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 void adns__tcp_closenext(adns_state ads) {
  46   int serv;
  47
  48   serv= ads->tcpserver;
  49   close(ads->tcpsocket);
  50   ads->tcpsocket= -1;
  51   ads->tcpstate= server_disconnected;
  52   ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
  53   ads->tcpserver= (serv+1)%ads->nservers;
  54 }
  55
  56 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  57   int serv;
  58   adns_query qu, nqu;
  59
  60   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  61   serv= ads->tcpserver;
  62   adns__warn(ads,serv,0,"TCP connection lost: %s: %s",what,why);
  63   adns__tcp_closenext(ads);
  64
  65   for (qu= ads->timew.head; qu; qu= nqu) {
  66     nqu= qu->next;
  67     if (qu->state == query_tosend) continue;
  68     assert(qu->state == query_tcpwait || qu->state == query_tcpsent);
  69     qu->state= query_tcpwait;
  70     qu->tcpfailed |= (1<<serv);
  71     if (qu->tcpfailed == (1<<ads->nservers)-1) {
  72       LIST_UNLINK(ads->timew,qu);
  73       adns__query_fail(qu,adns_s_allservfail);
  74     }
  75   }
  76 }
  77
  78 static void tcp_connected(adns_state ads, struct timeval now) {
  79   adns_query qu, nqu;
  80
  81   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  82   ads->tcpstate= server_ok;
  83   for (qu= ads->timew.head; qu; qu= nqu) {
  84     nqu= qu->next;
  85     if (qu->state == query_tosend) continue;
  86     assert (qu->state == query_tcpwait);
  87     adns__query_tcp(qu,now);
  88   }
  89 }
  90
  91 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  92   int r, fd, tries;
  93   struct sockaddr_in addr;
  94   struct protoent *proto;
  95
  96   for (tries=0; tries<ads->nservers; tries++) {
  97     if (ads->tcpstate == server_connecting || ads->tcpstate == server_ok) return;
  98     assert(ads->tcpstate == server_disconnected);
  99     assert(!ads->tcpsend.used);
 100     assert(!ads->tcprecv.used);
 101     assert(!ads->tcprecv_skip);
 102
 103     proto= getprotobyname("tcp");
 104     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
 105     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 106     if (fd<0) {
 107       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 108       return;
 109     }
 110     r= adns__setnonblock(ads,fd);
 111     if (r) {
 112       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
 113       close(fd);
 114       return;
 115     }
 116     memset(&addr,0,sizeof(addr));
 117     addr.sin_family= AF_INET;
 118     addr.sin_port= htons(DNS_PORT);
 119     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 120     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 121     ads->tcpsocket= fd;
 122     ads->tcpstate= server_connecting;
 123     if (r==0) { tcp_connected(ads,now); continue; }
 124     if (errno == EWOULDBLOCK || errno == EINPROGRESS) return;
 125     adns__tcp_broken(ads,"connect",strerror(errno));
 126   }
 127 }
 128
 129 /* Timeout handling functions. */
 130
 131 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 132                              struct timeval *tv_buf) {
 133   const struct timeval *now;
 134   int r;
 135
 136   now= *now_io;
 137   if (now) return;
 138   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 139   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 140   adns_globalsystemfailure(ads);
 141   return;
 142 }
 143
 144 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 145                         struct timeval maxto) {
 146   struct timeval *rbuf;
 147
 148   if (!tv_io) return;
 149   rbuf= *tv_io;
 150   if (!rbuf) {
 151     *tvbuf= maxto; *tv_io= tvbuf;
 152   } else {
 153     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 154   }
 155 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 156         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 157 }
 158
 159 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 160                            struct timeval now, struct timeval maxtime) {
 161   ldiv_t dr;
 162
 163 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 164         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 165   if (!tv_io) return;
 166   maxtime.tv_sec -= (now.tv_sec+2);
 167   maxtime.tv_usec -= (now.tv_usec-2000000);
 168   dr= ldiv(maxtime.tv_usec,1000000);
 169   maxtime.tv_sec += dr.quot;
 170   maxtime.tv_usec -= dr.quot*1000000;
 171   if (maxtime.tv_sec<0) timerclear(&maxtime);
 172   inter_maxto(tv_io,tvbuf,maxtime);
 173 }
 174
 175 void adns__timeouts(adns_state ads, int act,
 176                     struct timeval **tv_io, struct timeval *tvbuf,
 177                     struct timeval now) {
 178   adns_query qu, nqu;
 179
 180   for (qu= ads->timew.head; qu; qu= nqu) {
 181     nqu= qu->next;
 182     if (!timercmp(&now,&qu->timeout,>)) {
 183       if (!tv_io) continue;
 184       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 185     } else {
 186       if (!act) {
 187         tvbuf->tv_sec= 0;
 188         tvbuf->tv_usec= 0;
 189         *tv_io= tvbuf;
 190         return;
 191       }
 192       LIST_UNLINK(ads->timew,qu);
 193       if (qu->state != query_tosend) {
 194         adns__query_fail(qu,adns_s_timeout);
 195       } else {
 196         adns__query_send(qu,now);
 197       }
 198       nqu= ads->timew.head;
 199     }
 200   }
 201 }
 202
 203 void adns_firsttimeout(adns_state ads,
 204                        struct timeval **tv_io, struct timeval *tvbuf,
 205                        struct timeval now) {
 206   adns__consistency(ads,0,cc_entex);
 207   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 208   adns__consistency(ads,0,cc_entex);
 209 }
 210
 211 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 212   struct timeval tv_buf;
 213
 214   adns__consistency(ads,0,cc_entex);
 215   adns__must_gettimeofday(ads,&now,&tv_buf);
 216   if (now) adns__timeouts(ads, 1, 0,0, *now);
 217   adns__consistency(ads,0,cc_entex);
 218 }
 219
 220 /* fd handling functions.  These are the top-level of the real work of
 221  * reception and often transmission.
