1 /* Copyright 2006-2007 Niels Provos 2 * Copyright 2007-2012 Nick Mathewson and Niels Provos 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. The name of the author may not be used to endorse or promote products 13 * derived from this software without specific prior written permission. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 /* Based on software by Adam Langly. Adam's original message: 28 * 29 * Async DNS Library 30 * Adam Langley <agl (at) imperialviolet.org> 31 * http://www.imperialviolet.org/eventdns.html 32 * Public Domain code 33 * 34 * This software is Public Domain. To view a copy of the public domain dedication, 35 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to 36 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. 37 * 38 * I ask and expect, but do not require, that all derivative works contain an 39 * attribution similar to: 40 * Parts developed by Adam Langley <agl (at) imperialviolet.org> 41 * 42 * You may wish to replace the word "Parts" with something else depending on 43 * the amount of original code. 44 * 45 * (Derivative works does not include programs which link against, run or include 46 * the source verbatim in their source distributions) 47 * 48 * Version: 0.1b 49 */ 50 51 #include <sys/types.h> 52 #include "event2/event-config.h" 53 54 #ifndef _FORTIFY_SOURCE 55 #define _FORTIFY_SOURCE 3 56 #endif 57 58 #include <string.h> 59 #include <fcntl.h> 60 #ifdef _EVENT_HAVE_SYS_TIME_H 61 #include <sys/time.h> 62 #endif 63 #ifdef _EVENT_HAVE_STDINT_H 64 #include <stdint.h> 65 #endif 66 #include <stdlib.h> 67 #include <string.h> 68 #include <errno.h> 69 #ifdef _EVENT_HAVE_UNISTD_H 70 #include <unistd.h> 71 #endif 72 #include <limits.h> 73 #include <sys/stat.h> 74 #include <stdio.h> 75 #include <stdarg.h> 76 #ifdef WIN32 77 #include <winsock2.h> 78 #include <ws2tcpip.h> 79 #ifndef _WIN32_IE 80 #define _WIN32_IE 0x400 81 #endif 82 #include <shlobj.h> 83 #endif 84 85 #include "event2/dns.h" 86 #include "event2/dns_struct.h" 87 #include "event2/dns_compat.h" 88 #include "event2/util.h" 89 #include "event2/event.h" 90 #include "event2/event_struct.h" 91 #include "event2/thread.h" 92 93 #include "event2/bufferevent.h" 94 #include "event2/bufferevent_struct.h" 95 #include "bufferevent-internal.h" 96 97 #include "defer-internal.h" 98 #include "log-internal.h" 99 #include "mm-internal.h" 100 #include "strlcpy-internal.h" 101 #include "ipv6-internal.h" 102 #include "util-internal.h" 103 #include "evthread-internal.h" 104 #ifdef WIN32 105 #include <ctype.h> 106 #include <winsock2.h> 107 #include <windows.h> 108 #include <iphlpapi.h> 109 #include <io.h> 110 #else 111 #include <sys/socket.h> 112 #include <netinet/in.h> 113 #include <arpa/inet.h> 114 #endif 115 116 #ifdef _EVENT_HAVE_NETINET_IN6_H 117 #include <netinet/in6.h> 118 #endif 119 120 #define EVDNS_LOG_DEBUG 0 121 #define EVDNS_LOG_WARN 1 122 #define EVDNS_LOG_MSG 2 123 124 #ifndef HOST_NAME_MAX 125 #define HOST_NAME_MAX 255 126 #endif 127 128 #include <stdio.h> 129 130 #undef MIN 131 #define MIN(a,b) ((a)<(b)?(a):(b)) 132 133 #define ASSERT_VALID_REQUEST(req) \ 134 EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req)) 135 136 #define u64 ev_uint64_t 137 #define u32 ev_uint32_t 138 #define u16 ev_uint16_t 139 #define u8 ev_uint8_t 140 141 /* maximum number of addresses from a single packet */ 142 /* that we bother recording */ 143 #define MAX_V4_ADDRS 32 144 #define MAX_V6_ADDRS 32 145 146 147 #define TYPE_A EVDNS_TYPE_A 148 #define TYPE_CNAME 5 149 #define TYPE_PTR EVDNS_TYPE_PTR 150 #define TYPE_SOA EVDNS_TYPE_SOA 151 #define TYPE_AAAA EVDNS_TYPE_AAAA 152 153 #define CLASS_INET EVDNS_CLASS_INET 154 155 /* Persistent handle. We keep this separate from 'struct request' since we 156 * need some object to last for as long as an evdns_request is outstanding so 157 * that it can be canceled, whereas a search request can lead to multiple 158 * 'struct request' instances being created over its lifetime. */ 159 struct evdns_request { 160 struct request *current_req; 161 struct evdns_base *base; 162 163 int pending_cb; /* Waiting for its callback to be invoked; not 164 * owned by event base any more. */ 165 166 /* elements used by the searching code */ 167 int search_index; 168 struct search_state *search_state; 169 char *search_origname; /* needs to be free()ed */ 170 int search_flags; 171 }; 172 173 struct request { 174 u8 *request; /* the dns packet data */ 175 u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */ 176 unsigned int request_len; 177 int reissue_count; 178 int tx_count; /* the number of times that this packet has been sent */ 179 void *user_pointer; /* the pointer given to us for this request */ 180 evdns_callback_type user_callback; 181 struct nameserver *ns; /* the server which we last sent it */ 182 183 /* these objects are kept in a circular list */ 184 /* XXX We could turn this into a CIRCLEQ. */ 185 struct request *next, *prev; 186 187 struct event timeout_event; 188 189 u16 trans_id; /* the transaction id */ 190 unsigned request_appended :1; /* true if the request pointer is data which follows this struct */ 191 unsigned transmit_me :1; /* needs to be transmitted */ 192 193 /* XXXX This is a horrible hack. */ 194 char **put_cname_in_ptr; /* store the cname here if we get one. */ 195 196 struct evdns_base *base; 197 198 struct evdns_request *handle; 199 }; 200 201 struct reply { 202 unsigned int type; 203 unsigned int have_answer : 1; 204 union { 205 struct { 206 u32 addrcount; 207 u32 addresses[MAX_V4_ADDRS]; 208 } a; 209 struct { 210 u32 addrcount; 211 struct in6_addr addresses[MAX_V6_ADDRS]; 212 } aaaa; 213 struct { 214 char name[HOST_NAME_MAX]; 215 } ptr; 216 } data; 217 }; 218 219 struct nameserver { 220 evutil_socket_t socket; /* a connected UDP socket */ 221 struct sockaddr_storage address; 222 ev_socklen_t addrlen; 223 int failed_times; /* number of times which we have given this server a chance */ 224 int timedout; /* number of times in a row a request has timed out */ 225 struct event event; 226 /* these objects are kept in a circular list */ 227 struct nameserver *next, *prev; 228 struct event timeout_event; /* used to keep the timeout for */ 229 /* when we next probe this server. */ 230 /* Valid if state == 0 */ 231 /* Outstanding probe request for this nameserver, if any */ 232 struct evdns_request *probe_request; 233 char state; /* zero if we think that this server is down */ 234 char choked; /* true if we have an EAGAIN from this server's socket */ 235 char write_waiting; /* true if we are waiting for EV_WRITE events */ 236 struct evdns_base *base; 237 }; 238 239 240 /* Represents a local port where we're listening for DNS requests. Right now, */ 241 /* only UDP is supported. */ 242 struct evdns_server_port { 243 evutil_socket_t socket; /* socket we use to read queries and write replies. */ 244 int refcnt; /* reference count. */ 245 char choked; /* Are we currently blocked from writing? */ 246 char closing; /* Are we trying to close this port, pending writes? */ 247 evdns_request_callback_fn_type user_callback; /* Fn to handle requests */ 248 void *user_data; /* Opaque pointer passed to user_callback */ 249 struct event event; /* Read/write event */ 250 /* circular list of replies that we want to write. */ 251 struct server_request *pending_replies; 252 struct event_base *event_base; 253 254 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 255 void *lock; 256 #endif 257 }; 258 259 /* Represents part of a reply being built. (That is, a single RR.) */ 260 struct server_reply_item { 261 struct server_reply_item *next; /* next item in sequence. */ 262 char *name; /* name part of the RR */ 263 u16 type; /* The RR type */ 264 u16 class; /* The RR class (usually CLASS_INET) */ 265 u32 ttl; /* The RR TTL */ 266 char is_name; /* True iff data is a label */ 267 u16 datalen; /* Length of data; -1 if data is a label */ 268 void *data; /* The contents of the RR */ 269 }; 270 271 /* Represents a request that we've received as a DNS server, and holds */ 272 /* the components of the reply as we're constructing it. */ 273 struct server_request { 274 /* Pointers to the next and previous entries on the list of replies */ 275 /* that we're waiting to write. Only set if we have tried to respond */ 276 /* and gotten EAGAIN. */ 277 struct server_request *next_pending; 278 struct server_request *prev_pending; 279 280 u16 trans_id; /* Transaction id. */ 281 struct evdns_server_port *port; /* Which port received this request on? */ 282 struct sockaddr_storage addr; /* Where to send the response */ 283 ev_socklen_t addrlen; /* length of addr */ 284 285 int n_answer; /* how many answer RRs have been set? */ 286 int n_authority; /* how many authority RRs have been set? */ 287 int n_additional; /* how many additional RRs have been set? */ 288 289 struct server_reply_item *answer; /* linked list of answer RRs */ 290 struct server_reply_item *authority; /* linked list of authority RRs */ 291 struct server_reply_item *additional; /* linked list of additional RRs */ 292 293 /* Constructed response. Only set once we're ready to send a reply. */ 294 /* Once this is set, the RR fields are cleared, and no more should be set. */ 295 char *response; 296 size_t response_len; 297 298 /* Caller-visible fields: flags, questions. */ 299 struct evdns_server_request base; 300 }; 301 302 struct evdns_base { 303 /* An array of n_req_heads circular lists for inflight requests. 304 * Each inflight request req is in req_heads[req->trans_id % n_req_heads]. 305 */ 306 struct request **req_heads; 307 /* A circular list of requests that we're waiting to send, but haven't 308 * sent yet because there are too many requests inflight */ 309 struct request *req_waiting_head; 310 /* A circular list of nameservers. */ 311 struct nameserver *server_head; 312 int n_req_heads; 313 314 struct event_base *event_base; 315 316 /* The number of good nameservers that we have */ 317 int global_good_nameservers; 318 319 /* inflight requests are contained in the req_head list */ 320 /* and are actually going out across the network */ 321 int global_requests_inflight; 322 /* requests which aren't inflight are in the waiting list */ 323 /* and are counted here */ 324 int global_requests_waiting; 325 326 int global_max_requests_inflight; 327 328 struct timeval global_timeout; /* 5 seconds by default */ 329 int global_max_reissues; /* a reissue occurs when we get some errors from the server */ 330 int global_max_retransmits; /* number of times we'll retransmit a request which timed out */ 331 /* number of timeouts in a row before we consider this server to be down */ 332 int global_max_nameserver_timeout; 333 /* true iff we will use the 0x20 hack to prevent poisoning attacks. */ 334 int global_randomize_case; 335 336 /* The first time that a nameserver fails, how long do we wait before 337 * probing to see if it has returned? */ 338 struct timeval global_nameserver_probe_initial_timeout; 339 340 /** Port to bind to for outgoing DNS packets. */ 341 struct sockaddr_storage global_outgoing_address; 342 /** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */ 343 ev_socklen_t global_outgoing_addrlen; 344 345 struct timeval global_getaddrinfo_allow_skew; 346 347 int getaddrinfo_ipv4_timeouts; 348 int getaddrinfo_ipv6_timeouts; 349 int getaddrinfo_ipv4_answered; 350 int getaddrinfo_ipv6_answered; 351 352 struct search_state *global_search_state; 353 354 TAILQ_HEAD(hosts_list, hosts_entry) hostsdb; 355 356 #ifndef _EVENT_DISABLE_THREAD_SUPPORT 357 void *lock; 358 #endif 359 }; 360 361 struct hosts_entry { 362 TAILQ_ENTRY(hosts_entry) next; 363 union { 364 struct sockaddr sa; 365 struct sockaddr_in sin; 366 struct sockaddr_in6 sin6; 367 } addr; 368 int addrlen; 369 char hostname[1]; 370 }; 371 372 static struct evdns_base *current_base = NULL; 373 374 struct evdns_base * 375 evdns_get_global_base(void) 376 { 377 return current_base; 378 } 379 380 /* Given a pointer to an evdns_server_request, get the corresponding */ 381 /* server_request. */ 382 #define TO_SERVER_REQUEST(base_ptr) \ 383 ((struct server_request*) \ 384 (((char*)(base_ptr) - evutil_offsetof(struct server_request, base)))) 385 386 #define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads]) 387 388 static struct nameserver *nameserver_pick(struct evdns_base *base); 389 static void evdns_request_insert(struct request *req, struct request **head); 390 static void evdns_request_remove(struct request *req, struct request **head); 391 static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg); 392 static int evdns_transmit(struct evdns_base *base); 393 static int evdns_request_transmit(struct request *req); 394 static void nameserver_send_probe(struct nameserver *const ns); 395 static void search_request_finished(struct evdns_request *const); 396 static int search_try_next(struct evdns_request *const req); 397 static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg); 398 static void evdns_requests_pump_waiting_queue(struct evdns_base *base); 399 static u16 transaction_id_pick(struct evdns_base *base); 400 static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr); 401 static void request_submit(struct request *const req); 402 403 static int server_request_free(struct server_request *req); 404 static void server_request_free_answers(struct server_request *req); 405 static void server_port_free(struct evdns_server_port *port); 406 static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg); 407 static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename); 408 static int evdns_base_set_option_impl(struct evdns_base *base, 409 const char *option, const char *val, int flags); 410 static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests); 411 412 static int strtoint(const char *const str); 413 414 #ifdef _EVENT_DISABLE_THREAD_SUPPORT 415 #define EVDNS_LOCK(base) _EVUTIL_NIL_STMT 416 #define EVDNS_UNLOCK(base) _EVUTIL_NIL_STMT 417 #define ASSERT_LOCKED(base) _EVUTIL_NIL_STMT 418 #else 419 #define EVDNS_LOCK(base) \ 420 EVLOCK_LOCK((base)->lock, 0) 421 #define EVDNS_UNLOCK(base) \ 422 EVLOCK_UNLOCK((base)->lock, 0) 423 #define ASSERT_LOCKED(base) \ 424 EVLOCK_ASSERT_LOCKED((base)->lock) 425 #endif 426 427 static void 428 default_evdns_log_fn(int warning, const char *buf) 429 { 430 if (warning == EVDNS_LOG_WARN) 431 event_warnx("[evdns] %s", buf); 432 else if (warning == EVDNS_LOG_MSG) 433 event_msgx("[evdns] %s", buf); 434 else 435 event_debug(("[evdns] %s", buf)); 436 } 437 438 static evdns_debug_log_fn_type evdns_log_fn = NULL; 439 440 void 441 evdns_set_log_fn(evdns_debug_log_fn_type fn) 442 { 443 evdns_log_fn = fn; 444 } 445 446 #ifdef __GNUC__ 447 #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3))) 448 #else 449 #define EVDNS_LOG_CHECK 450 #endif 451 452 static void _evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK; 453 static void 454 _evdns_log(int warn, const char *fmt, ...) 