| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: bres.c,v 1.3 1999/07/26 23:27:22 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 `fw' port forwarder. |
| 13 | * |
| 14 | * `fw' is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU General Public License as published by |
| 16 | * the Free Software Foundation; either version 2 of the License, or |
| 17 | * (at your option) any later version. |
| 18 | * |
| 19 | * `fw' 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 General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with `fw'; if not, write to the Free Software Foundation, |
| 26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 27 | */ |
| 28 | |
| 29 | /*----- Revision history --------------------------------------------------* |
| 30 | * |
| 31 | * $Log: bres.c,v $ |
| 32 | * Revision 1.3 1999/07/26 23:27:22 mdw |
| 33 | * Change copyright notice. |
| 34 | * |
| 35 | * Revision 1.2 1999/07/03 13:56:04 mdw |
| 36 | * Perform a forward resolution to verify result of reverse lookup. |
| 37 | * |
| 38 | * Revision 1.1.1.1 1999/07/01 08:56:23 mdw |
| 39 | * Initial revision. |
| 40 | * |
| 41 | */ |
| 42 | |
| 43 | /*----- Header files ------------------------------------------------------*/ |
| 44 | |
| 45 | #include <errno.h> |
| 46 | #include <signal.h> |
| 47 | #include <stdio.h> |
| 48 | #include <stdlib.h> |
| 49 | #include <string.h> |
| 50 | |
| 51 | #include <sys/types.h> |
| 52 | #include <sys/time.h> |
| 53 | #include <unistd.h> |
| 54 | #include <sys/wait.h> |
| 55 | |
| 56 | #include <sys/socket.h> |
| 57 | #include <netinet/in.h> |
| 58 | #include <arpa/inet.h> |
| 59 | #include <netdb.h> |
| 60 | |
| 61 | #include <mLib/alloc.h> |
| 62 | #include <mLib/report.h> |
| 63 | #include <mLib/sel.h> |
| 64 | #include <mLib/selbuf.h> |
| 65 | |
| 66 | #include "bres.h" |
| 67 | |
| 68 | /*----- Magic numbers -----------------------------------------------------*/ |
| 69 | |
| 70 | #define BRES_MAX 5 /* Maximum number of resolvers */ |
| 71 | #define BRES_IDLE 60 /* Lifetime of an idle resolver */ |
| 72 | |
| 73 | /*----- Static variables --------------------------------------------------*/ |
| 74 | |
| 75 | static bres_server servers[BRES_MAX]; /* Statically allocated servers */ |
| 76 | |
| 77 | #define FREE ((bres_server *)&freelist) |
| 78 | static struct { bres_server *next, *prev; } freelist = { FREE, FREE }; |
| 79 | |
| 80 | #define QUEUE ((bres_client *)&queue) |
| 81 | static struct { bres_client *next, *prev; } queue = { QUEUE, QUEUE }; |
| 82 | |
| 83 | static sel_state *sel; |
| 84 | |
| 85 | /*----- Main code ---------------------------------------------------------*/ |
| 86 | |
| 87 | /* --- @zap@ --- * |
| 88 | * |
| 89 | * Arguments: @bres_server *rs@ = pointer to server block |
| 90 | * |
| 91 | * Returns: --- |
| 92 | * |
| 93 | * Use: Kills a server process, reaps the losing child and makes |
| 94 | * things generally clean again. |
| 95 | */ |
| 96 | |
| 97 | static void zap(bres_server *rs) |
| 98 | { |
| 99 | /* --- Close the pipes, kill the child, and reap it --- */ |
| 100 | |
| 101 | if (rs->kid != -1) { |
| 102 | selbuf_disable(&rs->b); |
| 103 | close(rs->fd); |
| 104 | close(rs->b.reader.fd); |
