Edit
kc3-lang/libevent/evdns.c
Greg Hazel
- evdns.c
-
/* Copyright 2006-2007 Niels Provos * Copyright 2007-2012 Nick Mathewson and Niels Provos * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* Based on software by Adam Langly. Adam's original message: * * Async DNS Library * Adam Langley <agl@imperialviolet.org> * http://www.imperialviolet.org/eventdns.html * Public Domain code * * This software is Public Domain. To view a copy of the public domain dedication, * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. * * I ask and expect, but do not require, that all derivative works contain an * attribution similar to: * Parts developed by Adam Langley <agl@imperialviolet.org> * * You may wish to replace the word "Parts" with something else depending on * the amount of original code. * * (Derivative works does not include programs which link against, run or include * the source verbatim in their source distributions) * * Version: 0.1b */ #include <sys/types.h> #include "event2/event-config.h" #ifndef _FORTIFY_SOURCE #define _FORTIFY_SOURCE 3 #endif #include <string.h> #include <fcntl.h> #ifdef _EVENT_HAVE_SYS_TIME_H #include <sys/time.h> #endif #ifdef _EVENT_HAVE_STDINT_H #include <stdint.h> #endif #include <stdlib.h> #include <string.h> #include <errno.h> #ifdef _EVENT_HAVE_UNISTD_H #include <unistd.h> #endif #include <limits.h> #include <sys/stat.h> #include <stdio.h> #include <stdarg.h> #ifdef WIN32 #include <winsock2.h> #include <ws2tcpip.h> #ifndef _WIN32_IE #define _WIN32_IE 0x400 #endif #include <shlobj.h> #endif #include "event2/dns.h" #include "event2/dns_struct.h" #include "event2/dns_compat.h" #include "event2/util.h" #include "event2/event.h" #include "event2/event_struct.h" #include "event2/thread.h" #include "event2/bufferevent.h" #include "event2/bufferevent_struct.h" #include "bufferevent-internal.h" #include "defer-internal.h" #include "log-internal.h" #include "mm-internal.h" #include "strlcpy-internal.h" #include "ipv6-internal.h" #include "util-internal.h" #include "evthread-internal.h" #ifdef WIN32 #include <ctype.h> #include <winsock2.h> #include <windows.h> #include <iphlpapi.h> #include <io.h> #else #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #endif #ifdef _EVENT_HAVE_NETINET_IN6_H #include <netinet/in6.h> #endif #define EVDNS_LOG_DEBUG 0 #define EVDNS_LOG_WARN 1 #define EVDNS_LOG_MSG 2 #ifndef HOST_NAME_MAX #define HOST_NAME_MAX 255 #endif #include <stdio.h> #undef MIN #define MIN(a,b) ((a)<(b)?(a):(b)) #define ASSERT_VALID_REQUEST(req) \ EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req)) #define u64 ev_uint64_t #define u32 ev_uint32_t #define u16 ev_uint16_t #define u8 ev_uint8_t /* maximum number of addresses from a single packet */ /* that we bother recording */ #define MAX_V4_ADDRS 32 #define MAX_V6_ADDRS 32 #define TYPE_A EVDNS_TYPE_A #define TYPE_CNAME 5 #define TYPE_PTR EVDNS_TYPE_PTR #define TYPE_SOA EVDNS_TYPE_SOA #define TYPE_AAAA EVDNS_TYPE_AAAA #define CLASS_INET EVDNS_CLASS_INET /* Persistent handle. We keep this separate from 'struct request' since we * need some object to last for as long as an evdns_request is outstanding so * that it can be canceled, whereas a search request can lead to multiple * 'struct request' instances being created over its lifetime. */ struct evdns_request { struct request *current_req; struct evdns_base *base; int pending_cb; /* Waiting for its callback to be invoked; not * owned by event base any more. */ /* elements used by the searching code */ int search_index; struct search_state *search_state; char *search_origname; /* needs to be free()ed */ int search_flags; }; struct request { u8 *request; /* the dns packet data */ u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */ unsigned int request_len; int reissue_count; int tx_count; /* the number of times that this packet has been sent */ void *user_pointer; /* the pointer given to us for this request */ evdns_callback_type user_callback; struct nameserver *ns; /* the server which we last sent it */ /* these objects are kept in a circular list */ /* XXX We could turn this into a CIRCLEQ. */ struct request *next, *prev; struct event timeout_event; u16 trans_id; /* the transaction id */ unsigned request_appended :1; /* true if the request pointer is data which follows this struct */ unsigned transmit_me :1; /* needs to be transmitted */ /* XXXX This is a horrible hack. */ char **put_cname_in_ptr; /* store the cname here if we get one. */ struct evdns_base *base; struct evdns_request *handle; }; struct reply { unsigned int type; unsigned int have_answer : 1; union { struct { u32 addrcount; u32 addresses[MAX_V4_ADDRS]; } a; struct { u32 addrcount; struct in6_addr addresses[MAX_V6_ADDRS]; } aaaa; struct { char name[HOST_NAME_MAX]; } ptr; } data; }; struct nameserver { evutil_socket_t socket; /* a connected UDP socket */ struct sockaddr_storage address; ev_socklen_t addrlen; int failed_times; /* number of times which we have given this server a chance */ int timedout; /* number of times in a row a request has timed out */ struct event event; /* these objects are kept in a circular list */ struct nameserver *next, *prev; struct event timeout_event; /* used to keep the timeout for */ /* when we next probe this server. */ /* Valid if state == 0 */ /* Outstanding probe request for this nameserver, if any */ struct evdns_request *probe_request; char state; /* zero if we think that this server is down */ char choked; /* true if we have an EAGAIN from this server's socket */ char write_waiting; /* true if we are waiting for EV_WRITE events */ struct evdns_base *base; }; /* Represents a local port where we're listening for DNS requests. Right now, */ /* only UDP is supported. */ struct evdns_server_port { evutil_socket_t socket; /* socket we use to read queries and write replies. */ int refcnt; /* reference count. */ char choked; /* Are we currently blocked from writing? */ char closing; /* Are we trying to close this port, pending writes? */ evdns_request_callback_fn_type user_callback; /* Fn to handle requests */ void *user_data; /* Opaque pointer passed to user_callback */ struct event event; /* Read/write event */ /* circular list of replies that we want to write. */ struct server_request *pending_replies; struct event_base *event_base; #ifndef _EVENT_DISABLE_THREAD_SUPPORT void *lock; #endif }; /* Represents part of a reply being built. (That is, a single RR.) */ struct server_reply_item { struct server_reply_item *next; /* next item in sequence. */ char *name; /* name part of the RR */ u16 type; /* The RR type */ u16 class; /* The RR class (usually CLASS_INET) */ u32 ttl; /* The RR TTL */ char is_name; /* True iff data is a label */ u16 datalen; /* Length of data; -1 if data is a label */ void *data; /* The contents of the RR */ }; /* Represents a request that we've received as a DNS server, and holds */ /* the components of the reply as we're constructing it. */ struct server_request { /* Pointers to the next and previous entries on the list of replies */ /* that we're waiting to write. Only set if we have tried to respond */ /* and gotten EAGAIN. */ struct server_request *next_pending; struct server_request *prev_pending; u16 trans_id; /* Transaction id. */ struct evdns_server_port *port; /* Which port received this request on? */ struct sockaddr_storage addr; /* Where to send the response */ ev_socklen_t addrlen; /* length of addr */ int n_answer; /* how many answer RRs have been set? */ int n_authority; /* how many authority RRs have been set? */ int n_additional; /* how many additional RRs have been set? */ struct server_reply_item *answer; /* linked list of answer RRs */ struct server_reply_item *authority; /* linked list of authority RRs */ struct server_reply_item *additional; /* linked list of additional RRs */ /* Constructed response. Only set once we're ready to send a reply. */ /* Once this is set, the RR fields are cleared, and no more should be set. */ char *response; size_t response_len; /* Caller-visible fields: flags, questions. */ struct evdns_server_request base; }; struct evdns_base { /* An array of n_req_heads circular lists for inflight requests. * Each inflight request req is in req_heads[req->trans_id % n_req_heads]. */ struct request **req_heads; /* A circular list of requests that we're waiting to send, but haven't * sent yet because there are too many requests inflight */ struct request *req_waiting_head; /* A circular list of nameservers. */ struct nameserver *server_head; int n_req_heads; struct event_base *event_base; /* The number of good nameservers that we have */ int global_good_nameservers; /* inflight requests are contained in the req_head list */ /* and are actually going out across the network */ int global_requests_inflight; /* requests which aren't inflight are in the waiting list */ /* and are counted here */ int global_requests_waiting; int global_max_requests_inflight; struct timeval global_timeout; /* 5 seconds by default */ int global_max_reissues; /* a reissue occurs when we get some errors from the server */ int global_max_retransmits; /* number of times we'll retransmit a request which timed out */ /* number of timeouts in a row before we consider this server to be down */ int global_max_nameserver_timeout; /* true iff we will use the 0x20 hack to prevent poisoning attacks. */ int global_randomize_case; /* The first time that a nameserver fails, how long do we wait before * probing to see if it has returned? */ struct timeval global_nameserver_probe_initial_timeout; /** Port to bind to for outgoing DNS packets. */ struct sockaddr_storage global_outgoing_address; /** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */ ev_socklen_t global_outgoing_addrlen; struct timeval global_getaddrinfo_allow_skew; int getaddrinfo_ipv4_timeouts; int getaddrinfo_ipv6_timeouts; int getaddrinfo_ipv4_answered; int getaddrinfo_ipv6_answered; struct search_state *global_search_state; TAILQ_HEAD(hosts_list, hosts_entry) hostsdb; #ifndef _EVENT_DISABLE_THREAD_SUPPORT void *lock; #endif }; struct hosts_entry { TAILQ_ENTRY(hosts_entry) next; union { struct sockaddr sa; struct sockaddr_in sin; struct sockaddr_in6 sin6; } addr; int addrlen; char hostname[1]; }; static struct evdns_base *current_base = NULL; struct evdns_base * evdns_get_global_base(void) { return current_base; } /* Given a pointer to an evdns_server_request, get the corresponding */ /* server_request. */ #define TO_SERVER_REQUEST(base_ptr) \ ((struct server_request*) \ (((char*)(base_ptr) - evutil_offsetof(struct server_request, base)))) #define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads]) static struct nameserver *nameserver_pick(struct evdns_base *base); static void evdns_request_insert(struct request *req, struct request **head); static void evdns_request_remove(struct request *req, struct request **head); static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg); static int evdns_transmit(struct evdns_base *base); static int evdns_request_transmit(struct request *req); static void nameserver_send_probe(struct nameserver *const ns); static void search_request_finished(struct evdns_request *const); static int search_try_next(struct evdns_request *const req); static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg); static void evdns_requests_pump_waiting_queue(struct evdns_base *base); static u16 transaction_id_pick(struct evdns_base *base); static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr); static void request_submit(struct request *const req); static int server_request_free(struct server_request *req); static void server_request_free_answers(struct server_request *req); static void server_port_free(struct evdns_server_port *port); static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg); static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename); static int evdns_base_set_option_impl(struct evdns_base *base, const char *option, const char *val, int flags); static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests); static int strtoint(const char *const str); #ifdef _EVENT_DISABLE_THREAD_SUPPORT #define EVDNS_LOCK(base) _EVUTIL_NIL_STMT #define EVDNS_UNLOCK(base) _EVUTIL_NIL_STMT #define ASSERT_LOCKED(base) _EVUTIL_NIL_STMT #else #define EVDNS_LOCK(base) \ EVLOCK_LOCK((base)->lock, 0) #define EVDNS_UNLOCK(base) \ EVLOCK_UNLOCK((base)->lock, 0) #define ASSERT_LOCKED(base) \ EVLOCK_ASSERT_LOCKED((base)->lock) #endif static void default_evdns_log_fn(int warning, const char *buf) { if (warning == EVDNS_LOG_WARN) event_warnx("[evdns] %s", buf); else if (warning == EVDNS_LOG_MSG) event_msgx("[evdns] %s", buf); else event_debug(("[evdns] %s", buf)); } static evdns_debug_log_fn_type evdns_log_fn = NULL; void evdns_set_log_fn(evdns_debug_log_fn_type fn) { evdns_log_fn = fn; } #ifdef __GNUC__ #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3))) #else #define EVDNS_LOG_CHECK #endif static void _evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK; static void _evdns_log(int warn, const char *fmt, ...) { va_list args; char buf[512]; if (!evdns_log_fn) return; va_start(args,fmt); evutil_vsnprintf(buf, sizeof(buf), fmt, args); va_end(args); if (evdns_log_fn) { if (warn == EVDNS_LOG_MSG) warn = EVDNS_LOG_WARN; evdns_log_fn(warn, buf); } else { default_evdns_log_fn(warn, buf); } } #define log _evdns_log /* This walks the list of inflight requests to find the */ /* one with a matching transaction id. Returns NULL on */ /* failure */ static struct request * request_find_from_trans_id(struct evdns_base *base, u16 trans_id) { struct request *req = REQ_HEAD(base, trans_id); struct request *const started_at = req; ASSERT_LOCKED(base); if (req) { do { if (req->trans_id == trans_id) return req; req = req->next; } while (req != started_at); } return NULL; } /* a libevent callback function which is called when a nameserver */ /* has gone down and we want to test if it has came back to life yet */ static void nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) { struct nameserver *const ns = (struct nameserver *) arg; (void)fd; (void)events; EVDNS_LOCK(ns->base); nameserver_send_probe(ns); EVDNS_UNLOCK(ns->base); } /* a libevent callback which is called when a nameserver probe (to see if */ /* it has come back to life) times out. We increment the count of failed_times */ /* and wait longer to send the next probe packet. */ static void nameserver_probe_failed(struct nameserver *const ns) { struct timeval timeout; int i; ASSERT_LOCKED(ns->base); (void) evtimer_del(&ns->timeout_event); if (ns->state == 1) { /* This can happen if the nameserver acts in a way which makes us mark */ /* it as bad and then starts sending good replies. */ return; } #define MAX_PROBE_TIMEOUT 3600 #define TIMEOUT_BACKOFF_FACTOR 3 memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout, sizeof(struct timeval)); for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) { timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR; timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR; if (timeout.tv_usec > 1000000) { timeout.tv_sec += timeout.tv_usec / 1000000; timeout.tv_usec %= 1000000; } } if (timeout.tv_sec > MAX_PROBE_TIMEOUT) { timeout.tv_sec = MAX_PROBE_TIMEOUT; timeout.tv_usec = 0; } ns->failed_times++; if (evtimer_add(&ns->timeout_event, &timeout) < 0) { char addrbuf[128]; log(EVDNS_LOG_WARN, "Error from libevent when adding timer event for %s", evutil_format_sockaddr_port( (struct sockaddr *)&ns->address, addrbuf, sizeof(addrbuf))); } } /* called when a nameserver has been deemed to have failed. For example, too */ /* many packets have timed out etc */ static void nameserver_failed(struct nameserver *const ns, const char *msg) { struct request *req, *started_at; struct evdns_base *base = ns->base; int i; char addrbuf[128]; ASSERT_LOCKED(base); /* if this nameserver has already been marked as failed */ /* then don't do anything */ if (!ns->state) return; log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s", evutil_format_sockaddr_port( (struct sockaddr *)&ns->address, addrbuf, sizeof(addrbuf)), msg); base->global_good_nameservers--; EVUTIL_ASSERT(base->global_good_nameservers >= 0); if (base->global_good_nameservers == 0) { log(EVDNS_LOG_MSG, "All nameservers have failed"); } ns->state = 0; ns->failed_times = 1; if (evtimer_add(&ns->timeout_event, &base->global_nameserver_probe_initial_timeout) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding timer event for %s", evutil_format_sockaddr_port( (struct sockaddr *)&ns->address, addrbuf, sizeof(addrbuf))); /* ???? Do more? */ } /* walk the list of inflight requests to see if any can be reassigned to */ /* a different server. Requests in the waiting queue don't have a */ /* nameserver assigned yet */ /* if we don't have *any* good nameservers then there's no point */ /* trying to reassign requests to one */ if (!base->global_good_nameservers) return; for (i = 0; i < base->n_req_heads; ++i) { req = started_at = base->req_heads[i]; if (req) { do { if (req->tx_count == 0 && req->ns == ns) { /* still waiting to go out, can be moved */ /* to another server */ req->ns = nameserver_pick(base); } req = req->next; } while (req != started_at); } } } static void nameserver_up(struct nameserver *const ns) { char addrbuf[128]; ASSERT_LOCKED(ns->base); if (ns->state) return; log(EVDNS_LOG_MSG, "Nameserver %s is back up", evutil_format_sockaddr_port( (struct sockaddr *)&ns->address, addrbuf, sizeof(addrbuf))); evtimer_del(&ns->timeout_event); if (ns->probe_request) { evdns_cancel_request(ns->base, ns->probe_request); ns->probe_request = NULL; } ns->state = 1; ns->failed_times = 0; ns->timedout = 0; ns->base->global_good_nameservers++; } static void request_trans_id_set(struct request *const req, const u16 trans_id) { req->trans_id = trans_id; *((u16 *) req->request) = htons(trans_id); } /* Called to remove a request from a list and dealloc it. */ /* head is a pointer to the head of the list it should be */ /* removed from or NULL if the request isn't in a list. */ /* when free_handle is one, free the handle as well. */ static void request_finished(struct request *const req, struct request **head, int free_handle) { struct evdns_base *base = req->base; int was_inflight = (head != &base->req_waiting_head); EVDNS_LOCK(base); ASSERT_VALID_REQUEST(req); if (head) evdns_request_remove(req, head); log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req); if (was_inflight) { evtimer_del(&req->timeout_event); base->global_requests_inflight--; } else { base->global_requests_waiting--; } /* it was initialized during request_new / evtimer_assign */ event_debug_unassign(&req->timeout_event); if (!req->request_appended) { /* need to free the request data on it's own */ mm_free(req->request); } else { /* the request data is appended onto the header */ /* so everything gets free()ed when we: */ } if (req->handle) { EVUTIL_ASSERT(req->handle->current_req == req); if (free_handle) { search_request_finished(req->handle); req->handle->current_req = NULL; if (! req->handle->pending_cb) { /* If we're planning to run the callback, * don't free the handle until later. */ mm_free(req->handle); } req->handle = NULL; /* If we have a bug, let's crash * early */ } else { req->handle->current_req = NULL; } } mm_free(req); evdns_requests_pump_waiting_queue(base); EVDNS_UNLOCK(base); } /* This is called when a server returns a funny error code. */ /* We try the request again with another server. */ /* */ /* return: */ /* 0 ok */ /* 1 failed/reissue is pointless */ static int request_reissue(struct request *req) { const struct nameserver *const last_ns = req->ns; ASSERT_LOCKED(req->base); ASSERT_VALID_REQUEST(req); /* the last nameserver should have been marked as failing */ /* by the caller of this function, therefore pick will try */ /* not to return it */ req->ns = nameserver_pick(req->base); if (req->ns == last_ns) { /* ... but pick did return it */ /* not a lot of point in trying again with the */ /* same server */ return 1; } req->reissue_count++; req->tx_count = 0; req->transmit_me = 1; return 0; } /* this function looks for space on the inflight queue and promotes */ /* requests from the waiting queue if it can. */ static void evdns_requests_pump_waiting_queue(struct evdns_base *base) { ASSERT_LOCKED(base); while (base->global_requests_inflight < base->global_max_requests_inflight && base->global_requests_waiting) { struct request *req; /* move a request from the waiting queue to the inflight queue */ EVUTIL_ASSERT(base->req_waiting_head); req = base->req_waiting_head; evdns_request_remove(req, &base->req_waiting_head); base->global_requests_waiting--; base->global_requests_inflight++; req->ns = nameserver_pick(base); request_trans_id_set(req, transaction_id_pick(base)); evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); evdns_request_transmit(req); evdns_transmit(base); } } /* TODO(nickm) document */ struct deferred_reply_callback { struct deferred_cb deferred; struct evdns_request *handle; u8 request_type; u8 have_reply; u32 ttl; u32 err; evdns_callback_type user_callback; struct reply reply; }; static void reply_run_callback(struct deferred_cb *d, void *user_pointer) { struct deferred_reply_callback *cb = EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred); switch (cb->request_type) { case TYPE_A: if (cb->have_reply) cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A, cb->reply.data.a.addrcount, cb->ttl, cb->reply.data.a.addresses, user_pointer); else cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); break; case TYPE_PTR: if (cb->have_reply) { char *name = cb->reply.data.ptr.name; cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl, &name, user_pointer); } else { cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); } break; case TYPE_AAAA: if (cb->have_reply) cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, cb->reply.data.aaaa.addrcount, cb->ttl, cb->reply.data.aaaa.addresses, user_pointer); else cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer); break; default: EVUTIL_ASSERT(0); } if (cb->handle && cb->handle->pending_cb) { mm_free(cb->handle); } mm_free(cb); } static void reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) { struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d)); if (!d) { event_warn("%s: Couldn't allocate space for deferred callback.", __func__); return; } ASSERT_LOCKED(req->base); d->request_type = req->request_type; d->user_callback = req->user_callback; d->ttl = ttl; d->err = err; if (reply) { d->have_reply = 1; memcpy(&d->reply, reply, sizeof(struct reply)); } if (req->handle) { req->handle->pending_cb = 1; d->handle = req->handle; } event_deferred_cb_init(&d->deferred, reply_run_callback, req->user_pointer); event_deferred_cb_schedule( event_base_get_deferred_cb_queue(req->base->event_base), &d->deferred); } /* this processes a parsed reply packet */ static void reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) { int error; char addrbuf[128]; static const int error_codes[] = { DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, DNS_ERR_NOTIMPL, DNS_ERR_REFUSED }; ASSERT_LOCKED(req->base); ASSERT_VALID_REQUEST(req); if (flags & 0x020f || !reply || !reply->have_answer) { /* there was an error */ if (flags & 0x0200) { error = DNS_ERR_TRUNCATED; } else if (flags & 0x000f) { u16 error_code = (flags & 0x000f) - 1; if (error_code > 4) { error = DNS_ERR_UNKNOWN; } else { error = error_codes[error_code]; } } else if (reply && !reply->have_answer) { error = DNS_ERR_NODATA; } else { error = DNS_ERR_UNKNOWN; } switch (error) { case DNS_ERR_NOTIMPL: case DNS_ERR_REFUSED: /* we regard these errors as marking a bad nameserver */ if (req->reissue_count < req->base->global_max_reissues) { char msg[64]; evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)", error, evdns_err_to_string(error)); nameserver_failed(req->ns, msg); if (!request_reissue(req)) return; } break; case DNS_ERR_SERVERFAILED: /* rcode 2 (servfailed) sometimes means "we * are broken" and sometimes (with some binds) * means "that request was very confusing." * Treat this as a timeout, not a failure. */ log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver" "at %s; will allow the request to time out.", evutil_format_sockaddr_port( (struct sockaddr *)&req->ns->address, addrbuf, sizeof(addrbuf))); break; default: /* we got a good reply from the nameserver: it is up. */ if (req->handle == req->ns->probe_request) { /* Avoid double-free */ req->ns->probe_request = NULL; } nameserver_up(req->ns); } if (req->handle->search_state && req->request_type != TYPE_PTR) { /* if we have a list of domains to search in, * try the next one */ if (!search_try_next(req->handle)) { /* a new request was issued so this * request is finished and */ /* the user callback will be made when * that request (or a */ /* child of it) finishes. */ return; } } /* all else failed. Pass the failure up */ reply_schedule_callback(req, ttl, error, NULL); request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); } else { /* all ok, tell the user */ reply_schedule_callback(req, ttl, 0, reply); if (req->handle == req->ns->probe_request) req->ns->probe_request = NULL; /* Avoid double-free */ nameserver_up(req->ns); request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); } } static int name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) { int name_end = -1; int j = *idx; int ptr_count = 0; #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while (0) #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while (0) #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0) char *cp = name_out; const char *const end = name_out + name_out_len; /* Normally, names are a series of length prefixed strings terminated */ /* with a length of 0 (the lengths are u8's < 63). */ /* However, the length can start with a pair of 1 bits and that */ /* means that the next 14 bits are a pointer within the current */ /* packet. */ for (;;) { u8 label_len; if (j >= length) return -1; GET8(label_len); if (!label_len) break; if (label_len & 0xc0) { u8 ptr_low; GET8(ptr_low); if (name_end < 0) name_end = j; j = (((int)label_len & 0x3f) << 8) + ptr_low; /* Make sure that the target offset is in-bounds. */ if (j < 0 || j >= length) return -1; /* If we've jumped more times than there are characters in the * message, we must have a loop. */ if (++ptr_count > length) return -1; continue; } if (label_len > 63) return -1; if (cp != name_out) { if (cp + 1 >= end) return -1; *cp++ = '.'; } if (cp + label_len >= end) return -1; memcpy(cp, packet + j, label_len); cp += label_len; j += label_len; } if (cp >= end) return -1; *cp = '\0'; if (name_end < 0) *idx = j; else *idx = name_end; return 0; err: return -1; } /* parses a raw request from a nameserver */ static int reply_parse(struct evdns_base *base, u8 *packet, int length) { int j = 0, k = 0; /* index into packet */ u16 _t; /* used by the macros */ u32 _t32; /* used by the macros */ char tmp_name[256], cmp_name[256]; /* used by the macros */ int name_matches = 0; u16 trans_id, questions, answers, authority, additional, datalength; u16 flags = 0; u32 ttl, ttl_r = 0xffffffff; struct reply reply; struct request *req = NULL; unsigned int i; ASSERT_LOCKED(base); GET16(trans_id); GET16(flags); GET16(questions); GET16(answers); GET16(authority); GET16(additional); (void) authority; /* suppress "unused variable" warnings. */ (void) additional; /* suppress "unused variable" warnings. */ req = request_find_from_trans_id(base, trans_id); if (!req) return -1; EVUTIL_ASSERT(req->base == base); memset(&reply, 0, sizeof(reply)); /* If it's not an answer, it doesn't correspond to any request. */ if (!(flags & 0x8000)) return -1; /* must be an answer */ if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) { /* there was an error and it's not NXDOMAIN */ goto err; } /* if (!answers) return; */ /* must have an answer of some form */ /* This macro skips a name in the DNS reply. */ #define SKIP_NAME \ do { tmp_name[0] = '\0'; \ if (name_parse(packet, length, &j, tmp_name, \ sizeof(tmp_name))<0) \ goto err; \ } while (0) #define TEST_NAME \ do { tmp_name[0] = '\0'; \ cmp_name[0] = '\0'; \ k = j; \ if (name_parse(packet, length, &j, tmp_name, \ sizeof(tmp_name))<0) \ goto err; \ if (name_parse(req->request, req->request_len, &k, \ cmp_name, sizeof(cmp_name))<0) \ goto err; \ if (base->global_randomize_case) { \ if (strcmp(tmp_name, cmp_name) == 0) \ name_matches = 1; \ } else { \ if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) \ name_matches = 1; \ } \ } while (0) reply.type = req->request_type; /* skip over each question in the reply */ for (i = 0; i < questions; ++i) { /* the question looks like * <label:name><u16:type><u16:class> */ TEST_NAME; j += 4; if (j > length) goto err; } if (!name_matches) goto err; /* now we have the answer section which looks like * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...> */ for (i = 0; i < answers; ++i) { u16 type, class; SKIP_NAME; GET16(type); GET16(class); GET32(ttl); GET16(datalength); if (type == TYPE_A && class == CLASS_INET) { int addrcount, addrtocopy; if (req->request_type != TYPE_A) { j += datalength; continue; } if ((datalength & 3) != 0) /* not an even number of As. */ goto err; addrcount = datalength >> 2; addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); ttl_r = MIN(ttl_r, ttl); /* we only bother with the first four addresses. */ if (j + 4*addrtocopy > length) goto err; memcpy(&reply.data.a.addresses[reply.data.a.addrcount], packet + j, 4*addrtocopy); j += 4*addrtocopy; reply.data.a.addrcount += addrtocopy; reply.have_answer = 1; if (reply.data.a.addrcount == MAX_V4_ADDRS) break; } else if (type == TYPE_PTR && class == CLASS_INET) { if (req->request_type != TYPE_PTR) { j += datalength; continue; } if (name_parse(packet, length, &j, reply.data.ptr.name, sizeof(reply.data.ptr.name))<0) goto err; ttl_r = MIN(ttl_r, ttl); reply.have_answer = 1; break; } else if (type == TYPE_CNAME) { char cname[HOST_NAME_MAX]; if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) { j += datalength; continue; } if (name_parse(packet, length, &j, cname, sizeof(cname))<0) goto err; *req->put_cname_in_ptr = mm_strdup(cname); } else if (type == TYPE_AAAA && class == CLASS_INET) { int addrcount, addrtocopy; if (req->request_type != TYPE_AAAA) { j += datalength; continue; } if ((datalength & 15) != 0) /* not an even number of AAAAs. */ goto err; addrcount = datalength >> 4; /* each address is 16 bytes long */ addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); ttl_r = MIN(ttl_r, ttl); /* we only bother with the first four addresses. */ if (j + 16*addrtocopy > length) goto err; memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], packet + j, 16*addrtocopy); reply.data.aaaa.addrcount += addrtocopy; j += 16*addrtocopy; reply.have_answer = 1; if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break; } else { /* skip over any other type of resource */ j += datalength; } } if (!reply.have_answer) { for (i = 0; i < authority; ++i) { u16 type, class; SKIP_NAME; GET16(type); GET16(class); GET32(ttl); GET16(datalength); if (type == TYPE_SOA && class == CLASS_INET) { u32 serial, refresh, retry, expire, minimum; SKIP_NAME; SKIP_NAME; GET32(serial); GET32(refresh); GET32(retry); GET32(expire); GET32(minimum); (void)expire; (void)retry; (void)refresh; (void)serial; ttl_r = MIN(ttl_r, ttl); ttl_r = MIN(ttl_r, minimum); } else { /* skip over any other type of resource */ j += datalength; } } } if (ttl_r == 0xffffffff) ttl_r = 0; reply_handle(req, flags, ttl_r, &reply); return 0; err: if (req) reply_handle(req, flags, 0, NULL); return -1; } /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ /* callback. */ static int request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen) { int j = 0; /* index into packet */ u16 _t; /* used by the macros */ char tmp_name[256]; /* used by the macros */ int i; u16 trans_id, flags, questions, answers, authority, additional; struct server_request *server_req = NULL; ASSERT_LOCKED(port); /* Get the header fields */ GET16(trans_id); GET16(flags); GET16(questions); GET16(answers); GET16(authority); GET16(additional); (void)answers; (void)additional; (void)authority; if (flags & 0x8000) return -1; /* Must not be an answer. */ flags &= 0x0110; /* Only RD and CD get preserved. */ server_req = mm_malloc(sizeof(struct server_request)); if (server_req == NULL) return -1; memset(server_req, 0, sizeof(struct server_request)); server_req->trans_id = trans_id; memcpy(&server_req->addr, addr, addrlen); server_req->addrlen = addrlen; server_req->base.flags = flags; server_req->base.nquestions = 0; server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions); if (server_req->base.questions == NULL) goto err; for (i = 0; i < questions; ++i) { u16 type, class; struct evdns_server_question *q; int namelen; if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0) goto err; GET16(type); GET16(class); namelen = (int)strlen(tmp_name); q = mm_malloc(sizeof(struct evdns_server_question) + namelen); if (!q) goto err; q->type = type; q->dns_question_class = class; memcpy(q->name, tmp_name, namelen+1); server_req->base.questions[server_req->base.nquestions++] = q; } /* Ignore answers, authority, and additional. */ server_req->port = port; port->refcnt++; /* Only standard queries are supported. */ if (flags & 0x7800) { evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); return -1; } port->user_callback(&(server_req->base), port->user_data); return 0; err: if (server_req) { if (server_req->base.questions) { for (i = 0; i < server_req->base.nquestions; ++i) mm_free(server_req->base.questions[i]); mm_free(server_req->base.questions); } mm_free(server_req); } return -1; #undef SKIP_NAME #undef GET32 #undef GET16 #undef GET8 } void evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void)) { } void evdns_set_random_bytes_fn(void (*fn)(char *, size_t)) { } /* Try to choose a strong transaction id which isn't already in flight */ static u16 transaction_id_pick(struct evdns_base *base) { ASSERT_LOCKED(base); for (;;) { u16 trans_id; evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id)); if (trans_id == 0xffff) continue; /* now check to see if that id is already inflight */ if (request_find_from_trans_id(base, trans_id) == NULL) return trans_id; } } /* choose a namesever to use. This function will try to ignore */ /* nameservers which we think are down and load balance across the rest */ /* by updating the server_head global each time. */ static struct nameserver * nameserver_pick(struct evdns_base *base) { struct nameserver *started_at = base->server_head, *picked; ASSERT_LOCKED(base); if (!base->server_head) return NULL; /* if we don't have any good nameservers then there's no */ /* point in trying to find one. */ if (!base->global_good_nameservers) { base->server_head = base->server_head->next; return base->server_head; } /* remember that nameservers are in a circular list */ for (;;) { if (base->server_head->state) { /* we think this server is currently good */ picked = base->server_head; base->server_head = base->server_head->next; return picked; } base->server_head = base->server_head->next; if (base->server_head == started_at) { /* all the nameservers seem to be down */ /* so we just return this one and hope for the */ /* best */ EVUTIL_ASSERT(base->global_good_nameservers == 0); picked = base->server_head; base->server_head = base->server_head->next; return picked; } } } /* this is called when a namesever socket is ready for reading */ static void nameserver_read(struct nameserver *ns) { struct sockaddr_storage ss; ev_socklen_t addrlen = sizeof(ss); u8 packet[1500]; char addrbuf[128]; ASSERT_LOCKED(ns->base); for (;;) { const int r = recvfrom(ns->socket, (void*)packet, sizeof(packet), 0, (struct sockaddr*)&ss, &addrlen); if (r < 0) { int err = evutil_socket_geterror(ns->socket); if (EVUTIL_ERR_RW_RETRIABLE(err)) return; nameserver_failed(ns, evutil_socket_error_to_string(err)); return; } if (evutil_sockaddr_cmp((struct sockaddr*)&ss, (struct sockaddr*)&ns->address, 0)) { log(EVDNS_LOG_WARN, "Address mismatch on received " "DNS packet. Apparent source was %s", evutil_format_sockaddr_port( (struct sockaddr *)&ss, addrbuf, sizeof(addrbuf))); return; } ns->timedout = 0; reply_parse(ns->base, packet, r); } } /* Read a packet from a DNS client on a server port s, parse it, and */ /* act accordingly. */ static void server_port_read(struct evdns_server_port *s) { u8 packet[1500]; struct sockaddr_storage addr; ev_socklen_t addrlen; int r; ASSERT_LOCKED(s); for (;;) { addrlen = sizeof(struct sockaddr_storage); r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0, (struct sockaddr*) &addr, &addrlen); if (r < 0) { int err = evutil_socket_geterror(s->socket); if (EVUTIL_ERR_RW_RETRIABLE(err)) return; log(EVDNS_LOG_WARN, "Error %s (%d) while reading request.", evutil_socket_error_to_string(err), err); return; } request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); } } /* Try to write all pending replies on a given DNS server port. */ static void server_port_flush(struct evdns_server_port *port) { struct server_request *req = port->pending_replies; ASSERT_LOCKED(port); while (req) { int r = sendto(port->socket, req->response, (int)req->response_len, 0, (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); if (r < 0) { int err = evutil_socket_geterror(port->socket); if (EVUTIL_ERR_RW_RETRIABLE(err)) return; log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err); } if (server_request_free(req)) { /* we released the last reference to req->port. */ return; } else { EVUTIL_ASSERT(req != port->pending_replies); req = port->pending_replies; } } /* We have no more pending requests; stop listening for 'writeable' events. */ (void) event_del(&port->event); event_assign(&port->event, port->event_base, port->socket, EV_READ | EV_PERSIST, server_port_ready_callback, port); if (event_add(&port->event, NULL) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); /* ???? Do more? */ } } /* set if we are waiting for the ability to write to this server. */ /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ /* we stop these events. */ static void nameserver_write_waiting(struct nameserver *ns, char waiting) { ASSERT_LOCKED(ns->base); if (ns->write_waiting == waiting) return; ns->write_waiting = waiting; (void) event_del(&ns->event); event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, nameserver_ready_callback, ns); if (event_add(&ns->event, NULL) < 0) { char addrbuf[128]; log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", evutil_format_sockaddr_port( (struct sockaddr *)&ns->address, addrbuf, sizeof(addrbuf))); /* ???? Do more? */ } } /* a callback function. Called by libevent when the kernel says that */ /* a nameserver socket is ready for writing or reading */ static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) { struct nameserver *ns = (struct nameserver *) arg; (void)fd; EVDNS_LOCK(ns->base); if (events & EV_WRITE) { ns->choked = 0; if (!evdns_transmit(ns->base)) { nameserver_write_waiting(ns, 0); } } if (events & EV_READ) { nameserver_read(ns); } EVDNS_UNLOCK(ns->base); } /* a callback function. Called by libevent when the kernel says that */ /* a server socket is ready for writing or reading. */ static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg) { struct evdns_server_port *port = (struct evdns_server_port *) arg; (void) fd; EVDNS_LOCK(port); if (events & EV_WRITE) { port->choked = 0; server_port_flush(port); } if (events & EV_READ) { server_port_read(port); } EVDNS_UNLOCK(port); } /* This is an inefficient representation; only use it via the dnslabel_table_* * functions, so that is can be safely replaced with something smarter later. */ #define MAX_LABELS 128 /* Structures used to implement name compression */ struct dnslabel_entry { char *v; off_t pos; }; struct dnslabel_table { int n_labels; /* number of current entries */ /* map from name to position in message */ struct dnslabel_entry labels[MAX_LABELS]; }; /* Initialize dnslabel_table. */ static void dnslabel_table_init(struct dnslabel_table *table) { table->n_labels = 0; } /* Free all storage held by table, but not the table itself. */ static void dnslabel_clear(struct dnslabel_table *table) { int i; for (i = 0; i < table->n_labels; ++i) mm_free(table->labels[i].v); table->n_labels = 0; } /* return the position of the label in the current message, or -1 if the label */ /* hasn't been used yet. */ static int dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) { int i; for (i = 0; i < table->n_labels; ++i) { if (!strcmp(label, table->labels[i].v)) return table->labels[i].pos; } return -1; } /* remember that we've used the label at position pos */ static int dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) { char *v; int p; if (table->n_labels == MAX_LABELS) return (-1); v = mm_strdup(label); if (v == NULL) return (-1); p = table->n_labels++; table->labels[p].v = v; table->labels[p].pos = pos; return (0); } /* Converts a string to a length-prefixed set of DNS labels, starting */ /* at buf[j]. name and buf must not overlap. name_len should be the length */ /* of name. table is optional, and is used for compression. */ /* */ /* Input: abc.def */ /* Output: <3>abc<3>def<0> */ /* */ /* Returns the first index after the encoded name, or negative on error. */ /* -1 label was > 63 bytes */ /* -2 name too long to fit in buffer. */ /* */ static off_t dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, const char *name, const size_t name_len, struct dnslabel_table *table) { const char *end = name + name_len; int ref = 0; u16 _t; #define APPEND16(x) do { \ if (j + 2 > (off_t)buf_len) \ goto overflow; \ _t = htons(x); \ memcpy(buf + j, &_t, 2); \ j += 2; \ } while (0) #define APPEND32(x) do { \ if (j + 4 > (off_t)buf_len) \ goto overflow; \ _t32 = htonl(x); \ memcpy(buf + j, &_t32, 4); \ j += 4; \ } while (0) if (name_len > 255) return -2; for (;;) { const char *const start = name; if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { APPEND16(ref | 0xc000); return j; } name = strchr(name, '.'); if (!name) { const size_t label_len = end - start; if (label_len > 63) return -1; if ((size_t)(j+label_len+1) > buf_len) return -2; if (table) dnslabel_table_add(table, start, j); buf[j++] = (ev_uint8_t)label_len; memcpy(buf + j, start, label_len); j += (int) label_len; break; } else { /* append length of the label. */ const size_t label_len = name - start; if (label_len > 63) return -1; if ((size_t)(j+label_len+1) > buf_len) return -2; if (table) dnslabel_table_add(table, start, j); buf[j++] = (ev_uint8_t)label_len; memcpy(buf + j, start, label_len); j += (int) label_len; /* hop over the '.' */ name++; } } /* the labels must be terminated by a 0. */ /* It's possible that the name ended in a . */ /* in which case the zero is already there */ if (!j || buf[j-1]) buf[j++] = 0; return j; overflow: return (-2); } /* Finds the length of a dns request for a DNS name of the given */ /* length. The actual request may be smaller than the value returned */ /* here */ static size_t evdns_request_len(const size_t name_len) { return 96 + /* length of the DNS standard header */ name_len + 2 + 4; /* space for the resource type */ } /* build a dns request packet into buf. buf should be at least as long */ /* as evdns_request_len told you it should be. */ /* */ /* Returns the amount of space used. Negative on error. */ static int evdns_request_data_build(const char *const name, const size_t name_len, const u16 trans_id, const u16 type, const u16 class, u8 *const buf, size_t buf_len) { off_t j = 0; /* current offset into buf */ u16 _t; /* used by the macros */ APPEND16(trans_id); APPEND16(0x0100); /* standard query, recusion needed */ APPEND16(1); /* one question */ APPEND16(0); /* no answers */ APPEND16(0); /* no authority */ APPEND16(0); /* no additional */ j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); if (j < 0) { return (int)j; } APPEND16(type); APPEND16(class); return (int)j; overflow: return (-1); } /* exported function */ struct evdns_server_port * evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) { struct evdns_server_port *port; if (flags) return NULL; /* flags not yet implemented */ if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) return NULL; memset(port, 0, sizeof(struct evdns_server_port)); port->socket = socket; port->refcnt = 1; port->choked = 0; port->closing = 0; port->user_callback = cb; port->user_data = user_data; port->pending_replies = NULL; port->event_base = base; event_assign(&port->event, port->event_base, port->socket, EV_READ | EV_PERSIST, server_port_ready_callback, port); if (event_add(&port->event, NULL) < 0) { mm_free(port); return NULL; } EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); return port; } struct evdns_server_port * evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data) { return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data); } /* exported function */ void evdns_close_server_port(struct evdns_server_port *port) { EVDNS_LOCK(port); if (--port->refcnt == 0) { EVDNS_UNLOCK(port); server_port_free(port); } else { port->closing = 1; } } /* exported function */ int 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) { struct server_request *req = TO_SERVER_REQUEST(_req); struct server_reply_item **itemp, *item; int *countp; int result = -1; EVDNS_LOCK(req->port); if (req->response) /* have we already answered? */ goto done; switch (section) { case EVDNS_ANSWER_SECTION: itemp = &req->answer; countp = &req->n_answer; break; case EVDNS_AUTHORITY_SECTION: itemp = &req->authority; countp = &req->n_authority; break; case EVDNS_ADDITIONAL_SECTION: itemp = &req->additional; countp = &req->n_additional; break; default: goto done; } while (*itemp) { itemp = &((*itemp)->next); } item = mm_malloc(sizeof(struct server_reply_item)); if (!item) goto done; item->next = NULL; if (!(item->name = mm_strdup(name))) { mm_free(item); goto done; } item->type = type; item->dns_question_class = class; item->ttl = ttl; item->is_name = is_name != 0; item->datalen = 0; item->data = NULL; if (data) { if (item->is_name) { if (!(item->data = mm_strdup(data))) { mm_free(item->name); mm_free(item); goto done; } item->datalen = (u16)-1; } else { if (!(item->data = mm_malloc(datalen))) { mm_free(item->name); mm_free(item); goto done; } item->datalen = datalen; memcpy(item->data, data, datalen); } } *itemp = item; ++(*countp); result = 0; done: EVDNS_UNLOCK(req->port); return result; } /* exported function */ int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) { return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, ttl, n*4, 0, addrs); } /* exported function */ int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl) { return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, ttl, n*16, 0, addrs); } /* exported function */ int evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) { u32 a; char buf[32]; if (in && inaddr_name) return -1; else if (!in && !inaddr_name) return -1; if (in) { a = ntohl(in->s_addr); evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", (int)(u8)((a )&0xff), (int)(u8)((a>>8 )&0xff), (int)(u8)((a>>16)&0xff), (int)(u8)((a>>24)&0xff)); inaddr_name = buf; } return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, ttl, -1, 1, hostname); } /* exported function */ int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) { return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, ttl, -1, 1, cname); } /* exported function */ void evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags) { struct server_request *req = TO_SERVER_REQUEST(exreq); req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD); req->base.flags |= flags; } static int evdns_server_request_format_response(struct server_request *req, int err) { unsigned char buf[1500]; size_t buf_len = sizeof(buf); off_t j = 0, r; u16 _t; u32 _t32; int i; u16 flags; struct dnslabel_table table; if (err < 0 || err > 15) return -1; /* Set response bit and error code; copy OPCODE and RD fields from * question; copy RA and AA if set by caller. */ flags = req->base.flags; flags |= (0x8000 | err); dnslabel_table_init(&table); APPEND16(req->trans_id); APPEND16(flags); APPEND16(req->base.nquestions); APPEND16(req->n_answer); APPEND16(req->n_authority); APPEND16(req->n_additional); /* Add questions. */ for (i=0; i < req->base.nquestions; ++i) { const char *s = req->base.questions[i]->name; j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); if (j < 0) { dnslabel_clear(&table); return (int) j; } APPEND16(req->base.questions[i]->type); APPEND16(req->base.questions[i]->dns_question_class); } /* Add answer, authority, and additional sections. */ for (i=0; i<3; ++i) { struct server_reply_item *item; if (i==0) item = req->answer; else if (i==1) item = req->authority; else item = req->additional; while (item) { r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); if (r < 0) goto overflow; j = r; APPEND16(item->type); APPEND16(item->dns_question_class); APPEND32(item->ttl); if (item->is_name) { off_t len_idx = j, name_start; j += 2; name_start = j; r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); if (r < 0) goto overflow; j = r; _t = htons( (short) (j-name_start) ); memcpy(buf+len_idx, &_t, 2); } else { APPEND16(item->datalen); if (j+item->datalen > (off_t)buf_len) goto overflow; memcpy(buf+j, item->data, item->datalen); j += item->datalen; } item = item->next; } } if (j > 512) { overflow: j = 512; buf[2] |= 0x02; /* set the truncated bit. */ } req->response_len = j; if (!