| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: bres.c,v 1.7 2004/04/08 01:36:11 mdw Exp $ |
| 4 | * |
| 5 | * Background reverse name resolution |
| 6 | * |
| 7 | * (c) 1999 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of the mLib utilities library. |
| 13 | * |
| 14 | * mLib is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU Library General Public License as |
| 16 | * published by the Free Software Foundation; either version 2 of the |
| 17 | * License, or (at your option) any later version. |
| 18 | * |
| 19 | * mLib is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU Library General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU Library General Public |
| 25 | * License along with mLib; if not, write to the Free |
| 26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include "config.h" |
| 33 | |
| 34 | #include <errno.h> |
| 35 | #include <signal.h> |
| 36 | #include <stdio.h> |
| 37 | #include <stdlib.h> |
| 38 | #include <string.h> |
| 39 | |
| 40 | #include <sys/types.h> |
| 41 | #include <sys/time.h> |
| 42 | #include <unistd.h> |
| 43 | #include <sys/wait.h> |
| 44 | |
| 45 | #include <sys/socket.h> |
| 46 | #include <netinet/in.h> |
| 47 | #include <arpa/inet.h> |
| 48 | #include <netdb.h> |
| 49 | |
| 50 | #include "alloc.h" |
| 51 | #include "bres.h" |
| 52 | #include "report.h" |
| 53 | #include "sel.h" |
| 54 | |
| 55 | /*----- Magic numbers -----------------------------------------------------*/ |
| 56 | |
| 57 | #define BRES_MAX 15 /* Maximum number of resolvers */ |
| 58 | #define BRES_IDLE 60 /* Lifetime of an idle resolver */ |
| 59 | |
| 60 | /*----- Static variables --------------------------------------------------*/ |
| 61 | |
| 62 | #ifndef BRES_STANDALONE |
| 63 | |
| 64 | static bres_server servers[BRES_MAX]; /* Statically allocated servers */ |
| 65 | |
| 66 | #define FREE ((bres_server *)&freelist) |
| 67 | static struct { bres_server *next, *prev; } freelist = { FREE, FREE }; |
| 68 | |
| 69 | #define QUEUE ((bres_client *)&queue) |
| 70 | static struct { bres_client *next, *prev; } queue = { QUEUE, QUEUE }; |
| 71 | |
| 72 | static sel_state *sel; |
| 73 | |
| 74 | static const char *server = 0; |
| 75 | |
| 76 | #endif |
| 77 | |
| 78 | /*----- Background resolver protocol --------------------------------------*/ |
| 79 | |
| 80 | /* --- Requests and responses --- * |
| 81 | * |
| 82 | * There are two types of requests: name and addr, corresponding to the |
| 83 | * standard @gethostbyname@ and @gethostbyaddr@ calls. There are two types |
| 84 | * of responses too: a positive response consists of an encoded equivalent of |
| 85 | * a @struct hostent@ structure containing the requested information; a |
| 86 | * negative response consists of an @h_errno@ value explaining the problem. |
| 87 | */ |
| 88 | |
| 89 | #define BRES_BYNAME 0 /* Request: resolve given name */ |
| 90 | #define BRES_BYADDR 1 /* Request: resolve given address */ |
| 91 | |
| 92 | #define BRES_HOSTENT 0 /* Response: resolved ok */ |
| 93 | #define BRES_ERROR 1 /* Response: resolution failed */ |
| 94 | |
| 95 | /* --- Encodings --- * |
| 96 | * |
| 97 | * A string is encoded as a @size_t@ length followed by the actual data. The |
| 98 | * null terminator is not transmitted. |
| 99 | * |
| 100 | * Addresses for resolution are transmitted as raw @struct in_addr@ |
| 101 | * structures. |
| 102 | * |
| 103 | * A @hostent@ structure is transmitted as a header containing fixed-size |
