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 #include "resolv_iface.h" 46 47 /* This code implements a small and *simple* DNS resolver cache. 48 * 49 * It is only used to cache DNS answers for a time defined by the smallest TTL 50 * among the answer records in order to reduce DNS traffic. It is not supposed 51 * to be a full DNS cache, since we plan to implement that in the future in a 52 * dedicated process running on the system. 53 * 54 * Note that its design is kept simple very intentionally, i.e.: 55 * 56 * - it takes raw DNS query packet data as input, and returns raw DNS 57 * answer packet data as output 58 * 59 * (this means that two similar queries that encode the DNS name 60 * differently will be treated distinctly). 61 * 62 * the smallest TTL value among the answer records are used as the time 63 * to keep an answer in the cache. 64 * 65 * this is bad, but we absolutely want to avoid parsing the answer packets 66 * (and should be solved by the later full DNS cache process). 67 * 68 * - the implementation is just a (query-data) => (answer-data) hash table 69 * with a trivial least-recently-used expiration policy. 70 * 71 * Doing this keeps the code simple and avoids to deal with a lot of things 72 * that a full DNS cache is expected to do. 73 * 74 * The API is also very simple: 75 * 76 * - the client calls _resolv_cache_get() to obtain a handle to the cache. 77 * this will initialize the cache on first usage. the result can be NULL 78 * if the cache is disabled. 79 * 80 * - the client calls _resolv_cache_lookup() before performing a query 81 * 82 * if the function returns RESOLV_CACHE_FOUND, a copy of the answer data 83 * has been copied into the client-provided answer buffer. 84 * 85 * if the function returns RESOLV_CACHE_NOTFOUND, the client should perform 86 * a request normally, *then* call _resolv_cache_add() to add the received 87 * answer to the cache. 88 * 89 * if the function returns RESOLV_CACHE_UNSUPPORTED, the client should 90 * perform a request normally, and *not* call _resolv_cache_add() 91 * 92 * note that RESOLV_CACHE_UNSUPPORTED is also returned if the answer buffer 93 * is too short to accomodate the cached result. 94 * 95 * - when network settings change, the cache must be flushed since the list 96 * of DNS servers probably changed. this is done by calling 97 * _resolv_cache_reset() 98 * 99 * the parameter to this function must be an ever-increasing generation 100 * number corresponding to the current network settings state. 101 * 102 * This is done because several threads could detect the same network 103 * settings change (but at different times) and will all end up calling the 104 * same function. Comparing with the last used generation number ensures 105 * that the cache is only flushed once per network change. 106 */ 107 108 /* the name of an environment variable that will be checked the first time 109 * this code is called if its value is "0", then the resolver cache is 110 * disabled. 111 */ 112 #define CONFIG_ENV "BIONIC_DNSCACHE" 113 114 /* entries older than CONFIG_SECONDS seconds are always discarded. 115 */ 116 #define CONFIG_SECONDS (60*10) /* 10 minutes */ 117 118 /* default number of entries kept in the cache. This value has been 119 * determined by browsing through various sites and counting the number 120 * of corresponding requests. Keep in mind that our framework is currently 121 * performing two requests per name lookup (one for IPv4, the other for IPv6) 122 * 123 * www.google.com 4 124 * www.ysearch.com 6 125 * www.amazon.com 8 126 * www.nytimes.com 22 127 * www.espn.com 28 128 * www.msn.com 28 129 * www.lemonde.fr 35 130 * 131 * (determined in 2009-2-17 from Paris, France, results may vary depending 132 * on location) 133 * 134 * most high-level websites use lots of media/ad servers with different names 135 * but these are generally reused when browsing through the site. 136 * 137 * As such, a value of 64 should be relatively comfortable at the moment. 138 * 139 * The system property ro.net.dns_cache_size can be used to override the default 140 * value with a custom value 141 * 142 * 143 * ****************************************** 144 * * NOTE - this has changed. 145 * * 1) we've added IPv6 support so each dns query results in 2 responses 146 * * 2) we've made this a system-wide cache, so the cost is less (it's not 147 * * duplicated in each process) and the need is greater (more processes 148 * * making different requests). 149 * * Upping by 2x for IPv6 150 * * Upping by another 5x for the centralized nature 151 * ***************************************** 152 */ 153 #define CONFIG_MAX_ENTRIES 64 * 2 * 5 154 /* name of the system property that can be used to set the cache size */ 155 #define DNS_CACHE_SIZE_PROP_NAME "ro.net.dns_cache_size" 156 157 /****************************************************************************/ 158 /****************************************************************************/ 159 /***** *****/ 160 /***** *****/ 161 /***** *****/ 162 /****************************************************************************/ 163 /****************************************************************************/ 164 165 /* set to 1 to debug cache operations */ 166 #define DEBUG 0 167 168 /* set to 1 to debug query data */ 169 #define DEBUG_DATA 0 170 171 #undef XLOG 172 #if DEBUG 173 # include <logd.h> 174 # define XLOG(...) \ 175 __libc_android_log_print(ANDROID_LOG_DEBUG,"libc",__VA_ARGS__) 176 177 #include <stdio.h> 178 #include <stdarg.h> 179 180 /** BOUNDED BUFFER FORMATTING 181 **/ 182 183 /* technical note: 184 * 185 * the following debugging routines are used to append data to a bounded 186 * buffer they take two parameters that are: 187 * 188 * - p : a pointer to the current cursor position in the buffer 189 * this value is initially set to the buffer's address. 190 * 191 * - end : the address of the buffer's limit, i.e. of the first byte 192 * after the buffer. this address should never be touched. 193 * 194 * IMPORTANT: it is assumed that end > buffer_address, i.e. 195 * that the buffer is at least one byte. 196 * 197 * the _bprint_() functions return the new value of 'p' after the data 198 * has been appended, and also ensure the following: 199 * 200 * - the returned value will never be strictly greater than 'end' 201 * 202 * - a return value equal to 'end' means that truncation occured 203 * (in which case, end[-1] will be set to 0) 204 * 205 * - after returning from a _bprint_() function, the content of the buffer 206 * is always 0-terminated, even in the event of truncation. 