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 Copyright (C) 1997-1999 Ian Jackson
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License as published by
  12  *  the Free Software Foundation; either version 2, or (at your option)
  13  *  any later version.
  14  *
  15  *  This program is distributed in the hope that it will be useful,
  16  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  *  GNU General Public License for more details.
  19  *
  20  *  You should have received a copy of the GNU General Public License
  21  *  along with this program; if not, write to the Free Software Foundation,
  22  *  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23  */
  24
  25 #include <errno.h>
  26 #include <stdlib.h>
  27 #include <unistd.h>
  28
  29 #include <sys/types.h>
  30 #include <sys/time.h>
  31 #include <netdb.h>
  32 #include <sys/socket.h>
  33 #include <netinet/in.h>
  34 #include <arpa/inet.h>
  35
  36 #include "internal.h"
  37
  38 /* TCP connection management. */
  39
  40 void adns__tcp_closenext(adns_state ads) {
  41   int serv;
  42
  43   serv= ads->tcpserver;
  44   close(ads->tcpsocket);
  45   ads->tcpstate= server_disconnected;
  46   ads->tcprecv.used= ads->tcpsend.used= 0;
  47   ads->tcpserver= (serv+1)%ads->nservers;
  48 }
  49
  50 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  51   int serv;
  52   adns_query qu, nqu;
  53
  54   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  55   serv= ads->tcpserver;
  56   adns__warn(ads,serv,0,"TCP connection lost: %s: %s",what,why);
  57   adns__tcp_closenext(ads);
  58
  59   for (qu= ads->timew.head; qu; qu= nqu) {
  60     nqu= qu->next;
  61     if (qu->state == query_tosend) continue;
  62     assert(qu->state == query_tcpwait || qu->state == query_tcpsent);
  63     qu->state= query_tcpwait;
  64     qu->tcpfailed |= (1<<serv);
  65     if (qu->tcpfailed == (1<<ads->nservers)-1) {
  66       LIST_UNLINK(ads->timew,qu);
  67       adns__query_fail(qu,adns_s_allservfail);
  68     }
  69   }
  70 }
  71
  72 static void tcp_connected(adns_state ads, struct timeval now) {
  73   adns_query qu, nqu;
  74
  75   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  76   ads->tcpstate= server_ok;
  77   for (qu= ads->timew.head; qu; qu= nqu) {
  78     nqu= qu->next;
  79     if (qu->state == query_tosend) continue;
  80     assert (qu->state == query_tcpwait);
  81     adns__query_tcp(qu,now);
  82   }
  83 }
  84
  85 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  86   int r, fd, tries;
  87   struct sockaddr_in addr;
  88   struct protoent *proto;
  89
  90   for (tries=0; tries<ads->nservers; tries++) {
  91     if (ads->tcpstate == server_connecting || ads->tcpstate == server_ok) return;
  92     assert(ads->tcpstate == server_disconnected);
  93     assert(!ads->tcpsend.used);
  94     assert(!ads->tcprecv.used);
  95
  96     proto= getprotobyname("tcp");
  97     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
  98     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
  99     if (fd<0) {
 100       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
 101       return;
 102     }
 103     r= adns__setnonblock(ads,fd);
 104     if (r) {
 105       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
 106       close(fd);
 107       return;
 108     }
 109     memset(&addr,0,sizeof(addr));
 110     addr.sin_family= AF_INET;
 111     addr.sin_port= htons(DNS_PORT);
 112     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 113     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 114     ads->tcpsocket= fd;
 115     ads->tcpstate= server_connecting;
 116     if (r==0) { tcp_connected(ads,now); continue; }
 117     if (errno == EWOULDBLOCK || errno == EINPROGRESS) return;
 118     adns__tcp_broken(ads,"connect",strerror(errno));
 119   }
 120 }
 121
 122 /* Timeout handling functions. */
