yp_dnslookup.c revision 145792
1/* 2 * Copyright (c) 1995, 1996 3 * Bill Paul <wpaul@ctr.columbia.edu>. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by Bill Paul. 16 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL Bill Paul OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33#include <sys/cdefs.h> 34__FBSDID("$FreeBSD: head/usr.sbin/ypserv/yp_dnslookup.c 145792 2005-05-02 09:34:07Z ume $"); 35 36/* 37 * Do standard and reverse DNS lookups using the resolver library. 38 * Take care of all the dirty work here so the main program only has to 39 * pass us a pointer to an array of characters. 40 * 41 * We have to use direct resolver calls here otherwise the YP server 42 * could end up looping by calling itself over and over again until 43 * it disappeared up its own belly button. 44 */ 45 46#include <sys/param.h> 47#include <sys/socket.h> 48#include <sys/time.h> 49#include <sys/fcntl.h> 50#include <sys/queue.h> 51#include <netinet/in.h> 52#include <arpa/inet.h> 53#include <arpa/nameser.h> 54 55#include <ctype.h> 56#include <errno.h> 57#include <netdb.h> 58#include <stdio.h> 59#include <stdlib.h> 60#include <string.h> 61#include <resolv.h> 62#include <unistd.h> 63 64#include <rpcsvc/yp.h> 65#include "yp_extern.h" 66 67static char * 68parse(struct hostent *hp) 69{ 70 static char result[MAXHOSTNAMELEN * 2]; 71 int len,i; 72 char addr[46]; 73 74 if (hp == NULL) 75 return(NULL); 76 77 if (inet_ntop(hp->h_addrtype, hp->h_addr, addr, sizeof(addr)) == NULL) 78 return(NULL); 79 80 len = strlen(addr) + 1 + strlen(hp->h_name); 81 for (i = 0; hp->h_aliases[i]; i++) 82 len += strlen(hp->h_aliases[i]) + 1; 83 len++; 84 85 if (len > sizeof(result)) 86 return(NULL); 87 88 bzero(result, sizeof(result)); 89 snprintf(result, sizeof(result), "%s %s", addr, hp->h_name); 90 for (i = 0; hp->h_aliases[i]; i++) { 91 strcat(result, " "); 92 strcat(result, hp->h_aliases[i]); 93 } 94 95 return ((char *)&result); 96} 97 98#define MAXPACKET (64*1024) 99#define DEF_TTL 50 100 101#define BY_DNS_ID 1 102#define BY_RPC_XID 2 103 104extern struct hostent *__dns_getanswer(char *, int, char *, int); 105 106static TAILQ_HEAD(dns_qhead, circleq_dnsentry) qhead; 107 108struct circleq_dnsentry { 109 SVCXPRT *xprt; 110 unsigned long xid; 111 struct sockaddr_in client_addr; 112 unsigned long ypvers; 113 unsigned long id; 114 unsigned long ttl; 115 unsigned long type; 116 unsigned short prot_type; 117 char **domain; 118 char *name; 119 int addrtype; 120 int addrlen; 121 uint32_t addr[4]; /* IPv4 or IPv6 */ 122 TAILQ_ENTRY(circleq_dnsentry) links; 123}; 124 125static int pending = 0; 126 127int 128yp_init_resolver(void) 129{ 130 TAILQ_INIT(&qhead); 131 if (!(_res.options & RES_INIT) && res_init() == -1) { 132 yp_error("res_init failed"); 133 return(1); 134 } 135 if ((resfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { 136 yp_error("couldn't create socket"); 137 return(1); 138 } 139 if (fcntl(resfd, F_SETFL, O_NONBLOCK) == -1) { 140 yp_error("couldn't make resolver socket non-blocking"); 141 return(1); 142 } 143 return(0); 144} 145 146static struct 147circleq_dnsentry *yp_malloc_dnsent(void) 148{ 149 register struct circleq_dnsentry *q; 150 151 q = (struct circleq_dnsentry *)malloc(sizeof(struct circleq_dnsentry)); 152 153 if (q == NULL) { 154 yp_error("failed to malloc() circleq dns entry"); 155 return(NULL); 156 } 157 158 return(q); 159} 160 161/* 162 * Transmit a query. 