mdw@git.distorted.org.uk Git - adns/blob - src/event.c

   1 /*
   2  * event.c
   3  * - event loop core
   4  * - TCP connection management
   5  * - user-visible check/wait and event-loop-related functions
   6  */
   7 /*
   8  *  This file is
   9  *    Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
  10  *
  11  *  It is part of adns, which is
  12  *    Copyright (C) 1997-2000 Ian Jackson <ian@davenant.greenend.org.uk>
  13  *    Copyright (C) 1999-2000 Tony Finch <dot@dotat.at>
  14  *
  15  *  This program is free software; you can redistribute it and/or modify
  16  *  it under the terms of the GNU General Public License as published by
  17  *  the Free Software Foundation; either version 2, or (at your option)
  18  *  any later version.
  19  *
  20  *  This program is distributed in the hope that it will be useful,
  21  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23  *  GNU General Public License for more details.
  24  *
  25  *  You should have received a copy of the GNU General Public License
  26  *  along with this program; if not, write to the Free Software Foundation,
  27  *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  28  */
  29
  30 #include <errno.h>
  31 #include <stdlib.h>
  32 #include <unistd.h>
  33
  34 #include <sys/types.h>
  35 #include <sys/time.h>
  36 #include <netdb.h>
  37 #include <sys/socket.h>
  38 #include <netinet/in.h>
  39 #include <arpa/inet.h>
  40
  41 #include "internal.h"
  42 #include "tvarith.h"
  43
  44 /* TCP connection management. */
  45
  46 static void tcp_close(adns_state ads) {
  47   int serv;
  48
  49   serv= ads->tcpserver;
  50   close(ads->tcpsocket);
  51   ads->tcpsocket= -1;
  52   ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
  53 }
  54
  55 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  56   int serv;
  57   adns_query qu;
  58
  59   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  60   serv= ads->tcpserver;
  61   if (what) adns__warn(ads,serv,0,"TCP connection failed: %s: %s",what,why);
  62
  63   if (ads->tcpstate == server_connecting) {
  64     /* Counts as a retry for all the queries waiting for TCP. */
  65     for (qu= ads->tcpw.head; qu; qu= qu->next)
  66       qu->retries++;
  67   }
  68
  69   tcp_close(ads);
  70   ads->tcpstate= server_broken;
  71   ads->tcpserver= (serv+1)%ads->nservers;
  72 }
  73
  74 static void tcp_connected(adns_state ads, struct timeval now) {
  75   adns_query qu, nqu;
  76
  77   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  78   ads->tcpstate= server_ok;
  79   for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
  80     nqu= qu->next;
  81     assert(qu->state == query_tcpw);
  82     adns__querysend_tcp(qu,now);
  83   }
  84 }
  85
  86 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  87   int r, fd, tries;
  88   struct sockaddr_in addr;
  89   struct protoent *proto;
  90
  91   for (tries=0; tries<ads->nservers; tries++) {
  92     switch (ads->tcpstate) {
  93     case server_connecting:
  94     case server_ok:
  95     case server_broken:
  96       return;
  97     case server_disconnected:
  98       break;
  99     default:
 100       abort();
 101     }
 102
 103     assert(!ads->tcpsend.used);
 104     assert(!ads->tcprecv.used);
 105     assert(!ads->tcprecv_skip);
 106
 107     proto= getprotobyname("tcp");
 108     if (!proto) {
 109       adns__diag(ads,-1,0,"unable to find protocol no. for TCP !");
 110       return;
 111     }
 112     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
 113     if (fd<0) {
 114       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 115       return;
 116     }
 117     r= adns__setnonblock(ads,fd);
 118     if (r) {
 119       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking:"
 120                  " %s",strerror(r));
 121       close(fd);
 122       return;
 123     }
 124     memset(&addr,0,sizeof(addr));
 125     addr.sin_family= AF_INET;
 126     addr.sin_port= htons(DNS_PORT);
 127     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 128     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 129     ads->tcpsocket= fd;
 130     ads->tcpstate= server_connecting;
 131     if (r==0) { tcp_connected(ads,now); return; }
 132     if (errno == EWOULDBLOCK || errno == EINPROGRESS) {
 133       ads->tcptimeout= now;