 123
 124 void adns__must_gettimeofday(adns_state ads, const struct timeval **now_io,
 125                              struct timeval *tv_buf) {
 126   const struct timeval *now;
 127   int r;
 128
 129   now= *now_io;
 130   if (now) return;
 131   r= gettimeofday(tv_buf,0); if (!r) { *now_io= tv_buf; return; }
 132   adns__diag(ads,-1,0,"gettimeofday failed: %s",strerror(errno));
 133   adns_globalsystemfailure(ads);
 134   return;
 135 }
 136
 137 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 138                         struct timeval maxto) {
 139   struct timeval *rbuf;
 140
 141   if (!tv_io) return;
 142   rbuf= *tv_io;
 143   if (!rbuf) {
 144     *tvbuf= maxto; *tv_io= tvbuf;
 145   } else {
 146     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 147   }
 148 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 149         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 150 }
 151
 152 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 153                            struct timeval now, struct timeval maxtime) {
 154   ldiv_t dr;
 155
 156 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 157         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 158   if (!tv_io) return;
 159   maxtime.tv_sec -= (now.tv_sec+2);
 160   maxtime.tv_usec -= (now.tv_usec-2000000);
 161   dr= ldiv(maxtime.tv_usec,1000000);
 162   maxtime.tv_sec += dr.quot;
 163   maxtime.tv_usec -= dr.quot*1000000;
 164   if (maxtime.tv_sec<0) timerclear(&maxtime);
 165   inter_maxto(tv_io,tvbuf,maxtime);
 166 }
 167
 168 void adns__timeouts(adns_state ads, int act,
 169                     struct timeval **tv_io, struct timeval *tvbuf,
 170                     struct timeval now) {
 171   adns_query qu, nqu;
 172
 173   for (qu= ads->timew.head; qu; qu= nqu) {
 174     nqu= qu->next;
 175     if (!timercmp(&now,&qu->timeout,>)) {
 176       if (!tv_io) continue;
 177       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 178     } else {
 179       if (!act) continue;
 180       LIST_UNLINK(ads->timew,qu);
 181       if (qu->state != query_tosend) {
 182         adns__query_fail(qu,adns_s_timeout);
 183       } else {
 184         adns__query_send(qu,now);
 185       }
 186       nqu= ads->timew.head;
 187     }
 188   }
 189 }
 190
 191 void adns_firsttimeout(adns_state ads,
 192                        struct timeval **tv_io, struct timeval *tvbuf,
 193                        struct timeval now) {
 194   adns__timeouts(ads, 0, tv_io,tvbuf, now);
 195 }
 196
 197 void adns_processtimeouts(adns_state ads, const struct timeval *now) {
 198   struct timeval tv_buf;
 199
 200   adns__must_gettimeofday(ads,&now,&tv_buf); if (!now) return;
 201   adns__timeouts(ads, 1, 0,0, *now);
 202 }
 203
 204 /* fd handling functions.  These are the top-level of the real work of
 205  * reception and often transmission.
 206  */
 207
 208 int adns__pollfds(adns_state ads, struct pollfd pollfds_buf[MAX_POLLFDS]) {
 209   /* Returns the number of entries filled in.  Always zeroes revents. */
 210
 211   assert(MAX_POLLFDS==2);
 212
 213   pollfds_buf[0].fd= ads->udpsocket;
 214   pollfds_buf[0].events= POLLIN;
 215   pollfds_buf[0].revents= 0;
 216
 217   switch (ads->tcpstate) {
 218   case server_disconnected:
 219     return 1;
 220   case server_connecting:
 221     pollfds_buf[1].events= POLLOUT;
 222     break;
 223   case server_ok:
 224     pollfds_buf[1].events= ads->tcpsend.used ? POLLIN|POLLOUT|POLLPRI : POLLIN|POLLPRI;
 225     break;
 226   default:
 227     abort();
 228   }
 229   pollfds_buf[1].fd= ads->tcpsocket;
 230   return 2;
 231 }
 232
 233 int adns_processreadable(adns_state ads, int fd, const struct timeval *now) {
 234   int skip, want, dgramlen, r, udpaddrlen, serv;
 235   byte udpbuf[DNS_MAXUDP];
 236   struct sockaddr_in udpaddr;
 237
 238   switch (ads->tcpstate) {
 239   case server_disconnected:
