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 part of adns, which is
   9  *    Copyright (C) 1997-2000,2003,2006  Ian Jackson
  10  *    Copyright (C) 1999-2000,2003,2006  Tony Finch
  11  *    Copyright (C) 1991 Massachusetts Institute of Technology
  12  *  (See the file INSTALL for full details.)
  13  *
  14  *  This program is free software; you can redistribute it and/or modify
  15  *  it under the terms of the GNU General Public License as published by
  16  *  the Free Software Foundation; either version 2, or (at your option)
  17  *  any later version.
  18  *
  19  *  This program is distributed in the hope that it will be useful,
  20  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  *  GNU General Public License for more details.
  23  *
  24  *  You should have received a copy of the GNU General Public License
  25  *  along with this program; if not, write to the Free Software Foundation,
  26  *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 #include <errno.h>
  30 #include <stdlib.h>
  31 #include <unistd.h>
  32
  33 #include <sys/types.h>
  34 #include <sys/time.h>
  35 #include <netdb.h>
  36 #include <sys/socket.h>
  37 #include <netinet/in.h>
  38 #include <arpa/inet.h>
  39
  40 #include "internal.h"
  41 #include "tvarith.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   adns_query qu;
  57
  58   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  59   serv= ads->tcpserver;
  60   if (what) adns__warn(ads,serv,0,"TCP connection failed: %s: %s",what,why);
  61
  62   if (ads->tcpstate == server_connecting) {
  63     /* Counts as a retry for all the queries waiting for TCP. */
  64     for (qu= ads->tcpw.head; qu; qu= qu->next)
  65       qu->retries++;
  66   }
  67
  68   tcp_close(ads);
  69   ads->tcpstate= server_broken;
  70   ads->tcpserver= (serv+1)%ads->nservers;
  71 }
  72
  73 static void tcp_connected(adns_state ads, struct timeval now) {
  74   adns_query qu, nqu;
  75
  76   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  77   ads->tcpstate= server_ok;
  78   for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
  79     nqu= qu->next;
  80     assert(qu->state == query_tcpw);
  81     adns__querysend_tcp(qu,now);
  82   }
  83 }
  84
  85 static void tcp_broken_events(adns_state ads) {
  86   adns_query qu, nqu;
  87
  88   assert(ads->tcpstate == server_broken);
  89   for (qu= ads->tcpw.head; qu; qu= nqu) {
  90     nqu= qu->next;
  91     assert(qu->state == query_tcpw);
  92     if (qu->retries > ads->nservers) {
  93       LIST_UNLINK(ads->tcpw,qu);
  94       adns__query_fail(qu,adns_s_allservfail);
  95     }
  96   }
  97   ads->tcpstate= server_disconnected;
  98 }
  99
 100 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
 101   int r, fd, tries;
 102   struct sockaddr_in addr;
 103   struct protoent *proto;
 104
 105   for (tries=0; tries<ads->nservers; tries++) {
 106     switch (ads->tcpstate) {
 107     case server_connecting:
 108     case server_ok:
 109     case server_broken:
 110       return;
 111     case server_disconnected:
 112       break;
 113     default:
 114       abort();
 115     }
 116
 117     assert(!ads->tcpsend.used);
 118     assert(!ads->tcprecv.used);
 119     assert(!ads->tcprecv_skip);
 120
 121     proto= getprotobyname("tcp");
 122     if (!proto) {
 123       adns__diag(ads,-1,0,"unable to find protocol no. for TCP !");
 124       return;
 125     }
 126     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 127     if (fd<0) {
 128       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 129       return;
 130     }
 131     r= adns__setnonblock(ads,fd);
 132     if (r) {
 133       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking:"
 134                  " %s",strerror(r));
 135       close(fd);
 136       return;
 137     }
 138     memset(&addr,0,sizeof(addr));
 139     addr.sin_family= AF_INET;
 140     addr.sin_port= htons(DNS_PORT);
 141     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 142     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 143     ads->tcpsocket= fd;
 144     ads->tcpstate= server_connecting;
 145     if (r==0) { tcp_connected(ads,now); return; }
 146     if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
 147       ads->tcptimeout= now;
 148       timevaladd(&ads->tcptimeout,TCPCONNMS);
 149       return;
 150     }
 151     adns__tcp_broken(ads,"connect",strerror(errno));
 152     tcp_broken_events(ads);
 153   }
 154 }
 155
 156 /* Timeout handling functions. */
 157
 158 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 159                              struct timeval *tv_buf) {
 160   const struct timeval *now;
 161   int r;
 162
 163   now= *now_io;
 164   if (now) return;
 165   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 166   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 167   adns_globalsystemfailure(ads);