455 { 456 va_list args; 457 char buf[512]; 458 if (!evdns_log_fn) 459 return; 460 va_start(args,fmt); 461 evutil_vsnprintf(buf, sizeof(buf), fmt, args); 462 va_end(args); 463 if (evdns_log_fn) { 464 if (warn == EVDNS_LOG_MSG) 465 warn = EVDNS_LOG_WARN; 466 evdns_log_fn(warn, buf); 467 } else { 468 default_evdns_log_fn(warn, buf); 469 } 470 471 } 472 473 #define log _evdns_log 474 475 /* This walks the list of inflight requests to find the */ 476 /* one with a matching transaction id. Returns NULL on */ 477 /* failure */ 478 static struct request * 479 request_find_from_trans_id(struct evdns_base *base, u16 trans_id) { 480 struct request *req = REQ_HEAD(base, trans_id); 481 struct request *const started_at = req; 482 483 ASSERT_LOCKED(base); 484 485 if (req) { 486 do { 487 if (req->trans_id == trans_id) return req; 488 req = req->next; 489 } while (req != started_at); 490 } 491 492 return NULL; 493 } 494 495 /* a libevent callback function which is called when a nameserver */ 496 /* has gone down and we want to test if it has came back to life yet */ 497 static void 498 nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) { 499 struct nameserver *const ns = (struct nameserver *) arg; 500 (void)fd; 501 (void)events; 502 503 EVDNS_LOCK(ns->base); 504 nameserver_send_probe(ns); 505 EVDNS_UNLOCK(ns->base); 506 } 507 508 /* a libevent callback which is called when a nameserver probe (to see if */ 509 /* it has come back to life) times out. We increment the count of failed_times */ 510 /* and wait longer to send the next probe packet. */ 511 static void 512 nameserver_probe_failed(struct nameserver *const ns) { 513 struct timeval timeout; 514 int i; 515 516 ASSERT_LOCKED(ns->base); 517 (void) evtimer_del(&ns->timeout_event); 518 if (ns->state == 1) { 519 /* This can happen if the nameserver acts in a way which makes us mark */ 520 /* it as bad and then starts sending good replies. */ 521 return; 522 } 523 524 #define MAX_PROBE_TIMEOUT 3600 525 #define TIMEOUT_BACKOFF_FACTOR 3 526 527 memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout, 528 sizeof(struct timeval)); 529 for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) { 530 timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR; 531 timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR; 532 if (timeout.tv_usec > 1000000) { 533 timeout.tv_sec += timeout.tv_usec / 1000000; 534 timeout.tv_usec %= 1000000; 535 } 536 } 537 if (timeout.tv_sec > MAX_PROBE_TIMEOUT) { 538 timeout.tv_sec = MAX_PROBE_TIMEOUT; 539 timeout.tv_usec = 0; 540 } 541 542 ns->failed_times++; 543 544 if (evtimer_add(&ns->timeout_event, &timeout) < 0) { 545 char addrbuf[128]; 546 log(EVDNS_LOG_WARN, 547 "Error from libevent when adding timer event for %s", 548 evutil_format_sockaddr_port( 549 (struct sockaddr *)&ns->address, 550 addrbuf, sizeof(addrbuf))); 551 } 552 } 553 554 /* called when a nameserver has been deemed to have failed. For example, too */ 555 /* many packets have timed out etc */ 556 static void 557 nameserver_failed(struct nameserver *const ns, const char *msg) { 558 struct request *req, *started_at; 559 struct evdns_base *base = ns->base; 560 int i; 561 char addrbuf[128]; 562 563 ASSERT_LOCKED(base); 564 /* if this nameserver has already been marked as failed */ 565 /* then don't do anything */ 566 if (!ns->state) return; 567 568 log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s", 569 evutil_format_sockaddr_port( 570 (struct sockaddr *)&ns->address, 571 addrbuf, sizeof(addrbuf)), 572 msg); 573 574 base->global_good_nameservers--; 575 EVUTIL_ASSERT(base->global_good_nameservers >= 0); 576 if (base->global_good_nameservers == 0) { 577 log(EVDNS_LOG_MSG, "All nameservers have failed"); 578 } 579 580 ns->state = 0; 581 ns->failed_times = 1; 582 583 if (evtimer_add(&ns->timeout_event, 584 &base->global_nameserver_probe_initial_timeout) < 0) { 585 log(EVDNS_LOG_WARN, 586 "Error from libevent when adding timer event for %s", 587 evutil_format_sockaddr_port( 588 (struct sockaddr *)&ns->address, 589 addrbuf, sizeof(addrbuf))); 590 /* ???? Do more? */ 591 } 592 593 /* walk the list of inflight requests to see if any can be reassigned to */ 594 /* a different server. Requests in the waiting queue don't have a */ 595 /* nameserver assigned yet */ 596 597 /* if we don't have *any* good nameservers then there's no point */ 598 /* trying to reassign requests to one */ 599 if (!base->global_good_nameservers) return; 600 601 for (i = 0; i < base->n_req_heads; ++i) { 602 req = started_at = base->req_heads[i]; 603 if (req) { 604 do { 605 if (req->tx_count == 0 && req->ns == ns) { 606 /* still waiting to go out, can be moved */ 607 /* to another server */ 608 req->ns = nameserver_pick(base); 609 } 610 req = req->next; 611 } while (req != started_at); 612 } 613 } 614 } 615 616 static void 617 nameserver_up(struct nameserver *const ns) 618 { 619 char addrbuf[128]; 620 ASSERT_LOCKED(ns->base); 621 if (ns->state) return; 622 log(EVDNS_LOG_MSG, "Nameserver %s is back up", 623 evutil_format_sockaddr_port( 624 (struct sockaddr *)&ns->address, 625 addrbuf, sizeof(addrbuf))); 626 evtimer_del(&ns->timeout_event); 627 if (ns->probe_request) { 628 evdns_cancel_request(ns->base, ns->probe_request); 629 ns->probe_request = NULL; 630 } 631 ns->state = 1; 632 ns->failed_times = 0; 633 ns->timedout = 0; 634 ns->base->global_good_nameservers++; 635 } 636 637 static void 638 request_trans_id_set(struct request *const req, const u16 trans_id) { 639 req->trans_id = trans_id; 640 *((u16 *) req->request) = htons(trans_id); 641 } 642 643 /* Called to remove a request from a list and dealloc it. */ 644 /* head is a pointer to the head of the list it should be */ 645 /* removed from or NULL if the request isn't in a list. */ 646 /* when free_handle is one, free the handle as well. */ 647 static void 648 request_finished(struct request *const req, struct request **head, int free_handle) { 649 struct evdns_base *base = req->base; 650 int was_inflight = (head != &base->req_waiting_head); 651 EVDNS_LOCK(base); 652 ASSERT_VALID_REQUEST(req); 653 654 if (head) 655 evdns_request_remove(req, head); 656 657 log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req); 658 if (was_inflight) { 659 evtimer_del(&req->timeout_event); 660 base->global_requests_inflight--; 661 } else { 662 base->global_requests_waiting--; 663 } 664 /* it was initialized during request_new / evtimer_assign */ 665 event_debug_unassign(&req->timeout_event); 666 667 if (!req->request_appended) { 668 /* need to free the request data on it's own */ 669 mm_free(req->request); 670 } else { 671 /* the request data is appended onto the header */ 672 /* so everything gets free()ed when we: */ 673 } 674 675 if (req->handle) { 676 EVUTIL_ASSERT(req->handle->current_req == req); 677 678 if (free_handle) { 679 search_request_finished(req->handle); 680 req->handle->current_req = NULL; 681 if (! req->handle->pending_cb) { 682 /* If we're planning to run the callback, 683 * don't free the handle until later. */ 684 mm_free(req->handle); 685 } 686 req->handle = NULL; /* If we have a bug, let's crash 687 * early */ 688 } else { 689 req->handle->current_req = NULL; 690 } 691 } 692 693 mm_free(req); 694 695 evdns_requests_pump_waiting_queue(base); 696 EVDNS_UNLOCK(base); 697 } 698 699 /* This is called when a server returns a funny error code. */ 700 /* We try the request again with another server. */ 701 /* */ 702 /* return: */ 703 /* 0 ok */ 704 /* 1 failed/reissue is pointless */ 705 static int 706 request_reissue(struct request *req) { 707 const struct nameserver *const last_ns = req->ns; 708 ASSERT_LOCKED(req->base); 709 ASSERT_VALID_REQUEST(req); 710 /* the last nameserver should have been marked as failing */ 711 /* by the caller of this function, therefore pick will try */ 712 /* not to return it */ 713 req->ns = nameserver_pick(req->base); 714 if (req->ns == last_ns) { 715 /* ... but pick did return it */ 716 /* not a lot of point in trying again with the */ 717 /* same server */ 718 return 1; 719 } 720 721 req->reissue_count++; 722 req->tx_count = 0; 723 req->transmit_me = 1; 724 725 return 0; 726 } 727 728 /* this function looks for space on the inflight queue and promotes */ 729 /* requests from the waiting queue if it can. */ 730 /* */ 731 /* TODO: */ 732 /* add return code, see at nameserver_pick() and other functions. */ 733 static void 734 evdns_requests_pump_waiting_queue(struct evdns_base *base) { 735 ASSERT_LOCKED(base); 736 while (base->global_requests_inflight < base->global_max_requests_inflight && 737 base->global_requests_waiting) { 738 struct request *req; 739 740 EVUTIL_ASSERT(base->req_waiting_head); 741 req = base->req_waiting_head; 742 743 req->ns = nameserver_pick(base); 744 if (!req->ns) 745 return; 746 747 /* move a request from the waiting queue to the inflight queue */ 748 evdns_request_remove(req, &base->req_waiting_head); 749 750 base->global_requests_waiting--; 751 base->global_requests_inflight++; 752 753 request_trans_id_set(req, transaction_id_pick(base)); 754 755 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 756 evdns_request_transmit(req); 757 evdns_transmit(base); 758 } 759 } 760 761 /* TODO(nickm) document */ 762 struct deferred_reply_callback { 763 struct deferred_cb deferred; 764 struct evdns_request *handle; 765 u8 request_type; 766 u8 have_reply; 767 u32 ttl; 768 u32 err; 769 evdns_callback_type user_callback; 770 struct reply reply; 771 }; 772 773 static void 774 reply_run_callback(struct deferred_cb *d, void *user_pointer) 775 { 776 struct deferred_reply_callback *cb = 777 EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred); 778 779 switch (cb->request_type) { 780 case TYPE_A: 781 if (cb->have_reply) 782 cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A, 783 cb->reply.data.a.addrcount, cb->ttl, 784 cb->reply.data.a.addresses, 785 user_pointer); 786 else 787 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 788 break; 789 case TYPE_PTR: 790 if (cb->have_reply) { 791 char *name = cb->reply.data.ptr.name; 792 cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl, 793 &name, user_pointer); 794 } else { 795 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 796 } 797 break; 798 case TYPE_AAAA: 799 if (cb->have_reply) 800 cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, 801 cb->reply.data.aaaa.addrcount, cb->ttl, 802 cb->reply.data.aaaa.addresses, 803 user_pointer); 804 else 805 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); 806 break; 807 default: 808 EVUTIL_ASSERT(0); 809 } 810 811 if (cb->handle && cb->handle->pending_cb) { 812 mm_free(cb->handle); 813 } 814 815 mm_free(cb); 816 } 817 818 static void 819 reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) 820 { 821 struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d)); 822 823 if (!d) { 824 event_warn("%s: Couldn't allocate space for deferred callback.", 825 __func__); 826 return; 827 } 828 829 ASSERT_LOCKED(req->base); 830 831 d->request_type = req->request_type; 832 d->user_callback = req->user_callback; 833 d->ttl = ttl; 834 d->err = err; 835 if (reply) { 836 d->have_reply = 1; 837 memcpy(&d->reply, reply, sizeof(struct reply)); 838 } 839 840 if (req->handle) { 841 req->handle->pending_cb = 1; 842 d->handle = req->handle; 843 } 844 845 event_deferred_cb_init(&d->deferred, reply_run_callback, 846 req->user_pointer); 847 event_deferred_cb_schedule( 848 event_base_get_deferred_cb_queue(req->base->event_base), 849 &d->deferred); 850 } 851 852 /* this processes a parsed reply packet */ 853 static void 854 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { 855 int error; 856 char addrbuf[128]; 857 static const int error_codes[] = { 858 DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, 859 DNS_ERR_NOTIMPL, DNS_ERR_REFUSED 860 }; 861 862 ASSERT_LOCKED(req->base); 863 ASSERT_VALID_REQUEST(req); 864 865 if (flags & 0x020f || !reply || !reply->have_answer) { 866 /* there was an error */ 867 if (flags & 0x0200) { 868 error = DNS_ERR_TRUNCATED; 869 } else if (flags & 0x000f) { 870 u16 error_code = (flags & 0x000f) - 1; 871 if (error_code > 4) { 872 error = DNS_ERR_UNKNOWN; 873 } else { 874 error = error_codes[error_code]; 875 } 876 } else if (reply && !reply->have_answer) { 877 error = DNS_ERR_NODATA; 878 } else { 879 error = DNS_ERR_UNKNOWN; 880 } 881 882 switch (error) { 883 case DNS_ERR_NOTIMPL: 884 case DNS_ERR_REFUSED: 885 /* we regard these errors as marking a bad nameserver */ 886 if (req->reissue_count < req->base->global_max_reissues) { 887 char msg[64]; 888 evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)", 889 error, evdns_err_to_string(error)); 890 nameserver_failed(req->ns, msg); 891 if (!request_reissue(req)) return; 892 } 893 break; 894 case DNS_ERR_SERVERFAILED: 895 /* rcode 2 (servfailed) sometimes means "we 896 * are broken" and sometimes (with some binds) 897 * means "that request was very confusing." 898 * Treat this as a timeout, not a failure. 899 */ 900 log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver" 901 "at %s; will allow the request to time out.", 902 evutil_format_sockaddr_port( 903 (struct sockaddr *)&req->ns->address, 904 addrbuf, sizeof(addrbuf))); 905 break; 906 default: 907 /* we got a good reply from the nameserver: it is up. */ 908 if (req->handle == req->ns->probe_request) { 909 /* Avoid double-free */ 910 req->ns->probe_request = NULL; 911 } 912 913 nameserver_up(req->ns); 914 } 915 916 if (req->handle->search_state && 917 req->request_type != TYPE_PTR) { 918 /* if we have a list of domains to search in, 919 * try the next one */ 920 if (!search_try_next(req->handle)) { 921 /* a new request was issued so this 922 * request is finished and */ 923 /* the user callback will be made when 924 * that request (or a */ 925 /* child of it) finishes. */ 926 return; 927 } 928 } 929 930 /* all else failed. Pass the failure up */ 931 reply_schedule_callback(req, ttl, error, NULL); 932 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 933 } else { 934 /* all ok, tell the user */ 935 reply_schedule_callback(req, ttl, 0, reply); 936 if (req->handle == req->ns->probe_request) 937 req->ns->probe_request = NULL; /* Avoid double-free */ 938 nameserver_up(req->ns); 939 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 940 } 941 } 942 943 static int 944 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { 945 int name_end = -1; 946 int j = *idx; 947 int ptr_count = 0; 948 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while (0) 949 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while (0) 950 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0) 951 952 char *cp = name_out; 953 const char *const end = name_out + name_out_len; 954 955 /* Normally, names are a series of length prefixed strings terminated */ 956 /* with a length of 0 (the lengths are u8's < 63). */ 957 /* However, the length can start with a pair of 1 bits and that */ 958 /* means that the next 14 bits are a pointer within the current */ 959 /* packet. */ 960 961 for (;;) { 962 u8 label_len; 963 if (j >= length) return -1; 964 GET8(label_len); 965 if (!label_len) break; 966 if (label_len & 0xc0) { 967 u8 ptr_low; 968 GET8(ptr_low); 969 if (name_end < 0) name_end = j; 970 j = (((int)label_len & 0x3f) << 8) + ptr_low; 971 /* Make sure that the target offset is in-bounds. */ 972 if (j < 0 || j >= length) return -1; 973 /* If we've jumped more times than there are characters in the 974 * message, we must have a loop. */ 975 if (++ptr_count > length) return -1; 976 continue; 977 } 978 if (label_len > 63) return -1; 979 if (cp != name_out) { 980 if (cp + 1 >= end) return -1; 981 *cp++ = '.'; 982 } 983 if (cp + label_len >= end) return -1; 984 memcpy(cp, packet + j, label_len); 985 cp += label_len; 986 j += label_len; 987 } 988 if (cp >= end) return -1; 989 *cp = '\0'; 990 if (name_end < 0) 991 *idx = j; 992 else 993 *idx = name_end; 994 return 0; 995 err: 996 return -1; 997 } 998 999 /* parses a raw request from a nameserver */ 1000 static int 1001 reply_parse(struct evdns_base *base, u8 *packet, int length) { 1002 int j = 0, k = 0; /* index into packet */ 1003 u16 _t; /* used by the macros */ 1004 u32 _t32; /* used by the macros */ 1005 char tmp_name[256], cmp_name[256]; /* used by the macros */ 1006 int name_matches = 0; 1007 1008 u16 trans_id, questions, answers, authority, additional, datalength; 1009 u16 flags = 0; 1010 u32 ttl, ttl_r = 0xffffffff; 1011 struct reply reply; 1012 struct request *req = NULL; 1013 unsigned int i; 1014 1015 ASSERT_LOCKED(base); 1016 1017 GET16(trans_id); 1018 GET16(flags); 1019 GET16(questions); 1020 GET16(answers); 1021 GET16(authority); 1022 GET16(additional); 1023 (void) authority; /* suppress "unused variable" warnings. */ 1024 (void) additional; /* suppress "unused variable" warnings. */ 1025 1026 req = request_find_from_trans_id(base, trans_id); 1027 if (!req) return -1; 1028 EVUTIL_ASSERT(req->base == base); 1029 1030 memset(&reply, 0, sizeof(reply)); 1031 1032 /* If it's not an answer, it doesn't correspond to any request. */ 1033 if (!(flags & 0x8000)) return -1; /* must be an answer */ 1034 if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) { 1035 /* there was an error and it's not NXDOMAIN */ 1036 goto err; 1037 } 1038 /* if (!answers) return; */ /* must have an answer of some form */ 1039 1040 /* This macro skips a name in the DNS reply. */ 1041 #define SKIP_NAME \ 1042 do { tmp_name[0] = '\0'; \ 1043 if (name_parse(packet, length, &j, tmp_name, \ 1044 sizeof(tmp_name))<0) \ 1045 goto err; \ 1046 } while (0) 1047 #define TEST_NAME \ 1048 do { tmp_name[0] = '\0'; \ 1049 cmp_name[0] = '\0'; \ 1050 k = j; \ 1051 if (name_parse(packet, length, &j, tmp_name, \ 1052 sizeof(tmp_name))<0) \ 1053 goto err; \ 1054 if (name_parse(req->request, req->request_len, &k, \ 1055 cmp_name, sizeof(cmp_name))<0) \ 1056 goto err; \ 1057 if (base->global_randomize_case) { \ 1058 if (strcmp(tmp_name, cmp_name) == 0) \ 1059 name_matches = 1; \ 1060 } else { \ 1061 if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) \ 1062 name_matches = 1; \ 1063 } \ 1064 } while (0) 1065 1066 reply.type = req->request_type; 1067 1068 /* skip over each question in the reply */ 1069 for (i = 0; i < questions; ++i) { 1070 /* the question looks like 1071 * <label:name><u16:type><u16:class> 1072 */ 1073 TEST_NAME; 1074 j += 4; 1075 if (j > length) goto err; 1076 } 1077 1078 if (!name_matches) 1079 goto err; 1080 1081 /* now we have the answer section which looks like 1082 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> 1083 */ 1084 1085 for (i = 0; i < answers; ++i) { 1086 u16 type, class; 1087 1088 SKIP_NAME; 1089 GET16(type); 1090 GET16(class); 1091 GET32(ttl); 1092 GET16(datalength); 1093 1094 if (type == TYPE_A && class == CLASS_INET) { 1095 int addrcount, addrtocopy; 1096 if (req->request_type != TYPE_A) { 1097 j += datalength; continue; 1098 } 1099 if ((datalength & 3) != 0) /* not an even number of As. */ 1100 goto err; 1101 addrcount = datalength >> 2; 1102 addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); 1103 1104 ttl_r = MIN(ttl_r, ttl); 1105 /* we only bother with the first four addresses. */ 1106 if (j + 4*addrtocopy > length) goto err; 1107 memcpy(&reply.data.a.addresses[reply.data.a.addrcount], 1108 packet + j, 4*addrtocopy); 1109 j += 4*addrtocopy; 1110 reply.data.a.addrcount += addrtocopy; 1111 reply.have_answer = 1; 1112 if (reply.data.a.addrcount == MAX_V4_ADDRS) break; 1113 } else if (type == TYPE_PTR && class == CLASS_INET) { 1114 if (req->request_type != TYPE_PTR) { 1115 j += datalength; continue; 1116 } 1117 if (name_parse(packet, length, &j, reply.data.ptr.name, 1118 sizeof(reply.data.ptr.name))<0) 1119 goto err; 1120 ttl_r = MIN(ttl_r, ttl); 1121 reply.have_answer = 1; 1122 break; 1123 } else if (type == TYPE_CNAME) { 1124 char cname[HOST_NAME_MAX]; 1125 if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) { 1126 j += datalength; continue; 1127 } 1128 if (name_parse(packet, length, &j, cname, 1129 sizeof(cname))<0) 1130 goto err; 1131 *req->put_cname_in_ptr = mm_strdup(cname); 1132 } else if (type == TYPE_AAAA && class == CLASS_INET) { 1133 int addrcount, addrtocopy; 1134 if (req->request_type != TYPE_AAAA) { 1135 j += datalength; continue; 1136 } 1137 if ((datalength & 15) != 0) /* not an even number of AAAAs. */ 1138 goto err; 1139 addrcount = datalength >> 4; /* each address is 16 bytes long */ 1140 addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); 1141 ttl_r = MIN(ttl_r, ttl); 1142 1143 /* we only bother with the first four addresses. */ 1144 if (j + 16*addrtocopy > length) goto err; 1145 memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], 1146 packet + j, 16*addrtocopy); 1147 reply.data.aaaa.addrcount += addrtocopy; 1148 j += 16*addrtocopy; 1149 reply.have_answer = 1; 1150 if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break; 1151 } else { 1152 /* skip over any other type of resource */ 1153 j += datalength; 1154 } 1155 } 1156 1157 if (!reply.have_answer) { 1158 for (i = 0; i < authority; ++i) { 1159 u16 type, class; 1160 SKIP_NAME; 1161 GET16(type); 1162 GET16(class); 1163 GET32(ttl); 1164 GET16(datalength); 1165 if (type == TYPE_SOA && class == CLASS_INET) { 1166 u32 serial, refresh, retry, expire, minimum; 1167 SKIP_NAME; 1168 SKIP_NAME; 1169 GET32(serial); 1170 GET32(refresh); 1171 GET32(retry); 1172 GET32(expire); 1173 GET32(minimum); 1174 (void)expire; 1175 (void)retry; 1176 (void)refresh; 1177 (void)serial; 1178 ttl_r = MIN(ttl_r, ttl); 1179 ttl_r = MIN(ttl_r, minimum); 1180 } else { 1181 /* skip over any other type of resource */ 1182 j += datalength; 1183 } 1184 } 1185 } 1186 1187 if (ttl_r == 0xffffffff) 1188 ttl_r = 0; 1189 1190 reply_handle(req, flags, ttl_r, &reply); 1191 return 0; 1192 err: 1193 if (req) 1194 reply_handle(req, flags, 0, NULL); 1195 return -1; 1196 } 1197 1198 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ 1199 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ 1200 /* callback. */ 1201 static int 1202 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen) 1203 { 1204 int j = 0; /* index into packet */ 1205 u16 _t; /* used by the macros */ 1206 char tmp_name[256]; /* used by the macros */ 1207 1208 int i; 1209 u16 trans_id, flags, questions, answers, authority, additional; 1210 struct server_request *server_req = NULL; 1211 1212 ASSERT_LOCKED(port); 1213 1214 /* Get the header fields */ 1215 GET16(trans_id); 1216 GET16(flags); 1217 GET16(questions); 1218 GET16(answers); 1219 GET16(authority); 1220 GET16(additional); 1221 (void)answers; 1222 (void)additional; 1223 (void)authority; 1224 1225 if (flags & 0x8000) return -1; /* Must not be an answer. */ 1226 flags &= 0x0110; /* Only RD and CD get preserved. */ 1227 1228 server_req = mm_malloc(sizeof(struct server_request)); 1229 if (server_req == NULL) return -1; 1230 memset(server_req, 0, sizeof(struct server_request)); 1231 1232 server_req->trans_id = trans_id; 1233 memcpy(&server_req->addr, addr, addrlen); 1234 server_req->addrlen = addrlen; 1235 1236 server_req->base.flags = flags; 1237 server_req->base.nquestions = 0; 1238 server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions); 1239 if (server_req->base.questions == NULL) 1240 goto err; 1241 1242 for (i = 0; i < questions; ++i) { 1243 u16 type, class; 1244 struct evdns_server_question *q; 1245 int namelen; 1246 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) 1247 goto err; 1248 GET16(type); 1249 GET16(class); 1250 namelen = (int)strlen(tmp_name); 1251 q = mm_malloc(sizeof(struct evdns_server_question) + namelen); 1252 if (!q) 1253 goto err; 1254 q->type = type; 1255 q->dns_question_class = class; 1256 memcpy(q->name, tmp_name, namelen+1); 1257 server_req->base.questions[server_req->base.nquestions++] = q; 1258 } 1259 1260 /* Ignore answers, authority, and additional. */ 1261 1262 server_req->port = port; 1263 port->refcnt++; 1264 1265 /* Only standard queries are supported. */ 1266 if (flags & 0x7800) { 1267 evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); 1268 return -1; 1269 } 1270 1271 port->user_callback(&(server_req->base), port->user_data); 1272 1273 return 0; 1274 err: 1275 if (server_req) { 1276 if (server_req->base.questions) { 1277 for (i = 0; i < server_req->base.nquestions; ++i) 1278 mm_free(server_req->base.questions[i]); 1279 mm_free(server_req->base.questions); 1280 } 1281 mm_free(server_req); 1282 } 1283 return -1; 1284 1285 #undef SKIP_NAME 1286 #undef GET32 1287 #undef GET16 1288 #undef GET8 1289 } 1290 1291 1292 void 1293 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) 1294 { 1295 } 1296 1297 void 1298 evdns_set_random_bytes_fn(void (*fn)(char *, size_t)) 1299 { 1300 } 1301 1302 /* Try to choose a strong transaction id which isn't already in flight */ 1303 static u16 1304 transaction_id_pick(struct evdns_base *base) { 1305 ASSERT_LOCKED(base); 1306 for (;;) { 1307 u16 trans_id; 1308 evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id)); 1309 1310 if (trans_id == 0xffff) continue; 1311 /* now check to see if that id is already inflight */ 1312 if (request_find_from_trans_id(base, trans_id) == NULL) 1313 return trans_id; 1314 } 1315 } 1316 1317 /* choose a namesever to use. This function will try to ignore */ 1318 /* nameservers which we think are down and load balance across the rest */ 1319 /* by updating the server_head global each time. */ 1320 static struct nameserver * 1321 nameserver_pick(struct evdns_base *base) { 1322 struct nameserver *started_at = base->server_head, *picked; 1323 ASSERT_LOCKED(base); 1324 if (!base->server_head) return NULL; 1325 1326 /* if we don't have any good nameservers then there's no */ 1327 /* point in trying to find one. */ 1328 if (!base->global_good_nameservers) { 1329 base->server_head = base->server_head->next; 1330 return base->server_head; 1331 } 1332 1333 /* remember that nameservers are in a circular list */ 1334 for (;;) { 1335 if (base->server_head->state) { 1336 /* we think this server is currently good */ 1337 picked = base->server_head; 1338 base->server_head = base->server_head->next; 1339 return picked; 1340 } 1341 1342 base->server_head = base->server_head->next; 1343 if (base->server_head == started_at) { 1344 /* all the nameservers seem to be down */ 1345 /* so we just return this one and hope for the */ 1346 /* best */ 1347 EVUTIL_ASSERT(base->global_good_nameservers == 0); 1348 picked = base->server_head; 1349 base->server_head = base->server_head->next; 1350 return picked; 1351 } 1352 } 1353 } 1354 1355 /* this is called when a namesever socket is ready for reading */ 1356 static void 1357 nameserver_read(struct nameserver *ns) { 1358 struct sockaddr_storage ss; 1359 ev_socklen_t addrlen = sizeof(ss); 1360 u8 packet[1500]; 1361 char addrbuf[128]; 1362 ASSERT_LOCKED(ns->base); 1363 1364 for (;;) { 1365 const int r = recvfrom(ns->socket, (void*)packet, 1366 sizeof(packet), 0, 1367 (struct sockaddr*)&ss, &addrlen); 1368 if (r < 0) { 1369 int err = evutil_socket_geterror(ns->socket); 1370 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1371 return; 1372 nameserver_failed(ns, 1373 evutil_socket_error_to_string(err)); 1374 return; 1375 } 1376 if (evutil_sockaddr_cmp((struct sockaddr*)&ss, 1377 (struct sockaddr*)&ns->address, 0)) { 1378 log(EVDNS_LOG_WARN, "Address mismatch on received " 1379 "DNS packet. Apparent source was %s", 1380 evutil_format_sockaddr_port( 1381 (struct sockaddr *)&ss, 1382 addrbuf, sizeof(addrbuf))); 1383 return; 1384 } 1385 1386 ns->timedout = 0; 1387 reply_parse(ns->base, packet, r); 1388 } 1389 } 1390 1391 /* Read a packet from a DNS client on a server port s, parse it, and */ 1392 /* act accordingly. */ 1393 static void 1394 server_port_read(struct evdns_server_port *s) { 1395 u8 packet[1500]; 1396 struct sockaddr_storage addr; 1397 ev_socklen_t addrlen; 1398 int r; 1399 ASSERT_LOCKED(s); 1400 1401 for (;;) { 1402 addrlen = sizeof(struct sockaddr_storage); 1403 r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0, 1404 (struct sockaddr*) &addr, &addrlen); 1405 if (r < 0) { 1406 int err = evutil_socket_geterror(s->socket); 1407 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1408 return; 1409 log(EVDNS_LOG_WARN, 1410 "Error %s (%d) while reading request.", 1411 evutil_socket_error_to_string(err), err); 1412 return; 1413 } 1414 request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); 1415 } 1416 } 1417 1418 /* Try to write all pending replies on a given DNS server port. */ 1419 static void 1420 server_port_flush(struct evdns_server_port *port) 1421 { 1422 struct server_request *req = port->pending_replies; 1423 ASSERT_LOCKED(port); 1424 while (req) { 1425 int r = sendto(port->socket, req->response, (int)req->response_len, 0, 1426 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1427 if (r < 0) { 1428 int err = evutil_socket_geterror(port->socket); 1429 if (EVUTIL_ERR_RW_RETRIABLE(err)) 1430 return; 1431 log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err); 1432 } 1433 if (server_request_free(req)) { 1434 /* we released the last reference to req->port. */ 1435 return; 1436 } else { 1437 EVUTIL_ASSERT(req != port->pending_replies); 1438 req = port->pending_replies; 1439 } 1440 } 1441 1442 /* We have no more pending requests; stop listening for 'writeable' events. */ 1443 (void) event_del(&port->event); 1444 event_assign(&port->event, port->event_base, 1445 port->socket, EV_READ | EV_PERSIST, 1446 server_port_ready_callback, port); 1447 1448 if (event_add(&port->event, NULL) < 0) { 1449 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); 1450 /* ???? Do more? */ 1451 } 1452 } 1453 1454 /* set if we are waiting for the ability to write to this server. */ 1455 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ 1456 /* we stop these events. */ 1457 static void 1458 nameserver_write_waiting(struct nameserver *ns, char waiting) { 1459 ASSERT_LOCKED(ns->base); 1460 if (ns->write_waiting == waiting) return; 1461 1462 ns->write_waiting = waiting; 1463 (void) event_del(&ns->event); 1464 event_assign(&ns->event, ns->base->event_base, 1465 ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, 1466 nameserver_ready_callback, ns); 1467 if (event_add(&ns->event, NULL) < 0) { 1468 char addrbuf[128]; 1469 log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", 1470 evutil_format_sockaddr_port( 1471 (struct sockaddr *)&ns->address, 1472 addrbuf, sizeof(addrbuf))); 1473 /* ???? Do more? */ 1474 } 1475 } 1476 1477 /* a callback function. Called by libevent when the kernel says that */ 1478 /* a nameserver socket is ready for writing or reading */ 1479 static void 1480 nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) { 1481 struct nameserver *ns = (struct nameserver *) arg; 1482 (void)fd; 1483 1484 EVDNS_LOCK(ns->base); 1485 if (events & EV_WRITE) { 1486 ns->choked = 0; 1487 if (!evdns_transmit(ns->base)) { 1488 nameserver_write_waiting(ns, 0); 1489 } 1490 } 1491 if (events & EV_READ) { 1492 nameserver_read(ns); 1493 } 1494 EVDNS_UNLOCK(ns->base); 1495 } 1496 1497 /* a callback function. Called by libevent when the kernel says that */ 1498 /* a server socket is ready for writing or reading. */ 1499 static void 1500 server_port_ready_callback(evutil_socket_t fd, short events, void *arg) { 1501 struct evdns_server_port *port = (struct evdns_server_port *) arg; 1502 (void) fd; 1503 1504 EVDNS_LOCK(port); 1505 if (events & EV_WRITE) { 1506 port->choked = 0; 1507 server_port_flush(port); 1508 } 1509 if (events & EV_READ) { 1510 server_port_read(port); 1511 } 1512 EVDNS_UNLOCK(port); 1513 } 1514 1515 /* This is an inefficient representation; only use it via the dnslabel_table_* 1516 * functions, so that is can be safely replaced with something smarter later. */ 1517 #define MAX_LABELS 128 1518 /* Structures used to implement name compression */ 1519 struct dnslabel_entry { char *v; off_t pos; }; 1520 struct dnslabel_table { 1521 int n_labels; /* number of current entries */ 1522 /* map from name to position in message */ 1523 struct dnslabel_entry labels[MAX_LABELS]; 1524 }; 1525 1526 /* Initialize dnslabel_table. */ 1527 static void 1528 dnslabel_table_init(struct dnslabel_table *table) 1529 { 1530 table->n_labels = 0; 1531 } 1532 1533 /* Free all storage held by table, but not the table itself. */ 1534 static void 1535 dnslabel_clear(struct dnslabel_table *table) 1536 { 1537 int i; 1538 for (i = 0; i < table->n_labels; ++i) 1539 mm_free(table->labels[i].v); 1540 table->n_labels = 0; 1541 } 1542 1543 /* return the position of the label in the current message, or -1 if the label */ 1544 /* hasn't been used yet. */ 1545 static int 1546 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) 1547 { 1548 int i; 1549 for (i = 0; i < table->n_labels; ++i) { 1550 if (!strcmp(label, table->labels[i].v)) 1551 return table->labels[i].pos; 1552 } 1553 return -1; 1554 } 1555 1556 /* remember that we've used the label at position pos */ 1557 static int 1558 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) 1559 { 1560 char *v; 1561 int p; 1562 if (table->n_labels == MAX_LABELS) 1563 return (-1); 1564 v = mm_strdup(label); 1565 if (v == NULL) 1566 return (-1); 1567 p = table->n_labels++; 1568 table->labels[p].v = v; 1569 table->labels[p].pos = pos; 1570 1571 return (0); 1572 } 1573 1574 /* Converts a string to a length-prefixed set of DNS labels, starting */ 1575 /* at buf[j]. name and buf must not overlap. name_len should be the length */ 1576 /* of name. table is optional, and is used for compression. */ 1577 /* */ 1578 /* Input: abc.def */ 1579 /* Output: <3>abc<3>def<0> */ 1580 /* */ 1581 /* Returns the first index after the encoded name, or negative on error. */ 1582 /* -1 label was > 63 bytes */ 1583 /* -2 name too long to fit in buffer. */ 1584 /* */ 1585 static off_t 1586 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, 1587 const char *name, const size_t name_len, 1588 struct dnslabel_table *table) { 1589 const char *end = name + name_len; 1590 int ref = 0; 1591 u16 _t; 1592 1593 #define APPEND16(x) do { \ 1594 if (j + 2 > (off_t)buf_len) \ 1595 goto overflow; \ 1596 _t = htons(x); \ 1597 memcpy(buf + j, &_t, 2); \ 1598 j += 2; \ 1599 } while (0) 1600 #define APPEND32(x) do { \ 1601 if (j + 4 > (off_t)buf_len) \ 1602 goto overflow; \ 1603 _t32 = htonl(x); \ 1604 memcpy(buf + j, &_t32, 4); \ 1605 j += 4; \ 1606 } while (0) 1607 1608 if (name_len > 255) return -2; 1609 1610 for (;;) { 1611 const char *const start = name; 1612 if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { 1613 APPEND16(ref | 0xc000); 1614 return j; 1615 } 1616 name = strchr(name, '.'); 1617 if (!name) { 1618 const size_t label_len = end - start; 1619 if (label_len > 63) return -1; 1620 if ((size_t)(j+label_len+1) > buf_len) return -2; 1621 if (table) dnslabel_table_add(table, start, j); 1622 buf[j++] = (ev_uint8_t)label_len; 1623 1624 memcpy(buf + j, start, label_len); 1625 j += (int) label_len; 1626 break; 1627 } else { 1628 /* append length of the label. */ 1629 const size_t label_len = name - start; 1630 if (label_len > 63) return -1; 1631 if ((size_t)(j+label_len+1) > buf_len) return -2; 1632 if (table) dnslabel_table_add(table, start, j); 1633 buf[j++] = (ev_uint8_t)label_len; 1634 1635 memcpy(buf + j, start, label_len); 1636 j += (int) label_len; 1637 /* hop over the '.' */ 1638 name++; 1639 } 1640 } 1641 1642 /* the labels must be terminated by a 0. */ 1643 /* It's possible that the name ended in a . */ 1644 /* in which case the zero is already there */ 1645 if (!j || buf[j-1]) buf[j++] = 0; 1646 return j; 1647 overflow: 1648 return (-2); 1649 } 1650 1651 /* Finds the length of a dns request for a DNS name of the given */ 1652 /* length. The actual request may be smaller than the value returned */ 1653 /* here */ 1654 static size_t 1655 evdns_request_len(const size_t name_len) { 1656 return 96 + /* length of the DNS standard header */ 1657 name_len + 2 + 1658 4; /* space for the resource type */ 1659 } 1660 1661 /* build a dns request packet into buf. buf should be at least as long */ 1662 /* as evdns_request_len told you it should be. */ 1663 /* */ 1664 /* Returns the amount of space used. Negative on error. */ 1665 static int 1666 evdns_request_data_build(const char *const name, const size_t name_len, 1667 const u16 trans_id, const u16 type, const u16 class, 1668 u8 *const buf, size_t buf_len) { 1669 off_t j = 0; /* current offset into buf */ 1670 u16 _t; /* used by the macros */ 1671 1672 APPEND16(trans_id); 1673 APPEND16(0x0100); /* standard query, recusion needed */ 1674 APPEND16(1); /* one question */ 1675 APPEND16(0); /* no answers */ 1676 APPEND16(0); /* no authority */ 1677 APPEND16(0); /* no additional */ 1678 1679 j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); 1680 if (j < 0) { 1681 return (int)j; 1682 } 1683 1684 APPEND16(type); 1685 APPEND16(class); 1686 1687 return (int)j; 1688 overflow: 1689 return (-1); 1690 } 1691 1692 /* exported function */ 1693 struct evdns_server_port * 1694 evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) 1695 { 1696 struct evdns_server_port *port; 1697 if (flags) 1698 return NULL; /* flags not yet implemented */ 1699 if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) 1700 return NULL; 1701 memset(port, 0, sizeof(struct evdns_server_port)); 1702 1703 1704 port->socket = socket; 1705 port->refcnt = 1; 1706 port->choked = 0; 1707 port->closing = 0; 1708 port->user_callback = cb; 1709 port->user_data = user_data; 1710 port->pending_replies = NULL; 1711 port->event_base = base; 1712 1713 event_assign(&port->event, port->event_base, 1714 port->socket, EV_READ | EV_PERSIST, 1715 server_port_ready_callback, port); 1716 if (event_add(&port->event, NULL) < 0) { 1717 mm_free(port); 1718 return NULL; 1719 } 1720 EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 1721 return port; 1722 } 1723 1724 struct evdns_server_port * 1725 evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) 1726 { 1727 return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data); 1728 } 1729 1730 /* exported function */ 1731 void 1732 evdns_close_server_port(struct evdns_server_port *port) 1733 { 1734 EVDNS_LOCK(port); 1735 if (--port->refcnt == 0) { 1736 EVDNS_UNLOCK(port); 1737 server_port_free(port); 1738 } else { 1739 port->closing = 1; 1740 } 1741 } 1742 1743 /* exported function */ 1744 int 1745 evdns_server_request_add_reply(struct evdns_server_request *_req, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data) 1746 { 1747 struct server_request *req = TO_SERVER_REQUEST(_req); 1748 struct server_reply_item **itemp, *item; 1749 int *countp; 1750 int result = -1; 1751 1752 EVDNS_LOCK(req->port); 1753 if (req->response) /* have we already answered? */ 1754 goto done; 1755 1756 switch (section) { 1757 case EVDNS_ANSWER_SECTION: 1758 itemp = &req->answer; 1759 countp = &req->n_answer; 1760 break; 1761 case EVDNS_AUTHORITY_SECTION: 1762 itemp = &req->authority; 1763 countp = &req->n_authority; 1764 break; 1765 case EVDNS_ADDITIONAL_SECTION: 1766 itemp = &req->additional; 1767 countp = &req->n_additional; 1768 break; 1769 default: 1770 goto done; 1771 } 1772 while (*itemp) { 1773 itemp = &((*itemp)->next); 1774 } 1775 item = mm_malloc(sizeof(struct server_reply_item)); 1776 if (!item) 1777 goto done; 1778 item->next = NULL; 1779 if (!