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 static void tcp_broken_events(adns_state ads) {
  87   adns_query qu, nqu;
  88
  89   assert(ads->tcpstate == server_broken);
  90   for (qu= ads->tcpw.head; qu; qu= nqu) {
  91     nqu= qu->next;
  92     assert(qu->state == query_tcpw);
  93     if (qu->retries > ads->nservers) {
  94       LIST_UNLINK(ads->tcpw,qu);
  95       adns__query_fail(qu,adns_s_allservfail);
  96     }
  97   }
  98   ads->tcpstate= server_disconnected;
  99 }
 100
 101 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
 102   int r, fd, tries;
 103   struct sockaddr_in addr;
 104   struct protoent *proto;
 105
 106   for (tries=0; tries<ads->nservers; tries++) {
 107     switch (ads->tcpstate) {
 108     case server_connecting:
 109     case server_ok:
 110     case server_broken:
 111       return;
 112     case server_disconnected:
 113       break;
 114     default:
 115       abort();
 116     }
 117
 118     assert(!ads->tcpsend.used);
 119     assert(!ads->tcprecv.used);
 120     assert(!ads->tcprecv_skip);
 121
 122     proto= getprotobyname("tcp");
 123     if (!proto) {
 124       adns__diag(ads,-1,0,"unable to find protocol no. for TCP !");
 125       return;
 126     }
 127     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 128     if (fd<0) {
 129       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 130       return;
 131     }
 132     r= adns__setnonblock(ads,fd);
 133     if (r) {
 134       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking:"
 135                  " %s",strerror(r));
 136       close(fd);
 137       return;
 138     }
 139     memset(&addr,0,sizeof(addr));
 140     addr.sin_family= AF_INET;
 141     addr.sin_port= htons(DNS_PORT);
 142     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 143     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 144     ads->tcpsocket= fd;
 145     ads->tcpstate= server_connecting;
 146     if (r==0) { tcp_connected(ads,now); return; }
 147     if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
 148       ads->tcptimeout= now;
 149       timevaladd(&ads->tcptimeout,TCPCONNMS);
 150       return;
 151     }
 152     adns__tcp_broken(ads,"connect",strerror(errno));
 153     tcp_broken_events(ads);
 154   }
 155 }
 156
 157 /* Timeout handling functions. */
 158
 159 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 160                              struct timeval *tv_buf) {
 161   const struct timeval *now;
 162   int r;
 163
 164   now= *now_io;
 165   if (now) return;
 166   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 167   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 168   adns_globalsystemfailure(ads);
 169   return;
 170 }
 171
 172 static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf) {
 173   struct timeval *rbuf;
 174
 175   if (!tv_io) return;
 176
 177   rbuf= *tv_io;
 178   if (!rbuf) { *tv_io= rbuf= tvbuf; }
 179
 180   timerclear(rbuf);
 181 }
 182
 183 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 184                         struct timeval maxto) {
 185   struct timeval *rbuf;
 186
 187   if (!tv_io) return;
 188   rbuf= *tv_io;
 189   if (!rbuf) {
 190     *tvbuf= maxto; *tv_io= tvbuf;
 191   } else {
 192     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 193   }
 194 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 195         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 196 }
 197
 198 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 199                            struct timeval now, struct timeval maxtime) {
 200   /* tv_io may be 0 */
 201   ldiv_t dr;
 202
 203 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 204         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 205   if (!tv_io) return;