 168   return;
 169 }
 170
 171 static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf) {
 172   struct timeval *rbuf;
 173
 174   if (!tv_io) return;
 175
 176   rbuf= *tv_io;
 177   if (!rbuf) { *tv_io= rbuf= tvbuf; }
 178
 179   timerclear(rbuf);
 180 }
 181
 182 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 183                         struct timeval maxto) {
 184   struct timeval *rbuf;
 185
 186   if (!tv_io) return;
 187   rbuf= *tv_io;
 188   if (!rbuf) {
 189     *tvbuf= maxto; *tv_io= tvbuf;
 190   } else {
 191     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 192   }
 193 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 194         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 195 }
 196
 197 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 198                            struct timeval now, struct timeval maxtime) {
 199   /* tv_io may be 0 */
 200   ldiv_t dr;
 201
 202 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 203         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 204   if (!tv_io) return;
 205   maxtime.tv_sec -= (now.tv_sec+2);
 206   maxtime.tv_usec -= (now.tv_usec-2000000);
 207   dr= ldiv(maxtime.tv_usec,1000000);
 208   maxtime.tv_sec += dr.quot;
 209   maxtime.tv_usec -= dr.quot*1000000;
 210   if (maxtime.tv_sec<0) timerclear(&maxtime);
 211   inter_maxto(tv_io,tvbuf,maxtime);
 212 }
 213
 214 static void timeouts_queue(adns_state ads, int act,
 215                            struct timeval **tv_io, struct timeval *tvbuf,
 216                            struct timeval now, struct query_queue *queue) {
 217   adns_query qu, nqu;
 218
 219   for (qu= queue->head; qu; qu= nqu) {
 220     nqu= qu->next;
 221     if (!timercmp(&now,&qu->timeout,>)) {
 222       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 223     } else {
 224       if (!act) { inter_immed(tv_io,tvbuf); return; }
 225       LIST_UNLINK(*queue,qu);
 226       if (qu->state != query_tosend) {
 227         adns__query_fail(qu,adns_s_timeout);
 228       } else {
 229         adns__query_send(qu,now);
 230       }
 231       nqu= queue->head;
 232     }
 233   }
 234 }
 235
 236 static void tcp_events(adns_state ads, int act,
 237                        struct timeval **tv_io, struct timeval *tvbuf,
 238                        struct timeval now) {
 239   for (;;) {
 240     switch (ads->tcpstate) {
 241     case server_broken:
 242       if (!act) { inter_immed(tv_io,tvbuf); return; }
 243       tcp_broken_events(ads);
 244     case server_disconnected: /* fall through */
 245       if (!ads->tcpw.head) return;
 246       if (!act) { inter_immed(tv_io,tvbuf); return; }
 247       adns__tcp_tryconnect(ads,now);
 248       break;
 249     case server_ok:
 250       if (ads->tcpw.head) return;
 251       if (!ads->tcptimeout.tv_sec) {
 252         assert(!ads->tcptimeout.tv_usec);
 253         ads->tcptimeout= now;
 254         timevaladd(&ads->tcptimeout,TCPIDLEMS);
 255       }
 256     case server_connecting: /* fall through */
 257       if (!act || !timercmp(&now,&ads->tcptimeout,>)) {
 258         inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
 259         return;
 260       } {
 261         /* TCP timeout has happened */
 262         switch (ads->tcpstate) {
 263         case server_connecting: /* failed to connect */
 264           adns__tcp_broken(ads,"unable to make connection","timed out");
 265           break;
 266         case server_ok: /* idle timeout */
 267           tcp_close(ads);
 268           ads->tcpstate= server_disconnected;
 269           return;
 270         default:
 271           abort();
 272         }
 273       }
 274       break;
 275     default:
 276       abort();
 277     }
 278   }
 279   return;
 280 }
 281
 282 void adns__timeouts(adns_state ads, int act,
 283                     struct timeval **tv_io, struct timeval *tvbuf,
 284                     struct timeval now) {
 285   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
 286   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
 287   tcp_events(ads,act,tv_io,tvbuf,now);
 288 }
 289
 290 void adns_firsttimeout(adns_state ads,
 291                        struct timeval **tv_io, struct timeval *tvbuf,
 292                        struct timeval now) {
 293   adns__consistency(ads,0,cc_entex);
 294   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 295   adns__consistency(ads,0,cc_entex);
 296 }
 297
 298 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 299   struct timeval tv_buf;
 300
 301   adns__consistency(ads,0,cc_entex);
 302   adns__must_gettimeofday(ads,&now,&tv_buf);
 303   if (now) adns__timeouts(ads, 1, 0,0, *now);
 304   adns__consistency(ads,0,cc_entex);
 305 }
 306
 307 /* fd handling functions.  These are the top-level of the real work of
 308  * reception and often transmission.