163 */ 164static unsigned long 165yp_send_dns_query(char *name, int type) 166{ 167 char buf[MAXPACKET]; 168 int n; 169 HEADER *hptr; 170 int ns; 171 int rval; 172 unsigned long id; 173 174 bzero(buf, sizeof(buf)); 175 176 n = res_mkquery(QUERY,name,C_IN,type,NULL,0,NULL,buf,sizeof(buf)); 177 178 if (n <= 0) { 179 yp_error("res_mkquery failed for %s type %d", name, type); 180 return(0); 181 } 182 183 hptr = (HEADER *)&buf; 184 id = ntohs(hptr->id); 185 186 for (ns = 0; ns < _res.nscount; ns++) { 187 rval = sendto(resfd, buf, n, 0, 188 (struct sockaddr *)&_res.nsaddr_list[ns], 189 sizeof(struct sockaddr)); 190 if (rval == -1) { 191 yp_error("sendto failed"); 192 return(0); 193 } 194 } 195 196 return(id); 197} 198 199static struct circleq_dnsentry * 200yp_find_dnsqent(unsigned long id, int type) 201{ 202 register struct circleq_dnsentry *q; 203 204 TAILQ_FOREACH(q, &qhead, links) { 205 switch (type) { 206 case BY_RPC_XID: 207 if (id == q->xid) 208 return(q); 209 break; 210 case BY_DNS_ID: 211 default: 212 if (id == q->id) 213 return(q); 214 break; 215 } 216 } 217 return (NULL); 218} 219 220static void 221yp_send_dns_reply(struct circleq_dnsentry *q, char *buf) 222{ 223 ypresponse result_v1; 224 ypresp_val result_v2; 225 unsigned long xid; 226 struct sockaddr_in client_addr; 227 xdrproc_t xdrfunc; 228 char *result; 229 230 /* 231 * Set up correct reply struct and 232 * XDR filter depending on ypvers. 233 */ 234 switch (q->ypvers) { 235 case YPVERS: 236 bzero((char *)&result_v2, sizeof(result_v2)); 237 238 if (buf == NULL) 239 result_v2.stat = YP_NOKEY; 240 else { 241 result_v2.val.valdat_len = strlen(buf); 242 result_v2.val.valdat_val = buf; 243 result_v2.stat = YP_TRUE; 244 } 245 result = (char *)&result_v2; 246 xdrfunc = (xdrproc_t)xdr_ypresp_val; 247 break; 248 case YPOLDVERS: 249 /* 250 * The odds are we will _never_ execute this 251 * particular code, but we include it anyway 252 * for the sake of completeness. 253 */ 254 bzero((char *)&result_v1, sizeof(result_v1)); 255 result_v1.yp_resptype = YPRESP_VAL; 256 257#define YPVAL ypresponse_u.yp_resp_valtype 258 if (buf == NULL) 259 result_v1.YPVAL.stat = YP_NOKEY; 260 else { 261 result_v1.YPVAL.val.valdat_len = strlen(buf); 262 result_v1.YPVAL.val.valdat_val = buf; 263 result_v1.YPVAL.stat = YP_TRUE; 264 } 265 result = (char *)&result_v1; 266 xdrfunc = (xdrproc_t)xdr_ypresponse; 267 break; 268 default: 269 yp_error("bad YP program version (%lu)!", q->ypvers); 270 return; 271 break; 272 } 273 274 if (debug) 275 yp_error("sending dns reply to %s (%lu)", 276 inet_ntoa(q->client_addr.sin_addr), q->id); 277 /* 278 * XXX This is disgusting. There's basically one transport 279 * handle for UDP, but we're holding off on replying to a 280 * client until we're ready, by which time we may have received 281 * several other queries from other clients with different 282 * transaction IDs. So to make the delayed response thing work, 283 * we have to save the transaction ID and client address of 284 * each request, then jam them into the transport handle when 285 * we're ready to send a reply. Then after we've send the reply, 286 * we put the old transaction ID and remote address back the 287 * way we found 'em. This is _INCREDIBLY_ non-portable; it's 288 * not even supported by the RPC library. 