res_cache.c revision 92425f097dc28e9518f5608bff2fce16f9b4f0ef
1/* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 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 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include "resolv_cache.h" 30#include <resolv.h> 31#include <stdlib.h> 32#include <string.h> 33#include <time.h> 34#include "pthread.h" 35 36#include <errno.h> 37#include "arpa_nameser.h" 38#include <sys/system_properties.h> 39#include <net/if.h> 40#include <netdb.h> 41#include <linux/if.h> 42 43#include <arpa/inet.h> 44#include "resolv_private.h" 45 46/* This code implements a small and *simple* DNS resolver cache. 47 * 48 * It is only used to cache DNS answers for a time defined by the smallest TTL 49 * among the answer records in order to reduce DNS traffic. It is not supposed 50 * to be a full DNS cache, since we plan to implement that in the future in a 51 * dedicated process running on the system. 52 * 53 * Note that its design is kept simple very intentionally, i.e.: 54 * 55 * - it takes raw DNS query packet data as input, and returns raw DNS 56 * answer packet data as output 57 * 58 * (this means that two similar queries that encode the DNS name 59 * differently will be treated distinctly). 60 * 61 * the smallest TTL value among the answer records are used as the time 62 * to keep an answer in the cache. 63 * 64 * this is bad, but we absolutely want to avoid parsing the answer packets 65 * (and should be solved by the later full DNS cache process). 66 * 67 * - the implementation is just a (query-data) => (answer-data) hash table 68 * with a trivial least-recently-used expiration policy. 69 * 70 * Doing this keeps the code simple and avoids to deal with a lot of things 71 * that a full DNS cache is expected to do. 72 * 73 * The API is also very simple: 74 * 75 * - the client calls _resolv_cache_get() to obtain a handle to the cache. 76 * this will initialize the cache on first usage. the result can be NULL 77 * if the cache is disabled. 78 * 79 * - the client calls _resolv_cache_lookup() before performing a query 80 * 81 * if the function returns RESOLV_CACHE_FOUND, a copy of the answer data 82 * has been copied into the client-provided answer buffer. 83 * 84 * if the function returns RESOLV_CACHE_NOTFOUND, the client should perform 85 * a request normally, *then* call _resolv_cache_add() to add the received 86 * answer to the cache. 87 * 88 * if the function returns RESOLV_CACHE_UNSUPPORTED, the client should 89 * perform a request normally, and *not* call _resolv_cache_add() 90 * 91 * note that RESOLV_CACHE_UNSUPPORTED is also returned if the answer buffer 92 * is too short to accomodate the cached result. 93 * 94 * - when network settings change, the cache must be flushed since the list 95 * of DNS servers probably changed. this is done by calling 96 * _resolv_cache_reset() 97 * 98 * the parameter to this function must be an ever-increasing generation 99 * number corresponding to the current network settings state. 100 * 101 * This is done because several threads could detect the same network 102 * settings change (but at different times) and will all end up calling the 103 * same function. Comparing with the last used generation number ensures 104 * that the cache is only flushed once per network change. 105 */ 106 107/* the name of an environment variable that will be checked the first time 108 * this code is called if its value is "0", then the resolver cache is 109 * disabled. 110 */ 111#define CONFIG_ENV "BIONIC_DNSCACHE" 112 113/* entries older than CONFIG_SECONDS seconds are always discarded. 114 */ 115#define CONFIG_SECONDS (60*10) /* 10 minutes */ 116 117/* default number of entries kept in the cache. This value has been 118 * determined by browsing through various sites and counting the number 119 * of corresponding requests. Keep in mind that our framework is currently 120 * performing two requests per name lookup (one for IPv4, the other for IPv6) 121 * 122 * www.google.com 4 123 * www.ysearch.com 6 124 * www.amazon.com 8 125 * www.nytimes.com 22 126 * www.espn.com 28 127 * www.msn.com 28 128 * www.lemonde.fr 35 129 * 130 * (determined in 2009-2-17 from Paris, France, results may vary depending 131 * on location) 132 * 133 * most high-level websites use lots of media/ad servers with different names 134 * but these are generally reused when browsing through the site. 135 * 136 * As such, a value of 64 should be relatively comfortable at the moment. 137 * 138 * The system property ro.net.dns_cache_size can be used to override the default 139 * value with a custom value 140 */ 141#define CONFIG_MAX_ENTRIES 64 142 143/* name of the system property that can be used to set the cache size */ 144#define DNS_CACHE_SIZE_PROP_NAME "ro.net.dns_cache_size" 145 146/****************************************************************************/ 147/****************************************************************************/ 148/***** *****/ 149/***** *****/ 150/***** *****/ 151/****************************************************************************/ 152/****************************************************************************/ 153 154/* set to 1 to debug cache operations */ 155#define DEBUG 0 156 157/* set to 1 to debug query data */ 158#define DEBUG_DATA 0 159 160#undef XLOG 161#if DEBUG 162# include <logd.h> 163# define XLOG(...) \ 164 __libc_android_log_print(ANDROID_LOG_DEBUG,"libc",__VA_ARGS__) 165 166#include <stdio.h> 167#include <stdarg.h> 168 169/** BOUNDED BUFFER FORMATTING 170 **/ 171 172/* technical note: 173 * 174 * the following debugging routines are used to append data to a bounded 175 * buffer they take two parameters that are: 176 * 177 * - p : a pointer to the current cursor position in the buffer 178 * this value is initially set to the buffer's address. 179 * 180 * - end : the address of the buffer's limit, i.e. of the first byte 181 * after the buffer. this address should never be touched. 182 * 183 * IMPORTANT: it is assumed that end > buffer_address, i.e. 184 * that the buffer is at least one byte. 185 * 186 * the _bprint_() functions return the new value of 'p' after the data 187 * has been appended, and also ensure the following: 188 * 189 * - the returned value will never be strictly greater than 'end' 190 * 191 * - a return value equal to 'end' means that truncation occured 192 * (in which case, end[-1] will be set to 0) 193 * 194 * - after returning from a _bprint_() function, the content of the buffer 195 * is always 0-terminated, even in the event of truncation. 