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