 240   case server_connecting:
 241     break;
 242   case server_ok:
 243     if (fd != ads->tcpsocket) break;
 244     skip= 0;
 245     for (;;) {
 246       if (ads->tcprecv.used<skip+2) {
 247         want= 2;
 248       } else {
 249         dgramlen= (ads->tcprecv.buf[skip]<<8) | ads->tcprecv.buf[skip+1];
 250         if (ads->tcprecv.used<skip+2+dgramlen) {
 251           want= 2+dgramlen;
 252         } else {
 253           adns__procdgram(ads,ads->tcprecv.buf+skip+2,dgramlen,ads->tcpserver,1,*now);
 254           skip+= 2+dgramlen; continue;
 255         }
 256       }
 257       ads->tcprecv.used -= skip;
 258       memmove(ads->tcprecv.buf,ads->tcprecv.buf+skip,ads->tcprecv.used);
 259       skip= 0;
 260       if (!adns__vbuf_ensure(&ads->tcprecv,want)) return ENOMEM;
 261       assert(ads->tcprecv.used <= ads->tcprecv.avail);
 262       if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 263       r= read(ads->tcpsocket,
 264               ads->tcprecv.buf+ads->tcprecv.used,
 265               ads->tcprecv.avail-ads->tcprecv.used);
 266       if (r>0) {
 267         ads->tcprecv.used+= r;
 268       } else {
 269         if (r) {
 270           if (errno==EAGAIN || errno==EWOULDBLOCK) return 0;
 271           if (errno==EINTR) continue;
 272           if (errno_resources(errno)) return errno;
 273         }
 274         adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 275         return 0;
 276       }
 277     } /* never reached */
 278   default:
 279     abort();
 280   }
 281   if (fd == ads->udpsocket) {
 282     for (;;) {
 283       udpaddrlen= sizeof(udpaddr);
 284       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 285                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 286       if (r<0) {
 287         if (errno == EAGAIN || errno == EWOULDBLOCK) return 0;
 288         if (errno == EINTR) continue;
 289         if (errno_resources(errno)) return errno;
 290         adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 291         return 0;
 292       }
 293       if (udpaddrlen != sizeof(udpaddr)) {
 294         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 295                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 296         continue;
 297       }
 298       if (udpaddr.sin_family != AF_INET) {
 299         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 300                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 301         continue;
 302       }
 303       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 304         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 305                    ntohs(udpaddr.sin_port),DNS_PORT);
 306         continue;
 307       }
 308       for (serv= 0;
 309            serv < ads->nservers &&
 310              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 311            serv++);
 312       if (serv >= ads->nservers) {
 313         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 314                    inet_ntoa(udpaddr.sin_addr));
 315         continue;
 316       }
 317       adns__procdgram(ads,udpbuf,r,serv,0,*now);
 318     }
 319   }
 320   return 0;
 321 }
 322
 323 int adns_processwriteable(adns_state ads, int fd, const struct timeval *now) {
 324   int r;
 325
 326   switch (ads->tcpstate) {
 327   case server_disconnected:
 328     break;
 329   case server_connecting:
 330     if (fd != ads->tcpsocket) break;
 331     assert(ads->tcprecv.used==0);
 332     for (;;) {
 333       if (!adns__vbuf_ensure(&ads->tcprecv,1)) return ENOMEM;
 334       r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 335       if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 336         tcp_connected(ads,*now);
 337         return 0;
 338       }
 339       if (r>0) {
 340         adns__tcp_broken(ads,"connect/read","sent data before first request");
