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) continue;
 187       LIST_UNLINK(ads->timew,qu);
 188       if (qu->state != query_tosend) {
 189         adns__query_fail(qu,adns_s_timeout);
 190       } else {
 191         adns__query_send(qu,now);
 192       }
 193       nqu= ads->timew.head;
 194     }
 195   }
 196 }
 197
 198 void adns_firsttimeout(adns_state ads,
 199                        struct timeval **tv_io, struct timeval *tvbuf,
 200                        struct timeval now) {
 201   adns__consistency(ads,0,cc_entex);
 202   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 203   adns__consistency(ads,0,cc_entex);
 204 }
 205
 206 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 207   struct timeval tv_buf;
 208
 209   adns__consistency(ads,0,cc_entex);
 210   adns__must_gettimeofday(ads,&now,&tv_buf);
 211   if (now) adns__timeouts(ads, 1, 0,0, *now);
 212   adns__consistency(ads,0,cc_entex);
 213 }
 214
 215 /* fd handling functions.  These are the top-level of the real work of
 216  * reception and often transmission.
 217  */
 218
 219 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 220   /* Returns the number of entries filled in.  Always zeroes revents. */
 221
 222   assert(MAX_POLLFDS==2);
 223
 224   pollfds_buf[0].fd= ads->udpsocket;
 225   pollfds_buf[0].events= POLLIN;
 226   pollfds_buf[0].revents= 0;
 227
 228   switch (ads->tcpstate) {
 229   case server_disconnected:
 230     return 1;
 231   case server_connecting:
 232     pollfds_buf[1].events= POLLOUT;
 233     break;
 234   case server_ok:
 235     pollfds_buf[1].events= ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 236     break;
 237   default:
 238     abort();
 239   }
 240   pollfds_buf[1].fd= ads->tcpsocket;
 241   return 2;
 242 }
 243
 244 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 245   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 246   byte udpbuf[DNS_MAXUDP];
 247   struct sockaddr_in udpaddr;
 248
 249   adns__consistency(ads,0,cc_entex);
 250
 251   switch (ads->tcpstate) {
 252   case server_disconnected:
 253   case server_connecting:
 254     break;
 255   case server_ok:
 256     if (fd != ads->tcpsocket) break;
 257     assert(!ads->tcprecv_skip);
 258     for (;;) {
 259       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 260         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 261                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 262         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 263           old_skip= ads->tcprecv_skip;
 264           ads->tcprecv_skip += 2+dgramlen;
 265           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 266                           dgramlen, ads->tcpserver, 1,*now);
 267           continue;
 268         } else {
 269           want= 2+dgramlen;
 270         }
 271       } else {
 272         want= 2;
 273       }
 274       ads->tcprecv.used -= ads->tcprecv_skip;
 275       memmove(ads->tcprecv.buf,ads->tcprecv.buf+ads->tcprecv_skip,ads->tcprecv.used);
 276       ads->tcprecv_skip= 0;
 277       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 278       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 279       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 280       r= read(ads->tcpsocket,
 281               ads->tcprecv.buf+ads->tcprecv.used,
 282               ads->tcprecv.avail-ads->tcprecv.used);
 283       if (r>0) {
 284         ads->tcprecv.used+= r;
 285       } else {
 286         if (r) {
 287           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 288           if (errno==EINTR) continue;
 289           if (errno_resources(errno)) { r= errno; goto xit; }
 290         }
 291         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 292         r= 0; goto xit;
 293       }
 294     } /* never reached */
 295   default:
 296     abort();
 297   }
 298   if (fd == ads->udpsocket) {
 299     for (;;) {
 300       udpaddrlen= sizeof(udpaddr);
 301       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 302                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 303       if (r<0) {
 304         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 305         if (errno == EINTR) continue;
 306         if (errno_resources(errno)) { r= errno; goto xit; }
 307         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 308         r= 0; goto xit;
 309       }
 310       if (udpaddrlen != sizeof(udpaddr)) {
 311         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 312                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 313         continue;
 314       }
 315       if (udpaddr.sin_family != AF_INET) {
 316         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 317                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 318         continue;
 319       }
 320       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 321         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 322                    ntohs(udpaddr.sin_port),DNS_PORT);