| 105 | kill(rs->kid, SIGTERM); |
| 106 | waitpid(rs->kid, 0, 0); |
| 107 | rs->kid = -1; |
| 108 | } |
| 109 | |
| 110 | /* --- Move the server to the back of the list --- */ |
| 111 | |
| 112 | rs->next->prev = rs->prev; |
| 113 | rs->prev->next = rs->next; |
| 114 | rs->next = FREE; |
| 115 | rs->prev = FREE->prev; |
| 116 | FREE->prev->next = rs; |
| 117 | FREE->prev = rs; |
| 118 | } |
| 119 | |
| 120 | /* --- @bres_abort@ --- * |
| 121 | * |
| 122 | * Arguments: @bres_client *rc@ = pointer to client block |
| 123 | * |
| 124 | * Returns: --- |
| 125 | * |
| 126 | * Use: Removes a queued job. |
| 127 | */ |
| 128 | |
| 129 | void bres_abort(bres_client *rc) |
| 130 | { |
| 131 | if (rc->rs) { |
| 132 | zap(rc->rs); |
| 133 | rc->rs = 0; |
| 134 | } else { |
| 135 | rc->next->prev = rc->prev; |
| 136 | rc->prev->next = rc->next; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | /* --- @child@ --- * |
| 141 | * |
| 142 | * Arguments: @int rfd@ = output file descriptor for resolved hostnames |
| 143 | * @int cfd@ = input file descriptor for raw addresses |
| 144 | * |
| 145 | * Returns: Never. |
| 146 | * |
| 147 | * Use: Asynchronous name resolving process. |
| 148 | */ |
| 149 | |
| 150 | static void child(int rfd, int cfd) |
| 151 | { |
| 152 | struct in_addr addr; |
| 153 | FILE *fp = fdopen(rfd, "w"); |
| 154 | |
| 155 | { |
| 156 | int i; |
| 157 | int maxfd = sysconf(_SC_OPEN_MAX); |
| 158 | |
| 159 | for (i = 0; i < maxfd; i++) { |
| 160 | if (i != rfd && i != cfd) |
| 161 | close(i); |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | for (;;) { |
| 166 | int r = read(cfd, &addr, sizeof(addr)); |
| 167 | struct hostent *h; |
| 168 | char *p; |
| 169 | |
| 170 | if (r <= 0) |
| 171 | break; |
| 172 | else if (r != sizeof(addr)) |
| 173 | continue; |
| 174 | |
| 175 | h = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET); |
| 176 | if (h) { |
| 177 | char **pp; |
| 178 | |
| 179 | p = xstrdup(h->h_name); |
| 180 | h = gethostbyname(p); |
| 181 | free(p); |
| 182 | p = 0; |
| 183 | if (h) { |
| 184 | for (pp = h->h_addr_list; *pp; pp++) { |
| 185 | struct in_addr a; |
| 186 | memcpy(&a, *pp, sizeof(a)); |
| 187 | if (a.s_addr == addr.s_addr) { |
| 188 | p = h->h_name; |
| 189 | break; |
| 190 | } |
| 191 | } |
| 192 | } |
| 193 | } |
| 194 | |
| 195 | if (!p) |
| 196 | p = inet_ntoa(addr); |
| 197 | fprintf(fp, "%s\n", p); |
| 198 | fflush(fp); |
| 199 | } |
| 200 | _exit(0); |
| 201 | } |
| 202 | |
| 203 | /* --- @idle@ --- * |
| 204 | * |
| 205 | * Arguments: @struct timeval *tv@ = pointer to the current time |
| 206 | * @void *vp@ = pointer to a server block |
| 207 | * |
| 208 | * Returns: --- |
| 209 | * |
| 210 | * Use: Kills off a child which has been idle for too long. |
| 211 | */ |
| 212 | |
| 213 | static void idle(struct timeval *tv, void *vp) |
| 214 | { |
| 215 | bres_server *rs = vp; |
| 216 | zap(rs); |
| 217 | } |
| 218 | |
| 219 | /* --- @answer@ --- * |
| 220 | * |
| 221 | * Arguments: @char *p@ = pointer to string read |
| 222 | * @void *vp@ = pointer to server block |
| 223 | * |
| 224 | * Returns: --- |
| 225 | * |
| 226 | * Use: Retrieves an answer from a name resolver process. |
| 227 | */ |
| 228 | |
| 229 | static void attach(bres_client */*rc*/); |
