src/ext/eventdns.c

   1 /* READ THIS COMMENT BEFORE HACKING THIS FILE.
   2  *
   3  * This eventdns.c copy has diverged a bit from Libevent's version, and it's
   4  * no longer easy to resynchronize them.  Once Tor requires Libevent 2.0, we
   5  * will just dump this file and use Libevent's evdns code.
   6  *
   7  * Therefore, you probably shouldn't make any change here without making it to
   8  * Libevent as well: it's not good for the implementation to diverge even
   9  * more.  Also, we can't shouldn't wantonly the API here (since Libevent APIs
  10  * can't change in ways that break user behavior).  Also, we shouldn't bother
  11  * with cosmetic changes: the whole module is slated for demolition, so
  12  * there's no point dusting the linebreaks or re-painting the parser.
  13  *
  14  * (We can't just drop the Libevent 2.0 evdns implementation in here instead,
  15  * since it depends pretty heavily on parts of Libevent 2.0.)
  16  */
  17
  18 /* Async DNS Library
  19  * Adam Langley <agl@imperialviolet.org>
  20  * Public Domain code
  21  *
  22  * This software is Public Domain. To view a copy of the public domain dedication,
  23  * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
  24  * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
  25  *
  26  * I ask and expect, but do not require, that all derivative works contain an
  27  * attribution similar to:
  28  *      Parts developed by Adam Langley <agl@imperialviolet.org>
  29  *
  30  * You may wish to replace the word "Parts" with something else depending on
  31  * the amount of original code.
  32  *
  33  * (Derivative works does not include programs which link against, run or include
  34  * the source verbatim in their source distributions)
  35  *
  36  * Version: 0.1b
  37  */
  38
  39 #include "eventdns_tor.h"
  40 #include "util.h"
  41 #include <sys/types.h>
  42 /* #define NDEBUG */
  43
  44 #ifndef DNS_USE_CPU_CLOCK_FOR_ID
  45 #ifndef DNS_USE_GETTIMEOFDAY_FOR_ID
  46 #ifndef DNS_USE_OPENSSL_FOR_ID
  47 #error Must configure at least one id generation method.
  48 #error Please see the documentation.
  49 #endif
  50 #endif
  51 #endif
  52
  53 /* #define _POSIX_C_SOURCE 200507 */
  54 #define _GNU_SOURCE
  55
  56 #ifdef DNS_USE_CPU_CLOCK_FOR_ID
  57 #ifdef DNS_USE_OPENSSL_FOR_ID
  58 #error Multiple id options selected
  59 #endif
  60 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
  61 #error Multiple id options selected
  62 #endif
  63 #include <time.h>
  64 #endif
  65
  66 #ifdef DNS_USE_OPENSSL_FOR_ID
  67 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
  68 #error Multiple id options selected
  69 #endif
  70 #include <openssl/rand.h>
  71 #endif
  72
  73 #include <string.h>
  74 #ifdef HAVE_FCNTL_H
  75 #include <fcntl.h>
  76 #endif
  77 #ifdef HAVE_SYS_TIME_H
  78 #include <sys/time.h>
  79 #endif
  80 #ifdef HAVE_STDINT_H
  81 #include <stdint.h>
  82 #endif
  83 #include <stdlib.h>
  84 #include <errno.h>
  85 #include <assert.h>
  86 #ifdef HAVE_UNISTD_H
  87 #include <unistd.h>
  88 #endif
  89 #ifdef HAVE_LIMITS_H
  90 #include <limits.h>
  91 #endif
  92 #include <sys/stat.h>
  93 #include <ctype.h>
  94 #include <stdio.h>
  95 #include <stdarg.h>
  96
  97 #include "eventdns.h"
  98
  99 #ifdef _WIN32
 100 #include <windows.h>
 101 #include <winsock2.h>
 102 #include <iphlpapi.h>
 103 #else
 104 #include <sys/socket.h>
 105 #include <netinet/in.h>
 106 #include <arpa/inet.h>
 107 #endif
 108
 109 #ifdef HAVE_NETINET_IN6_H
 110 #include <netinet/in6.h>
 111 #endif
 112
 113 #ifdef _WIN32
 114 typedef int socklen_t;
 115 #endif
 116
 117 #define EVDNS_LOG_DEBUG 0
 118 #define EVDNS_LOG_WARN 1
 119
 120 #ifndef HOST_NAME_MAX
 121 #define HOST_NAME_MAX 255
 122 #endif
 123
 124 #ifndef NDEBUG
 125 #include <stdio.h>
 126 #endif
 127
 128 /* for debugging possible memory leaks. */
 129 #define mm_malloc(x) tor_malloc(x)
 130 #define mm_realloc(x,y) tor_realloc((x),(y))
 131 #define mm_free(x) tor_free(x)
 132 #define mm_strdup(x) tor_strdup(x)
 133 #define _mm_free(x) tor_free_(x)
 134
 135 #undef MIN
 136 #define MIN(a,b) ((a)<(b)?(a):(b))
 137
 138 #if 0
 139 #ifdef __USE_ISOC99B
 140 /* libevent doesn't work without this */
 141 typedef uint8_t u_char;
 142 typedef unsigned int uint;
 143 #endif
 144 #endif
 145 #include <event.h>
 146
 147 #define u64 uint64_t
 148 #define u32 uint32_t
 149 #define u16 uint16_t
 150 #define u8      uint8_t
 151
 152 #define MAX_ADDRS 4      /* maximum number of addresses from a single packet */
 153 /* which we bother recording */
 154
 155 #define TYPE_A          EVDNS_TYPE_A
 156 #define TYPE_CNAME      5
 157 #define TYPE_PTR        EVDNS_TYPE_PTR
 158 #define TYPE_AAAA       EVDNS_TYPE_AAAA
 159
 160 #define CLASS_INET      EVDNS_CLASS_INET
 161
 162 #define CLEAR(x) do { memset((x), 0xF0, sizeof(*(x))); } while(0)
 163
 164 struct evdns_request {
 165         u8 *request; /* the dns packet data */
 166         unsigned int request_len;
 167         int reissue_count;
 168         int tx_count;  /* the number of times that this packet has been sent */
 169         unsigned int request_type; /* TYPE_PTR or TYPE_A */
 170         void *user_pointer;      /* the pointer given to us for this request */
 171         evdns_callback_type user_callback;
 172         struct nameserver *ns;  /* the server which we last sent it */
 173
 174         /* elements used by the searching code */
 175         int search_index;
 176         struct search_state *search_state;
 177         char *search_origname;  /* needs to be mm_free()ed */
 178         int search_flags;
 179
 180         /* these objects are kept in a circular list */
 181         struct evdns_request *next, *prev;
 182
 183         struct event timeout_event;
 184
 185         u16 trans_id;  /* the transaction id */
 186         char request_appended;  /* true if the request pointer is data which follows this struct */
 187         char transmit_me;  /* needs to be transmitted */
 188 };
 189
 190 #ifndef HAVE_STRUCT_IN6_ADDR
 191 struct in6_addr {
 192         u8 s6_addr[16];
 193 };
 194 #endif
 195
 196 struct reply {
 197         unsigned int type;
 198         unsigned int have_answer;
 199         union {
 200                 struct {
 201                         u32 addrcount;
 202                         u32 addresses[MAX_ADDRS];
 203                 } a;
 204                 struct {
 205                         u32 addrcount;
 206                         struct in6_addr addresses[MAX_ADDRS];
 207                 } aaaa;
 208                 struct {
 209                         char name[HOST_NAME_MAX];
 210                 } ptr;
 211         } data;
 212 };
 213
 214 struct nameserver {
 215         int socket;      /* a connected UDP socket */
 216         struct sockaddr_storage address;
 217         int failed_times;  /* number of times which we have given this server a chance */
 218         int timedout;  /* number of times in a row a request has timed out */
 219         struct event event;
 220         /* these objects are kept in a circular list */
 221         struct nameserver *next, *prev;
 222         struct event timeout_event; /* used to keep the timeout for */
 223                                                                 /* when we next probe this server. */
 224                                                                 /* Valid if state == 0 */
 225         char state;      /* zero if we think that this server is down */
 226         char choked;  /* true if we have an EAGAIN from this server's socket */
 227         char write_waiting;      /* true if we are waiting for EV_WRITE events */
 228 };
 229
 230 static struct evdns_request *req_head = NULL, *req_waiting_head = NULL;
 231 static struct nameserver *server_head = NULL;
 232
 233 /* Represents a local port where we're listening for DNS requests. Right now, */
 234 /* only UDP is supported. */
 235 struct evdns_server_port {
 236         int socket; /* socket we use to read queries and write replies. */
 237         int refcnt; /* reference count. */
 238         char choked; /* Are we currently blocked from writing? */
 239         char closing; /* Are we trying to close this port, pending writes? */
 240         evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
 241         void *user_data; /* Opaque pointer passed to user_callback */
 242         struct event event; /* Read/write event */
 243         /* circular list of replies that we want to write. */
 244         struct server_request *pending_replies;
 245 };
 246
 247 /* Represents part of a reply being built.      (That is, a single RR.) */
 248 struct server_reply_item {
 249         struct server_reply_item *next; /* next item in sequence. */
 250         char *name; /* name part of the RR */
 251         u16 type : 16; /* The RR type */
 252         u16 class : 16; /* The RR class (usually CLASS_INET) */
 253         u32 ttl; /* The RR TTL */
 254         char is_name; /* True iff data is a label */
 255         u16 datalen; /* Length of data; -1 if data is a label */
 256         void *data; /* The contents of the RR */
 257 };
 258
 259 /* Represents a request that we've received as a DNS server, and holds */
 260 /* the components of the reply as we're constructing it. */
 261 struct server_request {
 262         /* Pointers to the next and previous entries on the list of replies */
 263         /* that we're waiting to write.  Only set if we have tried to respond */
 264         /* and gotten EAGAIN. */
 265         struct server_request *next_pending;
 266         struct server_request *prev_pending;
 267
 268         u16 trans_id; /* Transaction id. */
 269         struct evdns_server_port *port; /* Which port received this request on? */
 270         struct sockaddr_storage addr; /* Where to send the response */
 271         socklen_t addrlen; /* length of addr */
 272
 273         int n_answer; /* how many answer RRs have been set? */
 274         int n_authority; /* how many authority RRs have been set? */
 275         int n_additional; /* how many additional RRs have been set? */
 276
 277         struct server_reply_item *answer; /* linked list of answer RRs */
 278         struct server_reply_item *authority; /* linked list of authority RRs */
 279         struct server_reply_item *additional; /* linked list of additional RRs */
 280
 281         /* Constructed response.  Only set once we're ready to send a reply. */
 282         /* Once this is set, the RR fields are cleared, and no more should be set. */
 283         char *response;
 284         size_t response_len;
 285
 286         /* Caller-visible fields: flags, questions. */
 287         struct evdns_server_request base;
 288 };
 289
 290 /* helper macro */
 291 #define OFFSET_OF(st, member) ((off_t) (((char*)&((st*)0)->member)-(char*)0))
 292
 293 /* Given a pointer to an evdns_server_request, get the corresponding */
 294 /* server_request. */
 295 #define TO_SERVER_REQUEST(base_ptr)                                                                             \
 296         ((struct server_request*)                                                                                       \
 297          (((char*)(base_ptr) - OFFSET_OF(struct server_request, base))))
 298
 299 /* The number of good nameservers that we have */
 300 static int global_good_nameservers = 0;
 301
 302 /* inflight requests are contained in the req_head list */
 303 /* and are actually going out across the network */
 304 static int global_requests_inflight = 0;
 305 /* requests which aren't inflight are in the waiting list */
 306 /* and are counted here */
 307 static int global_requests_waiting = 0;
 308
 309 static int global_max_requests_inflight = 64;
 310
 311 static struct timeval global_timeout = {5, 0};  /* 5 seconds */
 312 static int global_max_reissues = 1;     /* a reissue occurs when we get some errors from the server */
 313 static int global_max_retransmits = 3;  /* number of times we'll retransmit a request which timed out */
 314 /* number of timeouts in a row before we consider this server to be down */
 315 static int global_max_nameserver_timeout = 3;
 316
 317 /* true iff we should use the 0x20 hack. */
 318 static int global_randomize_case = 1;
 319
 320 /* These are the timeout values for nameservers. If we find a nameserver is down */
 321 /* we try to probe it at intervals as given below. Values are in seconds. */
 322 static const struct timeval global_nameserver_timeouts[] = {{10, 0}, {60, 0}, {300, 0}, {900, 0}, {3600, 0}};
 323 static const int global_nameserver_timeouts_length = (int)(sizeof(global_nameserver_timeouts)/sizeof(struct timeval));
 324
 325 static struct nameserver *nameserver_pick(void);
 326 static void evdns_request_insert(struct evdns_request *req, struct evdns_request **head);
 327 static void nameserver_ready_callback(int fd, short events, void *arg);
 328 static int evdns_transmit(void);
 329 static int evdns_request_transmit(struct evdns_request *req);
 330 static void nameserver_send_probe(struct nameserver *const ns);
 331 static void search_request_finished(struct evdns_request *const);
 332 static int search_try_next(struct evdns_request *const req);
 333 static int search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg);
 334 static void evdns_requests_pump_waiting_queue(void);
 335 static u16 transaction_id_pick(void);
 336 static struct evdns_request *request_new(int type, const char *name, int flags, evdns_callback_type callback, void *ptr);
 337 static void request_submit(struct evdns_request *req);
 338
 339 static int server_request_free(struct server_request *req);
 340 static void server_request_free_answers(struct server_request *req);
 341 static void server_port_free(struct evdns_server_port *port);
 342 static void server_port_ready_callback(int fd, short events, void *arg);
 343
 344 static int strtoint(const char *const str);
 345
 346 #ifdef _WIN32
 347 static int
 348 last_error(int sock)
 349 {
 350         int optval, optvallen=sizeof(optval);
 351         int err = WSAGetLastError();
 352         if (err == WSAEWOULDBLOCK && sock >= 0) {
 353                 if (getsockopt(sock, SOL_SOCKET, SO_ERROR, (void*)&optval,
 354                                            &optvallen))
 355                         return err;
 356                 if (optval)
 357                         return optval;
 358         }
 359         return err;
 360
 361 }
 362 static int
 363 error_is_eagain(int err)
 364 {
 365         return err == EAGAIN || err == WSAEWOULDBLOCK;
 366 }
 367 #define inet_aton(c, addr) tor_inet_aton((c), (addr))
 368 #define CLOSE_SOCKET(x) closesocket(x)
 369 #else
 370 #define last_error(sock) (errno)
 371 #if EAGAIN != EWOULDBLOCK
 372 #define error_is_eagain(err) ((err) == EAGAIN || (err) == EWOULDBLOCK)
 373 #else
 374 #define error_is_eagain(err) ((err) == EAGAIN)
 375 #endif
 376 #define CLOSE_SOCKET(x) close(x)
 377 #endif
 378
 379 #define ISSPACE(c) TOR_ISSPACE(c)
 380 #define ISDIGIT(c) TOR_ISDIGIT(c)
 381 #define ISALPHA(c) TOR_ISALPHA(c)
 382 #define TOLOWER(c) TOR_TOLOWER(c)
 383 #define TOUPPER(c) TOR_TOUPPER(c)
 384
 385 #ifndef NDEBUG
 386 static const char *
 387 debug_ntoa(u32 address)
 388 {
 389         static char buf[32];
 390         u32 a = ntohl(address);
 391         snprintf(buf, sizeof(buf), "%d.%d.%d.%d",
 392                         (int)(u8)((a>>24)&0xff),
 393                         (int)(u8)((a>>16)&0xff),
 394                         (int)(u8)((a>>8 )&0xff),
 395                         (int)(u8)((a    )&0xff));
 396         return buf;
 397 }
 398 static const char *
 399 debug_ntop(const struct sockaddr *sa)
 400 {
 401         if (sa->sa_family == AF_INET) {
 402                 struct sockaddr_in *sin = (struct sockaddr_in *) sa;
 403                 return debug_ntoa(sin->sin_addr.s_addr);
 404         }
 405         if (sa->sa_family == AF_INET6) {
 406                 /* Tor-specific.  In libevent, add more check code. */
 407                 static char buf[128];
 408                 struct sockaddr_in6 *sin = (struct sockaddr_in6 *) sa;
 409                 tor_inet_ntop(AF_INET6, &sin->sin6_addr, buf, sizeof(buf));
 410                 return buf;
 411         }
 412         return "<unknown>";
 413 }
 414 #endif
 415
 416 static evdns_debug_log_fn_type evdns_log_fn = NULL;
 417
 418 void
 419 evdns_set_log_fn(evdns_debug_log_fn_type fn)
 420 {
 421         evdns_log_fn = fn;
 422 }
 423
 424 #ifdef __GNUC__
 425 #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3)))
 426 #else
 427 #define EVDNS_LOG_CHECK
 428 #endif
 429
 430 static void evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK;
 431 static void
 432 evdns_log(int warn, const char *fmt, ...)