289 */ 290 /* 291 * XXX Don't frob the transaction ID for TCP handles. 292 */ 293 if (q->prot_type == SOCK_DGRAM) 294 xid = svcudp_set_xid(q->xprt, q->xid); 295 client_addr = q->xprt->xp_raddr; 296 q->xprt->xp_raddr = q->client_addr; 297 298 if (!svc_sendreply(q->xprt, xdrfunc, result)) 299 yp_error("svc_sendreply failed"); 300 301 /* 302 * Now that we sent the reply, 303 * put the handle back the way it was. 304 */ 305 if (q->prot_type == SOCK_DGRAM) 306 svcudp_set_xid(q->xprt, xid); 307 q->xprt->xp_raddr = client_addr; 308 309 return; 310} 311 312/* 313 * Decrement TTL on all queue entries, possibly nuking 314 * any that have been around too long without being serviced. 315 */ 316void 317yp_prune_dnsq(void) 318{ 319 register struct circleq_dnsentry *q, *n; 320 321 q = TAILQ_FIRST(&qhead); 322 while (q != NULL) { 323 q->ttl--; 324 n = TAILQ_NEXT(q, links); 325 if (!q->ttl) { 326 TAILQ_REMOVE(&qhead, q, links); 327 free(q->name); 328 free(q); 329 pending--; 330 } 331 q = n; 332 } 333 334 if (pending < 0) 335 pending = 0; 336 337 return; 338} 339 340/* 341 * Data is pending on the DNS socket; check for valid replies 342 * to our queries and dispatch them to waiting clients. 343 */ 344void 345yp_run_dnsq(void) 346{ 347 register struct circleq_dnsentry *q; 348 char buf[sizeof(HEADER) + MAXPACKET]; 349 char retrybuf[MAXHOSTNAMELEN]; 350 struct sockaddr_in sin; 351 socklen_t len; 352 int rval; 353 HEADER *hptr; 354 struct hostent *hent; 355 356 if (debug) 357 yp_error("running dns queue"); 358 359 bzero(buf, sizeof(buf)); 360 361 len = sizeof(struct sockaddr_in); 362 rval = recvfrom(resfd, buf, sizeof(buf), 0, 363 (struct sockaddr *)&sin, &len); 364 365 if (rval == -1) { 366 yp_error("recvfrom failed: %s", strerror(errno)); 367 return; 368 } 369 370 /* 371 * We may have data left in the socket that represents 372 * replies to earlier queries that we don't care about 373 * anymore. If there are no lookups pending or the packet 374 * ID doesn't match any of the queue IDs, just drop it 375 * on the floor. 376 */ 377 hptr = (HEADER *)&buf; 378 if (!pending || 379 (q = yp_find_dnsqent(ntohs(hptr->id), BY_DNS_ID)) == NULL) { 380 /* ignore */ 381 return; 382 } 383 384 if (debug) 385 yp_error("got dns reply from %s", inet_ntoa(sin.sin_addr)); 386 387 hent = __dns_getanswer(buf, rval, q->name, q->type); 388 389 if (hent != NULL) { 390 if (q->type == T_PTR) { 391 hent->h_addr = (char *)q->addr; 392 hent->h_addrtype = q->addrtype; 393 hent->h_length = q->addrlen; 394 } 395 } 396 397 /* Got an answer ready for a client -- send it off. */ 398 yp_send_dns_reply(q, parse(hent)); 399 pending--; 400 TAILQ_REMOVE(&qhead, q, links); 401 free(q->name); 402 free(q); 403 404 /* Decrement TTLs on other entries while we're here. */ 405 yp_prune_dnsq(); 406 407 return; 408} 409 410/* 411 * Queue and transmit an asynchronous DNS hostname lookup. 