 309  */
 310
 311 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 312   /* Returns the number of entries filled in.  Always zeroes revents. */
 313
 314   assert(MAX_POLLFDS==2);
 315
 316   pollfds_buf[0].fd= ads->udpsocket;
 317   pollfds_buf[0].events= POLLIN;
 318   pollfds_buf[0].revents= 0;
 319
 320   switch (ads->tcpstate) {
 321   case server_disconnected:
 322   case server_broken:
 323     return 1;
 324   case server_connecting:
 325     pollfds_buf[1].events= POLLOUT;
 326     break;
 327   case server_ok:
 328     pollfds_buf[1].events=
 329       ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 330     break;
 331   default:
 332     abort();
 333   }
 334   pollfds_buf[1].fd= ads->tcpsocket;
 335   return 2;
 336 }
 337
 338 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 339   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 340   byte udpbuf[DNS_MAXUDP];
 341   struct sockaddr_in udpaddr;
 342
 343   adns__consistency(ads,0,cc_entex);
 344
 345   switch (ads->tcpstate) {
 346   case server_disconnected:
 347   case server_broken:
 348   case server_connecting:
 349     break;
 350   case server_ok:
 351     if (fd != ads->tcpsocket) break;
 352     assert(!ads->tcprecv_skip);
 353     do {
 354       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 355         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 356                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 357         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 358           old_skip= ads->tcprecv_skip;
 359           ads->tcprecv_skip += 2+dgramlen;
 360           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 361                           dgramlen, ads->tcpserver, 1,*now);
 362           continue;
 363         } else {
 364           want= 2+dgramlen;
 365         }
 366       } else {
 367         want= 2;
 368       }
 369       ads->tcprecv.used -= ads->tcprecv_skip;
 370       memmove(ads->tcprecv.buf, ads->tcprecv.buf+ads->tcprecv_skip,
 371               ads->tcprecv.used);
 372       ads->tcprecv_skip= 0;
 373       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 374       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 375       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 376       r= read(ads->tcpsocket,
 377               ads->tcprecv.buf+ads->tcprecv.used,
 378               ads->tcprecv.avail-ads->tcprecv.used);
 379       if (r>0) {
 380         ads->tcprecv.used+= r;
 381       } else {
 382         if (r) {
 383           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 384           if (errno==EINTR) continue;
 385           if (errno_resources(errno)) { r= errno; goto xit; }
 386         }
 387         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 388       }
 389     } while (ads->tcpstate == server_ok);
 390     r= 0; goto xit;
 391   default:
 392     abort();
 393   }
 394   if (fd == ads->udpsocket) {
 395     for (;;) {
 396       udpaddrlen= sizeof(udpaddr);
 397       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 398                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 399       if (r<0) {
 400         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 401         if (errno == EINTR) continue;
 402         if (errno_resources(errno)) { r= errno; goto xit; }
 403         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 404         r= 0; goto xit;
 405       }
 406       if (udpaddrlen != sizeof(udpaddr)) {
 407         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 408                    " (expected %lu)", udpaddrlen,
 409                    (unsigned long)sizeof(udpaddr));
 410         continue;
 411       }
 412       if (udpaddr.sin_family != AF_INET) {
 413         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 414                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 415         continue;
 416       }
 417       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 418         adns__diag(ads,-1,0,"datagram received from wrong port"
 419                    " %u (expected %u)", ntohs(udpaddr.sin_port),DNS_PORT);
 420         continue;
 421       }
 422       for (serv= 0;
 423            serv < ads->nservers &&
 424              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 425            serv++);
 426       if (serv >= ads->nservers) {
 427         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 428                    inet_ntoa(udpaddr.sin_addr));
 429         continue;
 430       }
 431       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 432     }
 433   }
 434   r= 0;
 435 xit:
 436   adns__consistency(ads,0,cc_entex);
 437   return r;
 438 }
 439
 440 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 441   int r;
 442
 443   adns__consistency(ads,0,cc_entex);
 444
 445   switch (ads->tcpstate) {