 323         continue;
 324       }
 325       for (serv= 0;
 326            serv < ads->nservers &&
 327              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 328            serv++);
 329       if (serv >= ads->nservers) {
 330         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 331                    inet_ntoa(udpaddr.sin_addr));
 332         continue;
 333       }
 334       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 335     }
 336   }
 337   r= 0;
 338 xit:
 339   adns__consistency(ads,0,cc_entex);
 340   return r;
 341 }
 342
 343 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 344   int r;
 345
 346   adns__consistency(ads,0,cc_entex);
 347
 348   switch (ads->tcpstate) {
 349   case server_disconnected:
 350     break;
 351   case server_connecting:
 352     if (fd != ads->tcpsocket) break;
 353     assert(ads->tcprecv.used==0);
 354     assert(ads->tcprecv_skip==0);
 355     for (;;) {
 356       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 357       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 358       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 359         tcp_connected(ads,*now);
 360         r= 0; goto xit;
 361       }
 362       if (r>0) {
 363         adns__tcp_broken(ads,"connect/read","sent data before first request");
 364         r= 0; goto xit;
 365       }
 366       if (errno==EINTR) continue;
 367       if (errno_resources(errno)) { r= errno; goto xit; }
 368       adns__tcp_broken(ads,"connect/read",strerror(errno));
 369       r= 0; goto xit;
 370     } /* not reached */
 371   case server_ok:
 372     if (!(ads->tcpsend.used && fd == ads->tcpsocket)) break;
 373     for (;;) {
 374       adns__sigpipe_protect(ads);
 375       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 376       adns__sigpipe_unprotect(ads);
 377       if (r<0) {
 378         if (errno==EINTR) continue;
 379         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 380         if (errno_resources(errno)) { r= errno; goto xit; }
 381         adns__tcp_broken(ads,"write",strerror(errno));
 382         r= 0; goto xit;
 383       } else if (r>0) {
 384         ads->tcpsend.used -= r;
 385         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 386       }
 387     } /* not reached */
 388   default:
 389     abort();
 390   }
 391   r= 0;
 392 xit:
 393   adns__consistency(ads,0,cc_entex);
 394   return r;
 395 }
 396
 397 int adns_processexceptional(adns_state ads, int fd, const struct timeval *now) {
 398   adns__consistency(ads,0,cc_entex);
 399   switch (ads->tcpstate) {
 400   case server_disconnected:
 401     break;
 402   case server_connecting:
 403   case server_ok:
 404     if (fd != ads->tcpsocket) break;
 405     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 406     break;
 407   default:
 408     abort();
 409   }
 410   adns__consistency(ads,0,cc_entex);
 411   return 0;
 412 }
 413
 414 static void fd_event(adns_state ads, int fd,
 415                      int revent, int pollflag,
 416                      int maxfd, const fd_set *fds,
 417                      int (*func)(adns_state, int fd, const struct timeval *now),
 418                      struct timeval now, int *r_r) {
 419   int r;
 420
 421   if (!(revent & pollflag)) return;
 422   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 423   r= func(ads,fd,&now);
 424   if (r) {
 425     if (r_r) {
 426       *r_r= r;
 427     } else {
 428       adns__diag(ads,-1,0,"process fd failed after select: %s",strerror(errno));
 429       adns_globalsystemfailure(ads);
 430     }
 431   }
 432 }
 433
 434 void adns__fdevents(adns_state ads,
 435                     const struct pollfd *pollfds, int npollfds,
 436                     int maxfd, const fd_set *readfds,
 437                     const fd_set *writefds, const fd_set *exceptfds,
 438                     struct timeval now, int *r_r) {
 439   int i, fd, revents;
 440
 441   for (i=0; i<npollfds; i++) {
 442     fd= pollfds[i].fd;
 443     if (fd >= maxfd) maxfd= fd+1;
 444     revents= pollfds[i].revents;
 445     fd_event(ads,fd, revents,POLLIN, maxfd,readfds, adns_processreadable,now,r_r);
 446     fd_event(ads,fd, revents,POLLOUT, maxfd,writefds, adns_processwriteable,now,r_r);
 447     fd_event(ads,fd, revents,POLLPRI, maxfd,exceptfds, adns_processexceptional,now,r_r);
 448   }
 449 }
 450
 451 /* Wrappers for select(2). */
 452
 453 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 454                        fd_set *writefds_io, fd_set *exceptfds_io,
 455                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 456                        const struct timeval *now) {
 457   struct timeval tv_nowbuf;
 458   struct pollfd pollfds[MAX_POLLFDS];
 459   int i, fd, maxfd, npollfds;
 460
 461   adns__consistency(ads,0,cc_entex);
 462
 463   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 464     /* The caller is planning to sleep. */
 465     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 466     if (!now) goto xit;
 467     adns__timeouts(ads, 1, tv_mod,tv_tobuf, *now);