207 * 208 * these conventions allow you to call _bprint_ functions multiple times and 209 * only check for truncation at the end of the sequence, as in: 210 * 211 * char buff[1000], *p = buff, *end = p + sizeof(buff); 212 * 213 * p = _bprint_c(p, end, '"'); 214 * p = _bprint_s(p, end, my_string); 215 * p = _bprint_c(p, end, '"'); 216 * 217 * if (p >= end) { 218 * // buffer was too small 219 * } 220 * 221 * printf( "%s", buff ); 222 */ 223 224 /* add a char to a bounded buffer */ 225 static char* 226 _bprint_c( char* p, char* end, int c ) 227 { 228 if (p < end) { 229 if (p+1 == end) 230 *p++ = 0; 231 else { 232 *p++ = (char) c; 233 *p = 0; 234 } 235 } 236 return p; 237 } 238 239 /* add a sequence of bytes to a bounded buffer */ 240 static char* 241 _bprint_b( char* p, char* end, const char* buf, int len ) 242 { 243 int avail = end - p; 244 245 if (avail <= 0 || len <= 0) 246 return p; 247 248 if (avail > len) 249 avail = len; 250 251 memcpy( p, buf, avail ); 252 p += avail; 253 254 if (p < end) 255 p[0] = 0; 256 else 257 end[-1] = 0; 258 259 return p; 260 } 261 262 /* add a string to a bounded buffer */ 263 static char* 264 _bprint_s( char* p, char* end, const char* str ) 265 { 266 return _bprint_b(p, end, str, strlen(str)); 267 } 268 269 /* add a formatted string to a bounded buffer */ 270 static char* 271 _bprint( char* p, char* end, const char* format, ... ) 272 { 273 int avail, n; 274 va_list args; 275 276 avail = end - p; 277 278 if (avail <= 0) 279 return p; 280 281 va_start(args, format); 282 n = vsnprintf( p, avail, format, args); 283 va_end(args); 284 285 /* certain C libraries return -1 in case of truncation */ 286 if (n < 0 || n > avail) 287 n = avail; 288 289 p += n; 290 /* certain C libraries do not zero-terminate in case of truncation */ 291 if (p == end) 292 p[-1] = 0; 293 294 return p; 295 } 296 297 /* add a hex value to a bounded buffer, up to 8 digits */ 298 static char* 299 _bprint_hex( char* p, char* end, unsigned value, int numDigits ) 300 { 301 char text[sizeof(unsigned)*2]; 302 int nn = 0; 303 304 while (numDigits-- > 0) { 305 text[nn++] = "0123456789abcdef"[(value >> (numDigits*4)) & 15]; 306 } 307 return _bprint_b(p, end, text, nn); 308 } 309 310 /* add the hexadecimal dump of some memory area to a bounded buffer */ 311 static char* 312 _bprint_hexdump( char* p, char* end, const uint8_t* data, int datalen ) 313 { 314 int lineSize = 16; 315 316 while (datalen > 0) { 317 int avail = datalen; 318 int nn; 319 320 if (avail > lineSize) 321 avail = lineSize; 322 323 for (nn = 0; nn < avail; nn++) { 324 if (nn > 0) 325 p = _bprint_c(p, end, ' '); 326 p = _bprint_hex(p, end, data[nn], 2); 327 } 328 for ( ; nn < lineSize; nn++ ) { 329 p = _bprint_s(p, end, " "); 330 } 331 p = _bprint_s(p, end, " "); 332 333 for (nn = 0; nn < avail; nn++) { 334 int c = data[nn]; 335 336 if (c < 32 || c > 127) 337 c = '.'; 338 339 p = _bprint_c(p, end, c); 340 } 341 p = _bprint_c(p, end, '\n'); 342 343 data += avail; 344 datalen -= avail; 345 } 346 return p; 347 } 348 349 /* dump the content of a query of packet to the log */ 350 static void 351 XLOG_BYTES( const void* base, int len ) 352 { 353 char buff[1024]; 354 char* p = buff, *end = p + sizeof(buff); 355 356 p = _bprint_hexdump(p, end, base, len); 357 XLOG("%s",buff); 358 } 359 360 #else /* !DEBUG */ 361 # define XLOG(...) ((void)0) 362 # define XLOG_BYTES(a,b) ((void)0) 363 #endif 364 365 static time_t 366 _time_now( void ) 367 { 368 struct timeval tv; 369 370 gettimeofday( &tv, NULL ); 371 return tv.tv_sec; 372 } 373 374 /* reminder: the general format of a DNS packet is the following: 375 * 376 * HEADER (12 bytes) 377 * QUESTION (variable) 378 * ANSWER (variable) 379 * AUTHORITY (variable) 380 * ADDITIONNAL (variable) 381 * 382 * the HEADER is made of: 383 * 384 * ID : 16 : 16-bit unique query identification field 385 * 386 * QR : 1 : set to 0 for queries, and 1 for responses 387 * Opcode : 4 : set to 0 for queries 388 * AA : 1 : set to 0 for queries 389 * TC : 1 : truncation flag, will be set to 0 in queries 390 * RD : 1 : recursion desired 391 * 392 * RA : 1 : recursion available (0 in queries) 393 * Z : 3 : three reserved zero bits 394 * RCODE : 4 : response code (always 0=NOERROR in queries) 395 * 396 * QDCount: 16 : question count 397 * ANCount: 16 : Answer count (0 in queries) 398 * NSCount: 16: Authority Record count (0 in queries) 399 * ARCount: 16: Additionnal Record count (0 in queries) 400 * 401 * the QUESTION is made of QDCount Question Record (QRs) 402 * the ANSWER is made of ANCount RRs 403 * the AUTHORITY is made of NSCount RRs 404 * the ADDITIONNAL is made of ARCount RRs 405 * 406 * Each Question Record (QR) is made of: 407 * 408 * QNAME : variable : Query DNS NAME 409 * TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255) 410 * CLASS : 16 : class of query (IN=1) 411 * 412 * Each Resource Record (RR) is made of: 413 * 414 * NAME : variable : DNS NAME 415 * TYPE : 16 : type of query (A=1, PTR=12, MX=15, AAAA=28, ALL=255) 416 * CLASS : 16 : class of query (IN=1) 417 * TTL : 32 : seconds to cache this RR (0=none) 418 * RDLENGTH: 16 : size of RDDATA in bytes 419 * RDDATA : variable : RR data (depends on TYPE) 420 * 421 * Each QNAME contains a domain name encoded as a sequence of 'labels' 422 * terminated by a zero. Each label has the following format: 423 * 424 * LEN : 8 : lenght of label (MUST be < 64) 425 * NAME : 8*LEN : label length (must exclude dots) 426 * 427 * A value of 0 in the encoding is interpreted as the 'root' domain and 428 * terminates the encoding. So 'www.android.com' will be encoded as: 429 * 430 * <3>www<7>android<3>com<0> 431 * 432 * Where <n> represents the byte with value 'n' 433 * 434 * Each NAME reflects the QNAME of the question, but has a slightly more 435 * complex encoding in order to provide message compression. This is achieved 436 * by using a 2-byte pointer, with format: 437 * 438 * TYPE : 2 : 0b11 to indicate a pointer, 0b01 and 0b10 are reserved 439 * OFFSET : 14 : offset to another part of the DNS packet 440 * 441 * The offset is relative to the start of the DNS packet and must point 442 * A pointer terminates the encoding. 443 * 444 * The NAME can be encoded in one of the following formats: 445 * 446 * - a sequence of simple labels terminated by 0 (like QNAMEs) 447 * - a single pointer 448 * - a sequence of simple labels terminated by a pointer 449 * 450 * A pointer shall always point to either a pointer of a sequence of 451 * labels (which can themselves be terminated by either a 0 or a pointer) 452 * 453 * The expanded length of a given domain name should not exceed 255 bytes. 454 * 455 * NOTE: we don't parse the answer packets, so don't need to deal with NAME 456 * records, only QNAMEs. 457 */ 458 459 #define DNS_HEADER_SIZE 12 460 461 #define DNS_TYPE_A "\00\01" /* big-endian decimal 1 */ 462 #define DNS_TYPE_PTR "\00\014" /* big-endian decimal 12 */ 463 #define DNS_TYPE_MX "\00\017" /* big-endian decimal 15 */ 464 #define DNS_TYPE_AAAA "\00\034" /* big-endian decimal 28 */ 465 #define DNS_TYPE_ALL "\00\0377" /* big-endian decimal 255 */ 466 467 #define DNS_CLASS_IN "\00\01" /* big-endian decimal 1 */ 468 469 typedef struct { 470 const uint8_t* base; 471 const uint8_t* end; 472 const uint8_t* cursor; 473 } DnsPacket; 474 475 static void 476 _dnsPacket_init( DnsPacket* packet, const uint8_t* buff, int bufflen ) 477 { 478 packet->base = buff; 479 packet->end = buff + bufflen; 480 packet->cursor = buff; 481 } 482 483 static void 484 _dnsPacket_rewind( DnsPacket* packet ) 485 { 486 packet->cursor = packet->base; 487 } 488 489 static void 490 _dnsPacket_skip( DnsPacket* packet, int count ) 491 { 492 const uint8_t* p = packet->cursor + count; 493 494 if (p > packet->end) 495 p = packet->end; 496 497 packet->cursor = p; 498 } 499 500 static int 501 _dnsPacket_readInt16( DnsPacket* packet ) 502 { 503 const uint8_t* p = packet->cursor; 504 505 if (p+2 > packet->end) 506 return -1; 507 508 packet->cursor = p+2; 509 return (p[0]<< 8) | p[1]; 510 } 511 512 /** QUERY CHECKING 513 **/ 514 515 /* check bytes in a dns packet. returns 1 on success, 0 on failure. 