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) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
  10  *
  11  *  It is part of adns, which is
  12  *    Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
  13  *    Copyright (C) 1999-2000 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 #include "tvarith.h"
  43
  44 /* TCP connection management. */
  45
  46 static void tcp_close(adns_state ads) {
  47   int serv;
  48
  49   serv= ads->tcpserver;
  50   close(ads->tcpsocket);
  51   ads->tcpsocket= -1;
  52   ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
  53 }
  54
  55 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  56   int serv;
  57   adns_query qu;
  58
  59   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  60   serv= ads->tcpserver;
  61   if (what) adns__warn(ads,serv,0,"TCP connection failed: %s: %s",what,why);
  62
  63   if (ads->tcpstate == server_connecting) {
  64     /* Counts as a retry for all the queries waiting for TCP. */
  65     for (qu= ads->tcpw.head; qu; qu= qu->next)
  66       qu->retries++;
  67   }
  68
  69   tcp_close(ads);
  70   ads->tcpstate= server_broken;
  71   ads->tcpserver= (serv+1)%ads->nservers;
  72 }
  73
  74 static void tcp_connected(adns_state ads, struct timeval now) {
  75   adns_query qu, nqu;
  76
  77   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  78   ads->tcpstate= server_ok;
  79   for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
  80     nqu= qu->next;
  81     assert(qu->state == query_tcpw);
  82     adns__querysend_tcp(qu,now);
  83   }
  84 }
  85
  86 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  87   int r, fd, tries;
  88   struct sockaddr_in addr;
  89   struct protoent *proto;
  90
  91   for (tries=0; tries<ads->nservers; tries++) {
  92     switch (ads->tcpstate) {
  93     case server_connecting:
  94     case server_ok:
  95     case server_broken:
  96       return;
  97     case server_disconnected:
  98       break;
  99     default:
 100       abort();
 101     }
 102
 103     assert(!ads->tcpsend.used);
 104     assert(!ads->tcprecv.used);
 105     assert(!ads->tcprecv_skip);
 106
 107     proto= getprotobyname("tcp");
 108     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
 109     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 110     if (fd<0) {
 111       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 112       return;
 113     }
 114     r= adns__setnonblock(ads,fd);
 115     if (r) {
 116       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
 117       close(fd);
 118       return;
 119     }
 120     memset(&addr,0,sizeof(addr));
 121     addr.sin_family= AF_INET;
 122     addr.sin_port= htons(DNS_PORT);
 123     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 124     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 125     ads->tcpsocket= fd;
 126     ads->tcpstate= server_connecting;
 127     if (r==0) { tcp_connected(ads,now); return; }
 128     if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
 129       ads->tcptimeout= now;
 130       timevaladd(&ads->tcptimeout,TCPCONNMS);
 131       return;
 132     }
 133     adns__tcp_broken(ads,"connect",strerror(errno));
 134     ads->tcpstate= server_disconnected;
 135   }
 136 }
 137
 138 /* Timeout handling functions. */
 139
 140 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 141                              struct timeval *tv_buf) {
 142   const struct timeval *now;
 143   int r;
 144
 145   now= *now_io;
 146   if (now) return;
 147   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 148   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 149   adns_globalsystemfailure(ads);
 150   return;
 151 }
 152
 153 static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf) {
 154   struct timeval *rbuf;
 155
 156   if (!tv_io) return;
 157
 158   rbuf= *tv_io;
 159   if (!rbuf) { *tv_io= rbuf= tvbuf; }
 160
 161   timerclear(rbuf);
 162 }
 163
 164 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 165                         struct timeval maxto) {
 166   struct timeval *rbuf;
 167
 168   if (!tv_io) return;
 169   rbuf= *tv_io;
 170   if (!rbuf) {
 171     *tvbuf= maxto; *tv_io= tvbuf;
 172   } else {
 173     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 174   }
 175 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 176         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 177 }
 178