| 104 | * information, followed by the official name, an array of aliases, and an |
| 105 | * array of addresses. The number of items in the arrays is specified in the |
| 106 | * header. |
| 107 | * |
| 108 | * The implementation assumes that a complete request or reply is always |
| 109 | * sent. Undesirable blocking will occur if this is not the case. Both ends |
| 110 | * are assumed to trust each other. A protocol failure results in the child |
| 111 | * in question being terminated. |
| 112 | */ |
| 113 | |
| 114 | typedef struct hostskel { |
| 115 | size_t nalias; |
| 116 | int addrtype; |
| 117 | size_t addrsz; |
| 118 | size_t naddr; |
| 119 | } hostskel; |
| 120 | |
| 121 | /* --- @doread@, @dowrite@ --- * |
| 122 | * |
| 123 | * Arguments: @int fd@ = file descriptor |
| 124 | * @void *buf@ = buffer for data |
| 125 | * @size_t sz@ = size of data |
| 126 | * |
| 127 | * Returns: Zero if successful, nonzero otherwise. |
| 128 | * |
| 129 | * Use: Reads or writes a chunk of data. @EINTR@ errors are retried; |
| 130 | * incomplete reads and writes are continued from where they |
| 131 | * left off. End-of-file is considered an I/O error. |
| 132 | */ |
| 133 | |
| 134 | static int doread(int fd, void *buf, size_t sz) |
| 135 | { |
| 136 | char *p = buf; |
| 137 | while (sz) { |
| 138 | int r = read(fd, p, sz); |
| 139 | if (r < 0) { |
| 140 | if (errno == EINTR) |
| 141 | continue; |
| 142 | return (-1); |
| 143 | } else if (r == 0) { |
| 144 | errno = EIO; |
| 145 | return (-1); |
| 146 | } |
| 147 | sz -= r; |
| 148 | p += r; |
| 149 | } |
| 150 | return (0); |
| 151 | } |
| 152 | |
| 153 | static int dowrite(int fd, const void *buf, size_t sz) |
| 154 | { |
| 155 | const char *p = buf; |
| 156 | while (sz) { |
| 157 | int r = write(fd, p, sz); |
| 158 | if (r < 0) { |
| 159 | if (errno == EINTR) |
| 160 | continue; |
| 161 | return (-1); |
| 162 | } else if (r == 0) { |
| 163 | errno = EIO; |
| 164 | return (-1); |
| 165 | } |
| 166 | sz -= r; |
| 167 | p += r; |
| 168 | } |
| 169 | return (0); |
| 170 | } |
| 171 | |
| 172 | /* --- @getstring@ --- * |
| 173 | * |
| 174 | * Arguments: @int fd@ = file descriptor to read |
| 175 | * |
| 176 | * Returns: String in heap-allocated block, or a null pointer. |
| 177 | * |
| 178 | * Use: Decodes a string. |
| 179 | */ |
| 180 | |
| 181 | static char *getstring(int fd) |
| 182 | { |
| 183 | size_t sz; |
| 184 | char *p; |
| 185 | |
| 186 | if (doread(fd, &sz, sizeof(sz)) || (p = malloc(sz + 1)) == 0) |
| 187 | return (0); |
| 188 | if (doread(fd, p, sz)) { |
| 189 | free(p); |
| 190 | return (0); |
| 191 | } |
| 192 | p[sz] = 0; |
| 193 | return (p); |
| 194 | } |
| 195 | |
| 196 | /* --- @putstring@ --- * |
| 197 | * |
| 198 | * Arguments: @int fd@ = file descriptor to write on |
| 199 | * @const char *p@ = pointer to string to write |
| 200 | * |
| 201 | * Returns: Zero if successful. |
| 202 | * |
| 203 | * Use: Encodes a string. |
| 204 | */ |
| 205 | |
| 206 | static int putstring(int fd, const char *p) |
| 207 | { |
| 208 | size_t sz = strlen(p); |
| 209 | if (dowrite(fd, &sz, sizeof(sz)) || dowrite(fd, p, sz)) |
| 210 | return (-1); |
| 211 | return (0); |
| 212 | } |
| 213 | |
| 214 | /* --- @gethost@ --- * |
| 215 | * |
| 216 | * Arguments: @int fd@ = file descriptor to read |
| 217 | * |
| 218 | * Returns: Pointer to heap-allocated @struct hostent@, or null. |
| 219 | * |
| 220 | * Use: Decodes a host structure. The resulting structure is all in |
| 221 | * one big heap block. |
| 222 | */ |
| 223 | |