 134       timevaladd(&ads->tcptimeout,TCPCONNMS);
 135       return;
 136     }
 137     adns__tcp_broken(ads,"connect",strerror(errno));
 138     ads->tcpstate= server_disconnected;
 139   }
 140 }
 141
 142 /* Timeout handling functions. */
 143
 144 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 145                              struct timeval *tv_buf) {
 146   const struct timeval *now;
 147   int r;
 148
 149   now= *now_io;
 150   if (now) return;
 151   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 152   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 153   adns_globalsystemfailure(ads);
 154   return;
 155 }
 156
 157 static void inter_immed(struct timeval **tv_io, struct timeval *tvbuf) {
 158   struct timeval *rbuf;
 159
 160   if (!tv_io) return;
 161
 162   rbuf= *tv_io;
 163   if (!rbuf) { *tv_io= rbuf= tvbuf; }
 164
 165   timerclear(rbuf);
 166 }
 167
 168 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 169                         struct timeval maxto) {
 170   struct timeval *rbuf;
 171
 172   if (!tv_io) return;
 173   rbuf= *tv_io;
 174   if (!rbuf) {
 175     *tvbuf= maxto; *tv_io= tvbuf;
 176   } else {
 177     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 178   }
 179 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 180         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 181 }
 182
 183 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 184                            struct timeval now, struct timeval maxtime) {
 185   /* tv_io may be 0 */
 186   ldiv_t dr;
 187
 188 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 189         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 190   if (!tv_io) return;
 191   maxtime.tv_sec -= (now.tv_sec+2);
 192   maxtime.tv_usec -= (now.tv_usec-2000000);
 193   dr= ldiv(maxtime.tv_usec,1000000);
 194   maxtime.tv_sec += dr.quot;
 195   maxtime.tv_usec -= dr.quot*1000000;
 196   if (maxtime.tv_sec<0) timerclear(&maxtime);
 197   inter_maxto(tv_io,tvbuf,maxtime);
 198 }
 199
 200 static void timeouts_queue(adns_state ads, int act,
 201                            struct timeval **tv_io, struct timeval *tvbuf,
 202                            struct timeval now, struct query_queue *queue) {
 203   adns_query qu, nqu;
 204
 205   for (qu= queue->head; qu; qu= nqu) {
 206     nqu= qu->next;
 207     if (!timercmp(&now,&qu->timeout,>)) {
 208       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 209     } else {
 210       if (!act) { inter_immed(tv_io,tvbuf); return; }
 211       LIST_UNLINK(*queue,qu);
 212       if (qu->state != query_tosend) {
 213         adns__query_fail(qu,adns_s_timeout);
 214       } else {
 215         adns__query_send(qu,now);
 216       }
 217       nqu= queue->head;
 218     }
 219   }
 220 }
 221
 222 static void tcp_events(adns_state ads, int act,
 223                        struct timeval **tv_io, struct timeval *tvbuf,
 224                        struct timeval now) {
 225   adns_query qu, nqu;
 226
 227   for (;;) {
 228     switch (ads->tcpstate) {
 229     case server_broken:
 230       if (!act) { inter_immed(tv_io,tvbuf); return; }
 231       for (qu= ads->tcpw.head; qu; qu= nqu) {
 232         nqu= qu->next;
 233         assert(qu->state == query_tcpw);
 234         if (qu->retries > ads->nservers) {
 235           LIST_UNLINK(ads->tcpw,qu);
 236           adns__query_fail(qu,adns_s_allservfail);
 237         }
 238       }
 239       ads->tcpstate= server_disconnected;
 240     case server_disconnected: /* fall through */
 241       if (!ads->tcpw.head) return;
 242       if (!act) { inter_immed(tv_io,tvbuf); return; }
 243       adns__tcp_tryconnect(ads,now);
 244       break;
 245     case server_ok:
 246       if (ads->tcpw.head) return;
 247       if (!ads->tcptimeout.tv_sec) {
 248         assert(!ads->tcptimeout.tv_usec);
 249         ads->tcptimeout= now;
 250         timevaladd(&ads->tcptimeout,TCPIDLEMS);
 251       }
 252     case server_connecting: /* fall through */
 253       if (!act || !timercmp(&now,&ads->tcptimeout,>)) {
 254         inter_maxtoabs(tv_io,tvbuf,now,ads->tcptimeout);
 255         return;
 256       } {
 257         /* TCP timeout has happened */
 258         switch (ads->tcpstate) {
 259         case server_connecting: /* failed to connect */
 260           adns__tcp_broken(ads,"unable to make connection","timed out");