516 * the cursor is only advanced in the case of success 517 */ 518 static int 519 _dnsPacket_checkBytes( DnsPacket* packet, int numBytes, const void* bytes ) 520 { 521 const uint8_t* p = packet->cursor; 522 523 if (p + numBytes > packet->end) 524 return 0; 525 526 if (memcmp(p, bytes, numBytes) != 0) 527 return 0; 528 529 packet->cursor = p + numBytes; 530 return 1; 531 } 532 533 /* parse and skip a given QNAME stored in a query packet, 534 * from the current cursor position. returns 1 on success, 535 * or 0 for malformed data. 536 */ 537 static int 538 _dnsPacket_checkQName( DnsPacket* packet ) 539 { 540 const uint8_t* p = packet->cursor; 541 const uint8_t* end = packet->end; 542 543 for (;;) { 544 int c; 545 546 if (p >= end) 547 break; 548 549 c = *p++; 550 551 if (c == 0) { 552 packet->cursor = p; 553 return 1; 554 } 555 556 /* we don't expect label compression in QNAMEs */ 557 if (c >= 64) 558 break; 559 560 p += c; 561 /* we rely on the bound check at the start 562 * of the loop here */ 563 } 564 /* malformed data */ 565 XLOG("malformed QNAME"); 566 return 0; 567 } 568 569 /* parse and skip a given QR stored in a packet. 570 * returns 1 on success, and 0 on failure 571 */ 572 static int 573 _dnsPacket_checkQR( DnsPacket* packet ) 574 { 575 int len; 576 577 if (!_dnsPacket_checkQName(packet)) 578 return 0; 579 580 /* TYPE must be one of the things we support */ 581 if (!_dnsPacket_checkBytes(packet, 2, DNS_TYPE_A) && 582 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_PTR) && 583 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_MX) && 584 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_AAAA) && 585 !_dnsPacket_checkBytes(packet, 2, DNS_TYPE_ALL)) 586 { 587 XLOG("unsupported TYPE"); 588 return 0; 589 } 590 /* CLASS must be IN */ 591 if (!_dnsPacket_checkBytes(packet, 2, DNS_CLASS_IN)) { 592 XLOG("unsupported CLASS"); 593 return 0; 594 } 595 596 return 1; 597 } 598 599 /* check the header of a DNS Query packet, return 1 if it is one 600 * type of query we can cache, or 0 otherwise 601 */ 602 static int 603 _dnsPacket_checkQuery( DnsPacket* packet ) 604 { 605 const uint8_t* p = packet->base; 606 int qdCount, anCount, dnCount, arCount; 607 608 if (p + DNS_HEADER_SIZE > packet->end) { 609 XLOG("query packet too small"); 610 return 0; 611 } 612 613 /* QR must be set to 0, opcode must be 0 and AA must be 0 */ 614 /* RA, Z, and RCODE must be 0 */ 615 if ((p[2] & 0xFC) != 0 || p[3] != 0) { 616 XLOG("query packet flags unsupported"); 617 return 0; 618 } 619 620 /* Note that we ignore the TC and RD bits here for the 621 * following reasons: 622 * 623 * - there is no point for a query packet sent to a server 624 * to have the TC bit set, but the implementation might 625 * set the bit in the query buffer for its own needs 626 * between a _resolv_cache_lookup and a 627 * _resolv_cache_add. We should not freak out if this 628 * is the case. 629 * 630 * - we consider that the result from a RD=0 or a RD=1 631 * query might be different, hence that the RD bit 632 * should be used to differentiate cached result. 633 * 634 * this implies that RD is checked when hashing or 635 * comparing query packets, but not TC 636 */ 637 638 /* ANCOUNT, DNCOUNT and ARCOUNT must be 0 */ 639 qdCount = (p[4] << 8) | p[5]; 640 anCount = (p[6] << 8) | p[7]; 641 dnCount = (p[8] << 8) | p[9]; 642 arCount = (p[10]<< 8) | p[11]; 643 644 if (anCount != 0 || dnCount != 0 || arCount != 0) { 645 XLOG("query packet contains non-query records"); 646 return 0; 647 } 648 649 if (qdCount == 0) { 650 XLOG("query packet doesn't contain query record"); 651 return 0; 652 } 653 654 /* Check QDCOUNT QRs */ 655 packet->cursor = p + DNS_HEADER_SIZE; 656 657 for (;qdCount > 0; qdCount--) 658 if (!_dnsPacket_checkQR(packet)) 659 return 0; 660 661 return 1; 662 } 663 664 /** QUERY DEBUGGING 665 **/ 666 #if DEBUG 667 static char* 668 _dnsPacket_bprintQName(DnsPacket* packet, char* bp, char* bend) 669 { 670 const uint8_t* p = packet->cursor; 671 const uint8_t* end = packet->end; 672 int first = 1; 673 674 for (;;) { 675 int c; 676 677 if (p >= end) 678 break; 679 680 c = *p++; 681 682 if (c == 0) { 683 packet->cursor = p; 684 return bp; 685 } 686 687 /* we don't expect label compression in QNAMEs */ 688 if (c >= 64) 689 break; 690 691 if (first) 692 first = 0; 693 else 694 bp = _bprint_c(bp, bend, '.'); 695 696 bp = _bprint_b(bp, bend, (const char*)p, c); 697 698 p += c; 699 /* we rely on the bound check at the start 700 * of the loop here */ 701 } 702 /* malformed data */ 703 bp = _bprint_s(bp, bend, "<MALFORMED>"); 704 return bp; 705 } 706 707 static char* 708 _dnsPacket_bprintQR(DnsPacket* packet, char* p, char* end) 709 { 710 #define QQ(x) { DNS_TYPE_##x, #x } 711 static const struct { 712 const char* typeBytes; 713 const char* typeString; 714 } qTypes[] = 715 { 716 QQ(A), QQ(PTR), QQ(MX), QQ(AAAA), QQ(ALL), 717 { NULL, NULL } 718 }; 719 int nn; 720 const char* typeString = NULL; 721 722 /* dump QNAME */ 723 p = _dnsPacket_bprintQName(packet, p, end); 724 725 /* dump TYPE */ 726 p = _bprint_s(p, end, " ("); 727 728 for (nn = 0; qTypes[nn].typeBytes != NULL; nn++) { 729 if (_dnsPacket_checkBytes(packet, 2, qTypes[nn].typeBytes)) { 730 typeString = qTypes[nn].typeString; 731 break; 732 } 733 } 734 735 if (typeString != NULL) 736 p = _bprint_s(p, end, typeString); 737 else { 738 int typeCode = _dnsPacket_readInt16(packet); 739 p = _bprint(p, end, "UNKNOWN-%d", typeCode); 740 } 741 742 p = _bprint_c(p, end, ')'); 743 744 /* skip CLASS */ 745 _dnsPacket_skip(packet, 2); 746 return p; 747 } 748 749 /* this function assumes the packet has already been checked */ 750 static char* 751 _dnsPacket_bprintQuery( DnsPacket* packet, char* p, char* end ) 752 { 753 int qdCount; 754 755 if (packet->base[2] & 0x1) { 756 p = _bprint_s(p, end, "RECURSIVE "); 757 } 758 759 _dnsPacket_skip(packet, 4); 760 qdCount = _dnsPacket_readInt16(packet); 761 _dnsPacket_skip(packet, 6); 762 763 for ( ; qdCount > 0; qdCount-- ) { 764 p = _dnsPacket_bprintQR(packet, p, end); 765 } 766 return p; 767 } 768 #endif 769 770 771 /** QUERY HASHING SUPPORT 772 ** 773 ** THE FOLLOWING CODE ASSUMES THAT THE INPUT PACKET HAS ALREADY 774 ** BEEN SUCCESFULLY CHECKED. 775 **/ 776 777 /* use 32-bit FNV hash function */ 778 #define FNV_MULT 16777619U 779 #define FNV_BASIS 2166136261U 780 781 static unsigned 782 _dnsPacket_hashBytes( DnsPacket* packet, int numBytes, unsigned hash ) 783 { 784 const uint8_t* p = packet->cursor; 785 const uint8_t* end = packet->end; 786 787 while (numBytes > 0 && p < end) { 788 hash = hash*FNV_MULT ^ *p++; 789 } 790 packet->cursor = p; 791 return hash; 792 } 793 794 795 static unsigned 796 _dnsPacket_hashQName( DnsPacket* packet, unsigned hash ) 797 { 798 const uint8_t* p = packet->cursor; 799 const uint8_t* end = packet->end; 800 801 for (;;) { 802 int c; 803 804 if (p >= end) { /* should not happen */ 805 XLOG("%s: INTERNAL_ERROR: read-overflow !!\n", __FUNCTION__); 806 break; 807 } 808 809 c = *p++; 810 811 if (c == 0) 812 break; 813 814 if (c >= 64) { 815 XLOG("%s: INTERNAL_ERROR: malformed domain !!\n", __FUNCTION__); 816 break; 817 } 818 if (p + c >= end) { 819 XLOG("%s: INTERNAL_ERROR: simple label read-overflow !!