196 * 197 * these conventions allow you to call _bprint_ functions multiple times and 198 * only check for truncation at the end of the sequence, as in: 199 * 200 * char buff[1000], *p = buff, *end = p + sizeof(buff); 201 * 202 * p = _bprint_c(p, end, '"'); 203 * p = _bprint_s(p, end, my_string); 204 * p = _bprint_c(p, end, '"'); 205 * 206 * if (p >= end) { 207 * // buffer was too small 208 * } 209 * 210 * printf( "%s", buff ); 211 */ 212 213/* add a char to a bounded buffer */ 214static char* 215_bprint_c( char* p, char* end, int c ) 216{ 217 if (p < end) { 218 if (p+1 == end) 219 *p++ = 0; 220 else { 221 *p++ = (char) c; 222 *p = 0; 223 } 224 } 225 return p; 226} 227 228/* add a sequence of bytes to a bounded buffer */ 229static char* 230_bprint_b( char* p, char* end, const char* buf, int len ) 231{ 232 int avail = end - p; 233 234 if (avail <= 0 || len <= 0) 235 return p; 236 237 if (avail > len) 238 avail = len; 239 240 memcpy( p, buf, avail ); 241 p += avail; 242 243 if (p < end) 244 p[0] = 0; 245 else 246 end[-1] = 0; 247 248 return p; 249} 250 251/* add a string to a bounded buffer */ 252static char* 253_bprint_s( char* p, char* end, const char* str ) 254{ 255 return _bprint_b(p, end, str, strlen(str)); 256} 257 258/* add a formatted string to a bounded buffer */ 259static char* 260_bprint( char* p, char* end, const char* format, ... ) 261{ 262 int avail, n; 263 va_list args; 264 265 avail = end - p; 266 267 if (avail <= 0) 268 return p; 269 270 va_start(args, format); 271 n = vsnprintf( p, avail, format, args); 272 va_end(args); 273 274 /* certain C libraries return -1 in case of truncation */ 275 if (n < 0 || n > avail) 276 n = avail; 277 278 p += n; 279 /* certain C libraries do not zero-terminate in case of truncation */ 280 if (p == end) 281 p[-1] = 0; 282 283 return p; 284} 285 286/* add a hex value to a bounded buffer, up to 8 digits */ 287static char* 288_bprint_hex( char* p, char* end, unsigned value, int numDigits ) 289{ 290 char text[sizeof(unsigned)*2]; 291 int nn = 0; 292 293 while (numDigits-- > 0) { 294 text[nn++] = "0123456789abcdef"[(value >> (numDigits*4)) & 15]; 295 } 296 return _bprint_b(p, end, text, nn); 297} 298 299/* add the hexadecimal dump of some memory area to a bounded buffer */ 300static char* 301_bprint_hexdump( char* p, char* end, const uint8_t* data, int datalen ) 302{ 303 int lineSize = 16; 304 305 while (datalen > 0) { 306 int avail = datalen; 307 int nn; 308 309 if (avail > lineSize) 310 avail = lineSize; 311 312 for (nn = 0; nn < avail; nn++) { 313 if (nn > 0) 314 p = _bprint_c(p, end, ' '); 315 p = _bprint_hex(p, end, data[nn], 2); 316 } 317 for ( ; nn < lineSize; nn++ ) { 318 p = _bprint_s(p, end, " "); 319 } 320 p = _bprint_s(p, end, " "); 321 322 for (nn = 0; nn < avail; nn++) { 323 int c = data[nn]; 324 325 if (c < 32 || c > 127) 326 c = '.'; 327 328 p = _bprint_c(p, end, c); 329 } 330 p = _bprint_c(p, end, '\n'); 331 332 data += avail; 333 datalen -= avail; 334 } 335 return p; 336} 337 338/* dump the content of a query of packet to the log */ 339static void 340XLOG_BYTES( const void* base, int len ) 341{ 342 char buff[1024]; 343 char* p = buff, *end = p + sizeof(buff); 344 345 p = _bprint_hexdump(p, end, base, len); 346 XLOG("%s",buff); 347} 348 349#else /* !DEBUG */ 350# define XLOG(...) ((void)0) 351# define XLOG_BYTES(a,b) ((void)0) 352#endif 353 354static time_t 355_time_now( void ) 356{ 357 struct timeval tv; 358 359 gettimeofday( &tv, NULL ); 360 return tv.tv_sec; 361} 362 363/* reminder: the general format of a DNS packet is the following: 364 * 365 * HEADER (12 bytes) 366 * QUESTION (variable) 367 * ANSWER (variable) 368 * AUTHORITY (variable) 369 * ADDITIONNAL (variable) 370 * 371 * the HEADER is made of: 372 * 373 * ID : 16 : 16-bit unique query identification field 374 * 375 * QR : 1 : set to 0 for queries, and 1 for responses 376 * Opcode : 4 : set to 0 for queries 377 * AA : 1 : set to 0 for queries 378 * TC : 1 : truncation flag, will be set to 0 in queries 379 * RD : 1 : recursion desired 380 * 381 * RA : 1 : recursion available (0 in queries) 382 * Z : 3 : three reserved zero bits 383 * RCODE : 4 : response code (always 0=NOERROR in queries) 384 * 385 * QDCount: 16 : question count 386 * ANCount: 16 : Answer count (0 in queries) 387 * NSCount: 16: Authority Record count (0 in queries) 388 * ARCount: 16: Additionnal Record count (0 in queries) 389 * 390 * the QUESTION is made of QDCount Question Record (QRs) 391 * the ANSWER is made of ANCount RRs 392 * the AUTHORITY is made of NSCount RRs 393 * the ADDITIONNAL is made of ARCount RRs 394 * 395 * Each Question Record (QR) is made of: 396 * 397 * QNAME : variable : Query DNS NAME 398 * TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255) 399 * CLASS : 16 : class of query (IN=1) 400 * 401 * Each Resource Record (RR) is made of: 402 * 403 * NAME : variable : DNS NAME 404 * TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255) 405 * CLASS : 16 : class of query (IN=1) 406 * TTL : 32 : seconds to cache this RR (0=none) 407 * RDLENGTH: 16 : size of RDDATA in bytes 408 * RDDATA : variable : RR data (depends on TYPE) 409 * 410 * Each QNAME contains a domain name encoded as a sequence of 'labels' 411 * terminated by a zero. Each label has the following format: 412 * 413 * LEN : 8 : lenght of label (MUST be < 64) 414 * NAME : 8*LEN : label length (must exclude dots) 415 * 416 * A value of 0 in the encoding is interpreted as the 'root' domain and 417 * terminates the encoding. So 'www.android.com' will be encoded as: 418 * 419 * <3>www<7>android<3>com<0> 420 * 421 * Where <n> represents the byte with value 'n' 422 * 423 * Each NAME reflects the QNAME of the question, but has a slightly more 424 * complex encoding in order to provide message compression. This is achieved 425 * by using a 2-byte pointer, with format: 426 * 427 * TYPE : 2 : 0b11 to indicate a pointer, 0b01 and 0b10 are reserved 428 * OFFSET : 14 : offset to another part of the DNS packet 429 * 430 * The offset is relative to the start of the DNS packet and must point 431 * A pointer terminates the encoding. 432 * 433 * The NAME can be encoded in one of the following formats: 434 * 435 * - a sequence of simple labels terminated by 0 (like QNAMEs) 436 * - a single pointer 437 * - a sequence of simple labels terminated by a pointer 438 * 439 * A pointer shall always point to either a pointer of a sequence of 440 * labels (which can themselves be terminated by either a 0 or a pointer) 441 * 442 * The expanded length of a given domain name should not exceed 255 bytes. 443 * 444 * NOTE: we don't parse the answer packets, so don't need to deal with NAME 445 * records, only QNAMEs. 