 433 {
 434         va_list args;
 435         static char buf[512];
 436         if (!evdns_log_fn)
 437                 return;
 438         va_start(args,fmt);
 439 #ifdef _WIN32
 440         _vsnprintf(buf, sizeof(buf), fmt, args);
 441 #else
 442         vsnprintf(buf, sizeof(buf), fmt, args);
 443 #endif
 444         buf[sizeof(buf)-1] = '\0';
 445         evdns_log_fn(warn, buf);
 446         va_end(args);
 447 }
 448
 449 static int
 450 sockaddr_eq(const struct sockaddr *sa1, const struct sockaddr *sa2,
 451                         int include_port)
 452 {
 453         if (sa1->sa_family != sa2->sa_family)
 454                 return 0;
 455         if (sa1->sa_family == AF_INET) {
 456                 const struct sockaddr_in *sin1, *sin2;
 457                 sin1 = (const struct sockaddr_in *)sa1;
 458                 sin2 = (const struct sockaddr_in *)sa2;
 459                 if (sin1->sin_addr.s_addr != sin2->sin_addr.s_addr)
 460                         return 0;
 461                 else if (include_port && sin1->sin_port != sin2->sin_port)
 462                         return 0;
 463                 else
 464                         return 1;
 465         }
 466 #ifdef AF_INET6
 467         if (sa1->sa_family == AF_INET6) {
 468                 const struct sockaddr_in6 *sin1, *sin2;
 469                 sin1 = (const struct sockaddr_in6 *)sa1;
 470                 sin2 = (const struct sockaddr_in6 *)sa2;
 471                 if (tor_memneq(sin1->sin6_addr.s6_addr, sin2->sin6_addr.s6_addr, 16))
 472                         return 0;
 473                 else if (include_port && sin1->sin6_port != sin2->sin6_port)
 474                         return 0;
 475                 else
 476                         return 1;
 477         }
 478 #endif
 479         return 1;
 480 }
 481
 482 #define add_timeout_event(s, to)                                \
 483         (event_add(&(s)->timeout_event, (to)))
 484 #define del_timeout_event(s)                                    \
 485         (event_del(&(s)->timeout_event))
 486
 487 /* This walks the list of inflight requests to find the */
 488 /* one with a matching transaction id. Returns NULL on */
 489 /* failure */
 490 static struct evdns_request *
 491 request_find_from_trans_id(u16 trans_id) {
 492         struct evdns_request *req = req_head, *const started_at = req_head;
 493
 494         if (req) {
 495                 do {
 496                         if (req->trans_id == trans_id) return req;
 497                         req = req->next;
 498                 } while (req != started_at);
 499         }
 500
 501         return NULL;
 502 }
 503
 504 /* a libevent callback function which is called when a nameserver */
 505 /* has gone down and we want to test if it has came back to life yet */
 506 static void
 507 nameserver_prod_callback(int fd, short events, void *arg) {
 508         struct nameserver *const ns = (struct nameserver *) arg;
 509         (void)fd;
 510         (void)events;
 511
 512         nameserver_send_probe(ns);
 513 }
 514
 515 /* a libevent callback which is called when a nameserver probe (to see if */
 516 /* it has come back to life) times out. We increment the count of failed_times */
 517 /* and wait longer to send the next probe packet. */
 518 static void
 519 nameserver_probe_failed(struct nameserver *const ns) {
 520         const struct timeval * timeout;
 521         del_timeout_event(ns);
 522
 523         if (ns->state == 1) {
 524                 /* This can happen if the nameserver acts in a way which makes us mark */
 525                 /* it as bad and then starts sending good replies. */
 526                 return;
 527         }
 528
 529         timeout =
 530                 &global_nameserver_timeouts[MIN(ns->failed_times,
 531                                                                                 global_nameserver_timeouts_length - 1)];
 532         ns->failed_times++;
 533
 534         if (add_timeout_event(ns, (struct timeval *) timeout) < 0) {
 535                 evdns_log(EVDNS_LOG_WARN,
 536                         "Error from libevent when adding timer event for %s",
 537                         debug_ntop((struct sockaddr *)&ns->address));
 538                 /* ???? Do more? */
 539         }
 540 }
 541
 542 /* called when a nameserver has been deemed to have failed. For example, too */
 543 /* many packets have timed out etc */
 544 static void
 545 nameserver_failed(struct nameserver *const ns, const char *msg) {
 546         struct evdns_request *req, *started_at;
 547         /* if this nameserver has already been marked as failed */
 548         /* then don't do anything */
 549         if (!ns->state) return;
 550
 551         evdns_log(EVDNS_LOG_WARN, "Nameserver %s has failed: %s",
 552                 debug_ntop((struct sockaddr *)&ns->address), msg);
 553         global_good_nameservers--;
 554         assert(global_good_nameservers >= 0);
 555         if (global_good_nameservers == 0) {
 556                 evdns_log(EVDNS_LOG_WARN, "All nameservers have failed");
 557         }
 558
 559         ns->state = 0;
 560         ns->failed_times = 1;
 561
 562         if (add_timeout_event(ns, (struct timeval *) &global_nameserver_timeouts[0]) < 0) {
 563                 evdns_log(EVDNS_LOG_WARN,
 564                         "Error from libevent when adding timer event for %s",
 565                         debug_ntop((struct sockaddr *)&ns->address));
 566                 /* ???? Do more? */
 567         }
 568
 569         /* walk the list of inflight requests to see if any can be reassigned to */
 570         /* a different server. Requests in the waiting queue don't have a */
 571         /* nameserver assigned yet */
 572
 573         /* if we don't have *any* good nameservers then there's no point */
 574         /* trying to reassign requests to one */
 575         if (!global_good_nameservers) return;
 576
 577         req = req_head;
 578         started_at = req_head;
 579         if (req) {
 580                 do {
 581                         if (req->tx_count == 0 && req->ns == ns) {
 582                                 /* still waiting to go out, can be moved */
 583                                 /* to another server */
 584                                 req->ns = nameserver_pick();
 585                         }
 586                         req = req->next;
 587                 } while (req != started_at);
 588         }
 589 }
 590
 591 static void
 592 nameserver_up(struct nameserver *const ns) {
 593         if (ns->state) return;
 594         evdns_log(EVDNS_LOG_WARN, "Nameserver %s is back up",
 595                 debug_ntop((struct sockaddr *)&ns->address));
 596         del_timeout_event(ns);
 597         ns->state = 1;
 598         ns->failed_times = 0;
 599         ns->timedout = 0;
 600         global_good_nameservers++;
 601 }
 602
 603 static void
 604 request_trans_id_set(struct evdns_request *const req, const u16 trans_id) {
 605         req->trans_id = trans_id;
 606         *((u16 *) req->request) = htons(trans_id);
 607 }
 608
 609 /* Called to remove a request from a list and dealloc it. */
 610 /* head is a pointer to the head of the list it should be */
 611 /* removed from or NULL if the request isn't in a list. */
 612 static void
 613 request_finished(struct evdns_request *const req, struct evdns_request **head) {
 614         if (head) {
 615                 if (req->next == req) {
 616                         /* only item in the list */
 617                         *head = NULL;
 618                 } else {
 619                         req->next->prev = req->prev;
 620                         req->prev->next = req->next;
 621                         if (*head == req) *head = req->next;
 622                 }
 623         }
 624
 625         evdns_log(EVDNS_LOG_DEBUG, "Removing timeout for request %lx",
 626                 (unsigned long) req);
 627         del_timeout_event(req);
 628
 629         search_request_finished(req);
 630         global_requests_inflight--;
 631
 632         if (!req->request_appended) {
 633                 /* need to free the request data on it's own */
 634                 mm_free(req->request);
 635         } else {
 636                 /* the request data is appended onto the header */
 637                 /* so everything gets mm_free()ed when we: */
 638         }
 639
 640         CLEAR(req);
 641         _mm_free(req);
 642
 643         evdns_requests_pump_waiting_queue();
 644 }
 645
 646 /* This is called when a server returns a funny error code. */
 647 /* We try the request again with another server. */
 648 /* */
 649 /* return: */
 650 /* 0 ok */
 651 /* 1 failed/reissue is pointless */
 652 static int
 653 request_reissue(struct evdns_request *req) {
 654         const struct nameserver *const last_ns = req->ns;
 655         /* the last nameserver should have been marked as failing */
 656         /* by the caller of this function, therefore pick will try */
 657         /* not to return it */
 658         req->ns = nameserver_pick();
 659         if (req->ns == last_ns) {
 660                 /* ... but pick did return it */
 661                 /* not a lot of point in trying again with the */
 662                 /* same server */
 663                 return 1;
 664         }
 665
 666         req->reissue_count++;
 667         req->tx_count = 0;
 668         req->transmit_me = 1;
 669
 670         return 0;
 671 }
 672
 673 /* this function looks for space on the inflight queue and promotes */
 674 /* requests from the waiting queue if it can. */
 675 static void
 676 evdns_requests_pump_waiting_queue(void) {
 677         while (global_requests_inflight < global_max_requests_inflight &&
 678                 global_requests_waiting) {
 679                 struct evdns_request *req;
 680                 /* move a request from the waiting queue to the inflight queue */
 681                 assert(req_waiting_head);
 682                 if (req_waiting_head->next == req_waiting_head) {
 683                         /* only one item in the queue */
 684                         req = req_waiting_head;
 685                         req_waiting_head = NULL;
 686                 } else {
 687                         req = req_waiting_head;
 688                         req->next->prev = req->prev;
 689                         req->prev->next = req->next;
 690                         req_waiting_head = req->next;
 691                 }
 692
 693                 global_requests_waiting--;
 694                 global_requests_inflight++;
 695
 696                 req->ns = nameserver_pick();
 697                 request_trans_id_set(req, transaction_id_pick());
 698
 699                 evdns_request_insert(req, &req_head);
 700                 evdns_request_transmit(req);
 701                 evdns_transmit();
 702         }
 703 }
 704
 705 static void
 706 reply_callback(struct evdns_request *const req, u32 ttl, u32 err, struct reply *reply) {
 707         switch (req->request_type) {
 708         case TYPE_A:
 709                 if (reply)
 710                         req->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
 711                                                            reply->data.a.addrcount, ttl,
 712                                                            reply->data.a.addresses,
 713                                                            req->user_pointer);
 714                 else
 715                         req->user_callback(err, 0, 0, 0, NULL, req->user_pointer);
 716                 return;
 717         case TYPE_PTR:
 718                 if (reply) {
 719                         char *name = reply->data.ptr.name;
 720                         req->user_callback(DNS_ERR_NONE, DNS_PTR, 1, ttl,
 721                                                            &name, req->user_pointer);
 722                 } else {
 723                         req->user_callback(err, 0, 0, 0, NULL,
 724                                                            req->user_pointer);
 725                 }
 726                 return;
 727         case TYPE_AAAA:
 728                 if (reply)
 729                         req->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA,
 730                                                            reply->data.aaaa.addrcount, ttl,
 731                                                            reply->data.aaaa.addresses,
 732                                                            req->user_pointer);
 733                 else
 734                         req->user_callback(err, 0, 0, 0, NULL, req->user_pointer);
 735                 return;
 736         }
 737         assert(0);
 738 }
 739
 740 /* this processes a parsed reply packet */
 741 static void
 742 reply_handle(struct evdns_request *const req, u16 flags, u32 ttl, struct reply *reply) {
 743         int error;
 744         static const int error_codes[] = {DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, DNS_ERR_NOTIMPL, DNS_ERR_REFUSED};
 745
 746         if (flags & 0x020f || !reply || !reply->have_answer) {
 747                 /* there was an error */
 748                 if (flags & 0x0200) {
 749                         error = DNS_ERR_TRUNCATED;
 750                 } else {
 751                         u16 error_code = (flags & 0x000f) - 1;
 752                         if (error_code > 4) {
 753                                 error = DNS_ERR_UNKNOWN;
 754                         } else {
 755                                 error = error_codes[error_code];
 756                         }
 757                 }
 758
 759                 switch(error) {
 760                 case DNS_ERR_NOTIMPL:
 761                 case DNS_ERR_REFUSED:
 762                         /* we regard these errors as marking a bad nameserver */
 763                         if (req->reissue_count < global_max_reissues) {
 764                                 char msg[64];
 765                                 snprintf(msg, sizeof(msg), "Bad response %d (%s)",
 766                                                  error, evdns_err_to_string(error));
 767                                 nameserver_failed(req->ns, msg);
 768                                 if (!request_reissue(req)) return;
 769                         }
 770                         break;
 771                 case DNS_ERR_SERVERFAILED:
 772                         /* rcode 2 (servfailed) sometimes means "we are broken" and
 773                          * sometimes (with some binds) means "that request was very
 774                          * confusing."  Treat this as a timeout, not a failure.
