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   close(ads->tcpsocket);
  47   ads->tcpsocket= -1;
  48   ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
  49 }
  50
  51 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  52   int serv;
  53   adns_query qu;
  54
  55   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  56   serv= ads->tcpserver;
  57   if (what) adns__warn(ads,serv,0,"TCP connection failed: %s: %s",what,why);
  58
  59   if (ads->tcpstate == server_connecting) {
  60     /* Counts as a retry for all the queries waiting for TCP. */
  61     for (qu= ads->tcpw.head; qu; qu= qu->next)
  62       qu->retries++;
  63   }
  64
  65   tcp_close(ads);
  66   ads->tcpstate= server_broken;
  67   ads->tcpserver= (serv+1)%ads->nservers;
  68 }
  69
  70 static void tcp_connected(adns_state ads, struct timeval now) {
  71   adns_query qu, nqu;
  72
  73   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  74   ads->tcpstate= server_ok;
  75   for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
  76     nqu= qu->next;
  77     assert(qu->state == query_tcpw);
  78     adns__querysend_tcp(qu,now);
  79   }
  80 }
  81
  82 static void tcp_broken_events(adns_state ads) {
  83   adns_query qu, nqu;
  84
  85   assert(ads->tcpstate == server_broken);
  86   for (qu= ads->tcpw.head; qu; qu= nqu) {
  87     nqu= qu->next;
  88     assert(qu->state == query_tcpw);
  89     if (qu->retries > ads->nservers) {
  90       LIST_UNLINK(ads->tcpw,qu);
  91       adns__query_fail(qu,adns_s_allservfail);
  92     }
  93   }
  94   ads->tcpstate= server_disconnected;
  95 }
  96
  97 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  98   int r, fd, tries;
  99   struct sockaddr_in addr;
 100   struct protoent *proto;
 101
 102   for (tries=0; tries<ads->nservers; tries++) {
 103     switch (ads->tcpstate) {
 104     case server_connecting:
 105     case server_ok:
 106     case server_broken:
 107       return;
 108     case server_disconnected:
 109       break;
 110     default:
 111       abort();
 112     }
 113
 114     assert(!ads->tcpsend.used);
 115     assert(!ads->tcprecv.used);
 116     assert(!ads->tcprecv_skip);
 117
 118     proto= getprotobyname("tcp");
 119     if (!proto) {
 120       adns__diag(ads,-1,0,"unable to find protocol no. for TCP !");
 121       return;
 122     }
 123     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 124     if (fd<0) {
 125       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 126       return;
 127     }
 128     r= adns__setnonblock(ads,fd);
 129     if (r) {
 130       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking:"
 131                  " %s",strerror(r));
 132       close(fd);
 133       return;
 134     }
 135     memset(&addr,0,sizeof(addr));
 136     addr.sin_family= AF_INET;
 137     addr.sin_port= htons(DNS_PORT);
 138     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 139     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 140     ads->tcpsocket= fd;
 141     ads->tcpstate= server_connecting;
 142     if (r==0) { tcp_connected(ads,now); return; }
 143     if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
 144       ads->tcptimeout= now;
 145       timevaladd(&ads->tcptimeout,TCPCONNMS);
 146       return;
 147     }
 148     adns__tcp_broken(ads,"connect",strerror(errno));
 149     tcp_broken_events(ads);
 150   }
 151 }
 152
 153 /* Timeout handling functions. */
 154
 155 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 156                              struct timeval *tv_buf) {
 157   const struct timeval *now;
 158   int r;
 159
 160   now= *now_io;
 161   if (now) return;
 162   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 163   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 164   adns_globalsystemfailure(ads);
 165   return;
 166 }
 167
 168 static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf) {
 169   struct timeval *rbuf;
 170
 171   if (!tv_io) return;
 172
 173   rbuf= *tv_io;
 174   if (!rbuf) { *tv_io= rbuf= tvbuf; }
 175
 176   timerclear(rbuf);
 177 }
 178
 179 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 180                         struct timeval maxto) {
 181   struct timeval *rbuf;
 182
 183   if (!tv_io) return;
 184   rbuf= *tv_io;
 185   if (!rbuf) {
 186     *tvbuf= maxto; *tv_io= tvbuf;
