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
  29 #include <netdb.h>
  30 #include <sys/socket.h>
  31 #include <netinet/in.h>
  32 #include <arpa/inet.h>
  33
  34 #include "internal.h"
  35
  36 /* TCP connection management */
  37
  38 void adns__tcp_broken(adns_state ads, const char *what, const char *why) {
  39   int serv;
  40   adns_query qu, nqu;
  41
  42   assert(ads->tcpstate == server_connecting || ads->tcpstate == server_ok);
  43   serv= ads->tcpserver;
  44   adns__warn(ads,serv,0,"TCP connection lost: %s: %s",what,why);
  45   close(ads->tcpsocket);
  46   ads->tcpstate= server_disconnected;
  47
  48   for (qu= ads->timew.head; qu; qu= nqu) {
  49     nqu= qu->next;
  50     if (qu->state == query_udp) continue;
  51     assert(qu->state == query_tcpwait || qu->state == query_tcpsent);
  52     qu->state= query_tcpwait;
  53     qu->tcpfailed |= (1<<serv);
  54     if (qu->tcpfailed == (1<<ads->nservers)-1) {
  55       LIST_UNLINK(ads->timew,qu);
  56       adns__query_fail(qu,adns_s_allservfail);
  57     }
  58   }
  59
  60   ads->tcprecv.used= ads->tcpsend.used= 0;
  61   ads->tcpserver= (serv+1)%ads->nservers;
  62 }
  63
  64 static void tcp_connected(adns_state ads, struct timeval now) {
  65   adns_query qu, nqu;
  66
  67   adns__debug(ads,ads->tcpserver,0,"TCP connected");
  68   ads->tcpstate= server_ok;
  69   for (qu= ads->timew.head; qu; qu= nqu) {
  70     nqu= qu->next;
  71     if (qu->state == query_udp) continue;
  72     assert (qu->state == query_tcpwait);
  73     adns__query_tcp(qu,now);
  74   }
  75 }
  76
  77 void adns__tcp_tryconnect(adns_state ads, struct timeval now) {
  78   int r, fd, tries;
  79   struct sockaddr_in addr;
  80   struct protoent *proto;
  81
  82   for (tries=0; tries<ads->nservers; tries++) {
  83     if (ads->tcpstate == server_connecting || ads->tcpstate == server_ok) return;
  84     assert(ads->tcpstate == server_disconnected);
  85     assert(!ads->tcpsend.used);
  86     assert(!ads->tcprecv.used);
  87
  88     proto= getprotobyname("tcp");
  89     if (!proto) { adns__diag(ads,-1,0,"unable to find protocol no. for TCP !"); return; }
  90     fd= socket(AF_INET,SOCK_STREAM,proto->p_proto);
  91     if (fd<0) {
  92       adns__diag(ads,-1,0,"cannot create TCP socket: %s",strerror(errno));
  93       return;
  94     }
  95     r= adns__setnonblock(ads,fd);
  96     if (r) {
  97       adns__diag(ads,-1,0,"cannot make TCP socket nonblocking: %s",strerror(r));
  98       close(fd);
  99       return;
 100     }
 101     memset(&addr,0,sizeof(addr));
 102     addr.sin_family= AF_INET;
 103     addr.sin_port= htons(DNS_PORT);
 104     addr.sin_addr= ads->servers[ads->tcpserver].addr;
 105     r= connect(fd,(const struct sockaddr*)&addr,sizeof(addr));
 106     ads->tcpsocket= fd;
 107     ads->tcpstate= server_connecting;
 108     if (r==0) { tcp_connected(ads,now); continue; }
 109     if (errno == EWOULDBLOCK || errno == EINPROGRESS) return;
 110     adns__tcp_broken(ads,"connect",strerror(errno));
 111   }
 112 }
 113
 114 /* `Interest' functions - find out which fd's we might be interested in,
 115  * and when we want to be called back for a timeout.
