 498   }
 499 }
 500
 501 void adns__fdevents(adns_state ads,
 502                     const struct pollfd *pollfds, int npollfds,
 503                     int maxfd, const fd_set *readfds,
 504                     const fd_set *writefds, const fd_set *exceptfds,
 505                     struct timeval now, int *r_r) {
 506   int i, fd, revents;
 507
 508   for (i=0; i<npollfds; i++) {
 509     fd= pollfds[i].fd;
 510     if (fd >= maxfd) maxfd= fd+1;
 511     revents= pollfds[i].revents;
 512     fd_event(ads,fd, revents,POLLIN, maxfd,readfds, adns_processreadable,now,r_r);
 513     fd_event(ads,fd, revents,POLLOUT, maxfd,writefds, adns_processwriteable,now,r_r);
 514     fd_event(ads,fd, revents,POLLPRI, maxfd,exceptfds, adns_processexceptional,now,r_r);
 515   }
 516 }
 517
 518 /* Wrappers for select(2). */
 519
 520 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 521                        fd_set *writefds_io, fd_set *exceptfds_io,
 522                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 523                        const struct timeval *now) {
 524   struct timeval tv_nowbuf;
 525   struct pollfd pollfds[MAX_POLLFDS];
 526   int i, fd, maxfd, npollfds;
 527
 528   adns__consistency(ads,0,cc_entex);
 529
 530   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 531     /* The caller is planning to sleep. */
 532     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 533     if (!now) goto xit;
 534     adns__timeouts(ads, 1, tv_mod,tv_tobuf, *now);
 535   }
 536
 537   npollfds= adns__pollfds(ads,pollfds);
 538   maxfd= *maxfd_io;
 539   for (i=0; i<npollfds; i++) {
 540     fd= pollfds[i].fd;
 541     if (fd >= maxfd) maxfd= fd+1;
 542     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 543     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 544     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 545   }
 546   *maxfd_io= maxfd;
 547
 548 xit:
 549   adns__consistency(ads,0,cc_entex);
 550 }
 551
 552 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 553                       const fd_set *writefds, const fd_set *exceptfds,
 554                       const struct timeval *now) {
 555   struct timeval tv_buf;
 556   struct pollfd pollfds[MAX_POLLFDS];
 557   int npollfds, i;
 558
 559   adns__consistency(ads,0,cc_entex);
 560   adns__must_gettimeofday(ads,&now,&tv_buf);
 561   if (!now) goto xit;
 562   adns_processtimeouts(ads,now);
 563
 564   npollfds= adns__pollfds(ads,pollfds);
 565   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 566   adns__fdevents(ads,
 567                  pollfds,npollfds,
 568                  maxfd,readfds,writefds,exceptfds,
 569                  *now, 0);
 570 xit:
 571   adns__consistency(ads,0,cc_entex);
 572 }
 573
 574 /* General helpful functions. */
 575
 576 void adns_globalsystemfailure(adns_state ads) {
 577   adns__consistency(ads,0,cc_entex);
 578
 579   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 580   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 581
 582   switch (ads->tcpstate) {
 583   case server_connecting:
 584   case server_ok:
 585     adns__tcp_broken(ads,0,0);
 586     break;
 587   case server_disconnected:
 588     break;
 589   default:
 590     abort();
 591   }
 592   adns__consistency(ads,0,cc_entex);
 593 }
 594
 595 int adns_processany(adns_state ads) {
 596   int r, i;
 597   struct timeval now;
 598   struct pollfd pollfds[MAX_POLLFDS];
 599   int npollfds;
 600
 601   adns__consistency(ads,0,cc_entex);
 602
 603   r= gettimeofday(&now,0);
 604   if (!r) adns_processtimeouts(ads,&now);
 605
 606   /* We just use adns__fdevents to loop over the fd's trying them.
 607    * This seems more sensible than calling select, since we're most
 608    * likely just to want to do a read on one or two fds anyway.
 609    */
 610   npollfds= adns__pollfds(ads,pollfds);
 611   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events;
 612   adns__fdevents(ads,
 613                  pollfds,npollfds,
 614                  0,0,0,0,
 615                  now,&r);
 616
 617   adns__consistency(ads,0,cc_entex);
 618   return 0;
 619 }
 620
 621 void adns__autosys(adns_state ads, struct timeval now) {
 622   if (ads->iflags & adns_if_noautosys) return;
 623   adns_processany(ads);
 624 }
 625
 626 int adns__internal_check(adns_state ads,
 627                          adns_query *query_io,
 628                          adns_answer **answer,
 629                          void **context_r) {
 630   adns_query qu;
 631
 632   qu= *query_io;
 633   if (!qu) {
 634     if (ads->output.head) {
 635       qu= ads->output.head;
 636     } else if (ads->udpw.head || ads->tcpw.head) {
 637       return EAGAIN;
 638     } else {
 639       return ESRCH;
 640     }
 641   } else {
 642     if (qu->id>=0) return EAGAIN;
 643   }
 644   LIST_UNLINK(ads->output,qu);
 645   *answer= qu->answer;
 646   if (context_r) *context_r= qu->ctx.ext;
 647   *query_io= qu;
 648   free(qu);
 649   return 0;
 650 }
 651
 652 int adns_wait(adns_state ads,
 653               adns_query *query_io,
 654               adns_answer **answer_r,
 655               void **context_r) {
 656   int r, maxfd, rsel;
 657   fd_set readfds, writefds, exceptfds;
 658   struct timeval tvbuf, *tvp;
 659
 660   adns__consistency(ads,*query_io,cc_entex);
 661   for (;;) {
 662     r= adns__internal_check(ads,query_io,answer_r,context_r);
 663     if (r != EAGAIN) break;
 664     maxfd= 0; tvp= 0;
 665     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 666     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 667     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 668     if (rsel==-1) {
 669       if (errno == EINTR) {
 670         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 671       } else {
 672         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 673         adns_globalsystemfailure(ads);
 674       }
 675     } else {
 676       assert(rsel >= 0);
 677       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 678     }
 679   }
 680   adns__consistency(ads,0,cc_entex);
 681   return r;
 682 }
 683
 684 int adns_check(adns_state ads,
 685                adns_query *query_io,
 686                adns_answer **answer_r,
 687                void **context_r) {
 688   struct timeval now;
 689   int r;
 690
 691   adns__consistency(ads,*query_io,cc_entex);
 692   r= gettimeofday(&now,0);
 693   if (!r) adns__autosys(ads,now);
 694
 695   r= adns__internal_check(ads,query_io,answer_r,context_r);
 696   adns__consistency(ads,0,cc_entex);
 697   return r;
 698 }