(req->response = mm_malloc(req->response_len))) { server_request_free_answers(req); dnslabel_clear(&table); return (-1); } memcpy(req->response, buf, req->response_len); server_request_free_answers(req); dnslabel_clear(&table); return (0); } /* exported function */ int evdns_server_request_respond(struct evdns_server_request *_req, int err) { struct server_request *req = TO_SERVER_REQUEST(_req); struct evdns_server_port *port = req->port; int r = -1; EVDNS_LOCK(port); if (!req->response) { if ((r = evdns_server_request_format_response(req, err))<0) goto done; } r = sendto(port->socket, req->response, (int)req->response_len, 0, (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen); if (r<0) { int sock_err = evutil_socket_geterror(port->socket); if (EVUTIL_ERR_RW_RETRIABLE(sock_err)) goto done; if (port->pending_replies) { req->prev_pending = port->pending_replies->prev_pending; req->next_pending = port->pending_replies; req->prev_pending->next_pending = req->next_pending->prev_pending = req; } else { req->prev_pending = req->next_pending = req; port->pending_replies = req; port->choked = 1; (void) event_del(&port->event); event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); if (event_add(&port->event, NULL) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); } } r = 1; goto done; } if (server_request_free(req)) { r = 0; goto done; } if (port->pending_replies) server_port_flush(port); r = 0; done: EVDNS_UNLOCK(port); return r; } /* Free all storage held by RRs in req. */ static void server_request_free_answers(struct server_request *req) { struct server_reply_item *victim, *next, **list; int i; for (i = 0; i < 3; ++i) { if (i==0) list = &req->answer; else if (i==1) list = &req->authority; else list = &req->additional; victim = *list; while (victim) { next = victim->next; mm_free(victim->name); if (victim->data) mm_free(victim->data); mm_free(victim); victim = next; } *list = NULL; } } /* Free all storage held by req, and remove links to it. */ /* return true iff we just wound up freeing the server_port. */ static int server_request_free(struct server_request *req) { int i, rc=1, lock=0; if (req->base.questions) { for (i = 0; i < req->base.nquestions; ++i) mm_free(req->base.questions[i]); mm_free(req->base.questions); } if (req->port) { EVDNS_LOCK(req->port); lock=1; if (req->port->pending_replies == req) { if (req->next_pending && req->next_pending != req) req->port->pending_replies = req->next_pending; else req->port->pending_replies = NULL; } rc = --req->port->refcnt; } if (req->response) { mm_free(req->response); } server_request_free_answers(req); if (req->next_pending && req->next_pending != req) { req->next_pending->prev_pending = req->prev_pending; req->prev_pending->next_pending = req->next_pending; } if (rc == 0) { EVDNS_UNLOCK(req->port); /* ????? nickm */ server_port_free(req->port); mm_free(req); return (1); } if (lock) EVDNS_UNLOCK(req->port); mm_free(req); return (0); } /* Free all storage held by an evdns_server_port. Only called when */ static void server_port_free(struct evdns_server_port *port) { EVUTIL_ASSERT(port); EVUTIL_ASSERT(!port->refcnt); EVUTIL_ASSERT(!port->pending_replies); if (port->socket > 0) { evutil_closesocket(port->socket); port->socket = -1; } (void) event_del(&port->event); event_debug_unassign(&port->event); EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE); mm_free(port); } /* exported function */ int evdns_server_request_drop(struct evdns_server_request *_req) { struct server_request *req = TO_SERVER_REQUEST(_req); server_request_free(req); return 0; } /* exported function */ int evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len) { struct server_request *req = TO_SERVER_REQUEST(_req); if (addr_len < (int)req->addrlen) return -1; memcpy(sa, &(req->addr), req->addrlen); return req->addrlen; } #undef APPEND16 #undef APPEND32 /* this is a libevent callback function which is called when a request */ /* has timed out. */ static void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) { struct request *const req = (struct request *) arg; #ifndef _EVENT_DISABLE_THREAD_SUPPORT struct evdns_base *base = req->base; #endif (void) fd; (void) events; log(EVDNS_LOG_DEBUG, "Request %p timed out", arg); EVDNS_LOCK(base); req->ns->timedout++; if (req->ns->timedout > req->base->global_max_nameserver_timeout) { req->ns->timedout = 0; nameserver_failed(req->ns, "request timed out."); } if (req->tx_count >= req->base->global_max_retransmits) { /* this request has failed */ reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL); request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1); } else { /* retransmit it */ (void) evtimer_del(&req->timeout_event); evdns_request_transmit(req); } EVDNS_UNLOCK(base); } /* try to send a request to a given server. */ /* */ /* return: */ /* 0 ok */ /* 1 temporary failure */ /* 2 other failure */ static int evdns_request_transmit_to(struct request *req, struct nameserver *server) { int r; ASSERT_LOCKED(req->base); ASSERT_VALID_REQUEST(req); r = sendto(server->socket, (void*)req->request, req->request_len, 0, (struct sockaddr *)&server->address, server->addrlen); if (r < 0) { int err = evutil_socket_geterror(server->socket); if (EVUTIL_ERR_RW_RETRIABLE(err)) return 1; nameserver_failed(req->ns, evutil_socket_error_to_string(err)); return 2; } else if (r != (int)req->request_len) { return 1; /* short write */ } else { return 0; } } /* try to send a request, updating the fields of the request */ /* as needed */ /* */ /* return: */ /* 0 ok */ /* 1 failed */ static int evdns_request_transmit(struct request *req) { int retcode = 0, r; ASSERT_LOCKED(req->base); ASSERT_VALID_REQUEST(req); /* if we fail to send this packet then this flag marks it */ /* for evdns_transmit */ req->transmit_me = 1; EVUTIL_ASSERT(req->trans_id != 0xffff); if (req->ns->choked) { /* don't bother trying to write to a socket */ /* which we have had EAGAIN from */ return 1; } r = evdns_request_transmit_to(req, req->ns); switch (r) { case 1: /* temp failure */ req->ns->choked = 1; nameserver_write_waiting(req->ns, 1); return 1; case 2: /* failed to transmit the request entirely. */ retcode = 1; /* fall through: we'll set a timeout, which will time out, * and make us retransmit the request anyway. */ default: /* all ok */ log(EVDNS_LOG_DEBUG, "Setting timeout for request %p", req); if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding timer for request %p", req); /* ???? Do more? */ } req->tx_count++; req->transmit_me = 0; return retcode; } } static void nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { struct nameserver *const ns = (struct nameserver *) arg; (void) type; (void) count; (void) ttl; (void) addresses; if (result == DNS_ERR_CANCEL) { /* We canceled this request because the nameserver came up * for some other reason. Do not change our opinion about * the nameserver. */ return; } EVDNS_LOCK(ns->base); ns->probe_request = NULL; if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { /* this is a good reply */ nameserver_up(ns); } else { nameserver_probe_failed(ns); } EVDNS_UNLOCK(ns->base); } static void nameserver_send_probe(struct nameserver *const ns) { struct evdns_request *handle; struct request *req; char addrbuf[128]; /* here we need to send a probe to a given nameserver */ /* in the hope that it is up now. */ ASSERT_LOCKED(ns->base); log(EVDNS_LOG_DEBUG, "Sending probe to %s", evutil_format_sockaddr_port( (struct sockaddr *)&ns->address, addrbuf, sizeof(addrbuf))); handle = mm_calloc(1, sizeof(*handle)); if (!handle) return; req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns); if (!req) return; ns->probe_request = handle; /* we force this into the inflight queue no matter what */ request_trans_id_set(req, transaction_id_pick(ns->base)); req->ns = ns; request_submit(req); } /* returns: */ /* 0 didn't try to transmit anything */ /* 1 tried to transmit something */ static int evdns_transmit(struct evdns_base *base) { char did_try_to_transmit = 0; int i; ASSERT_LOCKED(base); for (i = 0; i < base->n_req_heads; ++i) { if (base->req_heads[i]) { struct request *const started_at = base->req_heads[i], *req = started_at; /* first transmit all the requests which are currently waiting */ do { if (req->transmit_me) { did_try_to_transmit = 1; evdns_request_transmit(req); } req = req->next; } while (req != started_at); } } return did_try_to_transmit; } /* exported function */ int evdns_base_count_nameservers(struct evdns_base *base) { const struct nameserver *server; int n = 0; EVDNS_LOCK(base); server = base->server_head; if (!server) goto done; do { ++n; server = server->next; } while (server != base->server_head); done: EVDNS_UNLOCK(base); return n; } int evdns_count_nameservers(void) { return evdns_base_count_nameservers(current_base); } /* exported function */ int evdns_base_clear_nameservers_and_suspend(struct evdns_base *base) { struct nameserver *server, *started_at; int i; EVDNS_LOCK(base); server = base->server_head; started_at = base->server_head; if (!server) { EVDNS_UNLOCK(base); return 0; } while (1) { struct nameserver *next = server->next; (void) event_del(&server->event); if (evtimer_initialized(&server->timeout_event)) (void) evtimer_del(&server->timeout_event); if (server->probe_request) { evdns_cancel_request(server->base, server->probe_request); server->probe_request = NULL; } if (server->socket >= 0) evutil_closesocket(server->socket); mm_free(server); if (next == started_at) break; server = next; } base->server_head = NULL; base->global_good_nameservers = 0; for (i = 0; i < base->n_req_heads; ++i) { struct request *req, *req_started_at; req = req_started_at = base->req_heads[i]; while (req) { struct request *next = req->next; req->tx_count = req->reissue_count = 0; req->ns = NULL; /* ???? What to do about searches? */ (void) evtimer_del(&req->timeout_event); req->trans_id = 0; req->transmit_me = 0; base->global_requests_waiting++; evdns_request_insert(req, &base->req_waiting_head); /* We want to insert these suspended elements at the front of * the waiting queue, since they were pending before any of * the waiting entries were added. This is a circular list, * so we can just shift the start back by one.