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   int serv;
  47
  48   serv= ads->tcpserver;
  49   close(ads->tcpsocket);
  50   ads->tcpsocket= -1;
  51   ads->tcprecv.used= ads->tcprecv_skip= ads->tcpsend.used= 0;
  52 }
  53
  54 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  55   int serv;
  56   adns_query qu;
  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   if (ads->tcpstate == server_connecting) {
  63     /* Counts as a retry for all the queries waiting for TCP. */
  64     for (qu= ads->tcpw.head; qu; qu= qu->next)
  65       qu->retries++;
  66   }
  67
  68   tcp_close(ads);
  69   ads->tcpstate= server_broken;
  70   ads->tcpserver= (serv+1)%ads->nservers;
  71 }
  72
  73 static void tcp_connected(adns_state ads, struct timeval now) {
  74   adns_query qu, nqu;
  75
  76   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  77   ads->tcpstate= server_ok;
  78   for (qu= ads->tcpw.head; qu && ads->tcpstate == server_ok; qu= nqu) {
  79     nqu= qu->next;
  80     assert(qu->state == query_tcpw);
  81     adns__querysend_tcp(qu,now);
  82   }
  83 }
  84
  85 static void tcp_broken_events(adns_state ads) {
  86   adns_query qu, nqu;
  87
  88   assert(ads->tcpstate == server_broken);
  89   for (qu= ads->tcpw.head; qu; qu= nqu) {
  90     nqu= qu->next;
  91     assert(qu->state == query_tcpw);
  92     if (qu->retries > ads->nservers) {
  93       LIST_UNLINK(ads->tcpw,qu);
  94       adns__query_fail(qu,adns_s_allservfail);
  95     }
  96   }
  97   ads->tcpstate= server_disconnected;
  98 }
  99
 100 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
 101   int r, fd, tries;
 102   adns_rr_addr *addr;
 103   struct protoent *proto;
 104
 105   for (tries=0; tries<ads->nservers; tries++) {
 106     switch (ads->tcpstate) {
 107     case server_connecting:
 108     case server_ok:
 109     case server_broken:
 110       return;
 111     case server_disconnected:
 112       break;
 113     default:
 114       abort();
 115     }
 116
 117     assert(!ads->tcpsend.used);
 118     assert(!ads->tcprecv.used);
 119     assert(!ads->tcprecv_skip);
 120
 121     proto= getprotobyname("tcp");
 122     if (!proto) {
 123       adns__diag(ads,-1,0,"unable to find protocol no. for TCP !");
 124       return;
 125     }
 126     addr = &ads->servers[ads->tcpserver];
 127     fd= socket(addr->addr.sa.sa_family, SOCK_STREAM, proto->p_proto);
 128     if (fd<0) {
 129       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 130       return;
 131     }
 132     r= adns__setnonblock(ads,fd);
 133     if (r) {
 134       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking:"
 135                  " %s",strerror(r));
 136       close(fd);
 137       return;
 138     }
 139     r= connect(fd,&addr->addr.sa,addr->len);
 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   int i;
 312
 313   assert(MAX_POLLFDS == MAXUDP + 1);
 314
 315   for (i = 0; i < ads->nudp; i++) {
 316     pollfds_buf[i].fd= ads->udpsocket[i].fd;
 317     pollfds_buf[i].events= POLLIN;
 318     pollfds_buf[i].revents= 0;
 319   }
 320
 321   switch (ads->tcpstate) {
 322   case server_disconnected:
 323   case server_broken:
 324     return 1;
 325   case server_connecting:
 326     pollfds_buf[i].events= POLLOUT;
 327     break;
 328   case server_ok:
 329     pollfds_buf[i].events=
 330       ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 331     break;
 332   default:
 333     abort();
 334   }
 335   pollfds_buf[i++].fd= ads->tcpsocket;
 336   return i;
 337 }
 338
 339 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 340   int want, dgramlen, r, i, udpaddrlen, serv, old_skip;
 341   byte udpbuf[DNS_MAXUDP];
 342   char addrbuf[MAX_ADDRSTRLEN];
 343   struct udpsocket *udp;
 344   adns_sockaddr udpaddr;
 345
 346   adns__consistency(ads,0,cc_entex);
 347
 348   switch (ads->tcpstate) {
 349   case server_disconnected:
 350   case server_broken:
 351   case server_connecting:
 352     break;
 353   case server_ok:
 354     if (fd != ads->tcpsocket) break;
 355     assert(!ads->tcprecv_skip);
 356     do {
 357       if (ads->tcprecv.used >= ads->tcprecv_skip+2) {
 358         dgramlen= ((ads->tcprecv.buf[ads->tcprecv_skip]<<8) |