 775                          */
 776                         /*XXXX refactor the parts of */
 777                         evdns_log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver %s; "
 778                                 "will allow the request to time out.",
 779                                 debug_ntop((struct sockaddr *)&req->ns->address));
 780                         break;
 781                 default:
 782                         /* we got a good reply from the nameserver */
 783                         nameserver_up(req->ns);
 784                 }
 785
 786                 if (req->search_state && req->request_type != TYPE_PTR) {
 787                         /* if we have a list of domains to search in, try the next one */
 788                         if (!search_try_next(req)) {
 789                                 /* a new request was issued so this request is finished and */
 790                                 /* the user callback will be made when that request (or a */
 791                                 /* child of it) finishes. */
 792                                 request_finished(req, &req_head);
 793                                 return;
 794                         }
 795                 }
 796
 797                 /* all else failed. Pass the failure up */
 798                 reply_callback(req, 0, error, NULL);
 799                 request_finished(req, &req_head);
 800         } else {
 801                 /* all ok, tell the user */
 802                 reply_callback(req, ttl, 0, reply);
 803                 nameserver_up(req->ns);
 804                 request_finished(req, &req_head);
 805         }
 806 }
 807
 808 static INLINE int
 809 name_parse(u8 *packet, int length, int *idx, char *name_out, size_t name_out_len) {
 810         int name_end = -1;
 811         int j = *idx;
 812         int ptr_count = 0;
 813 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while(0)
 814 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while(0)
 815 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while(0)
 816
 817         char *cp = name_out;
 818         const char *const end = name_out + name_out_len;
 819
 820         /* Normally, names are a series of length prefixed strings terminated */
 821         /* with a length of 0 (the lengths are u8's < 63). */
 822         /* However, the length can start with a pair of 1 bits and that */
 823         /* means that the next 14 bits are a pointer within the current */
 824         /* packet. */
 825
 826         for(;;) {
 827                 u8 label_len;
 828                 if (j >= length) return -1;
 829                 GET8(label_len);
 830                 if (!label_len) break;
 831                 if (label_len & 0xc0) {
 832                         u8 ptr_low;
 833                         GET8(ptr_low);
 834                         if (name_end < 0) name_end = j;
 835                         j = (((int)label_len & 0x3f) << 8) + ptr_low;
 836                         /* Make sure that the target offset is in-bounds. */
 837                         if (j < 0 || j >= length) return -1;
 838                         /* If we've jumped more times than there are characters in the
 839                          * message, we must have a loop. */
 840                         if (++ptr_count > length) return -1;
 841                         continue;
 842                 }
 843                 if (label_len > 63) return -1;
 844                 if (cp != name_out) {
 845                         if (cp >= name_out + name_out_len - 1) return -1;
 846                         *cp++ = '.';
 847                 }
 848                 if (label_len > name_out_len ||
 849                         cp >= name_out + name_out_len - label_len) return -1;
 850                 memcpy(cp, packet + j, label_len);
 851                 cp += label_len;
 852                 j += label_len;
 853         }
 854         if (cp >= end) return -1;
 855         *cp = '\0';
 856         if (name_end < 0)
 857                 *idx = j;
 858         else
 859                 *idx = name_end;
 860         return 0;
 861  err:
 862         return -1;
 863 }
 864
 865 /* parses a raw reply from a nameserver. */
 866 static int
 867 reply_parse(u8 *packet, int length) {
 868         int j = 0;      /* index into packet */
 869         int k;
 870         u16 _t;  /* used by the macros */
 871         u32 _t32;  /* used by the macros */
 872         char tmp_name[256], cmp_name[256]; /* used by the macros */
 873
 874         u16 trans_id, questions, answers, authority, additional, datalength;
 875         u16 flags = 0;
 876         u32 ttl, ttl_r = 0xffffffff;
 877         struct reply reply;
 878         struct evdns_request *req = NULL;
 879         unsigned int i;
 880         int name_matches = 0;
 881
 882         GET16(trans_id);
 883         GET16(flags);
 884         GET16(questions);
 885         GET16(answers);
 886         GET16(authority);
 887         GET16(additional);
 888         (void) authority; /* suppress "unused variable" warnings. */
 889         (void) additional; /* suppress "unused variable" warnings. */
 890
 891         req = request_find_from_trans_id(trans_id);
 892         /* if no request, can't do anything. */
 893         if (!req) return -1;
 894
 895         memset(&reply, 0, sizeof(reply));
 896
 897         /* If it's not an answer, it doesn't go with any of our requests. */
 898         if (!(flags & 0x8000)) return -1;  /* must be an answer */
 899         if (flags & 0x020f) {
 900                 /* there was an error */
 901                 goto err;
 902         }
 903         /* if (!answers) return; */  /* must have an answer of some form */
 904
 905         /* This macro skips a name in the DNS reply. */
 906 #define GET_NAME \
 907         do { tmp_name[0] = '\0';                                \
 908                 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\
 909                         goto err;                               \
 910         } while(0)
 911 #define TEST_NAME \
 912         do { tmp_name[0] = '\0';                                \
 913                 cmp_name[0] = '\0';                             \
 914                 k = j;                                          \
 915                 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\
 916                         goto err;                                       \
 917                 if (name_parse(req->request, req->request_len, &k, cmp_name, sizeof(cmp_name))<0)       \
 918                         goto err;                               \
 919                 if (global_randomize_case) {                                                    \
 920                         if (strcmp(tmp_name, cmp_name) == 0)                            \
 921                                 name_matches = 1; /* we ignore mismatching names */     \
 922                 } else {                                                                                                        \
 923                         if (strcasecmp(tmp_name, cmp_name) == 0)                                \
 924                                 name_matches = 1;                                                                       \
 925                 }                                                                                                                       \
 926         } while(0)
 927
 928         reply.type = req->request_type;
 929
 930         /* skip over each question in the reply */
 931         for (i = 0; i < questions; ++i) {
 932                 /* the question looks like
 933                  * <label:name><u16:type><u16:class>
 934                  */
 935                 TEST_NAME;
 936                 j += 4;
 937                 if (j >= length) goto err;
 938         }
 939
 940         if (!name_matches)
 941                 goto err;
 942
 943         /* now we have the answer section which looks like
 944          * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...>
 945          */
 946
 947         for (i = 0; i < answers; ++i) {
 948                 u16 type, class;
 949
 950                 GET_NAME;
 951                 GET16(type);
 952                 GET16(class);
 953                 GET32(ttl);
 954                 GET16(datalength);
 955
 956                 if (type == TYPE_A && class == CLASS_INET) {
 957                         int addrcount, addrtocopy;
 958                         if (req->request_type != TYPE_A) {
 959                                 j += datalength; continue;
 960                         }
 961                         if ((datalength & 3) != 0) /* not an even number of As. */
 962                                 goto err;
 963                         addrcount = datalength >> 2;
 964                         addrtocopy = MIN(MAX_ADDRS - reply.data.a.addrcount, (unsigned)addrcount);
 965
 966                         ttl_r = MIN(ttl_r, ttl);
 967                         /* we only bother with the first four addresses. */
 968                         if (j + 4*addrtocopy > length) goto err;
 969                         memcpy(&reply.data.a.addresses[reply.data.a.addrcount],
 970                                    packet + j, 4*addrtocopy);
 971                         reply.data.a.addrcount += addrtocopy;
 972                         reply.have_answer = 1;
 973                         if (reply.data.a.addrcount == MAX_ADDRS) break;
 974                         j += 4*addrtocopy;
 975                 } else if (type == TYPE_PTR && class == CLASS_INET) {
 976                         if (req->request_type != TYPE_PTR) {
 977                                 j += datalength; continue;
 978                         }
 979                         GET_NAME;
 980                         strlcpy(reply.data.ptr.name, tmp_name,
 981                                         sizeof(reply.data.ptr.name));
 982                         ttl_r = MIN(ttl_r, ttl);
 983                         reply.have_answer = 1;
 984                         break;
 985                 } else if (type == TYPE_AAAA && class == CLASS_INET) {
 986                         int addrcount, addrtocopy;
 987                         if (req->request_type != TYPE_AAAA) {
 988                                 j += datalength; continue;
 989                         }
 990                         if ((datalength & 15) != 0) /* not an even number of AAAAs. */
 991                                 goto err;
 992                         addrcount = datalength >> 4;  /* each address is 16 bytes long */
 993                         addrtocopy = MIN(MAX_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount);
 994                         ttl_r = MIN(ttl_r, ttl);
 995
 996                         /* we only bother with the first four addresses. */
 997                         if (j + 16*addrtocopy > length) goto err;
 998                         memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount],
 999                                    packet + j, 16*addrtocopy);
1000                         reply.data.aaaa.addrcount += addrtocopy;
1001                         reply.have_answer = 1;
1002                         if (reply.data.aaaa.addrcount == MAX_ADDRS) break;
1003                         j += 16*addrtocopy;
1004                 } else {
1005                         /* skip over any other type of resource */
1006                         j += datalength;
1007                 }
1008         }
1009
1010         reply_handle(req, flags, ttl_r, &reply);
1011         return 0;
1012  err:
1013         if (req)
1014                 reply_handle(req, flags, 0, NULL);
1015         return -1;
1016 }
1017
1018 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */
1019 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */
1020 /* callback. */
1021 static int
1022 request_parse(u8 *packet, ssize_t length, struct evdns_server_port *port, struct sockaddr *addr, socklen_t addrlen)
1023 {
1024         int j = 0;      /* index into packet */
1025         u16 _t;  /* used by the macros */
1026         char tmp_name[256]; /* used by the macros */
1027
1028         int i;
1029         u16 trans_id, flags, questions, answers, authority, additional;
1030         struct server_request *server_req = NULL;
1031
1032         /* Get the header fields */
1033         GET16(trans_id);
1034         GET16(flags);
1035         GET16(questions);
1036         GET16(answers);
1037         GET16(authority);
1038         GET16(additional);
1039         (void)additional;
1040         (void)authority;
1041         (void)answers;
1042
1043         if (flags & 0x8000) return -1; /* Must not be an answer. */
1044         flags &= 0x0110; /* Only RD and CD get preserved. */
1045
1046     if (length > INT_MAX)
1047         return -1;
1048
1049         server_req = mm_malloc(sizeof(struct server_request));
1050         if (server_req == NULL) return -1;
1051         memset(server_req, 0, sizeof(struct server_request));
1052
1053         server_req->trans_id = trans_id;
1054         memcpy(&server_req->addr, addr, addrlen);
1055         server_req->addrlen = addrlen;
1056
1057         server_req->base.flags = flags;
1058         server_req->base.nquestions = 0;
1059         server_req->base.questions = mm_malloc(sizeof(struct evdns_server_question *) * questions);
1060         if (server_req->base.questions == NULL)
1061                 goto err;
1062
1063         for (i = 0; i < questions; ++i) {
1064                 u16 type, class;
1065                 struct evdns_server_question *q;
1066                 size_t namelen;
1067                 if (name_parse(packet, (int)length, &j, tmp_name, sizeof(tmp_name))<0)
1068                         goto err;
1069                 GET16(type);
1070                 GET16(class);
1071                 namelen = strlen(tmp_name);
1072                 q = mm_malloc(sizeof(struct evdns_server_question) + namelen);
1073                 if (!q)
1074                         goto err;
1075                 q->type = type;
1076                 q->dns_question_class = class;
1077                 memcpy(q->name, tmp_name, namelen+1);
1078                 server_req->base.questions[server_req->base.nquestions++] = q;
1079         }
1080
1081         /* Ignore answers, authority, and additional. */
1082
1083         server_req->port = port;
1084         port->refcnt++;
1085
1086         /* Only standard queries are supported. */
1087         if (flags & 0x7800) {
1088                 evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL);
1089                 return -1;
1090         }
1091
1092         port->user_callback(&(server_req->base), port->user_data);
1093
1094         return 0;
1095 err:
1096         if (server_req) {
1097                 if (server_req->base.questions) {
1098                         for (i = 0; i < server_req->base.nquestions; ++i)
1099                                 mm_free(server_req->base.questions[i]);
1100                         mm_free(server_req->base.questions);
1101                 }
1102                 CLEAR(server_req);
1103                 mm_free(server_req);
1104         }
1105         return -1;
1106
1107 #undef SKIP_NAME
1108 #undef GET32
1109 #undef GET16
1110 #undef GET8
1111 }
1112
1113 static uint16_t
1114 default_transaction_id_fn(void)
1115 {
1116         u16 trans_id;
1117 #ifdef DNS_USE_CPU_CLOCK_FOR_ID
1118         struct timespec ts;
1119 #ifdef CLOCK_MONOTONIC
1120         if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
1121 #else
1122         if (clock_gettime(CLOCK_REALTIME, &ts) == -1)
1123 #endif
1124         event_err(1, "clock_gettime");
1125         trans_id = ts.tv_nsec & 0xffff;
1126 #endif
1127
1128 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
1129         struct timeval tv;
1130         gettimeofday(&tv, NULL);
1131         trans_id = tv.tv_usec & 0xffff;
1132 #endif
1133
1134 #ifdef DNS_USE_OPENSSL_FOR_ID
1135         if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) {
1136                 /* in the case that the RAND call fails we back */
1137                 /* down to using gettimeofday. */
1138                 /*
1139                   struct timeval tv;
1140                   gettimeofday(&tv, NULL);
1141                   trans_id = tv.tv_usec & 0xffff;
1142                 */
1143                 abort();
1144         }
1145 #endif
1146         return (unsigned short) trans_id;
1147 }
1148
1149 static uint16_t (*trans_id_function)(void) = default_transaction_id_fn;
1150
1151 static void
1152 default_random_bytes_fn(char *buf, size_t n)
1153 {
1154         unsigned i;
1155         for (i = 0; i < n; i += 2) {
1156                 u16 tid = trans_id_function();
1157                 buf[i] = (tid >> 8) & 0xff;
1158                 if (i+1<n)
1159                         buf[i+1] = tid & 0xff;
1160         }
1161 }
1162
1163 static void (*rand_bytes_function)(char *buf, size_t n) =
1164         default_random_bytes_fn;
1165
1166 static u16
1167 trans_id_from_random_bytes_fn(void)
1168 {
1169         u16 tid;
1170         rand_bytes_function((char*) &tid, sizeof(tid));
1171         return tid;
1172 }
1173
1174 void
1175 evdns_set_transaction_id_fn(uint16_t (*fn)(void))
1176 {
1177         if (fn)
1178                 trans_id_function = fn;
1179         else
1180                 trans_id_function = default_transaction_id_fn;
1181         rand_bytes_function = default_random_bytes_fn;
1182 }
1183
1184 void
1185 evdns_set_random_bytes_fn(void (*fn)(char *, size_t))
1186 {
1187         rand_bytes_function = fn;
1188         trans_id_function = trans_id_from_random_bytes_fn;
1189 }
1190
1191 /* Try to choose a strong transaction id which isn't already in flight */
1192 static u16
1193 transaction_id_pick(void) {
1194         for (;;) {
1195                 const struct evdns_request *req = req_head, *started_at;
1196                 u16 trans_id = trans_id_function();
1197
1198                 if (trans_id == 0xffff) continue;
1199                 /* now check to see if that id is already inflight */
1200                 req = started_at = req_head;
1201                 if (req) {
1202                         do {
1203                                 if (req->trans_id == trans_id) break;
1204                                 req = req->next;
1205                         } while (req != started_at);
1206                 }
1207                 /* we didn't find it, so this is a good id */
1208                 if (req == started_at) return trans_id;
1209         }
1210 }
1211
1212 /* choose a namesever to use. This function will try to ignore */
