1/* 2 * Copyright (C) 2004, 2005, 2007-2009 Internet Systems Consortium, Inc. ("ISC") 3 * Copyright (C) 2000, 2001, 2003 Internet Software Consortium. 4 * 5 * Permission to use, copy, modify, and/or distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11 * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 15 * PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18/* $Id: context.c,v 1.55 2009/09/02 23:48:03 tbox Exp $ */ 19 20/*! \file context.c 21 lwres_context_create() creates a #lwres_context_t structure for use in 22 lightweight resolver operations. It holds a socket and other data 23 needed for communicating with a resolver daemon. The new 24 lwres_context_t is returned through contextp, a pointer to a 25 lwres_context_t pointer. This lwres_context_t pointer must initially 26 be NULL, and is modified to point to the newly created 27 lwres_context_t. 28 29 When the lightweight resolver needs to perform dynamic memory 30 allocation, it will call malloc_function to allocate memory and 31 free_function to free it. If malloc_function and free_function are 32 NULL, memory is allocated using malloc and free. It is not 33 permitted to have a NULL malloc_function and a non-NULL free_function 34 or vice versa. arg is passed as the first parameter to the memory 35 allocation functions. If malloc_function and free_function are NULL, 36 arg is unused and should be passed as NULL. 37 38 Once memory for the structure has been allocated, it is initialized 39 using lwres_conf_init() and returned via *contextp. 40 41 lwres_context_destroy() destroys a #lwres_context_t, closing its 42 socket. contextp is a pointer to a pointer to the context that is to 43 be destroyed. The pointer will be set to NULL when the context has 44 been destroyed. 45 46 The context holds a serial number that is used to identify resolver 47 request packets and associate responses with the corresponding 48 requests. This serial number is controlled using 49 lwres_context_initserial() and lwres_context_nextserial(). 50 lwres_context_initserial() sets the serial number for context *ctx to 51 serial. lwres_context_nextserial() increments the serial number and 52 returns the previous value. 53 54 Memory for a lightweight resolver context is allocated and freed using 55 lwres_context_allocmem() and lwres_context_freemem(). These use 56 whatever allocations were defined when the context was created with 57 lwres_context_create(). lwres_context_allocmem() allocates len bytes 58 of memory and if successful returns a pointer to the allocated 59 storage. lwres_context_freemem() frees len bytes of space starting at 60 location mem. 61 62 lwres_context_sendrecv() performs I/O for the context ctx. Data are 63 read and written from the context's socket. It writes data from 64 sendbase -- typically a lightweight resolver query packet -- and waits 65 for a reply which is copied to the receive buffer at recvbase. The 66 number of bytes that were written to this receive buffer is returned 67 in *recvd_len. 68 69\section context_return Return Values 70 71 lwres_context_create() returns #LWRES_R_NOMEMORY if memory for the 72 struct lwres_context could not be allocated, #LWRES_R_SUCCESS 73 otherwise. 74 75 Successful calls to the memory allocator lwres_context_allocmem() 76 return a pointer to the start of the allocated space. It returns NULL 77 if memory could not be allocated. 