446 */ 447 448#define DNS_HEADER_SIZE 12 449 450#define DNS_TYPE_A "\00\01" /* big-endian decimal 1 */ 451#define DNS_TYPE_PTR "\00\014" /* big-endian decimal 12 */ 452#define DNS_TYPE_MX "\00\017" /* big-endian decimal 15 */ 453#define DNS_TYPE_AAAA "\00\034" /* big-endian decimal 28 */ 454#define DNS_TYPE_ALL "\00\0377" /* big-endian decimal 255 */ 455 456#define DNS_CLASS_IN "\00\01" /* big-endian decimal 1 */ 457 458typedef struct { 459 const uint8_t* base; 460 const uint8_t* end; 461 const uint8_t* cursor; 462} DnsPacket; 463 464static void 465_dnsPacket_init( DnsPacket* packet, const uint8_t* buff, int bufflen ) 466{ 467 packet->base = buff; 468 packet->end = buff + bufflen; 469 packet->cursor = buff; 470} 471 472static void 473_dnsPacket_rewind( DnsPacket* packet ) 474{ 475 packet->cursor = packet->base; 476} 477 478static void 479_dnsPacket_skip( DnsPacket* packet, int count ) 480{ 481 const uint8_t* p = packet->cursor + count; 482 483 if (p > packet->end) 484 p = packet->end; 485 486 packet->cursor = p; 487} 488 489static int 490_dnsPacket_readInt16( DnsPacket* packet ) 491{ 492 const uint8_t* p = packet->cursor; 493 494 if (p+2 > packet->end) 495 return -1; 496 497 packet->cursor = p+2; 498 return (p[0]<< 8) | p[1]; 499} 500 501/** QUERY CHECKING 502 **/ 503 504/* check bytes in a dns packet. returns 1 on success, 0 on failure. 505 * the cursor is only advanced in the case of success 506 */ 507static int 508_dnsPacket_checkBytes( DnsPacket* packet, int numBytes, const void* bytes ) 509{ 510 const uint8_t* p = packet->cursor; 511 512 if (p + numBytes > packet->end) 513 return 0; 514 515 if (memcmp(p, bytes, numBytes) != 0) 516 return 0; 517 518 packet->cursor = p + numBytes; 519 return 1; 520} 521 522/* parse and skip a given QNAME stored in a query packet, 523 * from the current cursor position. returns 1 on success, 524 * or 0 for malformed data. 525 */ 526static int 527_dnsPacket_checkQName( DnsPacket* packet ) 528{ 529 const uint8_t* p = packet->cursor; 530 const uint8_t* end = packet->end; 531 532 for (;;) { 533 int c; 534 535 if (p >= end) 536 break; 537 538 c = *p++; 539 540 if (c == 0) { 541 packet->cursor = p; 542 return 1; 543 } 544 545 /* we don't expect label compression in QNAMEs */ 546 if (c >= 64) 547 break; 548 549 p += c; 550 /* we rely on the bound check at the start 551 * of the loop here */ 552 } 553 /* malformed data */ 554 XLOG("malformed QNAME"); 555 return 0; 556} 557 558/* parse and skip a given QR stored in a packet. 559 * returns 1 on success, and 0 on failure 560 */ 561static int 562_dnsPacket_checkQR( DnsPacket* packet ) 563{ 564 int len; 565 566 if (!_dnsPacket_checkQName(packet)) 567 return 0; 568 569 /* TYPE must be one of the things we support */ 570 if (!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_A) && 571 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_PTR) && 572 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_MX) && 573 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_AAAA) && 574 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_ALL)) 575 { 576 XLOG("unsupported TYPE"); 577 return 0; 578 } 579 /* CLASS must be IN */ 580 if (!_dnsPacket_checkBytes(packet, 2, DNS_CLASS_IN)) { 581 XLOG("unsupported CLASS"); 582 return 0; 583 } 584 585 return 1; 586} 587 588/* check the header of a DNS Query packet, return 1 if it is one 589 * type of query we can cache, or 0 otherwise 590 */ 591static int 592_dnsPacket_checkQuery( DnsPacket* packet ) 593{ 594 const uint8_t* p = packet->base; 595 int qdCount, anCount, dnCount, arCount; 596 597 if (p + DNS_HEADER_SIZE > packet->end) { 598 XLOG("query packet too small"); 599 return 0; 600 } 601 602 /* QR must be set to 0, opcode must be 0 and AA must be 0 */ 603 /* RA, Z, and RCODE must be 0 */ 604 if ((p[2] & 0xFC) != 0 || p[3] != 0) { 605 XLOG("query packet flags unsupported"); 606 return 0; 607 } 608 609 /* Note that we ignore the TC and RD bits here for the 610 * following reasons: 611 * 612 * - there is no point for a query packet sent to a server 613 * to have the TC bit set, but the implementation might 614 * set the bit in the query buffer for its own needs 615 * between a _resolv_cache_lookup and a 616 * _resolv_cache_add. We should not freak out if this 617 * is the case. 618 * 619 * - we consider that the result from a RD=0 or a RD=1 620 * query might be different, hence that the RD bit 621 * should be used to differentiate cached result. 622 * 623 * this implies that RD is checked when hashing or 624 * comparing query packets, but not TC 625 */ 626 627 /* ANCOUNT, DNCOUNT and ARCOUNT must be 0 */ 628 qdCount = (p[4] << 8) | p[5]; 629 anCount = (p[6] << 8) | p[7]; 630 dnCount = (p[8] << 8) | p[9]; 631 arCount = (p[10]<< 8) | p[11]; 632 633 if (anCount != 0 || dnCount != 0 || arCount != 0) { 634 XLOG("query packet contains non-query records"); 635 return 0; 636 } 637 638 if (qdCount == 0) { 639 XLOG("query packet doesn't contain query record"); 640 return 0; 641 } 642 643 /* Check QDCOUNT QRs */ 644 packet->cursor = p + DNS_HEADER_SIZE; 645 646 for (;qdCount > 0; qdCount--) 647 if (!_dnsPacket_checkQR(packet)) 648 return 0; 649 650 return 1; 651} 652 653/** QUERY DEBUGGING 654 **/ 655#if DEBUG 656static char* 657_dnsPacket_bprintQName(DnsPacket* packet, char* bp, char* bend) 658{ 659 const uint8_t* p = packet->cursor; 660 const uint8_t* end = packet->end; 661 int first = 1; 662 663 for (;;) { 664 int c; 665 666 if (p >= end) 667 break; 668 669 c = *p++; 670 671 if (c == 0) { 672 packet->cursor = p; 673 return bp; 674 } 675 676 /* we don't expect label compression in QNAMEs */ 677 if (c >= 64) 678 break; 679 680 if (first) 681 first = 0; 682 else 683 bp = _bprint_c(bp, bend, '.'); 684 685 bp = _bprint_b(bp, bend, (const char*)p, c); 686 687 p += c; 688 /* we rely on the bound check at the start 689 * of the loop here */ 690 } 691 /* malformed data */ 692 bp = _bprint_s(bp, bend, "<MALFORMED>"); 693 return bp; 694} 695 696static char* 697_dnsPacket_bprintQR(DnsPacket* packet, char* p, char* end) 698{ 699#define QQ(x) { DNS_TYPE_##x, #x } 700 static const struct { 701 const char* typeBytes; 702 const char* typeString; 703 } qTypes[] = 704 { 705 QQ(A), QQ(PTR), QQ(MX), QQ(AAAA), QQ(ALL), 706 { NULL, NULL } 707 }; 708 int nn; 709 const char* typeString = NULL; 710 711 /* dump QNAME */ 712 p = _dnsPacket_bprintQName(packet, p, end); 713 714 /* dump TYPE */ 715 p = _bprint_s(p, end, " ("); 716 717 for (nn = 0; qTypes[nn].typeBytes != NULL; nn++) { 718 if (_dnsPacket_checkBytes(packet, 2, qTypes[nn].typeBytes)) { 719 typeString = qTypes[nn].typeString; 720 break; 721 } 722 } 723 724 if (typeString != NULL) 725 p = _bprint_s(p, end, typeString); 726 else { 727 int typeCode = _dnsPacket_readInt16(packet); 728 p = _bprint(p, end, "UNKNOWN-%d", typeCode); 729 } 730 731 p = _bprint_c(p, end, ')'); 732 733 /* skip CLASS */ 734 _dnsPacket_skip(packet, 2); 735 return p; 736} 737 738/* this function assumes the packet has already been checked */ 739static char* 740_dnsPacket_bprintQuery( DnsPacket* packet, char* p, char* end ) 741{ 742 int qdCount; 743 744 if (packet->base[2] & 0x1) { 745 p = _bprint_s(p, end, "RECURSIVE "); 746 } 747 748 _dnsPacket_skip(packet, 4); 749 qdCount = _dnsPacket_readInt16(packet); 750 _dnsPacket_skip(packet, 6); 751 752 for ( ; qdCount > 0; qdCount-- ) { 753 p = _dnsPacket_bprintQR(packet, p, end); 754 } 755 return p; 756} 757#endif 758 759 760/** QUERY HASHING SUPPORT 761 ** 762 ** THE FOLLOWING CODE ASSUMES THAT THE INPUT PACKET HAS ALREADY 763 ** BEEN SUCCESFULLY CHECKED. 