\n", 820 __FUNCTION__); 821 break; 822 } 823 while (c > 0) { 824 hash = hash*FNV_MULT ^ *p++; 825 c -= 1; 826 } 827 } 828 packet->cursor = p; 829 return hash; 830 } 831 832 static unsigned 833 _dnsPacket_hashQR( DnsPacket* packet, unsigned hash ) 834 { 835 int len; 836 837 hash = _dnsPacket_hashQName(packet, hash); 838 hash = _dnsPacket_hashBytes(packet, 4, hash); /* TYPE and CLASS */ 839 return hash; 840 } 841 842 static unsigned 843 _dnsPacket_hashQuery( DnsPacket* packet ) 844 { 845 unsigned hash = FNV_BASIS; 846 int count; 847 _dnsPacket_rewind(packet); 848 849 /* we ignore the TC bit for reasons explained in 850 * _dnsPacket_checkQuery(). 851 * 852 * however we hash the RD bit to differentiate 853 * between answers for recursive and non-recursive 854 * queries. 855 */ 856 hash = hash*FNV_MULT ^ (packet->base[2] & 1); 857 858 /* assume: other flags are 0 */ 859 _dnsPacket_skip(packet, 4); 860 861 /* read QDCOUNT */ 862 count = _dnsPacket_readInt16(packet); 863 864 /* assume: ANcount, NScount, ARcount are 0 */ 865 _dnsPacket_skip(packet, 6); 866 867 /* hash QDCOUNT QRs */ 868 for ( ; count > 0; count-- ) 869 hash = _dnsPacket_hashQR(packet, hash); 870 871 return hash; 872 } 873 874 875 /** QUERY COMPARISON 876 ** 877 ** THE FOLLOWING CODE ASSUMES THAT THE INPUT PACKETS HAVE ALREADY 878 ** BEEN SUCCESFULLY CHECKED. 879 **/ 880 881 static int 882 _dnsPacket_isEqualDomainName( DnsPacket* pack1, DnsPacket* pack2 ) 883 { 884 const uint8_t* p1 = pack1->cursor; 885 const uint8_t* end1 = pack1->end; 886 const uint8_t* p2 = pack2->cursor; 887 const uint8_t* end2 = pack2->end; 888 889 for (;;) { 890 int c1, c2; 891 892 if (p1 >= end1 || p2 >= end2) { 893 XLOG("%s: INTERNAL_ERROR: read-overflow !!\n", __FUNCTION__); 894 break; 895 } 896 c1 = *p1++; 897 c2 = *p2++; 898 if (c1 != c2) 899 break; 900 901 if (c1 == 0) { 902 pack1->cursor = p1; 903 pack2->cursor = p2; 904 return 1; 905 } 906 if (c1 >= 64) { 907 XLOG("%s: INTERNAL_ERROR: malformed domain !!\n", __FUNCTION__); 908 break; 909 } 910 if ((p1+c1 > end1) || (p2+c1 > end2)) { 911 XLOG("%s: INTERNAL_ERROR: simple label read-overflow !!\n", 912 __FUNCTION__); 913 break; 914 } 915 if (memcmp(p1, p2, c1) != 0) 916 break; 917 p1 += c1; 918 p2 += c1; 919 /* we rely on the bound checks at the start of the loop */ 920 } 921 /* not the same, or one is malformed */ 922 XLOG("different DN"); 923 return 0; 924 } 925 926 static int 927 _dnsPacket_isEqualBytes( DnsPacket* pack1, DnsPacket* pack2, int numBytes ) 928 { 929 const uint8_t* p1 = pack1->cursor; 930 const uint8_t* p2 = pack2->cursor; 931 932 if ( p1 + numBytes > pack1->end || p2 + numBytes > pack2->end ) 933 return 0; 934 935 if ( memcmp(p1, p2, numBytes) != 0 ) 936 return 0; 937 938 pack1->cursor += numBytes; 939 pack2->cursor += numBytes; 940 return 1; 941 } 942 943 static int 944 _dnsPacket_isEqualQR( DnsPacket* pack1, DnsPacket* pack2 ) 945 { 946 /* compare domain name encoding + TYPE + CLASS */ 947 if ( !_dnsPacket_isEqualDomainName(pack1, pack2) || 948 !_dnsPacket_isEqualBytes(pack1, pack2, 2+2) ) 949 return 0; 950 951 return 1; 952 } 953 954 static int 955 _dnsPacket_isEqualQuery( DnsPacket* pack1, DnsPacket* pack2 ) 956 { 957 int count1, count2; 958 959 /* compare the headers, ignore most fields */ 960 _dnsPacket_rewind(pack1); 961 _dnsPacket_rewind(pack2); 962 963 /* compare RD, ignore TC, see comment in _dnsPacket_checkQuery */ 964 if ((pack1->base[2] & 1) != (pack2->base[2] & 1)) { 965 XLOG("different RD"); 966 return 0; 967 } 968 969 /* assume: other flags are all 0 */ 970 _dnsPacket_skip(pack1, 4); 971 _dnsPacket_skip(pack2, 4); 972 973 /* compare QDCOUNT */ 974 count1 = _dnsPacket_readInt16(pack1); 975 count2 = _dnsPacket_readInt16(pack2); 976 if (count1 != count2 || count1 < 0) { 977 XLOG("different QDCOUNT"); 978 return 0; 979 } 980 981 /* assume: ANcount, NScount and ARcount are all 0 */ 982 _dnsPacket_skip(pack1, 6); 983 _dnsPacket_skip(pack2, 6); 984 985 /* compare the QDCOUNT QRs */ 986 for ( ; count1 > 0; count1-- ) { 987 if (!_dnsPacket_isEqualQR(pack1, pack2)) { 988 XLOG("different QR"); 989 return 0; 990 } 991 } 992 return 1; 993 } 994 995 /****************************************************************************/ 996 /****************************************************************************/ 997 /***** *****/ 998 /***** *****/ 999 /***** *****/ 1000 /****************************************************************************/ 1001 /****************************************************************************/ 1002 1003 /* cache entry. for simplicity, 'hash' and 'hlink' are inlined in this 1004 * structure though they are conceptually part of the hash table. 1005 * 1006 * similarly, mru_next and mru_prev are part of the global MRU list 1007 */ 1008 typedef struct Entry { 1009 unsigned int hash; /* hash value */ 1010 struct Entry* hlink; /* next in collision chain */ 1011 struct Entry* mru_prev; 1012 struct Entry* mru_next; 1013 1014 const uint8_t* query; 1015 int querylen; 1016 const uint8_t* answer; 1017 int answerlen; 1018 time_t expires; /* time_t when the entry isn't valid any more */ 1019 int id; /* for debugging purpose */ 1020 } Entry; 1021 1022 /** 1023 * Parse the answer records and find the smallest 1024 * TTL among the answer records. 1025 * 1026 * The returned TTL is the number of seconds to 1027 * keep the answer in the cache. 1028 * 1029 * In case of parse error zero (0) is returned which 1030 * indicates that the answer shall not be cached. 1031 */ 1032 static u_long 1033 answer_getTTL(const void* answer, int answerlen) 1034 { 1035 ns_msg handle; 1036 int ancount, n; 1037 u_long result, ttl; 1038 ns_rr rr; 1039 1040 result = 0; 1041 if (ns_initparse(answer, answerlen, &handle) >= 0) { 1042 // get number of answer records 1043 ancount = ns_msg_count(handle, ns_s_an); 1044 for (n = 0; n < ancount; n++) { 1045 if (ns_parserr(&handle, ns_s_an, n, &rr) == 0) { 1046 ttl = ns_rr_ttl(rr); 1047 if (n == 0 || ttl < result) { 1048 result = ttl; 1049 } 1050 } else { 1051 XLOG("ns_parserr failed ancount no = %d. errno = %s\n", n, strerror(errno)); 1052 } 1053 } 1054 } else { 1055 XLOG("ns_parserr failed. %s\n", strerror(errno)); 1056 } 1057 1058 XLOG("TTL = %d\n", result); 1059 1060 return result; 1061 } 1062 1063 static void 1064 entry_free( Entry* e ) 1065 { 1066 /* everything is allocated in a single memory block */ 1067 if (e) { 1068 free(e); 1069 } 1070 } 1071 1072 static __inline__ void 1073 entry_mru_remove( Entry* e ) 1074 { 1075 e->mru_prev->mru_next = e->mru_next; 1076 e->mru_next->mru_prev = e->mru_prev; 1077 } 1078 1079 static __inline__ void 1080 entry_mru_add( Entry* e, Entry* list ) 1081 { 1082 Entry* first = list->mru_next; 1083 1084 e->mru_next = first; 1085 e->mru_prev = list; 1086 1087 list->mru_next = e; 1088 first->mru_prev = e; 1089 } 1090 1091 /* compute the hash of a given entry, this is a hash of most 1092 * data in the query (key) */ 1093 static unsigned 1094 entry_hash( const Entry* e ) 1095 { 1096 DnsPacket pack[1]; 1097 1098 _dnsPacket_init(pack, e->query, e->querylen); 1099 return _dnsPacket_hashQuery(pack); 1100 } 1101 1102 /* initialize an Entry as a search key, this also checks the input query packet 1103 * returns 1 on success, or 0 in case of unsupported/malformed data */ 1104 static int 1105 entry_init_key( Entry* e, const void* query, int querylen ) 1106 { 1107 DnsPacket pack[1]; 1108 1109 memset(e, 0, sizeof(*e)); 1110 1111 e->query = query; 1112 e->querylen = querylen; 1113 