 187   } else {
 188     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 189   }
 190 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 191         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 192 }
 193
 194 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 195                            struct timeval now, struct timeval maxtime) {
 196   /* tv_io may be 0 */
 197   ldiv_t dr;
 198
 199 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 200         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 201   if (!tv_io) return;
 202   maxtime.tv_sec -= (now.tv_sec+2);
 203   maxtime.tv_usec -= (now.tv_usec-2000000);
 204   dr= ldiv(maxtime.tv_usec,1000000);
 205   maxtime.tv_sec += dr.quot;
 206   maxtime.tv_usec -= dr.quot*1000000;
 207   if (maxtime.tv_sec<0) timerclear(&maxtime);
 208   inter_maxto(tv_io,tvbuf,maxtime);
 209 }
 210
 211 static void timeouts_queue(adns_state ads, int act,
 212                            struct timeval **tv_io, struct timeval *tvbuf,
 213                            struct timeval now, struct query_queue *queue) {
 214   adns_query qu, nqu;
 215
 216   for (qu= queue->head; qu; qu= nqu) {
 217     nqu= qu->next;
 218     if (!timercmp(&now,&qu->timeout,>)) {
 219       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 220     } else {
 221       if (!act) { inter_immed(tv_io,tvbuf); return; }
 222       LIST_UNLINK(*queue,qu);
 223       if (qu->state != query_tosend) {
 224         adns__query_fail(qu,adns_s_timeout);
 225       } else {
 226         adns__query_send(qu,now);
 227       }
 228       nqu= queue->head;
 229     }
 230   }
 231 }
 232
 233 static void tcp_events(adns_state ads, int act,
 234                        struct timeval **tv_io, struct timeval *tvbuf,
 235                        struct timeval now) {
 236   for (;;) {
 237     switch (ads->tcpstate) {
 238     case server_broken:
 239       if (!act) { inter_immed(tv_io,tvbuf); return; }
 240       tcp_broken_events(ads);
 241     case server_disconnected: /* fall through */
 242       if (!ads->tcpw.head) return;
 243       if (!act) { inter_immed(tv_io,tvbuf); return; }
 244       adns__tcp_tryconnect(ads,now);
 245       break;
 246     case server_ok:
 247       if (ads->tcpw.head) return;
 248       if (!ads->tcptimeout.tv_sec) {
 249         assert(!ads->tcptimeout.tv_usec);
 250         ads->tcptimeout= now;
 251         timevaladd(&ads->tcptimeout,TCPIDLEMS);
 252       }
 253     case server_connecting: /* fall through */
 254       if (!act || !timercmp(&now,&ads->tcptimeout,>)) {
 255         inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
 256         return;
 257       } {
 258         /* TCP timeout has happened */
 259         switch (ads->tcpstate) {
 260         case server_connecting: /* failed to connect */
 261           adns__tcp_broken(ads,"unable to make connection","timed out");
 262           break;
 263         case server_ok: /* idle timeout */
 264           tcp_close(ads);
 265           ads->tcpstate= server_disconnected;
 266           return;
 267         default:
 268           abort();
 269         }
 270       }
 271       break;
 272     default:
 273       abort();
 274     }
 275   }
 276   return;
 277 }
 278
 279 void adns__timeouts(adns_state ads, int act,
 280                     struct timeval **tv_io, struct timeval *tvbuf,
 281                     struct timeval now) {
 282   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
 283   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
 284   tcp_events(ads,act,tv_io,tvbuf,now);
 285 }
 286
 287 void adns_firsttimeout(adns_state ads,
 288                        struct timeval **tv_io, struct timeval *tvbuf,
 289                        struct timeval now) {
 290   adns__consistency(ads,0,cc_entex);
 291   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 292   adns__consistency(ads,0,cc_entex);
 293 }
 294
 295 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 296   struct timeval tv_buf;
 297
 298   adns__consistency(ads,0,cc_entex);
 299   adns__must_gettimeofday(ads,&now,&tv_buf);
 300   if (now) adns__timeouts(ads, 1, 0,0, *now);
 301   adns__consistency(ads,0,cc_entex);
 302 }
 303
 304 /* fd handling functions.  These are the top-level of the real work of
 305  * reception and often transmission.