 116  */
 117
 118 static void inter_maxto(struct timeval **tv_io, struct timeval *tvbuf,
 119                         struct timeval maxto) {
 120   struct timeval *rbuf;
 121
 122   if (!tv_io) return;
 123   rbuf= *tv_io;
 124   if (!rbuf) {
 125     *tvbuf= maxto; *tv_io= tvbuf;
 126   } else {
 127     if (timercmp(rbuf,&maxto,>)) *rbuf= maxto;
 128   }
 129 /*fprintf(stderr,"inter_maxto maxto=%ld.%06ld result=%ld.%06ld\n",
 130         maxto.tv_sec,maxto.tv_usec,(**tv_io).tv_sec,(**tv_io).tv_usec);*/
 131 }
 132
 133 static void inter_maxtoabs(struct timeval **tv_io, struct timeval *tvbuf,
 134                            struct timeval now, struct timeval maxtime) {
 135   ldiv_t dr;
 136
 137 /*fprintf(stderr,"inter_maxtoabs now=%ld.%06ld maxtime=%ld.%06ld\n",
 138         now.tv_sec,now.tv_usec,maxtime.tv_sec,maxtime.tv_usec);*/
 139   if (!tv_io) return;
 140   maxtime.tv_sec -= (now.tv_sec+2);
 141   maxtime.tv_usec -= (now.tv_usec-2000000);
 142   dr= ldiv(maxtime.tv_usec,1000000);
 143   maxtime.tv_sec += dr.quot;
 144   maxtime.tv_usec -= dr.quot*1000000;
 145   if (maxtime.tv_sec<0) timerclear(&maxtime);
 146   inter_maxto(tv_io,tvbuf,maxtime);
 147 }
 148
 149 static void inter_addfd(int *maxfd, fd_set *fds, int fd) {
 150   if (!maxfd || !fds) return;
 151   if (fd>=*maxfd) *maxfd= fd+1;
 152   FD_SET(fd,fds);
 153 }
 154
 155 static void checktimeouts(adns_state ads, struct timeval now,
 156                           struct timeval **tv_io, struct timeval *tvbuf) {
 157   adns_query qu, nqu;
 158
 159   for (qu= ads->timew.head; qu; qu= nqu) {
 160     nqu= qu->next;
 161     if (timercmp(&now,&qu->timeout,>)) {
 162       LIST_UNLINK(ads->timew,qu);
 163       if (qu->state != query_udp) {
 164         adns__query_fail(qu,adns_s_timeout);
 165       } else {
 166         adns__query_udp(qu,now);
 167       }
 168     } else {
 169       inter_maxtoabs(tv_io,tvbuf,now,qu->timeout);
 170     }
 171   }
 172 }
 173
 174 void adns_interest(adns_state ads, int *maxfd,
 175                    fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
 176                    struct timeval **tv_io, struct timeval *tvbuf) {
 177   struct timeval now;
 178   struct timeval tvto_lr;
 179   int r;
 180
 181 /*fprintf(stderr,"adns_interest\n");*/
 182
 183   r= gettimeofday(&now,0);
 184   if (r) {
 185     adns__warn(ads,-1,0,"gettimeofday failed - will sleep for a bit: %s",
 186                strerror(errno));
 187     timerclear(&tvto_lr); timevaladd(&tvto_lr,LOCALRESOURCEMS);
 188     inter_maxto(tv_io, tvbuf, tvto_lr);
 189   } else {
 190     checktimeouts(ads,now,tv_io,tvbuf);
 191   }
 192
 193   inter_addfd(maxfd,readfds,ads->udpsocket);
 194
 195   switch (ads->tcpstate) {
 196   case server_disconnected:
 197     break;
 198   case server_connecting:
 199     inter_addfd(maxfd,writefds,ads->tcpsocket);
 200     break;
 201   case server_ok:
 202     inter_addfd(maxfd,readfds,ads->tcpsocket);
 203     inter_addfd(maxfd,exceptfds,ads->tcpsocket);
 204     if (ads->tcpsend.used) inter_addfd(maxfd,writefds,ads->tcpsocket);
 205     break;
 206   default:
 207     abort();
 208   }
 209 }
 210
 211 /* Callback procedures - these do the real work of reception and timeout, etc. */
 212
 213 static int callb_checkfd(int maxfd, const fd_set *fds, int fd) {
 214   return maxfd<0 || !fds ? 1 :
 215          fd<maxfd && FD_ISSET(fd,fds);
 216 }
 217
 218 static int internal_callback(adns_state ads, int maxfd,
 219                              const fd_set *readfds, const fd_set *writefds,
 220                              const fd_set *exceptfds,
 221                              struct timeval now) {
 222   int skip, want, dgramlen, count, udpaddrlen, r, serv;
 223   byte udpbuf[DNS_MAXUDP];