 179 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 180                            struct timeval now, struct timeval maxtime) {
 181   /* tv_io may be 0 */
 182   ldiv_t dr;
 183
 184 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 185         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 186   if (!tv_io) return;
 187   maxtime.tv_sec -= (now.tv_sec+2);
 188   maxtime.tv_usec -= (now.tv_usec-2000000);
 189   dr= ldiv(maxtime.tv_usec,1000000);
 190   maxtime.tv_sec += dr.quot;
 191   maxtime.tv_usec -= dr.quot*1000000;
 192   if (maxtime.tv_sec<0) timerclear(&maxtime);
 193   inter_maxto(tv_io,tvbuf,maxtime);
 194 }
 195
 196 static void timeouts_queue(adns_state ads, int act,
 197                            struct timeval **tv_io, struct timeval *tvbuf,
 198                            struct timeval now, struct query_queue *queue) {
 199   adns_query qu, nqu;
 200
 201   for (qu= queue->head; qu; qu= nqu) {
 202     nqu= qu->next;
 203     if (!timercmp(&now,&qu->timeout,>)) {
 204       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 205     } else {
 206       if (!act) { inter_immed(tv_io,tvbuf); return; }
 207       LIST_UNLINK(*queue,qu);
 208       if (qu->state != query_tosend) {
 209         adns__query_fail(qu,adns_s_timeout);
 210       } else {
 211         adns__query_send(qu,now);
 212       }
 213       nqu= queue->head;
 214     }
 215   }
 216 }
 217
 218 static void tcp_events(adns_state ads, int act,
 219                        struct timeval **tv_io, struct timeval *tvbuf,
 220                        struct timeval now) {
 221   adns_query qu, nqu;
 222
 223   for (;;) {
 224     switch (ads->tcpstate) {
 225     case server_broken:
 226       if (!act) { inter_immed(tv_io,tvbuf); return; }
 227       for (qu= ads->tcpw.head; qu; qu= nqu) {
 228         nqu= qu->next;
 229         assert(qu->state == query_tcpw);
 230         if (qu->retries > ads->nservers) {
 231           LIST_UNLINK(ads->tcpw,qu);
 232           adns__query_fail(qu,adns_s_allservfail);
 233         }
 234       }
 235       ads->tcpstate= server_disconnected;
 236     case server_disconnected: /* fall through */
 237       if (!ads->tcpw.head) return;
 238       if (!act) { inter_immed(tv_io,tvbuf); return; }
 239       adns__tcp_tryconnect(ads,now);
 240       break;
 241     case server_ok:
 242       if (ads->tcpw.head) return;
 243       if (!ads->tcptimeout.tv_sec) {
 244         assert(!ads->tcptimeout.tv_usec);
 245         ads->tcptimeout= now;
 246         timevaladd(&ads->tcptimeout,TCPIDLEMS);
 247       }
 248     case server_connecting: /* fall through */
 249       if (!act || !timercmp(&now,&ads->tcptimeout,>)) {
 250         inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
 251         return;
 252       } {
 253         /* TCP timeout has happened */
 254         switch (ads->tcpstate) {
 255         case server_connecting: /* failed to connect */
 256           adns__tcp_broken(ads,"unable to make connection","timed out");
 257           break;
 258         case server_ok: /* idle timeout */
 259           tcp_close(ads);
 260           ads->tcpstate= server_disconnected;
 261           return;
 262         default:
 263           abort();
 264         }
 265       }
 266       break;
 267     default:
 268       abort();
 269     }
 270   }
 271   return;
 272 }
 273
 274 void adns__timeouts(adns_state ads, int act,
 275                     struct timeval **tv_io, struct timeval *tvbuf,
 276                     struct timeval now) {
 277   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
 278   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
 279   tcp_events(ads,act,tv_io,tvbuf,now);
 280 }
 281
 282 void adns_firsttimeout(adns_state ads,
 283                        struct timeval **tv_io, struct timeval *tvbuf,
 284                        struct timeval now) {
 285   adns__consistency(ads,0,cc_entex);
 286   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 287   adns__consistency(ads,0,cc_entex);
 288 }
 289
 290 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 291   struct timeval tv_buf;
 292
 293   adns__consistency(ads,0,cc_entex);
 294   adns__must_gettimeofday(ads,&now,&tv_buf);
 295   if (now) adns__timeouts(ads, 1, 0,0, *now);
 296   adns__consistency(ads,0,cc_entex);
 297 }
 298
 299 /* fd handling functions.  These are the top-level of the real work of
 300  * reception and often transmission.