 261           break;
 262         case server_ok: /* idle timeout */
 263           tcp_close(ads);
 264           ads->tcpstate= server_disconnected;
 265           return;
 266         default:
 267           abort();
 268         }
 269       }
 270       break;
 271     default:
 272       abort();
 273     }
 274   }
 275   return;
 276 }
 277
 278 void adns__timeouts(adns_state ads, int act,
 279                     struct timeval **tv_io, struct timeval *tvbuf,
 280                     struct timeval now) {
 281   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->udpw);
 282   timeouts_queue(ads,act,tv_io,tvbuf,now, &ads->tcpw);
 283   tcp_events(ads,act,tv_io,tvbuf,now);
 284 }
 285
 286 void adns_firsttimeout(adns_state ads,
 287                        struct timeval **tv_io, struct timeval *tvbuf,
 288                        struct timeval now) {
 289   adns__consistency(ads,0,cc_entex);
 290   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 291   adns__consistency(ads,0,cc_entex);
 292 }
 293
 294 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 295   struct timeval tv_buf;
 296
 297   adns__consistency(ads,0,cc_entex);
 298   adns__must_gettimeofday(ads,&now,&tv_buf);
 299   if (now) adns__timeouts(ads, 1, 0,0, *now);
 300   adns__consistency(ads,0,cc_entex);
 301 }
 302
 303 /* fd handling functions.  These are the top-level of the real work of
 304  * reception and often transmission.
 305  */
 306
 307 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 308   /* Returns the number of entries filled in.  Always zeroes revents. */
 309
 310   assert(MAX_POLLFDS==2);
 311
 312   pollfds_buf[0].fd= ads->udpsocket;
 313   pollfds_buf[0].events= POLLIN;
 314   pollfds_buf[0].revents= 0;
 315
 316   switch (ads->tcpstate) {
 317   case server_disconnected:
 318   case server_broken:
 319     return 1;
 320   case server_connecting:
 321     pollfds_buf[1].events= POLLOUT;
 322     break;
 323   case server_ok:
 324     pollfds_buf[1].events=
 325       ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 326     break;
 327   default:
 328     abort();
 329   }
 330   pollfds_buf[1].fd= ads->tcpsocket;
 331   return 2;
 332 }
 333
 334 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 335   int want, dgramlen, r, udpaddrlen, serv, old_skip;
 336   byte udpbuf[DNS_MAXUDP];
 337   struct sockaddr_in udpaddr;
 338
 339   adns__consistency(ads,0,cc_entex);
 340
 341   switch (ads->tcpstate) {
 342   case server_disconnected:
 343   case server_broken:
 344   case server_connecting:
 345     break;
 346   case server_ok:
 347     if (fd != ads->tcpsocket) break;
 348     assert(!ads->tcprecv_skip);
 349     do {
 350       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 351         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 352                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 353         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 354           old_skip= ads->tcprecv_skip;
 355           ads->tcprecv_skip += 2+dgramlen;
 356           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 357                           dgramlen, ads->tcpserver, 1,*now);
 358           continue;
 359         } else {
 360           want= 2+dgramlen;
 361         }
 362       } else {
 363         want= 2;
 364       }
 365       ads->tcprecv.used -= ads->tcprecv_skip;
 366       memmove(ads->tcprecv.buf, ads->tcprecv.buf+ads->tcprecv_skip,
 367               ads->tcprecv.used);
 368       ads->tcprecv_skip= 0;
 369       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 370       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 371       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 372       r= read(ads->tcpsocket,
 373               ads->tcprecv.buf+ads->tcprecv.used,
 374               ads->tcprecv.avail-ads->tcprecv.used);
 375       if (r>0) {
 376         ads->tcprecv.used+= r;
 377       } else {
 378         if (r) {
 379           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 380           if (errno==EINTR) continue;
 381           if (errno_resources(errno)) { r= errno; goto xit; }
 382         }
 383         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 384       }
 385     } while (ads->tcpstate == server_ok);
 386     r= 0; goto xit;
 387   default:
 388     abort();