| 224 | #ifndef BRES_STANDALONE |
| 225 | |
| 226 | static struct hostent *gethost(int fd) |
| 227 | { |
| 228 | hostskel hsk; |
| 229 | struct hostent *h; |
| 230 | char *name; |
| 231 | char **alias = 0; |
| 232 | |
| 233 | /* --- Read the skeleton structure --- */ |
| 234 | |
| 235 | if (doread(fd, &hsk, sizeof(hsk))) |
| 236 | goto tidy_0; |
| 237 | |
| 238 | /* --- Read the hostname and alias strings --- * |
| 239 | * |
| 240 | * Count the length of the strings as we go. |
| 241 | */ |
| 242 | |
| 243 | { |
| 244 | size_t sz = |
| 245 | sizeof(struct hostent) + |
| 246 | hsk.naddr * hsk.addrsz + |
| 247 | (hsk.naddr + hsk.nalias + 2) * sizeof(char *); |
| 248 | |
| 249 | /* --- Read the primary host name --- */ |
| 250 | |
| 251 | if ((name = getstring(fd)) == 0) |
| 252 | goto tidy_0; |
| 253 | sz += strlen(name) + 1; |
| 254 | |
| 255 | /* --- Read in the alias names --- */ |
| 256 | |
| 257 | if (hsk.nalias) { |
| 258 | int i; |
| 259 | if ((alias = malloc(hsk.nalias * sizeof(char *))) == 0) |
| 260 | goto tidy_1; |
| 261 | for (i = 0; i < hsk.nalias; i++) |
| 262 | alias[i] = 0; |
| 263 | for (i = 0; i < hsk.nalias; i++) { |
| 264 | if ((alias[i] = getstring(fd)) == 0) |
| 265 | goto tidy_2; |
| 266 | sz += strlen(alias[i]) + 1; |
| 267 | } |
| 268 | } |
| 269 | |
| 270 | /* --- Allocate the output structure --- */ |
| 271 | |
| 272 | if ((h = malloc(sz)) == 0) |
| 273 | goto tidy_2; |
| 274 | } |
| 275 | |
| 276 | /* --- Fill in the base structure --- */ |
| 277 | |
| 278 | h->h_addrtype = hsk.addrtype; |
| 279 | h->h_length = hsk.addrsz; |
| 280 | |
| 281 | /* --- Start putting everything else in --- */ |
| 282 | |
| 283 | { |
| 284 | char **p = (char **)(h + 1); |
| 285 | char *a = (char *)(p + hsk.nalias + hsk.naddr + 2); |
| 286 | int i; |
| 287 | |
| 288 | /* --- Start with the address table --- */ |
| 289 | |
| 290 | h->h_addr_list = p; |
| 291 | if (doread(fd, a, hsk.naddr * hsk.addrsz)) |
| 292 | goto tidy_2; |
| 293 | for (i = 0; i < hsk.naddr; i++) { |
| 294 | *p++ = a; |
| 295 | a += hsk.addrsz; |
| 296 | } |
| 297 | *p++ = 0; |
| 298 | |
| 299 | /* --- Finally copy the strings over --- */ |
| 300 | |
| 301 | #define PUT(_p) do { \ |
| 302 | size_t _len = strlen(_p) + 1; \ |
| 303 | memcpy(a, (_p), _len); \ |
| 304 | a += _len; \ |
| 305 | } while (0) |
| 306 | |
| 307 | h->h_name = a; |
| 308 | PUT(name); |
| 309 | free(name); |
| 310 | h->h_aliases = p; |
| 311 | for (i = 0; i < hsk.nalias; i++) { |
| 312 | *p++ = a; |
| 313 | PUT(alias[i]); |
| 314 | free(alias[i]); |
| 315 | } |
| 316 | *p++ = 0; |
| 317 | free(alias); |
| 318 | |
| 319 | #undef PUT |
| 320 | } |
| 321 | |
| 322 | return (h); |
| 323 | |
| 324 | /* --- Tidy up after various types of failure --- */ |
| 325 | |
| 326 | tidy_2: |
| 327 | { |
| 328 | int i; |
| 329 | for (i = 0; i < hsk.nalias && alias[i]; i++) |
| 330 | free(alias[i]); |
| 331 | free(alias); |
| 332 | } |
| 333 | tidy_1: |
| 334 | free(name); |
| 335 | tidy_0: |
| 336 | return (0); |
| 337 | } |
| 338 | |
| 339 | #endif |
| 340 | |
| 341 | /* --- @puthost@ --- * |
| 342 | * |
| 343 | * Arguments: @int fd@ = file descriptor |
| 344 | * @struct hostent *h@ = pointer to host structure |
| 345 | * |
| 346 | * Returns: Zero if successful. |
| 347 | * |
| 348 | * Use: Encodes a host structure. |
| 349 | */ |
| 350 | |
| 351 | static int puthost(int fd, struct hostent *h) |
| 352 | { |
| 353 | hostskel hsk; |
| 354 | int i; |
| 355 | |
| 356 | /* --- Fill in and send the skeleton structure --- */ |