| 230 | |
| 231 | static void answer(char *p, void *vp) |
| 232 | { |
| 233 | bres_server *rs = vp; |
| 234 | bres_client *rc = rs->rc; |
| 235 | |
| 236 | /* --- Report the result to my client --- */ |
| 237 | |
| 238 | if (rc) |
| 239 | rc->func(p, rc->p); |
| 240 | if (!p) |
| 241 | zap(rs); |
| 242 | if (!rc) |
| 243 | return; |
| 244 | |
| 245 | /* --- Wrap up the various structures --- */ |
| 246 | |
| 247 | rs->rc = 0; |
| 248 | rc->rs = 0; |
| 249 | rs->next = FREE->next; |
| 250 | rs->prev = FREE; |
| 251 | FREE->next->prev = rs; |
| 252 | FREE->next = rs; |
| 253 | |
| 254 | /* --- Tie a timer onto the server block --- */ |
| 255 | |
| 256 | { |
| 257 | struct timeval tv; |
| 258 | |
| 259 | gettimeofday(&tv, 0); |
| 260 | tv.tv_sec += BRES_IDLE; |
| 261 | sel_addtimer(sel, &rs->t, &tv, idle, rs); |
| 262 | } |
| 263 | |
| 264 | /* --- If there are any clients waiting, attach one --- */ |
| 265 | |
| 266 | if (QUEUE->next != QUEUE) { |
| 267 | rc = QUEUE->next; |
| 268 | QUEUE->next = rc->next; |
| 269 | rc->next->prev = QUEUE; |
| 270 | attach(rc); |
| 271 | } |
| 272 | } |
| 273 | |
| 274 | /* --- @start@ --- * |
| 275 | * |
| 276 | * Arguments: @bres_server *rs@ = pointer to a server block |
| 277 | * |
| 278 | * Returns: Zero if OK, nonzero if something failed. |
| 279 | * |
| 280 | * Use: Starts up a child resolver process. |
| 281 | */ |
| 282 | |
| 283 | static int start(bres_server *rs) |
| 284 | { |
| 285 | int rfd[2], cfd[2]; |
| 286 | pid_t kid; |
| 287 | |
| 288 | /* --- Make the pipes --- */ |
| 289 | |
| 290 | if (pipe(rfd)) |
| 291 | goto fail_0; |
| 292 | if (pipe(cfd)) |
| 293 | goto fail_1; |
| 294 | |
| 295 | /* --- Start up the child process --- */ |
| 296 | |
| 297 | if ((kid = fork()) < 0) |
| 298 | goto fail_2; |
| 299 | if (kid == 0) { |
| 300 | close(cfd[1]); |
| 301 | close(rfd[0]); |
| 302 | child(rfd[1], cfd[0]); |
| 303 | _exit(1); |
| 304 | } |
| 305 | |
| 306 | /* --- Fix up everything in the server block --- */ |
| 307 | |
| 308 | close(cfd[0]); |
| 309 | close(rfd[1]); |
| 310 | rs->fd = cfd[1]; |
| 311 | selbuf_init(&rs->b, sel, rfd[0], answer, rs); |
| 312 | rs->kid = kid; |
| 313 | return (0); |
| 314 | |
| 315 | /* --- Fix up after errors --- */ |
| 316 | |
| 317 | fail_2: |
| 318 | close(cfd[0]); |
| 319 | close(cfd[1]); |
| 320 | fail_1: |
| 321 | close(rfd[0]); |
| 322 | close(rfd[1]); |
| 323 | fail_0: |
| 324 | return (-1); |
| 325 | } |
| 326 | |
| 327 | /* --- @attach@ --- * |
| 328 | * |
| 329 | * Arguments: @bres_client *rc@ = pointer to a client block |
| 330 | * |
| 331 | * Returns: --- |
| 332 | * |
| 333 | * Use: Attaches a client to a spare server (which is assumed to |
| 334 | * exist). |
| 335 | */ |
| 336 | |
| 337 | static void attach(bres_client *rc) |
| 338 | { |
| 339 | bres_server *rs; |
| 340 | int lose = 0; |
| 341 | |
| 342 | /* --- Fix up the server ready for the job --- * |
| 343 | * |
| 344 | * If the server has a process, remove its timer. Otherwise, fork off a |
| 345 | * new resolver process. This is also where I go if I find that the child |
| 346 | * resolver process has lost while I wasn't looking. Only one attempt at |
| 347 | * forking is performed. |
| 348 | */ |
| 349 | |