78 79 #LWRES_R_SUCCESS is returned when lwres_context_sendrecv() completes 80 successfully. #LWRES_R_IOERROR is returned if an I/O error occurs and 81 #LWRES_R_TIMEOUT is returned if lwres_context_sendrecv() times out 82 waiting for a response. 83 84\section context_see See Also 85 86 lwres_conf_init(), malloc, free. 87 */ 88#include <config.h> 89 90#include <fcntl.h> 91#include <limits.h> 92#include <stdlib.h> 93#include <string.h> 94#include <time.h> 95#include <unistd.h> 96 97#include <lwres/lwres.h> 98#include <lwres/net.h> 99#include <lwres/platform.h> 100 101#ifdef LWRES_PLATFORM_NEEDSYSSELECTH 102#include <sys/select.h> 103#endif 104 105#include "context_p.h" 106#include "assert_p.h" 107 108/*! 109 * Some systems define the socket length argument as an int, some as size_t, 110 * some as socklen_t. The last is what the current POSIX standard mandates. 111 * This definition is here so it can be portable but easily changed if needed. 112 */ 113#ifndef LWRES_SOCKADDR_LEN_T 114#define LWRES_SOCKADDR_LEN_T unsigned int 115#endif 116 117/*! 118 * Make a socket nonblocking. 119 */ 120#ifndef MAKE_NONBLOCKING 121#define MAKE_NONBLOCKING(sd, retval) \ 122do { \ 123 retval = fcntl(sd, F_GETFL, 0); \ 124 if (retval != -1) { \ 125 retval |= O_NONBLOCK; \ 126 retval = fcntl(sd, F_SETFL, retval); \ 127 } \ 128} while (0) 129#endif 130 131LIBLWRES_EXTERNAL_DATA lwres_uint16_t lwres_udp_port = LWRES_UDP_PORT; 132LIBLWRES_EXTERNAL_DATA const char *lwres_resolv_conf = LWRES_RESOLV_CONF; 133 134static void * 135lwres_malloc(void *, size_t); 136 137static void 138lwres_free(void *, void *, size_t); 139 140/*! 141 * lwres_result_t 142 */ 143static lwres_result_t 144context_connect(lwres_context_t *); 145 146/*% 147 * Creates a #lwres_context_t structure for use in 148 * lightweight resolver operations. 149 */ 150lwres_result_t 151lwres_context_create(lwres_context_t **contextp, void *arg, 152 lwres_malloc_t malloc_function, 153 lwres_free_t free_function, 154 unsigned int flags) 155{ 156 lwres_context_t *ctx; 157 158 REQUIRE(contextp != NULL && *contextp == NULL); 159 160 /* 161 * If we were not given anything special to use, use our own 162 * functions. These are just wrappers around malloc() and free(). 163 */ 164 if (malloc_function == NULL || free_function == NULL) { 165 REQUIRE(malloc_function == NULL); 166 REQUIRE(free_function == NULL); 167 malloc_function = lwres_malloc; 168 free_function = lwres_free; 169 } 170 171 ctx = malloc_function(arg, sizeof(lwres_context_t)); 172 if (ctx == NULL) 173 return (LWRES_R_NOMEMORY); 174 175 /* 176 * Set up the context. 177 */ 178 ctx->malloc = malloc_function; 179 ctx->free = free_function; 180 ctx->arg = arg; 181 ctx->sock = -1; 182 183 ctx->timeout = LWRES_DEFAULT_TIMEOUT; 184 ctx->serial = time(NULL); /* XXXMLG or BEW */ 185 186 ctx->use_ipv4 = 1; 187 ctx->use_ipv6 = 1; 188 if ((flags & (LWRES_CONTEXT_USEIPV4 | LWRES_CONTEXT_USEIPV6)) == 189 LWRES_CONTEXT_USEIPV6) { 190 ctx->use_ipv4 = 0; 191 } 192 if ((flags & (LWRES_CONTEXT_USEIPV4 | LWRES_CONTEXT_USEIPV6)) == 193 LWRES_CONTEXT_USEIPV4) { 194 ctx->use_ipv6 = 0; 195 } 196 197 /* 198 * Init resolv.conf bits. 199 */ 200 lwres_conf_init(ctx); 201 202 *contextp = ctx; 203 return (LWRES_R_SUCCESS); 204} 205 206/*% 207Destroys a #lwres_context_t, closing its socket. 208contextp is a pointer to a pointer to the context that is 209to be destroyed. The pointer will be set to NULL 210when the context has been destroyed. 