| 357 | |
| 358 | for (i = 0; h->h_aliases[i]; i++) |
| 359 | ; |
| 360 | hsk.nalias = i; |
| 361 | for (i = 0; h->h_addr_list[i]; i++) |
| 362 | ; |
| 363 | hsk.naddr = i; |
| 364 | hsk.addrtype = h->h_addrtype; |
| 365 | hsk.addrsz = h->h_length; |
| 366 | if (dowrite(fd, &hsk, sizeof(hsk))) |
| 367 | return (-1); |
| 368 | |
| 369 | /* --- Send the name and alias strings --- */ |
| 370 | |
| 371 | if (putstring(fd, h->h_name)) |
| 372 | return (-1); |
| 373 | for (i = 0; h->h_aliases[i]; i++) { |
| 374 | if (putstring(fd, h->h_aliases[i])) |
| 375 | return (-1); |
| 376 | } |
| 377 | |
| 378 | /* --- Send the address data --- */ |
| 379 | |
| 380 | for (i = 0; h->h_addr_list[i]; i++) { |
| 381 | if (dowrite(fd, h->h_addr_list[i], hsk.addrsz)) |
| 382 | return (-1); |
| 383 | } |
| 384 | |
| 385 | /* --- OK, done --- */ |
| 386 | |
| 387 | return (0); |
| 388 | } |
| 389 | |
| 390 | /*----- Resolver server ---------------------------------------------------*/ |
| 391 | |
| 392 | /* --- @child@ --- * |
| 393 | * |
| 394 | * Arguments: @int rfd@ = output file descriptor for resolved hostnames |
| 395 | * @int cfd@ = input file descriptor for raw addresses |
| 396 | * |
| 397 | * Returns: Never. |
| 398 | * |
| 399 | * Use: Asynchronous name resolving process. |
| 400 | */ |
| 401 | |
| 402 | static void child(int rfd, int cfd) |
| 403 | { |
| 404 | /* --- Close other file descriptors --- */ |
| 405 | |
| 406 | { |
| 407 | int i; |
| 408 | #if defined(_SC_OPEN_MAX) |
| 409 | int maxfd = sysconf(_SC_OPEN_MAX); |
| 410 | #elif defined(OPEN_MAX) |
| 411 | int maxfd = OPEN_MAX; |
| 412 | #else |
| 413 | int maxfd = -1; |
| 414 | #endif |
| 415 | |
| 416 | if (maxfd < 0) |
| 417 | maxfd = 256; /* Fingers crossed... */ |
| 418 | for (i = 0; i < maxfd; i++) { |
| 419 | if (i != rfd && i != cfd && i != 1) |
| 420 | close(i); |
| 421 | } |
| 422 | } |
| 423 | |
| 424 | signal(SIGTERM, SIG_DFL); |
| 425 | signal(SIGHUP, SIG_DFL); |
| 426 | signal(SIGQUIT, SIG_DFL); |
| 427 | signal(SIGALRM, SIG_DFL); |
| 428 | signal(SIGINT, SIG_DFL); |
| 429 | |
| 430 | /* --- Main request/response loop --- */ |
| 431 | |
| 432 | for (;;) { |
| 433 | int req, resp; |
| 434 | struct hostent *h; |
| 435 | |
| 436 | /* --- Read the request --- */ |
| 437 | |
| 438 | if (doread(cfd, &req, sizeof(req))) |
| 439 | goto lose; |
| 440 | |
| 441 | /* --- Process it into a host structure --- */ |
| 442 | |
| 443 | switch (req) { |
| 444 | |
| 445 | /* --- Normal forward lookup --- */ |
| 446 | |
| 447 | case BRES_BYNAME: { |
| 448 | char *name = getstring(cfd); |
| 449 | if (!name) |
| 450 | goto lose; |
| 451 | h = gethostbyname(name); |
| 452 | free(name); |
| 453 | } break; |
| 454 | |
| 455 | /* --- Reverse lookup --- */ |
| 456 | |
| 457 | case BRES_BYADDR: { |
| 458 | struct in_addr addr; |
| 459 | char *p; |
| 460 | if (doread(cfd, &addr, sizeof(addr))) |
| 461 | goto lose; |
| 462 | if ((h = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET)) == 0) |
| 463 | goto fail; |
| 464 | |
| 465 | /* --- Do a forward lookup to confirm --- */ |
| 466 | |
| 467 | { |
| 468 | size_t sz = strlen(h->h_name) + 1; |
| 469 | if ((p = malloc(sz)) == 0) |
| 470 | goto fail; |
| 471 | memcpy(p, h->h_name, sz); |
| 472 | } |
| 473 | |
| 474 | h = gethostbyname(p); |
| 475 | free(p); |
| 476 | if (!h) |
| 477 | goto fail; |
| 478 | p = 0; |
| 479 | if (h) { |
| 480 | char **pp; |
| 481 | for (pp = h->h_addr_list; *pp; pp++) { |
| 482 | struct in_addr a; |
| 483 | memcpy(&a, *pp, sizeof(a)); |