764 **/ 765 766/* use 32-bit FNV hash function */ 767#define FNV_MULT 16777619U 768#define FNV_BASIS 2166136261U 769 770static unsigned 771_dnsPacket_hashBytes( DnsPacket* packet, int numBytes, unsigned hash ) 772{ 773 const uint8_t* p = packet->cursor; 774 const uint8_t* end = packet->end; 775 776 while (numBytes > 0 && p < end) { 777 hash = hash*FNV_MULT ^ *p++; 778 } 779 packet->cursor = p; 780 return hash; 781} 782 783 784static unsigned 785_dnsPacket_hashQName( DnsPacket* packet, unsigned hash ) 786{ 787 const uint8_t* p = packet->cursor; 788 const uint8_t* end = packet->end; 789 790 for (;;) { 791 int c; 792 793 if (p >= end) { /* should not happen */ 794 XLOG("%s: INTERNAL_ERROR: read-overflow !!\n", __FUNCTION__); 795 break; 796 } 797 798 c = *p++; 799 800 if (c == 0) 801 break; 802 803 if (c >= 64) { 804 XLOG("%s: INTERNAL_ERROR: malformed domain !!\n", __FUNCTION__); 805 break; 806 } 807 if (p + c >= end) { 808 XLOG("%s: INTERNAL_ERROR: simple label read-overflow !!\n", 809 __FUNCTION__); 810 break; 811 } 812 while (c > 0) { 813 hash = hash*FNV_MULT ^ *p++; 814 c -= 1; 815 } 816 } 817 packet->cursor = p; 818 return hash; 819} 820 821static unsigned 822_dnsPacket_hashQR( DnsPacket* packet, unsigned hash ) 823{ 824 int len; 825 826 hash = _dnsPacket_hashQName(packet, hash); 827 hash = _dnsPacket_hashBytes(packet, 4, hash); /* TYPE and CLASS */ 828 return hash; 829} 830 831static unsigned 832_dnsPacket_hashQuery( DnsPacket* packet ) 833{ 834 unsigned hash = FNV_BASIS; 835 int count; 836 _dnsPacket_rewind(packet); 837 838 /* we ignore the TC bit for reasons explained in 839 * _dnsPacket_checkQuery(). 840 * 841 * however we hash the RD bit to differentiate 842 * between answers for recursive and non-recursive 843 * queries. 844 */ 845 hash = hash*FNV_MULT ^ (packet->base[2] & 1); 846 847 /* assume: other flags are 0 */ 848 _dnsPacket_skip(packet, 4); 849 850 /* read QDCOUNT */ 851 count = _dnsPacket_readInt16(packet); 852 853 /* assume: ANcount, NScount, ARcount are 0 */ 854 _dnsPacket_skip(packet, 6); 855 856 /* hash QDCOUNT QRs */ 857 for ( ; count > 0; count-- ) 858 hash = _dnsPacket_hashQR(packet, hash); 859 860 return hash; 861} 862 863 864/** QUERY COMPARISON 865 ** 866 ** THE FOLLOWING CODE ASSUMES THAT THE INPUT PACKETS HAVE ALREADY 867 ** BEEN SUCCESFULLY CHECKED. 868 **/ 869 870static int 871_dnsPacket_isEqualDomainName( DnsPacket* pack1, DnsPacket* pack2 ) 872{ 873 const uint8_t* p1 = pack1->cursor; 874 const uint8_t* end1 = pack1->end; 875 const uint8_t* p2 = pack2->cursor; 876 const uint8_t* end2 = pack2->end; 877 878 for (;;) { 879 int c1, c2; 880 881 if (p1 >= end1 || p2 >= end2) { 882 XLOG("%s: INTERNAL_ERROR: read-overflow !!\n", __FUNCTION__); 883 break; 884 } 885 c1 = *p1++; 886 c2 = *p2++; 887 if (c1 != c2) 888 break; 889 890 if (c1 == 0) { 891 pack1->cursor = p1; 892 pack2->cursor = p2; 893 return 1; 894 } 895 if (c1 >= 64) { 896 XLOG("%s: INTERNAL_ERROR: malformed domain !!\n", __FUNCTION__); 897 break; 898 } 899 if ((p1+c1 > end1) || (p2+c1 > end2)) { 900 XLOG("%s: INTERNAL_ERROR: simple label read-overflow !!\n", 901 __FUNCTION__); 902 break; 903 } 904 if (memcmp(p1, p2, c1) != 0) 905 break; 906 p1 += c1; 907 p2 += c1; 908 /* we rely on the bound checks at the start of the loop */ 909 } 910 /* not the same, or one is malformed */ 911 XLOG("different DN"); 912 return 0; 913} 914 915static int 916_dnsPacket_isEqualBytes( DnsPacket* pack1, DnsPacket* pack2, int numBytes ) 917{ 918 const uint8_t* p1 = pack1->cursor; 919 const uint8_t* p2 = pack2->cursor; 920 921 if ( p1 + numBytes > pack1->end || p2 + numBytes > pack2->end ) 922 return 0; 923 924 if ( memcmp(p1, p2, numBytes) != 0 ) 925 return 0; 926 927 pack1->cursor += numBytes; 928 pack2->cursor += numBytes; 929 return 1; 930} 931 932static int 933_dnsPacket_isEqualQR( DnsPacket* pack1, DnsPacket* pack2 ) 934{ 935 /* compare domain name encoding + TYPE + CLASS */ 936 if ( !_dnsPacket_isEqualDomainName(pack1, pack2) || 937 !_dnsPacket_isEqualBytes(pack1, pack2, 2+2) ) 938 return 0; 939 940 return 1; 941} 942 943static int 944_dnsPacket_isEqualQuery( DnsPacket* pack1, DnsPacket* pack2 ) 945{ 946 int count1, count2; 947 948 /* compare the headers, ignore most fields */ 949 _dnsPacket_rewind(pack1); 950 _dnsPacket_rewind(pack2); 951 952 /* compare RD, ignore TC, see comment in _dnsPacket_checkQuery */ 953 if ((pack1->base[2] & 1) != (pack2->base[2] & 1)) { 954 XLOG("different RD"); 955 return 0; 956 } 957 958 /* assume: other flags are all 0 */ 959 _dnsPacket_skip(pack1, 4); 960 _dnsPacket_skip(pack2, 4); 961 962 /* compare QDCOUNT */ 963 count1 = _dnsPacket_readInt16(pack1); 964 count2 = _dnsPacket_readInt16(pack2); 965 if (count1 != count2 || count1 < 0) { 966 XLOG("different QDCOUNT"); 967 return 0; 968 } 969 970 /* assume: ANcount, NScount and ARcount are all 0 */ 971 _dnsPacket_skip(pack1, 6); 972 _dnsPacket_skip(pack2, 6); 973 974 /* compare the QDCOUNT QRs */ 975 for ( ; count1 > 0; count1-- ) { 976 if (!_dnsPacket_isEqualQR(pack1, pack2)) { 977 XLOG("different QR"); 978 return 0; 979 } 980 } 981 return 1; 982} 983 984/****************************************************************************/ 985/****************************************************************************/ 986/***** *****/ 987/***** *****/ 988/***** *****/ 989/****************************************************************************/ 990/****************************************************************************/ 991 992/* cache entry. for simplicity, 'hash' and 'hlink' are inlined in this 993 * structure though they are conceptually part of the hash table. 994 * 995 * similarly, mru_next and mru_prev are part of the global MRU list 996 */ 997typedef struct Entry { 998 unsigned int hash; /* hash value */ 999 struct Entry* hlink; /* next in collision chain */ 1000 struct Entry* mru_prev; 1001 struct Entry* mru_next; 1002 1003 const uint8_t* query; 1004 int querylen; 1005 const uint8_t* answer; 1006 int answerlen; 1007 time_t expires; /* time_t when the entry isn't valid any more */ 1008 int id; /* for debugging purpose */ 1009} Entry; 1010 1011/** 1012 * Parse the answer records and find the smallest 1013 * TTL among the answer records. 