 222  */
 223
 224 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 225   /* Returns the number of entries filled in.  Always zeroes revents. */
 226
 227   assert(MAX_POLLFDS==2);
 228
 229   pollfds_buf[0].fd= ads->udpsocket;
 230   pollfds_buf[0].events= POLLIN;
 231   pollfds_buf[0].revents= 0;
 232
 233   switch (ads->tcpstate) {
 234   case server_disconnected:
 235     return 1;
 236   case server_connecting:
 237     pollfds_buf[1].events= POLLOUT;
 238     break;
 239   case server_ok:
 240     pollfds_buf[1].events= ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 241     break;
 242   default:
 243     abort();
 244   }
 245   pollfds_buf[1].fd= ads->tcpsocket;
 246   return 2;
 247 }
 248
 249 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 250   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 251   byte udpbuf[DNS_MAXUDP];
 252   struct sockaddr_in udpaddr;
 253
 254   adns__consistency(ads,0,cc_entex);
 255
 256   switch (ads->tcpstate) {
 257   case server_disconnected:
 258   case server_connecting:
 259     break;
 260   case server_ok:
 261     if (fd != ads->tcpsocket) break;
 262     assert(!ads->tcprecv_skip);
 263     for (;;) {
 264       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 265         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 266                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 267         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 268           old_skip= ads->tcprecv_skip;
 269           ads->tcprecv_skip += 2+dgramlen;
 270           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 271                           dgramlen, ads->tcpserver, 1,*now);
 272           continue;
 273         } else {
 274           want= 2+dgramlen;
 275         }
 276       } else {
 277         want= 2;
 278       }
 279       ads->tcprecv.used -= ads->tcprecv_skip;
 280       memmove(ads->tcprecv.buf,ads->tcprecv.buf+ads->tcprecv_skip,ads->tcprecv.used);
 281       ads->tcprecv_skip= 0;
 282       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 283       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 284       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 285       r= read(ads->tcpsocket,
 286               ads->tcprecv.buf+ads->tcprecv.used,
 287               ads->tcprecv.avail-ads->tcprecv.used);
 288       if (r>0) {
 289         ads->tcprecv.used+= r;
 290       } else {
 291         if (r) {
 292           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 293           if (errno==EINTR) continue;
 294           if (errno_resources(errno)) { r= errno; goto xit; }
 295         }
 296         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 297         r= 0; goto xit;
 298       }
 299     } /* never reached */
 300   default:
 301     abort();
 302   }
 303   if (fd == ads->udpsocket) {
 304     for (;;) {
 305       udpaddrlen= sizeof(udpaddr);
 306       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 307                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 308       if (r<0) {
 309         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 310         if (errno == EINTR) continue;
 311         if (errno_resources(errno)) { r= errno; goto xit; }
 312         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 313         r= 0; goto xit;
 314       }
 315       if (udpaddrlen != sizeof(udpaddr)) {
 316         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 317                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 318         continue;
 319       }
 320       if (udpaddr.sin_family != AF_INET) {
 321         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 322                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 323         continue;
 324       }
 325       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 326         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 327                    ntohs(udpaddr.sin_port),DNS_PORT);
 328         continue;
 329       }
 330       for (serv= 0;
 331            serv < ads->nservers &&
 332              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 333            serv++);
 334       if (serv >= ads->nservers) {
 335         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 336                    inet_ntoa(udpaddr.sin_addr));
 337         continue;
 338       }
 339       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 340     }
 341   }
 342   r= 0;
 343 xit:
 344   adns__consistency(ads,0,cc_entex);
 345   return r;
 346 }
 347
 348 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 349   int r;
 350
 351   adns__consistency(ads,0,cc_entex);
 352
 353   switch (ads->tcpstate) {