*/ base->req_waiting_head = base->req_waiting_head->prev; if (next == req_started_at) break; req = next; } base->req_heads[i] = NULL; } base->global_requests_inflight = 0; EVDNS_UNLOCK(base); return 0; } int evdns_clear_nameservers_and_suspend(void) { return evdns_base_clear_nameservers_and_suspend(current_base); } /* exported function */ int evdns_base_resume(struct evdns_base *base) { EVDNS_LOCK(base); evdns_requests_pump_waiting_queue(base); EVDNS_UNLOCK(base); return 0; } int evdns_resume(void) { return evdns_base_resume(current_base); } static int _evdns_nameserver_add_impl(struct evdns_base *base, const struct sockaddr *address, int addrlen) { /* first check to see if we already have this nameserver */ const struct nameserver *server = base->server_head, *const started_at = base->server_head; struct nameserver *ns; int err = 0; char addrbuf[128]; ASSERT_LOCKED(base); if (server) { do { if (!evutil_sockaddr_cmp((struct sockaddr*)&server->address, address, 1)) return 3; server = server->next; } while (server != started_at); } if (addrlen > (int)sizeof(ns->address)) { log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); return 2; } ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); if (!ns) return -1; memset(ns, 0, sizeof(struct nameserver)); ns->base = base; evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns); ns->socket = socket(address->sa_family, SOCK_DGRAM, 0); if (ns->socket < 0) { err = 1; goto out1; } evutil_make_socket_closeonexec(ns->socket); evutil_make_socket_nonblocking(ns->socket); if (base->global_outgoing_addrlen && !evutil_sockaddr_is_loopback(address)) { if (bind(ns->socket, (struct sockaddr*)&base->global_outgoing_address, base->global_outgoing_addrlen) < 0) { log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address"); err = 2; goto out2; } } memcpy(&ns->address, address, addrlen); ns->addrlen = addrlen; ns->state = 1; event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); if (event_add(&ns->event, NULL) < 0) { err = 2; goto out2; } log(EVDNS_LOG_DEBUG, "Added nameserver %s", evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf))); /* insert this nameserver into the list of them */ if (!base->server_head) { ns->next = ns->prev = ns; base->server_head = ns; } else { ns->next = base->server_head->next; ns->prev = base->server_head; base->server_head->next = ns; ns->next->prev = ns; } base->global_good_nameservers++; return 0; out2: evutil_closesocket(ns->socket); out1: event_debug_unassign(&ns->event); mm_free(ns); log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", evutil_format_sockaddr_port(address, addrbuf, sizeof(addrbuf)), err); return err; } /* exported function */ int evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address) { struct sockaddr_in sin; int res; sin.sin_addr.s_addr = address; sin.sin_port = htons(53); sin.sin_family = AF_INET; EVDNS_LOCK(base); res = _evdns_nameserver_add_impl(base, (struct sockaddr*)&sin, sizeof(sin)); EVDNS_UNLOCK(base); return res; } int evdns_nameserver_add(unsigned long int address) { if (!current_base) current_base = evdns_base_new(NULL, 0); return evdns_base_nameserver_add(current_base, address); } static void sockaddr_setport(struct sockaddr *sa, ev_uint16_t port) { if (sa->sa_family == AF_INET) { ((struct sockaddr_in *)sa)->sin_port = htons(port); } else if (sa->sa_family == AF_INET6) { ((struct sockaddr_in6 *)sa)->sin6_port = htons(port); } } static ev_uint16_t sockaddr_getport(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return ntohs(((struct sockaddr_in *)sa)->sin_port); } else if (sa->sa_family == AF_INET6) { return ntohs(((struct sockaddr_in6 *)sa)->sin6_port); } else { return 0; } } /* exported function */ int evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) { struct sockaddr_storage ss; struct sockaddr *sa; int len = sizeof(ss); int res; if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss, &len)) { log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s", ip_as_string); return 4; } sa = (struct sockaddr *) &ss; if (sockaddr_getport(sa) == 0) sockaddr_setport(sa, 53); EVDNS_LOCK(base); res = _evdns_nameserver_add_impl(base, sa, len); EVDNS_UNLOCK(base); return res; } int evdns_nameserver_ip_add(const char *ip_as_string) { if (!current_base) current_base = evdns_base_new(NULL, 0); return evdns_base_nameserver_ip_add(current_base, ip_as_string); } int evdns_base_nameserver_sockaddr_add(struct evdns_base *base, const struct sockaddr *sa, ev_socklen_t len, unsigned flags) { int res; EVUTIL_ASSERT(base); EVDNS_LOCK(base); res = _evdns_nameserver_add_impl(base, sa, len); EVDNS_UNLOCK(base); return res; } /* remove from the queue */ static void evdns_request_remove(struct request *req, struct request **head) { ASSERT_LOCKED(req->base); ASSERT_VALID_REQUEST(req); #if 0 { struct request *ptr; int found = 0; EVUTIL_ASSERT(*head != NULL); ptr = *head; do { if (ptr == req) { found = 1; break; } ptr = ptr->next; } while (ptr != *head); EVUTIL_ASSERT(found); EVUTIL_ASSERT(req->next); } #endif if (req->next == req) { /* only item in the list */ *head = NULL; } else { req->next->prev = req->prev; req->prev->next = req->next; if (*head == req) *head = req->next; } req->next = req->prev = NULL; } /* insert into the tail of the queue */ static void evdns_request_insert(struct request *req, struct request **head) { ASSERT_LOCKED(req->base); ASSERT_VALID_REQUEST(req); if (!*head) { *head = req; req->next = req->prev = req; return; } req->prev = (*head)->prev; req->prev->next = req; req->next = *head; (*head)->prev = req; } static int string_num_dots(const char *s) { int count = 0; while ((s = strchr(s, '.'))) { s++; count++; } return count; } static struct request * request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *user_ptr) { const char issuing_now = (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0; const size_t name_len = strlen(name); const size_t request_max_len = evdns_request_len(name_len); const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff; /* the request data is alloced in a single block with the header */ struct request *const req = mm_malloc(sizeof(struct request) + request_max_len); int rlen; char namebuf[256]; (void) flags; ASSERT_LOCKED(base); if (!req) return NULL; if (name_len >= sizeof(namebuf)) { mm_free(req); return NULL; } memset(req, 0, sizeof(struct request)); req->base = base; evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req); if (base->global_randomize_case) { unsigned i; char randbits[(sizeof(namebuf)+7)/8]; strlcpy(namebuf, name, sizeof(namebuf)); evutil_secure_rng_get_bytes(randbits, (name_len+7)/8); for (i = 0; i < name_len; ++i) { if (EVUTIL_ISALPHA(namebuf[i])) { if ((randbits[i >> 3] & (1<<(i & 7)))) namebuf[i] |= 0x20; else namebuf[i] &= ~0x20; } } name = namebuf; } /* request data lives just after the header */ req->request = ((u8 *) req) + sizeof(struct request); /* denotes that the request data shouldn't be free()ed */ req->request_appended = 1; rlen = evdns_request_data_build(name, name_len, trans_id, type, CLASS_INET, req->request, request_max_len); if (rlen < 0) goto err1; req->request_len = rlen; req->trans_id = trans_id; req->tx_count = 0; req->request_type = type; req->user_pointer = user_ptr; req->user_callback = callback; req->ns = issuing_now ? nameserver_pick(base) : NULL; req->next = req->prev = NULL; req->handle = handle; if (handle) { handle->current_req = req; handle->base = base; } return req; err1: mm_free(req); return NULL; } static void request_submit(struct request *const req) { struct evdns_base *base = req->base; ASSERT_LOCKED(base); ASSERT_VALID_REQUEST(req); if (req->ns) { /* if it has a nameserver assigned then this is going */ /* straight into the inflight queue */ evdns_request_insert(req, &REQ_HEAD(base, req->trans_id)); base->global_requests_inflight++; evdns_request_transmit(req); } else { evdns_request_insert(req, &base->req_waiting_head); base->global_requests_waiting++; } } /* exported function */ void evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle) { struct request *req; if (!handle->current_req) return; if (!base) { /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */ base = handle->base; if (!base) base = handle->current_req->base; } EVDNS_LOCK(base); if (handle->pending_cb) { EVDNS_UNLOCK(base); return; } req = handle->current_req; ASSERT_VALID_REQUEST(req); reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL); if (req->ns) { /* remove from inflight queue */ request_finished(req, &REQ_HEAD(base, req->trans_id), 1); } else { /* remove from global_waiting head */ request_finished(req, &base->req_waiting_head, 1); } EVDNS_UNLOCK(base); } /* exported function */ struct evdns_request * evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr) { struct evdns_request *handle; struct request *req; log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); handle = mm_calloc(1, sizeof(*handle)); if (handle == NULL) return NULL; EVDNS_LOCK(base); if (flags & DNS_QUERY_NO_SEARCH) { req = request_new(base, handle, TYPE_A, name, flags, callback, ptr); if (req) request_submit(req); } else { search_request_new(base, handle, TYPE_A, name, flags, callback, ptr); } if (handle->current_req == NULL) { mm_free(handle); handle = NULL; } EVDNS_UNLOCK(base); return handle; } int evdns_resolve_ipv4(const char *name, int flags, evdns_callback_type callback, void *ptr) { return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr) ? 0 : -1; } /* exported function */ struct evdns_request * evdns_base_resolve_ipv6(struct evdns_base *base, const char *name, int flags, evdns_callback_type callback, void *ptr) { struct evdns_request *handle; struct request *req; log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); handle = mm_calloc(1, sizeof(*handle)); if (handle == NULL) return NULL; EVDNS_LOCK(base); if (flags & DNS_QUERY_NO_SEARCH) { req = request_new(base, handle, TYPE_AAAA, name, flags, callback, ptr); if (req) request_submit(req); } else { search_request_new(base, handle, TYPE_AAAA, name, flags, callback, ptr); } if (handle->current_req == NULL) { mm_free(handle); handle = NULL; } EVDNS_UNLOCK(base); return handle; } int evdns_resolve_ipv6(const char *name, int flags, evdns_callback_type callback, void *ptr) { return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr) ? 0 : -1; } struct evdns_request * evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { char buf[32]; struct evdns_request *handle; struct request *req; u32 a; EVUTIL_ASSERT(in); a = ntohl(in->s_addr); evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", (int)(u8)((a )&0xff), (int)(u8)((a>>8 )&0xff), (int)(u8)((a>>16)&0xff), (int)(u8)((a>>24)&0xff)); handle = mm_calloc(1, sizeof(*handle)); if (handle == NULL) return NULL; log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); EVDNS_LOCK(base); req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); if (req) request_submit(req); if (handle->current_req == NULL) { mm_free(handle); handle = NULL; } EVDNS_UNLOCK(base); return (handle); } int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr) ? 0 : -1; } struct evdns_request * evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ char buf[73]; char *cp; struct evdns_request *handle; struct request *req; int i; EVUTIL_ASSERT(in); cp = buf; for (i=15; i >= 0; --i) { u8 byte = in->s6_addr[i]; *cp++ = "0123456789abcdef"[byte & 0x0f]; *cp++ = '.'; *cp++ = "0123456789abcdef"[byte >> 4]; *cp++ = '.'; } EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf)); memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); handle = mm_calloc(1, sizeof(*handle)); if (handle == NULL) return NULL; log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); EVDNS_LOCK(base); req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr); if (req) request_submit(req); if (handle->current_req == NULL) { mm_free(handle); handle = NULL; } EVDNS_UNLOCK(base); return (handle); } int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr) ? 0 : -1; } /* ================================================================= */ /* Search support */ /* */ /* the libc resolver has support for searching a number of domains */ /* to find a name. If nothing else then it takes the single domain */ /* from the gethostname() call. */ /* */ /* It can also be configured via the domain and search options in a */ /* resolv.conf. */ /* */ /* The ndots option controls how many dots it takes for the resolver */ /* to decide that a name is non-local and so try a raw lookup first. */ struct search_domain { int len; struct search_domain *next; /* the text string is appended to this structure */ }; struct search_state { int refcount; int ndots; int num_domains; struct search_domain *head; }; static void search_state_decref(struct search_state *const state) { if (!state) return; state->refcount--; if (!state->refcount) { struct search_domain *next, *dom; for (dom = state->head; dom; dom = next) { next = dom->next; mm_free(dom); } mm_free(state); } } static struct search_state * search_state_new(void) { struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); if (!state) return NULL; memset(state, 0, sizeof(struct search_state)); state->refcount = 1; state->ndots = 1; return state; } static void search_postfix_clear(struct evdns_base *base) { search_state_decref(base->global_search_state); base->global_search_state = search_state_new(); } /* exported function */ void evdns_base_search_clear(struct evdns_base *base) { EVDNS_LOCK(base); search_postfix_clear(base); EVDNS_UNLOCK(base); } void evdns_search_clear(void) { evdns_base_search_clear(current_base); } static void search_postfix_add(struct evdns_base *base, const char *domain) { size_t domain_len; struct search_domain *sdomain; while (domain[0] == '.') domain++; domain_len = strlen(domain); ASSERT_LOCKED(base); if (!base->global_search_state) base->global_search_state = search_state_new(); if (!base->global_search_state) return; base->global_search_state->num_domains++; sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); if (!sdomain) return; memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); sdomain->next = base->global_search_state->head; sdomain->len = (int) domain_len; base->global_search_state->head = sdomain; } /* reverse the order of members in the postfix list. This is needed because, */ /* when parsing resolv.conf we push elements in the wrong order */ static void search_reverse(struct evdns_base *base) { struct search_domain *cur, *prev = NULL, *next; ASSERT_LOCKED(base); cur = base->global_search_state->head; while (cur) { next = cur->next; cur->next = prev; prev = cur; cur = next; } base->global_search_state->head = prev; } /* exported function */ void evdns_base_search_add(struct evdns_base *base, const char *domain) { EVDNS_LOCK(base); search_postfix_add(base, domain); EVDNS_UNLOCK(base); } void evdns_search_add(const char *domain) { evdns_base_search_add(current_base, domain); } /* exported function */ void evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) { EVDNS_LOCK(base); if (!base->global_search_state) base->global_search_state = search_state_new(); if (base->global_search_state) base->global_search_state->ndots = ndots; EVDNS_UNLOCK(base); } void evdns_search_ndots_set(const int ndots) { evdns_base_search_ndots_set(current_base, ndots); } static void search_set_from_hostname(struct evdns_base *base) { char hostname[HOST_NAME_MAX + 1], *domainname; ASSERT_LOCKED(base); search_postfix_clear(base); if (gethostname(hostname, sizeof(hostname))) return; domainname = strchr(hostname, '.'); if (!domainname) return; search_postfix_add(base, domainname); } /* warning: returns malloced string */ static char * search_make_new(const struct search_state *const state, int n, const char *const base_name) { const size_t base_len = strlen(base_name); const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; struct search_domain *dom; for (dom = state->head; dom; dom = dom->next) { if (!n--) { /* this is the postfix we want */ /* the actual postfix string is kept at the end of the structure */ const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); const int postfix_len = dom->len; char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); if (!newname) return NULL; memcpy(newname, base_name, base_len); if (need_to_append_dot) newname[base_len] = '.'; memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); newname[base_len + need_to_append_dot + postfix_len] = 0; return newname; } } /* we ran off the end of the list and still didn't find the requested string */ EVUTIL_ASSERT(0); return NULL; /* unreachable; stops warnings in some compilers. */ } static struct request * search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg) { ASSERT_LOCKED(base); EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA); EVUTIL_ASSERT(handle->current_req == NULL); if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && base->global_search_state && base->global_search_state->num_domains) { /* we have some domains to search */ struct request *req; if (string_num_dots(name) >= base->global_search_state->ndots) { req = request_new(base, handle, type, name, flags, user_callback, user_arg); if (!req) return NULL; handle->search_index = -1; } else { char *const new_name = search_make_new(base->global_search_state, 0, name); if (!new_name) return NULL; req = request_new(base, handle, type, new_name, flags, user_callback, user_arg); mm_free(new_name); if (!req) return NULL; handle->search_index = 0; } EVUTIL_ASSERT(handle->search_origname == NULL); handle->search_origname = mm_strdup(name); if (handle->search_origname == NULL) { /* XXX Should we dealloc req? If yes, how? */ return NULL; } handle->search_state = base->global_search_state; handle->search_flags = flags; base->global_search_state->refcount++; request_submit(req); return req; } else { struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg); if (!req) return NULL; request_submit(req); return req; } } /* this is called when a request has failed to find a name. We need to check */ /* if it is part of a search and, if so, try the next name in the list */ /* returns: */ /* 0 another request has been submitted */ /* 1 no more requests needed */ static int search_try_next(struct evdns_request *const handle) { struct request *req = handle->current_req; struct evdns_base *base = req->base; struct request *newreq; ASSERT_LOCKED(base); if (handle->search_state) { /* it is part of a search */ char *new_name; handle->search_index++; if (handle->search_index >= handle->search_state->num_domains) { /* no more postfixes to try, however we may need to try */ /* this name without a postfix */ if (string_num_dots(handle->search_origname) < handle->search_state->ndots) { /* yep, we need to try it raw */ newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer); log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname); if (newreq) { search_request_finished(handle); goto submit_next; } } return 1; } new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname); if (!new_name) return 1; log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index); newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer); mm_free(new_name); if (!newreq) return 1; goto submit_next; } return 1; submit_next: request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0); handle->current_req = newreq; newreq->handle = handle; request_submit(newreq); return 0; } static void search_request_finished(struct evdns_request *const handle) { ASSERT_LOCKED(handle->current_req->base); if (handle->search_state) { search_state_decref(handle->search_state); handle->search_state = NULL; } if (handle->search_origname) { mm_free(handle->search_origname); handle->search_origname = NULL; } } /* ================================================================= */ /* Parsing resolv.conf files */ static void evdns_resolv_set_defaults(struct evdns_base *base, int flags) { /* if the file isn't found then we assume a local resolver */ ASSERT_LOCKED(base); if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base); if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1"); } #ifndef _EVENT_HAVE_STRTOK_R static char * strtok_r(char *s, const char *delim, char **state) { char *cp, *start; start = cp = s ? s : *state; if (!cp) return NULL; while (*cp && !strchr(delim, *cp)) ++cp; if (!*cp) { if (cp == start) return NULL; *state = NULL; return start; } else { *cp++ = '\0'; *state = cp; return start; } } #endif /* helper version of atoi which returns -1 on error */ static int strtoint(const char *const str) { char *endptr; const int r = strtol(str, &endptr, 10); if (*endptr) return -1; return r; } /* Parse a number of seconds into a timeval; return -1 on error. */ static int strtotimeval(const char *const str, struct timeval *out) { double d; char *endptr; d = strtod(str, &endptr); if (*endptr) return -1; if (d < 0) return -1; out->tv_sec = (int) d; out->tv_usec = (int) ((d - (int) d)*1000000); if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */ return -1; return 0; } /* helper version of atoi that returns -1 on error and clips to bounds. */ static int strtoint_clipped(const char *const str, int min, int max) { int r = strtoint(str); if (r == -1) return r; else if (r<min) return min; else if (r>max) return max; else return r; } static int evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight) { int old_n_heads = base->n_req_heads, n_heads; struct request **old_heads = base->req_heads, **new_heads, *req; int i; ASSERT_LOCKED(base); if (maxinflight < 1) maxinflight = 1; n_heads = (maxinflight+4) / 5; EVUTIL_ASSERT(n_heads > 0); new_heads = mm_calloc(n_heads, sizeof(struct request*)); if (!new_heads) return (-1); if (old_heads) { for (i = 0; i < old_n_heads; ++i) { while (old_heads[i]) { req = old_heads[i]; evdns_request_remove(req, &old_heads[i]); evdns_request_insert(req, &new_heads[req->trans_id % n_heads]); } } mm_free(old_heads); } base->req_heads = new_heads; base->n_req_heads = n_heads; base->global_max_requests_inflight = maxinflight; return (0); } /* exported function */ int evdns_base_set_option(struct evdns_base *base, const char *option, const char *val) { int res; EVDNS_LOCK(base); res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL); EVDNS_UNLOCK(base); return res; } static inline int str_matches_option(const char *s1, const char *optionname) { /* Option names are given as "option:" We accept either 'option' in * s1, or 'option:randomjunk'. The latter form is to implement the * resolv.conf parser. */ size_t optlen = strlen(optionname); size_t slen = strlen(s1); if (slen == optlen || slen == optlen - 1) return !strncmp(s1, optionname, slen); else if (slen > optlen) return !strncmp(s1, optionname, optlen); else return 0; } static int evdns_base_set_option_impl(struct evdns_base *base, const char *option, const char *val, int flags) { ASSERT_LOCKED(base); if (str_matches_option(option, "ndots:")) { const int ndots = strtoint(val); if (ndots == -1) return -1; if (!(flags & DNS_OPTION_SEARCH)) return 0; log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); if (!base->global_search_state) base->global_search_state = search_state_new(); if (!base->global_search_state) return -1; base->global_search_state->ndots = ndots; } else if (str_matches_option(option, "timeout:")) { struct timeval tv; if (strtotimeval(val, &tv) == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val); memcpy(&base->global_timeout, &tv, sizeof(struct timeval)); } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) { struct timeval tv; if (strtotimeval(val, &tv) == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s", val); memcpy(&base->global_getaddrinfo_allow_skew, &tv, sizeof(struct timeval)); } else if (str_matches_option(option, "max-timeouts:")) { const int maxtimeout = strtoint_clipped(val, 1, 255); if (maxtimeout == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", maxtimeout); base->global_max_nameserver_timeout = maxtimeout; } else if (str_matches_option(option, "max-inflight:")) { const int maxinflight = strtoint_clipped(val, 1, 65000); if (maxinflight == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", maxinflight); evdns_base_set_max_requests_inflight(base, maxinflight); } else if (str_matches_option(option, "attempts:")) { int retries = strtoint(val); if (retries == -1) return -1; if (retries > 255) retries = 255; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); base->global_max_retransmits = retries; } else if (str_matches_option(option, "randomize-case:")) { int randcase = strtoint(val); if (!(flags & DNS_OPTION_MISC)) return 0; base->global_randomize_case = randcase; } else if (str_matches_option(option, "bind-to:")) { /* XXX This only applies to successive nameservers, not * to already-configured ones. We might want to fix that. */ int len = sizeof(base->global_outgoing_address); if (!