1014 * 1015 * The returned TTL is the number of seconds to 1016 * keep the answer in the cache. 1017 * 1018 * In case of parse error zero (0) is returned which 1019 * indicates that the answer shall not be cached. 1020 */ 1021static u_long 1022answer_getTTL(const void* answer, int answerlen) 1023{ 1024 ns_msg handle; 1025 int ancount, n; 1026 u_long result, ttl; 1027 ns_rr rr; 1028 1029 result = 0; 1030 if (ns_initparse(answer, answerlen, &handle) >= 0) { 1031 // get number of answer records 1032 ancount = ns_msg_count(handle, ns_s_an); 1033 for (n = 0; n < ancount; n++) { 1034 if (ns_parserr(&handle, ns_s_an, n, &rr) == 0) { 1035 ttl = ns_rr_ttl(rr); 1036 if (n == 0 || ttl < result) { 1037 result = ttl; 1038 } 1039 } else { 1040 XLOG("ns_parserr failed ancount no = %d. errno = %s\n", n, strerror(errno)); 1041 } 1042 } 1043 } else { 1044 XLOG("ns_parserr failed. %s\n", strerror(errno)); 1045 } 1046 1047 XLOG("TTL = %d\n", result); 1048 1049 return result; 1050} 1051 1052static void 1053entry_free( Entry* e ) 1054{ 1055 /* everything is allocated in a single memory block */ 1056 if (e) { 1057 free(e); 1058 } 1059} 1060 1061static __inline__ void 1062entry_mru_remove( Entry* e ) 1063{ 1064 e->mru_prev->mru_next = e->mru_next; 1065 e->mru_next->mru_prev = e->mru_prev; 1066} 1067 1068static __inline__ void 1069entry_mru_add( Entry* e, Entry* list ) 1070{ 1071 Entry* first = list->mru_next; 1072 1073 e->mru_next = first; 1074 e->mru_prev = list; 1075 1076 list->mru_next = e; 1077 first->mru_prev = e; 1078} 1079 1080/* compute the hash of a given entry, this is a hash of most 1081 * data in the query (key) */ 1082static unsigned 1083entry_hash( const Entry* e ) 1084{ 1085 DnsPacket pack[1]; 1086 1087 _dnsPacket_init(pack, e->query, e->querylen); 1088 return _dnsPacket_hashQuery(pack); 1089} 1090 1091/* initialize an Entry as a search key, this also checks the input query packet 1092 * returns 1 on success, or 0 in case of unsupported/malformed data */ 1093static int 1094entry_init_key( Entry* e, const void* query, int querylen ) 1095{ 1096 DnsPacket pack[1]; 1097 1098 memset(e, 0, sizeof(*e)); 1099 1100 e->query = query; 1101 e->querylen = querylen; 1102 e->hash = entry_hash(e); 1103 1104 _dnsPacket_init(pack, query, querylen); 1105 1106 return _dnsPacket_checkQuery(pack); 1107} 1108 1109/* allocate a new entry as a cache node */ 1110static Entry* 1111entry_alloc( const Entry* init, const void* answer, int answerlen ) 1112{ 1113 Entry* e; 1114 int size; 1115 1116 size = sizeof(*e) + init->querylen + answerlen; 1117 e = calloc(size, 1); 1118 if (e == NULL) 1119 return e; 1120 1121 e->hash = init->hash; 1122 e->query = (const uint8_t*)(e+1); 1123 e->querylen = init->querylen; 1124 1125 memcpy( (char*)e->query, init->query, e->querylen ); 1126 1127 e->answer = e->query + e->querylen; 1128 e->answerlen = answerlen; 1129 1130 memcpy( (char*)e->answer, answer, e->answerlen ); 1131 1132 return e; 1133} 1134 1135static int 1136entry_equals( const Entry* e1, const Entry* e2 ) 1137{ 1138 DnsPacket pack1[1], pack2[1]; 1139 1140 if (e1->querylen != e2->querylen) { 1141 return 0; 1142 } 1143 _dnsPacket_init(pack1, e1->query, e1->querylen); 1144 _dnsPacket_init(pack2, e2->query, e2->querylen); 1145 1146 return _dnsPacket_isEqualQuery(pack1, pack2); 1147} 1148 1149/****************************************************************************/ 1150/****************************************************************************/ 1151/***** *****/ 1152/***** *****/ 1153/***** *****/ 1154/****************************************************************************/ 1155/****************************************************************************/ 1156 1157/* We use a simple hash table with external collision lists 1158 * for simplicity, the hash-table fields 'hash' and 'hlink' are 1159 * inlined in the Entry structure. 1160 */ 1161 1162typedef struct resolv_cache { 1163 int max_entries; 1164 int num_entries; 1165 Entry mru_list; 1166 pthread_mutex_t lock; 1167 unsigned generation; 1168 int last_id; 1169 Entry* entries; 1170} Cache; 1171 1172typedef struct resolv_cache_info { 1173 char ifname[IF_NAMESIZE + 1]; 1174 struct in_addr ifaddr; 1175 Cache* cache; 1176 struct resolv_cache_info* next; 1177 char* nameservers[MAXNS +1]; 1178 struct addrinfo* nsaddrinfo[MAXNS + 1]; 1179} CacheInfo; 1180 1181#define HTABLE_VALID(x) ((x) != NULL && (x) != HTABLE_DELETED) 1182 1183static void 1184_cache_flush_locked( Cache* cache ) 1185{ 1186 int nn; 1187 time_t now = _time_now(); 1188 1189 for (nn = 0; nn < cache->max_entries; nn++) 1190 { 1191 Entry** pnode = (Entry**) &cache->entries[nn]; 1192 1193 while (*pnode != NULL) { 1194 Entry* node = *pnode; 1195 *pnode = node->hlink; 1196 entry_free(node); 1197 } 1198 } 1199 1200 cache->mru_list.mru_next = cache->mru_list.mru_prev = &cache->mru_list; 1201 cache->num_entries = 0; 1202 cache->last_id = 0; 1203 1204 XLOG("*************************\n" 1205 "*** DNS CACHE FLUSHED ***\n" 1206 "*************************"); 1207} 1208 1209/* Return max number of entries allowed in the cache, 1210 * i.e. cache size. The cache size is either defined 1211 * by system property ro.net.dns_cache_size or by 1212 * CONFIG_MAX_ENTRIES if system property not set 1213 * or set to invalid value. */ 1214static int 1215_res_cache_get_max_entries( void ) 1216{ 1217 int result = -1; 1218 char cache_size[PROP_VALUE_MAX]; 1219 1220 if (__system_property_get(DNS_CACHE_SIZE_PROP_NAME, cache_size) > 0) { 1221 result = atoi(cache_size); 1222 } 1223 1224 // ro.net.dns_cache_size not set or set to negative value 1225 if (result <= 0) { 1226 result = CONFIG_MAX_ENTRIES; 1227 } 1228 1229 XLOG("cache size: %d", result); 1230 return result; 1231} 1232 1233static struct resolv_cache* 1234_resolv_cache_create( void ) 1235{ 1236 struct resolv_cache* cache; 1237 1238 cache = calloc(sizeof(*cache), 1); 1239 if (cache) { 1240 cache->max_entries = _res_cache_get_max_entries(); 1241 cache->entries = calloc(sizeof(*cache->entries), cache->max_entries); 1242 if (cache->entries) { 1243 cache->generation = ~0U; 1244 pthread_mutex_init( &cache->lock, NULL ); 1245 cache->mru_list.mru_prev = cache->mru_list.mru_next = &cache->mru_list; 1246 XLOG("%s: cache created\n", __FUNCTION__); 1247 } else { 1248 free(cache); 1249 cache = NULL; 1250 } 1251 } 1252 return cache; 1253} 1254 1255 1256#if DEBUG 1257static void 1258_dump_query( const uint8_t* query, int querylen ) 1259{ 1260 char temp[256], *p=temp, *end=p+sizeof(temp); 1261 DnsPacket pack[1]; 1262 1263 _dnsPacket_init(pack, query, querylen); 1264 p = _dnsPacket_bprintQuery(pack, p, end); 1265 XLOG("QUERY: %s", temp); 1266} 1267 1268static void 1269_cache_dump_mru( Cache* cache ) 1270{ 1271 char