 301  */
 302
 303 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 304   /* Returns the number of entries filled in.  Always zeroes revents. */
 305
 306   assert(MAX_POLLFDS==2);
 307
 308   pollfds_buf[0].fd= ads->udpsocket;
 309   pollfds_buf[0].events= POLLIN;
 310   pollfds_buf[0].revents= 0;
 311
 312   switch (ads->tcpstate) {
 313   case server_disconnected:
 314   case server_broken:
 315     return 1;
 316   case server_connecting:
 317     pollfds_buf[1].events= POLLOUT;
 318     break;
 319   case server_ok:
 320     pollfds_buf[1].events= ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 321     break;
 322   default:
 323     abort();
 324   }
 325   pollfds_buf[1].fd= ads->tcpsocket;
 326   return 2;
 327 }
 328
 329 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 330   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 331   byte udpbuf[DNS_MAXUDP];
 332   struct sockaddr_in udpaddr;
 333
 334   adns__consistency(ads,0,cc_entex);
 335
 336   switch (ads->tcpstate) {
 337   case server_disconnected:
 338   case server_broken:
 339   case server_connecting:
 340     break;
 341   case server_ok:
 342     if (fd != ads->tcpsocket) break;
 343     assert(!ads->tcprecv_skip);
 344     do {
 345       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 346         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 347                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 348         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 349           old_skip= ads->tcprecv_skip;
 350           ads->tcprecv_skip += 2+dgramlen;
 351           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 352                           dgramlen, ads->tcpserver, 1,*now);
 353           continue;
 354         } else {
 355           want= 2+dgramlen;
 356         }
 357       } else {
 358         want= 2;
 359       }
 360       ads->tcprecv.used -= ads->tcprecv_skip;
 361       memmove(ads->tcprecv.buf,ads->tcprecv.buf+ads->tcprecv_skip,ads->tcprecv.used);
 362       ads->tcprecv_skip= 0;
 363       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 364       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 365       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 366       r= read(ads->tcpsocket,
 367               ads->tcprecv.buf+ads->tcprecv.used,
 368               ads->tcprecv.avail-ads->tcprecv.used);
 369       if (r>0) {
 370         ads->tcprecv.used+= r;
 371       } else {
 372         if (r) {
 373           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 374           if (errno==EINTR) continue;
 375           if (errno_resources(errno)) { r= errno; goto xit; }
 376         }
 377         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 378       }
 379     } while (ads->tcpstate == server_ok);
 380     r= 0; goto xit;
 381   default:
 382     abort();
 383   }
 384   if (fd == ads->udpsocket) {
 385     for (;;) {
 386       udpaddrlen= sizeof(udpaddr);
 387       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 388                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 389       if (r<0) {
 390         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 391         if (errno == EINTR) continue;
 392         if (errno_resources(errno)) { r= errno; goto xit; }
 393         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 394         r= 0; goto xit;
 395       }
 396       if (udpaddrlen != sizeof(udpaddr)) {
 397         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 398                    " (expected %lu)", udpaddrlen,
 399                    (unsigned long)sizeof(udpaddr));
 400         continue;
 401       }
 402       if (udpaddr.sin_family != AF_INET) {
 403         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 404                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 405         continue;
 406       }
 407       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 408         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 409                    ntohs(udpaddr.sin_port),DNS_PORT);
 410         continue;
 411       }
 412       for (serv= 0;
 413            serv < ads->nservers &&
 414              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 415            serv++);
 416       if (serv >= ads->nservers) {
 417         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 418                    inet_ntoa(udpaddr.sin_addr));
 419         continue;
 420       }
 421       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 422     }
 423   }
 424   r= 0;
 425 xit:
 426   adns__consistency(ads,0,cc_entex);
 427   return r;
 428 }
 429
 430 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 431   int r;
 432
 433   adns__consistency(ads,0,cc_entex);
 434
 435   switch (ads->tcpstate) {