 354   case server_disconnected:
 355     break;
 356   case server_connecting:
 357     if (fd != ads->tcpsocket) break;
 358     assert(ads->tcprecv.used==0);
 359     assert(ads->tcprecv_skip==0);
 360     for (;;) {
 361       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 362       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 363       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 364         tcp_connected(ads,*now);
 365         r= 0; goto xit;
 366       }
 367       if (r>0) {
 368         adns__tcp_broken(ads,"connect/read","sent data before first request");
 369         r= 0; goto xit;
 370       }
 371       if (errno==EINTR) continue;
 372       if (errno_resources(errno)) { r= errno; goto xit; }
 373       adns__tcp_broken(ads,"connect/read",strerror(errno));
 374       r= 0; goto xit;
 375     } /* not reached */
 376   case server_ok:
 377     if (!(ads->tcpsend.used && fd == ads->tcpsocket)) break;
 378     for (;;) {
 379       adns__sigpipe_protect(ads);
 380       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 381       adns__sigpipe_unprotect(ads);
 382       if (r<0) {
 383         if (errno==EINTR) continue;
 384         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 385         if (errno_resources(errno)) { r= errno; goto xit; }
 386         adns__tcp_broken(ads,"write",strerror(errno));
 387         r= 0; goto xit;
 388       } else if (r>0) {
 389         ads->tcpsend.used -= r;
 390         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 391       }
 392     } /* not reached */
 393   default:
 394     abort();
 395   }
 396   r= 0;
 397 xit:
 398   adns__consistency(ads,0,cc_entex);
 399   return r;
 400 }
 401
 402 int adns_processexceptional(adns_state ads, int fd, const struct timeval *now) {
 403   adns__consistency(ads,0,cc_entex);
 404   switch (ads->tcpstate) {
 405   case server_disconnected:
 406     break;
 407   case server_connecting:
 408   case server_ok:
 409     if (fd != ads->tcpsocket) break;
 410     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 411     break;
 412   default:
 413     abort();
 414   }
 415   adns__consistency(ads,0,cc_entex);
 416   return 0;
 417 }
 418
 419 static void fd_event(adns_state ads, int fd,
 420                      int revent, int pollflag,
 421                      int maxfd, const fd_set *fds,
 422                      int (*func)(adns_state, int fd, const struct timeval *now),
 423                      struct timeval now, int *r_r) {
 424   int r;
 425
 426   if (!(revent & pollflag)) return;
 427   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 428   r= func(ads,fd,&now);
 429   if (r) {
 430     if (r_r) {
 431       *r_r= r;
 432     } else {
 433       adns__diag(ads,-1,0,"process fd failed after select: %s",strerror(errno));
 434       adns_globalsystemfailure(ads);
 435     }
 436   }
 437 }
 438
 439 void adns__fdevents(adns_state ads,
 440                     const struct pollfd *pollfds, int npollfds,
 441                     int maxfd, const fd_set *readfds,
 442                     const fd_set *writefds, const fd_set *exceptfds,
 443                     struct timeval now, int *r_r) {
 444   int i, fd, revents;
 445
 446   for (i=0; i<npollfds; i++) {
 447     fd= pollfds[i].fd;
 448     if (fd >= maxfd) maxfd= fd+1;
 449     revents= pollfds[i].revents;
 450     fd_event(ads,fd, revents,POLLIN, maxfd,readfds, adns_processreadable,now,r_r);
 451     fd_event(ads,fd, revents,POLLOUT, maxfd,writefds, adns_processwriteable,now,r_r);
 452     fd_event(ads,fd, revents,POLLPRI, maxfd,exceptfds, adns_processexceptional,now,r_r);
 453   }
 454 }
 455
 456 /* Wrappers for select(2). */
 457
 458 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 459                        fd_set *writefds_io, fd_set *exceptfds_io,
 460                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 461                        const struct timeval *now) {
 462   struct timeval tv_nowbuf;
 463   struct pollfd pollfds[MAX_POLLFDS];
 464   int i, fd, maxfd, npollfds;
 465
 466   adns__consistency(ads,0,cc_entex);
 467
 468   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 469     /* The caller is planning to sleep. */
 470     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 471     if (!now) goto xit;
 472     adns__timeouts(ads, 1, tv_mod,tv_tobuf, *now);
 473   }
 474
 475   npollfds= adns__pollfds(ads,pollfds);
 476   maxfd= *maxfd_io;
 477   for (i=0; i<npollfds; i++) {
 478     fd= pollfds[i].fd;
 479     if (fd >= maxfd) maxfd= fd+1;
 480     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 481     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 482     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 483   }