(item->name = mm_strdup(name))) { 1780 mm_free(item); 1781 goto done; 1782 } 1783 item->type = type; 1784 item->dns_question_class = class; 1785 item->ttl = ttl; 1786 item->is_name = is_name != 0; 1787 item->datalen = 0; 1788 item->data = NULL; 1789 if (data) { 1790 if (item->is_name) { 1791 if (!(item->data = mm_strdup(data))) { 1792 mm_free(item->name); 1793 mm_free(item); 1794 goto done; 1795 } 1796 item->datalen = (u16)-1; 1797 } else { 1798 if (!(item->data = mm_malloc(datalen))) { 1799 mm_free(item->name); 1800 mm_free(item); 1801 goto done; 1802 } 1803 item->datalen = datalen; 1804 memcpy(item->data, data, datalen); 1805 } 1806 } 1807 1808 *itemp = item; 1809 ++(*countp); 1810 result = 0; 1811 done: 1812 EVDNS_UNLOCK(req->port); 1813 return result; 1814 } 1815 1816 /* exported function */ 1817 int 1818 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1819 { 1820 return evdns_server_request_add_reply( 1821 req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, 1822 ttl, n*4, 0, addrs); 1823 } 1824 1825 /* exported function */ 1826 int 1827 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) 1828 { 1829 return evdns_server_request_add_reply( 1830 req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, 1831 ttl, n*16, 0, addrs); 1832 } 1833 1834 /* exported function */ 1835 int 1836 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) 1837 { 1838 u32 a; 1839 char buf[32]; 1840 if (in && inaddr_name) 1841 return -1; 1842 else if (!in && !inaddr_name) 1843 return -1; 1844 if (in) { 1845 a = ntohl(in->s_addr); 1846 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 1847 (int)(u8)((a )&0xff), 1848 (int)(u8)((a>>8 )&0xff), 1849 (int)(u8)((a>>16)&0xff), 1850 (int)(u8)((a>>24)&0xff)); 1851 inaddr_name = buf; 1852 } 1853 return evdns_server_request_add_reply( 1854 req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, 1855 ttl, -1, 1, hostname); 1856 } 1857 1858 /* exported function */ 1859 int 1860 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) 1861 { 1862 return evdns_server_request_add_reply( 1863 req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, 1864 ttl, -1, 1, cname); 1865 } 1866 1867 /* exported function */ 1868 void 1869 evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags) 1870 { 1871 struct server_request *req = TO_SERVER_REQUEST(exreq); 1872 req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD); 1873 req->base.flags |= flags; 1874 } 1875 1876 static int 1877 evdns_server_request_format_response(struct server_request *req, int err) 1878 { 1879 unsigned char buf[1500]; 1880 size_t buf_len = sizeof(buf); 1881 off_t j = 0, r; 1882 u16 _t; 1883 u32 _t32; 1884 int i; 1885 u16 flags; 1886 struct dnslabel_table table; 1887 1888 if (err < 0 || err > 15) return -1; 1889 1890 /* Set response bit and error code; copy OPCODE and RD fields from 1891 * question; copy RA and AA if set by caller. */ 1892 flags = req->base.flags; 1893 flags |= (0x8000 | err); 1894 1895 dnslabel_table_init(&table); 1896 APPEND16(req->trans_id); 1897 APPEND16(flags); 1898 APPEND16(req->base.nquestions); 1899 APPEND16(req->n_answer); 1900 APPEND16(req->n_authority); 1901 APPEND16(req->n_additional); 1902 1903 /* Add questions. */ 1904 for (i=0; i < req->base.nquestions; ++i) { 1905 const char *s = req->base.questions[i]->name; 1906 j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); 1907 if (j < 0) { 1908 dnslabel_clear(&table); 1909 return (int) j; 1910 } 1911 APPEND16(req->base.questions[i]->type); 1912 APPEND16(req->base.questions[i]->dns_question_class); 1913 } 1914 1915 /* Add answer, authority, and additional sections. */ 1916 for (i=0; i<3; ++i) { 1917 struct server_reply_item *item; 1918 if (i==0) 1919 item = req->answer; 1920 else if (i==1) 1921 item = req->authority; 1922 else 1923 item = req->additional; 1924 while (item) { 1925 r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); 1926 if (r < 0) 1927 goto overflow; 1928 j = r; 1929 1930 APPEND16(item->type); 1931 APPEND16(item->dns_question_class); 1932 APPEND32(item->ttl); 1933 if (item->is_name) { 1934 off_t len_idx = j, name_start; 1935 j += 2; 1936 name_start = j; 1937 r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); 1938 if (r < 0) 1939 goto overflow; 1940 j = r; 1941 _t = htons( (short) (j-name_start) ); 1942 memcpy(buf+len_idx, &_t, 2); 1943 } else { 1944 APPEND16(item->datalen); 1945 if (j+item->datalen > (off_t)buf_len) 1946 goto overflow; 1947 memcpy(buf+j, item->data, item->datalen); 1948 j += item->datalen; 1949 } 1950 item = item->next; 1951 } 1952 } 1953 1954 if (j > 512) { 1955 overflow: 1956 j = 512; 1957 buf[2] |= 0x02; /* set the truncated bit. */ 1958 } 1959 1960 req->response_len = j; 1961 1962 if (!(req->response = mm_malloc(req->response_len))) { 1963 server_request_free_answers(req); 1964 dnslabel_clear(&table); 1965 return (-1); 1966 } 1967 memcpy(req->response, buf, req->response_len); 1968 server_request_free_answers(req); 1969 dnslabel_clear(&table); 1970 return (0); 1971 } 1972 1973 /* exported function */ 1974 int 1975 evdns_server_request_respond(struct evdns_server_request *_req, int err) 1976 { 1977 struct server_request *req = TO_SERVER_REQUEST(_req); 1978 struct evdns_server_port *port = req->port; 1979 int r = -1; 1980 1981 EVDNS_LOCK(port); 1982 if (!req->response) { 1983 if ((r = evdns_server_request_format_response(req, err))<0) 1984 goto done; 1985 } 1986 1987 r = sendto(port->socket, req->response, (int)req->response_len, 0, 1988 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); 1989 if (r<0) { 1990 int sock_err = evutil_socket_geterror(port->socket); 1991 if (EVUTIL_ERR_RW_RETRIABLE(sock_err)) 1992 goto done; 1993 1994 if (port->pending_replies) { 1995 req->prev_pending = port->pending_replies->prev_pending; 1996 req->next_pending = port->pending_replies; 1997 req->prev_pending->next_pending = 1998 req->next_pending->prev_pending = req; 1999 } else { 2000 req->prev_pending = req->next_pending = req; 2001 port->pending_replies = req; 2002 port->choked = 1; 2003 2004 (void) event_del(&port->event); 2005 event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); 2006 2007 if (event_add(&port->event, NULL) < 0) { 2008 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); 2009 } 2010 2011 } 2012 2013 r = 1; 2014 goto done; 2015 } 2016 if (server_request_free(req)) { 2017 r = 0; 2018 goto done; 2019 } 2020 2021 if (port->pending_replies) 2022 server_port_flush(port); 2023 2024 r = 0; 2025 done: 2026 EVDNS_UNLOCK(port); 2027 return r; 2028 } 2029 2030 /* Free all storage held by RRs in req. */ 2031 static void 2032 server_request_free_answers(struct server_request *req) 2033 { 2034 struct server_reply_item *victim, *next, **list; 2035 int i; 2036 for (i = 0; i < 3; ++i) { 2037 if (i==0) 2038 list = &req->answer; 2039 else if (i==1) 2040 list = &req->authority; 2041 else 2042 list = &req->additional; 2043 2044 victim = *list; 2045 while (victim) { 2046 next = victim->next; 2047 mm_free(victim->name); 2048 if (victim->data) 2049 mm_free(victim->data); 2050 mm_free(victim); 2051 victim = next; 2052 } 2053 *list = NULL; 2054 } 2055 } 2056 2057 /* Free all storage held by req, and remove links to it. */ 2058 /* return true iff we just wound up freeing the server_port. */ 2059 static int 2060 server_request_free(struct server_request *req) 2061 { 2062 int i, rc=1, lock=0; 2063 if (req->base.questions) { 2064 for (i = 0; i < req->base.nquestions; ++i) 2065 mm_free(req->base.questions[i]); 2066 mm_free(req->base.questions); 2067 } 2068 2069 if (req->port) { 2070 EVDNS_LOCK(req->port); 2071 lock=1; 2072 if (req->port->pending_replies == req) { 2073 if (req->next_pending && req->next_pending != req) 2074 req->port->pending_replies = req->next_pending; 2075 else 2076 req->port->pending_replies = NULL; 2077 } 2078 rc = --req->port->refcnt; 2079 } 2080 2081 if (req->response) { 2082 mm_free(req->response); 2083 } 2084 2085 server_request_free_answers(req); 2086 2087 if (req->next_pending && req->next_pending != req) { 2088 req->next_pending->prev_pending = req->prev_pending; 2089 req->prev_pending->next_pending = req->next_pending; 2090 } 2091 2092 if (rc == 0) { 2093 EVDNS_UNLOCK(req->port); /* ????? nickm */ 2094 server_port_free(req->port); 2095 mm_free(req); 2096 return (1); 2097 } 2098 if (lock) 2099 EVDNS_UNLOCK(req->port); 2100 mm_free(req); 2101 return (0); 2102 } 2103 2104 /* Free all storage held by an evdns_server_port. Only called when */ 2105 static void 2106 server_port_free(struct evdns_server_port *port) 2107 { 2108 EVUTIL_ASSERT(port); 2109 EVUTIL_ASSERT(!port->refcnt); 2110 EVUTIL_ASSERT(!port->pending_replies); 2111 if (port->socket > 0) { 2112 evutil_closesocket(port->socket); 2113 port->socket = -1; 2114 } 2115 (void) event_del(&port->event); 2116 event_debug_unassign(&port->event); 2117 EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 2118 mm_free(port); 2119 } 2120 2121 /* exported function */ 2122 int 2123 evdns_server_request_drop(struct evdns_server_request *_req) 2124 { 2125 struct server_request *req = TO_SERVER_REQUEST(_req); 2126 server_request_free(req); 2127 return 0; 2128 } 2129 2130 /* exported function */ 2131 int 2132 evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len) 2133 { 2134 struct server_request *req = TO_SERVER_REQUEST(_req); 2135 if (addr_len < (int)req->addrlen) 2136 return -1; 2137 memcpy(sa, &(req->addr), req->addrlen); 2138 return req->addrlen; 2139 } 2140 2141 #undef APPEND16 2142 #undef APPEND32 2143 2144 /* this is a libevent callback function which is called when a request */ 2145 /* has timed out. */ 2146 static void 2147 evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) { 2148 struct request *const req = (struct request *) arg; 2149 struct evdns_base *base = req->base; 2150 2151 (void) fd; 2152 (void) events; 2153 2154 log(EVDNS_LOG_DEBUG, "Request %p timed out", arg); 2155 EVDNS_LOCK(base); 2156 2157 req->ns->timedout++; 2158 if (req->ns->timedout > req->base->global_max_nameserver_timeout) { 2159 req->ns->timedout = 0; 2160 nameserver_failed(req->ns, "request timed out."); 2161 } 2162 2163 if (req->tx_count >= req->base->global_max_retransmits) { 2164 /* this request has failed */ 2165 log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d", 2166 arg, req->tx_count); 2167 reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL); 2168 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); 2169 } else { 2170 /* retransmit it */ 2171 struct nameserver *new_ns; 2172 log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d", 2173 arg, req->tx_count); 2174 (void) evtimer_del(&req->timeout_event); 2175 new_ns = nameserver_pick(base); 2176 if (new_ns) 2177 req->ns = new_ns; 2178 evdns_request_transmit(req); 2179 } 2180 EVDNS_UNLOCK(base); 2181 } 2182 2183 /* try to send a request to a given server. */ 2184 /* */ 2185 /* return: */ 2186 /* 0 ok */ 2187 /* 1 temporary failure */ 2188 /* 2 other failure */ 2189 static int 2190 evdns_request_transmit_to(struct request *req, struct nameserver *server) { 2191 int r; 2192 ASSERT_LOCKED(req->base); 2193 ASSERT_VALID_REQUEST(req); 2194 r = sendto(server->socket, (void*)req->request, req->request_len, 0, 2195 (struct sockaddr *)&server->address, server->addrlen); 2196 if (r < 0) { 2197 int err = evutil_socket_geterror(server->socket); 2198 if (EVUTIL_ERR_RW_RETRIABLE(err)) 2199 return 1; 2200 nameserver_failed(req->ns, evutil_socket_error_to_string(err)); 2201 return 2; 2202 } else if (r != (int)req->request_len) { 2203 return 1; /* short write */ 2204 } else { 2205 return 0; 2206 } 2207 } 2208 2209 /* try to send a request, updating the fields of the request */ 2210 /* as needed */ 2211 /* */ 2212 /* return: */ 2213 /* 0 ok */ 2214 /* 1 failed */ 2215 static int 2216 evdns_request_transmit(struct request *req) { 2217 int retcode = 0, r; 2218 2219 ASSERT_LOCKED(req->base); 2220 ASSERT_VALID_REQUEST(req); 2221 /* if we fail to send this packet then this flag marks it */ 2222 /* for evdns_transmit */ 2223 req->transmit_me = 1; 2224 EVUTIL_ASSERT(req->trans_id != 0xffff); 2225 2226 if (!req->ns) 2227 { 2228 /* unable to transmit request if no nameservers */ 2229 return 1; 2230 } 2231 2232 if (req->ns->choked) { 2233 /* don't bother trying to write to a socket */ 2234 /* which we have had EAGAIN from */ 2235 return 1; 2236 } 2237 2238 r = evdns_request_transmit_to(req, req->ns); 2239 switch (r) { 2240 case 1: 2241 /* temp failure */ 2242 req->ns->choked = 1; 2243 nameserver_write_waiting(req->ns, 1); 2244 return 1; 2245 case 2: 2246 /* failed to transmit the request entirely. */ 2247 retcode = 1; 2248 /* fall through: we'll set a timeout, which will time out, 2249 * and make us retransmit the request anyway. */ 2250 default: 2251 /* all ok */ 2252 log(EVDNS_LOG_DEBUG, 2253 "Setting timeout for request %p, sent to nameserver %p", req, req->ns); 2254 if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) { 2255 log(EVDNS_LOG_WARN, 2256 "Error from libevent when adding timer for request %p", 2257 req); 2258 /* ???? Do more? */ 2259 } 2260 req->tx_count++; 2261 req->transmit_me = 0; 2262 return retcode; 2263 } 2264 } 2265 2266 static void 2267 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { 2268 struct nameserver *const ns = (struct nameserver *) arg; 2269 (void) type; 2270 (void) count; 2271 (void) ttl; 2272 (void) addresses; 2273 2274 if (result == DNS_ERR_CANCEL) { 2275 /* We canceled this request because the nameserver came up 2276 * for some other reason. Do not change our opinion about 2277 * the nameserver. */ 2278 return; 2279 } 2280 2281 EVDNS_LOCK(ns->base); 2282 ns->probe_request = NULL; 2283 if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { 2284 /* this is a good reply */ 2285 nameserver_up(ns); 2286 } else { 2287 nameserver_probe_failed(ns); 2288 } 2289 EVDNS_UNLOCK(ns->base); 2290 } 2291 2292 static void 2293 nameserver_send_probe(struct nameserver *const ns) { 2294 struct evdns_request *handle; 2295 struct request *req; 2296 char addrbuf[128]; 2297 /* here we need to send a probe to a given nameserver */ 2298 /* in the hope that it is up now. */ 2299 2300 ASSERT_LOCKED(ns->base); 2301 log(EVDNS_LOG_DEBUG, "Sending probe to %s", 2302 evutil_format_sockaddr_port( 2303 (struct sockaddr *)&ns->address, 2304 addrbuf, sizeof(addrbuf))); 2305 handle = mm_calloc(1, sizeof(*handle)); 2306 if (!handle) return; 2307 req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); 2308 if (!req) { 2309 mm_free(handle); 2310 return; 2311 } 2312 ns->probe_request = handle; 2313 /* we force this into the inflight queue no matter what */ 2314 request_trans_id_set(req, transaction_id_pick(ns->base)); 2315 req->ns = ns; 2316 request_submit(req); 2317 } 2318 2319 /* returns: */ 2320 /* 0 didn't try to transmit anything */ 2321 /* 1 tried to transmit something */ 2322 static int 2323 evdns_transmit(struct evdns_base *base) { 2324 char did_try_to_transmit = 0; 2325 int i; 2326 2327 ASSERT_LOCKED(base); 2328 for (i = 0; i < base->n_req_heads; ++i) { 2329 if (base->req_heads[i]) { 2330 struct request *const started_at = base->req_heads[i], *req = started_at; 2331 /* first transmit all the requests which are currently waiting */ 2332 do { 2333 if (req->transmit_me) { 2334 did_try_to_transmit = 1; 2335 evdns_request_transmit(req); 2336 } 2337 2338 req = req->next; 2339 } while (req != started_at); 2340 } 2341 } 2342 2343 return did_try_to_transmit; 2344 } 2345 2346 /* exported function */ 2347 int 2348 evdns_base_count_nameservers(struct evdns_base *base) 2349 { 2350 const struct nameserver *server; 2351 int n = 0; 2352 2353 EVDNS_LOCK(base); 2354 server = base->server_head; 2355 if (!server) 2356 goto done; 2357 do { 2358 ++n; 2359 server = server->next; 2360 } while (server != base->server_head); 2361 done: 2362 EVDNS_UNLOCK(base); 2363 return n; 2364 } 2365 2366 int 2367 evdns_count_nameservers(void) 2368 { 2369 return evdns_base_count_nameservers(current_base); 2370 } 2371 2372 /* exported function */ 2373 int 2374 evdns_base_clear_nameservers_and_suspend(struct evdns_base *base) 2375 { 2376 struct nameserver *server, *started_at; 2377 int i; 2378 2379 EVDNS_LOCK(base); 2380 server = base->server_head; 2381 started_at = base->server_head; 2382 if (!server) { 2383 EVDNS_UNLOCK(base); 2384 return 0; 2385 } 2386 while (1) { 2387 struct nameserver *next = server->next; 2388 (void) event_del(&server->event); 2389 if (evtimer_initialized(&server->timeout_event)) 2390 (void) evtimer_del(&server->timeout_event); 2391 if (server->probe_request) { 2392 evdns_cancel_request(server->base, server->probe_request); 2393 server->probe_request = NULL; 2394 } 2395 if (server->socket >= 0) 2396 evutil_closesocket(server->socket); 2397 mm_free(server); 2398 if (next == started_at) 2399 break; 2400 server = next; 2401 } 2402 base->server_head = NULL; 2403 base->global_good_nameservers = 0; 2404 2405 for (i = 0; i < base->n_req_heads; ++i) { 2406 struct request *req, *req_started_at; 2407 req = req_started_at = base->req_heads[i]; 2408 while (req) { 2409 struct request *next = req->next; 2410 req->tx_count = req->reissue_count = 0; 2411 req->ns = NULL; 2412 /* ???? What to do about searches? */ 2413 (void) evtimer_del(&req->timeout_event); 2414 req->trans_id = 0; 2415 req->transmit_me = 0; 2416 2417 base->global_requests_waiting++; 2418 evdns_request_insert(req, &base->req_waiting_head); 2419 /* We want to insert these suspended elements at the front of 2420 * the waiting queue, since they were pending before any of 2421 * the waiting entries were added. This is a circular list, 2422 * so we can just shift the start back by one.