temp[512], *p=temp, *end=p+sizeof(temp); 1272 Entry* e; 1273 1274 p = _bprint(temp, end, "MRU LIST (%2d): ", cache->num_entries); 1275 for (e = cache->mru_list.mru_next; e != &cache->mru_list; e = e->mru_next) 1276 p = _bprint(p, end, " %d", e->id); 1277 1278 XLOG("%s", temp); 1279} 1280 1281static void 1282_dump_answer(const void* answer, int answerlen) 1283{ 1284 res_state statep; 1285 FILE* fp; 1286 char* buf; 1287 int fileLen; 1288 1289 fp = fopen("/data/reslog.txt", "w+"); 1290 if (fp != NULL) { 1291 statep = __res_get_state(); 1292 1293 res_pquery(statep, answer, answerlen, fp); 1294 1295 //Get file length 1296 fseek(fp, 0, SEEK_END); 1297 fileLen=ftell(fp); 1298 fseek(fp, 0, SEEK_SET); 1299 buf = (char *)malloc(fileLen+1); 1300 if (buf != NULL) { 1301 //Read file contents into buffer 1302 fread(buf, fileLen, 1, fp); 1303 XLOG("%s\n", buf); 1304 free(buf); 1305 } 1306 fclose(fp); 1307 remove("/data/reslog.txt"); 1308 } 1309 else { 1310 XLOG("_dump_answer: can't open file\n"); 1311 } 1312} 1313#endif 1314 1315#if DEBUG 1316# define XLOG_QUERY(q,len) _dump_query((q), (len)) 1317# define XLOG_ANSWER(a, len) _dump_answer((a), (len)) 1318#else 1319# define XLOG_QUERY(q,len) ((void)0) 1320# define XLOG_ANSWER(a,len) ((void)0) 1321#endif 1322 1323/* This function tries to find a key within the hash table 1324 * In case of success, it will return a *pointer* to the hashed key. 1325 * In case of failure, it will return a *pointer* to NULL 1326 * 1327 * So, the caller must check '*result' to check for success/failure. 1328 * 1329 * The main idea is that the result can later be used directly in 1330 * calls to _resolv_cache_add or _resolv_cache_remove as the 'lookup' 1331 * parameter. This makes the code simpler and avoids re-searching 1332 * for the key position in the htable. 1333 * 1334 * The result of a lookup_p is only valid until you alter the hash 1335 * table. 1336 */ 1337static Entry** 1338_cache_lookup_p( Cache* cache, 1339 Entry* key ) 1340{ 1341 int index = key->hash % cache->max_entries; 1342 Entry** pnode = (Entry**) &cache->entries[ index ]; 1343 1344 while (*pnode != NULL) { 1345 Entry* node = *pnode; 1346 1347 if (node == NULL) 1348 break; 1349 1350 if (node->hash == key->hash && entry_equals(node, key)) 1351 break; 1352 1353 pnode = &node->hlink; 1354 } 1355 return pnode; 1356} 1357 1358/* Add a new entry to the hash table. 'lookup' must be the 1359 * result of an immediate previous failed _lookup_p() call 1360 * (i.e. with *lookup == NULL), and 'e' is the pointer to the 1361 * newly created entry 1362 */ 1363static void 1364_cache_add_p( Cache* cache, 1365 Entry** lookup, 1366 Entry* e ) 1367{ 1368 *lookup = e; 1369 e->id = ++cache->last_id; 1370 entry_mru_add(e, &cache->mru_list); 1371 cache->num_entries += 1; 1372 1373 XLOG("%s: entry %d added (count=%d)", __FUNCTION__, 1374 e->id, cache->num_entries); 1375} 1376 1377/* Remove an existing entry from the hash table, 1378 * 'lookup' must be the result of an immediate previous 1379 * and succesful _lookup_p() call. 1380 */ 1381static void 1382_cache_remove_p( Cache* cache, 1383 Entry** lookup ) 1384{ 1385 Entry* e = *lookup; 1386 1387 XLOG("%s: entry %d removed (count=%d)", __FUNCTION__, 1388 e->id, cache->num_entries-1); 1389 1390 entry_mru_remove(e); 1391 *lookup = e->hlink; 1392 entry_free(e); 1393 cache->num_entries -= 1; 1394} 1395 1396/* Remove the oldest entry from the hash table. 1397 */ 1398static void 1399_cache_remove_oldest( Cache* cache ) 1400{ 1401 Entry* oldest = cache->mru_list.mru_prev; 1402 Entry** lookup = _cache_lookup_p(cache, oldest); 1403 1404 if (*lookup == NULL) { /* should not happen */ 1405 XLOG("%s: OLDEST NOT IN HTABLE ?", __FUNCTION__); 1406 return; 1407 } 1408 _cache_remove_p(cache, lookup); 1409} 1410 1411 1412ResolvCacheStatus 1413_resolv_cache_lookup( struct resolv_cache* cache, 1414 const void* query, 1415 int querylen, 1416 void* answer, 1417 int answersize, 1418 int *answerlen ) 1419{ 1420 DnsPacket pack[1]; 1421 Entry key[1]; 1422 int index; 1423 Entry** lookup; 1424 Entry* e; 1425 time_t now; 1426 1427 ResolvCacheStatus result = RESOLV_CACHE_NOTFOUND; 1428 1429 XLOG("%s: lookup", __FUNCTION__); 1430 XLOG_QUERY(query, querylen); 1431 1432 /* we don't cache malformed queries */ 1433 if (!entry_init_key(key, query, querylen)) { 1434 XLOG("%s: unsupported query", __FUNCTION__); 1435 return RESOLV_CACHE_UNSUPPORTED; 1436 } 1437 /* lookup cache */ 1438 pthread_mutex_lock( &cache->lock ); 1439 1440 /* see the description of _lookup_p to understand this. 1441 * the function always return a non-NULL pointer. 1442 */ 1443 lookup = _cache_lookup_p(cache, key); 1444 e = *lookup; 1445 1446 if (e == NULL) { 1447 XLOG( "NOT IN CACHE"); 1448 goto Exit; 1449 } 1450 1451 now = _time_now(); 1452 1453 /* remove stale entries here */ 1454 if (now >= e->expires) { 1455 XLOG( " NOT IN CACHE (STALE ENTRY %p DISCARDED)", *lookup ); 1456 _cache_remove_p(cache, lookup); 1457 goto Exit; 1458 } 1459 1460 *answerlen = e->answerlen; 1461 if (e->answerlen > answersize) { 1462 /* NOTE: we return UNSUPPORTED if the answer buffer is too short */ 1463 result = RESOLV_CACHE_UNSUPPORTED; 1464 XLOG(" ANSWER TOO LONG"); 1465 goto Exit; 1466 } 1467 1468 memcpy( answer, e->answer, e->answerlen ); 1469 1470 /* bump up this entry to the top of the MRU list */ 1471 if (e != cache->mru_list.mru_next) { 1472 entry_mru_remove( e ); 1473 entry_mru_add( e, &cache->mru_list ); 1474 } 1475 1476 XLOG( "FOUND IN CACHE entry=%p", e ); 1477 result = RESOLV_CACHE_FOUND; 1478 1479Exit: 1480 pthread_mutex_unlock( &cache->lock ); 1481 return result; 1482} 1483 1484 1485void 1486_resolv_cache_add( struct resolv_cache* cache, 1487 const void* query, 1488 int querylen, 1489 const void* answer, 1490 int answerlen ) 1491{ 1492 Entry key[1]; 1493 Entry* e; 1494 Entry** lookup; 1495 u_long ttl; 1496 1497 /* don't assume that the query has already been cached 1498 */ 1499 if (!entry_init_key( key, query, querylen )) { 1500 XLOG( "%s: passed invalid query ?", __FUNCTION__); 1501 return; 1502 } 1503 1504 pthread_mutex_lock( &cache->lock ); 1505 1506 XLOG( "%s: query:", __FUNCTION__ ); 1507 XLOG_QUERY(query,querylen); 1508 XLOG_ANSWER(answer, answerlen); 1509#if DEBUG_DATA 1510 XLOG( "answer:"); 1511 XLOG_BYTES(answer,answerlen); 1512#endif 1513 1514 lookup = _cache_lookup_p(cache, key); 1515 e = *lookup; 1516 1517 if (e != NULL) { /* should not happen */ 1518 XLOG("%s: ALREADY IN CACHE (%p) ? IGNORING ADD", 1519 __FUNCTION__, e); 1520 goto Exit; 1521 } 1522 1523 if (cache->num_entries >= cache->max_entries) { 1524 _cache_remove_oldest(cache); 1525 /* need to lookup again */ 1526 lookup = _cache_lookup_p(cache, key); 1527 e = *lookup; 1528 if (e != NULL) { 1529 XLOG("%s: ALREADY IN