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, 1998 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
  29 #include <netdb.h>
  30 #include <arpa/inet.h>
  31
  32 #include "internal.h"
  33
  34 /* TCP connection management */
  35
  36 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  37   int serv;
  38   adns_query qu, nqu;
  39
  40   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  41   serv= ads->tcpserver;
  42   adns__warn(ads,serv,0,"TCP connection lost: %s: %s",what,why);
  43   close(ads->tcpsocket);
  44   ads->tcpstate= server_disconnected;
  45
  46   for (qu= ads->timew.head; qu; qu= nqu) {
  47     nqu= qu->next;
  48     if (qu->state == query_udp) continue;
  49     assert(qu->state == query_tcpwait || qu->state == query_tcpsent);
  50     qu->state= query_tcpwait;
  51     qu->tcpfailed |= (1<<serv);
  52     if (qu->tcpfailed == (1<<ads->nservers)-1) {
  53       LIST_UNLINK(ads->timew,qu);
  54       adns__query_fail(qu,adns_s_allservfail);
  55     }
  56   }
  57
  58   ads->tcprecv.used= ads->tcpsend.used= 0;
  59   ads->tcpserver= (serv+1)%ads->nservers;
  60 }
  61
  62 static void tcp_connected(adns_state ads, struct timeval now) {
  63   adns_query qu, nqu;
  64
  65   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  66   ads->tcpstate= server_ok;
  67   for (qu= ads->timew.head; qu; qu= nqu) {
  68     nqu= qu->next;
  69     if (qu->state == query_udp) continue;
  70     assert (qu->state == query_tcpwait);
  71     adns__query_tcp(qu,now);
  72   }
  73 }
  74
  75 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  76   int r, fd, tries;
  77   struct sockaddr_in addr;
  78   struct protoent *proto;
  79   /* fixme: single TCP timeout, not once per server */
  80
  81   for (tries=0; tries<ads->nservers; tries++) {
  82     if (ads->tcpstate == server_connecting || ads->tcpstate == server_ok) return;
  83     assert(ads->tcpstate == server_disconnected);
  84     assert(!ads->tcpsend.used);
  85     assert(!ads->tcprecv.used);
  86
  87     proto= getprotobyname("tcp");
  88     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
  89     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
  90     if (fd<0) {
  91       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
  92       return;
  93     }
  94     r= adns__setnonblock(ads,fd);
  95     if (r) {
  96       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
  97       close(fd);
  98       return;
  99     }
 100     memset(&addr,0,sizeof(addr));
 101     addr.sin_family= AF_INET;
 102     addr.sin_port= htons(DNS_PORT);
 103     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 104     r= connect(fd,&addr,sizeof(addr));
 105     ads->tcpsocket= fd;
 106     ads->tcpstate= server_connecting;
 107     if (r==0) { tcp_connected(ads,now); continue; }
 108     if (errno == EWOULDBLOCK || errno == EINPROGRESS) return;
 109     adns__tcp_broken(ads,"connect",strerror(errno));
 110   }
 111 }
 112
 113 /* `Interest' functions - find out which fd's we might be interested in,
 114  * and when we want to be called back for a timeout.
 115  */
 116
 117 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 118                         struct timeval maxto) {
 119   struct timeval *rbuf;
 120
 121   if (!tv_io) return;
 122   rbuf= *tv_io;
 123   if (!rbuf) {
 124     *tvbuf= maxto; *tv_io= tvbuf;
 125   } else {
 126     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 127   }
 128 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 129         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 130 }
 131
 132 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 133                            struct timeval now, struct timeval maxtime) {
 134   ldiv_t dr;
 135
 136 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 137         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 138   if (!tv_io) return;
 139   maxtime.tv_sec -= (now.tv_sec+2);
 140   maxtime.tv_usec -= (now.tv_usec-2000000);
 141   dr= ldiv(maxtime.tv_usec,1000000);
 142   maxtime.tv_sec += dr.quot;
 143   maxtime.tv_usec -= dr.quot*1000000;
 144   if (maxtime.tv_sec<0) timerclear(&maxtime);
 145   inter_maxto(tv_io,tvbuf,maxtime);
 146 }
 147
 148 static void inter_addfd(int *maxfd, fd_set *fds, int fd) {
 149   if (!maxfd || !fds) return;
 150   if (fd>=*maxfd) *maxfd= fd+1;
 151   FD_SET(fd,fds);
 152 }
 153
 154 static void checktimeouts(adns_state ads, struct timeval now,
 155                           struct timeval **tv_io, struct timeval *tvbuf) {
 156   adns_query qu, nqu;
 157
 158   for (qu= ads->timew.head; qu; qu= nqu) {
 159     nqu= qu->next;