*/ 2423 base->req_waiting_head = base->req_waiting_head->prev; 2424 2425 if (next == req_started_at) 2426 break; 2427 req = next; 2428 } 2429 base->req_heads[i] = NULL; 2430 } 2431 2432 base->global_requests_inflight = 0; 2433 2434 EVDNS_UNLOCK(base); 2435 return 0; 2436 } 2437 2438 int 2439 evdns_clear_nameservers_and_suspend(void) 2440 { 2441 return evdns_base_clear_nameservers_and_suspend(current_base); 2442 } 2443 2444 2445 /* exported function */ 2446 int 2447 evdns_base_resume(struct evdns_base *base) 2448 { 2449 EVDNS_LOCK(base); 2450 evdns_requests_pump_waiting_queue(base); 2451 EVDNS_UNLOCK(base); 2452 2453 return 0; 2454 } 2455 2456 int 2457 evdns_resume(void) 2458 { 2459 return evdns_base_resume(current_base); 2460 } 2461 2462 static int 2463 _evdns_nameserver_add_impl(struct evdns_base *base, const struct sockaddr *address, int addrlen) { 2464 /* first check to see if we already have this nameserver */ 2465 2466 const struct nameserver *server = base->server_head, *const started_at = base->server_head; 2467 struct nameserver *ns; 2468 int err = 0; 2469 char addrbuf[128]; 2470 2471 ASSERT_LOCKED(base); 2472 if (server) { 2473 do { 2474 if (!evutil_sockaddr_cmp((struct sockaddr*)&server->address, address, 1)) return 3; 2475 server = server->next; 2476 } while (server != started_at); 2477 } 2478 if (addrlen > (int)sizeof(ns->address)) { 2479 log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); 2480 return 2; 2481 } 2482 2483 ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); 2484 if (!ns) return -1; 2485 2486 memset(ns, 0, sizeof(struct nameserver)); 2487 ns->base = base; 2488 2489 evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns); 2490 2491 ns->socket = socket(address->sa_family, SOCK_DGRAM, 0); 2492 if (ns->socket < 0) { err = 1; goto out1; } 2493 evutil_make_socket_closeonexec(ns->socket); 2494 evutil_make_socket_nonblocking(ns->socket); 2495 2496 if (base->global_outgoing_addrlen && 2497 !evutil_sockaddr_is_loopback(address)) { 2498 if (bind(ns->socket, 2499 (struct sockaddr*)&base->global_outgoing_address, 2500 base->global_outgoing_addrlen) < 0) { 2501 log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address"); 2502 err = 2; 2503 goto out2; 2504 } 2505 } 2506 2507 memcpy(&ns->address, address, addrlen); 2508 ns->addrlen = addrlen; 2509 ns->state = 1; 2510 event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); 2511 if (event_add(&ns->event, NULL) < 0) { 2512 err = 2; 2513 goto out2; 2514 } 2515 2516 log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p", 2517 evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), ns); 2518 2519 /* insert this nameserver into the list of them */ 2520 if (!base->server_head) { 2521 ns->next = ns->prev = ns; 2522 base->server_head = ns; 2523 } else { 2524 ns->next = base->server_head->next; 2525 ns->prev = base->server_head; 2526 base->server_head->next = ns; 2527 ns->next->prev = ns; 2528 } 2529 2530 base->global_good_nameservers++; 2531 2532 return 0; 2533 2534 out2: 2535 evutil_closesocket(ns->socket); 2536 out1: 2537 event_debug_unassign(&ns->event); 2538 mm_free(ns); 2539 log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", 2540 evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), err); 2541 return err; 2542 } 2543 2544 /* exported function */ 2545 int 2546 evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address) 2547 { 2548 struct sockaddr_in sin; 2549 int res; 2550 memset(&sin, 0, sizeof(sin)); 2551 sin.sin_addr.s_addr = address; 2552 sin.sin_port = htons(53); 2553 sin.sin_family = AF_INET; 2554 EVDNS_LOCK(base); 2555 res = _evdns_nameserver_add_impl(base, (struct sockaddr*)&sin, sizeof(sin)); 2556 EVDNS_UNLOCK(base); 2557 return res; 2558 } 2559 2560 int 2561 evdns_nameserver_add(unsigned long int address) { 2562 if (!current_base) 2563 current_base = evdns_base_new(NULL, 0); 2564 return evdns_base_nameserver_add(current_base, address); 2565 } 2566 2567 static void 2568 sockaddr_setport(struct sockaddr *sa, ev_uint16_t port) 2569 { 2570 if (sa->sa_family == AF_INET) { 2571 ((struct sockaddr_in *)sa)->sin_port = htons(port); 2572 } else if (sa->sa_family == AF_INET6) { 2573 ((struct sockaddr_in6 *)sa)->sin6_port = htons(port); 2574 } 2575 } 2576 2577 static ev_uint16_t 2578 sockaddr_getport(struct sockaddr *sa) 2579 { 2580 if (sa->sa_family == AF_INET) { 2581 return ntohs(((struct sockaddr_in *)sa)->sin_port); 2582 } else if (sa->sa_family == AF_INET6) { 2583 return ntohs(((struct sockaddr_in6 *)sa)->sin6_port); 2584 } else { 2585 return 0; 2586 } 2587 } 2588 2589 /* exported function */ 2590 int 2591 evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) { 2592 struct sockaddr_storage ss; 2593 struct sockaddr *sa; 2594 int len = sizeof(ss); 2595 int res; 2596 if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss, 2597 &len)) { 2598 log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s", 2599 ip_as_string); 2600 return 4; 2601 } 2602 sa = (struct sockaddr *) &ss; 2603 if (sockaddr_getport(sa) == 0) 2604 sockaddr_setport(sa, 53); 2605 2606 EVDNS_LOCK(base); 2607 res = _evdns_nameserver_add_impl(base, sa, len); 2608 EVDNS_UNLOCK(base); 2609 return res; 2610 } 2611 2612 int 2613 evdns_nameserver_ip_add(const char *ip_as_string) { 2614 if (!current_base) 2615 current_base = evdns_base_new(NULL, 0); 2616 return evdns_base_nameserver_ip_add(current_base, ip_as_string); 2617 } 2618 2619 int 2620 evdns_base_nameserver_sockaddr_add(struct evdns_base *base, 2621 const struct sockaddr *sa, ev_socklen_t len, unsigned flags) 2622 { 2623 int res; 2624 EVUTIL_ASSERT(base); 2625 EVDNS_LOCK(base); 2626 res = _evdns_nameserver_add_impl(base, sa, len); 2627 EVDNS_UNLOCK(base); 2628 return res; 2629 } 2630 2631 /* remove from the queue */ 2632 static void 2633 evdns_request_remove(struct request *req, struct request **head) 2634 { 2635 ASSERT_LOCKED(req->base); 2636 ASSERT_VALID_REQUEST(req); 2637 2638 #if 0 2639 { 2640 struct request *ptr; 2641 int found = 0; 2642 EVUTIL_ASSERT(*head != NULL); 2643 2644 ptr = *head; 2645 do { 2646 if (ptr == req) { 2647 found = 1; 2648 break; 2649 } 2650 ptr = ptr->next; 2651 } while (ptr != *head); 2652 EVUTIL_ASSERT(found); 2653 2654 EVUTIL_ASSERT(req->next); 2655 } 2656 #endif 2657 2658 if (req->next == req) { 2659 /* only item in the list */ 2660 *head = NULL; 2661 } else { 2662 req->next->prev = req->prev; 2663 req->prev->next = req->next; 2664 if (*head == req) *head = req->next; 2665 } 2666 req->next = req->prev = NULL; 2667 } 2668 2669 /* insert into the tail of the queue */ 2670 static void 2671 evdns_request_insert(struct request *req, struct request **head) { 2672 ASSERT_LOCKED(req->base); 2673 ASSERT_VALID_REQUEST(req); 2674 if (!*head) { 2675 *head = req; 2676 req->next = req->prev = req; 2677 return; 2678 } 2679 2680 req->prev = (*head)->prev; 2681 req->prev->next = req; 2682 req->next = *head; 2683 (*head)->prev = req; 2684 } 2685 2686 static int 2687 string_num_dots(const char *s) { 2688 int count = 0; 2689 while ((s = strchr(s, '.'))) { 2690 s++; 2691 count++; 2692 } 2693 return count; 2694 } 2695 2696 static struct request * 2697 request_new(struct evdns_base *base, struct evdns_request *handle, int type, 2698 const char *name, int flags, evdns_callback_type callback, 2699 void *user_ptr) { 2700 2701 const char issuing_now = 2702 (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0; 2703 2704 const size_t name_len = strlen(name); 2705 const size_t request_max_len = evdns_request_len(name_len); 2706 const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff; 2707 /* the request data is alloced in a single block with the header */ 2708 struct request *const req = 2709 mm_malloc(sizeof(struct request) + request_max_len); 2710 int rlen; 2711 char namebuf[256]; 2712 (void) flags; 2713 2714 ASSERT_LOCKED(base); 2715 2716 if (!req) return NULL; 2717 2718 if (name_len >= sizeof(namebuf)) { 2719 mm_free(req); 2720 return NULL; 2721 } 2722 2723 memset(req, 0, sizeof(struct request)); 2724 req->base = base; 2725 2726 evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req); 2727 2728 if (base->global_randomize_case) { 2729 unsigned i; 2730 char randbits[(sizeof(namebuf)+7)/8]; 2731 strlcpy(namebuf, name, sizeof(namebuf)); 2732 evutil_secure_rng_get_bytes(randbits, (name_len+7)/8); 2733 for (i = 0; i < name_len; ++i) { 2734 if (EVUTIL_ISALPHA(namebuf[i])) { 2735 if ((randbits[i >> 3] & (1<<(i & 7)))) 2736 namebuf[i] |= 0x20; 2737 else 2738 namebuf[i] &= ~0x20; 2739 } 2740 } 2741 name = namebuf; 2742 } 2743 2744 /* request data lives just after the header */ 2745 req->request = ((u8 *) req) + sizeof(struct request); 2746 /* denotes that the request data shouldn't be free()ed */ 2747 req->request_appended = 1; 2748 rlen = evdns_request_data_build(name, name_len, trans_id, 2749 type, CLASS_INET, req->request, request_max_len); 2750 if (rlen < 0) 2751 goto err1; 2752 2753 req->request_len = rlen; 2754 req->trans_id = trans_id; 2755 req->tx_count = 0; 2756 req->request_type = type; 2757 req->user_pointer = user_ptr; 2758 req->user_callback = callback; 2759 req->ns = issuing_now ? nameserver_pick(base) : NULL; 2760 req->next = req->prev = NULL; 2761 req->handle = handle; 2762 if (handle) { 2763 handle->current_req = req; 2764 handle->base = base; 2765 } 2766 2767 return req; 2768 err1: 2769 mm_free(req); 2770 return NULL; 2771 } 2772 2773 static void 2774 request_submit(struct request *const req) { 2775 struct evdns_base *base = req->base; 2776 ASSERT_LOCKED(base); 2777 ASSERT_VALID_REQUEST(req); 2778 if (req->ns) { 2779 /* if it has a nameserver assigned then this is going */ 2780 /* straight into the inflight queue */ 2781 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); 2782 base->global_requests_inflight++; 2783 evdns_request_transmit(req); 2784 } else { 2785 evdns_request_insert(req, &base->req_waiting_head); 2786 base->global_requests_waiting++; 2787 } 2788 } 2789 2790 /* exported function */ 2791 void 2792 evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle) 2793 { 2794 struct request *req; 2795 2796 if (!handle->current_req) 2797 return; 2798 2799 if (!base) { 2800 /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */ 2801 base = handle->base; 2802 if (!base) 2803 base = handle->current_req->base; 2804 } 2805 2806 EVDNS_LOCK(base); 2807 if (handle->pending_cb) { 2808 EVDNS_UNLOCK(base); 2809 return; 2810 } 2811 2812 req = handle->current_req; 2813 ASSERT_VALID_REQUEST(req); 2814 2815 reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL); 2816 if (req->ns) { 2817 /* remove from inflight queue */ 2818 request_finished(req, &REQ_HEAD(base, req->trans_id), 1); 2819 } else { 2820 /* remove from global_waiting head */ 2821 request_finished(req, &base->req_waiting_head, 1); 2822 } 2823 EVDNS_UNLOCK(base); 2824 } 2825 2826 /* exported function */ 2827 struct evdns_request * 2828 evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, 2829 evdns_callback_type callback, void *ptr) { 2830 struct evdns_request *handle; 2831 struct request *req; 2832 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2833 handle = mm_calloc(1, sizeof(*handle)); 2834 if (handle == NULL) 2835 return NULL; 2836 EVDNS_LOCK(base); 2837 if (flags & DNS_QUERY_NO_SEARCH) { 2838 req = 2839 request_new(base, handle, TYPE_A, name, flags, 2840 callback, ptr); 2841 if (req) 2842 request_submit(req); 2843 } else { 2844 search_request_new(base, handle, TYPE_A, name, flags, 2845 callback, ptr); 2846 } 2847 if (handle->current_req == NULL) { 2848 mm_free(handle); 2849 handle = NULL; 2850 } 2851 EVDNS_UNLOCK(base); 2852 return handle; 2853 } 2854 2855 int evdns_resolve_ipv4(const char *name, int flags, 2856 evdns_callback_type callback, void *ptr) 2857 { 2858 return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr) 2859 ? 0 : -1; 2860 } 2861 2862 2863 /* exported function */ 2864 struct evdns_request * 2865 evdns_base_resolve_ipv6(struct evdns_base *base, 2866 const char *name, int flags, 2867 evdns_callback_type callback, void *ptr) 2868 { 2869 struct evdns_request *handle; 2870 struct request *req; 2871 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); 2872 handle = mm_calloc(1, sizeof(*handle)); 2873 if (handle == NULL) 2874 return NULL; 2875 EVDNS_LOCK(base); 2876 if (flags & DNS_QUERY_NO_SEARCH) { 2877 req = request_new(base, handle, TYPE_AAAA, name, flags, 2878 callback, ptr); 2879 if (req) 2880 request_submit(req); 2881 } else { 2882 search_request_new(base, handle, TYPE_AAAA, name, flags, 2883 callback, ptr); 2884 } 2885 if (handle->current_req == NULL) { 2886 mm_free(handle); 2887 handle = NULL; 2888 } 2889 EVDNS_UNLOCK(base); 2890 return handle; 2891 } 2892 2893 int evdns_resolve_ipv6(const char *name, int flags, 2894 evdns_callback_type callback, void *ptr) { 2895 return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr) 2896 ? 0 : -1; 2897 } 2898 2899 struct evdns_request * 2900 evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2901 char buf[32]; 2902 struct evdns_request *handle; 2903 struct request *req; 2904 u32 a; 2905 EVUTIL_ASSERT(in); 2906 a = ntohl(in->s_addr); 2907 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", 2908 (int)(u8)((a )&0xff), 2909 (int)(u8)((a>>8 )&0xff), 2910 (int)(u8)((a>>16)&0xff), 2911 (int)(u8)((a>>24)&0xff)); 2912 handle = mm_calloc(1, sizeof(*handle)); 2913 if (handle == NULL) 2914 return NULL; 2915 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2916 EVDNS_LOCK(base); 2917 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2918 if (req) 2919 request_submit(req); 2920 if (handle->current_req == NULL) { 2921 mm_free(handle); 2922 handle = NULL; 2923 } 2924 EVDNS_UNLOCK(base); 2925 return (handle); 2926 } 2927 2928 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2929 return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr) 2930 ? 0 : -1; 2931 } 2932 2933 struct evdns_request * 2934 evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2935 /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ 2936 char buf[73]; 2937 char *cp; 2938 struct evdns_request *handle; 2939 struct request *req; 2940 int i; 2941 EVUTIL_ASSERT(in); 2942 cp = buf; 2943 for (i=15; i >= 0; --i) { 2944 u8 byte = in->s6_addr[i]; 2945 *cp++ = "0123456789abcdef"[byte & 0x0f]; 2946 *cp++ = '.'; 2947 *cp++ = "0123456789abcdef"[byte >> 4]; 2948 *cp++ = '.'; 2949 } 2950 EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf)); 2951 memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); 2952 handle = mm_calloc(1, sizeof(*handle)); 2953 if (handle == NULL) 2954 return NULL; 2955 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); 2956 EVDNS_LOCK(base); 2957 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); 2958 if (req) 2959 request_submit(req); 2960 if (handle->current_req == NULL) { 2961 mm_free(handle); 2962 handle = NULL; 2963 } 2964 EVDNS_UNLOCK(base); 2965 return (handle); 2966 } 2967 2968 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { 2969 return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr) 2970 ? 