1213 /* nameservers which we think are down and load balance across the rest */
1214 /* by updating the server_head global each time. */
1215 static struct nameserver *
1216 nameserver_pick(void) {
1217         struct nameserver *started_at = server_head, *picked;
1218         if (!server_head) return NULL;
1219
1220         /* if we don't have any good nameservers then there's no */
1221         /* point in trying to find one. */
1222         if (!global_good_nameservers) {
1223                 server_head = server_head->next;
1224                 return server_head;
1225         }
1226
1227         /* remember that nameservers are in a circular list */
1228         for (;;) {
1229                 if (server_head->state) {
1230                         /* we think this server is currently good */
1231                         picked = server_head;
1232                         server_head = server_head->next;
1233                         return picked;
1234                 }
1235
1236                 server_head = server_head->next;
1237                 if (server_head == started_at) {
1238                         /* all the nameservers seem to be down */
1239                         /* so we just return this one and hope for the */
1240                         /* best */
1241                         assert(global_good_nameservers == 0);
1242                         picked = server_head;
1243                         server_head = server_head->next;
1244                         return picked;
1245                 }
1246         }
1247 }
1248
1249 /* this is called when a namesever socket is ready for reading */
1250 static void
1251 nameserver_read(struct nameserver *ns) {
1252         struct sockaddr_storage ss;
1253         struct sockaddr *sa = (struct sockaddr *) &ss;
1254         socklen_t addrlen = sizeof(ss);
1255         u8 packet[1500];
1256
1257         for (;;) {
1258                 const int r =
1259             (int)recvfrom(ns->socket, (void*)packet,
1260                                                   (socklen_t)sizeof(packet), 0,
1261                                                   sa, &addrlen);
1262                 if (r < 0) {
1263                         int err = last_error(ns->socket);
1264                         if (error_is_eagain(err)) return;
1265                         nameserver_failed(ns, tor_socket_strerror(err));
1266                         return;
1267                 }
1268                 /* XXX Match port too? */
1269                 if (!sockaddr_eq(sa, (struct sockaddr*)&ns->address, 0)) {
1270                         evdns_log(EVDNS_LOG_WARN,
1271                                 "Address mismatch on received DNS packet.  Address was %s",
1272                                 debug_ntop(sa));
1273                         return;
1274                 }
1275                 ns->timedout = 0;
1276                 reply_parse(packet, r);
1277         }
1278 }
1279
1280 /* Read a packet from a DNS client on a server port s, parse it, and */
1281 /* act accordingly. */
1282 static void
1283 server_port_read(struct evdns_server_port *s) {
1284         u8 packet[1500];
1285         struct sockaddr_storage addr;
1286         socklen_t addrlen;
1287         ssize_t r;
1288
1289         for (;;) {
1290                 addrlen = (socklen_t)sizeof(struct sockaddr_storage);
1291                 r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0,
1292                                          (struct sockaddr*) &addr, &addrlen);
1293                 if (r < 0) {
1294                         int err = last_error(s->socket);
1295                         if (error_is_eagain(err)) return;
1296                         evdns_log(EVDNS_LOG_WARN, "Error %s (%d) while reading request.",
1297                                 tor_socket_strerror(err), err);
1298                         return;
1299                 }
1300                 request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen);
1301         }
1302 }
1303
1304 /* Try to write all pending replies on a given DNS server port. */
1305 static void
1306 server_port_flush(struct evdns_server_port *port)
1307 {
1308         struct server_request *req = port->pending_replies;
1309         while (req) {
1310                 ssize_t r = sendto(port->socket, req->response, req->response_len, 0,
1311                        (struct sockaddr*) &req->addr, (socklen_t)req->addrlen);
1312                 if (r < 0) {
1313                         int err = last_error(port->socket);
1314                         if (error_is_eagain(err))
1315                                 return;
1316                         evdns_log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", tor_socket_strerror(err), err);
1317                 }
1318                 if (server_request_free(req)) {
1319                         /* we released the last reference to req->port. */
1320                         return;
1321                 } else {
1322                         assert(port->pending_replies != req);
1323                         req = port->pending_replies;
1324                 }
1325         }
1326
1327         /* We have no more pending requests; stop listening for 'writeable' events. */
1328         (void) event_del(&port->event);
1329         CLEAR(&port->event);
1330         event_set(&port->event, port->socket, EV_READ | EV_PERSIST,
1331                           server_port_ready_callback, port);
1332         if (event_add(&port->event, NULL) < 0) {
1333                 evdns_log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server.");
1334                 /* ???? Do more? */
1335         }
1336 }
1337
1338 /* set if we are waiting for the ability to write to this server. */
1339 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */
1340 /* we stop these events. */
1341 static void
1342 nameserver_write_waiting(struct nameserver *ns, char waiting) {
1343         if (ns->write_waiting == waiting) return;
1344
1345         ns->write_waiting = waiting;
1346         (void) event_del(&ns->event);
1347         CLEAR(&ns->event);
1348         event_set(&ns->event, ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST,
1349                           nameserver_ready_callback, ns);
1350         if (event_add(&ns->event, NULL) < 0) {
1351                 evdns_log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s",
1352                         debug_ntop((struct sockaddr *)&ns->address));
1353                 /* ???? Do more? */
1354         }
1355 }
1356
1357 /* a callback function. Called by libevent when the kernel says that */
1358 /* a nameserver socket is ready for writing or reading */
1359 static void
1360 nameserver_ready_callback(int fd, short events, void *arg) {
1361         struct nameserver *ns = (struct nameserver *) arg;
1362         (void)fd;
1363
1364         if (events & EV_WRITE) {
1365                 ns->choked = 0;
1366                 if (!evdns_transmit()) {
1367                         nameserver_write_waiting(ns, 0);
1368                 }
1369         }
1370         if (events & EV_READ) {
1371                 nameserver_read(ns);
1372         }
1373 }
1374
1375 /* a callback function. Called by libevent when the kernel says that */
1376 /* a server socket is ready for writing or reading. */
1377 static void
1378 server_port_ready_callback(int fd, short events, void *arg) {
1379         struct evdns_server_port *port = (struct evdns_server_port *) arg;
1380         (void) fd;
1381
1382         if (events & EV_WRITE) {
1383                 port->choked = 0;
1384                 server_port_flush(port);
1385         }
1386         if (events & EV_READ) {
1387                 server_port_read(port);
1388         }
1389 }
1390
1391 /* This is an inefficient representation; only use it via the dnslabel_table_*
1392  * functions, so that is can be safely replaced with something smarter later. */
1393 #define MAX_LABELS 128
1394 /* Structures used to implement name compression */
1395 struct dnslabel_entry { char *v; off_t pos; };
1396 struct dnslabel_table {
1397         int n_labels; /* number of current entries */
1398         /* map from name to position in message */
1399         struct dnslabel_entry labels[MAX_LABELS];
1400 };
1401
1402 /* Initialize dnslabel_table. */
1403 static void
1404 dnslabel_table_init(struct dnslabel_table *table)
1405 {
1406         table->n_labels = 0;
1407 }
1408
1409 /* Free all storage held by table, but not the table itself. */
1410 static void
1411 dnslabel_clear(struct dnslabel_table *table)
1412 {
1413         int i;
1414         for (i = 0; i < table->n_labels; ++i)
1415                 mm_free(table->labels[i].v);
1416         table->n_labels = 0;
1417 }
1418
1419 /* return the position of the label in the current message, or -1 if the label */
1420 /* hasn't been used yet. */
1421 static int
1422 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label)
1423 {
1424         int i;
1425         for (i = 0; i < table->n_labels; ++i) {
1426                 if (!strcmp(label, table->labels[i].v)) {
1427                         off_t pos = table->labels[i].pos;
1428             if (pos > 65535)
1429                 return -1;
1430             return (int)pos;
1431         }
1432         }
1433         return -1;
1434 }
1435
1436 /* remember that we've used the label at position pos */
1437 static int
1438 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos)
1439 {
1440         char *v;
1441         int p;
1442         if (table->n_labels == MAX_LABELS)
1443                 return (-1);
1444         v = mm_strdup(label);
1445         if (v == NULL)
1446                 return (-1);
1447         p = table->n_labels++;
1448         table->labels[p].v = v;
1449         table->labels[p].pos = pos;
1450
1451         return (0);
1452 }
1453
1454 /* Converts a string to a length-prefixed set of DNS labels, starting */
1455 /* at buf[j]. name and buf must not overlap. name_len should be the length */
1456 /* of name.      table is optional, and is used for compression. */
1457 /* */
1458 /* Input: abc.def */
1459 /* Output: <3>abc<3>def<0> */
1460 /* */
1461 /* Returns the first index after the encoded name, or negative on error. */
1462 /* -1    label was > 63 bytes */
1463 /* -2    name too long to fit in buffer. */
1464 /* */
1465 static off_t
1466 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
1467                                   const char *name, const size_t name_len,
1468                                   struct dnslabel_table *table) {
1469         const char *end = name + name_len;
1470         int ref = 0;
1471         u16 _t;
1472
1473 #define APPEND16(x) do {                                                   \
1474                 if (j + 2 > (off_t)buf_len)                                \
1475                         goto overflow;                                             \
1476                 _t = htons(x);                                                     \
1477                 memcpy(buf + j, &_t, 2);                                   \
1478                 j += 2;                                                                    \
1479         } while (0)
1480 #define APPEND32(x) do {                                                   \
1481                 if (j + 4 > (off_t)buf_len)                                \
1482                         goto overflow;                                             \
1483                 _t32 = htonl(x);                                                   \
1484                 memcpy(buf + j, &_t32, 4);                                 \
1485                 j += 4;                                                                    \
1486         } while (0)
1487
1488         if (name_len > 255) return -2;
1489
1490         for (;;) {
1491                 const char *const start = name;
1492                 if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) {
1493                         APPEND16(ref | 0xc000);
1494                         return j;
1495                 }
1496                 name = strchr(name, '.');
1497                 if (!name) {
1498                         const size_t label_len = end - start;
1499                         if (label_len > 63) return -1;
1500                         if ((size_t)(j+label_len+1) > buf_len) return -2;
1501                         if (table) dnslabel_table_add(table, start, j);
1502                         buf[j++] = (uint8_t)label_len;
1503
1504                         memcpy(buf + j, start, label_len);
1505                         j += end - start;
1506                         break;
1507                 } else {
1508                         /* append length of the label. */
1509                         const size_t label_len = name - start;
1510                         if (label_len > 63) return -1;
1511                         if ((size_t)(j+label_len+1) > buf_len) return -2;
1512                         if (table) dnslabel_table_add(table, start, j);
1513                         buf[j++] = (uint8_t)label_len;
1514
1515                         memcpy(buf + j, start, name - start);
1516                         j += name - start;
1517                         /* hop over the '.' */
1518                         name++;
1519                 }
1520         }
1521
1522         /* the labels must be terminated by a 0. */
1523         /* It's possible that the name ended in a . */
1524         /* in which case the zero is already there */
1525         if (!j || buf[j-1]) buf[j++] = 0;
1526         return j;
1527  overflow:
1528         return (-2);
1529 }
1530
1531 /* Finds the length of a dns request for a DNS name of the given */
1532 /* length. The actual request may be smaller than the value returned */
1533 /* here */
1534 static size_t
1535 evdns_request_len(const size_t name_len) {
1536         return 96 + /* length of the DNS standard header */
1537                 name_len + 2 +
1538                 4;      /* space for the resource type */
1539 }
1540
1541 /* build a dns request packet into buf. buf should be at least as long */
1542 /* as evdns_request_len told you it should be. */
1543 /* */
1544 /* Returns the amount of space used. Negative on error. */
1545 static int
1546 evdns_request_data_build(const char *const name, const size_t name_len,
1547                                                  const u16 trans_id, const u16 type, const u16 class,
1548                                                  u8 *const buf, size_t buf_len) {
1549         off_t j = 0;    /* current offset into buf */
1550         u16 _t;  /* used by the macros */
1551
1552         APPEND16(trans_id);
1553         APPEND16(0x0100);  /* standard query, recusion needed */
1554         APPEND16(1);  /* one question */
1555         APPEND16(0);  /* no answers */
1556         APPEND16(0);  /* no authority */
1557         APPEND16(0);  /* no additional */
1558
1559         j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL);
1560         if (j < 0) {
1561                 return (int)j;
1562         }
1563
1564         APPEND16(type);
1565         APPEND16(class);
1566
1567         return (int)j;
1568  overflow:
1569         return (-1);
1570 }
1571
1572 /* exported function */
1573 struct evdns_server_port *
1574 evdns_add_server_port(tor_socket_t socket, int is_tcp, evdns_request_callback_fn_type cb, void *user_data)
1575 {
1576         struct evdns_server_port *port;
1577         if (!(port = mm_malloc(sizeof(struct evdns_server_port))))
1578                 return NULL;
1579         memset(port, 0, sizeof(struct evdns_server_port));
1580
1581         assert(!is_tcp); /* TCP sockets not yet implemented */
1582         port->socket = socket;
1583         port->refcnt = 1;
1584         port->choked = 0;
1585         port->closing = 0;
1586         port->user_callback = cb;
1587         port->user_data = user_data;
1588         port->pending_replies = NULL;
1589
1590         event_set(&port->event, port->socket, EV_READ | EV_PERSIST,
1591                           server_port_ready_callback, port);
1592         if (event_add(&port->event, NULL)<0) {
1593                 mm_free(port);
1594                 return NULL;
1595         }
1596         return port;
1597 }
1598
1599 /* exported function */
1600 void
1601 evdns_close_server_port(struct evdns_server_port *port)
1602 {
1603         port->closing = 1;
1604         if (--port->refcnt == 0)
1605                 server_port_free(port);
1606 }
1607
1608 /* exported function */
1609 int
1610 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)
1611 {
1612         struct server_request *req = TO_SERVER_REQUEST(_req);
1613         struct server_reply_item **itemp, *item;
1614         int *countp;
1615
1616         if (req->response) /* have we already answered? */
1617                 return (-1);
1618
1619         switch (section) {
1620         case EVDNS_ANSWER_SECTION:
1621                 itemp = &req->answer;
1622                 countp = &req->n_answer;
1623                 break;
1624         case EVDNS_AUTHORITY_SECTION:
1625                 itemp = &req->authority;
1626                 countp = &req->n_authority;
1627                 break;
1628         case EVDNS_ADDITIONAL_SECTION:
1629                 itemp = &req->additional;
1630                 countp = &req->n_additional;
1631                 break;
1632         default:
1633                 return (-1);
1634         }
1635         while (*itemp) {
1636                 itemp = &((*itemp)->next);
1637         }
1638         item = mm_malloc(sizeof(struct server_reply_item));
1639         if (!item)
1640                 return -1;
1641         CLEAR(item);
1642         item->next = NULL;
1643         if (!(item->name = mm_strdup(name))) {
1644                 CLEAR(item);
1645                 mm_free(item);
1646                 return -1;
1647         }
1648         item->type = type;
1649         item->class = class;
1650         item->ttl = ttl;
1651         item->is_name = is_name != 0;
1652         item->datalen = 0;
1653         item->data = NULL;
1654         if (data) {
1655                 if (item->is_name) {
1656                         if (!(item->data = mm_strdup(data))) {
1657                                 mm_free(item->name);
1658                                 CLEAR(item);
1659                                 mm_free(item);
1660                                 return -1;
1661                         }
1662                         item->datalen = (u16)-1;
1663                 } else {
1664                         if (!(item->data = mm_malloc(datalen))) {
1665                                 mm_free(item->name);