 160     if (timercmp(&now,&qu->timeout,>)) {
 161       LIST_UNLINK(ads->timew,qu);
 162       if (qu->state != query_udp) {
 163         adns__query_fail(qu,adns_s_timeout);
 164       } else {
 165         adns__query_udp(qu,now);
 166       }
 167     } else {
 168       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 169     }
 170   }
 171 }
 172
 173 void adns_interest(adns_state ads, int *maxfd,
 174                    fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
 175                    struct timeval **tv_io, struct timeval *tvbuf) {
 176   struct timeval now;
 177   struct timeval tvto_lr;
 178   int r;
 179
 180 /*fprintf(stderr,"adns_interest\n");*/
 181
 182   r= gettimeofday(&now,0);
 183   if (r) {
 184     adns__warn(ads,-1,0,"gettimeofday failed - will sleep for a bit: %s",
 185                strerror(errno));
 186     timerclear(&tvto_lr); timevaladd(&tvto_lr,LOCALRESOURCEMS);
 187     inter_maxto(tv_io, tvbuf, tvto_lr);
 188   } else {
 189     checktimeouts(ads,now,tv_io,tvbuf);
 190   }
 191
 192   inter_addfd(maxfd,readfds,ads->udpsocket);
 193
 194   switch (ads->tcpstate) {
 195   case server_disconnected:
 196     break;
 197   case server_connecting:
 198     inter_addfd(maxfd,writefds,ads->tcpsocket);
 199     break;
 200   case server_ok:
 201     inter_addfd(maxfd,readfds,ads->tcpsocket);
 202     inter_addfd(maxfd,exceptfds,ads->tcpsocket);
 203     if (ads->tcpsend.used) inter_addfd(maxfd,writefds,ads->tcpsocket);
 204     break;
 205   default:
 206     abort();
 207   }
 208 }
 209
 210 /* Callback procedures - these do the real work of reception and timeout, etc. */
 211
 212 static int callb_checkfd(int maxfd, const fd_set *fds, int fd) {
 213   return maxfd<0 || !fds ? 1 :
 214          fd<maxfd && FD_ISSET(fd,fds);
 215 }
 216
 217 static int internal_callback(adns_state ads, int maxfd,
 218                              const fd_set *readfds, const fd_set *writefds,
 219                              const fd_set *exceptfds,
 220                              struct timeval now) {
 221   int skip, want, dgramlen, count, udpaddrlen, r, serv;
 222   byte udpbuf[DNS_MAXUDP];
 223   struct sockaddr_in udpaddr;
 224
 225   count= 0;
 226
 227   switch (ads->tcpstate) {
 228   case server_disconnected:
 229     break;
 230   case server_connecting:
 231     if (callb_checkfd(maxfd,writefds,ads->tcpsocket)) {
 232       count++;
 233       assert(ads->tcprecv.used==0);
 234       if (!adns__vbuf_ensure(&ads->tcprecv,1)) return -1;
 235       if (ads->tcprecv.buf) {
 236         r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 237         if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 238           tcp_connected(ads,now);
 239         } else if (r>0) {
 240           adns__tcp_broken(ads,"connect/read","sent data before first request");
 241         } else if (errno!=EINTR) {
 242           adns__tcp_broken(ads,"connect/read",strerror(errno));
 243         }
 244       }
 245     }
 246     break;
 247   case server_ok:
 248     count+= callb_checkfd(maxfd,readfds,ads->tcpsocket) +
 249             callb_checkfd(maxfd,exceptfds,ads->tcpsocket) +
 250       (ads->tcpsend.used && callb_checkfd(maxfd,writefds,ads->tcpsocket));
 251     if (callb_checkfd(maxfd,readfds,ads->tcpsocket)) {
 252       skip= 0;
 253       for (;;) {
 254         if (ads->tcprecv.used<skip+2) {
 255           want= 2;
 256         } else {
 257           dgramlen= (ads->tcprecv.buf[skip]<<8) | ads->tcprecv.buf[skip+1];
 258           if (ads->tcprecv.used<skip+2+dgramlen) {
 259             want= 2+dgramlen;
 260           } else {
 261             adns__procdgram(ads,ads->tcprecv.buf+skip+2,dgramlen,ads->tcpserver,now);
 262             skip+= 2+dgramlen; continue;
 263           }
 264         }
 265         ads->tcprecv.used -= skip;
 266         memmove(ads->tcprecv.buf,ads->tcprecv.buf+skip,ads->tcprecv.used);
 267         skip= 0;
 268         if (!adns__vbuf_ensure(&ads->tcprecv,want)) return -1;
 269         assert(ads->tcprecv.used <= ads->tcprecv.avail);
 270         if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 271         r= read(ads->tcpsocket,
 272                 ads->tcprecv.buf+ads->tcprecv.used,
 273                 ads->tcprecv.avail-ads->tcprecv.used);
 274         if (r>0) {
 275           ads->tcprecv.used+= r;
 276         } else {
 277           if (r<0) {
 278             if (errno==EAGAIN || errno==EWOULDBLOCK || errno==ENOMEM) break;
 279             if (errno==EINTR) continue;
 280           }
 281           adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 282           break;
 283         }
 284       }