 359                    ads->tcprecv.buf[ads->tcprecv_skip+1]);
 360         if (ads->tcprecv.used >= ads->tcprecv_skip+2+dgramlen) {
 361           old_skip= ads->tcprecv_skip;
 362           ads->tcprecv_skip += 2+dgramlen;
 363           adns__procdgram(ads, ads->tcprecv.buf+old_skip+2,
 364                           dgramlen, ads->tcpserver, 1,*now);
 365           continue;
 366         } else {
 367           want= 2+dgramlen;
 368         }
 369       } else {
 370         want= 2;
 371       }
 372       ads->tcprecv.used -= ads->tcprecv_skip;
 373       memmove(ads->tcprecv.buf, ads->tcprecv.buf+ads->tcprecv_skip,
 374               ads->tcprecv.used);
 375       ads->tcprecv_skip= 0;
 376       if (!adns__vbuf_ensure(&ads->tcprecv,want)) { r= ENOMEM; goto xit; }
 377       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 378       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 379       r= read(ads->tcpsocket,
 380               ads->tcprecv.buf+ads->tcprecv.used,
 381               ads->tcprecv.avail-ads->tcprecv.used);
 382       if (r>0) {
 383         ads->tcprecv.used+= r;
 384       } else {
 385         if (r) {
 386           if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 387           if (errno==EINTR) continue;
 388           if (errno_resources(errno)) { r= errno; goto xit; }
 389         }
 390         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 391       }
 392     } while (ads->tcpstate == server_ok);
 393     r= 0; goto xit;
 394   default:
 395     abort();
 396   }
 397   for (i = 0; i < ads->nudp; i++) {
 398     udp = &ads->udpsocket[i];
 399     if (fd == udp->fd) {
 400       for (;;) {
 401         udpaddrlen= sizeof(udpaddr);
 402         r= recvfrom(fd,udpbuf,sizeof(udpbuf),0, &udpaddr.sa,&udpaddrlen);
 403         if (r<0) {
 404           if (errno == EAGAIN || errno == EWOULDBLOCK) { r= 0; goto xit; }
 405           if (errno == EINTR) continue;
 406           if (errno_resources(errno)) { r= errno; goto xit; }
 407           adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 408           r= 0; goto xit;
 409         }
 410         for (serv= 0;
 411              serv < ads->nservers &&
 412                !adns__sockaddr_equal_p(&udpaddr.sa,
 413                                        &ads->servers[serv].addr.sa);
 414              serv++);
 415         if (serv >= ads->nservers) {
 416           adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 417                      adns__sockaddr_ntoa(&udpaddr.sa, udpaddrlen, addrbuf));
 418           continue;
 419         }
 420         adns__procdgram(ads,udpbuf,r,serv,0,*now);
 421       }
 422       break;
 423     }
 424   }
 425   r= 0;
 426 xit:
 427   adns__consistency(ads,0,cc_entex);
 428   return r;
 429 }
 430
 431 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 432   int r;
 433
 434   adns__consistency(ads,0,cc_entex);
 435
 436   switch (ads->tcpstate) {
 437   case server_disconnected:
 438   case server_broken:
 439     break;
 440   case server_connecting:
 441     if (fd != ads->tcpsocket) break;
 442     assert(ads->tcprecv.used==0);
 443     assert(ads->tcprecv_skip==0);
 444     for (;;) {
 445       if (!adns__vbuf_ensure(&ads->tcprecv,1)) { r= ENOMEM; goto xit; }
 446       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 447       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 448         tcp_connected(ads,*now);
 449         r= 0; goto xit;
 450       }
 451       if (r>0) {
 452         adns__tcp_broken(ads,"connect/read","sent data before first request");
 453         r= 0; goto xit;
 454       }
 455       if (errno==EINTR) continue;
 456       if (errno_resources(errno)) { r= errno; goto xit; }
 457       adns__tcp_broken(ads,"connect/read",strerror(errno));
 458       r= 0; goto xit;
 459     } /* not reached */
 460   case server_ok:
 461     if (fd != ads->tcpsocket) break;
 462     while (ads->tcpsend.used) {
 463       adns__sigpipe_protect(ads);
 464       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 465       adns__sigpipe_unprotect(ads);
 466       if (r<0) {
 467         if (errno==EINTR) continue;
 468         if (errno==EAGAIN || errno==EWOULDBLOCK) { r= 0; goto xit; }
