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_broken(adns_state ads, const char *what, const char *why) {
  42   int serv;
  43   adns_query qu, nqu;
  44
  45   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  46   serv= ads->tcpserver;
  47   adns__warn(ads,serv,0,"TCP connection lost: %s: %s",what,why);
  48   close(ads->tcpsocket);
  49   ads->tcpstate= server_disconnected;
  50
  51   for (qu= ads->timew.head; qu; qu= nqu) {
  52     nqu= qu->next;
  53     if (qu->state == query_udp) continue;
  54     assert(qu->state == query_tcpwait || qu->state == query_tcpsent);
  55     qu->state= query_tcpwait;
  56     qu->tcpfailed |= (1<<serv);
  57     if (qu->tcpfailed == (1<<ads->nservers)-1) {
  58       LIST_UNLINK(ads->timew,qu);
  59       adns__query_fail(qu,adns_s_allservfail);
  60     }
  61   }
  62
  63   ads->tcprecv.used= ads->tcpsend.used= 0;
  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->timew.head; qu; qu= nqu) {
  73     nqu= qu->next;
  74     if (qu->state == query_udp) continue;
  75     assert (qu->state == query_tcpwait);
  76     adns__query_tcp(qu,now);
  77   }
  78 }
  79
  80 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  81   int r, fd, tries;
  82   struct sockaddr_in addr;
  83   struct protoent *proto;
  84
  85   for (tries=0; tries<ads->nservers; tries++) {
  86     if (ads->tcpstate == server_connecting || ads->tcpstate == server_ok) return;
  87     assert(ads->tcpstate == server_disconnected);
  88     assert(!ads->tcpsend.used);
  89     assert(!ads->tcprecv.used);
  90
  91     proto= getprotobyname("tcp");
  92     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
  93     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
  94     if (fd<0) {
  95       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
  96       return;
  97     }
  98     r= adns__setnonblock(ads,fd);
  99     if (r) {
 100       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
 101       close(fd);
 102       return;
 103     }
 104     memset(&addr,0,sizeof(addr));
 105     addr.sin_family= AF_INET;
 106     addr.sin_port= htons(DNS_PORT);
 107     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 108     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 109     ads->tcpsocket= fd;
 110     ads->tcpstate= server_connecting;
 111     if (r==0) { tcp_connected(ads,now); continue; }
 112     if (errno == EWOULDBLOCK || errno == EINPROGRESS) return;
 113     adns__tcp_broken(ads,"connect",strerror(errno));
 114   }
 115 }
 116
 117 /* `Interest' functions - find out which fd's we might be interested in,
 118  * and when we want to be called back for a timeout.
 119  */
 120
 121 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 122                         struct timeval maxto) {
 123   struct timeval *rbuf;
 124
 125   if (!tv_io) return;
 126   rbuf= *tv_io;
 127   if (!rbuf) {
 128     *tvbuf= maxto; *tv_io= tvbuf;
 129   } else {
 130     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 131   }
 132 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 133         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 134 }
 135
 136 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 137                            struct timeval now, struct timeval maxtime) {
 138   ldiv_t dr;
 139
 140 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 141         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 142   if (!tv_io) return;
 143   maxtime.tv_sec -= (now.tv_sec+2);
 144   maxtime.tv_usec -= (now.tv_usec-2000000);
 145   dr= ldiv(maxtime.tv_usec,1000000);
 146   maxtime.tv_sec += dr.quot;
 147   maxtime.tv_usec -= dr.quot*1000000;
 148   if (maxtime.tv_sec<0) timerclear(&maxtime);
 149   inter_maxto(tv_io,tvbuf,maxtime);
 150 }
 151
 152 static void inter_addfd(int *maxfd, fd_set *fds, int fd) {
 153   if (!maxfd || !fds) return;
 154   if (fd>=*maxfd) *maxfd= fd+1;
 155   FD_SET(fd,fds);
 156 }
 157
 158 static void checktimeouts(adns_state ads, struct timeval now,
 159                           struct timeval **tv_io, struct timeval *tvbuf) {
 160   adns_query qu, nqu;
 161
 162   for (qu= ads->timew.head; qu; qu= nqu) {
 163     nqu= qu->next;
 164     if (timercmp(&now,&qu->timeout,>)) {
 165       LIST_UNLINK(ads->timew,qu);
 166       if (qu->state != query_udp) {
 167         adns__query_fail(qu,adns_s_timeout);
 168       } else {
 169         adns__query_udp(qu,now);
 170       }
 171     } else {
 172       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 173     }
 174   }
 175 }
 176