 468   }
 469
 470   npollfds= adns__pollfds(ads,pollfds);
 471   maxfd= *maxfd_io;
 472   for (i=0; i<npollfds; i++) {
 473     fd= pollfds[i].fd;
 474     if (fd >= maxfd) maxfd= fd+1;
 475     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 476     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 477     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 478   }
 479   *maxfd_io= maxfd;
 480
 481 xit:
 482   adns__consistency(ads,0,cc_entex);
 483 }
 484
 485 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 486                       const fd_set *writefds, const fd_set *exceptfds,
 487                       const struct timeval *now) {
 488   struct timeval tv_buf;
 489   struct pollfd pollfds[MAX_POLLFDS];
 490   int npollfds, i;
 491
 492   adns__consistency(ads,0,cc_entex);
 493   adns__must_gettimeofday(ads,&now,&tv_buf);
 494   if (!now) goto xit;
 495   adns_processtimeouts(ads,now);
 496
 497   npollfds= adns__pollfds(ads,pollfds);
 498   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 499   adns__fdevents(ads,
 500                  pollfds,npollfds,
 501                  maxfd,readfds,writefds,exceptfds,
 502                  *now, 0);
 503 xit:
 504   adns__consistency(ads,0,cc_entex);
 505 }
 506
 507 /* General helpful functions. */
 508
 509 void adns_globalsystemfailure(adns_state ads) {
 510   adns__consistency(ads,0,cc_entex);
 511
 512   while (ads->timew.head) {
 513     adns__query_fail(ads->timew.head, adns_s_systemfail);
 514   }
 515
 516   switch (ads->tcpstate) {
 517   case server_connecting:
 518   case server_ok:
 519     adns__tcp_closenext(ads);
 520     break;
 521   case server_disconnected:
 522     break;
 523   default:
 524     abort();
 525   }
 526   adns__consistency(ads,0,cc_entex);
 527 }
 528
 529 int adns_processany(adns_state ads) {
 530   int r, i;
 531   struct timeval now;
 532   struct pollfd pollfds[MAX_POLLFDS];
 533   int npollfds;
 534
 535   adns__consistency(ads,0,cc_entex);
 536
 537   r= gettimeofday(&now,0);
 538   if (!r) adns_processtimeouts(ads,&now);
 539
 540   /* We just use adns__fdevents to loop over the fd's trying them.
 541    * This seems more sensible than calling select, since we're most
 542    * likely just to want to do a read on one or two fds anyway.
 543    */
 544   npollfds= adns__pollfds(ads,pollfds);
 545   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events;
 546   adns__fdevents(ads,
 547                  pollfds,npollfds,
 548                  0,0,0,0,
 549                  now,&r);
 550
 551   adns__consistency(ads,0,cc_entex);
 552   return 0;
 553 }
 554
 555 void adns__autosys(adns_state ads, struct timeval now) {
 556   if (ads->iflags & adns_if_noautosys) return;
 557   adns_processany(ads);
 558 }
 559
 560 int adns__internal_check(adns_state ads,
 561                          adns_query *query_io,
 562                          adns_answer **answer,
 563                          void **context_r) {
 564   adns_query qu;
 565
 566   qu= *query_io;
 567   if (!qu) {
 568     if (ads->output.head) {
 569       qu= ads->output.head;
 570     } else if (ads->timew.head) {
 571       return EAGAIN;
 572     } else {
 573       return ESRCH;
 574     }
 575   } else {
 576     if (qu->id>=0) return EAGAIN;
 577   }
 578   LIST_UNLINK(ads->output,qu);
 579   *answer= qu->answer;
 580   if (context_r) *context_r= qu->ctx.ext;
 581   *query_io= qu;
 582   free(qu);
 583   return 0;
 584 }
 585
 586 int adns_wait(adns_state ads,
 587               adns_query *query_io,
 588               adns_answer **answer_r,
 589               void **context_r) {
 590   int r, maxfd, rsel;
 591   fd_set readfds, writefds, exceptfds;
 592   struct timeval tvbuf, *tvp;
 593
 594   adns__consistency(ads,*query_io,cc_entex);
 595   for (;;) {
 596     r= adns__internal_check(ads,query_io,answer_r,context_r);
 597     if (r != EAGAIN) break;
 598     maxfd= 0; tvp= 0;
 599     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 600     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 601     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 602     if (rsel==-1) {
 603       if (errno == EINTR) {
 604         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 605       } else {
 606         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 607         adns_globalsystemfailure(ads);
 608       }
 609     } else {
 610       assert(rsel >= 0);
 611       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 612     }
 613   }
 614   adns__consistency(ads,0,cc_entex);
 615   return r;
 616 }
 617
 618 int adns_check(adns_state ads,
 619                adns_query *query_io,
 620                adns_answer **answer_r,
 621                void **context_r) {
 622   struct timeval now;
 623   int r;
 624
 625   adns__consistency(ads,*query_io,cc_entex);
 626   r= gettimeofday(&now,0);
 627   if (!r) adns__autosys(ads,now);
 628
 629   r= adns__internal_check(ads,query_io,answer_r,context_r);
 630   adns__consistency(ads,0,cc_entex);
 631   return r;
 632 }