e->hash = entry_hash(e); 1114 1115 _dnsPacket_init(pack, query, querylen); 1116 1117 return _dnsPacket_checkQuery(pack); 1118 } 1119 1120 /* allocate a new entry as a cache node */ 1121 static Entry* 1122 entry_alloc( const Entry* init, const void* answer, int answerlen ) 1123 { 1124 Entry* e; 1125 int size; 1126 1127 size = sizeof(*e) + init->querylen + answerlen; 1128 e = calloc(size, 1); 1129 if (e == NULL) 1130 return e; 1131 1132 e->hash = init->hash; 1133 e->query = (const uint8_t*)(e+1); 1134 e->querylen = init->querylen; 1135 1136 memcpy( (char*)e->query, init->query, e->querylen ); 1137 1138 e->answer = e->query + e->querylen; 1139 e->answerlen = answerlen; 1140 1141 memcpy( (char*)e->answer, answer, e->answerlen ); 1142 1143 return e; 1144 } 1145 1146 static int 1147 entry_equals( const Entry* e1, const Entry* e2 ) 1148 { 1149 DnsPacket pack1[1], pack2[1]; 1150 1151 if (e1->querylen != e2->querylen) { 1152 return 0; 1153 } 1154 _dnsPacket_init(pack1, e1->query, e1->querylen); 1155 _dnsPacket_init(pack2, e2->query, e2->querylen); 1156 1157 return _dnsPacket_isEqualQuery(pack1, pack2); 1158 } 1159 1160 /****************************************************************************/ 1161 /****************************************************************************/ 1162 /***** *****/ 1163 /***** *****/ 1164 /***** *****/ 1165 /****************************************************************************/ 1166 /****************************************************************************/ 1167 1168 /* We use a simple hash table with external collision lists 1169 * for simplicity, the hash-table fields 'hash' and 'hlink' are 1170 * inlined in the Entry structure. 1171 */ 1172 1173 /* Maximum time for a thread to wait for an pending request */ 1174 #define PENDING_REQUEST_TIMEOUT 20; 1175 1176 typedef struct pending_req_info { 1177 unsigned int hash; 1178 pthread_cond_t cond; 1179 struct pending_req_info* next; 1180 } PendingReqInfo; 1181 1182 typedef struct resolv_cache { 1183 int max_entries; 1184 int num_entries; 1185 Entry mru_list; 1186 pthread_mutex_t lock; 1187 unsigned generation; 1188 int last_id; 1189 Entry* entries; 1190 PendingReqInfo pending_requests; 1191 } Cache; 1192 1193 typedef struct resolv_cache_info { 1194 char ifname[IF_NAMESIZE + 1]; 1195 struct in_addr ifaddr; 1196 Cache* cache; 1197 struct resolv_cache_info* next; 1198 char* nameservers[MAXNS +1]; 1199 struct addrinfo* nsaddrinfo[MAXNS + 1]; 1200 } CacheInfo; 1201 1202 #define HTABLE_VALID(x) ((x) != NULL && (x) != HTABLE_DELETED) 1203 1204 static void 1205 _cache_flush_pending_requests_locked( struct resolv_cache* cache ) 1206 { 1207 struct pending_req_info *ri, *tmp; 1208 if (cache) { 1209 ri = cache->pending_requests.next; 1210 1211 while (ri) { 1212 tmp = ri; 1213 ri = ri->next; 1214 pthread_cond_broadcast(&tmp->cond); 1215 1216 pthread_cond_destroy(&tmp->cond); 1217 free(tmp); 1218 } 1219 1220 cache->pending_requests.next = NULL; 1221 } 1222 } 1223 1224 /* return 0 if no pending request is found matching the key 1225 * if a matching request is found the calling thread will wait 1226 * and return 1 when released */ 1227 static int 1228 _cache_check_pending_request_locked( struct resolv_cache* cache, Entry* key ) 1229 { 1230 struct pending_req_info *ri, *prev; 1231 int exist = 0; 1232 1233 if (cache && key) { 1234 ri = cache->pending_requests.next; 1235 prev = &cache->pending_requests; 1236 while (ri) { 1237 if (ri->hash == key->hash) { 1238 exist = 1; 1239 break; 1240 } 1241 prev = ri; 1242 ri = ri->next; 1243 } 1244 1245 if (!exist) { 1246 ri = calloc(1, sizeof(struct pending_req_info)); 1247 if (ri) { 1248 ri->hash = key->hash; 1249 pthread_cond_init(&ri->cond, NULL); 1250 prev->next = ri; 1251 } 1252 } else { 1253 struct timespec ts = {0,0}; 1254 ts.tv_sec = _time_now() + PENDING_REQUEST_TIMEOUT; 1255 int rv = pthread_cond_timedwait(&ri->cond, &cache->lock, &ts); 1256 } 1257 } 1258 1259 return exist; 1260 } 1261 1262 /* notify any waiting thread that waiting on a request 1263 * matching the key has been added to the cache */ 1264 static void 1265 _cache_notify_waiting_tid_locked( struct resolv_cache* cache, Entry* key ) 1266 { 1267 struct pending_req_info *ri, *prev; 1268 1269 if (cache && key) { 1270 ri = cache->pending_requests.next; 1271 prev = &cache->pending_requests; 1272 while (ri) { 1273 if (ri->hash == key->hash) { 1274 pthread_cond_broadcast(&ri->cond); 1275 break; 1276 } 1277 prev = ri; 1278 ri = ri->next; 1279 } 1280 1281 // remove item from list and destroy 1282 if (ri) { 1283 prev->next = ri->next; 1284 pthread_cond_destroy(&ri->cond); 1285 free(ri); 1286 } 1287 } 1288 } 1289 1290 /* notify the cache that the query failed */ 1291 void 1292 _resolv_cache_query_failed( struct resolv_cache* cache, 1293 const void* query, 1294 int querylen) 1295 { 1296 Entry key[1]; 1297 1298 if (cache && entry_init_key(key, query, querylen)) { 1299 pthread_mutex_lock(&cache->lock); 1300 _cache_notify_waiting_tid_locked(cache, key); 1301 pthread_mutex_unlock(&cache->lock); 1302 } 1303 } 1304 1305 static void 1306 _cache_flush_locked( Cache* cache ) 1307 { 1308 int nn; 1309 time_t now = _time_now(); 1310 1311 for (nn = 0; nn < cache->max_entries; nn++) 1312 { 1313 Entry** pnode = (Entry**) &cache->entries[nn]; 1314 1315 while (*pnode != NULL) { 1316 Entry* node = *pnode; 1317 *pnode = node->hlink; 1318 entry_free(node); 1319 } 1320 } 1321 1322 // flush pending request 1323 _cache_flush_pending_requests_locked(cache); 1324 1325 cache->mru_list.mru_next = cache->mru_list.mru_prev = &cache->mru_list; 1326 cache->num_entries = 0; 1327 cache->last_id = 0; 1328 1329 XLOG("*************************\n" 1330 "*** DNS CACHE FLUSHED ***\n" 1331 "*************************"); 1332 } 1333 1334 /* Return max number of entries allowed in the cache, 1335 * i.e. cache size. The cache size is either defined 1336 * by system property ro.net.dns_cache_size or by 1337 * CONFIG_MAX_ENTRIES if system property not set 1338 * or set to invalid value. */ 1339 static int 1340 _res_cache_get_max_entries( void ) 1341 { 1342 int result = -1; 1343 char cache_size[PROP_VALUE_MAX]; 1344 1345 const char* cache_mode = getenv("ANDROID_DNS_MODE"); 1346 1347 if (cache_mode == NULL || strcmp(cache_mode, "local") != 0) { 1348 // Don't use the cache in local mode. This is used by the 1349 // proxy itself. 