| 484 | if (a.s_addr == addr.s_addr) { |
| 485 | p = h->h_name; |
| 486 | break; |
| 487 | } |
| 488 | } |
| 489 | } |
| 490 | if (!p) { |
| 491 | h = 0; |
| 492 | h_errno = NO_RECOVERY; |
| 493 | } |
| 494 | fail:; |
| 495 | } break; |
| 496 | |
| 497 | /* --- Unknown request -- may have lost sync --- */ |
| 498 | |
| 499 | default: |
| 500 | goto lose; |
| 501 | } |
| 502 | |
| 503 | /* --- Transmit the response --- */ |
| 504 | |
| 505 | if (h) { |
| 506 | resp = BRES_HOSTENT; |
| 507 | if (dowrite(rfd, &resp, sizeof(resp)) || puthost(rfd, h)) |
| 508 | goto lose; |
| 509 | } else { |
| 510 | resp = BRES_ERROR; |
| 511 | if (dowrite(rfd, &resp, sizeof(resp)) || |
| 512 | dowrite(rfd, &h_errno, sizeof(h_errno))) |
| 513 | goto lose; |
| 514 | } |
| 515 | } |
| 516 | |
| 517 | lose: |
| 518 | _exit(1); |
| 519 | } |
| 520 | |
| 521 | /* --- @main@ --- * |
| 522 | * |
| 523 | * Arguments: @int argc@ = number of command line arguments |
| 524 | * @char *argv[]@ = array of arguments |
| 525 | * |
| 526 | * Returns: Runs until killed or an error occurs. |
| 527 | * |
| 528 | * Use: A name resolver server process for mLib programs which need |
| 529 | * this sort of thing. |
| 530 | */ |
| 531 | |
| 532 | #ifdef BRES_STANDALONE |
| 533 | |
| 534 | int main(int argc, char *argv[]) |
| 535 | { |
| 536 | if (isatty(STDIN_FILENO)) { |
| 537 | char *p = strrchr(argv[0], '/'); |
| 538 | if (p) |
| 539 | p++; |
| 540 | else |
| 541 | p = argv[0]; |
| 542 | fprintf(stderr, |
| 543 | "%s: don't run this program unless you know what you're doing.\n", |
| 544 | p); |
| 545 | exit(1); |
| 546 | } |
| 547 | child(STDOUT_FILENO, STDIN_FILENO); |
| 548 | return (1); |
| 549 | } |
| 550 | |
| 551 | #endif |
| 552 | |
| 553 | /*----- Main code ---------------------------------------------------------*/ |
| 554 | |
| 555 | #ifndef BRES_STANDALONE |
| 556 | |
| 557 | /* --- @zap@ --- * |
| 558 | * |
| 559 | * Arguments: @bres_server *rs@ = pointer to server block |
| 560 | * |
| 561 | * Returns: --- |
| 562 | * |
| 563 | * Use: Kills a server process, reaps the losing child and makes |
| 564 | * things generally clean again. |
| 565 | */ |
| 566 | |
| 567 | static void zap(bres_server *rs) |
| 568 | { |
| 569 | /* --- Close the pipes, kill the child, and reap it --- */ |
| 570 | |
| 571 | if (rs->kid != -1) { |
| 572 | close(rs->fd); |
| 573 | close(rs->f.fd); |
| 574 | kill(rs->kid, SIGTERM); |
| 575 | waitpid(rs->kid, 0, 0); |
| 576 | rs->kid = -1; |
| 577 | } |
| 578 | |
| 579 | /* --- Move the server to the back of the list --- */ |
| 580 | |
| 581 | rs->next->prev = rs->prev; |
| 582 | rs->prev->next = rs->next; |
| 583 | rs->next = FREE; |
| 584 | rs->prev = FREE->prev; |
| 585 | FREE->prev->next = rs; |
| 586 | FREE->prev = rs; |
| 587 | } |
| 588 | |
| 589 | /* --- @bres_abort@ --- * |
| 590 | * |
| 591 | * Arguments: @bres_client *rc@ = pointer to client block |
| 592 | * |
| 593 | * Returns: --- |
| 594 | * |
| 595 | * Use: Removes a queued job. |
| 596 | */ |
| 597 | |
| 598 | void bres_abort(bres_client *rc) |
| 599 | { |
| 600 | if (rc->q == BRES_BYNAME) |
| 601 | xfree(rc->u.name); |
| 602 | if (rc->rs) { |
| 603 | sel_rmfile(&rc->rs->f); |
| 604 | zap(rc->rs); |
| 605 | rc->rs = 0; |
| 606 | } else { |
| 607 | rc->next->prev = rc->prev; |
| 608 | rc->prev->next = rc->next; |
| 609 | } |
| 610 | } |
| 611 | |
| 612 | /* --- @idle@ --- * |
| 613 | * |
| 614 | * Arguments: @struct timeval *tv@ = pointer to the current time |