1666                                 CLEAR(item);
1667                                 mm_free(item);
1668                                 return -1;
1669                         }
1670                         item->datalen = datalen;
1671                         memcpy(item->data, data, datalen);
1672                 }
1673         }
1674
1675         *itemp = item;
1676         ++(*countp);
1677         return 0;
1678 }
1679
1680 /* exported function */
1681 int
1682 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
1683 {
1684         return evdns_server_request_add_reply(
1685                   req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET,
1686                   ttl, n*4, 0, addrs);
1687 }
1688
1689 /* exported function */
1690 int
1691 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
1692 {
1693         return evdns_server_request_add_reply(
1694                   req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET,
1695                   ttl, n*16, 0, addrs);
1696 }
1697
1698 /* exported function */
1699 int
1700 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl)
1701 {
1702         u32 a;
1703         char buf[32];
1704         assert(in || inaddr_name);
1705         assert(!(in && inaddr_name));
1706         if (in) {
1707                 a = ntohl(in->s_addr);
1708                 snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
1709                                 (int)(u8)((a    )&0xff),
1710                                 (int)(u8)((a>>8 )&0xff),
1711                                 (int)(u8)((a>>16)&0xff),
1712                                 (int)(u8)((a>>24)&0xff));
1713                 inaddr_name = buf;
1714         }
1715         return evdns_server_request_add_reply(
1716                   req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET,
1717                   ttl, -1, 1, hostname);
1718 }
1719
1720 /* exported function */
1721 int
1722 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl)
1723 {
1724         return evdns_server_request_add_reply(
1725                   req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET,
1726                   ttl, -1, 1, cname);
1727 }
1728
1729
1730 static int
1731 evdns_server_request_format_response(struct server_request *req, int err)
1732 {
1733         unsigned char buf[1500];
1734         size_t buf_len = sizeof(buf);
1735         off_t j = 0, r;
1736         u16 _t;
1737         u32 _t32;
1738         int i;
1739         u16 flags;
1740         struct dnslabel_table table;
1741
1742         if (err < 0 || err > 15) return -1;
1743
1744         /* Set response bit and error code; copy OPCODE and RD fields from
1745          * question; copy RA and AA if set by caller. */
1746         flags = req->base.flags;
1747         flags |= (0x8000 | err);
1748
1749         dnslabel_table_init(&table);
1750         APPEND16(req->trans_id);
1751         APPEND16(flags);
1752         APPEND16(req->base.nquestions);
1753         APPEND16(req->n_answer);
1754         APPEND16(req->n_authority);
1755         APPEND16(req->n_additional);
1756
1757         /* Add questions. */
1758         for (i=0; i < req->base.nquestions; ++i) {
1759                 const char *s = req->base.questions[i]->name;
1760                 j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table);
1761                 if (j < 0) {
1762                         dnslabel_clear(&table);
1763                         return (int) j;
1764                 }
1765                 APPEND16(req->base.questions[i]->type);
1766                 APPEND16(req->base.questions[i]->dns_question_class);
1767         }
1768
1769         /* Add answer, authority, and additional sections. */
1770         for (i=0; i<3; ++i) {
1771                 struct server_reply_item *item;
1772                 if (i==0)
1773                         item = req->answer;
1774                 else if (i==1)
1775                         item = req->authority;
1776                 else
1777                         item = req->additional;
1778                 while (item) {
1779                         r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
1780                         if (r < 0)
1781                                 goto overflow;
1782                         j = r;
1783
1784                         APPEND16(item->type);
1785                         APPEND16(item->class);
1786                         APPEND32(item->ttl);
1787                         if (item->is_name) {
1788                                 off_t len_idx = j, name_start;
1789                                 j += 2;
1790                                 name_start = j;
1791                                 r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
1792                                 if (r < 0)
1793                                         goto overflow;
1794                                 j = r;
1795                                 _t = htons( (j-name_start) );
1796                                 memcpy(buf+len_idx, &_t, 2);
1797                         } else {
1798                                 APPEND16(item->datalen);
1799                                 if (j+item->datalen > (off_t)buf_len)
1800                                         goto overflow;
1801                                 memcpy(buf+j, item->data, item->datalen);
1802                                 j += item->datalen;
1803                         }
1804                         item = item->next;
1805                 }
1806         }
1807
1808         if (j > 512) {
1809 overflow:
1810                 j = 512;
1811                 buf[2] |= 0x02; /* set the truncated bit. */
1812         }
1813
1814         req->response_len = (size_t)j;
1815
1816         if (!(req->response = mm_malloc(req->response_len))) {
1817                 server_request_free_answers(req);
1818                 dnslabel_clear(&table);
1819                 return (-1);
1820         }
1821         memcpy(req->response, buf, req->response_len);
1822         server_request_free_answers(req);
1823         dnslabel_clear(&table);
1824         return (0);
1825 }
1826
1827 /* exported function */
1828 int
1829 evdns_server_request_respond(struct evdns_server_request *_req, int err)
1830 {
1831         struct server_request *req = TO_SERVER_REQUEST(_req);
1832         struct evdns_server_port *port = req->port;
1833         ssize_t r;
1834         if (!req->response) {
1835                 if ((r = evdns_server_request_format_response(req, err))<0)
1836                         return (int)r;
1837         }
1838
1839         r = sendto(port->socket, req->response, req->response_len, 0,
1840                            (struct sockaddr*) &req->addr, req->addrlen);
1841         if (r<0) {
1842                 int error = last_error(port->socket);
1843                 if (! error_is_eagain(error))
1844                         return -1;
1845
1846                 if (port->pending_replies) {
1847                         req->prev_pending = port->pending_replies->prev_pending;
1848                         req->next_pending = port->pending_replies;
1849                         req->prev_pending->next_pending =
1850                                 req->next_pending->prev_pending = req;
1851                 } else {
1852                         req->prev_pending = req->next_pending = req;
1853                         port->pending_replies = req;
1854                         port->choked = 1;
1855
1856                         (void) event_del(&port->event);
1857                         CLEAR(&port->event);
1858                         event_set(&port->event, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port);
1859
1860                         if (event_add(&port->event, NULL) < 0) {
1861                                 evdns_log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server");
1862                         }
1863
1864                 }
1865
1866                 return 1;
1867         }
1868         if (server_request_free(req))
1869                 return 0;
1870
1871         if (port->pending_replies)
1872                 server_port_flush(port);
1873
1874         return 0;
1875 }
1876
1877 /* Free all storage held by RRs in req. */
1878 static void
1879 server_request_free_answers(struct server_request *req)
1880 {
1881         struct server_reply_item *victim, *next, **list;
1882         int i;
1883         for (i = 0; i < 3; ++i) {
1884                 if (i==0)
1885                         list = &req->answer;
1886                 else if (i==1)
1887                         list = &req->authority;
1888                 else
1889                         list = &req->additional;
1890
1891                 victim = *list;
1892                 while (victim) {
1893                         next = victim->next;
1894                         mm_free(victim->name);
1895                         if (victim->data)
1896                                 mm_free(victim->data);
1897                         mm_free(victim);
1898                         victim = next;
1899                 }
1900                 *list = NULL;
1901         }
1902 }
1903
1904 /* Free all storage held by req, and remove links to it. */
1905 /* return true iff we just wound up freeing the server_port. */
1906 static int
1907 server_request_free(struct server_request *req)
1908 {
1909         int i, rc=1;
1910         if (req->base.questions) {
1911                 for (i = 0; i < req->base.nquestions; ++i)
1912                         mm_free(req->base.questions[i]);
1913                 mm_free(req->base.questions);
1914         }
1915
1916         if (req->port) {
1917                 if (req->port->pending_replies == req) {
1918                         if (req->next_pending && req->next_pending != req)
1919                                 req->port->pending_replies = req->next_pending;
1920                         else
1921                                 req->port->pending_replies = NULL;
1922                 }
1923                 rc = --req->port->refcnt;
1924         }
1925
1926         if (req->response) {
1927                 mm_free(req->response);
1928         }
1929
1930         server_request_free_answers(req);
1931
1932         if (req->next_pending && req->next_pending != req) {
1933                 req->next_pending->prev_pending = req->prev_pending;
1934                 req->prev_pending->next_pending = req->next_pending;
1935         }
1936
1937         if (rc == 0) {
1938                 server_port_free(req->port);
1939                 CLEAR(req);
1940                 mm_free(req);
1941                 return (1);
1942         }
1943         CLEAR(req);
1944         mm_free(req);
1945         return (0);
1946 }
1947
1948 /* Free all storage held by an evdns_server_port.  Only called when the
1949  * reference count is down to 0. */
1950 static void
1951 server_port_free(struct evdns_server_port *port)
1952 {
1953         assert(port);
1954         assert(!port->refcnt);
1955         assert(!port->pending_replies);
1956         if (port->socket > 0) {
1957                 CLOSE_SOCKET(port->socket);
1958                 port->socket = -1;
1959         }
1960         (void) event_del(&port->event);
1961         CLEAR(&port->event);
1962         CLEAR(port);
1963         mm_free(port);
1964 }
1965
1966 /* exported function */
1967 int
1968 evdns_server_request_drop(struct evdns_server_request *_req)
1969 {
1970         struct server_request *req = TO_SERVER_REQUEST(_req);
1971         server_request_free(req);
1972         return 0;
1973 }
1974
1975 /* exported function */
1976 int
1977 evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len)
1978 {
1979         struct server_request *req = TO_SERVER_REQUEST(_req);
1980         if (addr_len < (int)req->addrlen)
1981                 return -1;
1982         memcpy(sa, &(req->addr), req->addrlen);
1983         return req->addrlen;
1984 }
1985
1986 #undef APPEND16
1987 #undef APPEND32
1988
1989 /* this is a libevent callback function which is called when a request */
1990 /* has timed out. */
1991 static void
1992 evdns_request_timeout_callback(int fd, short events, void *arg) {
1993         struct evdns_request *const req = (struct evdns_request *) arg;
1994         (void) fd;
1995         (void) events;
1996
1997         evdns_log(EVDNS_LOG_DEBUG, "Request %lx timed out", (unsigned long) arg);
1998
1999         req->ns->timedout++;
2000         if (req->ns->timedout > global_max_nameserver_timeout) {
2001                 req->ns->timedout = 0;
2002                 nameserver_failed(req->ns, "request timed out.");
2003         }
2004
2005         if (req->tx_count >= global_max_retransmits) {
2006                 /* this request has failed */
2007                 reply_callback(req, 0, DNS_ERR_TIMEOUT, NULL);
2008                 request_finished(req, &req_head);
2009         } else {
2010                 /* retransmit it */
2011                 /* Stop waiting for the timeout.  No need to do this in
2012                  * request_finished; that one already deletes the timeout event.
2013                  * XXXX023 port this change to libevent. */
2014                 del_timeout_event(req);
2015                 evdns_request_transmit(req);
2016         }
2017 }
2018
2019 /* try to send a request to a given server. */
2020 /* */
2021 /* return: */
2022 /* 0 ok */
2023 /* 1 temporary failure */
2024 /* 2 other failure */
2025 static int
2026 evdns_request_transmit_to(struct evdns_request *req, struct nameserver *server) {
2027         const ssize_t r = send(server->socket, (void*)req->request,
2028                          req->request_len, 0);
2029         if (r < 0) {
2030                 int err = last_error(server->socket);
2031                 if (error_is_eagain(err)) return 1;
2032                 nameserver_failed(req->ns, tor_socket_strerror(err));
2033                 return 2;
2034         } else if (r != (ssize_t)req->request_len) {
2035                 return 1;  /* short write */
2036         } else {
2037                 return 0;
2038         }
2039 }
2040
2041 /* try to send a request, updating the fields of the request */
2042 /* as needed */
2043 /* */
2044 /* return: */
2045 /* 0 ok */
2046 /* 1 failed */
2047 static int
2048 evdns_request_transmit(struct evdns_request *req) {
2049         int retcode = 0, r;
2050
2051         /* if we fail to send this packet then this flag marks it */
2052         /* for evdns_transmit */
2053         req->transmit_me = 1;
2054         if (req->trans_id == 0xffff) abort();
2055
2056         if (req->ns->choked) {
2057                 /* don't bother trying to write to a socket */
2058                 /* which we have had EAGAIN from */
2059                 return 1;
2060         }
2061
2062         r = evdns_request_transmit_to(req, req->ns);
2063         switch (r) {
2064         case 1:
2065                 /* temp failure */
2066                 req->ns->choked = 1;
2067                 nameserver_write_waiting(req->ns, 1);
2068                 return 1;
2069         case 2:
2070                 /* failed to transmit the request entirely. */
2071                 retcode = 1;
2072                 /* fall through: we'll set a timeout, which will time out,
2073                  * and make us retransmit the request anyway. */
2074         default:
2075                 /* transmitted; we need to check for timeout. */
2076                 evdns_log(EVDNS_LOG_DEBUG,
2077                         "Setting timeout for request %lx", (unsigned long) req);
2078
2079                 if (add_timeout_event(req, &global_timeout) < 0) {
2080                         evdns_log(EVDNS_LOG_WARN,
2081                                 "Error from libevent when adding timer for request %lx",
2082                                 (unsigned long) req);
2083                         /* ???? Do more? */
2084                 }
2085                 req->tx_count++;
2086                 req->transmit_me = 0;
2087                 return retcode;
2088         }
2089 }
2090
2091 static void
2092 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) {
2093         struct sockaddr *addr = arg;
2094         struct nameserver *server;
2095         (void) type;
2096         (void) count;
2097         (void) ttl;
2098         (void) addresses;
2099
2100         for (server = server_head; server; server = server->next) {
2101                 if (sockaddr_eq(addr, (struct sockaddr*) &server->address, 1)) {
2102                         if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) {
2103                                 /* this is a good reply */
2104                                 nameserver_up(server);
2105                         } else {
2106                                 nameserver_probe_failed(server);
2107                         }
2108                 }
2109                 if (server->next == server_head)
2110                         break;
2111         }
2112
2113         mm_free(addr);
2114 }
2115
2116 static void
2117 nameserver_send_probe(struct nameserver *const ns) {
2118         struct evdns_request *req;
2119         struct sockaddr_storage *addr;
2120         /* here we need to send a probe to a given nameserver */
2121         /* in the hope that it is up now. */
2122
2123         /* We identify the nameserver by its address, in case it is removed before
2124          * our probe comes back. */
2125         addr = mm_malloc(sizeof(struct sockaddr_storage));
2126         memcpy(addr, &ns->address, sizeof(struct sockaddr_storage));
2127
2128         evdns_log(EVDNS_LOG_DEBUG, "Sending probe to %s", debug_ntop((struct sockaddr *)&ns->address));
2129
2130         req = request_new(TYPE_A, "www.google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, addr);
2131         if (!req) {
2132                 mm_free(addr);
2133                 return;
2134         }
2135         /* we force this into the inflight queue no matter what */
2136         request_trans_id_set(req, transaction_id_pick());
2137         req->ns = ns;
2138         request_submit(req);
2139 }
2140
2141 /* returns: */
2142 /* 0 didn't try to transmit anything */
2143 /* 1 tried to transmit something */
2144 static int
2145 evdns_transmit(void) {
2146         char did_try_to_transmit = 0;
2147
2148         if (req_head) {
2149                 struct evdns_request *const started_at = req_head, *req = req_head;
2150                 /* first transmit all the requests which are currently waiting */
2151                 do {
2152                         if (req->transmit_me) {
2153                                 did_try_to_transmit = 1;