1350 // TODO - change this to 0 when all dns stuff uses proxy (5918973) 1351 XLOG("setup cache for non-cache process. size=1"); 1352 return 1; 1353 } 1354 1355 if (__system_property_get(DNS_CACHE_SIZE_PROP_NAME, cache_size) > 0) { 1356 result = atoi(cache_size); 1357 } 1358 1359 // ro.net.dns_cache_size not set or set to negative value 1360 if (result <= 0) { 1361 result = CONFIG_MAX_ENTRIES; 1362 } 1363 1364 XLOG("cache size: %d", result); 1365 return result; 1366 } 1367 1368 static struct resolv_cache* 1369 _resolv_cache_create( void ) 1370 { 1371 struct resolv_cache* cache; 1372 1373 cache = calloc(sizeof(*cache), 1); 1374 if (cache) { 1375 cache->max_entries = _res_cache_get_max_entries(); 1376 cache->entries = calloc(sizeof(*cache->entries), cache->max_entries); 1377 if (cache->entries) { 1378 cache->generation = ~0U; 1379 pthread_mutex_init( &cache->lock, NULL ); 1380 cache->mru_list.mru_prev = cache->mru_list.mru_next = &cache->mru_list; 1381 XLOG("%s: cache created\n", __FUNCTION__); 1382 } else { 1383 free(cache); 1384 cache = NULL; 1385 } 1386 } 1387 return cache; 1388 } 1389 1390 1391 #if DEBUG 1392 static void 1393 _dump_query( const uint8_t* query, int querylen ) 1394 { 1395 char temp[256], *p=temp, *end=p+sizeof(temp); 1396 DnsPacket pack[1]; 1397 1398 _dnsPacket_init(pack, query, querylen); 1399 p = _dnsPacket_bprintQuery(pack, p, end); 1400 XLOG("QUERY: %s", temp); 1401 } 1402 1403 static void 1404 _cache_dump_mru( Cache* cache ) 1405 { 1406 char temp[512], *p=temp, *end=p+sizeof(temp); 1407 Entry* e; 1408 1409 p = _bprint(temp, end, "MRU LIST (%2d): ", cache->num_entries); 1410 for (e = cache->mru_list.mru_next; e != &cache->mru_list; e = e->mru_next) 1411 p = _bprint(p, end, " %d", e->id); 1412 1413 XLOG("%s", temp); 1414 } 1415 1416 static void 1417 _dump_answer(const void* answer, int answerlen) 1418 { 1419 res_state statep; 1420 FILE* fp; 1421 char* buf; 1422 int fileLen; 1423 1424 fp = fopen("/data/reslog.txt", "w+"); 1425 if (fp != NULL) { 1426 statep = __res_get_state(); 1427 1428 res_pquery(statep, answer, answerlen, fp); 1429 1430 //Get file length 1431 fseek(fp, 0, SEEK_END); 1432 fileLen=ftell(fp); 1433 fseek(fp, 0, SEEK_SET); 1434 buf = (char *)malloc(fileLen+1); 1435 if (buf != NULL) { 1436 //Read file contents into buffer 1437 fread(buf, fileLen, 1, fp); 1438 XLOG("%s\n", buf); 1439 free(buf); 1440 } 1441 fclose(fp); 1442 remove("/data/reslog.txt"); 1443 } 1444 else { 1445 XLOG("_dump_answer: can't open file\n"); 1446 } 1447 } 1448 #endif 1449 1450 #if DEBUG 1451 # define XLOG_QUERY(q,len) _dump_query((q), (len)) 1452 # define XLOG_ANSWER(a, len) _dump_answer((a), (len)) 1453 #else 1454 # define XLOG_QUERY(q,len) ((void)0) 1455 # define XLOG_ANSWER(a,len) ((void)0) 1456 #endif 1457 1458 /* This function tries to find a key within the hash table 1459 * In case of success, it will return a *pointer* to the hashed key. 1460 * In case of failure, it will return a *pointer* to NULL 1461 * 1462 * So, the caller must check '*result' to check for success/failure. 1463 * 1464 * The main idea is that the result can later be used directly in 1465 * calls to _resolv_cache_add or _resolv_cache_remove as the 'lookup' 1466 * parameter. This makes the code simpler and avoids re-searching 1467 * for the key position in the htable. 1468 * 1469 * The result of a lookup_p is only valid until you alter the hash 1470 * table. 1471 */ 1472 static Entry** 1473 _cache_lookup_p( Cache* cache, 1474 Entry* key ) 1475 { 1476 int index = key->hash % cache->max_entries; 1477 Entry** pnode = (Entry**) &cache->entries[ index ]; 1478 1479 while (*pnode != NULL) { 1480 Entry* node = *pnode; 1481 1482 if (node == NULL) 1483 break; 1484 1485 if (node->hash == key->hash && entry_equals(node, key)) 1486 break; 1487 1488 pnode = &node->hlink; 1489 } 1490 return pnode; 1491 } 1492 1493 /* Add a new entry to the hash table. 'lookup' must be the 1494 * result of an immediate previous failed _lookup_p() call 1495 * (i.e. with *lookup == NULL), and 'e' is the pointer to the 1496 * newly created entry 1497 */ 1498 static void 1499 _cache_add_p( Cache* cache, 1500 Entry** lookup, 1501 Entry* e ) 1502 { 1503 *lookup = e; 1504 e->id = ++cache->last_id; 1505 entry_mru_add(e, &cache->mru_list); 1506 cache->num_entries += 1; 1507 1508 XLOG("%s: entry %d added (count=%d)", __FUNCTION__, 1509 e->id, cache->num_entries); 1510 } 1511 1512 /* Remove an existing entry from the hash table, 1513 * 'lookup' must be the result of an immediate previous 1514 * and succesful _lookup_p() call. 1515 */ 1516 static void 1517 _cache_remove_p( Cache* cache, 1518 Entry** lookup ) 1519 { 1520 Entry* e = *lookup; 1521 1522 XLOG("%s: entry %d removed (count=%d)", __FUNCTION__, 1523 e->id, cache->num_entries-1); 1524 1525 entry_mru_remove(e); 1526 *lookup = e->hlink; 1527 entry_free(e); 1528 cache->num_entries -= 1; 1529 } 1530 1531 /* Remove the oldest entry from the hash table. 1532 */ 1533 static void 1534 _cache_remove_oldest( Cache* cache ) 1535 { 1536 Entry* oldest = cache->mru_list.mru_prev; 1537 Entry** lookup = _cache_lookup_p(cache, oldest); 1538 1539 if (*lookup == NULL) { /* should not happen */ 1540 XLOG("%s: OLDEST NOT IN HTABLE ?", __FUNCTION__); 1541 return; 1542 } 1543 if (DEBUG) { 1544 XLOG("Cache full - removing oldest"); 1545 XLOG_QUERY(oldest->query, oldest->querylen); 1546 } 1547 _cache_remove_p(cache, lookup); 1548 } 1549 1550 /* Remove all expired entries from the hash table. 1551 */ 1552 static void _cache_remove_expired(Cache* cache) { 1553 Entry* e; 1554 time_t now = _time_now(); 1555 1556 for (e = cache->mru_list.mru_next; e != &cache->mru_list;) { 1557 // Entry is old, remove 1558 if (now >= e->expires) { 1559 Entry** lookup = _cache_lookup_p(cache, e); 1560 if (*lookup == NULL) { /* should not happen */ 1561 XLOG("%s: ENTRY NOT IN HTABLE ?", __FUNCTION__); 1562 return; 1563 } 1564 e = e->mru_next; 1565 _cache_remove_p(cache, lookup); 1566 } else { 1567 e = e->mru_next; 1568 } 1569 } 1570 } 1571 1572 ResolvCacheStatus 1573 _resolv_cache_lookup( struct resolv_cache* cache, 1574 const void* query, 1575 int querylen, 1576 void* answer, 1577 int answersize, 1578 int *answerlen ) 1579 { 1580 DnsPacket pack[1]; 1581 Entry key[1]; 1582 int index; 1583 Entry** lookup; 1584 Entry* e; 1585 time_t now; 1586 1587 ResolvCacheStatus result = RESOLV_CACHE_NOTFOUND; 1588 1589 XLOG("%s: lookup", __FUNCTION__); 1590 XLOG_QUERY(query, querylen); 1591 1592 /* we don't cache malformed queries */ 1593 if (!entry_init_key(key, query, querylen)) { 1594 XLOG("%s: unsupported query", __FUNCTION__); 1595 return RESOLV_CACHE_UNSUPPORTED; 1596 } 1597 /* lookup cache */ 1598 pthread_mutex_lock( &cache->lock ); 1599 1600 /* see the description of _lookup_p to understand this. 1601 * the function always return a non-NULL pointer. 1602 */ 1603 lookup = _cache_lookup_p(cache, key); 1604 e = *lookup; 1605 1606 if (e == NULL) { 1607 XLOG( "NOT IN CACHE"); 1608 // calling thread will wait if an outstanding request is found 1609 // that matching this query 1610 if (!_cache_check_pending_request_locked(cache, key)) { 1611 goto Exit; 1612 } else { 1613 lookup = _cache_lookup_p(cache, key); 1614 e = *lookup; 1615 if (e == NULL) { 1616 goto Exit; 1617 } 1618 } 1619 } 1620 1621 now = _time_now(); 1622 1623 /* remove stale entries here */ 1624 if (now >= e->expires) { 1625 XLOG( " NOT IN CACHE (STALE ENTRY %p DISCARDED)", *lookup ); 1626 XLOG_QUERY(e->query, e->querylen); 1627 _cache_remove_p(cache, lookup); 1628 goto Exit; 1629 } 1630 1631 *answerlen = e->answerlen; 1632 if (e->answerlen > answersize) { 1633 /* NOTE: we return UNSUPPORTED if the answer buffer is too short */ 1634 result = RESOLV_CACHE_UNSUPPORTED; 1635 XLOG(" ANSWER TOO LONG"); 1636 goto Exit; 1637 } 1638 1639 memcpy( answer, e->answer, e->answerlen ); 1640 1641 /* bump up this entry to the top of the MRU list */ 1642 if (e != cache->mru_list.mru_next) { 1643 entry_mru_remove( e ); 1644 entry_mru_add( e, &cache->mru_list ); 1645 } 1646 1647 XLOG( "FOUND IN CACHE entry=%p", e ); 1648 result = RESOLV_CACHE_FOUND; 1649 1650 Exit: 1651 pthread_mutex_unlock( &cache->lock ); 1652 return result; 1653 } 1654 1655 1656 void 1657 _resolv_cache_add( struct resolv_cache* cache, 1658 const void* query, 1659 int querylen, 1660 const void* answer, 1661 int answerlen ) 1662 { 