 224   struct sockaddr_in udpaddr;
 225
 226   count= 0;
 227
 228   switch (ads->tcpstate) {
 229   case server_disconnected:
 230     break;
 231   case server_connecting:
 232     if (callb_checkfd(maxfd,writefds,ads->tcpsocket)) {
 233       count++;
 234       assert(ads->tcprecv.used==0);
 235       if (!adns__vbuf_ensure(&ads->tcprecv,1)) return -1;
 236       if (ads->tcprecv.buf) {
 237         r= read(ads->tcpsocket,&ads->tcprecv.buf,1);
 238         if (r==0 || (r<0 && (errno==EAGAIN || errno==EWOULDBLOCK))) {
 239           tcp_connected(ads,now);
 240         } else if (r>0) {
 241           adns__tcp_broken(ads,"connect/read","sent data before first request");
 242         } else if (errno!=EINTR) {
 243           adns__tcp_broken(ads,"connect/read",strerror(errno));
 244         }
 245       }
 246     }
 247     break;
 248   case server_ok:
 249     count+= callb_checkfd(maxfd,readfds,ads->tcpsocket) +
 250             callb_checkfd(maxfd,exceptfds,ads->tcpsocket) +
 251       (ads->tcpsend.used && callb_checkfd(maxfd,writefds,ads->tcpsocket));
 252     if (callb_checkfd(maxfd,readfds,ads->tcpsocket)) {
 253       skip= 0;
 254       for (;;) {
 255         if (ads->tcprecv.used<skip+2) {
 256           want= 2;
 257         } else {
 258           dgramlen= (ads->tcprecv.buf[skip]<<8) | ads->tcprecv.buf[skip+1];
 259           if (ads->tcprecv.used<skip+2+dgramlen) {
 260             want= 2+dgramlen;
 261           } else {
 262             adns__procdgram(ads,ads->tcprecv.buf+skip+2,dgramlen,ads->tcpserver,now);
 263             skip+= 2+dgramlen; continue;
 264           }
 265         }
 266         ads->tcprecv.used -= skip;
 267         memmove(ads->tcprecv.buf,ads->tcprecv.buf+skip,ads->tcprecv.used);
 268         skip= 0;
 269         if (!adns__vbuf_ensure(&ads->tcprecv,want)) return -1;
 270         assert(ads->tcprecv.used <= ads->tcprecv.avail);
 271         if (ads->tcprecv.used == ads->tcprecv.avail) continue;
 272         r= read(ads->tcpsocket,
 273                 ads->tcprecv.buf+ads->tcprecv.used,
 274                 ads->tcprecv.avail-ads->tcprecv.used);
 275         if (r>0) {
 276           ads->tcprecv.used+= r;
 277         } else {
 278           if (r<0) {
 279             if (errno==EAGAIN || errno==EWOULDBLOCK || errno==ENOMEM) break;
 280             if (errno==EINTR) continue;
 281           }
 282           adns__tcp_broken(ads,"read",r?strerror(errno):"closed");
 283           break;
 284         }
 285       }
 286     } else if (callb_checkfd(maxfd,exceptfds,ads->tcpsocket)) {
 287       adns__tcp_broken(ads,"select","exceptional condition detected");
 288     } else if (ads->tcpsend.used && callb_checkfd(maxfd,writefds,ads->tcpsocket)) {
 289       adns__sigpipe_protect(ads);
 290       r= write(ads->tcpsocket,ads->tcpsend.buf,ads->tcpsend.used);
 291       adns__sigpipe_unprotect(ads);
 292       if (r<0) {
 293         if (errno!=EAGAIN && errno!=EWOULDBLOCK && errno!=ENOMEM && errno!=EINTR) {
 294           adns__tcp_broken(ads,"write",strerror(errno));
 295         }
 296       } else if (r>0) {
 297         ads->tcpsend.used -= r;
 298         memmove(ads->tcpsend.buf,ads->tcpsend.buf+r,ads->tcpsend.used);
 299       }
 300     }
 301     break;
 302   default:
 303     abort();
 304   }
 305
 306   if (callb_checkfd(maxfd,readfds,ads->udpsocket)) {
 307     count++;
 308     for (;;) {
 309       udpaddrlen= sizeof(udpaddr);
 310       r= recvfrom(ads->udpsocket,udpbuf,sizeof(udpbuf),0,
 311                   (struct sockaddr*)&udpaddr,&udpaddrlen);
 312       if (r<0) {
 313         if (!(errno == EAGAIN || errno == EWOULDBLOCK ||
 314               errno == EINTR || errno == ENOMEM || errno == ENOBUFS))