 306  */
 307
 308 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 309   /* Returns the number of entries filled in.  Always zeroes revents. */
 310
 311   assert(MAX_POLLFDS==2);
 312
 313   pollfds_buf[0].fd= ads->udpsocket;
 314   pollfds_buf[0].events= POLLIN;
 315   pollfds_buf[0].revents= 0;
 316
 317   switch (ads->tcpstate) {
 318   case server_disconnected:
 319   case server_broken:
 320     return 1;
 321   case server_connecting:
 322     pollfds_buf[1].events= POLLOUT;
 323     break;
 324   case server_ok:
 325     pollfds_buf[1].events=
 326       ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 327     break;
 328   default:
 329     abort();
 330   }
 331   pollfds_buf[1].fd= ads->tcpsocket;
 332   return 2;
 333 }
 334
 335 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 336   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 337   byte udpbuf[DNS_MAXUDP];
 338   struct sockaddr_in udpaddr;
 339
 340   adns__consistency(ads,0,cc_entex);
 341
 342   switch (ads->tcpstate) {
 343   case server_disconnected:
 344   case server_broken:
 345   case server_connecting:
 346     break;
 347   case server_ok:
 348     if (fd != ads->tcpsocket) break;
 349     assert(!ads->tcprecv_skip);
 350     do {
 351       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 352         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 353                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 354         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 355           old_skip= ads->tcprecv_skip;
 356           ads->tcprecv_skip += 2+dgramlen;
 357           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 358                           dgramlen, ads->tcpserver, 1,*now);
 359           continue;
 360         } else {
 361           want= 2+dgramlen;
 362         }
 363       } else {
 364         want= 2;
 365       }
 366       ads->tcprecv.used -= ads->tcprecv_skip;
 367       memmove(ads->tcprecv.buf, ads->tcprecv.buf+ads->tcprecv_skip,
 368               ads->tcprecv.used);
 369       ads->tcprecv_skip= 0;
 370       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 371       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 372       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 373       r= read(ads->tcpsocket,
 374               ads->tcprecv.buf+ads->tcprecv.used,
 375               ads->tcprecv.avail-ads->tcprecv.used);
 376       if (r>0) {
 377         ads->tcprecv.used+= r;
 378       } else {
 379         if (r) {
 380           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 381           if (errno==EINTR) continue;
 382           if (errno_resources(errno)) { r= errno; goto xit; }
 383         }
 384         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 385       }
 386     } while (ads->tcpstate == server_ok);
 387     r= 0; goto xit;
 388   default:
 389     abort();
 390   }
 391   if (fd == ads->udpsocket) {
 392     for (;;) {
 393       udpaddrlen= sizeof(udpaddr);
 394       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 395                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 396       if (r<0) {
 397         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 398         if (errno == EINTR) continue;
 399         if (errno_resources(errno)) { r= errno; goto xit; }
 400         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 401         r= 0; goto xit;
 402       }
 403       if (udpaddrlen != sizeof(udpaddr)) {
 404         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 405                    " (expected %lu)", udpaddrlen,
 406                    (unsigned long)sizeof(udpaddr));
 407         continue;
 408       }
 409       if (udpaddr.sin_family != AF_INET) {
 410         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 411                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 412         continue;
 413       }
 414       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 415         adns__diag(ads,-1,0,"datagram received from wrong port"
 416                    " %u (expected %u)", ntohs(udpaddr.sin_port),DNS_PORT);
 417         continue;
 418       }
 419       for (serv= 0;
 420            serv < ads->nservers &&
 421              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 422            serv++);
 423       if (serv >= ads->nservers) {
 424         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 425                    inet_ntoa(udpaddr.sin_addr));
 426         continue;
 427       }
 428       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 429     }
 430   }
 431   r= 0;
 432 xit:
 433   adns__consistency(ads,0,cc_entex);
 434   return r;
 435 }
 436
 437 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 438   int r;
 439
 440   adns__consistency(ads,0,cc_entex);
 441
 442   switch (ads->tcpstate) {