 436   case server_disconnected:
 437   case server_broken:
 438     break;
 439   case server_connecting:
 440     if (fd != ads->tcpsocket) break;
 441     assert(ads->tcprecv.used==0);
 442     assert(ads->tcprecv_skip==0);
 443     for (;;) {
 444       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 445       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 446       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 447         tcp_connected(ads,*now);
 448         r= 0; goto xit;
 449       }
 450       if (r>0) {
 451         adns__tcp_broken(ads,"connect/read","sent data before first request");
 452         r= 0; goto xit;
 453       }
 454       if (errno==EINTR) continue;
 455       if (errno_resources(errno)) { r= errno; goto xit; }
 456       adns__tcp_broken(ads,"connect/read",strerror(errno));
 457       r= 0; goto xit;
 458     } /* not reached */
 459   case server_ok:
 460     if (fd != ads->tcpsocket) break;
 461     while (ads->tcpsend.used) {
 462       adns__sigpipe_protect(ads);
 463       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 464       adns__sigpipe_unprotect(ads);
 465       if (r<0) {
 466         if (errno==EINTR) continue;
 467         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 468         if (errno_resources(errno)) { r= errno; goto xit; }
 469         adns__tcp_broken(ads,"write",strerror(errno));
 470         r= 0; goto xit;
 471       } else if (r>0) {
 472         ads->tcpsend.used -= r;
 473         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 474       }
 475     }
 476     r= 0;
 477     goto xit;
 478   default:
 479     abort();
 480   }
 481   r= 0;
 482 xit:
 483   adns__consistency(ads,0,cc_entex);
 484   return r;
 485 }
 486
 487 int adns_processexceptional(adns_state ads, int fd, const struct timeval *now) {
 488   adns__consistency(ads,0,cc_entex);
 489   switch (ads->tcpstate) {
 490   case server_disconnected:
 491   case server_broken:
 492     break;
 493   case server_connecting:
 494   case server_ok:
 495     if (fd != ads->tcpsocket) break;
 496     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 497     break;
 498   default:
 499     abort();
 500   }
 501   adns__consistency(ads,0,cc_entex);
 502   return 0;
 503 }
 504
 505 static void fd_event(adns_state ads, int fd,
 506                      int revent, int pollflag,
 507                      int maxfd, const fd_set *fds,
 508                      int (*func)(adns_state, int fd, const struct timeval *now),
 509                      struct timeval now, int *r_r) {
 510   int r;
 511
 512   if (!(revent & pollflag)) return;
 513   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 514   r= func(ads,fd,&now);
 515   if (r) {
 516     if (r_r) {
 517       *r_r= r;
 518     } else {
 519       adns__diag(ads,-1,0,"process fd failed after select: %s",strerror(errno));
 520       adns_globalsystemfailure(ads);
 521     }
 522   }
 523 }
 524
 525 void adns__fdevents(adns_state ads,
 526                     const struct pollfd *pollfds, int npollfds,
 527                     int maxfd, const fd_set *readfds,
 528                     const fd_set *writefds, const fd_set *exceptfds,
 529                     struct timeval now, int *r_r) {
 530   int i, fd, revents;
 531
 532   for (i=0; i<npollfds; i++) {
 533     fd= pollfds[i].fd;
 534     if (fd >= maxfd) maxfd= fd+1;
 535     revents= pollfds[i].revents;
 536     fd_event(ads,fd, revents,POLLIN, maxfd,readfds, adns_processreadable,now,r_r);
 537     fd_event(ads,fd, revents,POLLOUT, maxfd,writefds, adns_processwriteable,now,r_r);
 538     fd_event(ads,fd, revents,POLLPRI, maxfd,exceptfds, adns_processexceptional,now,r_r);
 539   }
 540 }
 541
 542 /* Wrappers for select(2). */
 543
 544 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 545                        fd_set *writefds_io, fd_set *exceptfds_io,
 546                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 547                        const struct timeval *now) {
 548   struct timeval tv_nowbuf;
 549   struct pollfd pollfds[MAX_POLLFDS];
 550   int i, fd, maxfd, npollfds;
 551
 552   adns__consistency(ads,0,cc_entex);
 553
 554   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 555     /* The caller is planning to sleep. */
 556     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 557     if (!now) { inter_immed(tv_mod,tv_tobuf); goto xit; }
 558     adns__timeouts(ads, 0, tv_mod,tv_tobuf, *now);
 559   }
 560
 561   npollfds= adns__pollfds(ads,pollfds);
 562   maxfd= *maxfd_io;
 563   for (i=0; i<npollfds; i++) {
 564     fd= pollfds[i].fd;
 565     if (fd >= maxfd) maxfd= fd+1;
 566     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 567     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 568     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 569   }