 389   }
 390   if (fd == ads->udpsocket) {
 391     for (;;) {
 392       udpaddrlen= sizeof(udpaddr);
 393       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 394                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 395       if (r<0) {
 396         if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 397         if (errno == EINTR) continue;
 398         if (errno_resources(errno)) { r= errno; goto xit; }
 399         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 400         r= 0; goto xit;
 401       }
 402       if (udpaddrlen != sizeof(udpaddr)) {
 403         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 404                    " (expected %lu)", udpaddrlen,
 405                    (unsigned long)sizeof(udpaddr));
 406         continue;
 407       }
 408       if (udpaddr.sin_family != AF_INET) {
 409         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 410                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 411         continue;
 412       }
 413       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 414         adns__diag(ads,-1,0,"datagram received from wrong port"
 415                    " %u (expected %u)", ntohs(udpaddr.sin_port),DNS_PORT);
 416         continue;
 417       }
 418       for (serv= 0;
 419            serv < ads->nservers &&
 420              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 421            serv++);
 422       if (serv >= ads->nservers) {
 423         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 424                    inet_ntoa(udpaddr.sin_addr));
 425         continue;
 426       }
 427       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 428     }
 429   }
 430   r= 0;
 431 xit:
 432   adns__consistency(ads,0,cc_entex);
 433   return r;
 434 }
 435
 436 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 437   int r;
 438
 439   adns__consistency(ads,0,cc_entex);
 440
 441   switch (ads->tcpstate) {
 442   case server_disconnected:
 443   case server_broken:
 444     break;
 445   case server_connecting:
 446     if (fd != ads->tcpsocket) break;
 447     assert(ads->tcprecv.used==0);
 448     assert(ads->tcprecv_skip==0);
 449     for (;;) {
 450       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 451       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 452       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 453         tcp_connected(ads,*now);
 454         r= 0; goto xit;
 455       }
 456       if (r>0) {
 457         adns__tcp_broken(ads,"connect/read","sent data before first request");
 458         r= 0; goto xit;
 459       }
 460       if (errno==EINTR) continue;
 461       if (errno_resources(errno)) { r= errno; goto xit; }
 462       adns__tcp_broken(ads,"connect/read",strerror(errno));
 463       r= 0; goto xit;
 464     } /* not reached */
 465   case server_ok:
 466     if (fd != ads->tcpsocket) break;
 467     while (ads->tcpsend.used) {
 468       adns__sigpipe_protect(ads);
 469       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 470       adns__sigpipe_unprotect(ads);
 471       if (r<0) {
 472         if (errno==EINTR) continue;
 473         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 474         if (errno_resources(errno)) { r= errno; goto xit; }
 475         adns__tcp_broken(ads,"write",strerror(errno));
 476         r= 0; goto xit;
 477       } else if (r>0) {
 478         ads->tcpsend.used -= r;
 479         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 480       }
 481     }
 482     r= 0;
 483     goto xit;
 484   default:
 485     abort();
 486   }
 487   r= 0;
 488 xit:
 489   adns__consistency(ads,0,cc_entex);
 490   return r;
 491 }
 492
 493 int adns_processexceptional(adns_state ads, int fd,
 494                             const struct timeval *now) {
 495   adns__consistency(ads,0,cc_entex);
 496   switch (ads->tcpstate) {
 497   case server_disconnected:
 498   case server_broken:
 499     break;
 500   case server_connecting:
 501   case server_ok:
 502     if (fd != ads->tcpsocket) break;
 503     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 504     break;
 505   default:
 506     abort();
 507   }
 508   adns__consistency(ads,0,cc_entex);
 509   return 0;
 510 }
 511
 512 static void fd_event(adns_state ads, int fd,
 513                      int revent, int pollflag,