| 615 | * @void *vp@ = pointer to a server block |
| 616 | * |
| 617 | * Returns: --- |
| 618 | * |
| 619 | * Use: Kills off a child which has been idle for too long. |
| 620 | */ |
| 621 | |
| 622 | static void idle(struct timeval *tv, void *vp) |
| 623 | { |
| 624 | bres_server *rs = vp; |
| 625 | zap(rs); |
| 626 | } |
| 627 | |
| 628 | /* --- @answer@ --- * |
| 629 | * |
| 630 | * Arguments: @int fd@ = file descriptor which is ready |
| 631 | * @unsigned mode@ = what it's doing now |
| 632 | * @void *vp@ = pointer to server block |
| 633 | * |
| 634 | * Returns: --- |
| 635 | * |
| 636 | * Use: Retrieves an answer from a name resolver process. |
| 637 | */ |
| 638 | |
| 639 | static void attach(bres_client */*rc*/); |
| 640 | |
| 641 | static void answer(int fd, unsigned mode, void *vp) |
| 642 | { |
| 643 | bres_server *rs = vp; |
| 644 | bres_client *rc = rs->rc; |
| 645 | struct hostent *h = 0; |
| 646 | int resp; |
| 647 | int fail = 1; |
| 648 | |
| 649 | /* --- Report the result to my client --- */ |
| 650 | |
| 651 | sel_rmfile(&rs->f); |
| 652 | h_errno = -1; |
| 653 | if (doread(fd, &resp, sizeof(resp)) == 0) { |
| 654 | switch (resp) { |
| 655 | case BRES_ERROR: |
| 656 | doread(fd, &h_errno, sizeof(h_errno)); |
| 657 | fail = 0; |
| 658 | break; |
| 659 | case BRES_HOSTENT: |
| 660 | h = gethost(fd); |
| 661 | fail = 0; |
| 662 | break; |
| 663 | } |
| 664 | } |
| 665 | if (rc) { |
| 666 | rc->func(h, rc->p); |
| 667 | if (rc->q == BRES_BYNAME) |
| 668 | xfree(rc->u.name); |
| 669 | } |
| 670 | if (h) |
| 671 | free(h); |
| 672 | if (fail) |
| 673 | zap(rs); |
| 674 | if (!rc) |
| 675 | return; |
| 676 | |
| 677 | /* --- Wrap up the various structures --- */ |
| 678 | |
| 679 | rs->rc = 0; |
| 680 | rc->rs = 0; |
| 681 | rs->next = FREE->next; |
| 682 | rs->prev = FREE; |
| 683 | FREE->next->prev = rs; |
| 684 | FREE->next = rs; |
| 685 | |
| 686 | /* --- Tie a timer onto the server block --- */ |
| 687 | |
| 688 | { |
| 689 | struct timeval tv; |
| 690 | |
| 691 | gettimeofday(&tv, 0); |
| 692 | tv.tv_sec += BRES_IDLE; |
| 693 | sel_addtimer(sel, &rs->t, &tv, idle, rs); |
| 694 | } |
| 695 | |
| 696 | /* --- If there are any clients waiting, attach one --- */ |
| 697 | |
| 698 | if (QUEUE->next != QUEUE) { |
| 699 | rc = QUEUE->next; |
| 700 | QUEUE->next = rc->next; |
| 701 | rc->next->prev = QUEUE; |
| 702 | attach(rc); |
| 703 | } |
| 704 | } |
| 705 | |
| 706 | /* --- @start@ --- * |
| 707 | * |
| 708 | * Arguments: @bres_server *rs@ = pointer to a server block |
| 709 | * |
| 710 | * Returns: Zero if OK, nonzero if something failed. |
| 711 | * |
| 712 | * Use: Starts up a child resolver process. |
| 713 | */ |
| 714 | |
| 715 | static int start(bres_server *rs) |
| 716 | { |
| 717 | int rfd[2], cfd[2]; |
| 718 | pid_t kid; |
| 719 | |
| 720 | /* --- Make the pipes --- */ |
| 721 | |
| 722 | if (pipe(rfd)) |
| 723 | goto fail_0; |
| 724 | if (pipe(cfd)) |
| 725 | goto fail_1; |
| 726 | |
| 727 | /* --- Start up the child process --- */ |
| 728 | |
| 729 | if ((kid = fork()) < 0) |
| 730 | goto fail_2; |
| 731 | if (kid == 0) { |
| 732 | close(cfd[1]); |
| 733 | close(rfd[0]); |
| 734 | |
| 735 | if (server) { |
| 736 | dup2(cfd[0], STDIN_FILENO); |
| 737 | dup2(rfd[1], STDOUT_FILENO); |
| 738 | close(cfd[0]); |
| 739 | close(rfd[1]); |
| 740 | execlp(server, server, (char *)0); |
| 741 | child(STDOUT_FILENO, STDIN_FILENO); |
| 742 | } else |
| 743 | child(rfd[1], cfd[0]); |
| 744 | _exit(1); |
| 745 | } |
| 746 | |