 177 void adns_interest(adns_state ads, int *maxfd,
 178                    fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
 179                    struct timeval **tv_io, struct timeval *tvbuf) {
 180   struct timeval now;
 181   struct timeval tvto_lr;
 182   int r;
 183
 184 /*fprintf(stderr,"adns_interest\n");*/
 185
 186   r= gettimeofday(&now,0);
 187   if (r) {
 188     adns__warn(ads,-1,0,"gettimeofday failed - will sleep for a bit: %s",
 189                strerror(errno));
 190     timerclear(&tvto_lr); timevaladd(&tvto_lr,LOCALRESOURCEMS);
 191     inter_maxto(tv_io, tvbuf, tvto_lr);
 192   } else {
 193     checktimeouts(ads,now,tv_io,tvbuf);
 194   }
 195
 196   inter_addfd(maxfd,readfds,ads->udpsocket);
 197
 198   switch (ads->tcpstate) {
 199   case server_disconnected:
 200     break;
 201   case server_connecting:
 202     inter_addfd(maxfd,writefds,ads->tcpsocket);
 203     break;
 204   case server_ok:
 205     inter_addfd(maxfd,readfds,ads->tcpsocket);
 206     inter_addfd(maxfd,exceptfds,ads->tcpsocket);
 207     if (ads->tcpsend.used) inter_addfd(maxfd,writefds,ads->tcpsocket);
 208     break;
 209   default:
 210     abort();
 211   }
 212 }
 213
 214 /* Callback procedures - these do the real work of reception and timeout, etc. */
 215
 216 static int callb_checkfd(int maxfd, const fd_set *fds, int fd) {
 217   return maxfd<0 || !fds ? 1 :
 218          fd<maxfd && FD_ISSET(fd,fds);
 219 }
 220
 221 static int internal_callback(adns_state ads, int maxfd,
 222                              const fd_set *readfds, const fd_set *writefds,
 223                              const fd_set *exceptfds,
 224                              struct timeval now) {
 225   int skip, want, dgramlen, count, udpaddrlen, r, serv;
 226   byte udpbuf[DNS_MAXUDP];
 227   struct sockaddr_in udpaddr;
 228
 229   count= 0;
 230
 231   switch (ads->tcpstate) {
 232   case server_disconnected:
 233     break;
 234   case server_connecting:
 235     if (callb_checkfd(maxfd,writefds,ads->tcpsocket)) {
 236       count++;
 237       assert(ads->tcprecv.used==0);
 238       if (!adns__vbuf_ensure(&ads->tcprecv,1)) return -1;
 239       if (ads->tcprecv.buf) {
 240         r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 241         if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 242           tcp_connected(ads,now);
 243         } else if (r>0) {
 244           adns__tcp_broken(ads,"connect/read","sent data before first request");
 245         } else if (errno!=EINTR) {
 246           adns__tcp_broken(ads,"connect/read",strerror(errno));
 247         }
 248       }
 249     }
 250     break;
 251   case server_ok:
 252     count+= callb_checkfd(maxfd,readfds,ads->tcpsocket) +
 253             callb_checkfd(maxfd,exceptfds,ads->tcpsocket) +
 254       (ads->tcpsend.used && callb_checkfd(maxfd,writefds,ads->tcpsocket));
 255     if (callb_checkfd(maxfd,readfds,ads->tcpsocket)) {
 256       skip= 0;
 257       for (;;) {
 258         if (ads->tcprecv.used<skip+2) {
 259           want= 2;
 260         } else {
 261           dgramlen= (ads->tcprecv.buf[skip]<<8) | ads->tcprecv.buf[skip+1];
 262           if (ads->tcprecv.used<skip+2+dgramlen) {
 263             want= 2+dgramlen;
 264           } else {
 265             adns__procdgram(ads,ads->tcprecv.buf+skip+2,dgramlen,ads->tcpserver,now);
 266             skip+= 2+dgramlen; continue;
 267           }
 268         }
 269         ads->tcprecv.used -= skip;
 270         memmove(ads->tcprecv.buf,ads->tcprecv.buf+skip,ads->tcprecv.used);
 271         skip= 0;
 272         if (!adns__vbuf_ensure(&ads->tcprecv,want)) return -1;
 273         assert(ads->tcprecv.used <= ads->tcprecv.avail);
 274         if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 275         r= read(ads->tcpsocket,
 276                 ads->tcprecv.buf+ads->tcprecv.used,
 277                 ads->tcprecv.avail-ads->tcprecv.used);
 278         if (r>0) {
 279           ads->tcprecv.used+= r;
 280         } else {
 281           if (r<0) {
 282             if (errno==EAGAIN || errno==EWOULDBLOCK || errno==ENOMEM) break;
 283             if (errno==EINTR) continue;
 284           }
 285           adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 286           break;
 287         }
 288       }
 289     } else if (callb_checkfd(maxfd,exceptfds,ads->tcpsocket)) {
 290       adns__tcp_broken(ads,"select","exceptional condition detected");
 291     } else if (ads->tcpsend.used && callb_checkfd(maxfd,writefds,ads->tcpsocket)) {
 292       adns__sigpipe_protect(ads);