 514                      int maxfd, const fd_set *fds,
 515                      int (*func)(adns_state, int fd,
 516                                  const struct timeval *now),
 517                      struct timeval now, int *r_r) {
 518   int r;
 519
 520   if (!(revent & pollflag)) return;
 521   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 522   r= func(ads,fd,&now);
 523   if (r) {
 524     if (r_r) {
 525       *r_r= r;
 526     } else {
 527       adns__diag(ads,-1,0,"process fd failed after select:"
 528                  " %s",strerror(errno));
 529       adns_globalsystemfailure(ads);
 530     }
 531   }
 532 }
 533
 534 void adns__fdevents(adns_state ads,
 535                     const struct pollfd *pollfds, int npollfds,
 536                     int maxfd, const fd_set *readfds,
 537                     const fd_set *writefds, const fd_set *exceptfds,
 538                     struct timeval now, int *r_r) {
 539   int i, fd, revents;
 540
 541   for (i=0; i<npollfds; i++) {
 542     fd= pollfds[i].fd;
 543     if (fd >= maxfd) maxfd= fd+1;
 544     revents= pollfds[i].revents;
 545 #define EV(pollfl,fds,how)  \
 546     fd_event(ads,fd, revents,pollfl, maxfd,fds, adns_process##how,now,r_r)
 547     EV( POLLIN,  readfds,   readable    );
 548     EV( POLLOUT, writefds,  writeable   );
 549     EV( POLLPRI, exceptfds, exceptional );
 550 #undef EV
 551   }
 552 }
 553
 554 /* Wrappers for select(2). */
 555
 556 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 557                        fd_set *writefds_io, fd_set *exceptfds_io,
 558                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 559                        const struct timeval *now) {
 560   struct timeval tv_nowbuf;
 561   struct pollfd pollfds[MAX_POLLFDS];
 562   int i, fd, maxfd, npollfds;
 563
 564   adns__consistency(ads,0,cc_entex);
 565
 566   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 567     /* The caller is planning to sleep. */
 568     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 569     if (!now) { inter_immed(tv_mod,tv_tobuf); goto xit; }
 570     adns__timeouts(ads, 0, tv_mod,tv_tobuf, *now);
 571   }
 572
 573   npollfds= adns__pollfds(ads,pollfds);
 574   maxfd= *maxfd_io;
 575   for (i=0; i<npollfds; i++) {
 576     fd= pollfds[i].fd;
 577     if (fd >= maxfd) maxfd= fd+1;
 578     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 579     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 580     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 581   }
 582   *maxfd_io= maxfd;
 583
 584 xit:
 585   adns__consistency(ads,0,cc_entex);
 586 }
 587
 588 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 589                       const fd_set *writefds, const fd_set *exceptfds,
 590                       const struct timeval *now) {
 591   struct timeval tv_buf;
 592   struct pollfd pollfds[MAX_POLLFDS];
 593   int npollfds, i;
 594
 595   adns__consistency(ads,0,cc_entex);
 596   adns__must_gettimeofday(ads,&now,&tv_buf);
 597   if (!now) goto xit;
 598   adns_processtimeouts(ads,now);
 599
 600   npollfds= adns__pollfds(ads,pollfds);
 601   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 602   adns__fdevents(ads,
 603                  pollfds,npollfds,
 604                  maxfd,readfds,writefds,exceptfds,
 605                  *now, 0);
 606 xit:
 607   adns__consistency(ads,0,cc_entex);
 608 }
 609
 610 /* General helpful functions. */
 611
 612 void adns_globalsystemfailure(adns_state ads) {
 613   adns__consistency(ads,0,cc_entex);
 614
 615   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 616   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 617
 618   switch (ads->tcpstate) {
 619   case server_connecting:
 620   case server_ok:
 621     adns__tcp_broken(ads,0,0);
 622     break;
 623   case server_disconnected:
 624   case server_broken:
 625     break;
 626   default:
 627     abort();
 628   }
 629   adns__consistency(ads,0,cc_entex);
 630 }
 631
 632 int adns_processany(adns_state ads) {
 633   int r, i;
 634   struct timeval now;
 635   struct pollfd pollfds[MAX_POLLFDS];
 636   int npollfds;
 637
 638   adns__consistency(ads,0,cc_entex);
 639
 640   r= gettimeofday(&now,0);
 641   if (!r) adns_processtimeouts(ads,&now);
 642
 643   /* We just use adns__fdevents to loop over the fd's trying them.