 443   case server_disconnected:
 444   case server_broken:
 445     break;
 446   case server_connecting:
 447     if (fd != ads->tcpsocket) break;
 448     assert(ads->tcprecv.used==0);
 449     assert(ads->tcprecv_skip==0);
 450     for (;;) {
 451       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 452       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 453       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 454         tcp_connected(ads,*now);
 455         r= 0; goto xit;
 456       }
 457       if (r>0) {
 458         adns__tcp_broken(ads,"connect/read","sent data before first request");
 459         r= 0; goto xit;
 460       }
 461       if (errno==EINTR) continue;
 462       if (errno_resources(errno)) { r= errno; goto xit; }
 463       adns__tcp_broken(ads,"connect/read",strerror(errno));
 464       r= 0; goto xit;
 465     } /* not reached */
 466   case server_ok:
 467     if (fd != ads->tcpsocket) break;
 468     while (ads->tcpsend.used) {
 469       adns__sigpipe_protect(ads);
 470       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 471       adns__sigpipe_unprotect(ads);
 472       if (r<0) {
 473         if (errno==EINTR) continue;
 474         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 475         if (errno_resources(errno)) { r= errno; goto xit; }
 476         adns__tcp_broken(ads,"write",strerror(errno));
 477         r= 0; goto xit;
 478       } else if (r>0) {
 479         ads->tcpsend.used -= r;
 480         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 481       }
 482     }
 483     r= 0;
 484     goto xit;
 485   default:
 486     abort();
 487   }
 488   r= 0;
 489 xit:
 490   adns__consistency(ads,0,cc_entex);
 491   return r;
 492 }
 493
 494 int adns_processexceptional(adns_state ads, int fd,
 495                             const struct timeval *now) {
 496   adns__consistency(ads,0,cc_entex);
 497   switch (ads->tcpstate) {
 498   case server_disconnected:
 499   case server_broken:
 500     break;
 501   case server_connecting:
 502   case server_ok:
 503     if (fd != ads->tcpsocket) break;
 504     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 505     break;
 506   default:
 507     abort();
 508   }
 509   adns__consistency(ads,0,cc_entex);
 510   return 0;
 511 }
 512
 513 static void fd_event(adns_state ads, int fd,
 514                      int revent, int pollflag,
 515                      int maxfd, const fd_set *fds,
 516                      int (*func)(adns_state, int fd,
 517                                  const struct timeval *now),
 518                      struct timeval now, int *r_r) {
 519   int r;
 520
 521   if (!(revent & pollflag)) return;
 522   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 523   r= func(ads,fd,&now);
 524   if (r) {
 525     if (r_r) {
 526       *r_r= r;
 527     } else {
 528       adns__diag(ads,-1,0,"process fd failed after select:"
 529                  " %s",strerror(errno));
 530       adns_globalsystemfailure(ads);
 531     }
 532   }
 533 }
 534
 535 void adns__fdevents(adns_state ads,
 536                     const struct pollfd *pollfds, int npollfds,
 537                     int maxfd, const fd_set *readfds,
 538                     const fd_set *writefds, const fd_set *exceptfds,
 539                     struct timeval now, int *r_r) {
 540   int i, fd, revents;
 541
 542   for (i=0; i<npollfds; i++) {
 543     fd= pollfds[i].fd;
 544     if (fd >= maxfd) maxfd= fd+1;
 545     revents= pollfds[i].revents;
 546 #define EV(pollfl,fds,how)  \
 547     fd_event(ads,fd, revents,pollfl, maxfd,fds, adns_process##how,now,r_r)
 548     EV( POLLIN,  readfds,   readable    );
 549     EV( POLLOUT, writefds,  writeable   );
 550     EV( POLLPRI, exceptfds, exceptional );
 551 #undef EV
 552   }
 553 }
 554
 555 /* Wrappers for select(2). */
 556
 557 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 558                        fd_set *writefds_io, fd_set *exceptfds_io,
 559                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 560                        const struct timeval *now) {
 561   struct timeval tv_nowbuf;
 562   struct pollfd pollfds[MAX_POLLFDS];
 563   int i, fd, maxfd, npollfds;
 564
 565   adns__consistency(ads,0,cc_entex);
 566
 567   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 568     /* The caller is planning to sleep. */
 569     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 570     if (!now) { inter_immed(tv_mod,tv_tobuf); goto xit; }
 571     adns__timeouts(ads, 0, tv_mod,tv_tobuf, *now);
 572   }
 573
 574   npollfds= adns__pollfds(ads,pollfds);
 575   maxfd= *maxfd_io;
 576   for (i=0; i<npollfds; i++) {
 577     fd= pollfds[i].fd;
 578     if (fd >= maxfd) maxfd= fd+1;