 315           adns__warn(ads,-1,0,"datagram receive error: %s",strerror(errno));
 316         break;
 317       }
 318       if (udpaddrlen != sizeof(udpaddr)) {
 319         adns__diag(ads,-1,0,"datagram received with wrong address length %d"
 320                    " (expected %d)", udpaddrlen,sizeof(udpaddr));
 321         continue;
 322       }
 323       if (udpaddr.sin_family != AF_INET) {
 324         adns__diag(ads,-1,0,"datagram received with wrong protocol family"
 325                    " %u (expected %u)",udpaddr.sin_family,AF_INET);
 326         continue;
 327       }
 328       if (ntohs(udpaddr.sin_port) != DNS_PORT) {
 329         adns__diag(ads,-1,0,"datagram received from wrong port %u (expected %u)",
 330                    ntohs(udpaddr.sin_port),DNS_PORT);
 331         continue;
 332       }
 333       for (serv= 0;
 334            serv < ads->nservers &&
 335              ads->servers[serv].addr.s_addr != udpaddr.sin_addr.s_addr;
 336            serv++);
 337       if (serv >= ads->nservers) {
 338         adns__warn(ads,-1,0,"datagram received from unknown nameserver %s",
 339                    inet_ntoa(udpaddr.sin_addr));
 340         continue;
 341       }
 342       adns__procdgram(ads,udpbuf,r,serv,now);
 343     }
 344   }
 345   return count;
 346 }
 347
 348 int adns_callback(adns_state ads, int maxfd,
 349                   const fd_set *readfds, const fd_set *writefds,
 350                   const fd_set *exceptfds) {
 351   struct timeval now;
 352   int r;
 353
 354   r= gettimeofday(&now,0); if (r) return -1;
 355   checktimeouts(ads,now,0,0);
 356   return internal_callback(ads,maxfd,readfds,writefds,exceptfds,now);
 357 }
 358
 359 /* User-visible functions and their implementation. */
 360
 361 void adns__autosys(adns_state ads, struct timeval now) {
 362   if (ads->iflags & adns_if_noautosys) return;
 363   adns_callback(ads,-1,0,0,0);
 364 }
 365
 366 static int internal_check(adns_state ads,
 367                           adns_query *query_io,
 368                           adns_answer **answer,
 369                           void **context_r) {
 370   adns_query qu;
 371
 372   qu= *query_io;
 373   if (!qu) {
 374     if (!ads->output.head) return EWOULDBLOCK;
 375     qu= ads->output.head;
 376   } else {
 377     if (qu->id>=0) return EWOULDBLOCK;
 378   }
 379   LIST_UNLINK(ads->output,qu);
 380   *answer= qu->answer;
 381   if (context_r) *context_r= qu->ctx.ext;
 382   free(qu);
 383   return 0;
 384 }
 385
 386 int adns_wait(adns_state ads,
 387               adns_query *query_io,
 388               adns_answer **answer_r,
 389               void **context_r) {
 390   int r, maxfd, rsel, rcb;
 391   fd_set readfds, writefds, exceptfds;
 392   struct timeval tvbuf, *tvp;
 393
 394   for (;;) {
 395     r= internal_check(ads,query_io,answer_r,context_r);
 396     if (r != EWOULDBLOCK) return r;
 397     maxfd= 0; tvp= 0;
 398     FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&exceptfds);
 399     adns_interest(ads,&maxfd,&readfds,&writefds,&exceptfds,&tvp,&tvbuf);
 400     rsel= select(maxfd,&readfds,&writefds,&exceptfds,tvp);
 401     if (rsel==-1) {
 402       if (errno == EINTR && !(ads->iflags & adns_if_eintr)) continue;
 403       return errno;
 404     }
 405     rcb= adns_callback(ads,maxfd,&readfds,&writefds,&exceptfds);
 406     assert(rcb==rsel);
 407   }
 408 }
 409
 410 int adns_check(adns_state ads,
 411                adns_query *query_io,
 412                adns_answer **answer_r,
 413                void **context_r) {
 414   struct timeval now;
 415   int r;
 416
 417   r= gettimeofday(&now,0); if (r) return errno;
 418   adns__autosys(ads,now);
 419   return internal_check(ads,query_io,answer_r,context_r);
 420 }