2154                                 evdns_request_transmit(req);
2155                         }
2156
2157                         req = req->next;
2158                 } while (req != started_at);
2159         }
2160
2161         return did_try_to_transmit;
2162 }
2163
2164 /* exported function */
2165 int
2166 evdns_count_nameservers(void)
2167 {
2168         const struct nameserver *server = server_head;
2169         int n = 0;
2170         if (!server)
2171                 return 0;
2172         do {
2173                 ++n;
2174                 server = server->next;
2175         } while (server != server_head);
2176         return n;
2177 }
2178
2179 /* exported function */
2180 int
2181 evdns_clear_nameservers_and_suspend(void)
2182 {
2183         struct nameserver *server = server_head, *started_at = server_head;
2184         struct evdns_request *req = req_head, *req_started_at = req_head;
2185
2186         if (!server)
2187                 return 0;
2188         while (1) {
2189                 struct nameserver *next = server->next;
2190                 (void) event_del(&server->event);
2191                 CLEAR(&server->event);
2192                 del_timeout_event(server);
2193                 if (server->socket >= 0)
2194                         CLOSE_SOCKET(server->socket);
2195                 CLEAR(server);
2196                 mm_free(server);
2197                 if (next == started_at)
2198                         break;
2199                 server = next;
2200         }
2201         server_head = NULL;
2202         global_good_nameservers = 0;
2203
2204         while (req) {
2205                 struct evdns_request *next = req->next;
2206                 req->tx_count = req->reissue_count = 0;
2207                 req->ns = NULL;
2208                 /* ???? What to do about searches? */
2209                 del_timeout_event(req);
2210                 req->trans_id = 0;
2211                 req->transmit_me = 0;
2212
2213                 global_requests_waiting++;
2214                 evdns_request_insert(req, &req_waiting_head);
2215                 /* We want to insert these suspended elements at the front of
2216                  * the waiting queue, since they were pending before any of
2217                  * the waiting entries were added.      This is a circular list,
2218                  * so we can just shift the start back by one.*/
2219                 req_waiting_head = req_waiting_head->prev;
2220
2221                 if (next == req_started_at)
2222                         break;
2223                 req = next;
2224         }
2225         req_head = NULL;
2226         global_requests_inflight = 0;
2227
2228         return 0;
2229 }
2230
2231 static struct sockaddr_storage global_bind_address;
2232 static socklen_t global_bind_addrlen = 0;
2233 static int global_bind_addr_is_set = 0;
2234 void
2235 evdns_set_default_outgoing_bind_address(const struct sockaddr *addr,
2236                                                                                 socklen_t addrlen)
2237 {
2238         memset(&global_bind_address, 0, sizeof(global_bind_address));
2239         if (addr) {
2240                 assert(addrlen <= (socklen_t)sizeof(global_bind_address));
2241                 memcpy(&global_bind_address, addr, addrlen);
2242                 global_bind_addrlen = addrlen;
2243                 global_bind_addr_is_set = 1;
2244         } else {
2245                 global_bind_addr_is_set = 0;
2246         }
2247 }
2248
2249 /* exported function */
2250 int
2251 evdns_resume(void)
2252 {
2253         evdns_requests_pump_waiting_queue();
2254         return 0;
2255 }
2256
2257 static int
2258 sockaddr_is_loopback(const struct sockaddr *addr)
2259 {
2260         static const char LOOPBACK_S6[16] =
2261             "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1";
2262         if (addr->sa_family == AF_INET) {
2263                 struct sockaddr_in *sin = (struct sockaddr_in *)addr;
2264                 return (ntohl(sin->sin_addr.s_addr) & 0xff000000) == 0x7f000000;
2265         } else if (addr->sa_family == AF_INET6) {
2266                 struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)addr;
2267                 return fast_memeq(sin6->sin6_addr.s6_addr, LOOPBACK_S6, 16);
2268         }
2269         return 0;
2270 }
2271
2272 static int
2273 _evdns_nameserver_add_impl(const struct sockaddr *address,
2274                                                    socklen_t addrlen) {
2275         /* first check to see if we already have this nameserver */
2276
2277         const struct nameserver *server = server_head, *const started_at = server_head;
2278         struct nameserver *ns;
2279
2280         int err = 0;
2281         if (server) {
2282                 do {
2283                         if (sockaddr_eq(address, (struct sockaddr *)&server->address, 1)) {
2284                                 evdns_log(EVDNS_LOG_DEBUG, "Duplicate nameserver.");
2285                                 return 3;
2286                         }
2287                         server = server->next;
2288                 } while (server != started_at);
2289         }
2290         if (addrlen > (int)sizeof(ns->address)) {
2291                 evdns_log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen);
2292                 return 2;
2293         }
2294
2295         ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver));
2296         if (!ns) return -1;
2297
2298         memset(ns, 0, sizeof(struct nameserver));
2299
2300         evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
2301
2302 #if 1
2303         ns->socket = tor_open_socket_nonblocking(address->sa_family, SOCK_DGRAM, 0);
2304         if (!SOCKET_OK(ns->socket)) { err = 1; goto out1; }
2305 #else
2306         ns->socket = tor_open_socket(address->sa_family, SOCK_DGRAM, 0);
2307         if (ns->socket < 0) { err = 1; goto out1; }
2308 #ifdef _WIN32
2309         {
2310                 u_long nonblocking = 1;
2311                 ioctlsocket(ns->socket, FIONBIO, &nonblocking);
2312         }
2313 #else
2314         if (fcntl(ns->socket, F_SETFL, O_NONBLOCK) == -1) {
2315                 evdns_log(EVDNS_LOG_WARN, "Error %s (%d) while settings file status flags.",
2316                                   tor_socket_strerror(errno), errno);
2317                 err = 2;
2318                 goto out2;
2319         }
2320 #endif
2321
2322 #endif /* 1 */
2323         if (global_bind_addr_is_set &&
2324             !sockaddr_is_loopback((struct sockaddr*)&global_bind_address)) {
2325                 if (bind(ns->socket, (struct sockaddr *)&global_bind_address,
2326                                  global_bind_addrlen) < 0) {
2327                         evdns_log(EVDNS_LOG_DEBUG, "Couldn't bind to outgoing address.");
2328                         err = 2;
2329                         goto out2;
2330                 }
2331         }
2332
2333         if (connect(ns->socket, address, addrlen) != 0) {
2334                 evdns_log(EVDNS_LOG_DEBUG, "Couldn't open socket to nameserver.");
2335                 err = 2;
2336                 goto out2;
2337         }
2338
2339         memcpy(&ns->address, address, addrlen);
2340         ns->state = 1;
2341         event_set(&ns->event, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns);
2342         if (event_add(&ns->event, NULL) < 0) {
2343                 evdns_log(EVDNS_LOG_DEBUG, "Couldn't add event for nameserver.");
2344                 err = 2;
2345                 goto out2;
2346         }
2347
2348         evdns_log(EVDNS_LOG_DEBUG, "Added nameserver %s", debug_ntop(address));
2349
2350         /* insert this nameserver into the list of them */
2351         if (!server_head) {
2352                 ns->next = ns->prev = ns;
2353                 server_head = ns;
2354         } else {
2355                 ns->next = server_head->next;
2356                 ns->prev = server_head;
2357                 server_head->next = ns;
2358                 if (server_head->prev == server_head) {
2359                         server_head->prev = ns;
2360                 }
2361         }
2362
2363         global_good_nameservers++;
2364
2365         return 0;
2366
2367 out2:
2368         CLOSE_SOCKET(ns->socket);
2369 out1:
2370         CLEAR(ns);
2371         mm_free(ns);
2372         evdns_log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", debug_ntop(address), err);
2373         return err;
2374 }
2375
2376 /* exported function */
2377 int
2378 evdns_nameserver_add(uint32_t address) {
2379         struct sockaddr_in sin;
2380         memset(&sin, 0, sizeof(sin));
2381         sin.sin_family = AF_INET;
2382 #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
2383         sin.sin_len = sizeof(sin);
2384 #endif
2385         sin.sin_addr.s_addr = htonl(address);
2386         sin.sin_port = 53;
2387         return _evdns_nameserver_add_impl((struct sockaddr*) &sin, sizeof(sin));
2388 }
2389
2390 /* exported function */
2391 int
2392 evdns_nameserver_ip_add(const char *ip_as_string) {
2393         int port;
2394         char buf[128];
2395         const char *cp, *addr_part, *port_part;
2396         int is_ipv6;
2397         /* recognized formats are:
2398          * [ipv6]:port
2399          * ipv6
2400          * [ipv6]
2401          * ipv4:port
2402          * ipv4
2403          */
2404
2405         evdns_log(EVDNS_LOG_DEBUG, "Trying to add nameserver <%s>", ip_as_string);
2406
2407         cp = strchr(ip_as_string, ':');
2408         if (*ip_as_string == '[') {
2409                 size_t len;
2410                 if (!(cp = strchr(ip_as_string, ']'))) {
2411                         evdns_log(EVDNS_LOG_DEBUG, "Nameserver missing closing ]");
2412                         return 4;
2413                 }
2414                 len = cp-(ip_as_string + 1);
2415                 if (len > sizeof(buf)-1) {
2416                         evdns_log(EVDNS_LOG_DEBUG, "[Nameserver] does not fit in buffer.");
2417                         return 4;
2418                 }
2419                 memcpy(buf, ip_as_string+1, len);
2420                 buf[len] = '\0';
2421                 addr_part = buf;
2422                 if (cp[1] == ':')
2423                         port_part = cp+2;
2424                 else
2425                         port_part = NULL;
2426                 is_ipv6 = 1;
2427         } else if (cp && strchr(cp+1, ':')) {
2428                 is_ipv6 = 1;
2429                 addr_part = ip_as_string;
2430                 port_part = NULL;
2431         } else if (cp) {
2432                 is_ipv6 = 0;
2433                 if (cp - ip_as_string > (int)sizeof(buf)-1) {
2434                         evdns_log(EVDNS_LOG_DEBUG, "Nameserver does not fit in buffer.");
2435                         return 4;
2436                 }
2437                 memcpy(buf, ip_as_string, cp-ip_as_string);
2438                 buf[cp-ip_as_string] = '\0';
2439                 addr_part = buf;
2440                 port_part = cp+1;
2441         } else {
2442                 addr_part = ip_as_string;
2443                 port_part = NULL;
2444                 is_ipv6 = 0;
2445         }
2446
2447         if (port_part == NULL) {
2448                 port = 53;
2449         } else {
2450                 port = strtoint(port_part);
2451                 if (port <= 0 || port > 65535) {
2452                         evdns_log(EVDNS_LOG_DEBUG, "Nameserver port <%s> out of range",
2453                                 port_part);
2454                         return 4;
2455                 }
2456         }
2457
2458         /* Tor-only.  needs a more general fix. */
2459         assert(addr_part);
2460         if (is_ipv6) {
2461                 struct sockaddr_in6 sin6;
2462                 memset(&sin6, 0, sizeof(sin6));
2463 #ifdef HAVE_STRUCT_SOCKADDR_IN6_SIN6_LEN
2464                 sin6.sin6_len = sizeof(sin6);
2465 #endif
2466                 sin6.sin6_family = AF_INET6;
2467                 sin6.sin6_port = htons(port);
2468                 if (1 != tor_inet_pton(AF_INET6, addr_part, &sin6.sin6_addr)) {
2469                         evdns_log(EVDNS_LOG_DEBUG, "inet_pton(%s) failed", addr_part);
2470                         return 4;
2471                 }
2472                 return _evdns_nameserver_add_impl((struct sockaddr*)&sin6,
2473                                                                                   sizeof(sin6));
2474         } else {
2475                 struct sockaddr_in sin;
2476                 memset(&sin, 0, sizeof(sin));
2477 #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
2478                 sin.sin_len = sizeof(sin);
2479 #endif
2480                 sin.sin_family = AF_INET;
2481                 sin.sin_port = htons(port);
2482                 if (!inet_aton(addr_part, &sin.sin_addr)) {
2483                         evdns_log(EVDNS_LOG_DEBUG, "inet_pton(%s) failed", addr_part);
2484                         return 4;
2485                 }
2486                 return _evdns_nameserver_add_impl((struct sockaddr*)&sin,
2487                                                                                   sizeof(sin));
2488         }
2489 }
2490
2491 int
2492 evdns_nameserver_sockaddr_add(const struct sockaddr *sa, socklen_t len)
2493 {
2494         return _evdns_nameserver_add_impl(sa, len);
2495 }
2496
2497 /* insert into the tail of the queue */
2498 static void
2499 evdns_request_insert(struct evdns_request *req, struct evdns_request **head) {
2500         if (!*head) {
2501                 *head = req;
2502                 req->next = req->prev = req;
2503                 return;
2504         }
2505
2506         req->prev = (*head)->prev;
2507         req->prev->next = req;
2508         req->next = *head;
2509         (*head)->prev = req;
2510 }
2511
2512 static int
2513 string_num_dots(const char *s) {
2514         int count = 0;
2515         while ((s = strchr(s, '.'))) {
2516                 s++;
2517                 count++;
2518         }
2519         return count;
2520 }
2521
2522 static struct evdns_request *
2523 request_new(int type, const char *name, int flags,
2524         evdns_callback_type callback, void *user_ptr) {
2525         const char issuing_now =
2526                 (global_requests_inflight < global_max_requests_inflight) ? 1 : 0;
2527
2528         const size_t name_len = strlen(name);
2529         const size_t request_max_len = evdns_request_len(name_len);
2530         const u16 trans_id = issuing_now ? transaction_id_pick() : 0xffff;
2531         /* the request data is alloced in a single block with the header */
2532         struct evdns_request *const req =
2533                 (struct evdns_request *) mm_malloc(sizeof(struct evdns_request) + request_max_len);
2534         char namebuf[256];
2535         int rlen;
2536         (void) flags;
2537
2538         if (!req) return NULL;
2539
2540         if (name_len >= sizeof(namebuf)) {
2541                 _mm_free(req);
2542                 return NULL;
2543         }
2544
2545         memset(req, 0, sizeof(struct evdns_request));
2546
2547         evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req);
2548
2549         if (global_randomize_case) {
2550                 unsigned i;
2551                 char randbits[32];
2552                 strlcpy(namebuf, name, sizeof(namebuf));
2553                 rand_bytes_function(randbits, (name_len+7)/8);
2554                 for (i = 0; i < name_len; ++i) {
2555                         if (ISALPHA(namebuf[i])) {
2556                                 if ((randbits[i >> 3] & (1<<(i%7))))
2557                                         namebuf[i] = TOLOWER(namebuf[i]);
2558                                 else
2559                                         namebuf[i] = TOUPPER(namebuf[i]);
2560                         }
2561                 }
2562                 name = namebuf;
2563         }
2564
2565         /* request data lives just after the header */
2566         req->request = ((u8 *) req) + sizeof(struct evdns_request);
2567         /* denotes that the request data shouldn't be mm_free()ed */
2568         req->request_appended = 1;
2569         rlen = evdns_request_data_build(name, name_len, trans_id,
2570                                                         type, CLASS_INET, req->request, request_max_len);
2571         if (rlen < 0)
2572                 goto err1;
2573         req->request_len = rlen;
2574         req->trans_id = trans_id;
2575         req->tx_count = 0;
2576         req->request_type = type;
2577         req->user_pointer = user_ptr;
2578         req->user_callback = callback;
2579         req->ns = issuing_now ? nameserver_pick() : NULL;
2580         req->next = req->prev = NULL;
2581
2582         return req;
2583 err1:
2584         CLEAR(req);
2585         _mm_free(req);
2586         return NULL;
2587 }
2588
2589 static void
2590 request_submit(struct evdns_request *const req) {
2591         if (req->ns) {
2592                 /* if it has a nameserver assigned then this is going */
2593                 /* straight into the inflight queue */
2594                 evdns_request_insert(req, &req_head);
2595                 global_requests_inflight++;
2596                 evdns_request_transmit(req);
2597         } else {
2598                 evdns_request_insert(req, &req_waiting_head);
2599                 global_requests_waiting++;
2600         }
2601 }
2602
2603 /* exported function */
2604 int evdns_resolve_ipv4(const char *name, int flags,
2605                                            evdns_callback_type callback, void *ptr) {
2606         evdns_log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
2607         if (flags & DNS_QUERY_NO_SEARCH) {
2608                 struct evdns_request *const req =
2609                         request_new(TYPE_A, name, flags, callback, ptr);
2610                 if (req == NULL)
2611                         return (1);
2612                 request_submit(req);
2613                 return (0);
2614         } else {
2615                 return (search_request_new(TYPE_A, name, flags, callback, ptr));
2616         }
2617 }
2618
2619 /* exported function */
2620 int evdns_resolve_ipv6(const char *name, int flags,
2621                                            evdns_callback_type callback, void *ptr) {
2622         evdns_log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
2623         if (flags & DNS_QUERY_NO_SEARCH) {
2624                 struct evdns_request *const req =
2625                         request_new(TYPE_AAAA, name, flags, callback, ptr);
2626                 if (req == NULL)
2627                         return (1);