 206   maxtime.tv_sec -= (now.tv_sec+2);
 207   maxtime.tv_usec -= (now.tv_usec-2000000);
 208   dr= ldiv(maxtime.tv_usec,1000000);
 209   maxtime.tv_sec += dr.quot;
 210   maxtime.tv_usec -= dr.quot*1000000;
 211   if (maxtime.tv_sec<0) timerclear(&maxtime);
 212   inter_maxto(tv_io,tvbuf,maxtime);
 213 }
 214
 215 static void timeouts_queue(adns_state ads, int act,
 216                            struct timeval **tv_io, struct timeval *tvbuf,
 217                            struct timeval now, struct query_queue *queue) {
 218   adns_query qu, nqu;
 219
 220   for (qu= queue->head; qu; qu= nqu) {
 221     nqu= qu->next;
 222     if (!timercmp(&now,&qu->timeout,>)) {
 223       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 224     } else {
 225       if (!act) { inter_immed(tv_io,tvbuf); return; }
 226       LIST_UNLINK(*queue,qu);
 227       if (qu->state != query_tosend) {
 228         adns__query_fail(qu,adns_s_timeout);
 229       } else {
 230         adns__query_send(qu,now);
 231       }
 232       nqu= queue->head;
 233     }
 234   }
 235 }
 236
 237 static void tcp_events(adns_state ads, int act,
 238                        struct timeval **tv_io, struct timeval *tvbuf,
 239                        struct timeval now) {
 240   for (;;) {
 241     switch (ads->tcpstate) {
 242     case server_broken:
 243       if (!act) { inter_immed(tv_io,tvbuf); return; }
 244       tcp_broken_events(ads);
 245     case server_disconnected: /* fall through */
 246       if (!ads->tcpw.head) return;
 247       if (!act) { inter_immed(tv_io,tvbuf); return; }
 248       adns__tcp_tryconnect(ads,now);
 249       break;
 250     case server_ok:
 251       if (ads->tcpw.head) return;
 252       if (!ads->tcptimeout.tv_sec) {
 253         assert(!ads->tcptimeout.tv_usec);
 254         ads->tcptimeout= now;
 255         timevaladd(&ads->tcptimeout,TCPIDLEMS);
 256       }
 257     case server_connecting: /* fall through */
 258       if (!act || !timercmp(&now,&ads->tcptimeout,>)) {
 259         inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
 260         return;
 261       } {
 262         /* TCP timeout has happened */
 263         switch (ads->tcpstate) {
 264         case server_connecting: /* failed to connect */
 265           adns__tcp_broken(ads,"unable to make connection","timed out");
 266           break;
 267         case server_ok: /* idle timeout */
 268           tcp_close(ads);
 269           ads->tcpstate= server_disconnected;
 270           return;
 271         default:
 272           abort();
 273         }
 274       }
 275       break;
 276     default:
 277       abort();
 278     }
 279   }
 280   return;
 281 }
 282
 283 void adns__timeouts(adns_state ads, int act,
 284                     struct timeval **tv_io, struct timeval *tvbuf,
 285                     struct timeval now) {
 286   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
 287   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
 288   tcp_events(ads,act,tv_io,tvbuf,now);
 289 }
 290
 291 void adns_firsttimeout(adns_state ads,
 292                        struct timeval **tv_io, struct timeval *tvbuf,
 293                        struct timeval now) {
 294   adns__consistency(ads,0,cc_entex);
 295   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 296   adns__consistency(ads,0,cc_entex);
 297 }
 298
 299 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 300   struct timeval tv_buf;
 301
 302   adns__consistency(ads,0,cc_entex);
 303   adns__must_gettimeofday(ads,&now,&tv_buf);
 304   if (now) adns__timeouts(ads, 1, 0,0, *now);
 305   adns__consistency(ads,0,cc_entex);
 306 }
 307
 308 /* fd handling functions.  These are the top-level of the real work of
 309  * reception and often transmission.