CACHE (%p) ? IGNORING ADD", 1530 __FUNCTION__, e); 1531 goto Exit; 1532 } 1533 } 1534 1535 ttl = answer_getTTL(answer, answerlen); 1536 if (ttl > 0) { 1537 e = entry_alloc(key, answer, answerlen); 1538 if (e != NULL) { 1539 e->expires = ttl + _time_now(); 1540 _cache_add_p(cache, lookup, e); 1541 } 1542 } 1543#if DEBUG 1544 _cache_dump_mru(cache); 1545#endif 1546Exit: 1547 pthread_mutex_unlock( &cache->lock ); 1548} 1549 1550/****************************************************************************/ 1551/****************************************************************************/ 1552/***** *****/ 1553/***** *****/ 1554/***** *****/ 1555/****************************************************************************/ 1556/****************************************************************************/ 1557 1558static pthread_once_t _res_cache_once; 1559 1560// Head of the list of caches. Protected by _res_cache_list_lock. 1561static struct resolv_cache_info _res_cache_list; 1562 1563// name of the current default inteface 1564static char _res_default_ifname[IF_NAMESIZE + 1]; 1565 1566// lock protecting everything in the _resolve_cache_info structs (next ptr, etc) 1567static pthread_mutex_t _res_cache_list_lock; 1568 1569 1570/* lookup the default interface name */ 1571static char *_get_default_iface_locked(); 1572/* insert resolv_cache_info into the list of resolv_cache_infos */ 1573static void _insert_cache_info_locked(struct resolv_cache_info* cache_info); 1574/* creates a resolv_cache_info */ 1575static struct resolv_cache_info* _create_cache_info( void ); 1576/* gets cache associated with an interface name, or NULL if none exists */ 1577static struct resolv_cache* _find_named_cache_locked(const char* ifname); 1578/* gets a resolv_cache_info associated with an interface name, or NULL if not found */ 1579static struct resolv_cache_info* _find_cache_info_locked(const char* ifname); 1580/* free dns name server list of a resolv_cache_info structure */ 1581static void _free_nameservers(struct resolv_cache_info* cache_info); 1582/* look up the named cache, and creates one if needed */ 1583static struct resolv_cache* _get_res_cache_for_iface_locked(const char* ifname); 1584/* empty the named cache */ 1585static void _flush_cache_for_iface_locked(const char* ifname); 1586/* empty the nameservers set for the named cache */ 1587static void _free_nameservers_locked(struct resolv_cache_info* cache_info); 1588/* lookup the namserver for the name interface */ 1589static int _get_nameserver_locked(const char* ifname, int n, char* addr, int addrLen); 1590/* lookup the addr of the nameserver for the named interface */ 1591static struct addrinfo* _get_nameserver_addr_locked(const char* ifname, int n); 1592/* lookup the inteface's address */ 1593static struct in_addr* _get_addr_locked(const char * ifname); 1594 1595 1596 1597static void 1598_res_cache_init(void) 1599{ 1600 const char* env = getenv(CONFIG_ENV); 1601 1602 if (env && atoi(env) == 0) { 1603 /* the cache is disabled */ 1604 return; 1605 } 1606 1607 memset(&_res_default_ifname, 0, sizeof(_res_default_ifname)); 1608 memset(&_res_cache_list, 0, sizeof(_res_cache_list)); 1609 pthread_mutex_init(&_res_cache_list_lock, NULL); 1610} 1611 1612struct resolv_cache* 1613__get_res_cache(void) 1614{ 1615 struct resolv_cache *cache; 1616 1617 pthread_once(&_res_cache_once, _res_cache_init); 1618 1619 pthread_mutex_lock(&_res_cache_list_lock); 1620 1621 char* ifname = _get_default_iface_locked(); 1622 1623 // if default interface not set then use the first cache 1624 // associated with an interface as the default one. 1625 if (ifname[0] == '\0') { 1626 struct resolv_cache_info* cache_info = _res_cache_list.next; 1627 while (cache_info) { 1628 if (cache_info->ifname[0] != '\0') { 1629 ifname = cache_info->ifname; 1630 } 1631 1632 cache_info = cache_info->next; 1633 } 1634 } 1635 cache = _get_res_cache_for_iface_locked(ifname); 1636 1637 pthread_mutex_unlock(&_res_cache_list_lock); 1638 XLOG("_get_res_cache. default_ifname = %s\n", ifname); 1639 return cache; 1640} 1641 1642static struct resolv_cache* 1643_get_res_cache_for_iface_locked(const char* ifname) 1644{ 1645 if (ifname == NULL) 1646 return NULL; 1647 1648 struct resolv_cache* cache = _find_named_cache_locked(ifname); 1649 if (!cache) { 1650 struct resolv_cache_info* cache_info = _create_cache_info(); 1651 if (cache_info) { 1652 cache = _resolv_cache_create(); 1653 if (cache) { 1654 int len = sizeof(cache_info->ifname); 1655 cache_info->cache = cache; 1656 strncpy(cache_info->ifname, ifname, len - 1); 1657 cache_info->ifname[len - 1] = '\0'; 1658 1659 _insert_cache_info_locked(cache_info); 1660 } else { 1661 free(cache_info); 1662 } 1663 } 1664 } 1665 return cache; 1666} 1667 1668void 1669_resolv_cache_reset(unsigned generation) 1670{ 1671 XLOG("%s: generation=%d", __FUNCTION__, generation); 1672 1673 pthread_once(&_res_cache_once, _res_cache_init); 1674 pthread_mutex_lock(&_res_cache_list_lock); 1675 1676 char* ifname = _get_default_iface_locked(); 1677 // if default interface not set then use the first cache 1678 // associated with an interface as the default one. 1679 // Note: Copied the code from __get_res_cache since this 1680 // method will be deleted/obsolete when cache per interface 1681 // implemented all over 1682 if (ifname[0] == '\0') { 1683 struct resolv_cache_info* cache_info = _res_cache_list.next; 1684 while (cache_info) { 1685 if (cache_info->ifname[0] != '\0') { 1686 ifname = cache_info->ifname; 1687 } 1688 1689 cache_info = cache_info->next; 1690 } 1691 } 1692 struct resolv_cache* cache = _get_res_cache_for_iface_locked(ifname); 1693 1694 if (cache == NULL) { 1695 pthread_mutex_unlock(&_res_cache_list_lock); 1696 return; 1697 } 1698 1699 pthread_mutex_lock( &cache->lock ); 1700 if (cache->generation != generation) { 1701 _cache_flush_locked(cache); 1702 cache->generation = generation; 1703 } 1704 pthread_mutex_unlock( &cache->lock ); 1705 1706 pthread_mutex_unlock(&_res_cache_list_lock); 1707} 1708 1709void 1710_resolv_flush_cache_for_default_iface(void) 1711{ 1712 char* ifname; 1713 1714 pthread_once(&_res_cache_once, _res_cache_init); 1715 pthread_mutex_lock(&_res_cache_list_lock); 1716 1717 ifname = _get_default_iface_locked(); 1718 _flush_cache_for_iface_locked(ifname); 1719 1720 pthread_mutex_unlock(&_res_cache_list_lock); 1721} 1722 1723void 1724_resolv_flush_cache_for_iface(const char* ifname) 1725{ 1726 pthread_once(&_res_cache_once, _res_cache_init); 1727 pthread_mutex_lock(&_res_cache_list_lock); 1728 1729 _flush_cache_for_iface_locked(ifname); 1730 1731 pthread_mutex_unlock(&_res_cache_list_lock); 1732} 1733 1734static void 1735_flush_cache_for_iface_locked(const char* ifname) 1736{ 1737 struct