0 : -1; 2971 } 2972 2973 /* ================================================================= */ 2974 /* Search support */ 2975 /* */ 2976 /* the libc resolver has support for searching a number of domains */ 2977 /* to find a name. If nothing else then it takes the single domain */ 2978 /* from the gethostname() call. */ 2979 /* */ 2980 /* It can also be configured via the domain and search options in a */ 2981 /* resolv.conf. */ 2982 /* */ 2983 /* The ndots option controls how many dots it takes for the resolver */ 2984 /* to decide that a name is non-local and so try a raw lookup first. */ 2985 2986 struct search_domain { 2987 int len; 2988 struct search_domain *next; 2989 /* the text string is appended to this structure */ 2990 }; 2991 2992 struct search_state { 2993 int refcount; 2994 int ndots; 2995 int num_domains; 2996 struct search_domain *head; 2997 }; 2998 2999 static void 3000 search_state_decref(struct search_state *const state) { 3001 if (!state) return; 3002 state->refcount--; 3003 if (!state->refcount) { 3004 struct search_domain *next, *dom; 3005 for (dom = state->head; dom; dom = next) { 3006 next = dom->next; 3007 mm_free(dom); 3008 } 3009 mm_free(state); 3010 } 3011 } 3012 3013 static struct search_state * 3014 search_state_new(void) { 3015 struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); 3016 if (!state) return NULL; 3017 memset(state, 0, sizeof(struct search_state)); 3018 state->refcount = 1; 3019 state->ndots = 1; 3020 3021 return state; 3022 } 3023 3024 static void 3025 search_postfix_clear(struct evdns_base *base) { 3026 search_state_decref(base->global_search_state); 3027 3028 base->global_search_state = search_state_new(); 3029 } 3030 3031 /* exported function */ 3032 void 3033 evdns_base_search_clear(struct evdns_base *base) 3034 { 3035 EVDNS_LOCK(base); 3036 search_postfix_clear(base); 3037 EVDNS_UNLOCK(base); 3038 } 3039 3040 void 3041 evdns_search_clear(void) { 3042 evdns_base_search_clear(current_base); 3043 } 3044 3045 static void 3046 search_postfix_add(struct evdns_base *base, const char *domain) { 3047 size_t domain_len; 3048 struct search_domain *sdomain; 3049 while (domain[0] == '.') domain++; 3050 domain_len = strlen(domain); 3051 3052 ASSERT_LOCKED(base); 3053 if (!base->global_search_state) base->global_search_state = search_state_new(); 3054 if (!base->global_search_state) return; 3055 base->global_search_state->num_domains++; 3056 3057 sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); 3058 if (!sdomain) return; 3059 memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); 3060 sdomain->next = base->global_search_state->head; 3061 sdomain->len = (int) domain_len; 3062 3063 base->global_search_state->head = sdomain; 3064 } 3065 3066 /* reverse the order of members in the postfix list. This is needed because, */ 3067 /* when parsing resolv.conf we push elements in the wrong order */ 3068 static void 3069 search_reverse(struct evdns_base *base) { 3070 struct search_domain *cur, *prev = NULL, *next; 3071 ASSERT_LOCKED(base); 3072 cur = base->global_search_state->head; 3073 while (cur) { 3074 next = cur->next; 3075 cur->next = prev; 3076 prev = cur; 3077 cur = next; 3078 } 3079 3080 base->global_search_state->head = prev; 3081 } 3082 3083 /* exported function */ 3084 void 3085 evdns_base_search_add(struct evdns_base *base, const char *domain) { 3086 EVDNS_LOCK(base); 3087 search_postfix_add(base, domain); 3088 EVDNS_UNLOCK(base); 3089 } 3090 void 3091 evdns_search_add(const char *domain) { 3092 evdns_base_search_add(current_base, domain); 3093 } 3094 3095 /* exported function */ 3096 void 3097 evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) { 3098 EVDNS_LOCK(base); 3099 if (!base->global_search_state) base->global_search_state = search_state_new(); 3100 if (base->global_search_state) 3101 base->global_search_state->ndots = ndots; 3102 EVDNS_UNLOCK(base); 3103 } 3104 void 3105 evdns_search_ndots_set(const int ndots) { 3106 evdns_base_search_ndots_set(current_base, ndots); 3107 } 3108 3109 static void 3110 search_set_from_hostname(struct evdns_base *base) { 3111 char hostname[HOST_NAME_MAX + 1], *domainname; 3112 3113 ASSERT_LOCKED(base); 3114 search_postfix_clear(base); 3115 if (gethostname(hostname, sizeof(hostname))) return; 3116 domainname = strchr(hostname, '.'); 3117 if (!domainname) return; 3118 search_postfix_add(base, domainname); 3119 } 3120 3121 /* warning: returns malloced string */ 3122 static char * 3123 search_make_new(const struct search_state *const state, int n, const char *const base_name) { 3124 const size_t base_len = strlen(base_name); 3125 const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; 3126 struct search_domain *dom; 3127 3128 for (dom = state->head; dom; dom = dom->next) { 3129 if (!n--) { 3130 /* this is the postfix we want */ 3131 /* the actual postfix string is kept at the end of the structure */ 3132 const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); 3133 const int postfix_len = dom->len; 3134 char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); 3135 if (!newname) return NULL; 3136 memcpy(newname, base_name, base_len); 3137 if (need_to_append_dot) newname[base_len] = '.'; 3138 memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); 3139 newname[base_len + need_to_append_dot + postfix_len] = 0; 3140 return newname; 3141 } 3142 } 3143 3144 /* we ran off the end of the list and still didn't find the requested string */ 3145 EVUTIL_ASSERT(0); 3146 return NULL; /* unreachable; stops warnings in some compilers. */ 3147 } 3148 3149 static struct request * 3150 search_request_new(struct evdns_base *base, struct evdns_request *handle, 3151 int type, const char *const name, int flags, 3152 evdns_callback_type user_callback, void *user_arg) { 3153 ASSERT_LOCKED(base); 3154 EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA); 3155 EVUTIL_ASSERT(handle->current_req == NULL); 3156 if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && 3157 base->global_search_state && 3158 base->global_search_state->num_domains) { 3159 /* we have some domains to search */ 3160 struct request *req; 3161 if (string_num_dots(name) >= base->global_search_state->ndots) { 3162 req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3163 if (!req) return NULL; 3164 handle->search_index = -1; 3165 } else { 3166 char *const new_name = search_make_new(base->global_search_state, 0, name); 3167 if (!new_name) return NULL; 3168 req = request_new(base, handle, type, new_name, flags, user_callback, user_arg); 3169 mm_free(new_name); 3170 if (!req) return NULL; 3171 handle->search_index = 0; 3172 } 3173 EVUTIL_ASSERT(handle->search_origname == NULL); 3174 handle->search_origname = mm_strdup(name); 3175 if (handle->search_origname == NULL) { 3176 /* XXX Should we dealloc req? If yes, how? */ 3177 if (req) 3178 mm_free(req); 3179 return NULL; 3180 } 3181 handle->search_state = base->global_search_state; 3182 handle->search_flags = flags; 3183 base->global_search_state->refcount++; 3184 request_submit(req); 3185 return req; 3186 } else { 3187 struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg); 3188 if (!req) return NULL; 3189 request_submit(req); 3190 return req; 3191 } 3192 } 3193 3194 /* this is called when a request has failed to find a name. We need to check */ 3195 /* if it is part of a search and, if so, try the next name in the list */ 3196 /* returns: */ 3197 /* 0 another request has been submitted */ 3198 /* 1 no more requests needed */ 3199 static int 3200 search_try_next(struct evdns_request *const handle) { 3201 struct request *req = handle->current_req; 3202 struct evdns_base *base = req->base; 3203 struct request *newreq; 3204 ASSERT_LOCKED(base); 3205 if (handle->search_state) { 3206 /* it is part of a search */ 3207 char *new_name; 3208 handle->search_index++; 3209 if (handle->search_index >= handle->search_state->num_domains) { 3210 /* no more postfixes to try, however we may need to try */ 3211 /* this name without a postfix */ 3212 if (string_num_dots(handle->search_origname) < handle->search_state->ndots) { 3213 /* yep, we need to try it raw */ 3214 newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer); 3215 log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname); 3216 if (newreq) { 3217 search_request_finished(handle); 3218 goto submit_next; 3219 } 3220 } 3221 return 1; 3222 } 3223 3224 new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname); 3225 if (!new_name) return 1; 3226 log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index); 3227 newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer); 3228 mm_free(new_name); 3229 if (!newreq) return 1; 3230 goto submit_next; 3231 } 3232 return 1; 3233 3234 submit_next: 3235 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0); 3236 handle->current_req = newreq; 3237 newreq->handle = handle; 3238 request_submit(newreq); 3239 return 0; 3240 } 3241 3242 static void 3243 search_request_finished(struct evdns_request *const handle) { 3244 ASSERT_LOCKED(handle->current_req->base); 3245 if (handle->search_state) { 3246 search_state_decref(handle->search_state); 3247 handle->search_state = NULL; 3248 } 3249 if (handle->search_origname) { 3250 mm_free(handle->search_origname); 3251 handle->search_origname = NULL; 3252 } 3253 } 3254 3255 /* ================================================================= */ 3256 /* Parsing resolv.conf files */ 3257 3258 static void 3259 evdns_resolv_set_defaults(struct evdns_base *base, int flags) { 3260 /* if the file isn't found then we assume a local resolver */ 3261 ASSERT_LOCKED(base); 3262 if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base); 3263 if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1"); 3264 } 3265 3266 #ifndef _EVENT_HAVE_STRTOK_R 3267 static char * 3268 strtok_r(char *s, const char *delim, char **state) { 3269 char *cp, *start; 3270 start = cp = s ? s : *state; 3271 if (!cp) 3272 return NULL; 3273 while (*cp && !strchr(delim, *cp)) 3274 ++cp; 3275 if (!*cp) { 3276 if (cp == start) 3277 return NULL; 3278 *state = NULL; 3279 return start; 3280 } else { 3281 *cp++ = '\0'; 3282 *state = cp; 3283 return start; 3284 } 3285 } 3286 #endif 3287 3288 /* helper version of atoi which returns -1 on error */ 3289 static int 3290 strtoint(const char *const str) 3291 { 3292 char *endptr; 3293 const int r = strtol(str, &endptr, 10); 3294 if (*endptr) return -1; 3295 return r; 3296 } 3297 3298 /* Parse a number of seconds into a timeval; return -1 on error. */ 3299 static int 3300 strtotimeval(const char *const str, struct timeval *out) 3301 { 3302 double d; 3303 char *endptr; 3304 d = strtod(str, &endptr); 3305 if (*endptr) return -1; 3306 if (d < 0) return -1; 3307 out->tv_sec = (int) d; 3308 out->tv_usec = (int) ((d - (int) d)*1000000); 3309 if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */ 3310 return -1; 3311 return 0; 3312 } 3313 3314 /* helper version of atoi that returns -1 on error and clips to bounds. */ 3315 static int 3316 strtoint_clipped(const char *const str, int min, int max) 3317 { 3318 int r = strtoint(str); 3319 if (r == -1) 3320 return r; 3321 else if (r<min) 3322 return min; 3323 else if (r>max) 3324 return max; 3325 else 3326 return r; 3327 } 3328 3329 static int 3330 evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight) 3331 { 3332 int old_n_heads = base->n_req_heads, n_heads; 3333 struct request **old_heads = base->req_heads, **new_heads, *req; 3334 int i; 3335 3336 ASSERT_LOCKED(base); 3337 if (maxinflight < 1) 3338 maxinflight = 1; 3339 n_heads = (maxinflight+4) / 5; 3340 EVUTIL_ASSERT(n_heads > 0); 3341 new_heads = mm_calloc(n_heads, sizeof(struct request*)); 3342 if (!new_heads) 3343 return (-1); 3344 if (old_heads) { 3345 for (i = 0; i < old_n_heads; ++i) { 3346 while (old_heads[i]) { 3347 req = old_heads[i]; 3348 evdns_request_remove(req, &old_heads[i]); 3349 evdns_request_insert(req, &new_heads[req->trans_id % n_heads]); 3350 } 3351 } 3352 mm_free(old_heads); 3353 } 3354 base->req_heads = new_heads; 3355 base->n_req_heads = n_heads; 3356 base->global_max_requests_inflight = maxinflight; 3357 return (0); 3358 } 3359 3360 /* exported function */ 3361 int 3362 evdns_base_set_option(struct evdns_base *base, 3363 const char *option, const char *val) 3364 { 3365 int res; 3366 EVDNS_LOCK(base); 3367 res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL); 3368 EVDNS_UNLOCK(base); 3369 return res; 3370 } 3371 3372 static inline int 3373 str_matches_option(const char *s1, const char *optionname) 3374 { 3375 /* Option names are given as "option:" We accept either 'option' in 3376 * s1, or 'option:randomjunk'. The latter form is to implement the 3377 * resolv.conf parser. */ 3378 size_t optlen = strlen(optionname); 3379 size_t slen = strlen(s1); 3380 if (slen == optlen || slen == optlen - 1) 3381 return !strncmp(s1, optionname, slen); 3382 else if (slen > optlen) 3383 return !strncmp(s1, optionname, optlen); 3384 else 3385 return 0; 3386 } 3387 3388 static int 3389 evdns_base_set_option_impl(struct evdns_base *base, 3390 const char *option, const char *val, int flags) 3391 { 3392 ASSERT_LOCKED(base); 3393 if (str_matches_option(option, "ndots:")) { 3394 const int ndots = strtoint(val); 3395 if (ndots == -1) return -1; 3396 if (!(flags & DNS_OPTION_SEARCH)) return 0; 3397 log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); 3398 if (!base->global_search_state) base->global_search_state = search_state_new(); 3399 if (!base->global_search_state) return -1; 3400 base->global_search_state->ndots = ndots; 3401 } else if (str_matches_option(option, "timeout:")) { 3402 struct timeval tv; 3403 if (strtotimeval(val, &tv) == -1) return -1; 3404 if (!(flags & DNS_OPTION_MISC)) return 0; 3405 log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val); 3406 memcpy(&base->global_timeout, &tv, sizeof(struct timeval)); 3407 } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) { 3408 struct timeval tv; 3409 if (strtotimeval(val, &tv) == -1) return -1; 3410 if (!(flags & DNS_OPTION_MISC)) return 0; 3411 log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s", 3412 val); 3413 memcpy(&base->global_getaddrinfo_allow_skew, &tv, 3414 sizeof(struct timeval)); 3415 } else if (str_matches_option(option, "max-timeouts:")) { 3416 const int maxtimeout = strtoint_clipped(val, 1, 255); 3417 if (maxtimeout == -1) return -1; 3418 if (!(flags & DNS_OPTION_MISC)) return 0; 3419 log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", 3420 maxtimeout); 3421 base->global_max_nameserver_timeout = maxtimeout; 3422 } else if (str_matches_option(option, "max-inflight:")) { 3423 const int maxinflight = strtoint_clipped(val, 1, 65000); 3424 if (maxinflight == -1) return -1; 3425 if (!(flags & DNS_OPTION_MISC)) return 0; 3426 log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", 3427 maxinflight); 3428 evdns_base_set_max_requests_inflight(base, maxinflight); 3429 } else if (str_matches_option(option, "attempts:")) { 3430 int retries = strtoint(val); 3431 if (retries == -1) return -1; 3432 if (retries > 255) retries = 255; 3433 if (!(flags & DNS_OPTION_MISC)) return 0; 3434 log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); 3435 base->global_max_retransmits = retries; 3436 } else if (str_matches_option(option, "randomize-case:")) { 3437 int randcase = strtoint(val); 3438 if (!(flags & DNS_OPTION_MISC)) return 0; 3439 base->global_randomize_case = randcase; 3440 } else if (str_matches_option(option, "bind-to:")) { 3441 /* XXX This only applies to successive nameservers, not 3442 * to already-configured ones. We might want to fix that. */ 3443 int len = sizeof(base->global_outgoing_address); 3444 if (!(flags & DNS_OPTION_NAMESERVERS)) return 0; 3445 if (evutil_parse_sockaddr_port(val, 3446 (struct sockaddr*)&base->global_outgoing_address, &len)) 3447 return -1; 3448 base->global_outgoing_addrlen = len; 3449 } else if (str_matches_option(option, "initial-probe-timeout:")) { 3450 struct timeval tv; 3451 if (strtotimeval(val, &tv) == -1) return -1; 3452 if (tv.tv_sec > 3600) 3453 tv.tv_sec = 3600; 3454 if (!