211 */ 212void 213lwres_context_destroy(lwres_context_t **contextp) { 214 lwres_context_t *ctx; 215 216 REQUIRE(contextp != NULL && *contextp != NULL); 217 218 ctx = *contextp; 219 *contextp = NULL; 220 221 if (ctx->sock != -1) { 222#ifdef WIN32 223 DestroySockets(); 224#endif 225 (void)close(ctx->sock); 226 ctx->sock = -1; 227 } 228 229 CTXFREE(ctx, sizeof(lwres_context_t)); 230} 231/*% Increments the serial number and returns the previous value. */ 232lwres_uint32_t 233lwres_context_nextserial(lwres_context_t *ctx) { 234 REQUIRE(ctx != NULL); 235 236 return (ctx->serial++); 237} 238 239/*% Sets the serial number for context *ctx to serial. */ 240void 241lwres_context_initserial(lwres_context_t *ctx, lwres_uint32_t serial) { 242 REQUIRE(ctx != NULL); 243 244 ctx->serial = serial; 245} 246 247/*% Frees len bytes of space starting at location mem. */ 248void 249lwres_context_freemem(lwres_context_t *ctx, void *mem, size_t len) { 250 REQUIRE(mem != NULL); 251 REQUIRE(len != 0U); 252 253 CTXFREE(mem, len); 254} 255 256/*% Allocates len bytes of memory and if successful returns a pointer to the allocated storage. */ 257void * 258lwres_context_allocmem(lwres_context_t *ctx, size_t len) { 259 REQUIRE(len != 0U); 260 261 return (CTXMALLOC(len)); 262} 263 264static void * 265lwres_malloc(void *arg, size_t len) { 266 void *mem; 267 268 UNUSED(arg); 269 270 mem = malloc(len); 271 if (mem == NULL) 272 return (NULL); 273 274 memset(mem, 0xe5, len); 275 276 return (mem); 277} 278 279static void 280lwres_free(void *arg, void *mem, size_t len) { 281 UNUSED(arg); 282 283 memset(mem, 0xa9, len); 284 free(mem); 285} 286 287static lwres_result_t 288context_connect(lwres_context_t *ctx) { 289 int s; 290 int ret; 291 struct sockaddr_in sin; 292 struct sockaddr_in6 sin6; 293 struct sockaddr *sa; 294 LWRES_SOCKADDR_LEN_T salen; 295 int domain; 296 297 if (ctx->confdata.lwnext != 0) { 298 memcpy(&ctx->address, &ctx->confdata.lwservers[0], 299 sizeof(lwres_addr_t)); 300 LWRES_LINK_INIT(&ctx->address, link); 301 } else { 302 /* The default is the IPv4 loopback address 127.0.0.1. */ 303 memset(&ctx->address, 0, sizeof(ctx->address)); 304 ctx->address.family = LWRES_ADDRTYPE_V4; 305 ctx->address.length = 4; 306 ctx->address.address[0] = 127; 307 ctx->address.address[1] = 0; 308 ctx->address.address[2] = 0; 309 ctx->address.address[3] = 1; 310 } 311 312 if (ctx->address.family == LWRES_ADDRTYPE_V4) { 313 memcpy(&sin.sin_addr, ctx->address.address, 314 sizeof(sin.sin_addr)); 315 sin.sin_port = htons(lwres_udp_port); 316 sin.sin_family = AF_INET; 317 sa = (struct sockaddr *)&sin; 318 salen = sizeof(sin); 319 domain = PF_INET; 320 } else if (ctx->address.family == LWRES_ADDRTYPE_V6) { 321 memcpy(&sin6.sin6_addr, ctx->address.address, 322 sizeof(sin6.sin6_addr)); 323 sin6.sin6_port = htons(lwres_udp_port); 324 sin6.sin6_family = AF_INET6; 325 sa = (struct sockaddr *)&sin6; 326 salen = sizeof(sin6); 327 domain = PF_INET6; 328 } else 329 return (LWRES_R_IOERROR); 330 331#ifdef WIN32 332 InitSockets(); 333#endif 334 s = socket(domain, SOCK_DGRAM, IPPROTO_UDP); 335 if (s < 0) { 336#ifdef WIN32 337 DestroySockets(); 338#endif 339 return (LWRES_R_IOERROR); 340 } 341 342 ret = connect(s, sa, salen); 343 if (ret != 0) { 344#ifdef WIN32 345 DestroySockets(); 346#endif 347 (void)close(s); 348 return (LWRES_R_IOERROR); 349 } 350 351 MAKE_NONBLOCKING(s, ret); 352 if (ret < 0) { 353#ifdef WIN32 354 DestroySockets(); 355#endif 356 (void)close(s); 357 return (LWRES_R_IOERROR); 358 } 359 360 ctx->sock = s; 361 362 return (LWRES_R_SUCCESS); 363} 364 365int 