 469         if (errno_resources(errno)) { r= errno; goto xit; }
 470         adns__tcp_broken(ads,"write",strerror(errno));
 471         r= 0; goto xit;
 472       } else if (r>0) {
 473         ads->tcpsend.used -= r;
 474         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 475       }
 476     }
 477     r= 0;
 478     goto xit;
 479   default:
 480     abort();
 481   }
 482   r= 0;
 483 xit:
 484   adns__consistency(ads,0,cc_entex);
 485   return r;
 486 }
 487
 488 int adns_processexceptional(adns_state ads, int fd,
 489                             const struct timeval *now) {
 490   adns__consistency(ads,0,cc_entex);
 491   switch (ads->tcpstate) {
 492   case server_disconnected:
 493   case server_broken:
 494     break;
 495   case server_connecting:
 496   case server_ok:
 497     if (fd != ads->tcpsocket) break;
 498     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 499     break;
 500   default:
 501     abort();
 502   }
 503   adns__consistency(ads,0,cc_entex);
 504   return 0;
 505 }
 506
 507 static void fd_event(adns_state ads, int fd,
 508                      int revent, int pollflag,
 509                      int maxfd, const fd_set *fds,
 510                      int (*func)(adns_state, int fd,
 511                                  const struct timeval *now),
 512                      struct timeval now, int *r_r) {
 513   int r;
 514
 515   if (!(revent & pollflag)) return;
 516   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 517   r= func(ads,fd,&now);
 518   if (r) {
 519     if (r_r) {
 520       *r_r= r;
 521     } else {
 522       adns__diag(ads,-1,0,"process fd failed after select:"
 523                  " %s",strerror(errno));
 524       adns_globalsystemfailure(ads);
 525     }
 526   }
 527 }
 528
 529 void adns__fdevents(adns_state ads,
 530                     const struct pollfd *pollfds, int npollfds,
 531                     int maxfd, const fd_set *readfds,
 532                     const fd_set *writefds, const fd_set *exceptfds,
 533                     struct timeval now, int *r_r) {
 534   int i, fd, revents;
 535
 536   for (i=0; i<npollfds; i++) {
 537     fd= pollfds[i].fd;
 538     if (fd >= maxfd) maxfd= fd+1;
 539     revents= pollfds[i].revents;
 540 #define EV(pollfl,fds,how)  \
 541     fd_event(ads,fd, revents,pollfl, maxfd,fds, adns_process##how,now,r_r)
 542     EV( POLLIN,  readfds,   readable    );
 543     EV( POLLOUT, writefds,  writeable   );
 544     EV( POLLPRI, exceptfds, exceptional );
 545 #undef EV
 546   }
 547 }
 548
 549 /* Wrappers for select(2). */
 550
 551 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 552                        fd_set *writefds_io, fd_set *exceptfds_io,
 553                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 554                        const struct timeval *now) {
 555   struct timeval tv_nowbuf;
 556   struct pollfd pollfds[MAX_POLLFDS];
 557   int i, fd, maxfd, npollfds;
 558
 559   adns__consistency(ads,0,cc_entex);
 560
 561   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 562     /* The caller is planning to sleep. */
 563     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 564     if (!now) { inter_immed(tv_mod,tv_tobuf); goto xit; }
 565     adns__timeouts(ads, 0, tv_mod,tv_tobuf, *now);
 566   }
 567
 568   npollfds= adns__pollfds(ads,pollfds);
 569   maxfd= *maxfd_io;
 570   for (i=0; i<npollfds; i++) {
 571     fd= pollfds[i].fd;
 572     if (fd >= maxfd) maxfd= fd+1;
 573     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 574     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 575     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 576   }
 577   *maxfd_io= maxfd;
 578
 579 xit:
 580   adns__consistency(ads,0,cc_entex);
 581 }
 582
 583 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 584                       const fd_set *writefds, const fd_set *exceptfds,
 585                       const struct timeval *now) {
 586   struct timeval tv_buf;
 587   struct pollfd pollfds[MAX_POLLFDS];
 588   int npollfds, i;
 589
 590   adns__consistency(ads,0,cc_entex);
 591   adns__must_gettimeofday(ads,&now,&tv_buf);
 592   if (!now) goto xit;
 593   adns_processtimeouts(ads,now);
 594
 595   npollfds= adns__pollfds(ads,pollfds);