 293       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 294       adns__sigpipe_unprotect(ads);
 295       if (r<0) {
 296         if (errno!=EAGAIN && errno!=EWOULDBLOCK && errno!=ENOMEM && errno!=EINTR) {
 297           adns__tcp_broken(ads,"write",strerror(errno));
 298         }
 299       } else if (r>0) {
 300         ads->tcpsend.used -= r;
 301         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 302       }
 303     }
 304     break;
 305   default:
 306     abort();
 307   }
 308
 309   if (callb_checkfd(maxfd,readfds,ads->udpsocket)) {
 310     count++;
 311     for (;;) {
 312       udpaddrlen= sizeof(udpaddr);
 313       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 314                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 315       if (r<0) {
 316         if (!(errno == EAGAIN || errno == EWOULDBLOCK ||
 317               errno == EINTR || errno == ENOMEM || errno == ENOBUFS))
 318           adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 319         break;
 320       }
 321       if (udpaddrlen != sizeof(udpaddr)) {
 322         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 323                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 324         continue;
 325       }
 326       if (udpaddr.sin_family != AF_INET) {
 327         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 328                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 329         continue;
 330       }
 331       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 332         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 333                    ntohs(udpaddr.sin_port),DNS_PORT);
 334         continue;
 335       }
 336       for (serv= 0;
 337            serv < ads->nservers &&
 338              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 339            serv++);
 340       if (serv >= ads->nservers) {
 341         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 342                    inet_ntoa(udpaddr.sin_addr));
 343         continue;
 344       }
 345       adns__procdgram(ads,udpbuf,r,serv,now);
 346     }
 347   }
 348   return count;
 349 }
 350
 351 int adns_callback(adns_state ads, int maxfd,
 352                   const fd_set *readfds, const fd_set *writefds,
 353                   const fd_set *exceptfds) {
 354   struct timeval now;
 355   int r;
 356
 357   r= gettimeofday(&now,0); if (r) return -1;
 358   checktimeouts(ads,now,0,0);
 359   return internal_callback(ads,maxfd,readfds,writefds,exceptfds,now);
 360 }
 361
 362 /* User-visible functions and their implementation. */
 363
 364 void adns__autosys(adns_state ads, struct timeval now) {
 365   if (ads->iflags & adns_if_noautosys) return;
 366   adns_callback(ads,-1,0,0,0);
 367 }
 368
 369 static int internal_check(adns_state ads,
 370                           adns_query *query_io,
 371                           adns_answer **answer,
 372                           void **context_r) {
 373   adns_query qu;
 374
 375   qu= *query_io;
 376   if (!qu) {
 377     if (!ads->output.head) return EWOULDBLOCK;
 378     qu= ads->output.head;
 379   } else {
 380     if (qu->id>=0) return EWOULDBLOCK;
 381   }
 382   LIST_UNLINK(ads->output,qu);
 383   *answer= qu->answer;
 384   if (context_r) *context_r= qu->ctx.ext;
 385   free(qu);
 386   return 0;
 387 }
 388
 389 int adns_wait(adns_state ads,
 390               adns_query *query_io,
 391               adns_answer **answer_r,
 392               void **context_r) {
 393   int r, maxfd, rsel, rcb;
 394   fd_set readfds, writefds, exceptfds;
 395   struct timeval tvbuf, *tvp;
 396
 397   for (;;) {
 398     r= internal_check(ads,query_io,answer_r,context_r);
 399     if (r != EWOULDBLOCK) return r;
 400     maxfd= 0; tvp= 0;
 401     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 402     adns_interest(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf);
 403     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 404     if (rsel==-1) {
 405       if (errno == EINTR && !(ads->iflags & adns_if_eintr)) continue;
 406       return errno;
 407     }
 408     rcb= adns_callback(ads,maxfd,&readfds,&writefds,&exceptfds);
 409     assert(rcb==rsel);
 410   }
 411 }
 412
 413 int adns_check(adns_state ads,
 414                adns_query *query_io,
 415                adns_answer **answer_r,
 416                void **context_r) {
 417   struct timeval now;
 418   int r;
 419
 420   r= gettimeofday(&now,0); if (r) return errno;
 421   adns__autosys(ads,now);
 422   return internal_check(ads,query_io,answer_r,context_r);
 423 }