resolv_cache* cache = _find_named_cache_locked(ifname); 1738 if (cache) { 1739 pthread_mutex_lock(&cache->lock); 1740 _cache_flush_locked(cache); 1741 pthread_mutex_unlock(&cache->lock); 1742 } 1743} 1744 1745static struct resolv_cache_info* 1746_create_cache_info(void) 1747{ 1748 struct resolv_cache_info* cache_info; 1749 1750 cache_info = calloc(sizeof(*cache_info), 1); 1751 return cache_info; 1752} 1753 1754static void 1755_insert_cache_info_locked(struct resolv_cache_info* cache_info) 1756{ 1757 struct resolv_cache_info* last; 1758 1759 for (last = &_res_cache_list; last->next; last = last->next); 1760 1761 last->next = cache_info; 1762 1763} 1764 1765static struct resolv_cache* 1766_find_named_cache_locked(const char* ifname) { 1767 1768 struct resolv_cache_info* info = _find_cache_info_locked(ifname); 1769 1770 if (info != NULL) return info->cache; 1771 1772 return NULL; 1773} 1774 1775static struct resolv_cache_info* 1776_find_cache_info_locked(const char* ifname) 1777{ 1778 if (ifname == NULL) 1779 return NULL; 1780 1781 struct resolv_cache_info* cache_info = _res_cache_list.next; 1782 1783 while (cache_info) { 1784 if (strcmp(cache_info->ifname, ifname) == 0) { 1785 break; 1786 } 1787 1788 cache_info = cache_info->next; 1789 } 1790 return cache_info; 1791} 1792 1793static char* 1794_get_default_iface_locked(void) 1795{ 1796 char* iface = _res_default_ifname; 1797 1798 return iface; 1799} 1800 1801void 1802_resolv_set_default_iface(const char* ifname) 1803{ 1804 XLOG("_resolv_set_default_if ifname %s\n",ifname); 1805 1806 pthread_once(&_res_cache_once, _res_cache_init); 1807 pthread_mutex_lock(&_res_cache_list_lock); 1808 1809 int size = sizeof(_res_default_ifname); 1810 memset(_res_default_ifname, 0, size); 1811 strncpy(_res_default_ifname, ifname, size - 1); 1812 _res_default_ifname[size - 1] = '\0'; 1813 1814 pthread_mutex_unlock(&_res_cache_list_lock); 1815} 1816 1817void 1818_resolv_set_nameservers_for_iface(const char* ifname, char** servers, int numservers) 1819{ 1820 int i, rt, index; 1821 struct addrinfo hints; 1822 char sbuf[NI_MAXSERV]; 1823 1824 pthread_once(&_res_cache_once, _res_cache_init); 1825 1826 pthread_mutex_lock(&_res_cache_list_lock); 1827 // creates the cache if not created 1828 _get_res_cache_for_iface_locked(ifname); 1829 1830 struct resolv_cache_info* cache_info = _find_cache_info_locked(ifname); 1831 1832 if (cache_info != NULL) { 1833 // free current before adding new 1834 _free_nameservers_locked(cache_info); 1835 1836 memset(&hints, 0, sizeof(hints)); 1837 hints.ai_family = PF_UNSPEC; 1838 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 1839 hints.ai_flags = AI_NUMERICHOST; 1840 sprintf(sbuf, "%u", NAMESERVER_PORT); 1841 1842 index = 0; 1843 for (i = 0; i < numservers && i < MAXNS; i++) { 1844 rt = getaddrinfo(servers[i], sbuf, &hints, &cache_info->nsaddrinfo[index]); 1845 if (rt == 0) { 1846 cache_info->nameservers[index] = strdup(servers[i]); 1847 index++; 1848 } else { 1849 cache_info->nsaddrinfo[index] = NULL; 1850 } 1851 } 1852 } 1853 pthread_mutex_unlock(&_res_cache_list_lock); 1854} 1855 1856static void 1857_free_nameservers_locked(struct resolv_cache_info* cache_info) 1858{ 1859 int i; 1860 for (i = 0; i <= MAXNS; i++) { 1861 free(cache_info->nameservers[i]); 1862 cache_info->nameservers[i] = NULL; 1863 if (cache_info->nsaddrinfo[i] != NULL) { 1864 freeaddrinfo(cache_info->nsaddrinfo[i]); 1865 cache_info->nsaddrinfo[i] = NULL; 1866 } 1867 } 1868} 1869 1870int 1871_resolv_cache_get_nameserver(int n, char* addr, int addrLen) 1872{ 1873 char *ifname; 1874 int result = 0; 1875 1876 pthread_once(&_res_cache_once, _res_cache_init); 1877 pthread_mutex_lock(&_res_cache_list_lock); 1878 1879 ifname = _get_default_iface_locked(); 1880 result = _get_nameserver_locked(ifname, n, addr, addrLen); 1881 1882 pthread_mutex_unlock(&_res_cache_list_lock); 1883 return result; 1884} 1885 1886static int 1887_get_nameserver_locked(const char* ifname, int n, char* addr, int addrLen) 1888{ 1889 int len = 0; 1890 char* ns; 1891 struct resolv_cache_info* cache_info; 1892 1893 if (n < 1 || n > MAXNS || !addr) 1894 return 0; 1895 1896 cache_info = _find_cache_info_locked(ifname); 1897 if (cache_info) { 1898 ns = cache_info->nameservers[n - 1]; 1899 if (ns) { 1900 len = strlen(ns); 1901 if (len < addrLen) { 1902 strncpy(addr, ns, len); 1903 addr[len] = '\0'; 1904 } else { 1905 len = 0; 1906 } 1907 } 1908 } 1909 1910 return len; 1911} 1912 1913struct addrinfo* 1914_cache_get_nameserver_addr(int n) 1915{ 1916 struct addrinfo *result; 1917 char* ifname; 1918 1919 pthread_once(&_res_cache_once, _res_cache_init); 1920 pthread_mutex_lock(&_res_cache_list_lock); 1921 1922 ifname = _get_default_iface_locked(); 1923 1924 result = _get_nameserver_addr_locked(ifname, n); 1925 pthread_mutex_unlock(&_res_cache_list_lock); 1926 return result; 1927} 1928 1929static struct addrinfo* 1930_get_nameserver_addr_locked(const char* ifname, int n) 1931{ 1932 struct addrinfo* ai = NULL; 1933 struct resolv_cache_info* cache_info; 1934 1935 if (n < 1 || n > MAXNS) 1936 return NULL; 1937 1938 cache_info = _find_cache_info_locked(ifname); 1939 if (cache_info) { 1940 ai = cache_info->nsaddrinfo[n - 1]; 1941 } 1942 return ai; 1943} 1944 1945void 1946_resolv_set_addr_of_iface(const char* ifname, struct in_addr* addr) 1947{ 1948 pthread_once(&_res_cache_once, _res_cache_init); 1949 pthread_mutex_lock(&_res_cache_list_lock); 1950 struct resolv_cache_info* cache_info = _find_cache_info_locked(ifname); 1951 if (cache_info) { 1952 memcpy(&cache_info->ifaddr, addr, sizeof(*addr)); 1953 1954 if (DEBUG) { 1955 char* addr_s = inet_ntoa(cache_info->ifaddr); 1956 XLOG("address of interface %s is %s\n", ifname, addr_s); 1957 } 1958 } 1959 pthread_mutex_unlock(&_res_cache_list_lock); 1960} 1961 1962struct in_addr* 1963_resolv_get_addr_of_default_iface(void) 1964{ 1965 struct in_addr* ai = NULL; 1966 char* ifname; 1967 1968 pthread_once(&_res_cache_once, _res_cache_init); 1969 pthread_mutex_lock(&_res_cache_list_lock); 1970 ifname = _get_default_iface_locked(); 1971 ai = _get_addr_locked(ifname); 1972 pthread_mutex_unlock(&_res_cache_list_lock); 1973 1974 return ai; 1975} 1976 1977struct in_addr* 1978_resolv_get_addr_of_iface(const char* ifname) 1979{ 1980 struct in_addr* ai = NULL; 1981 1982 pthread_once(&_res_cache_once, _res_cache_init); 1983 pthread_mutex_lock(&_res_cache_list_lock); 1984 ai =_get_addr_locked(ifname); 1985 pthread_mutex_unlock(&_res_cache_list_lock); 1986 return ai; 1987} 1988 1989static struct in_addr* 1990_get_addr_locked(const char * ifname) 1991{ 1992 struct resolv_cache_info* cache_info = _find_cache_info_locked(ifname); 1993 if (cache_info) { 1994 return &cache_info->ifaddr; 1995 } 1996 return NULL; 1997} 1998