| 747 | /* --- Fix up everything in the server block --- */ |
| 748 | |
| 749 | close(cfd[0]); |
| 750 | close(rfd[1]); |
| 751 | rs->fd = cfd[1]; |
| 752 | sel_initfile(sel, &rs->f, rfd[0], SEL_READ, answer, rs); |
| 753 | rs->kid = kid; |
| 754 | return (0); |
| 755 | |
| 756 | /* --- Fix up after errors --- */ |
| 757 | |
| 758 | fail_2: |
| 759 | close(cfd[0]); |
| 760 | close(cfd[1]); |
| 761 | fail_1: |
| 762 | close(rfd[0]); |
| 763 | close(rfd[1]); |
| 764 | fail_0: |
| 765 | return (-1); |
| 766 | } |
| 767 | |
| 768 | /* --- @attach@ --- * |
| 769 | * |
| 770 | * Arguments: @bres_client *rc@ = pointer to a client block |
| 771 | * |
| 772 | * Returns: --- |
| 773 | * |
| 774 | * Use: Attaches a client to a spare server (which is assumed to |
| 775 | * exist). |
| 776 | */ |
| 777 | |
| 778 | static void attach(bres_client *rc) |
| 779 | { |
| 780 | bres_server *rs; |
| 781 | int lose = 0; |
| 782 | |
| 783 | /* --- Fix up the server ready for the job --- * |
| 784 | * |
| 785 | * If the server has a process, remove its timer. Otherwise, fork off a |
| 786 | * new resolver process. This is also where I go if I find that the child |
| 787 | * resolver process has lost while I wasn't looking. Only one attempt at |
| 788 | * forking is performed. |
| 789 | */ |
| 790 | |
| 791 | again: |
| 792 | rs = FREE->next; |
| 793 | if (rs->kid != -1) |
| 794 | sel_rmtimer(&rs->t); |
| 795 | else { |
| 796 | if (lose || start(rs)) |
| 797 | goto lost; |
| 798 | lose = 1; |
| 799 | } |
| 800 | |
| 801 | /* --- Submit the job to the resolver --- */ |
| 802 | |
| 803 | { |
| 804 | struct sigaction sa, osa; |
| 805 | int e; |
| 806 | |
| 807 | /* --- Ignore @SIGPIPE@ for now --- * |
| 808 | * |
| 809 | * This way I can trap @EPIPE@ and reap a losing child, if there was one. |
| 810 | */ |
| 811 | |
| 812 | sa.sa_handler = SIG_IGN; |
| 813 | sa.sa_flags = 0; |
| 814 | sigemptyset(&sa.sa_mask); |
| 815 | sigaction(SIGPIPE, &sa, &osa); |
| 816 | |
| 817 | /* --- Write the new job to the child --- */ |
| 818 | |
| 819 | e = 0; |
| 820 | if (dowrite(rs->fd, &rc->q, sizeof(rc->q))) |
| 821 | e = errno; |
| 822 | else switch (rc->q) { |
| 823 | case BRES_BYADDR: |
| 824 | if (dowrite(rs->fd, &rc->u.addr, sizeof(rc->u.addr))) |
| 825 | e = errno; |
| 826 | break; |
| 827 | case BRES_BYNAME: |
| 828 | if (putstring(rs->fd, rc->u.name)) |
| 829 | e = errno; |
| 830 | break; |
| 831 | } |
| 832 | sigaction(SIGPIPE, &osa, 0); |
| 833 | |
| 834 | /* --- Sort out various errors --- * |
| 835 | * |
| 836 | * This was once more complicated, handling @EPIPE@ separately from other |
| 837 | * errors. Now everything's handled the same way. |
| 838 | */ |
| 839 | |
| 840 | if (e) { |
| 841 | zap(rs); |
| 842 | goto again; |
| 843 | } |
| 844 | } |
| 845 | |
| 846 | /* --- Fiddle with lists so that everything's OK --- */ |
| 847 | |
| 848 | sel_addfile(&rs->f); |
| 849 | rs->next->prev = FREE; |
| 850 | FREE->next = rs->next; |
| 851 | rs->next = rs->prev = rs; |
| 852 | rs->rc = rc; |
| 853 | rc->rs = rs; |
| 854 | return; |
| 855 | |
| 856 | lost: |
| 857 | rc->func(0, rc->p); |
| 858 | if (rc->q == BRES_BYNAME) |
| 859 | xfree(rc->u.name); |
| 860 | } |
| 861 | |
| 862 | /* --- @resolve@ --- * |
| 863 | * |
| 864 | * Arguments: @bres_client *rc@ = pointer to filled-in client block |
| 865 | * |
| 866 | * Returns: --- |
| 867 | * |
| 868 | * Use: Dispatcher for incoming resolution jobs. |
| 869 | */ |
| 870 | |
| 871 | static void resolve(bres_client *rc) |
| 872 | { |