 310  */
 311
 312 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 313   /* Returns the number of entries filled in.  Always zeroes revents. */
 314
 315   assert(MAX_POLLFDS==2);
 316
 317   pollfds_buf[0].fd= ads->udpsocket;
 318   pollfds_buf[0].events= POLLIN;
 319   pollfds_buf[0].revents= 0;
 320
 321   switch (ads->tcpstate) {
 322   case server_disconnected:
 323   case server_broken:
 324     return 1;
 325   case server_connecting:
 326     pollfds_buf[1].events= POLLOUT;
 327     break;
 328   case server_ok:
 329     pollfds_buf[1].events=
 330       ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 331     break;
 332   default:
 333     abort();
 334   }
 335   pollfds_buf[1].fd= ads->tcpsocket;
 336   return 2;
 337 }
 338
 339 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 340   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 341   byte udpbuf[DNS_MAXUDP];
 342   struct sockaddr_in udpaddr;
 343
 344   adns__consistency(ads,0,cc_entex);
 345
 346   switch (ads->tcpstate) {
 347   case server_disconnected:
 348   case server_broken:
 349   case server_connecting:
 350     break;
 351   case server_ok:
 352     if (fd != ads->tcpsocket) break;
 353     assert(!ads->tcprecv_skip);
 354     do {
 355       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 356         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 357                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 358         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 359           old_skip= ads->tcprecv_skip;
 360           ads->tcprecv_skip += 2+dgramlen;
 361           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 362                           dgramlen, ads->tcpserver, 1,*now);
 363           continue;
 364         } else {
 365           want= 2+dgramlen;
 366         }
 367       } else {
 368         want= 2;
 369       }
 370       ads->tcprecv.used -= ads->tcprecv_skip;
 371       memmove(ads->tcprecv.buf, ads->tcprecv.buf+ads->tcprecv_skip,
 372               ads->tcprecv.used);
 373       ads->tcprecv_skip= 0;
 374       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 375       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 376       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 377       r= read(ads->tcpsocket,
 378               ads->tcprecv.buf+ads->tcprecv.used,
 379               ads->tcprecv.avail-ads->tcprecv.used);
 380       if (r>0) {
 381         ads->tcprecv.used+= r;
 382       } else {
 383         if (r) {
 384           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 385           if (errno==EINTR) continue;
 386           if (errno_resources(errno)) { r= errno; goto xit; }
 387         }
 388         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 389       }
 390     } while (ads->tcpstate == server_ok);
 391     r= 0; goto xit;
 392   default:
 393     abort();
 394   }
 395   if (fd == ads->udpsocket) {
 396     for (;;) {
 397       udpaddrlen= sizeof(udpaddr);
 398       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 399                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 400       if (r<0) {
 401         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 402         if (errno == EINTR) continue;
 403         if (errno_resources(errno)) { r= errno; goto xit; }
 404         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 405         r= 0; goto xit;
 406       }
 407       if (udpaddrlen != sizeof(udpaddr)) {
 408         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 409                    " (expected %lu)", udpaddrlen,
 410                    (unsigned long)sizeof(udpaddr));
 411         continue;
 412       }
 413       if (udpaddr.sin_family != AF_INET) {
 414         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 415                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 416         continue;
 417       }
 418       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 419         adns__diag(ads,-1,0,"datagram received from wrong port"
 420                    " %u (expected %u)", ntohs(udpaddr.sin_port),DNS_PORT);
 421         continue;
 422       }
 423       for (serv= 0;
 424            serv < ads->nservers &&
 425              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 426            serv++);
 427       if (serv >= ads->nservers) {
 428         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 429                    inet_ntoa(udpaddr.sin_addr));
 430         continue;
 431       }
 432       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 433     }
 434   }
 435   r= 0;
 436 xit:
 437   adns__consistency(ads,0,cc_entex);
 438   return r;
 439 }
 440
 441 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 442   int r;
 443
 444   adns__consistency(ads,0,cc_entex);
 445
 446   switch (ads->tcpstate) {