1663 Entry key[1]; 1664 Entry* e; 1665 Entry** lookup; 1666 u_long ttl; 1667 1668 /* don't assume that the query has already been cached 1669 */ 1670 if (!entry_init_key( key, query, querylen )) { 1671 XLOG( "%s: passed invalid query ?", __FUNCTION__); 1672 return; 1673 } 1674 1675 pthread_mutex_lock( &cache->lock ); 1676 1677 XLOG( "%s: query:", __FUNCTION__ ); 1678 XLOG_QUERY(query,querylen); 1679 XLOG_ANSWER(answer, answerlen); 1680 #if DEBUG_DATA 1681 XLOG( "answer:"); 1682 XLOG_BYTES(answer,answerlen); 1683 #endif 1684 1685 lookup = _cache_lookup_p(cache, key); 1686 e = *lookup; 1687 1688 if (e != NULL) { /* should not happen */ 1689 XLOG("%s: ALREADY IN CACHE (%p) ? IGNORING ADD", 1690 __FUNCTION__, e); 1691 goto Exit; 1692 } 1693 1694 if (cache->num_entries >= cache->max_entries) { 1695 _cache_remove_expired(cache); 1696 if (cache->num_entries >= cache->max_entries) { 1697 _cache_remove_oldest(cache); 1698 } 1699 /* need to lookup again */ 1700 lookup = _cache_lookup_p(cache, key); 1701 e = *lookup; 1702 if (e != NULL) { 1703 XLOG("%s: ALREADY IN CACHE (%p) ? IGNORING ADD", 1704 __FUNCTION__, e); 1705 goto Exit; 1706 } 1707 } 1708 1709 ttl = answer_getTTL(answer, answerlen); 1710 if (ttl > 0) { 1711 e = entry_alloc(key, answer, answerlen); 1712 if (e != NULL) { 1713 e->expires = ttl + _time_now(); 1714 _cache_add_p(cache, lookup, e); 1715 } 1716 } 1717 #if DEBUG 1718 _cache_dump_mru(cache); 1719 #endif 1720 Exit: 1721 _cache_notify_waiting_tid_locked(cache, key); 1722 pthread_mutex_unlock( &cache->lock ); 1723 } 1724 1725 /****************************************************************************/ 1726 /****************************************************************************/ 1727 /***** *****/ 1728 /***** *****/ 1729 /***** *****/ 1730 /****************************************************************************/ 1731 /****************************************************************************/ 1732 1733 static pthread_once_t _res_cache_once; 1734 1735 // Head of the list of caches. Protected by _res_cache_list_lock. 1736 static struct resolv_cache_info _res_cache_list; 1737 1738 // name of the current default inteface 1739 static char _res_default_ifname[IF_NAMESIZE + 1]; 1740 1741 // lock protecting everything in the _resolve_cache_info structs (next ptr, etc) 1742 static pthread_mutex_t _res_cache_list_lock; 1743 1744 1745 /* lookup the default interface name */ 1746 static char *_get_default_iface_locked(); 1747 /* insert resolv_cache_info into the list of resolv_cache_infos */ 1748 static void _insert_cache_info_locked(struct resolv_cache_info* cache_info); 1749 /* creates a resolv_cache_info */ 1750 static struct resolv_cache_info* _create_cache_info( void ); 1751 /* gets cache associated with an interface name, or NULL if none exists */ 1752 static struct resolv_cache* _find_named_cache_locked(const char* ifname); 1753 /* gets a resolv_cache_info associated with an interface name, or NULL if not found */ 1754 static struct resolv_cache_info* _find_cache_info_locked(const char* ifname); 1755 /* free dns name server list of a resolv_cache_info structure */ 1756 static void _free_nameservers(struct resolv_cache_info* cache_info); 1757 /* look up the named cache, and creates one if needed */ 1758 static struct resolv_cache* _get_res_cache_for_iface_locked(const char* ifname); 1759 /* empty the named cache */ 1760 static void _flush_cache_for_iface_locked(const char* ifname); 1761 /* empty the nameservers set for the named cache */ 1762 static void _free_nameservers_locked(struct resolv_cache_info* cache_info); 1763 /* lookup the namserver for the name interface */ 1764 static int _get_nameserver_locked(const char* ifname, int n, char* addr, int addrLen); 1765 /* lookup the addr of the nameserver for the named interface */ 1766 static struct addrinfo* _get_nameserver_addr_locked(const char* ifname, int n); 1767 /* lookup the inteface's address */ 1768 static struct in_addr* _get_addr_locked(const char * ifname); 1769 1770 1771 1772 static void 1773 _res_cache_init(void) 1774 { 1775 const char* env = getenv(CONFIG_ENV); 1776 1777 if (env && atoi(env) == 0) { 1778 /* the cache is disabled */ 1779 return; 1780 } 1781 1782 memset(&_res_default_ifname, 0, sizeof(_res_default_ifname)); 1783 memset(&_res_cache_list, 0, sizeof(_res_cache_list)); 1784 pthread_mutex_init(&_res_cache_list_lock, NULL); 1785 } 1786 1787 struct resolv_cache* 1788 __get_res_cache(void) 1789 { 1790 struct resolv_cache *cache; 1791 1792 pthread_once(&_res_cache_once, _res_cache_init); 1793 1794 pthread_mutex_lock(&_res_cache_list_lock); 1795 1796 char* ifname = _get_default_iface_locked(); 1797 1798 // if default interface not set then use the first cache 1799 // associated with an interface as the default one. 1800 if (ifname[0] == '\0') { 1801 struct resolv_cache_info* cache_info = _res_cache_list.next; 1802 while (cache_info) { 1803 if (cache_info->ifname[0] != '\0') { 1804 ifname = cache_info->ifname; 1805 break; 1806 } 1807 1808 cache_info = cache_info->next; 1809 } 1810 } 1811 cache = _get_res_cache_for_iface_locked(ifname); 1812 1813 pthread_mutex_unlock(&_res_cache_list_lock); 1814 XLOG("_get_res_cache. default_ifname = %s\n", ifname); 1815 return cache; 1816 } 1817 1818 static struct resolv_cache* 1819 _get_res_cache_for_iface_locked(const char* ifname) 1820 { 1821 if (ifname == NULL) 1822 return NULL; 1823 1824 struct resolv_cache* cache = _find_named_cache_locked(ifname); 1825 if (!cache) { 1826 struct resolv_cache_info* cache_info = _create_cache_info(); 1827 if (cache_info) { 1828 cache = _resolv_cache_create(); 1829 if (cache) { 1830 int len = sizeof(cache_info->ifname); 1831 cache_info->cache = cache; 1832 strncpy(cache_info->ifname, ifname, len - 1); 1833 cache_info->ifname[len - 1] = '\0'; 1834 1835 _insert_cache_info_locked(cache_info); 1836 } else { 1837 free(cache_info); 1838 } 1839 } 1840 } 1841 return cache; 1842 } 1843 1844 void 1845 _resolv_cache_reset(unsigned generation) 1846 { 1847 XLOG("%s: generation=%d", __FUNCTION__, generation); 1848 1849 pthread_once(&_res_cache_once, _res_cache_init); 1850 pthread_mutex_lock(&_res_cache_list_lock); 1851 1852 char* ifname = _get_default_iface_locked(); 1853 // if default interface not set then use the first cache 1854 // associated with an interface as the default one. 1855 // Note: Copied the code from __get_res_cache since this 1856 // method will be deleted/obsolete when cache per interface 1857 // implemented all over 1858 if (ifname[0] == '\0') { 1859 struct resolv_cache_info* cache_info = _res_cache_list.next; 1860 while (cache_info) { 1861 if (cache_info->ifname[0] != '\0') { 1862 ifname = cache_info->ifname; 1863 break; 1864 } 1865 1866 cache_info = cache_info->next; 1867 } 1868 } 1869 struct resolv_cache* cache = _get_res_cache_for_iface_locked(ifname); 1870 1871 if (cache != NULL) { 1872 pthread_mutex_lock( &cache->lock ); 1873 if (cache->generation != generation) { 1874 _cache_flush_locked(cache); 1875 cache->generation = generation; 1876 } 1877 pthread_mutex_unlock( &cache->lock ); 1878 } 1879 1880 pthread_mutex_unlock(&_res_cache_list_lock); 1881 } 1882 1883 void 1884 _resolv_flush_cache_for_default_iface(void) 1885 { 1886 char* ifname; 1887 1888 pthread_once(&_res_cache_once, _res_cache_init); 1889 pthread_mutex_lock(&_res_cache_list_lock); 1890 