366lwres_context_getsocket(lwres_context_t *ctx) { 367 return (ctx->sock); 368} 369 370lwres_result_t 371lwres_context_send(lwres_context_t *ctx, 372 void *sendbase, int sendlen) { 373 int ret; 374 lwres_result_t lwresult; 375 376 if (ctx->sock == -1) { 377 lwresult = context_connect(ctx); 378 if (lwresult != LWRES_R_SUCCESS) 379 return (lwresult); 380 } 381 382 ret = sendto(ctx->sock, sendbase, sendlen, 0, NULL, 0); 383 if (ret < 0) 384 return (LWRES_R_IOERROR); 385 if (ret != sendlen) 386 return (LWRES_R_IOERROR); 387 388 return (LWRES_R_SUCCESS); 389} 390 391lwres_result_t 392lwres_context_recv(lwres_context_t *ctx, 393 void *recvbase, int recvlen, 394 int *recvd_len) 395{ 396 LWRES_SOCKADDR_LEN_T fromlen; 397 struct sockaddr_in sin; 398 struct sockaddr_in6 sin6; 399 struct sockaddr *sa; 400 int ret; 401 402 if (ctx->address.family == LWRES_ADDRTYPE_V4) { 403 sa = (struct sockaddr *)&sin; 404 fromlen = sizeof(sin); 405 } else { 406 sa = (struct sockaddr *)&sin6; 407 fromlen = sizeof(sin6); 408 } 409 410 /* 411 * The address of fromlen is cast to void * to shut up compiler 412 * warnings, namely on systems that have the sixth parameter 413 * prototyped as a signed int when LWRES_SOCKADDR_LEN_T is 414 * defined as unsigned. 415 */ 416 ret = recvfrom(ctx->sock, recvbase, recvlen, 0, sa, (void *)&fromlen); 417 418 if (ret < 0) 419 return (LWRES_R_IOERROR); 420 421 if (ret == recvlen) 422 return (LWRES_R_TOOLARGE); 423 424 /* 425 * If we got something other than what we expect, have the caller 426 * wait for another packet. This can happen if an old result 427 * comes in, or if someone is sending us random stuff. 428 */ 429 if (ctx->address.family == LWRES_ADDRTYPE_V4) { 430 if (fromlen != sizeof(sin) 431 || memcmp(&sin.sin_addr, ctx->address.address, 432 sizeof(sin.sin_addr)) != 0 433 || sin.sin_port != htons(lwres_udp_port)) 434 return (LWRES_R_RETRY); 435 } else { 436 if (fromlen != sizeof(sin6) 437 || memcmp(&sin6.sin6_addr, ctx->address.address, 438 sizeof(sin6.sin6_addr)) != 0 439 || sin6.sin6_port != htons(lwres_udp_port)) 440 return (LWRES_R_RETRY); 441 } 442 443 if (recvd_len != NULL) 444 *recvd_len = ret; 445 446 return (LWRES_R_SUCCESS); 447} 448 449/*% performs I/O for the context ctx. */ 450lwres_result_t 451lwres_context_sendrecv(lwres_context_t *ctx, 452 void *sendbase, int sendlen, 453 void *recvbase, int recvlen, 454 int *recvd_len) 455{ 456 lwres_result_t result; 457 int ret2; 458 fd_set readfds; 459 struct timeval timeout; 460 461 /* 462 * Type of tv_sec is 32 bits long. 463 */ 464 if (ctx->timeout <= 0x7FFFFFFFU) 465 timeout.tv_sec = (int)ctx->timeout; 466 else 467 timeout.tv_sec = 0x7FFFFFFF; 468 469 timeout.tv_usec = 0; 470 471 result = lwres_context_send(ctx, sendbase, sendlen); 472 if (result != LWRES_R_SUCCESS) 473 return (result); 474 475 /* 476 * If this is not checked, select() can overflow, 477 * causing corruption elsewhere. 478 */ 479 if (ctx->sock >= (int)FD_SETSIZE) { 480 close(ctx->sock); 481 ctx->sock = -1; 482 return (LWRES_R_IOERROR); 483 } 484 485 again: 486 FD_ZERO(&readfds); 487 FD_SET(ctx->sock, &readfds); 488 ret2 = select(ctx->sock + 1, &readfds, NULL, NULL, &timeout); 489 490 /* 491 * What happened with select? 492 */ 493 if (ret2 < 0) 494 return (LWRES_R_IOERROR); 495 if (ret2 == 0) 496 return (LWRES_R_TIMEOUT); 497 498 result = lwres_context_recv(ctx, recvbase, recvlen, recvd_len); 499 if (result == LWRES_R_RETRY) 500 goto again; 501 502 return (result); 503} 504