412 */ 413ypstat 414yp_async_lookup_name(struct svc_req *rqstp, char *name, int af) 415{ 416 register struct circleq_dnsentry *q; 417 socklen_t len; 418 int type; 419 420 /* Check for SOCK_DGRAM or SOCK_STREAM -- we need to know later */ 421 type = -1; 422 len = sizeof(type); 423 if (getsockopt(rqstp->rq_xprt->xp_fd, SOL_SOCKET, 424 SO_TYPE, &type, &len) == -1) { 425 yp_error("getsockopt failed: %s", strerror(errno)); 426 return(YP_YPERR); 427 } 428 429 /* Avoid transmitting dupe requests. */ 430 if (type == SOCK_DGRAM && 431 yp_find_dnsqent(svcudp_get_xid(rqstp->rq_xprt),BY_RPC_XID) != NULL) 432 return(YP_TRUE); 433 434 if ((q = yp_malloc_dnsent()) == NULL) 435 return(YP_YPERR); 436 437 q->type = (af == AF_INET) ? T_A : T_AAAA; 438 q->ttl = DEF_TTL; 439 q->xprt = rqstp->rq_xprt; 440 q->ypvers = rqstp->rq_vers; 441 q->prot_type = type; 442 if (q->prot_type == SOCK_DGRAM) 443 q->xid = svcudp_get_xid(q->xprt); 444 q->client_addr = q->xprt->xp_raddr; 445 q->domain = _res.dnsrch; 446 q->id = yp_send_dns_query(name, q->type); 447 448 if (q->id == 0) { 449 yp_error("DNS query failed"); 450 free(q); 451 return(YP_YPERR); 452 } 453 454 q->name = strdup(name); 455 TAILQ_INSERT_HEAD(&qhead, q, links); 456 pending++; 457 458 if (debug) 459 yp_error("queueing async DNS name lookup (%d)", q->id); 460 461 yp_prune_dnsq(); 462 return(YP_TRUE); 463} 464 465/* 466 * Queue and transmit an asynchronous DNS IP address lookup. 467 */ 468ypstat 469yp_async_lookup_addr(struct svc_req *rqstp, char *addr, int af) 470{ 471 register struct circleq_dnsentry *q; 472 char buf[MAXHOSTNAMELEN], *qp; 473 uint32_t abuf[4]; /* IPv4 or IPv6 */ 474 u_char *uaddr = (u_char *)abuf; 475 socklen_t len; 476 int type, n; 477 478 /* Check for SOCK_DGRAM or SOCK_STREAM -- we need to know later */ 479 type = -1; 480 len = sizeof(type); 481 if (getsockopt(rqstp->rq_xprt->xp_fd, SOL_SOCKET, 482 SO_TYPE, &type, &len) == -1) { 483 yp_error("getsockopt failed: %s", strerror(errno)); 484 return(YP_YPERR); 485 } 486 487 /* Avoid transmitting dupe requests. */ 488 if (type == SOCK_DGRAM && 489 yp_find_dnsqent(svcudp_get_xid(rqstp->rq_xprt),BY_RPC_XID) != NULL) 490 return(YP_TRUE); 491 492 if ((q = yp_malloc_dnsent()) == NULL) 493 return(YP_YPERR); 494 495 switch (af) { 496 case AF_INET: 497 if (inet_aton(addr, (struct in_addr *)uaddr) != 1) 498 return(YP_NOKEY); 499 snprintf(buf, sizeof(buf), "%u.%u.%u.%u.in-addr.arpa", 500 (uaddr[3] & 0xff), (uaddr[2] & 0xff), 501 (uaddr[1] & 0xff), (uaddr[0] & 0xff)); 502 len = INADDRSZ; 503 break; 504 case AF_INET6: 505 if (inet_pton(af, addr, uaddr) != 1) 506 return(YP_NOKEY); 507 qp = buf; 508 for (n = IN6ADDRSZ - 1; n >= 0; n--) { 509 qp += (size_t)sprintf(qp, "%x.%x.", uaddr[n] & 0xf, 510 (uaddr[n] >> 4) & 0xf); 511 } 512 strlcat(buf, "ip6.arpa", sizeof(buf)); 513 len = IN6ADDRSZ; 514 break; 515 default: 516 return(YP_YPERR); 517 } 518 519 if (debug) 520 yp_error("DNS address is: %s", buf); 521 522 q->type = T_PTR; 523 q->ttl = DEF_TTL; 524 q->xprt = rqstp->rq_xprt; 525 q->ypvers = rqstp->rq_vers; 526 q->domain = NULL; 527 q->prot_type = type; 528 if (q->prot_type == SOCK_DGRAM) 529 q->xid = svcudp_get_xid(q->xprt); 530 q->client_addr = q->xprt->xp_raddr; 531 q->id = yp_send_dns_query(buf, q->type); 532 533 if (q->id == 0) { 534 yp_error("DNS query failed"); 535 free(q); 536 return(YP_YPERR); 537 } 538 539 memcpy(q->addr, uaddr, len); 540 q->addrlen = len; 541 q->addrtype = af; 542 q->name = strdup(buf); 543 TAILQ_INSERT_HEAD(&qhead, q, links); 544 pending++; 545 546 if (debug) 547 yp_error("queueing async DNS address lookup (%d)", q->id); 548 549 yp_prune_dnsq(); 550 return(YP_TRUE); 551} 552