 341         return 0;
 342       }
 343       if (errno==EINTR) continue;
 344       if (errno_resources(errno)) return errno;
 345       adns__tcp_broken(ads,"connect/read",strerror(errno));
 346       return 0;
 347     } /* not reached */
 348   case server_ok:
 349     if (!(ads->tcpsend.used && fd == ads->tcpsocket)) break;
 350     for (;;) {
 351       adns__sigpipe_protect(ads);
 352       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 353       adns__sigpipe_unprotect(ads);
 354       if (r<0) {
 355         if (errno==EINTR) continue;
 356         if (errno==EAGAIN || errno==EWOULDBLOCK) return 0;
 357         if (errno_resources(errno)) return errno;
 358         adns__tcp_broken(ads,"write",strerror(errno));
 359         return 0;
 360       } else if (r>0) {
 361         ads->tcpsend.used -= r;
 362         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 363       }
 364     } /* not reached */
 365   default:
 366     abort();
 367   }
 368   return 0;
 369 }
 370
 371 int adns_processexceptional(adns_state ads, int fd, const struct timeval *now) {
 372   switch (ads->tcpstate) {
 373   case server_disconnected:
 374     break;
 375   case server_connecting:
 376   case server_ok:
 377     if (fd != ads->tcpsocket) break;
 378     adns__tcp_broken(ads,"poll/select","exceptional condition detected");
 379     return 0;
 380   default:
 381     abort();
 382   }
 383   return 0;
 384 }
 385
 386 static void fd_event(adns_state ads, int fd,
 387                      int revent, int pollflag,
 388                      int maxfd, const fd_set *fds,
 389                      int (*func)(adns_state, int fd, const struct timeval *now),
 390                      struct timeval now, int *r_r) {
 391   int r;
 392
 393   if (!(revent & pollflag)) return;
 394   if (fds && !(fd<maxfd && FD_ISSET(fd,fds))) return;
 395   r= func(ads,fd,&now);
 396   if (r) {
 397     if (r_r) {
 398       *r_r= r;
 399     } else {
 400       adns__diag(ads,-1,0,"process fd failed after select: %s",strerror(errno));
 401       adns_globalsystemfailure(ads);
 402     }
 403   }
 404 }
 405
 406 void adns__fdevents(adns_state ads,
 407                     const struct pollfd *pollfds, int npollfds,
 408                     int maxfd, const fd_set *readfds,
 409                     const fd_set *writefds, const fd_set *exceptfds,
 410                     struct timeval now, int *r_r) {
 411   int i, fd, revents;
 412
 413   for (i=0; i<npollfds; i++) {
 414     fd= pollfds[i].fd;
 415     if (fd >= maxfd) maxfd= fd+1;
 416     revents= pollfds[i].revents;
 417     fd_event(ads,fd, revents,POLLIN, maxfd,readfds, adns_processreadable,now,r_r);
 418     fd_event(ads,fd, revents,POLLOUT, maxfd,writefds, adns_processwriteable,now,r_r);
 419     fd_event(ads,fd, revents,POLLPRI, maxfd,exceptfds, adns_processexceptional,now,r_r);
 420   }
 421 }
 422
 423 /* Wrappers for select(2). */
 424
 425 void adns_beforeselect(adns_state ads, int *maxfd_io, fd_set *readfds_io,
 426                        fd_set *writefds_io, fd_set *exceptfds_io,
 427                        struct timeval **tv_mod, struct timeval *tv_tobuf,
 428                        const struct timeval *now) {
 429   struct timeval tv_nowbuf;
 430   struct pollfd pollfds[MAX_POLLFDS];
 431   int i, fd, maxfd, npollfds;
 432
 433   if (tv_mod && (!*tv_mod || (*tv_mod)->tv_sec || (*tv_mod)->tv_usec)) {
 434     /* The caller is planning to sleep. */
 435     adns__must_gettimeofday(ads,&now,&tv_nowbuf);
 436     if (!now) return;
 437     adns__timeouts(ads, 1, tv_mod,tv_tobuf, *now);
 438   }
 439
 440   npollfds= adns__pollfds(ads,pollfds);
 441   maxfd= *maxfd_io;
 442   for (i=0; i<npollfds; i++) {
 443     fd= pollfds[i].fd;
 444     if (fd >= maxfd) maxfd= fd+1;
 445     if (pollfds[i].events & POLLIN) FD_SET(fd,readfds_io);
 446     if (pollfds[i].events & POLLOUT) FD_SET(fd,writefds_io);