1891 ifname = _get_default_iface_locked(); 1892 _flush_cache_for_iface_locked(ifname); 1893 1894 pthread_mutex_unlock(&_res_cache_list_lock); 1895 } 1896 1897 void 1898 _resolv_flush_cache_for_iface(const char* ifname) 1899 { 1900 pthread_once(&_res_cache_once, _res_cache_init); 1901 pthread_mutex_lock(&_res_cache_list_lock); 1902 1903 _flush_cache_for_iface_locked(ifname); 1904 1905 pthread_mutex_unlock(&_res_cache_list_lock); 1906 } 1907 1908 static void 1909 _flush_cache_for_iface_locked(const char* ifname) 1910 { 1911 struct resolv_cache* cache = _find_named_cache_locked(ifname); 1912 if (cache) { 1913 pthread_mutex_lock(&cache->lock); 1914 _cache_flush_locked(cache); 1915 pthread_mutex_unlock(&cache->lock); 1916 } 1917 } 1918 1919 static struct resolv_cache_info* 1920 _create_cache_info(void) 1921 { 1922 struct resolv_cache_info* cache_info; 1923 1924 cache_info = calloc(sizeof(*cache_info), 1); 1925 return cache_info; 1926 } 1927 1928 static void 1929 _insert_cache_info_locked(struct resolv_cache_info* cache_info) 1930 { 1931 struct resolv_cache_info* last; 1932 1933 for (last = &_res_cache_list; last->next; last = last->next); 1934 1935 last->next = cache_info; 1936 1937 } 1938 1939 static struct resolv_cache* 1940 _find_named_cache_locked(const char* ifname) { 1941 1942 struct resolv_cache_info* info = _find_cache_info_locked(ifname); 1943 1944 if (info != NULL) return info->cache; 1945 1946 return NULL; 1947 } 1948 1949 static struct resolv_cache_info* 1950 _find_cache_info_locked(const char* ifname) 1951 { 1952 if (ifname == NULL) 1953 return NULL; 1954 1955 struct resolv_cache_info* cache_info = _res_cache_list.next; 1956 1957 while (cache_info) { 1958 if (strcmp(cache_info->ifname, ifname) == 0) { 1959 break; 1960 } 1961 1962 cache_info = cache_info->next; 1963 } 1964 return cache_info; 1965 } 1966 1967 static char* 1968 _get_default_iface_locked(void) 1969 { 1970 char* iface = _res_default_ifname; 1971 1972 return iface; 1973 } 1974 1975 void 1976 _resolv_set_default_iface(const char* ifname) 1977 { 1978 XLOG("_resolv_set_default_if ifname %s\n",ifname); 1979 1980 pthread_once(&_res_cache_once, _res_cache_init); 1981 pthread_mutex_lock(&_res_cache_list_lock); 1982 1983 int size = sizeof(_res_default_ifname); 1984 memset(_res_default_ifname, 0, size); 1985 strncpy(_res_default_ifname, ifname, size - 1); 1986 _res_default_ifname[size - 1] = '\0'; 1987 1988 pthread_mutex_unlock(&_res_cache_list_lock); 1989 } 1990 1991 void 1992 _resolv_set_nameservers_for_iface(const char* ifname, char** servers, int numservers) 1993 { 1994 int i, rt, index; 1995 struct addrinfo hints; 1996 char sbuf[NI_MAXSERV]; 1997 1998 pthread_once(&_res_cache_once, _res_cache_init); 1999 2000 pthread_mutex_lock(&_res_cache_list_lock); 2001 // creates the cache if not created 2002 _get_res_cache_for_iface_locked(ifname); 2003 2004 struct resolv_cache_info* cache_info = _find_cache_info_locked(ifname); 2005 2006 if (cache_info != NULL) { 2007 // free current before adding new 2008 _free_nameservers_locked(cache_info); 2009 2010 memset(&hints, 0, sizeof(hints)); 2011 hints.ai_family = PF_UNSPEC; 2012 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 2013 hints.ai_flags = AI_NUMERICHOST; 2014 sprintf(sbuf, "%u", NAMESERVER_PORT); 2015 2016 index = 0; 2017 for (i = 0; i < numservers && i < MAXNS; i++) { 2018 rt = getaddrinfo(servers[i], sbuf, &hints, &cache_info->nsaddrinfo[index]); 2019 if (rt == 0) { 2020 cache_info->nameservers[index] = strdup(servers[i]); 2021 index++; 2022 } else { 2023 cache_info->nsaddrinfo[index] = NULL; 2024 } 2025 } 2026 } 2027 pthread_mutex_unlock(&_res_cache_list_lock); 2028 } 2029 2030 static void 2031 _free_nameservers_locked(struct resolv_cache_info* cache_info) 2032 { 2033 int i; 2034 for (i = 0; i <= MAXNS; i++) { 2035 free(cache_info->nameservers[i]); 2036 cache_info->nameservers[i] = NULL; 2037 if (cache_info->nsaddrinfo[i] != NULL) { 2038 freeaddrinfo(cache_info->nsaddrinfo[i]); 2039 cache_info->nsaddrinfo[i] = NULL; 2040 } 2041 } 2042 } 2043 2044 int 2045 _resolv_cache_get_nameserver(int n, char* addr, int addrLen) 2046 { 2047 char *ifname; 2048 int result = 0; 2049 2050 pthread_once(&_res_cache_once, _res_cache_init); 2051 pthread_mutex_lock(&_res_cache_list_lock); 2052 2053 ifname = _get_default_iface_locked(); 2054 result = _get_nameserver_locked(ifname, n, addr, addrLen); 2055 2056 pthread_mutex_unlock(&_res_cache_list_lock); 2057 return result; 2058 } 2059 2060 static int 2061 _get_nameserver_locked(const char* ifname, int n, char* addr, int addrLen) 2062 { 2063 int len = 0; 2064 char* ns; 2065 struct resolv_cache_info* cache_info; 2066 2067 if (n < 1 || n > MAXNS || !addr) 2068 return 0; 2069 2070 cache_info = _find_cache_info_locked(ifname); 2071 if (cache_info) { 2072 ns = cache_info->nameservers[n - 1]; 2073 if (ns) { 2074 len = strlen(ns); 2075 if (len < addrLen) { 2076 strncpy(addr, ns, len); 2077 addr[len] = '\0'; 2078 } else { 2079 len = 0; 2080 } 2081 } 2082 } 2083 2084 return len; 2085 } 2086 2087 struct addrinfo* 2088 _cache_get_nameserver_addr(int n) 2089 { 2090 struct addrinfo *result; 2091 char* ifname; 2092 2093 pthread_once(&_res_cache_once, _res_cache_init); 2094 pthread_mutex_lock(&_res_cache_list_lock); 2095 2096 ifname = _get_default_iface_locked(); 2097 2098 result = _get_nameserver_addr_locked(ifname, n); 2099 pthread_mutex_unlock(&_res_cache_list_lock); 2100 return result; 2101 } 2102 2103 static struct addrinfo* 2104 _get_nameserver_addr_locked(const char* ifname, int n) 2105 { 2106 struct addrinfo* ai = NULL; 2107 struct resolv_cache_info* cache_info; 2108 2109 if (n < 1 || n > MAXNS) 2110 return NULL; 2111 2112 cache_info = _find_cache_info_locked(ifname); 2113 if (cache_info) { 2114 ai = cache_info->nsaddrinfo[n - 1]; 2115 } 2116 return ai; 2117 } 2118 2119 void 2120 _resolv_set_addr_of_iface(const char* ifname, struct in_addr* addr) 2121 { 2122 pthread_once(&_res_cache_once, _res_cache_init); 2123 pthread_mutex_lock(&_res_cache_list_lock); 2124 struct resolv_cache_info* cache_info = _find_cache_info_locked(ifname); 2125 if (cache_info) { 2126 memcpy(&cache_info->ifaddr, addr, sizeof(*addr)); 2127 2128 if (DEBUG) { 2129 char* addr_s = inet_ntoa(cache_info->ifaddr); 2130 XLOG("address of interface %s is %s\n", ifname, addr_s); 2131 } 2132 } 2133 pthread_mutex_unlock(&_res_cache_list_lock); 2134 } 2135 2136 struct in_addr* 2137 _resolv_get_addr_of_default_iface(void) 2138 { 2139 struct in_addr* ai = NULL; 2140 char* ifname; 2141 2142 pthread_once(&_res_cache_once, _res_cache_init); 2143 pthread_mutex_lock(&_res_cache_list_lock); 2144 ifname = _get_default_iface_locked(); 2145 ai = _get_addr_locked(ifname); 2146 pthread_mutex_unlock(&_res_cache_list_lock); 2147 2148 return ai; 2149 } 2150 2151 struct in_addr* 2152 _resolv_get_addr_of_iface(const char* ifname) 2153 { 2154 struct in_addr* ai = NULL; 2155 2156 pthread_once(&_res_cache_once, _res_cache_init); 2157 pthread_mutex_lock(&_res_cache_list_lock); 2158 ai =_get_addr_locked(ifname); 2159 pthread_mutex_unlock(&_res_cache_list_lock); 2160 return ai; 2161 } 2162 2163 static struct in_addr* 2164 _get_addr_locked(const char * ifname) 2165 { 2166 struct resolv_cache_info* cache_info = _find_cache_info_locked(ifname); 2167 if (cache_info) { 2168 return &cache_info->ifaddr; 2169 } 2170 return NULL; 2171 } 2172
