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