 579     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 580     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 581     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 582   }
 583   *maxfd_io= maxfd;
 584
 585 xit:
 586   adns__consistency(ads,0,cc_entex);
 587 }
 588
 589 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 590                       const fd_set *writefds, const fd_set *exceptfds,
 591                       const struct timeval *now) {
 592   struct timeval tv_buf;
 593   struct pollfd pollfds[MAX_POLLFDS];
 594   int npollfds, i;
 595
 596   adns__consistency(ads,0,cc_entex);
 597   adns__must_gettimeofday(ads,&now,&tv_buf);
 598   if (!now) goto xit;
 599   adns_processtimeouts(ads,now);
 600
 601   npollfds= adns__pollfds(ads,pollfds);
 602   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 603   adns__fdevents(ads,
 604                  pollfds,npollfds,
 605                  maxfd,readfds,writefds,exceptfds,
 606                  *now, 0);
 607 xit:
 608   adns__consistency(ads,0,cc_entex);
 609 }
 610
 611 /* General helpful functions. */
 612
 613 void adns_globalsystemfailure(adns_state ads) {
 614   adns__consistency(ads,0,cc_entex);
 615
 616   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 617   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 618
 619   switch (ads->tcpstate) {
 620   case server_connecting:
 621   case server_ok:
 622     adns__tcp_broken(ads,0,0);
 623     break;
 624   case server_disconnected:
 625   case server_broken:
 626     break;
 627   default:
 628     abort();
 629   }
 630   adns__consistency(ads,0,cc_entex);
 631 }
 632
 633 int adns_processany(adns_state ads) {
 634   int r, i;
 635   struct timeval now;
 636   struct pollfd pollfds[MAX_POLLFDS];
 637   int npollfds;
 638
 639   adns__consistency(ads,0,cc_entex);
 640
 641   r= gettimeofday(&now,0);
 642   if (!r) adns_processtimeouts(ads,&now);
 643
 644   /* We just use adns__fdevents to loop over the fd's trying them.
 645    * This seems more sensible than calling select, since we're most
 646    * likely just to want to do a read on one or two fds anyway.
 647    */
 648   npollfds= adns__pollfds(ads,pollfds);
 649   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events & ~POLLPRI;
 650   adns__fdevents(ads,
 651                  pollfds,npollfds,
 652                  0,0,0,0,
 653                  now,&r);
 654
 655   adns__consistency(ads,0,cc_entex);
 656   return 0;
 657 }
 658
 659 void adns__autosys(adns_state ads, struct timeval now) {
 660   if (ads->iflags & adns_if_noautosys) return;
 661   adns_processany(ads);
 662 }
 663
 664 int adns__internal_check(adns_state ads,
 665                          adns_query *query_io,
 666                          adns_answer **answer,
 667                          void **context_r) {
 668   adns_query qu;
 669
 670   qu= *query_io;
 671   if (!qu) {
 672     if (ads->output.head) {
 673       qu= ads->output.head;
 674     } else if (ads->udpw.head || ads->tcpw.head) {
 675       return EAGAIN;
 676     } else {
 677       return ESRCH;
 678     }
 679   } else {
 680     if (qu->id>=0) return EAGAIN;
 681   }
 682   LIST_UNLINK(ads->output,qu);
 683   *answer= qu->answer;
 684   if (context_r) *context_r= qu->ctx.ext;
 685   *query_io= qu;
 686   free(qu);
 687   return 0;
 688 }
 689
 690 int adns_wait(adns_state ads,
 691               adns_query *query_io,
 692               adns_answer **answer_r,
 693               void **context_r) {
 694   int r, maxfd, rsel;
 695   fd_set readfds, writefds, exceptfds;
 696   struct timeval tvbuf, *tvp;
 697
 698   adns__consistency(ads,*query_io,cc_entex);
 699   for (;;) {
 700     r= adns__internal_check(ads,query_io,answer_r,context_r);
 701     if (r != EAGAIN) break;
 702     maxfd= 0; tvp= 0;
 703     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 704     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 705     assert(tvp);
 706     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 707     if (rsel==-1) {
 708       if (errno == EINTR) {
 709         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 710       } else {
 711         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 712         adns_globalsystemfailure(ads);
 713       }
 714     } else {
 715       assert(rsel >= 0);
 716       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 717     }
 718   }
 719   adns__consistency(ads,0,cc_entex);
 720   return r;
 721 }
 722
 723 int adns_check(adns_state ads,
 724                adns_query *query_io,
 725                adns_answer **answer_r,
 726                void **context_r) {
 727   struct timeval now;
 728   int r;
 729
 730   adns__consistency(ads,*query_io,cc_entex);
 731   r= gettimeofday(&now,0);
 732   if (!r) adns__autosys(ads,now);
 733
 734   r= adns__internal_check(ads,query_io,answer_r,context_r);
 735   adns__consistency(ads,0,cc_entex);
 736   return r;
 737 }