(flags & DNS_OPTION_MISC)) return 0; 3455 log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s", 3456 val); 3457 memcpy(&base->global_nameserver_probe_initial_timeout, &tv, 3458 sizeof(tv)); 3459 } 3460 return 0; 3461 } 3462 3463 int 3464 evdns_set_option(const char *option, const char *val, int flags) 3465 { 3466 if (!current_base) 3467 current_base = evdns_base_new(NULL, 0); 3468 return evdns_base_set_option(current_base, option, val); 3469 } 3470 3471 static void 3472 resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) { 3473 char *strtok_state; 3474 static const char *const delims = " \t"; 3475 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 3476 3477 3478 char *const first_token = strtok_r(start, delims, &strtok_state); 3479 ASSERT_LOCKED(base); 3480 if (!first_token) return; 3481 3482 if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { 3483 const char *const nameserver = NEXT_TOKEN; 3484 3485 if (nameserver) 3486 evdns_base_nameserver_ip_add(base, nameserver); 3487 } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { 3488 const char *const domain = NEXT_TOKEN; 3489 if (domain) { 3490 search_postfix_clear(base); 3491 search_postfix_add(base, domain); 3492 } 3493 } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { 3494 const char *domain; 3495 search_postfix_clear(base); 3496 3497 while ((domain = NEXT_TOKEN)) { 3498 search_postfix_add(base, domain); 3499 } 3500 search_reverse(base); 3501 } else if (!strcmp(first_token, "options")) { 3502 const char *option; 3503 while ((option = NEXT_TOKEN)) { 3504 const char *val = strchr(option, ':'); 3505 evdns_base_set_option_impl(base, option, val ? val+1 : "", flags); 3506 } 3507 } 3508 #undef NEXT_TOKEN 3509 } 3510 3511 /* exported function */ 3512 /* returns: */ 3513 /* 0 no errors */ 3514 /* 1 failed to open file */ 3515 /* 2 failed to stat file */ 3516 /* 3 file too large */ 3517 /* 4 out of memory */ 3518 /* 5 short read from file */ 3519 int 3520 evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) { 3521 int res; 3522 EVDNS_LOCK(base); 3523 res = evdns_base_resolv_conf_parse_impl(base, flags, filename); 3524 EVDNS_UNLOCK(base); 3525 return res; 3526 } 3527 3528 static char * 3529 evdns_get_default_hosts_filename(void) 3530 { 3531 #ifdef WIN32 3532 /* Windows is a little coy about where it puts its configuration 3533 * files. Sure, they're _usually_ in C:\windows\system32, but 3534 * there's no reason in principle they couldn't be in 3535 * W:\hoboken chicken emergency\ 3536 */ 3537 char path[MAX_PATH+1]; 3538 static const char hostfile[] = "\\drivers\\etc\\hosts"; 3539 char *path_out; 3540 size_t len_out; 3541 3542 if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0)) 3543 return NULL; 3544 len_out = strlen(path)+strlen(hostfile); 3545 path_out = mm_malloc(len_out+1); 3546 evutil_snprintf(path_out, len_out, "%s%s", path, hostfile); 3547 return path_out; 3548 #else 3549 return mm_strdup("/etc/hosts"); 3550 #endif 3551 } 3552 3553 static int 3554 evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) { 3555 size_t n; 3556 char *resolv; 3557 char *start; 3558 int err = 0; 3559 3560 log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); 3561 3562 if (flags & DNS_OPTION_HOSTSFILE) { 3563 char *fname = evdns_get_default_hosts_filename(); 3564 evdns_base_load_hosts(base, fname); 3565 if (fname) 3566 mm_free(fname); 3567 } 3568 3569 if ((err = evutil_read_file(filename, &resolv, &n, 0)) < 0) { 3570 if (err == -1) { 3571 /* No file. */ 3572 evdns_resolv_set_defaults(base, flags); 3573 return 1; 3574 } else { 3575 return 2; 3576 } 3577 } 3578 3579 start = resolv; 3580 for (;;) { 3581 char *const newline = strchr(start, '\n'); 3582 if (!newline) { 3583 resolv_conf_parse_line(base, start, flags); 3584 break; 3585 } else { 3586 *newline = 0; 3587 resolv_conf_parse_line(base, start, flags); 3588 start = newline + 1; 3589 } 3590 } 3591 3592 if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) { 3593 /* no nameservers were configured. */ 3594 evdns_base_nameserver_ip_add(base, "127.0.0.1"); 3595 err = 6; 3596 } 3597 if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) { 3598 search_set_from_hostname(base); 3599 } 3600 3601 mm_free(resolv); 3602 return err; 3603 } 3604 3605 int 3606 evdns_resolv_conf_parse(int flags, const char *const filename) { 3607 if (!current_base) 3608 current_base = evdns_base_new(NULL, 0); 3609 return evdns_base_resolv_conf_parse(current_base, flags, filename); 3610 } 3611 3612 3613 #ifdef WIN32 3614 /* Add multiple nameservers from a space-or-comma-separated list. */ 3615 static int 3616 evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) { 3617 const char *addr; 3618 char *buf; 3619 int r; 3620 ASSERT_LOCKED(base); 3621 while (*ips) { 3622 while (isspace(*ips) || *ips == ',' || *ips == '\t') 3623 ++ips; 3624 addr = ips; 3625 while (isdigit(*ips) || *ips == '.' || *ips == ':' || 3626 *ips=='[' || *ips==']') 3627 ++ips; 3628 buf = mm_malloc(ips-addr+1); 3629 if (!buf) return 4; 3630 memcpy(buf, addr, ips-addr); 3631 buf[ips-addr] = '\0'; 3632 r = evdns_base_nameserver_ip_add(base, buf); 3633 mm_free(buf); 3634 if (r) return r; 3635 } 3636 return 0; 3637 } 3638 3639 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); 3640 3641 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ 3642 /* figure out what our nameservers are. */ 3643 static int 3644 load_nameservers_with_getnetworkparams(struct evdns_base *base) 3645 { 3646 /* Based on MSDN examples and inspection of c-ares code. */ 3647 FIXED_INFO *fixed; 3648 HMODULE handle = 0; 3649 ULONG size = sizeof(FIXED_INFO); 3650 void *buf = NULL; 3651 int status = 0, r, added_any; 3652 IP_ADDR_STRING *ns; 3653 GetNetworkParams_fn_t fn; 3654 3655 ASSERT_LOCKED(base); 3656 if (!(handle = evutil_load_windows_system_library( 3657 TEXT("iphlpapi.dll")))) { 3658 log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); 3659 status = -1; 3660 goto done; 3661 } 3662 if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { 3663 log(EVDNS_LOG_WARN, "Could not get address of function."); 3664 status = -1; 3665 goto done; 3666 } 3667 3668 buf = mm_malloc(size); 3669 if (!buf) { status = 4; goto done; } 3670 fixed = buf; 3671 r = fn(fixed, &size); 3672 if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { 3673 status = -1; 3674 goto done; 3675 } 3676 if (r != ERROR_SUCCESS) { 3677 mm_free(buf); 3678 buf = mm_malloc(size); 3679 if (!buf) { status = 4; goto done; } 3680 fixed = buf; 3681 r = fn(fixed, &size); 3682 if (r != ERROR_SUCCESS) { 3683 log(EVDNS_LOG_DEBUG, "fn() failed."); 3684 status = -1; 3685 goto done; 3686 } 3687 } 3688 3689 EVUTIL_ASSERT(fixed); 3690 added_any = 0; 3691 ns = &(fixed->DnsServerList); 3692 while (ns) { 3693 r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String); 3694 if (r) { 3695 log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", 3696 (ns->IpAddress.String),(int)GetLastError()); 3697 status = r; 3698 } else { 3699 ++added_any; 3700 log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); 3701 } 3702 3703 ns = ns->Next; 3704 } 3705 3706 if (!added_any) { 3707 log(EVDNS_LOG_DEBUG, "No nameservers added."); 3708 if (status == 0) 3709 status = -1; 3710 } else { 3711 status = 0; 3712 } 3713 3714 done: 3715 if (buf) 3716 mm_free(buf); 3717 if (handle) 3718 FreeLibrary(handle); 3719 return status; 3720 } 3721 3722 static int 3723 config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey) 3724 { 3725 char *buf; 3726 DWORD bufsz = 0, type = 0; 3727 int status = 0; 3728 3729 ASSERT_LOCKED(base); 3730 if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) 3731 != ERROR_MORE_DATA) 3732 return -1; 3733 if (!(buf = mm_malloc(bufsz))) 3734 return -1; 3735 3736 if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) 3737 == ERROR_SUCCESS && bufsz > 1) { 3738 status = evdns_nameserver_ip_add_line(base,buf); 3739 } 3740 3741 mm_free(buf); 3742 return status; 3743 } 3744 3745 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\") 3746 #define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP") 3747 #define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters") 3748 3749 static int 3750 load_nameservers_from_registry(struct evdns_base *base) 3751 { 3752 int found = 0; 3753 int r; 3754 #define TRY(k, name) \ 3755 if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \ 3756 log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ 3757 found = 1; \ 3758 } else if (!found) { \ 3759 log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ 3760 #k,#name); \ 3761 } 3762 3763 ASSERT_LOCKED(base); 3764 3765 if (((int)GetVersion()) > 0) { /* NT */ 3766 HKEY nt_key = 0, interfaces_key = 0; 3767 3768 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, 3769 KEY_READ, &nt_key) != ERROR_SUCCESS) { 3770 log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); 3771 return -1; 3772 } 3773 r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0, 3774 KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, 3775 &interfaces_key); 3776 if (r != ERROR_SUCCESS) { 3777 log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); 3778 return -1; 3779 } 3780 TRY(nt_key, "NameServer"); 3781 TRY(nt_key, "DhcpNameServer"); 3782 TRY(interfaces_key, "NameServer"); 3783 TRY(interfaces_key, "DhcpNameServer"); 3784 RegCloseKey(interfaces_key); 3785 RegCloseKey(nt_key); 3786 } else { 3787 HKEY win_key = 0; 3788 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, 3789 KEY_READ, &win_key) != ERROR_SUCCESS) { 3790 log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); 3791 return -1; 3792 } 3793 TRY(win_key, "NameServer"); 3794 RegCloseKey(win_key); 3795 } 3796 3797 if (found == 0) { 3798 log(EVDNS_LOG_WARN,"Didn't find any nameservers."); 3799 } 3800 3801 return found ? 0 : -1; 3802 #undef TRY 3803 } 3804 3805 int 3806 evdns_base_config_windows_nameservers(struct evdns_base *base) 3807 { 3808 int r; 3809 char *fname; 3810 if (base == NULL) 3811 base = current_base; 3812 if (base == NULL) 3813 return -1; 3814 EVDNS_LOCK(base); 3815 if (load_nameservers_with_getnetworkparams(base) == 0) { 3816 EVDNS_UNLOCK(base); 3817 return 0; 3818 } 3819 r = load_nameservers_from_registry(base); 3820 3821 fname = evdns_get_default_hosts_filename(); 3822 evdns_base_load_hosts(base, fname); 3823 if (fname) 3824 mm_free(fname); 3825 3826 EVDNS_UNLOCK(base); 3827 return r; 3828 } 3829 3830 int 3831 evdns_config_windows_nameservers(void) 3832 { 3833 if (!current_base) { 3834 current_base = evdns_base_new(NULL, 1); 3835 return current_base == NULL ? -1 : 0; 3836 } else { 3837 return evdns_base_config_windows_nameservers(current_base); 3838 } 3839 } 3840 #endif 3841 3842 struct evdns_base * 3843 evdns_base_new(struct event_base *event_base, int initialize_nameservers) 3844 { 3845 struct evdns_base *base; 3846 3847 if (evutil_secure_rng_init() < 0) { 3848 log(EVDNS_LOG_WARN, "Unable to seed random number generator; " 3849 "DNS can't run."); 3850 return NULL; 3851 } 3852 3853 /* Give the evutil library a hook into its evdns-enabled 3854 * functionality. We can't just call evdns_getaddrinfo directly or 3855 * else libevent-core will depend on libevent-extras. */ 3856 evutil_set_evdns_getaddrinfo_fn(evdns_getaddrinfo); 3857 3858 base = mm_malloc(sizeof(struct evdns_base)); 3859 if (base == NULL) 3860 return (NULL); 3861 memset(base, 0, sizeof(struct evdns_base)); 3862 base->req_waiting_head = NULL; 3863 3864 EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 3865 EVDNS_LOCK(base); 3866 3867 /* Set max requests inflight and allocate req_heads. */ 3868 base->req_heads = NULL; 3869 3870 evdns_base_set_max_requests_inflight(base, 64); 3871 3872 base->server_head = NULL; 3873 base->event_base = event_base; 3874 base->global_good_nameservers = base->global_requests_inflight = 3875 base->global_requests_waiting = 0; 3876 3877 base->global_timeout.tv_sec = 5; 3878 base->global_timeout.tv_usec = 0; 3879 base->global_max_reissues = 1; 3880 base->global_max_retransmits = 3; 3881 base->global_max_nameserver_timeout = 3; 3882 base->global_search_state = NULL; 3883 base->global_randomize_case = 1; 3884 base->global_getaddrinfo_allow_skew.tv_sec = 3; 3885 base->global_getaddrinfo_allow_skew.tv_usec = 0; 3886 base->global_nameserver_probe_initial_timeout.tv_sec = 10; 3887 base->global_nameserver_probe_initial_timeout.tv_usec = 0; 3888 3889 TAILQ_INIT(&base->hostsdb); 3890 3891 if (initialize_nameservers) { 3892 int r; 3893 #ifdef WIN32 3894 r = evdns_base_config_windows_nameservers(base); 3895 #else 3896 r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf"); 3897 #endif 3898 if (r == -1) { 3899 evdns_base_free_and_unlock(base, 0); 3900 return NULL; 3901 } 3902 } 3903 EVDNS_UNLOCK(base); 3904 return base; 3905 } 3906 3907 int 3908 evdns_init(void) 3909 { 3910 struct evdns_base *base = evdns_base_new(NULL, 1); 3911 if (base) { 3912 current_base = base; 3913 return 0; 3914 } else { 3915 return -1; 3916 } 3917 } 3918 3919 const char * 3920 evdns_err_to_string(int err) 3921 { 3922 switch (err) { 3923 case DNS_ERR_NONE: return "no error"; 3924 case DNS_ERR_FORMAT: return "misformatted query"; 3925 case DNS_ERR_SERVERFAILED: return "server failed"; 3926 case DNS_ERR_NOTEXIST: return "name does not exist"; 3927 case DNS_ERR_NOTIMPL: return "query not implemented"; 3928 case DNS_ERR_REFUSED: return "refused"; 3929 3930 case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; 3931 case DNS_ERR_UNKNOWN: return "unknown"; 3932 case DNS_ERR_TIMEOUT: return "request timed out"; 3933 case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; 3934 case DNS_ERR_CANCEL: return "dns request canceled"; 3935 case DNS_ERR_NODATA: return "no records in the reply"; 3936 default: return "[Unknown error code]"; 3937 } 3938 } 3939 3940 static void 3941 evdns_nameserver_free(struct nameserver *server) 3942 { 3943 if (server->socket >= 0) 3944 evutil_closesocket(server->socket); 3945 (void) event_del(&server->event); 3946 event_debug_unassign(&server->event); 3947 if (server->state == 0) 3948 (void) event_del(&server->timeout_event); 3949 if (server->probe_request) { 3950 evdns_cancel_request(server->base, server->probe_request); 3951 server->probe_request = NULL; 3952 } 3953 event_debug_unassign(&server->timeout_event); 3954 mm_free(server); 3955 } 3956 3957 static void 3958 evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests) 3959 { 3960 struct nameserver *server, *server_next; 3961 struct search_domain *dom, *dom_next; 3962 int i; 3963 3964 /* Requires that we hold the lock. */ 3965 3966 /* TODO(nickm) we might need to refcount here. */ 3967 3968 for (server = base->server_head; server; server = server_next) { 3969 server_next = server->next; 3970 evdns_nameserver_free(server); 3971 if (server_next == base->server_head) 3972 break; 3973 } 3974 base->server_head = NULL; 3975 base->global_good_nameservers = 0; 3976 3977 for (i = 0; i < base->n_req_heads; ++i) { 3978 while (base->req_heads[i]) { 3979 if (fail_requests) 3980 reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL); 3981 request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1); 3982 } 3983 } 3984 while (base->req_waiting_head) { 3985 if (fail_requests) 3986 reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); 3987 request_finished(base->req_waiting_head, &base->req_waiting_head, 1); 3988 } 3989 base->global_requests_inflight = base->global_requests_waiting = 0; 3990 3991 3992 if (base->global_search_state) { 3993 for (dom = base->global_search_state->head; dom; dom = dom_next) { 3994 dom_next = dom->next; 3995 mm_free(dom); 3996 } 3997 mm_free(base->global_search_state); 3998 base->global_search_state = NULL; 3999 } 4000 4001 { 4002 struct hosts_entry *victim; 4003 while ((victim = TAILQ_FIRST(&base->hostsdb))) { 4004 TAILQ_REMOVE(&base->hostsdb, victim, next); 4005 mm_free(victim); 4006 } 4007 } 4008 4009 mm_free(base->req_heads); 4010 4011 EVDNS_UNLOCK(base); 4012 EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); 4013 4014 mm_free(base); 4015 } 4016 4017 void 4018 evdns_base_free(struct evdns_base *base, int fail_requests) 4019 { 4020 EVDNS_LOCK(base); 4021 evdns_base_free_and_unlock(base, fail_requests); 4022 } 4023 4024 void 4025 evdns_shutdown(int fail_requests) 4026 { 4027 if (current_base) { 4028 struct evdns_base *b = current_base; 4029 current_base = NULL; 4030 evdns_base_free(b, fail_requests); 4031 } 4032 evdns_log_fn = NULL; 4033 } 4034 4035 static int 4036 evdns_base_parse_hosts_line(struct evdns_base *base, char *line) 4037 { 4038 char *strtok_state; 4039 static const char *const delims = " \t"; 4040 char *const addr = strtok_r(line, delims, &strtok_state); 4041 char *hostname, *hash; 4042 struct sockaddr_storage ss; 4043 int socklen = sizeof(ss); 4044 ASSERT_LOCKED(base); 4045 4046 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) 4047 4048 if (!addr || *addr == '#') 4049 return 0; 4050 4051 memset(&ss, 0, sizeof(ss)); 4052 if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0) 4053 return -1; 4054 if (socklen > (int)sizeof(struct sockaddr_in6)) 4055 return -1; 4056 4057 if (sockaddr_getport((struct sockaddr*)&ss)) 4058 return -1; 4059 4060 while ((hostname = NEXT_TOKEN)) { 4061 struct hosts_entry *he; 4062 size_t namelen; 4063 if ((hash = strchr(hostname, '#'))) { 4064 if (hash == hostname) 4065 return 0; 4066 *hash = '\0'; 4067 } 4068 4069 namelen = strlen(hostname); 4070 4071 he = mm_calloc(1, sizeof(struct hosts_entry)+namelen); 4072 if (!he) 4073 return -1; 4074 EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr)); 4075 memcpy(&he->addr, &ss, socklen); 4076 memcpy(he->hostname, hostname, namelen+1); 4077 he->addrlen = socklen; 4078 4079 TAILQ_INSERT_TAIL(&base->hostsdb, he, next); 4080 4081 if (hash) 4082 return 0; 4083 } 4084 4085 return 0; 4086 #undef NEXT_TOKEN 4087 } 4088 4089 static int 4090 evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname) 4091 { 4092 char *str=NULL, *cp, *eol; 4093 size_t len; 4094 int err=0; 4095 4096 ASSERT_LOCKED(base); 4097 4098 if (hosts_fname == NULL || 4099 (err = evutil_read_file(hosts_fname, &str, &len, 0)) < 0) { 4100 char tmp[64]; 4101 strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp)); 4102 evdns_base_parse_hosts_line(base, tmp); 4103 strlcpy(tmp, "::1 localhost", sizeof(tmp)); 4104 evdns_base_parse_hosts_line(base, tmp); 4105 return err ? -1 : 0; 4106 } 4107 4108 /* This will break early if there is a NUL in the hosts file. 4109 * Probably not a problem.