 570   *maxfd_io= maxfd;
 571
 572 xit:
 573   adns__consistency(ads,0,cc_entex);
 574 }
 575
 576 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 577                       const fd_set *writefds, const fd_set *exceptfds,
 578                       const struct timeval *now) {
 579   struct timeval tv_buf;
 580   struct pollfd pollfds[MAX_POLLFDS];
 581   int npollfds, i;
 582
 583   adns__consistency(ads,0,cc_entex);
 584   adns__must_gettimeofday(ads,&now,&tv_buf);
 585   if (!now) goto xit;
 586   adns_processtimeouts(ads,now);
 587
 588   npollfds= adns__pollfds(ads,pollfds);
 589   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 590   adns__fdevents(ads,
 591                  pollfds,npollfds,
 592                  maxfd,readfds,writefds,exceptfds,
 593                  *now, 0);
 594 xit:
 595   adns__consistency(ads,0,cc_entex);
 596 }
 597
 598 /* General helpful functions. */
 599
 600 void adns_globalsystemfailure(adns_state ads) {
 601   adns__consistency(ads,0,cc_entex);
 602
 603   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 604   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 605
 606   switch (ads->tcpstate) {
 607   case server_connecting:
 608   case server_ok:
 609     adns__tcp_broken(ads,0,0);
 610     break;
 611   case server_disconnected:
 612   case server_broken:
 613     break;
 614   default:
 615     abort();
 616   }
 617   adns__consistency(ads,0,cc_entex);
 618 }
 619
 620 int adns_processany(adns_state ads) {
 621   int r, i;
 622   struct timeval now;
 623   struct pollfd pollfds[MAX_POLLFDS];
 624   int npollfds;
 625
 626   adns__consistency(ads,0,cc_entex);
 627
 628   r= gettimeofday(&now,0);
 629   if (!r) adns_processtimeouts(ads,&now);
 630
 631   /* We just use adns__fdevents to loop over the fd's trying them.
 632    * This seems more sensible than calling select, since we're most
 633    * likely just to want to do a read on one or two fds anyway.
 634    */
 635   npollfds= adns__pollfds(ads,pollfds);
 636   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events & ~POLLPRI;
 637   adns__fdevents(ads,
 638                  pollfds,npollfds,
 639                  0,0,0,0,
 640                  now,&r);
 641
 642   adns__consistency(ads,0,cc_entex);
 643   return 0;
 644 }
 645
 646 void adns__autosys(adns_state ads, struct timeval now) {
 647   if (ads->iflags & adns_if_noautosys) return;
 648   adns_processany(ads);
 649 }
 650
 651 int adns__internal_check(adns_state ads,
 652                          adns_query *query_io,
 653                          adns_answer **answer,
 654                          void **context_r) {
 655   adns_query qu;
 656
 657   qu= *query_io;
 658   if (!qu) {
 659     if (ads->output.head) {
 660       qu= ads->output.head;
 661     } else if (ads->udpw.head || ads->tcpw.head) {
 662       return EAGAIN;
 663     } else {
 664       return ESRCH;
 665     }
 666   } else {
 667     if (qu->id>=0) return EAGAIN;
 668   }
 669   LIST_UNLINK(ads->output,qu);
 670   *answer= qu->answer;
 671   if (context_r) *context_r= qu->ctx.ext;
 672   *query_io= qu;
 673   free(qu);
 674   return 0;
 675 }
 676
 677 int adns_wait(adns_state ads,
 678               adns_query *query_io,
 679               adns_answer **answer_r,
 680               void **context_r) {
 681   int r, maxfd, rsel;
 682   fd_set readfds, writefds, exceptfds;
 683   struct timeval tvbuf, *tvp;
 684
 685   adns__consistency(ads,*query_io,cc_entex);
 686   for (;;) {
 687     r= adns__internal_check(ads,query_io,answer_r,context_r);
 688     if (r != EAGAIN) break;
 689     maxfd= 0; tvp= 0;
 690     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 691     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 692     assert(tvp);
 693     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 694     if (rsel==-1) {
 695       if (errno == EINTR) {
 696         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 697       } else {
 698         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 699         adns_globalsystemfailure(ads);
 700       }
 701     } else {
 702       assert(rsel >= 0);
 703       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 704     }
 705   }
 706   adns__consistency(ads,0,cc_entex);
 707   return r;
 708 }
 709
 710 int adns_check(adns_state ads,
 711                adns_query *query_io,
 712                adns_answer **answer_r,
 713                void **context_r) {
 714   struct timeval now;
 715   int r;
 716
 717   adns__consistency(ads,*query_io,cc_entex);
 718   r= gettimeofday(&now,0);
 719   if (!r) adns__autosys(ads,now);
 720
 721   r= adns__internal_check(ads,query_io,answer_r,context_r);
 722   adns__consistency(ads,0,cc_entex);
 723   return r;
 724 }