2628                 request_submit(req);
2629                 return (0);
2630         } else {
2631                 return (search_request_new(TYPE_AAAA, name, flags, callback, ptr));
2632         }
2633 }
2634
2635 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
2636         char buf[32];
2637         struct evdns_request *req;
2638         u32 a;
2639         assert(in);
2640         a = ntohl(in->s_addr);
2641         snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
2642                         (int)(u8)((a    )&0xff),
2643                         (int)(u8)((a>>8 )&0xff),
2644                         (int)(u8)((a>>16)&0xff),
2645                         (int)(u8)((a>>24)&0xff));
2646         evdns_log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
2647         req = request_new(TYPE_PTR, buf, flags, callback, ptr);
2648         if (!req) return 1;
2649         request_submit(req);
2650         return 0;
2651 }
2652
2653 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
2654         /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */
2655         char buf[73];
2656         char *cp;
2657         struct evdns_request *req;
2658         int i;
2659         assert(in);
2660         cp = buf;
2661         for (i=15; i >= 0; --i) {
2662                 u8 byte = in->s6_addr[i];
2663                 *cp++ = "0123456789abcdef"[byte & 0x0f];
2664                 *cp++ = '.';
2665                 *cp++ = "0123456789abcdef"[byte >> 4];
2666                 *cp++ = '.';
2667         }
2668         assert(cp + strlen("ip6.arpa") < buf+sizeof(buf));
2669         memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1);
2670         evdns_log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
2671         req = request_new(TYPE_PTR, buf, flags, callback, ptr);
2672         if (!req) return 1;
2673         request_submit(req);
2674         return 0;
2675 }
2676
2677 /*/////////////////////////////////////////////////////////////////// */
2678 /* Search support */
2679 /* */
2680 /* the libc resolver has support for searching a number of domains */
2681 /* to find a name. If nothing else then it takes the single domain */
2682 /* from the gethostname() call. */
2683 /* */
2684 /* It can also be configured via the domain and search options in a */
2685 /* resolv.conf. */
2686 /* */
2687 /* The ndots option controls how many dots it takes for the resolver */
2688 /* to decide that a name is non-local and so try a raw lookup first. */
2689
2690 struct search_domain {
2691         size_t len;
2692         struct search_domain *next;
2693         /* the text string is appended to this structure */
2694 };
2695
2696 struct search_state {
2697         int refcount;
2698         int ndots;
2699         int num_domains;
2700         struct search_domain *head;
2701 };
2702
2703 static struct search_state *global_search_state = NULL;
2704
2705 static void
2706 search_state_decref(struct search_state *const state) {
2707         if (!state) return;
2708         state->refcount--;
2709         if (!state->refcount) {
2710                 struct search_domain *next, *dom;
2711                 for (dom = state->head; dom; dom = next) {
2712                         next = dom->next;
2713                         CLEAR(dom);
2714                         _mm_free(dom);
2715                 }
2716                 CLEAR(state);
2717                 _mm_free(state);
2718         }
2719 }
2720
2721 static struct search_state *
2722 search_state_new(void) {
2723         struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state));
2724         if (!state) return NULL;
2725         memset(state, 0, sizeof(struct search_state));
2726         state->refcount = 1;
2727         state->ndots = 1;
2728
2729         return state;
2730 }
2731
2732 static void
2733 search_postfix_clear(void) {
2734         search_state_decref(global_search_state);
2735
2736         global_search_state = search_state_new();
2737 }
2738
2739 /* exported function */
2740 void
2741 evdns_search_clear(void) {
2742         search_postfix_clear();
2743 }
2744
2745 static void
2746 search_postfix_add(const char *domain) {
2747         size_t domain_len;
2748         struct search_domain *sdomain;
2749         while (domain[0] == '.') domain++;
2750         domain_len = strlen(domain);
2751
2752         if (!global_search_state) global_search_state = search_state_new();
2753                 if (!global_search_state) return;
2754         global_search_state->num_domains++;
2755
2756         sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len);
2757                 if (!sdomain) return;
2758         memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len);
2759         sdomain->next = global_search_state->head;
2760         sdomain->len = domain_len;
2761
2762         global_search_state->head = sdomain;
2763 }
2764
2765 /* reverse the order of members in the postfix list. This is needed because, */
2766 /* when parsing resolv.conf we push elements in the wrong order */
2767 static void
2768 search_reverse(void) {
2769         struct search_domain *cur, *prev = NULL, *next;
2770         cur = global_search_state->head;
2771         while (cur) {
2772                 next = cur->next;
2773                 cur->next = prev;
2774                 prev = cur;
2775                 cur = next;
2776         }
2777
2778         global_search_state->head = prev;
2779 }
2780
2781 /* exported function */
2782 void
2783 evdns_search_add(const char *domain) {
2784         search_postfix_add(domain);
2785 }
2786
2787 /* exported function */
2788 void
2789 evdns_search_ndots_set(const int ndots) {
2790         if (!global_search_state) global_search_state = search_state_new();
2791                 if (!global_search_state) return;
2792         global_search_state->ndots = ndots;
2793 }
2794
2795 static void
2796 search_set_from_hostname(void) {
2797         char hostname[HOST_NAME_MAX + 1], *domainname;
2798
2799         search_postfix_clear();
2800         if (gethostname(hostname, sizeof(hostname))) return;
2801         domainname = strchr(hostname, '.');
2802         if (!domainname) return;
2803         search_postfix_add(domainname);
2804 }
2805
2806 /* warning: returns malloced string */
2807 static char *
2808 search_make_new(const struct search_state *const state, int n, const char *const base_name) {
2809         const size_t base_len = strlen(base_name);
2810         const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1;
2811         struct search_domain *dom;
2812
2813         for (dom = state->head; dom; dom = dom->next) {
2814                 if (!n--) {
2815                         /* this is the postfix we want */
2816                         /* the actual postfix string is kept at the end of the structure */
2817                         const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain);
2818                         const size_t postfix_len = dom->len;
2819                         char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1);
2820                         if (!newname) return NULL;
2821                         memcpy(newname, base_name, base_len);
2822                         if (need_to_append_dot) newname[base_len] = '.';
2823                         memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len);
2824                         newname[base_len + need_to_append_dot + postfix_len] = 0;
2825                         return newname;
2826                 }
2827         }
2828
2829         /* we ran off the end of the list and still didn't find the requested string */
2830         abort();
2831         return NULL; /* unreachable; stops warnings in some compilers. */
2832 }
2833
2834 static int
2835 search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg) {
2836         assert(type == TYPE_A || type == TYPE_AAAA);
2837         if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) &&
2838                  global_search_state &&
2839                  global_search_state->num_domains) {
2840                 /* we have some domains to search */
2841                 struct evdns_request *req;
2842                 if (string_num_dots(name) >= global_search_state->ndots) {
2843                         req = request_new(type, name, flags, user_callback, user_arg);
2844                         if (!req) return 1;
2845                         req->search_index = -1;
2846                 } else {
2847                         char *const new_name = search_make_new(global_search_state, 0, name);
2848                                                 if (!new_name) return 1;
2849                         req = request_new(type, new_name, flags, user_callback, user_arg);
2850                         _mm_free(new_name);
2851                         if (!req) return 1;
2852                         req->search_index = 0;
2853                 }
2854                 req->search_origname = mm_strdup(name);
2855                 req->search_state = global_search_state;
2856                 req->search_flags = flags;
2857                 global_search_state->refcount++;
2858                 request_submit(req);
2859                 return 0;
2860         } else {
2861                 struct evdns_request *const req = request_new(type, name, flags, user_callback, user_arg);
2862                 if (!req) return 1;
2863                 request_submit(req);
2864                 return 0;
2865         }
2866 }
2867
2868 /* this is called when a request has failed to find a name. We need to check */
2869 /* if it is part of a search and, if so, try the next name in the list */
2870 /* returns: */
2871 /* 0 another request has been submitted */
2872 /* 1 no more requests needed */
2873 static int
2874 search_try_next(struct evdns_request *const req) {
2875         if (req->search_state) {
2876                 /* it is part of a search */
2877                 char *new_name;
2878                 struct evdns_request *newreq;
2879                 req->search_index++;
2880                 if (req->search_index >= req->search_state->num_domains) {
2881                         /* no more postfixes to try, however we may need to try */
2882                         /* this name without a postfix */
2883                         if (string_num_dots(req->search_origname) < req->search_state->ndots) {
2884                                 /* yep, we need to try it raw */
2885                                 struct evdns_request *const newreq = request_new(req->request_type, req->search_origname, req->search_flags, req->user_callback, req->user_pointer);
2886                                 evdns_log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", req->search_origname);
2887                                 if (newreq) {
2888                                         request_submit(newreq);
2889                                         return 0;
2890                                 }
2891                         }
2892                         return 1;
2893                 }
2894
2895                 new_name = search_make_new(req->search_state, req->search_index, req->search_origname);
2896                                 if (!new_name) return 1;
2897                 evdns_log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, req->search_index);
2898                 newreq = request_new(req->request_type, new_name, req->search_flags, req->user_callback, req->user_pointer);
2899                 mm_free(new_name);
2900                 if (!newreq) return 1;
2901                 newreq->search_origname = req->search_origname;
2902                 req->search_origname = NULL;
2903                 newreq->search_state = req->search_state;
2904                 newreq->search_flags = req->search_flags;
2905                 newreq->search_index = req->search_index;
2906                 newreq->search_state->refcount++;
2907                 request_submit(newreq);
2908                 return 0;
2909         }
2910         return 1;
2911 }
2912
2913 static void
2914 search_request_finished(struct evdns_request *const req) {
2915         if (req->search_state) {
2916                 search_state_decref(req->search_state);
2917                 req->search_state = NULL;
2918         }
2919         if (req->search_origname) {
2920                 mm_free(req->search_origname);
2921                 req->search_origname = NULL;
2922         }
2923 }
2924
2925 /*/////////////////////////////////////////////////////////////////// */
2926 /* Parsing resolv.conf files */
2927
2928 static void
2929 evdns_resolv_set_defaults(int flags) {
2930         /* if the file isn't found then we assume a local resolver */
2931         if (flags & DNS_OPTION_SEARCH) search_set_from_hostname();
2932         if (flags & DNS_OPTION_NAMESERVERS) evdns_nameserver_ip_add("127.0.0.1");
2933 }
2934
2935 /* helper version of atoi which returns -1 on error */
2936 static int
2937 strtoint(const char *const str) {
2938         char *endptr;
2939         const long r = strtol(str, &endptr, 10);
2940         if (*endptr || r > INT_MAX) return -1;
2941         return (int)r;
2942 }
2943
2944 /* helper version of atoi that returns -1 on error and clips to bounds. */
2945 static int
2946 strtoint_clipped(const char *const str, int min, int max)
2947 {
2948         int r = strtoint(str);
2949         if (r == -1)
2950                 return r;
2951         else if (r<min)
2952                 return min;
2953         else if (r>max)
2954                 return max;
2955         else
2956                 return r;
2957 }
2958
2959 /* exported function */
2960 int
2961 evdns_set_option(const char *option, const char *val, int flags)
2962 {
2963         if (!strncmp(option, "ndots:", 6)) {
2964                 const int ndots = strtoint(val);
2965                 if (ndots == -1) return -1;
2966                 if (!(flags & DNS_OPTION_SEARCH)) return 0;
2967                 evdns_log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots);
2968                 if (!global_search_state) global_search_state = search_state_new();
2969                 if (!global_search_state) return -1;
2970                 global_search_state->ndots = ndots;
2971         } else if (!strncmp(option, "timeout:", 8)) {
2972                 const int timeout = strtoint(val);
2973                 if (timeout == -1) return -1;
2974                 if (!(flags & DNS_OPTION_MISC)) return 0;
2975                 evdns_log(EVDNS_LOG_DEBUG, "Setting timeout to %d", timeout);
2976                 global_timeout.tv_sec = timeout;
2977         } else if (!strncmp(option, "max-timeouts:", 12)) {
2978                 const int maxtimeout = strtoint_clipped(val, 1, 255);
2979                 if (maxtimeout == -1) return -1;
2980                 if (!(flags & DNS_OPTION_MISC)) return 0;
2981                 evdns_log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d",
2982                         maxtimeout);
2983                 global_max_nameserver_timeout = maxtimeout;
2984         } else if (!strncmp(option, "max-inflight:", 13)) {
2985                 const int maxinflight = strtoint_clipped(val, 1, 65000);
2986                 if (maxinflight == -1) return -1;
2987                 if (!(flags & DNS_OPTION_MISC)) return 0;
2988                 evdns_log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d",
2989                         maxinflight);
2990                 global_max_requests_inflight = maxinflight;
2991         } else if (!strncmp(option, "attempts:", 9)) {
2992                 int retries = strtoint(val);
2993                 if (retries == -1) return -1;
2994                 if (retries > 255) retries = 255;
2995                 if (!(flags & DNS_OPTION_MISC)) return 0;
2996                 evdns_log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries);
2997                 global_max_retransmits = retries;
2998         } else if (!strncmp(option, "randomize-case:", 15)) {
2999                 int randcase = strtoint(val);
3000                 if (!(flags & DNS_OPTION_MISC)) return 0;
3001                 evdns_log(EVDNS_LOG_DEBUG, "Setting randomize_case to %d", randcase);
3002                 global_randomize_case = randcase;
3003         }
3004         return 0;
3005 }
3006
3007 static void
3008 resolv_conf_parse_line(char *const start, int flags) {
3009         char *strtok_state;
3010         static const char *const delims = " \t";
3011 #define NEXT_TOKEN tor_strtok_r(NULL, delims, &strtok_state)
3012
3013         char *const first_token = tor_strtok_r(start, delims, &strtok_state);
3014         if (!first_token) return;
3015
3016         if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) {
3017                 const char *const nameserver = NEXT_TOKEN;
3018                 if (nameserver)
3019                         evdns_nameserver_ip_add(nameserver);
3020         } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) {
3021                 const char *const domain = NEXT_TOKEN;
3022                 if (domain) {
3023                         search_postfix_clear();
3024                         search_postfix_add(domain);
3025                 }
3026         } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) {
3027                 const char *domain;
3028                 search_postfix_clear();
3029
3030                 while ((domain = NEXT_TOKEN)) {
3031                         search_postfix_add(domain);
3032                 }
3033                 search_reverse();
3034         } else if (!strcmp(first_token, "options")) {
3035                 const char *option;
3036                 while ((option = NEXT_TOKEN)) {
3037                         const char *val = strchr(option, ':');
3038                         evdns_set_option(option, val ? val+1 : "", flags);
3039                 }
3040         }
3041 #undef NEXT_TOKEN
3042 }
3043
3044 /* exported function */
3045 /* returns: */
3046 /* 0 no errors */
3047 /* 1 failed to open file */
3048 /* 2 failed to stat file */
3049 /* 3 file too large */
3050 /* 4 out of memory */
3051 /* 5 short read from file */
3052 int
3053 evdns_resolv_conf_parse(int flags, const char *const filename) {
3054         struct stat st;
3055         int fd, n, r;
3056         u8 *resolv;
3057         char *start;
3058         int err = 0;
3059
3060         evdns_log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
3061
3062         fd = tor_open_cloexec(filename, O_RDONLY, 0);
3063         if (fd < 0) {
3064                 evdns_resolv_set_defaults(flags);
3065                 return 1;
3066         }
3067
3068         if (fstat(fd, &st)) { err = 2; goto out1; }
3069         if (!st.st_size) {