 447     if (pollfds[i].events & POLLPRI) FD_SET(fd,exceptfds_io);
 448   }
 449   *maxfd_io= maxfd;
 450 }
 451
 452 void adns_afterselect(adns_state ads, int maxfd, const fd_set *readfds,
 453                       const fd_set *writefds, const fd_set *exceptfds,
 454                       const struct timeval *now) {
 455   struct timeval tv_buf;
 456   struct pollfd pollfds[MAX_POLLFDS];
 457   int npollfds, i;
 458
 459   adns__must_gettimeofday(ads,&now,&tv_buf);
 460   if (!now) return;
 461   adns_processtimeouts(ads,now);
 462
 463   npollfds= adns__pollfds(ads,pollfds);
 464   for (i=0; i<npollfds; i++) pollfds[i].revents= POLLIN|POLLOUT|POLLPRI;
 465   adns__fdevents(ads,
 466                  pollfds,npollfds,
 467                  maxfd,readfds,writefds,exceptfds,
 468                  *now, 0);
 469 }
 470
 471 /* General helpful functions. */
 472
 473 void adns_globalsystemfailure(adns_state ads) {
 474   while (ads->timew.head) {
 475     adns__query_fail(ads->timew.head, adns_s_systemfail);
 476   }
 477
 478   switch (ads->tcpstate) {
 479   case server_connecting:
 480   case server_ok:
 481     adns__tcp_closenext(ads);
 482     break;
 483   case server_disconnected:
 484     break;
 485   default:
 486     abort();
 487   }
 488 }
 489
 490 int adns_processany(adns_state ads) {
 491   int r;
 492   struct timeval now;
 493   struct pollfd pollfds[MAX_POLLFDS];
 494   int npollfds;
 495
 496   r= gettimeofday(&now,0);
 497   if (!r) adns_processtimeouts(ads,&now);
 498
 499   npollfds= adns__pollfds(ads,pollfds);
 500   adns__fdevents(ads,
 501                  pollfds,npollfds,
 502                  0,0,0,0,
 503                  now,&r);
 504   return r;
 505 }
 506
 507 void adns__autosys(adns_state ads, struct timeval now) {
 508   if (ads->iflags & adns_if_noautosys) return;
 509   adns_processany(ads);
 510 }
 511
 512 static int internal_check(adns_state ads,
 513                           adns_query *query_io,
 514                           adns_answer **answer,
 515                           void **context_r) {
 516   adns_query qu;
 517
 518   qu= *query_io;
 519   if (!qu) {
 520     if (!ads->output.head) return EWOULDBLOCK;
 521     qu= ads->output.head;
 522   } else {
 523     if (qu->id>=0) return EWOULDBLOCK;
 524   }
 525   LIST_UNLINK(ads->output,qu);
 526   *answer= qu->answer;
 527   if (context_r) *context_r= qu->ctx.ext;
 528   *query_io= qu;
 529   free(qu);
 530   return 0;
 531 }
 532
 533 int adns_wait(adns_state ads,
 534               adns_query *query_io,
 535               adns_answer **answer_r,
 536               void **context_r) {
 537   int r, maxfd, rsel;
 538   fd_set readfds, writefds, exceptfds;
 539   struct timeval tvbuf, *tvp;
 540
 541   for (;;) {
 542     r= internal_check(ads,query_io,answer_r,context_r);
 543     if (r != EWOULDBLOCK) return r;
 544     maxfd= 0; tvp= 0;
 545     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 546     adns_beforeselect(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf,0);
 547     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 548     if (rsel==-1) {
 549       if (errno == EINTR) {
 550         if (ads->iflags & adns_if_eintr) return EINTR;
 551       } else {
 552         adns__diag(ads,-1,0,"select failed in wait: %s",strerror(errno));
 553         adns_globalsystemfailure(ads);
 554       }
 555     } else {
 556       assert(rsel >= 0);
 557       adns_afterselect(ads,maxfd,&readfds,&writefds,&exceptfds,0);
 558     }
 559   }
 560 }
 561
 562 int adns_check(adns_state ads,
 563                adns_query *query_io,
 564                adns_answer **answer_r,
 565                void **context_r) {
 566   struct timeval now;
 567   int r;
 568
 569   r= gettimeofday(&now,0);
 570   if (!r) adns__autosys(ads,now);
 571
 572   return internal_check(ads,query_io,answer_r,context_r);
 573 }