| 873 | /* --- If there's a free server, plug it in --- */ |
| 874 | |
| 875 | rc->rs = 0; |
| 876 | if (FREE->next == FREE) { |
| 877 | rc->next = QUEUE; |
| 878 | rc->prev = QUEUE->prev; |
| 879 | QUEUE->prev->next = rc; |
| 880 | QUEUE->prev = rc; |
| 881 | } else |
| 882 | attach(rc); |
| 883 | } |
| 884 | |
| 885 | /* --- @bres_byaddr@ --- * |
| 886 | * |
| 887 | * Arguments: @bres_client *rc@ = pointer to client block |
| 888 | * @struct in_addr addr@ = address to resolve |
| 889 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
| 890 | * @void *p@ = argument for handler function |
| 891 | * |
| 892 | * Returns: --- |
| 893 | * |
| 894 | * Use: Adds an address lookup job to the queue. The job will be |
| 895 | * processed when there's a spare resolver process to deal with |
| 896 | * it. |
| 897 | */ |
| 898 | |
| 899 | void bres_byaddr(bres_client *rc, struct in_addr addr, |
| 900 | void (*func)(struct hostent */*h*/, void */*p*/), |
| 901 | void *p) |
| 902 | { |
| 903 | rc->q = BRES_BYADDR; |
| 904 | rc->u.addr = addr; |
| 905 | rc->func = func; |
| 906 | rc->p = p; |
| 907 | resolve(rc); |
| 908 | } |
| 909 | |
| 910 | /* --- @bres_byname@ --- * |
| 911 | * |
| 912 | * Arguments: @bres_client *rc@ = pointer to client block |
| 913 | * @const char *name@ = name to resolve |
| 914 | * @void (*func)(struct hostent *h, void *p)@ = handler function |
| 915 | * @void *p@ = argument for handler function |
| 916 | * |
| 917 | * Returns: --- |
| 918 | * |
| 919 | * Use: Adds a name lookup job to the queue. The job will be |
| 920 | * processed when there's a spare resolver process to deal with |
| 921 | * it. |
| 922 | */ |
| 923 | |
| 924 | void bres_byname(bres_client *rc, const char *name, |
| 925 | void (*func)(struct hostent */*h*/, void */*p*/), |
| 926 | void *p) |
| 927 | { |
| 928 | rc->q = BRES_BYNAME; |
| 929 | rc->u.name = xstrdup(name); |
| 930 | rc->func = func; |
| 931 | rc->p = p; |
| 932 | resolve(rc); |
| 933 | } |
| 934 | |
| 935 | /* --- @bres_exec@ --- * |
| 936 | * |
| 937 | * Arguments: @const char *file@ = file containing server code or null |
| 938 | * |
| 939 | * Returns: --- |
| 940 | * |
| 941 | * Use: Makes `bres' use a standalone server rather than copies of |
| 942 | * the current process. This can reduce memory consumption for |
| 943 | * large processes, at the expense of startup time (which |
| 944 | * shouldn't be too bad anyway, because of the resolver design). |
| 945 | * If the filename is null, a default set up at install time is |
| 946 | * used. It's probably a good idea to leave it alone. |
| 947 | */ |
| 948 | |
| 949 | void bres_exec(const char *file) |
| 950 | { |
| 951 | if (file) |
| 952 | server = file; |
| 953 | else |
| 954 | server = BRES_SERVER; |
| 955 | } |
| 956 | |
| 957 | /* --- @bres_init@ --- * |
| 958 | * |
| 959 | * Arguments: @sel_state *s@ = pointer to select multiplexor |
| 960 | * |
| 961 | * Returns: --- |
| 962 | * |
| 963 | * Use: Initializes the background resolver for use. |
| 964 | */ |
| 965 | |
| 966 | void bres_init(sel_state *s) |
| 967 | { |
| 968 | int i; |
| 969 | |
| 970 | sel = s; |
| 971 | for (i = 0; i < BRES_MAX; i++) { |
| 972 | servers[i].next = FREE; |
| 973 | servers[i].prev = FREE->prev; |
| 974 | servers[i].kid = -1; |
| 975 | servers[i].rc = 0; |
| 976 | FREE->prev->next = &servers[i]; |
| 977 | FREE->prev = &servers[i]; |
| 978 | } |
| 979 | } |
| 980 | |
| 981 | #endif |
| 982 | |
| 983 | /*----- That's all, folks -------------------------------------------------*/ |