 446   case server_disconnected:
 447   case server_broken:
 448     break;
 449   case server_connecting:
 450     if (fd != ads->tcpsocket) break;
 451     assert(ads->tcprecv.used==0);
 452     assert(ads->tcprecv_skip==0);
 453     for (;;) {
 454       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 455       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 456       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 457         tcp_connected(ads,*now);
 458         r= 0; goto xit;
 459       }
 460       if (r>0) {
 461         adns__tcp_broken(ads,"connect/read","sent data before first request");
 462         r= 0; goto xit;
 463       }
 464       if (errno==EINTR) continue;
 465       if (errno_resources(errno)) { r= errno; goto xit; }
 466       adns__tcp_broken(ads,"connect/read",strerror(errno));
 467       r= 0; goto xit;
 468     } /* not reached */
 469   case server_ok:
 470     if (fd != ads->tcpsocket) break;
 471     while (ads->tcpsend.used) {
 472       adns__sigpipe_protect(ads);
 473       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 474       adns__sigpipe_unprotect(ads);
 475       if (r<0) {
 476         if (errno==EINTR) continue;
 477         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 478         if (errno_resources(errno)) { r= errno; goto xit; }
 479         adns__tcp_broken(ads,"write",strerror(errno));
 480         r= 0; goto xit;
 481       } else if (r>0) {
 482         ads->tcpsend.used -= r;
 483         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 484       }
 485     }
 486     r= 0;
 487     goto xit;
 488   default:
 489     abort();
 490   }
 491   r= 0;
 492 xit:
 493   adns__consistency(ads,0,cc_entex);
 494   return r;
 495 }
 496
 497 int adns_processexceptional(adns_state ads, int fd,
 498                             const struct timeval *now) {
 499   adns__consistency(ads,0,cc_entex);
 500   switch (ads->tcpstate) {
 501   case server_disconnected:
 502   case server_broken:
 503     break;
 504   case server_connecting:
 505   case server_ok:
 506     if (fd != ads->tcpsocket) break;
 507     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 508     break;
 509   default:
 510     abort();
 511   }
 512   adns__consistency(ads,0,cc_entex);
 513   return 0;
 514 }
 515
 516 static void fd_event(adns_state ads, int fd,
 517                      int revent, int pollflag,
 518                      int maxfd, const fd_set *fds,
 519                      int (*func)(adns_state, int fd,
 520                                  const struct timeval *now),
 521                      struct timeval now, int *r_r) {
 522   int r;
 523
 524   if (!(revent & pollflag)) return;
 525   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 526   r= func(ads,fd,&now);
 527   if (r) {
 528     if (r_r) {
 529       *r_r= r;
 530     } else {
 531       adns__diag(ads,-1,0,"process fd failed after select:"
 532                  " %s",strerror(errno));
 533       adns_globalsystemfailure(ads);
 534     }
 535   }
 536 }
 537
 538 void adns__fdevents(adns_state ads,
 539                     const struct pollfd *pollfds, int npollfds,
 540                     int maxfd, const fd_set *readfds,
 541                     const fd_set *writefds, const fd_set *exceptfds,
 542                     struct timeval now, int *r_r) {
 543   int i, fd, revents;
 544
 545   for (i=0; i<npollfds; i++) {
 546     fd= pollfds[i].fd;
 547     if (fd >= maxfd) maxfd= fd+1;
 548     revents= pollfds[i].revents;
 549 #define EV(pollfl,fds,how)  \
 550     fd_event(ads,fd, revents,pollfl, maxfd,fds, adns_process##how,now,r_r)
 551     EV( POLLIN,  readfds,   readable    );
 552     EV( POLLOUT, writefds,  writeable   );
 553     EV( POLLPRI, exceptfds, exceptional );
 554 #undef EV
 555   }
 556 }
 557
 558 /* Wrappers for select(2). */
 559
 560 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 561                        fd_set *writefds_io, fd_set *exceptfds_io,
 562                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 563                        const struct timeval *now) {
 564   struct timeval tv_nowbuf;
 565   struct pollfd pollfds[MAX_POLLFDS];
 566   int i, fd, maxfd, npollfds;
 567
 568   adns__consistency(ads,0,cc_entex);
 569
 570   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 571     /* The caller is planning to sleep. */
 572     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 573     if (!now) { inter_immed(tv_mod,tv_tobuf); goto xit; }
 574     adns__timeouts(ads, 0, tv_mod,tv_tobuf, *now);
 575   }
 576
 577   npollfds= adns__pollfds(ads,pollfds);
 578   maxfd= *maxfd_io;
 579   for (i=0; i<npollfds; i++) {
 580     fd= pollfds[i].fd;
 581     if (fd >= maxfd) maxfd= fd+1;