*/ 4110 cp = str; 4111 for (;;) { 4112 eol = strchr(cp, '\n'); 4113 4114 if (eol) { 4115 *eol = '\0'; 4116 evdns_base_parse_hosts_line(base, cp); 4117 cp = eol+1; 4118 } else { 4119 evdns_base_parse_hosts_line(base, cp); 4120 break; 4121 } 4122 } 4123 4124 mm_free(str); 4125 return 0; 4126 } 4127 4128 int 4129 evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname) 4130 { 4131 int res; 4132 if (!base) 4133 base = current_base; 4134 EVDNS_LOCK(base); 4135 res = evdns_base_load_hosts_impl(base, hosts_fname); 4136 EVDNS_UNLOCK(base); 4137 return res; 4138 } 4139 4140 /* A single request for a getaddrinfo, either v4 or v6. */ 4141 struct getaddrinfo_subrequest { 4142 struct evdns_request *r; 4143 ev_uint32_t type; 4144 }; 4145 4146 /* State data used to implement an in-progress getaddrinfo. */ 4147 struct evdns_getaddrinfo_request { 4148 struct evdns_base *evdns_base; 4149 /* Copy of the modified 'hints' data that we'll use to build 4150 * answers. */ 4151 struct evutil_addrinfo hints; 4152 /* The callback to invoke when we're done */ 4153 evdns_getaddrinfo_cb user_cb; 4154 /* User-supplied data to give to the callback. */ 4155 void *user_data; 4156 /* The port to use when building sockaddrs. */ 4157 ev_uint16_t port; 4158 /* The sub_request for an A record (if any) */ 4159 struct getaddrinfo_subrequest ipv4_request; 4160 /* The sub_request for an AAAA record (if any) */ 4161 struct getaddrinfo_subrequest ipv6_request; 4162 4163 /* The cname result that we were told (if any) */ 4164 char *cname_result; 4165 4166 /* If we have one request answered and one request still inflight, 4167 * then this field holds the answer from the first request... */ 4168 struct evutil_addrinfo *pending_result; 4169 /* And this event is a timeout that will tell us to cancel the second 4170 * request if it's taking a long time. */ 4171 struct event timeout; 4172 4173 /* And this field holds the error code from the first request... */ 4174 int pending_error; 4175 /* If this is set, the user canceled this request. */ 4176 unsigned user_canceled : 1; 4177 /* If this is set, the user can no longer cancel this request; we're 4178 * just waiting for the free. */ 4179 unsigned request_done : 1; 4180 }; 4181 4182 /* Convert an evdns errors to the equivalent getaddrinfo error. */ 4183 static int 4184 evdns_err_to_getaddrinfo_err(int e1) 4185 { 4186 /* XXX Do this better! */ 4187 if (e1 == DNS_ERR_NONE) 4188 return 0; 4189 else if (e1 == DNS_ERR_NOTEXIST) 4190 return EVUTIL_EAI_NONAME; 4191 else 4192 return EVUTIL_EAI_FAIL; 4193 } 4194 4195 /* Return the more informative of two getaddrinfo errors. */ 4196 static int 4197 getaddrinfo_merge_err(int e1, int e2) 4198 { 4199 /* XXXX be cleverer here. */ 4200 if (e1 == 0) 4201 return e2; 4202 else 4203 return e1; 4204 } 4205 4206 static void 4207 free_getaddrinfo_request(struct evdns_getaddrinfo_request *data) 4208 { 4209 /* DO NOT CALL this if either of the requests is pending. Only once 4210 * both callbacks have been invoked is it safe to free the request */ 4211 if (data->pending_result) 4212 evutil_freeaddrinfo(data->pending_result); 4213 if (data->cname_result) 4214 mm_free(data->cname_result); 4215 event_del(&data->timeout); 4216 mm_free(data); 4217 return; 4218 } 4219 4220 static void 4221 add_cname_to_reply(struct evdns_getaddrinfo_request *data, 4222 struct evutil_addrinfo *ai) 4223 { 4224 if (data->cname_result && ai) { 4225 ai->ai_canonname = data->cname_result; 4226 data->cname_result = NULL; 4227 } 4228 } 4229 4230 /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo 4231 * request has finished, but the other one took too long to answer. Pass 4232 * along the answer we got, and cancel the other request. 4233 */ 4234 static void 4235 evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr) 4236 { 4237 int v4_timedout = 0, v6_timedout = 0; 4238 struct evdns_getaddrinfo_request *data = ptr; 4239 4240 /* Cancel any pending requests, and note which one */ 4241 if (data->ipv4_request.r) { 4242 /* XXXX This does nothing if the request's callback is already 4243 * running (pending_cb is set). */ 4244 evdns_cancel_request(NULL, data->ipv4_request.r); 4245 v4_timedout = 1; 4246 EVDNS_LOCK(data->evdns_base); 4247 ++data->evdns_base->getaddrinfo_ipv4_timeouts; 4248 EVDNS_UNLOCK(data->evdns_base); 4249 } 4250 if (data->ipv6_request.r) { 4251 /* XXXX This does nothing if the request's callback is already 4252 * running (pending_cb is set). */ 4253 evdns_cancel_request(NULL, data->ipv6_request.r); 4254 v6_timedout = 1; 4255 EVDNS_LOCK(data->evdns_base); 4256 ++data->evdns_base->getaddrinfo_ipv6_timeouts; 4257 EVDNS_UNLOCK(data->evdns_base); 4258 } 4259 4260 /* We only use this timeout callback when we have an answer for 4261 * one address. */ 4262 EVUTIL_ASSERT(!v4_timedout || !v6_timedout); 4263 4264 /* Report the outcome of the other request that didn't time out. */ 4265 if (data->pending_result) { 4266 add_cname_to_reply(data, data->pending_result); 4267 data->user_cb(0, data->pending_result, data->user_data); 4268 data->pending_result = NULL; 4269 } else { 4270 int e = data->pending_error; 4271 if (!e) 4272 e = EVUTIL_EAI_AGAIN; 4273 data->user_cb(e, NULL, data->user_data); 4274 } 4275 4276 data->user_cb = NULL; /* prevent double-call if evdns callbacks are 4277 * in-progress. XXXX It would be better if this 4278 * weren't necessary. */ 4279 4280 if (!v4_timedout && !v6_timedout) { 4281 /* should be impossible? XXXX */ 4282 free_getaddrinfo_request(data); 4283 } 4284 } 4285 4286 static int 4287 evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base, 4288 struct evdns_getaddrinfo_request *data) 4289 { 4290 return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew); 4291 } 4292 4293 static inline int 4294 evdns_result_is_answer(int result) 4295 { 4296 return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED && 4297 result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL); 4298 } 4299 4300 static void 4301 evdns_getaddrinfo_gotresolve(int result, char type, int count, 4302 int ttl, void *addresses, void *arg) 4303 { 4304 int i; 4305 struct getaddrinfo_subrequest *req = arg; 4306 struct getaddrinfo_subrequest *other_req; 4307 struct evdns_getaddrinfo_request *data; 4308 4309 struct evutil_addrinfo *res; 4310 4311 struct sockaddr_in sin; 4312 struct sockaddr_in6 sin6; 4313 struct sockaddr *sa; 4314 int socklen, addrlen; 4315 void *addrp; 4316 int err; 4317 int user_canceled; 4318 4319 EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA); 4320 if (req->type == DNS_IPv4_A) { 4321 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request); 4322 other_req = &data->ipv6_request; 4323 } else { 4324 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request); 4325 other_req = &data->ipv4_request; 4326 } 4327 4328 EVDNS_LOCK(data->evdns_base); 4329 if (evdns_result_is_answer(result)) { 4330 if (req->type == DNS_IPv4_A) 4331 ++data->evdns_base->getaddrinfo_ipv4_answered; 4332 else 4333 ++data->evdns_base->getaddrinfo_ipv6_answered; 4334 } 4335 user_canceled = data->user_canceled; 4336 if (other_req->r == NULL) 4337 data->request_done = 1; 4338 EVDNS_UNLOCK(data->evdns_base); 4339 4340 req->r = NULL; 4341 4342 if (result == DNS_ERR_CANCEL && ! user_canceled) { 4343 /* Internal cancel request from timeout or internal error. 4344 * we already answered the user. */ 4345 if (other_req->r == NULL) 4346 free_getaddrinfo_request(data); 4347 return; 4348 } 4349 4350 if (data->user_cb == NULL) { 4351 /* We already answered. XXXX This shouldn't be needed; see 4352 * comments in evdns_getaddrinfo_timeout_cb */ 4353 free_getaddrinfo_request(data); 4354 return; 4355 } 4356 4357 if (result == DNS_ERR_NONE) { 4358 if (count == 0) 4359 err = EVUTIL_EAI_NODATA; 4360 else 4361 err = 0; 4362 } else { 4363 err = evdns_err_to_getaddrinfo_err(result); 4364 } 4365 4366 if (err) { 4367 /* Looks like we got an error. */ 4368 if (other_req->r) { 4369 /* The other request is still working; maybe it will 4370 * succeed. */ 4371 /* XXXX handle failure from set_timeout */ 4372 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4373 data->pending_error = err; 4374 return; 4375 } 4376 4377 if (user_canceled) { 4378 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4379 } else if (data->pending_result) { 4380 /* If we have an answer waiting, and we weren't 4381 * canceled, ignore this error. */ 4382 add_cname_to_reply(data, data->pending_result); 4383 data->user_cb(0, data->pending_result, data->user_data); 4384 data->pending_result = NULL; 4385 } else { 4386 if (data->pending_error) 4387 err = getaddrinfo_merge_err(err, 4388 data->pending_error); 4389 data->user_cb(err, NULL, data->user_data); 4390 } 4391 free_getaddrinfo_request(data); 4392 return; 4393 } else if (user_canceled) { 4394 if (other_req->r) { 4395 /* The other request is still working; let it hit this 4396 * callback with EVUTIL_EAI_CANCEL callback and report 4397 * the failure. */ 4398 return; 4399 } 4400 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); 4401 free_getaddrinfo_request(data); 4402 return; 4403 } 4404 4405 /* Looks like we got some answers. We should turn them into addrinfos 4406 * and then either queue those or return them all. */ 4407 EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA); 4408 4409 if (type == DNS_IPv4_A) { 4410 memset(&sin, 0, sizeof(sin)); 4411 sin.sin_family = AF_INET; 4412 sin.sin_port = htons(data->port); 4413 4414 sa = (struct sockaddr *)&sin; 4415 socklen = sizeof(sin); 4416 addrlen = 4; 4417 addrp = &sin.sin_addr.s_addr; 4418 } else { 4419 memset(&sin6, 0, sizeof(sin6)); 4420 sin6.sin6_family = AF_INET6; 4421 sin6.sin6_port = htons(data->port); 4422 4423 sa = (struct sockaddr *)&sin6; 4424 socklen = sizeof(sin6); 4425 addrlen = 16; 4426 addrp = &sin6.sin6_addr.s6_addr; 4427 } 4428 4429 res = NULL; 4430 for (i=0; i < count; ++i) { 4431 struct evutil_addrinfo *ai; 4432 memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen); 4433 ai = evutil_new_addrinfo(sa, socklen, &data->hints); 4434 if (!ai) { 4435 if (other_req->r) { 4436 evdns_cancel_request(NULL, other_req->r); 4437 } 4438 data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data); 4439 if (res) 4440 evutil_freeaddrinfo(res); 4441 4442 if (other_req->r == NULL) 4443 free_getaddrinfo_request(data); 4444 return; 4445 } 4446 res = evutil_addrinfo_append(res, ai); 4447 } 4448 4449 if (other_req->r) { 4450 /* The other request is still in progress; wait for it */ 4451 /* XXXX handle failure from set_timeout */ 4452 evdns_getaddrinfo_set_timeout(data->evdns_base, data); 4453 data->pending_result = res; 4454 return; 4455 } else { 4456 /* The other request is done or never started; append its 4457 * results (if any) and return them. */ 4458 if (data->pending_result) { 4459 if (req->type == DNS_IPv4_A) 4460 res = evutil_addrinfo_append(res, 4461 data->pending_result); 4462 else 4463 res = evutil_addrinfo_append( 4464 data->pending_result, res); 4465 data->pending_result = NULL; 4466 } 4467 4468 /* Call the user callback. */ 4469 add_cname_to_reply(data, res); 4470 data->user_cb(0, res, data->user_data); 4471 4472 /* Free data. */ 4473 free_getaddrinfo_request(data); 4474 } 4475 } 4476 4477 static struct hosts_entry * 4478 find_hosts_entry(struct evdns_base *base, const char *hostname, 4479 struct hosts_entry *find_after) 4480 { 4481 struct hosts_entry *e; 4482 4483 if (find_after) 4484 e = TAILQ_NEXT(find_after, next); 4485 else 4486 e = TAILQ_FIRST(&base->hostsdb); 4487 4488 for (; e; e = TAILQ_NEXT(e, next)) { 4489 if (!evutil_ascii_strcasecmp(e->hostname, hostname)) 4490 return e; 4491 } 4492 return NULL; 4493 } 4494 4495 static int 4496 evdns_getaddrinfo_fromhosts(struct evdns_base *base, 4497 const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port, 4498 struct evutil_addrinfo **res) 4499 { 4500 int n_found = 0; 4501 struct hosts_entry *e; 4502 struct evutil_addrinfo *ai=NULL; 4503 int f = hints->ai_family; 4504 4505 EVDNS_LOCK(base); 4506 for (e = find_hosts_entry(base, nodename, NULL); e; 4507 e = find_hosts_entry(base, nodename, e)) { 4508 struct evutil_addrinfo *ai_new; 4509 ++n_found; 4510 if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) || 4511 (e->addr.sa.sa_family == AF_INET6 && f == PF_INET)) 4512 continue; 4513 ai_new = evutil_new_addrinfo(&e->addr.sa, e->addrlen, hints); 4514 if (!ai_new) { 4515 n_found = 0; 4516 goto out; 4517 } 4518 sockaddr_setport(ai_new->ai_addr, port); 4519 ai = evutil_addrinfo_append(ai, ai_new); 4520 } 4521 EVDNS_UNLOCK(base); 4522 out: 4523 if (n_found) { 4524 /* Note that we return an empty answer if we found entries for 4525 * this hostname but none were of the right address type. */ 4526 *res = ai; 4527 return 0; 4528 } else { 4529 if (ai) 4530 evutil_freeaddrinfo(ai); 4531 return -1; 4532 } 4533 } 4534 4535 struct evdns_getaddrinfo_request * 4536 evdns_getaddrinfo(struct evdns_base *dns_base, 4537 const char *nodename, const char *servname, 4538 const struct evutil_addrinfo *hints_in, 4539 evdns_getaddrinfo_cb cb, void *arg) 4540 { 4541 struct evdns_getaddrinfo_request *data; 4542 struct evutil_addrinfo hints; 4543 struct evutil_addrinfo *res = NULL; 4544 int err; 4545 int port = 0; 4546 int want_cname = 0; 4547 4548 if (!dns_base) { 4549 dns_base = current_base; 4550 if (!dns_base) { 4551 log(EVDNS_LOG_WARN, 4552 "Call to getaddrinfo_async with no " 4553 "evdns_base configured."); 4554 cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */ 4555 return NULL; 4556 } 4557 } 4558 4559 /* If we _must_ answer this immediately, do so. */ 4560 if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) { 4561 res = NULL; 4562 err = evutil_getaddrinfo(nodename, servname, hints_in, &res); 4563 cb(err, res, arg); 4564 return NULL; 4565 } 4566 4567 if (hints_in) { 4568 memcpy(&hints, hints_in, sizeof(hints)); 4569 } else { 4570 memset(&hints, 0, sizeof(hints)); 4571 hints.ai_family = PF_UNSPEC; 4572 } 4573 4574 evutil_adjust_hints_for_addrconfig(&hints); 4575 4576 /* Now try to see if we _can_ answer immediately. */ 4577 /* (It would be nice to do this by calling getaddrinfo directly, with 4578 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't 4579 * a reliable way to distinguish the "that wasn't a numeric host!" case 4580 * from any other EAI_NONAME cases.) */ 4581 err = evutil_getaddrinfo_common(nodename, servname, &hints, &res, &port); 4582 if (err != EVUTIL_EAI_NEED_RESOLVE) { 4583 cb(err, res, arg); 4584 return NULL; 4585 } 4586 4587 /* If there is an entry in the hosts file, we should give it now. */ 4588 if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) { 4589 cb(0, res, arg); 4590 return NULL; 4591 } 4592 4593 /* Okay, things are serious now. We're going to need to actually 4594 * launch a request. 4595 */ 4596 data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request)); 4597 if (!data) { 4598 cb(EVUTIL_EAI_MEMORY, NULL, arg); 4599 return NULL; 4600 } 4601 4602 memcpy(&data->hints, &hints, sizeof(data->hints)); 4603 data->port = (ev_uint16_t)port; 4604 data->ipv4_request.type = DNS_IPv4_A; 4605 data->ipv6_request.type = DNS_IPv6_AAAA; 4606 data->user_cb = cb; 4607 data->user_data = arg; 4608 data->evdns_base = dns_base; 4609 4610 want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME); 4611 4612 /* If we are asked for a PF_UNSPEC address, we launch two requests in 4613 * parallel: one for an A address and one for an AAAA address. We 4614 * can't send just one request, since many servers only answer one 4615 * question per DNS request. 4616 * 4617 * Once we have the answer to one request, we allow for a short 4618 * timeout before we report it, to see if the other one arrives. If 4619 * they both show up in time, then we report both the answers. 4620 * 4621 * If too many addresses of one type time out or fail, we should stop 4622 * launching those requests. (XXX we don't do that yet.) 4623 */ 4624 4625 if (hints.ai_family != PF_INET6) { 4626 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p", 4627 nodename, &data->ipv4_request); 4628 4629 data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base, 4630 nodename, 0, evdns_getaddrinfo_gotresolve, 4631 &data->ipv4_request); 4632 if (want_cname) 4633 data->ipv4_request.r->current_req->put_cname_in_ptr = 4634 &data->cname_result; 4635 } 4636 if (hints.ai_family != PF_INET) { 4637 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p", 4638 nodename, &data->ipv6_request); 4639 4640 data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base, 4641 nodename, 0, evdns_getaddrinfo_gotresolve, 4642 &data->ipv6_request); 4643 if (want_cname) 4644 data->ipv6_request.r->current_req->put_cname_in_ptr = 4645 &data->cname_result; 4646 } 4647 4648 evtimer_assign(&data->timeout, dns_base->event_base, 4649 evdns_getaddrinfo_timeout_cb, data); 4650 4651 if (data->ipv4_request.r || data->ipv6_request.r) { 4652 return data; 4653 } else { 4654 mm_free(data); 4655 cb(EVUTIL_EAI_FAIL, NULL, arg); 4656 return NULL; 4657 } 4658 } 4659 4660 void 4661 evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data) 4662 { 4663 EVDNS_LOCK(data->evdns_base); 4664 if (data->request_done) { 4665 EVDNS_UNLOCK(data->evdns_base); 4666 return; 4667 } 4668 event_del(&data->timeout); 4669 data->user_canceled = 1; 4670 if (data->ipv4_request.r) 4671 evdns_cancel_request(data->evdns_base, data->ipv4_request.r); 4672 if (data->ipv6_request.r) 4673 evdns_cancel_request(data->evdns_base, data->ipv6_request.r); 4674 EVDNS_UNLOCK(data->evdns_base); 4675 } 4676