 484   *maxfd_io= maxfd;
 485
 486 xit:
 487   adns__consistency(ads,0,cc_entex);
 488 }
 489
 490 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 491                       const fd_set *writefds, const fd_set *exceptfds,
 492                       const struct timeval *now) {
 493   struct timeval tv_buf;
 494   struct pollfd pollfds[MAX_POLLFDS];
 495   int npollfds, i;
 496
 497   adns__consistency(ads,0,cc_entex);
 498   adns__must_gettimeofday(ads,&now,&tv_buf);
 499   if (!now) goto xit;
 500   adns_processtimeouts(ads,now);
 501
 502   npollfds= adns__pollfds(ads,pollfds);
 503   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 504   adns__fdevents(ads,
 505                  pollfds,npollfds,
 506                  maxfd,readfds,writefds,exceptfds,
 507                  *now, 0);
 508 xit:
 509   adns__consistency(ads,0,cc_entex);
 510 }
 511
 512 /* General helpful functions. */
 513
 514 void adns_globalsystemfailure(adns_state ads) {
 515   adns__consistency(ads,0,cc_entex);
 516
 517   while (ads->timew.head) {
 518     adns__query_fail(ads->timew.head, adns_s_systemfail);
 519   }
 520
 521   switch (ads->tcpstate) {
 522   case server_connecting:
 523   case server_ok:
 524     adns__tcp_closenext(ads);
 525     break;
 526   case server_disconnected:
 527     break;
 528   default:
 529     abort();
 530   }
 531   adns__consistency(ads,0,cc_entex);
 532 }
 533
 534 int adns_processany(adns_state ads) {
 535   int r, i;
 536   struct timeval now;
 537   struct pollfd pollfds[MAX_POLLFDS];
 538   int npollfds;
 539
 540   adns__consistency(ads,0,cc_entex);
 541
 542   r= gettimeofday(&now,0);
 543   if (!r) adns_processtimeouts(ads,&now);
 544
 545   /* We just use adns__fdevents to loop over the fd's trying them.
 546    * This seems more sensible than calling select, since we're most
 547    * likely just to want to do a read on one or two fds anyway.
 548    */
 549   npollfds= adns__pollfds(ads,pollfds);
 550   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events;
 551   adns__fdevents(ads,
 552                  pollfds,npollfds,
 553                  0,0,0,0,
 554                  now,&r);
 555
 556   adns__consistency(ads,0,cc_entex);
 557   return 0;
 558 }
 559
 560 void adns__autosys(adns_state ads, struct timeval now) {
 561   if (ads->iflags & adns_if_noautosys) return;
 562   adns_processany(ads);
 563 }
 564
 565 int adns__internal_check(adns_state ads,
 566                          adns_query *query_io,
 567                          adns_answer **answer,
 568                          void **context_r) {
 569   adns_query qu;
 570
 571   qu= *query_io;
 572   if (!qu) {
 573     if (ads->output.head) {
 574       qu= ads->output.head;
 575     } else if (ads->timew.head) {
 576       return EAGAIN;
 577     } else {
 578       return ESRCH;
 579     }
 580   } else {
 581     if (qu->id>=0) return EAGAIN;
 582   }
 583   LIST_UNLINK(ads->output,qu);
 584   *answer= qu->answer;
 585   if (context_r) *context_r= qu->ctx.ext;
 586   *query_io= qu;
 587   free(qu);
 588   return 0;
 589 }
 590
 591 int adns_wait(adns_state ads,
 592               adns_query *query_io,
 593               adns_answer **answer_r,
 594               void **context_r) {
 595   int r, maxfd, rsel;
 596   fd_set readfds, writefds, exceptfds;
 597   struct timeval tvbuf, *tvp;
 598
 599   adns__consistency(ads,*query_io,cc_entex);
 600   for (;;) {
 601     r= adns__internal_check(ads,query_io,answer_r,context_r);
 602     if (r != EAGAIN) break;
 603     maxfd= 0; tvp= 0;
 604     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 605     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 606     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 607     if (rsel==-1) {
 608       if (errno == EINTR) {
 609         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 610       } else {
 611         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 612         adns_globalsystemfailure(ads);
 613       }
 614     } else {
 615       assert(rsel >= 0);
 616       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 617     }
 618   }
 619   adns__consistency(ads,0,cc_entex);
 620   return r;
 621 }
 622
 623 int adns_check(adns_state ads,
 624                adns_query *query_io,
 625                adns_answer **answer_r,
 626                void **context_r) {
 627   struct timeval now;
 628   int r;
 629
 630   adns__consistency(ads,*query_io,cc_entex);
 631   r= gettimeofday(&now,0);
 632   if (!r) adns__autosys(ads,now);
 633
 634   r= adns__internal_check(ads,query_io,answer_r,context_r);
 635   adns__consistency(ads,0,cc_entex);
 636   return r;
 637 }