 285     } else if (callb_checkfd(maxfd,exceptfds,ads->tcpsocket)) {
 286       adns__tcp_broken(ads,"select","exceptional condition detected");
 287     } else if (ads->tcpsend.used && callb_checkfd(maxfd,writefds,ads->tcpsocket)) {
 288       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 289       if (r<0) {
 290         if (errno!=EAGAIN && errno!=EWOULDBLOCK && errno!=ENOMEM && errno!=EINTR) {
 291           adns__tcp_broken(ads,"write",strerror(errno));
 292         }
 293       } else if (r>0) {
 294         ads->tcpsend.used -= r;
 295         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 296       }
 297     }
 298     break;
 299   default:
 300     abort();
 301   }
 302
 303   if (callb_checkfd(maxfd,readfds,ads->udpsocket)) {
 304     count++;
 305     for (;;) {
 306       udpaddrlen= sizeof(udpaddr);
 307       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,&udpaddr,&udpaddrlen);
 308       if (r<0) {
 309         if (!(errno == EAGAIN || errno == EWOULDBLOCK ||
 310               errno == EINTR || errno == ENOMEM || errno == ENOBUFS))
 311           adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 312         break;
 313       }
 314       if (udpaddrlen != sizeof(udpaddr)) {
 315         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 316                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 317         continue;
 318       }
 319       if (udpaddr.sin_family != AF_INET) {
 320         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 321                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 322         continue;
 323       }
 324       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 325         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 326                    ntohs(udpaddr.sin_port),DNS_PORT);
 327         continue;
 328       }
 329       for (serv= 0;
 330            serv < ads->nservers &&
 331              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 332            serv++);
 333       if (serv >= ads->nservers) {
 334         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 335                    inet_ntoa(udpaddr.sin_addr));
 336         continue;
 337       }
 338       adns__procdgram(ads,udpbuf,r,serv,now);
 339     }
 340   }
 341   return count;
 342 }
 343
 344 int adns_callback(adns_state ads, int maxfd,
 345                   const fd_set *readfds, const fd_set *writefds,
 346                   const fd_set *exceptfds) {
 347   struct timeval now;
 348   int r;
 349
 350   r= gettimeofday(&now,0); if (r) return -1;
 351   checktimeouts(ads,now,0,0);
 352   return internal_callback(ads,maxfd,readfds,writefds,exceptfds,now);
 353 }
 354
 355 /* User-visible functions and their implementation. */
 356
 357 void adns__autosys(adns_state ads, struct timeval now) {
 358   if (ads->iflags & adns_if_noautosys) return;
 359   adns_callback(ads,-1,0,0,0);
 360 }
 361
 362 static int internal_check(adns_state ads,
 363                           adns_query *query_io,
 364                           adns_answer **answer,
 365                           void **context_r) {
 366   adns_query qu;
 367
 368   qu= *query_io;
 369   if (!qu) {
 370     if (!ads->output.head) return EWOULDBLOCK;
 371     qu= ads->output.head;
 372   } else {
 373     if (qu->id>=0) return EWOULDBLOCK;
 374   }
 375   LIST_UNLINK(ads->output,qu);
 376   *answer= qu->answer;
 377   if (context_r) *context_r= qu->context.ext;
 378   free(qu);
 379   return 0;
 380 }
 381
 382 int adns_wait(adns_state ads,
 383               adns_query *query_io,
 384               adns_answer **answer_r,
 385               void **context_r) {
 386   int r, maxfd, rsel, rcb;
 387   fd_set readfds, writefds, exceptfds;
 388   struct timeval tvbuf, *tvp;
 389
 390   for (;;) {
 391     r= internal_check(ads,query_io,answer_r,context_r);
 392     if (r != EWOULDBLOCK) return r;
 393     maxfd= 0; tvp= 0;
 394     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 395     adns_interest(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf);
 396     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 397     if (rsel==-1) return r;
 398     rcb= adns_callback(ads,maxfd,&readfds,&writefds,&exceptfds);
 399     assert(rcb==rsel);
 400   }
 401 }
 402
 403 int adns_check(adns_state ads,
 404                adns_query *query_io,
 405                adns_answer **answer_r,
 406                void **context_r) {
 407   struct timeval now;
 408   int r;
 409
 410   r= gettimeofday(&now,0); if (r) return errno;
 411   adns__autosys(ads,now);
 412   return internal_check(ads,query_io,answer_r,context_r);
 413 }