 582     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 583     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 584     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 585   }
 586   *maxfd_io= maxfd;
 587
 588 xit:
 589   adns__consistency(ads,0,cc_entex);
 590 }
 591
 592 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 593                       const fd_set *writefds, const fd_set *exceptfds,
 594                       const struct timeval *now) {
 595   struct timeval tv_buf;
 596   struct pollfd pollfds[MAX_POLLFDS];
 597   int npollfds, i;
 598
 599   adns__consistency(ads,0,cc_entex);
 600   adns__must_gettimeofday(ads,&now,&tv_buf);
 601   if (!now) goto xit;
 602   adns_processtimeouts(ads,now);
 603
 604   npollfds= adns__pollfds(ads,pollfds);
 605   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 606   adns__fdevents(ads,
 607                  pollfds,npollfds,
 608                  maxfd,readfds,writefds,exceptfds,
 609                  *now, 0);
 610 xit:
 611   adns__consistency(ads,0,cc_entex);
 612 }
 613
 614 /* General helpful functions. */
 615
 616 void adns_globalsystemfailure(adns_state ads) {
 617   adns__consistency(ads,0,cc_entex);
 618
 619   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 620   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 621
 622   switch (ads->tcpstate) {
 623   case server_connecting:
 624   case server_ok:
 625     adns__tcp_broken(ads,0,0);
 626     break;
 627   case server_disconnected:
 628   case server_broken:
 629     break;
 630   default:
 631     abort();
 632   }
 633   adns__consistency(ads,0,cc_entex);
 634 }
 635
 636 int adns_processany(adns_state ads) {
 637   int r, i;
 638   struct timeval now;
 639   struct pollfd pollfds[MAX_POLLFDS];
 640   int npollfds;
 641
 642   adns__consistency(ads,0,cc_entex);
 643
 644   r= gettimeofday(&now,0);
 645   if (!r) adns_processtimeouts(ads,&now);
 646
 647   /* We just use adns__fdevents to loop over the fd's trying them.
 648    * This seems more sensible than calling select, since we're most
 649    * likely just to want to do a read on one or two fds anyway.
 650    */
 651   npollfds= adns__pollfds(ads,pollfds);
 652   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events & ~POLLPRI;
 653   adns__fdevents(ads,
 654                  pollfds,npollfds,
 655                  0,0,0,0,
 656                  now,&r);
 657
 658   adns__consistency(ads,0,cc_entex);
 659   return 0;
 660 }
 661
 662 void adns__autosys(adns_state ads, struct timeval now) {
 663   if (ads->iflags & adns_if_noautosys) return;
 664   adns_processany(ads);
 665 }
 666
 667 int adns__internal_check(adns_state ads,
 668                          adns_query *query_io,
 669                          adns_answer **answer,
 670                          void **context_r) {
 671   adns_query qu;
 672
 673   qu= *query_io;
 674   if (!qu) {
 675     if (ads->output.head) {
 676       qu= ads->output.head;
 677     } else if (ads->udpw.head || ads->tcpw.head) {
 678       return EAGAIN;
 679     } else {
 680       return ESRCH;
 681     }
 682   } else {
 683     if (qu->id>=0) return EAGAIN;
 684   }
 685   LIST_UNLINK(ads->output,qu);
 686   *answer= qu->answer;
 687   if (context_r) *context_r= qu->ctx.ext;
 688   *query_io= qu;
 689   free(qu);
 690   return 0;
 691 }
 692
 693 int adns_wait(adns_state ads,
 694               adns_query *query_io,
 695               adns_answer **answer_r,
 696               void **context_r) {
 697   int r, maxfd, rsel;
 698   fd_set readfds, writefds, exceptfds;
 699   struct timeval tvbuf, *tvp;
 700
 701   adns__consistency(ads,*query_io,cc_entex);
 702   for (;;) {
 703     r= adns__internal_check(ads,query_io,answer_r,context_r);
 704     if (r != EAGAIN) break;
 705     maxfd= 0; tvp= 0;
 706     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 707     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 708     assert(tvp);
 709     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 710     if (rsel==-1) {
 711       if (errno == EINTR) {
 712         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 713       } else {
 714         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 715         adns_globalsystemfailure(ads);
 716       }
 717     } else {
 718       assert(rsel >= 0);
 719       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 720     }
 721   }
 722   adns__consistency(ads,0,cc_entex);
 723   return r;
 724 }
 725
 726 int adns_check(adns_state ads,
 727                adns_query *query_io,
 728                adns_answer **answer_r,
 729                void **context_r) {
 730   struct timeval now;
 731   int r;
 732
 733   adns__consistency(ads,*query_io,cc_entex);
 734   r= gettimeofday(&now,0);
 735   if (!r) adns__autosys(ads,now);
 736
 737   r= adns__internal_check(ads,query_io,answer_r,context_r);
 738   adns__consistency(ads,0,cc_entex);
 739   return r;
 740 }