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