| 350 | again: |
| 351 | rs = FREE->next; |
| 352 | if (rs->kid != -1) |
| 353 | sel_rmtimer(&rs->t); |
| 354 | else { |
| 355 | if (lose || start(rs)) |
| 356 | goto lost; |
| 357 | lose = 1; |
| 358 | } |
| 359 | |
| 360 | /* --- Submit the job to the resolver --- */ |
| 361 | |
| 362 | { |
| 363 | struct sigaction sa, osa; |
| 364 | int e; |
| 365 | |
| 366 | /* --- Ignore @SIGPIPE@ for now --- * |
| 367 | * |
| 368 | * This way I can trap @EPIPE@ and reap a losing child, if there was one. |
| 369 | */ |
| 370 | |
| 371 | sa.sa_handler = SIG_IGN; |
| 372 | sa.sa_flags = 0; |
| 373 | sigemptyset(&sa.sa_mask); |
| 374 | sigaction(SIGPIPE, &sa, &osa); |
| 375 | |
| 376 | /* --- Write the new job to the child --- */ |
| 377 | |
| 378 | e = 0; |
| 379 | if (write(rs->fd, &rc->addr, sizeof(rc->addr)) < 0) |
| 380 | e = errno; |
| 381 | sigaction(SIGPIPE, &osa, 0); |
| 382 | |
| 383 | /* --- Sort out various errors --- */ |
| 384 | |
| 385 | if (e == EPIPE) { |
| 386 | zap(rs); |
| 387 | goto again; |
| 388 | } else if (e) |
| 389 | goto lost; |
| 390 | } |
| 391 | |
| 392 | /* --- Fiddle with lists so that everything's OK --- */ |
| 393 | |
| 394 | rs->next->prev = FREE; |
| 395 | FREE->next = rs->next; |
| 396 | rs->next = rs->prev = rs; |
| 397 | rs->rc = rc; |
| 398 | rc->rs = rs; |
| 399 | return; |
| 400 | |
| 401 | lost: |
| 402 | rc->func(0, rc->p); |
| 403 | } |
| 404 | |
| 405 | /* --- @bres_resolve@ --- * |
| 406 | * |
| 407 | * Arguments: @bres_client *rc@ = pointer to client block |
| 408 | * @struct in_addr addr@ = address to resolve |
| 409 | * @void (*func)(const char *host, void *p)@ = handler function |
| 410 | * @void *p@ = argument for handler function |
| 411 | * |
| 412 | * Returns: --- |
| 413 | * |
| 414 | * Use: Adds a resolver job to the queue. The job will be processed |
| 415 | * when there's a spare resolver process to deal with it. |
| 416 | */ |
| 417 | |
| 418 | void bres_resolve(bres_client *rc, struct in_addr addr, |
| 419 | void (*func)(const char */*host*/, void */*p*/), void *p) |
| 420 | { |
| 421 | /* --- Fill in the structure --- */ |
| 422 | |
| 423 | rc->addr = addr; |
| 424 | rc->func = func; |
| 425 | rc->p = p; |
| 426 | rc->rs = 0; |
| 427 | |
| 428 | /* --- If there's a free server, plug it in --- */ |
| 429 | |
| 430 | if (FREE->next == FREE) { |
| 431 | rc->next = QUEUE; |
| 432 | rc->prev = QUEUE->prev; |
| 433 | QUEUE->prev->next = rc; |
| 434 | QUEUE->prev = rc; |
| 435 | } else |
| 436 | attach(rc); |
| 437 | } |
| 438 | |
| 439 | /* --- @bres_init@ --- * |
| 440 | * |
| 441 | * Arguments: @sel_state *s@ = pointer to select multiplexor |
| 442 | * |
| 443 | * Returns: --- |
| 444 | * |
| 445 | * Use: Initializes the background resolver for use. |
| 446 | */ |
| 447 | |
| 448 | void bres_init(sel_state *s) |
| 449 | { |
| 450 | int i; |
| 451 | |
| 452 | sel = s; |
| 453 | for (i = 0; i < BRES_MAX; i++) { |
| 454 | servers[i].next = FREE; |
| 455 | servers[i].prev = FREE->prev; |
| 456 | servers[i].kid = -1; |
| 457 | servers[i].rc = 0; |
| 458 | FREE->prev->next = &servers[i]; |
| 459 | FREE->prev = &servers[i]; |
| 460 | } |
| 461 | } |
| 462 | |
| 463 | /*----- That's all, folks -------------------------------------------------*/ |