 447   case server_disconnected:
 448   case server_broken:
 449     break;
 450   case server_connecting:
 451     if (fd != ads->tcpsocket) break;
 452     assert(ads->tcprecv.used==0);
 453     assert(ads->tcprecv_skip==0);
 454     for (;;) {
 455       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 456       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 457       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 458         tcp_connected(ads,*now);
 459         r= 0; goto xit;
 460       }
 461       if (r>0) {
 462         adns__tcp_broken(ads,"connect/read","sent data before first request");
 463         r= 0; goto xit;
 464       }
 465       if (errno==EINTR) continue;
 466       if (errno_resources(errno)) { r= errno; goto xit; }
 467       adns__tcp_broken(ads,"connect/read",strerror(errno));
 468       r= 0; goto xit;
 469     } /* not reached */
 470   case server_ok:
 471     if (fd != ads->tcpsocket) break;
 472     while (ads->tcpsend.used) {
 473       adns__sigpipe_protect(ads);
 474       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 475       adns__sigpipe_unprotect(ads);
 476       if (r<0) {
 477         if (errno==EINTR) continue;
 478         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 479         if (errno_resources(errno)) { r= errno; goto xit; }
 480         adns__tcp_broken(ads,"write",strerror(errno));
 481         r= 0; goto xit;
 482       } else if (r>0) {
 483         ads->tcpsend.used -= r;
 484         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 485       }
 486     }
 487     r= 0;
 488     goto xit;
 489   default:
 490     abort();
 491   }
 492   r= 0;
 493 xit:
 494   adns__consistency(ads,0,cc_entex);
 495   return r;
 496 }
 497
 498 int adns_processexceptional(adns_state ads, int fd,
 499                             const struct timeval *now) {
 500   adns__consistency(ads,0,cc_entex);
 501   switch (ads->tcpstate) {
 502   case server_disconnected:
 503   case server_broken:
 504     break;
 505   case server_connecting:
 506   case server_ok:
 507     if (fd != ads->tcpsocket) break;
 508     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 509     break;
 510   default:
 511     abort();
 512   }
 513   adns__consistency(ads,0,cc_entex);
 514   return 0;
 515 }
 516
 517 static void fd_event(adns_state ads, int fd,
 518                      int revent, int pollflag,
 519                      int maxfd, const fd_set *fds,
 520                      int (*func)(adns_state, int fd,
 521                                  const struct timeval *now),
 522                      struct timeval now, int *r_r) {
 523   int r;
 524
 525   if (!(revent & pollflag)) return;
 526   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 527   r= func(ads,fd,&now);
 528   if (r) {
 529     if (r_r) {
 530       *r_r= r;
 531     } else {
 532       adns__diag(ads,-1,0,"process fd failed after select:"
 533                  " %s",strerror(errno));
 534       adns_globalsystemfailure(ads);
 535     }
 536   }
 537 }
 538
 539 void adns__fdevents(adns_state ads,
 540                     const struct pollfd *pollfds, int npollfds,
 541                     int maxfd, const fd_set *readfds,
 542                     const fd_set *writefds, const fd_set *exceptfds,
 543                     struct timeval now, int *r_r) {
 544   int i, fd, revents;
 545
 546   for (i=0; i<npollfds; i++) {
 547     fd= pollfds[i].fd;
 548     if (fd >= maxfd) maxfd= fd+1;
 549     revents= pollfds[i].revents;
 550 #define EV(pollfl,fds,how)  \
 551     fd_event(ads,fd, revents,pollfl, maxfd,fds, adns_process##how,now,r_r)
 552     EV( POLLIN,  readfds,   readable    );
 553     EV( POLLOUT, writefds,  writeable   );
 554     EV( POLLPRI, exceptfds, exceptional );
 555 #undef EV
 556   }
 557 }
 558
 559 /* Wrappers for select(2). */
 560
 561 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 562                        fd_set *writefds_io, fd_set *exceptfds_io,
 563                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 564                        const struct timeval *now) {
 565   struct timeval tv_nowbuf;
 566   struct pollfd pollfds[MAX_POLLFDS];
 567   int i, fd, maxfd, npollfds;
 568
 569   adns__consistency(ads,0,cc_entex);
 570
 571   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 572     /* The caller is planning to sleep. */
 573     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 574     if (!now) { inter_immed(tv_mod,tv_tobuf); goto xit; }
 575     adns__timeouts(ads, 0, tv_mod,tv_tobuf, *now);
 576   }
 577
 578   npollfds= adns__pollfds(ads,pollfds);
 579   maxfd= *maxfd_io;
 580   for (i=0; i<npollfds; i++) {
 581     fd= pollfds[i].fd;
 582     if (fd >= maxfd) maxfd= fd+1;