 596   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 597   adns__fdevents(ads,
 598                  pollfds,npollfds,
 599                  maxfd,readfds,writefds,exceptfds,
 600                  *now, 0);
 601 xit:
 602   adns__consistency(ads,0,cc_entex);
 603 }
 604
 605 /* General helpful functions. */
 606
 607 void adns_globalsystemfailure(adns_state ads) {
 608   adns__consistency(ads,0,cc_entex);
 609
 610   while (ads->udpw.head) adns__query_fail(ads->udpw.head, adns_s_systemfail);
 611   while (ads->tcpw.head) adns__query_fail(ads->tcpw.head, adns_s_systemfail);
 612
 613   switch (ads->tcpstate) {
 614   case server_connecting:
 615   case server_ok:
 616     adns__tcp_broken(ads,0,0);
 617     break;
 618   case server_disconnected:
 619   case server_broken:
 620     break;
 621   default:
 622     abort();
 623   }
 624   adns__consistency(ads,0,cc_entex);
 625 }
 626
 627 int adns_processany(adns_state ads) {
 628   int r, i;
 629   struct timeval now;
 630   struct pollfd pollfds[MAX_POLLFDS];
 631   int npollfds;
 632
 633   adns__consistency(ads,0,cc_entex);
 634
 635   r= gettimeofday(&now,0);
 636   if (!r) adns_processtimeouts(ads,&now);
 637
 638   /* We just use adns__fdevents to loop over the fd's trying them.
 639    * This seems more sensible than calling select, since we're most
 640    * likely just to want to do a read on one or two fds anyway.
 641    */
 642   npollfds= adns__pollfds(ads,pollfds);
 643   for (i=0; i<npollfds; i++) pollfds[i].revents= pollfds[i].events & ~POLLPRI;
 644   adns__fdevents(ads,
 645                  pollfds,npollfds,
 646                  0,0,0,0,
 647                  now,&r);
 648
 649   adns__consistency(ads,0,cc_entex);
 650   return 0;
 651 }
 652
 653 void adns__autosys(adns_state ads, struct timeval now) {
 654   if (ads->iflags & adns_if_noautosys) return;
 655   adns_processany(ads);
 656 }
 657
 658 int adns__internal_check(adns_state ads,
 659                          adns_query *query_io,
 660                          adns_answer **answer,
 661                          void **context_r) {
 662   adns_query qu;
 663
 664   qu= *query_io;
 665   if (!qu) {
 666     if (ads->output.head) {
 667       qu= ads->output.head;
 668     } else if (ads->udpw.head || ads->tcpw.head) {
 669       return EAGAIN;
 670     } else {
 671       return ESRCH;
 672     }
 673   } else {
 674     if (qu->id>=0) return EAGAIN;
 675   }
 676   LIST_UNLINK(ads->output,qu);
 677   *answer= qu->answer;
 678   if (context_r) *context_r= qu->ctx.ext;
 679   *query_io= qu;
 680   free(qu);
 681   return 0;
 682 }
 683
 684 int adns_wait(adns_state ads,
 685               adns_query *query_io,
 686               adns_answer **answer_r,
 687               void **context_r) {
 688   int r, maxfd, rsel;
 689   fd_set readfds, writefds, exceptfds;
 690   struct timeval tvbuf, *tvp;
 691
 692   adns__consistency(ads,*query_io,cc_entex);
 693   for (;;) {
 694     r= adns__internal_check(ads,query_io,answer_r,context_r);
 695     if (r != EAGAIN) break;
 696     maxfd= 0; tvp= 0;
 697     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 698     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 699     assert(tvp);
 700     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 701     if (rsel==-1) {
 702       if (errno == EINTR) {
 703         if (ads->iflags & adns_if_eintr) { r= EINTR; break; }
 704       } else {
 705         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 706         adns_globalsystemfailure(ads);
 707       }
 708     } else {
 709       assert(rsel >= 0);
 710       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 711     }
 712   }
 713   adns__consistency(ads,0,cc_entex);
 714   return r;
 715 }
 716
 717 int adns_check(adns_state ads,
 718                adns_query *query_io,
 719                adns_answer **answer_r,
 720                void **context_r) {
 721   struct timeval now;
 722   int r;
 723
 724   adns__consistency(ads,*query_io,cc_entex);
 725   r= gettimeofday(&now,0);
 726   if (!r) adns__autosys(ads,now);
 727
 728   r= adns__internal_check(ads,query_io,answer_r,context_r);
 729   adns__consistency(ads,0,cc_entex);
 730   return r;
 731 }