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