3070                 evdns_resolv_set_defaults(flags);
3071                 err = (flags & DNS_OPTION_NAMESERVERS) ? 6 : 0;
3072                 goto out1;
3073         }
3074         if (st.st_size > 65535) { err = 3; goto out1; }  /* no resolv.conf should be any bigger */
3075
3076         resolv = (u8 *) mm_malloc((size_t)st.st_size + 1);
3077         if (!resolv) { err = 4; goto out1; }
3078
3079     n = 0;
3080         while ((r = (int)read(fd, resolv+n, (size_t)st.st_size-n)) > 0) {
3081                 n += r;
3082                 if (n == st.st_size)
3083                         break;
3084                 assert(n < st.st_size);
3085         }
3086         if (r < 0) { err = 5; goto out2; }
3087         resolv[n] = 0;   /* we malloced an extra byte; this should be fine. */
3088
3089         start = (char *) resolv;
3090         for (;;) {
3091                 char *const newline = strchr(start, '\n');
3092                 if (!newline) {
3093                         resolv_conf_parse_line(start, flags);
3094                         break;
3095                 } else {
3096                         *newline = 0;
3097                         resolv_conf_parse_line(start, flags);
3098                         start = newline + 1;
3099                 }
3100         }
3101
3102         if (!server_head && (flags & DNS_OPTION_NAMESERVERS)) {
3103                 /* no nameservers were configured. */
3104                 evdns_nameserver_ip_add("127.0.0.1");
3105                 err = 6;
3106         }
3107         if (flags & DNS_OPTION_SEARCH && (!global_search_state || global_search_state->num_domains == 0)) {
3108                 search_set_from_hostname();
3109         }
3110
3111 out2:
3112         mm_free(resolv);
3113 out1:
3114         close(fd);
3115         return err;
3116 }
3117
3118 #ifdef _WIN32
3119 /* Add multiple nameservers from a space-or-comma-separated list. */
3120 static int
3121 evdns_nameserver_ip_add_line(const char *ips) {
3122         const char *addr;
3123         char *buf;
3124         int r;
3125         while (*ips) {
3126                 while (ISSPACE(*ips) || *ips == ',' || *ips == '\t')
3127                         ++ips;
3128                 addr = ips;
3129                 while (ISDIGIT(*ips) || *ips == '.' || *ips == ':' || *ips == '[' || *ips == ']')
3130                         ++ips;
3131                 buf = mm_malloc(ips-addr+1);
3132                 if (!buf) return 4;
3133                 memcpy(buf, addr, ips-addr);
3134                 buf[ips-addr] = '\0';
3135                 r = evdns_nameserver_ip_add(buf);
3136                 mm_free(buf);
3137                 if (r) return r;
3138         }
3139         return 0;
3140 }
3141
3142 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*);
3143
3144 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */
3145 /* figure out what our nameservers are. */
3146 static int
3147 load_nameservers_with_getnetworkparams(void)
3148 {
3149         /* Based on MSDN examples and inspection of      c-ares code. */
3150         FIXED_INFO *fixed;
3151         HMODULE handle = 0;
3152         ULONG size = sizeof(FIXED_INFO);
3153         void *buf = NULL;
3154         int status = 0, r, added_any;
3155         IP_ADDR_STRING *ns;
3156         GetNetworkParams_fn_t fn;
3157
3158         if (!(handle = load_windows_system_library(TEXT("iphlpapi.dll")))) {
3159                 evdns_log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll");
3160                 /* right now status = 0, doesn't that mean "good" - mikec */
3161                 status = -1;
3162                 goto done;
3163         }
3164         if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, TEXT("GetNetworkParams")))) {
3165                 evdns_log(EVDNS_LOG_WARN, "Could not get address of function.");
3166                 /* same as above */
3167                 status = -1;
3168                 goto done;
3169         }
3170
3171         buf = mm_malloc(size);
3172         if (!buf) { status = 4; goto done; }
3173         fixed = buf;
3174         r = fn(fixed, &size);
3175         if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) {
3176                 status = -1;
3177                 goto done;
3178         }
3179         if (r != ERROR_SUCCESS) {
3180                 mm_free(buf);
3181                 buf = mm_malloc(size);
3182                 if (!buf) { status = 4; goto done; }
3183                 fixed = buf;
3184                 r = fn(fixed, &size);
3185                 if (r != ERROR_SUCCESS) {
3186                         evdns_log(EVDNS_LOG_DEBUG, "fn() failed.");
3187                         status = -1;
3188                         goto done;
3189                 }
3190         }
3191
3192         assert(fixed);
3193         added_any = 0;
3194         ns = &(fixed->DnsServerList);
3195         while (ns) {
3196                 r = evdns_nameserver_ip_add_line(ns->IpAddress.String);
3197                 if (r) {
3198                         evdns_log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list, "
3199                                 "error: %d; status: %d",
3200                                 (ns->IpAddress.String),(int)GetLastError(), r);
3201                         status = r;
3202                 } else {
3203                         evdns_log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String);
3204                         added_any++;
3205                 }
3206
3207                 ns = ns->Next;
3208         }
3209
3210         if (!added_any) {
3211                 evdns_log(EVDNS_LOG_DEBUG, "No nameservers added.");
3212                 if (status == 0)
3213                         status = -1;
3214         } else {
3215                 status = 0;
3216         }
3217
3218  done:
3219         if (buf)
3220                 mm_free(buf);
3221         if (handle)
3222                 FreeLibrary(handle);
3223         return status;
3224 }
3225
3226 static int
3227 config_nameserver_from_reg_key(HKEY key, const TCHAR *subkey)
3228 {
3229         char *buf;
3230         char ansibuf[MAX_PATH] = {0};
3231         DWORD bufsz = 0, type = 0;
3232         int status = 0;
3233
3234         if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz)
3235                 != ERROR_MORE_DATA)
3236                 return -1;
3237         if (!(buf = mm_malloc(bufsz)))
3238                 return -1;
3239
3240         if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
3241                 == ERROR_SUCCESS && bufsz > 1) {
3242                 wcstombs(ansibuf,(wchar_t*)buf,MAX_PATH);/*XXXX UNICODE */
3243                 abuf[MAX_PATH-1] = '\0';
3244                 status = evdns_nameserver_ip_add_line(ansibuf);
3245         }
3246
3247         mm_free(buf);
3248         return status;
3249 }
3250
3251 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\")
3252 #define WIN_NS_9X_KEY  SERVICES_KEY TEXT("VxD\\MSTCP")
3253 #define WIN_NS_NT_KEY  SERVICES_KEY TEXT("Tcpip\\Parameters")
3254
3255 static int
3256 load_nameservers_from_registry(void)
3257 {
3258         int found = 0;
3259         int r;
3260         OSVERSIONINFO info;
3261         memset(&info, 0, sizeof(info));
3262         info.dwOSVersionInfoSize = sizeof (info);
3263         GetVersionEx(&info);
3264
3265 #define TRY(k, name)                                                                                                    \
3266         if (!found && config_nameserver_from_reg_key(k,TEXT(name)) == 0) {      \
3267                 evdns_log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name);                \
3268                 found = 1;                                                                                                              \
3269         } else if (!found) {                                                                                            \
3270                 evdns_log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s",                   \
3271                         #k,#name);                                                                                                      \
3272         }
3273
3274         if (info.dwMajorVersion >= 5) { /* NT */
3275                 HKEY nt_key = 0, interfaces_key = 0;
3276
3277                 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0,
3278                                                  KEY_READ, &nt_key) != ERROR_SUCCESS) {
3279                         evdns_log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError());
3280                         return -1;
3281                 }
3282                 r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0,
3283                                                  KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS,
3284                                                  &interfaces_key);
3285                 if (r != ERROR_SUCCESS) {
3286                         evdns_log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError());
3287                         return -1;
3288                 }
3289                 TRY(nt_key, "NameServer");
3290                 TRY(nt_key, "DhcpNameServer");
3291                 TRY(interfaces_key, "NameServer");
3292                 TRY(interfaces_key, "DhcpNameServer");
3293                 RegCloseKey(interfaces_key);
3294                 RegCloseKey(nt_key);
3295         } else {
3296                 HKEY win_key = 0;
3297                 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0,
3298                                                  KEY_READ, &win_key) != ERROR_SUCCESS) {
3299                         evdns_log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError());
3300                         return -1;
3301                 }
3302                 TRY(win_key, "NameServer");
3303                 RegCloseKey(win_key);
3304         }
3305
3306         if (found == 0) {
3307                 evdns_log(EVDNS_LOG_WARN,"Didn't find any nameservers.");
3308         }
3309
3310         return found ? 0 : -1;
3311 #undef TRY
3312 }
3313
3314 int
3315 evdns_config_windows_nameservers(void)
3316 {
3317         if (load_nameservers_with_getnetworkparams() == 0)
3318                 return 0;
3319         return load_nameservers_from_registry();
3320 }
3321 #endif
3322
3323 int
3324 evdns_init(void)
3325 {
3326                 int res = 0;
3327 #ifdef _WIN32
3328                 evdns_config_windows_nameservers();
3329 #else
3330                 res = evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
3331 #endif
3332
3333                 return (res);
3334 }
3335
3336 const char *
3337 evdns_err_to_string(int err)
3338 {
3339         switch (err) {
3340         case DNS_ERR_NONE: return "no error";
3341         case DNS_ERR_FORMAT: return "misformatted query";
3342         case DNS_ERR_SERVERFAILED: return "server failed";
3343         case DNS_ERR_NOTEXIST: return "name does not exist";
3344         case DNS_ERR_NOTIMPL: return "query not implemented";
3345         case DNS_ERR_REFUSED: return "refused";
3346
3347         case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed";
3348         case DNS_ERR_UNKNOWN: return "unknown";
3349         case DNS_ERR_TIMEOUT: return "request timed out";
3350         case DNS_ERR_SHUTDOWN: return "dns subsystem shut down";
3351         default: return "[Unknown error code]";
3352         }
3353 }
3354
3355 void
3356 evdns_shutdown(int fail_requests)
3357 {
3358         struct nameserver *server, *server_next;
3359         struct search_domain *dom, *dom_next;
3360
3361         while (req_head) {
3362                 if (fail_requests)
3363                         reply_callback(req_head, 0, DNS_ERR_SHUTDOWN, NULL);
3364                 request_finished(req_head, &req_head);
3365         }
3366         while (req_waiting_head) {
3367                 if (fail_requests)
3368                         reply_callback(req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL);
3369                 request_finished(req_waiting_head, &req_waiting_head);
3370         }
3371         global_requests_inflight = global_requests_waiting = 0;
3372
3373         for (server = server_head; server; server = server_next) {
3374                 server_next = server->next;
3375                 if (server->socket >= 0)
3376                         CLOSE_SOCKET(server->socket);
3377                 (void) event_del(&server->event);
3378                 del_timeout_event(server);
3379                 CLEAR(server);
3380                 mm_free(server);
3381                 if (server_next == server_head)
3382                         break;
3383         }
3384         server_head = NULL;
3385         global_good_nameservers = 0;
3386
3387         if (global_search_state) {
3388                 for (dom = global_search_state->head; dom; dom = dom_next) {
3389                         dom_next = dom->next;
3390                         CLEAR(dom);
3391                         mm_free(dom);
3392                 }
3393                 CLEAR(global_search_state);
3394                 mm_free(global_search_state);
3395                 global_search_state = NULL;
3396         }
3397         evdns_log_fn = NULL;
3398 }
3399
3400 #ifdef EVDNS_MAIN
3401 void
3402 main_callback(int result, char type, int count, int ttl,
3403                           void *addrs, void *orig) {
3404         char *n = (char*)orig;
3405         int i;
3406         for (i = 0; i < count; ++i) {
3407                 if (type == DNS_IPv4_A) {
3408                         printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i]));
3409                 } else if (type == DNS_PTR) {
3410                         printf("%s: %s\n", n, ((char**)addrs)[i]);
3411                 }
3412         }
3413         if (!count) {
3414                 printf("%s: No answer (%d)\n", n, result);
3415         }
3416         fflush(stdout);
3417 }
3418 void
3419 evdns_server_callback(struct evdns_server_request *req, void *data)
3420 {
3421         int i, r;
3422         (void)data;
3423         /* dummy; give 192.168.11.11 as an answer for all A questions,
3424          *      give foo.bar.example.com as an answer for all PTR questions. */
3425         for (i = 0; i < req->nquestions; ++i) {
3426                 u32 ans = htonl(0xc0a80b0bUL);
3427                 if (req->questions[i]->type == EVDNS_TYPE_A &&
3428                         req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
3429                         printf(" -- replying for %s (A)\n", req->questions[i]->name);
3430                         r = evdns_server_request_add_a_reply(req, req->questions[i]->name,
3431                                                                                   1, &ans, 10);
3432                         if (r<0)
3433                                 printf("eeep, didn't work.\n");
3434                 } else if (req->questions[i]->type == EVDNS_TYPE_PTR &&
3435                                    req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
3436                         printf(" -- replying for %s (PTR)\n", req->questions[i]->name);
3437                         r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name,
3438                                                                                         "foo.bar.example.com", 10);
3439                 } else {
3440                         printf(" -- skipping %s [%d %d]\n", req->questions[i]->name,
3441                                    req->questions[i]->type, req->questions[i]->dns_question_class);
3442                 }
3443         }
3444
3445         r = evdns_server_request_respond(req, 0);
3446         if (r<0)
3447                 printf("eeek, couldn't send reply.\n");
3448 }
3449
3450 void
3451 logfn(int is_warn, const char *msg) {
3452         (void) is_warn;
3453         fprintf(stderr, "%s\n", msg);
3454 }
3455 int
3456 main(int c, char **v) {
3457         int idx;
3458         int reverse = 0, verbose = 1, servertest = 0;
3459         if (c<2) {
3460                 fprintf(stderr, "syntax: %s [-x] [-v] hostname\n", v[0]);
3461                 fprintf(stderr, "syntax: %s [-servertest]\n", v[0]);
3462                 return 1;
3463         }
3464         idx = 1;
3465         while (idx < c && v[idx][0] == '-') {
3466                 if (!strcmp(v[idx], "-x"))
3467                         reverse = 1;
3468                 else if (!strcmp(v[idx], "-v"))
3469                         verbose = 1;
3470                 else if (!strcmp(v[idx], "-servertest"))
3471                         servertest = 1;
3472                 else
3473                         fprintf(stderr, "Unknown option %s\n", v[idx]);
3474                 ++idx;
3475         }
3476         event_init();
3477         if (verbose)
3478                 evdns_set_log_fn(logfn);
3479         evdns_resolv_conf_parse(DNS_OPTION_NAMESERVERS, "/etc/resolv.conf");
3480         if (servertest) {
3481                 int sock;
3482                 struct sockaddr_in my_addr;
3483 #if 1
3484                 sock = tor_open_socket_nonblocking(PF_INET, SOCK_DGRAM, 0)
3485 #else
3486                 sock = tor_open_socket(PF_INET, SOCK_DGRAM, 0);
3487                 fcntl(sock, F_SETFL, O_NONBLOCK);
3488 #endif
3489                 my_addr.sin_family = AF_INET;
3490                 my_addr.sin_port = htons(10053);
3491                 my_addr.sin_addr.s_addr = INADDR_ANY;
3492                 if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) {
3493                         perror("bind");
3494                         exit(1);
3495                 }
3496                 evdns_add_server_port(sock, 0, evdns_server_callback, NULL);
3497         }
3498         for (; idx < c; ++idx) {
3499                 if (reverse) {
3500                         struct in_addr addr;
3501                         if (!inet_aton(v[idx], &addr)) {
3502                                 fprintf(stderr, "Skipping non-IP %s\n", v[idx]);
3503                                 continue;
3504                         }
3505                         fprintf(stderr, "resolving %s...\n",v[idx]);
3506                         evdns_resolve_reverse(&addr, 0, main_callback, v[idx]);
3507                 } else {
3508                         fprintf(stderr, "resolving (fwd) %s...\n",v[idx]);
3509                         evdns_resolve_ipv4(v[idx], 0, main_callback, v[idx]);
3510                 }
3511         }
3512         fflush(stdout);
3513         event_dispatch();
3514         return 0;
3515 }
3516 #endif
3517
3518 /* Local Variables: */
3519 /* tab-width: 4 */
3520 /* c-basic-offset: 4 */
3521 /* indent-tabs-mode: t */
3522 /* End: */
3523