 583     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 584     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 585     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 586   }
 587   *maxfd_io= maxfd;
 588
 589 xit:
 590   adns__consistency(ads,0,cc_entex);
 591 }
 592
 593 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 594                       const fd_set *writefds, const fd_set *exceptfds,
 595                       const struct timeval *now) {
 596   struct timeval tv_buf;
 597   struct pollfd pollfds[MAX_POLLFDS];
 598   int npollfds, i;
 599
 600   adns__consistency(ads,0,cc_entex);
 601   adns__must_gettimeofday(ads,&now,&tv_buf);
 602   if (!now) goto xit;
 603   adns_processtimeouts(ads,now);
 604
 605   npollfds= adns__pollfds(ads,pollfds);
 606   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 607   adns__fdevents(ads,
 608                  pollfds,npollfds,
 609                  maxfd,readfds,writefds,exceptfds,
 610                  *now, 0);
 611 xit:
 612   adns__consistency(ads,0,cc_entex);
 613 }
 614
 615 /* General helpful functions. */
 616
 617 void adns_globalsystemfailure(adns_state ads) {
 618   adns__consistency(ads,0,cc_entex);
 619
 620   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 621   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 622
 623   switch (ads->tcpstate) {
 624   case server_connecting:
 625   case server_ok:
 626     adns__tcp_broken(ads,0,0);
 627     break;
 628   case server_disconnected:
 629   case server_broken:
 630     break;
 631   default:
 632     abort();
 633   }
 634   adns__consistency(ads,0,cc_entex);
 635 }
 636
 637 int adns_processany(adns_state ads) {
 638   int r, i;
 639   struct timeval now;
 640   struct pollfd pollfds[MAX_POLLFDS];
 641   int npollfds;
 642
 643   adns__consistency(ads,0,cc_entex);
 644
 645   r= gettimeofday(&now,0);
 646   if (!r) adns_processtimeouts(ads,&now);
 647
 648   /* We just use adns__fdevents to loop over the fd's trying them.
 649    * This seems more sensible than calling select, since we're most
 650    * likely just to want to do a read on one or two fds anyway.
 651    */
 652   npollfds= adns__pollfds(ads,pollfds);
 653   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events & ~POLLPRI;
 654   adns__fdevents(ads,
 655                  pollfds,npollfds,
 656                  0,0,0,0,
 657                  now,&r);
 658
 659   adns__consistency(ads,0,cc_entex);
 660   return 0;
 661 }
 662
 663 void adns__autosys(adns_state ads, struct timeval now) {
 664   if (ads->iflags & adns_if_noautosys) return;
 665   adns_processany(ads);
 666 }
 667
 668 int adns__internal_check(adns_state ads,
 669                          adns_query *query_io,
 670                          adns_answer **answer,
 671                          void **context_r) {
 672   adns_query qu;
 673
 674   qu= *query_io;
 675   if (!qu) {
 676     if (ads->output.head) {
 677       qu= ads->output.head;
 678     } else if (ads->udpw.head || ads->tcpw.head) {
 679       return EAGAIN;
 680     } else {
 681       return ESRCH;
 682     }
 683   } else {
 684     if (qu->id>=0) return EAGAIN;
 685   }
 686   LIST_UNLINK(ads->output,qu);
 687   *answer= qu->answer;
 688   if (context_r) *context_r= qu->ctx.ext;
 689   *query_io= qu;
 690   free(qu);
 691   return 0;
 692 }
 693
 694 int adns_wait(adns_state ads,
 695               adns_query *query_io,
 696               adns_answer **answer_r,
 697               void **context_r) {
 698   int r, maxfd, rsel;
 699   fd_set readfds, writefds, exceptfds;
 700   struct timeval tvbuf, *tvp;
 701
 702   adns__consistency(ads,*query_io,cc_entex);
 703   for (;;) {
 704     r= adns__internal_check(ads,query_io,answer_r,context_r);
 705     if (r != EAGAIN) break;
 706     maxfd= 0; tvp= 0;
 707     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 708     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 709     assert(tvp);
 710     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 711     if (rsel==-1) {
 712       if (errno == EINTR) {
 713         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 714       } else {
 715         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 716         adns_globalsystemfailure(ads);
 717       }
 718     } else {
 719       assert(rsel >= 0);
 720       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 721     }
 722   }
 723   adns__consistency(ads,0,cc_entex);
 724   return r;
 725 }
 726
 727 int adns_check(adns_state ads,
 728                adns_query *query_io,
 729                adns_answer **answer_r,
 730                void **context_r) {
 731   struct timeval now;
 732   int r;
 733
 734   adns__consistency(ads,*query_io,cc_entex);
 735   r= gettimeofday(&now,0);
 736   if (!r) adns__autosys(ads,now);
 737
 738   r= adns__internal_check(ads,query_io,answer_r,context_r);
 739   adns__consistency(ads,0,cc_entex);
 740   return r;
 741 }