 644    * This seems more sensible than calling select, since we're most
 645    * likely just to want to do a read on one or two fds anyway.
 646    */
 647   npollfds= adns__pollfds(ads,pollfds);
 648   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events & ~POLLPRI;
 649   adns__fdevents(ads,
 650                  pollfds,npollfds,
 651                  0,0,0,0,
 652                  now,&r);
 653
 654   adns__consistency(ads,0,cc_entex);
 655   return 0;
 656 }
 657
 658 void adns__autosys(adns_state ads, struct timeval now) {
 659   if (ads->iflags & adns_if_noautosys) return;
 660   adns_processany(ads);
 661 }
 662
 663 int adns__internal_check(adns_state ads,
 664                          adns_query *query_io,
 665                          adns_answer **answer,
 666                          void **context_r) {
 667   adns_query qu;
 668
 669   qu= *query_io;
 670   if (!qu) {
 671     if (ads->output.head) {
 672       qu= ads->output.head;
 673     } else if (ads->udpw.head || ads->tcpw.head) {
 674       return EAGAIN;
 675     } else {
 676       return ESRCH;
 677     }
 678   } else {
 679     if (qu->id>=0) return EAGAIN;
 680   }
 681   LIST_UNLINK(ads->output,qu);
 682   *answer= qu->answer;
 683   if (context_r) *context_r= qu->ctx.ext;
 684   *query_io= qu;
 685   free(qu);
 686   return 0;
 687 }
 688
 689 int adns_wait(adns_state ads,
 690               adns_query *query_io,
 691               adns_answer **answer_r,
 692               void **context_r) {
 693   int r, maxfd, rsel;
 694   fd_set readfds, writefds, exceptfds;
 695   struct timeval tvbuf, *tvp;
 696
 697   adns__consistency(ads,*query_io,cc_entex);
 698   for (;;) {
 699     r= adns__internal_check(ads,query_io,answer_r,context_r);
 700     if (r != EAGAIN) break;
 701     maxfd= 0; tvp= 0;
 702     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 703     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 704     assert(tvp);
 705     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 706     if (rsel==-1) {
 707       if (errno == EINTR) {
 708         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 709       } else {
 710         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 711         adns_globalsystemfailure(ads);
 712       }
 713     } else {
 714       assert(rsel >= 0);
 715       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 716     }
 717   }
 718   adns__consistency(ads,0,cc_entex);
 719   return r;
 720 }
 721
 722 int adns_check(adns_state ads,
 723                adns_query *query_io,
 724                adns_answer **answer_r,
 725                void **context_r) {
 726   struct timeval now;
 727   int r;
 728
 729   adns__consistency(ads,*query_io,cc_entex);
 730   r= gettimeofday(&now,0);
 731   if (!r) adns__autosys(ads,now);
 732
 733   r= adns__internal_check(ads,query_io,answer_r,context_r);
 734   adns__consistency(ads,0,cc_entex);
 735   return r;
 736 }