(flags & DNS_OPTION_NAMESERVERS)) return 0; if (evutil_parse_sockaddr_port(val, (struct sockaddr*)&base->global_outgoing_address, &len)) return -1; base->global_outgoing_addrlen = len; } else if (str_matches_option(option, "initial-probe-timeout:")) { struct timeval tv; if (strtotimeval(val, &tv) == -1) return -1; if (tv.tv_sec > 3600) tv.tv_sec = 3600; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s", val); memcpy(&base->global_nameserver_probe_initial_timeout, &tv, sizeof(tv)); } return 0; } int evdns_set_option(const char *option, const char *val, int flags) { if (!current_base) current_base = evdns_base_new(NULL, 0); return evdns_base_set_option(current_base, option, val); } static void resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) { char *strtok_state; static const char *const delims = " \t"; #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) char *const first_token = strtok_r(start, delims, &strtok_state); ASSERT_LOCKED(base); if (!first_token) return; if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { const char *const nameserver = NEXT_TOKEN; if (nameserver) evdns_base_nameserver_ip_add(base, nameserver); } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { const char *const domain = NEXT_TOKEN; if (domain) { search_postfix_clear(base); search_postfix_add(base, domain); } } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { const char *domain; search_postfix_clear(base); while ((domain = NEXT_TOKEN)) { search_postfix_add(base, domain); } search_reverse(base); } else if (!strcmp(first_token, "options")) { const char *option; while ((option = NEXT_TOKEN)) { const char *val = strchr(option, ':'); evdns_base_set_option_impl(base, option, val ? val+1 : "", flags); } } #undef NEXT_TOKEN } /* exported function */ /* returns: */ /* 0 no errors */ /* 1 failed to open file */ /* 2 failed to stat file */ /* 3 file too large */ /* 4 out of memory */ /* 5 short read from file */ int evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) { int res; EVDNS_LOCK(base); res = evdns_base_resolv_conf_parse_impl(base, flags, filename); EVDNS_UNLOCK(base); return res; } static char * evdns_get_default_hosts_filename(void) { #ifdef WIN32 /* Windows is a little coy about where it puts its configuration * files. Sure, they're _usually_ in C:\windows\system32, but * there's no reason in principle they couldn't be in * W:\hoboken chicken emergency\ */ char path[MAX_PATH+1]; static const char hostfile[] = "\\drivers\\etc\\hosts"; char *path_out; size_t len_out; if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0)) return NULL; len_out = strlen(path)+strlen(hostfile); path_out = mm_malloc(len_out+1); evutil_snprintf(path_out, len_out, "%s%s", path, hostfile); return path_out; #else return mm_strdup("/etc/hosts"); #endif } static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) { size_t n; char *resolv; char *start; int err = 0; log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); if (flags & DNS_OPTION_HOSTSFILE) { char *fname = evdns_get_default_hosts_filename(); evdns_base_load_hosts(base, fname); if (fname) mm_free(fname); } if ((err = evutil_read_file(filename, &resolv, &n, 0)) < 0) { if (err == -1) { /* No file. */ evdns_resolv_set_defaults(base, flags); return 1; } else { return 2; } } start = resolv; for (;;) { char *const newline = strchr(start, '\n'); if (!newline) { resolv_conf_parse_line(base, start, flags); break; } else { *newline = 0; resolv_conf_parse_line(base, start, flags); start = newline + 1; } } if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) { /* no nameservers were configured. */ evdns_base_nameserver_ip_add(base, "127.0.0.1"); err = 6; } if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) { search_set_from_hostname(base); } mm_free(resolv); return err; } int evdns_resolv_conf_parse(int flags, const char *const filename) { if (!current_base) current_base = evdns_base_new(NULL, 0); return evdns_base_resolv_conf_parse(current_base, flags, filename); } #ifdef WIN32 /* Add multiple nameservers from a space-or-comma-separated list. */ static int evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) { const char *addr; char *buf; int r; ASSERT_LOCKED(base); while (*ips) { while (isspace(*ips) || *ips == ',' || *ips == '\t') ++ips; addr = ips; while (isdigit(*ips) || *ips == '.' || *ips == ':' || *ips=='[' || *ips==']') ++ips; buf = mm_malloc(ips-addr+1); if (!buf) return 4; memcpy(buf, addr, ips-addr); buf[ips-addr] = '\0'; r = evdns_base_nameserver_ip_add(base, buf); mm_free(buf); if (r) return r; } return 0; } typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ /* figure out what our nameservers are. */ static int load_nameservers_with_getnetworkparams(struct evdns_base *base) { /* Based on MSDN examples and inspection of c-ares code. */ FIXED_INFO *fixed; HMODULE handle = 0; ULONG size = sizeof(FIXED_INFO); void *buf = NULL; int status = 0, r, added_any; IP_ADDR_STRING *ns; GetNetworkParams_fn_t fn; ASSERT_LOCKED(base); if (!(handle = evutil_load_windows_system_library( TEXT("iphlpapi.dll")))) { log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); status = -1; goto done; } if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { log(EVDNS_LOG_WARN, "Could not get address of function."); status = -1; goto done; } buf = mm_malloc(size); if (!buf) { status = 4; goto done; } fixed = buf; r = fn(fixed, &size); if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { status = -1; goto done; } if (r != ERROR_SUCCESS) { mm_free(buf); buf = mm_malloc(size); if (!buf) { status = 4; goto done; } fixed = buf; r = fn(fixed, &size); if (r != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG, "fn() failed."); status = -1; goto done; } } EVUTIL_ASSERT(fixed); added_any = 0; ns = &(fixed->DnsServerList); while (ns) { r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String); if (r) { log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d", (ns->IpAddress.String),(int)GetLastError()); status = r; } else { ++added_any; log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); } ns = ns->Next; } if (!added_any) { log(EVDNS_LOG_DEBUG, "No nameservers added."); if (status == 0) status = -1; } else { status = 0; } done: if (buf) mm_free(buf); if (handle) FreeLibrary(handle); return status; } static int config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey) { char *buf; DWORD bufsz = 0, type = 0; int status = 0; ASSERT_LOCKED(base); if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) != ERROR_MORE_DATA) return -1; if (!(buf = mm_malloc(bufsz))) return -1; if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) == ERROR_SUCCESS && bufsz > 1) { status = evdns_nameserver_ip_add_line(base,buf); } mm_free(buf); return status; } #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\") #define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP") #define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters") static int load_nameservers_from_registry(struct evdns_base *base) { int found = 0; int r; #define TRY(k, name) \ if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \ log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ found = 1; \ } else if (!found) { \ log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ #k,#name); \ } ASSERT_LOCKED(base); if (((int)GetVersion()) > 0) { /* NT */ HKEY nt_key = 0, interfaces_key = 0; if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ, &nt_key) != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); return -1; } r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0, KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, &interfaces_key); if (r != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); return -1; } TRY(nt_key, "NameServer"); TRY(nt_key, "DhcpNameServer"); TRY(interfaces_key, "NameServer"); TRY(interfaces_key, "DhcpNameServer"); RegCloseKey(interfaces_key); RegCloseKey(nt_key); } else { HKEY win_key = 0; if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, KEY_READ, &win_key) != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); return -1; } TRY(win_key, "NameServer"); RegCloseKey(win_key); } if (found == 0) { log(EVDNS_LOG_WARN,"Didn't find any nameservers."); } return found ? 0 : -1; #undef TRY } int evdns_base_config_windows_nameservers(struct evdns_base *base) { int r; char *fname; if (base == NULL) base = current_base; if (base == NULL) return -1; EVDNS_LOCK(base); if (load_nameservers_with_getnetworkparams(base) == 0) { EVDNS_UNLOCK(base); return 0; } r = load_nameservers_from_registry(base); fname = evdns_get_default_hosts_filename(); evdns_base_load_hosts(base, fname); if (fname) mm_free(fname); EVDNS_UNLOCK(base); return r; } int evdns_config_windows_nameservers(void) { if (!current_base) { current_base = evdns_base_new(NULL, 1); return current_base == NULL ? -1 : 0; } else { return evdns_base_config_windows_nameservers(current_base); } } #endif struct evdns_base * evdns_base_new(struct event_base *event_base, int initialize_nameservers) { struct evdns_base *base; if (evutil_secure_rng_init() < 0) { log(EVDNS_LOG_WARN, "Unable to seed random number generator; " "DNS can't run."); return NULL; } /* Give the evutil library a hook into its evdns-enabled * functionality. We can't just call evdns_getaddrinfo directly or * else libevent-core will depend on libevent-extras. */ evutil_set_evdns_getaddrinfo_fn(evdns_getaddrinfo); base = mm_malloc(sizeof(struct evdns_base)); if (base == NULL) return (NULL); memset(base, 0, sizeof(struct evdns_base)); base->req_waiting_head = NULL; EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); EVDNS_LOCK(base); /* Set max requests inflight and allocate req_heads. */ base->req_heads = NULL; evdns_base_set_max_requests_inflight(base, 64); base->server_head = NULL; base->event_base = event_base; base->global_good_nameservers = base->global_requests_inflight = base->global_requests_waiting = 0; base->global_timeout.tv_sec = 5; base->global_timeout.tv_usec = 0; base->global_max_reissues = 1; base->global_max_retransmits = 3; base->global_max_nameserver_timeout = 3; base->global_search_state = NULL; base->global_randomize_case = 1; base->global_getaddrinfo_allow_skew.tv_sec = 3; base->global_getaddrinfo_allow_skew.tv_usec = 0; base->global_nameserver_probe_initial_timeout.tv_sec = 10; base->global_nameserver_probe_initial_timeout.tv_usec = 0; TAILQ_INIT(&base->hostsdb); if (initialize_nameservers) { int r; #ifdef WIN32 r = evdns_base_config_windows_nameservers(base); #else r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf"); #endif if (r == -1) { evdns_base_free_and_unlock(base, 0); return NULL; } } EVDNS_UNLOCK(base); return base; } int evdns_init(void) { struct evdns_base *base = evdns_base_new(NULL, 1); if (base) { current_base = base; return 0; } else { return -1; } } const char * evdns_err_to_string(int err) { switch (err) { case DNS_ERR_NONE: return "no error"; case DNS_ERR_FORMAT: return "misformatted query"; case DNS_ERR_SERVERFAILED: return "server failed"; case DNS_ERR_NOTEXIST: return "name does not exist"; case DNS_ERR_NOTIMPL: return "query not implemented"; case DNS_ERR_REFUSED: return "refused"; case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; case DNS_ERR_UNKNOWN: return "unknown"; case DNS_ERR_TIMEOUT: return "request timed out"; case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; case DNS_ERR_CANCEL: return "dns request canceled"; case DNS_ERR_NODATA: return "no records in the reply"; default: return "[Unknown error code]"; } } static void evdns_nameserver_free(struct nameserver *server) { if (server->socket >= 0) evutil_closesocket(server->socket); (void) event_del(&server->event); event_debug_unassign(&server->event); if (server->state == 0) (void) event_del(&server->timeout_event); event_debug_unassign(&server->timeout_event); mm_free(server); } static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests) { struct nameserver *server, *server_next; struct search_domain *dom, *dom_next; int i; /* Requires that we hold the lock. */ /* TODO(nickm) we might need to refcount here. */ for (i = 0; i < base->n_req_heads; ++i) { while (base->req_heads[i]) { if (fail_requests) reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL); request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1); } } while (base->req_waiting_head) { if (fail_requests) reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); request_finished(base->req_waiting_head, &base->req_waiting_head, 1); } base->global_requests_inflight = base->global_requests_waiting = 0; for (server = base->server_head; server; server = server_next) { server_next = server->next; evdns_nameserver_free(server); if (server_next == base->server_head) break; } base->server_head = NULL; base->global_good_nameservers = 0; if (base->global_search_state) { for (dom = base->global_search_state->head; dom; dom = dom_next) { dom_next = dom->next; mm_free(dom); } mm_free(base->global_search_state); base->global_search_state = NULL; } { struct hosts_entry *victim; while ((victim = TAILQ_FIRST(&base->hostsdb))) { TAILQ_REMOVE(&base->hostsdb, victim, next); mm_free(victim); } } mm_free(base->req_heads); EVDNS_UNLOCK(base); EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE); mm_free(base); } void evdns_base_free(struct evdns_base *base, int fail_requests) { EVDNS_LOCK(base); evdns_base_free_and_unlock(base, fail_requests); } void evdns_shutdown(int fail_requests) { if (current_base) { struct evdns_base *b = current_base; current_base = NULL; evdns_base_free(b, fail_requests); } evdns_log_fn = NULL; } static int evdns_base_parse_hosts_line(struct evdns_base *base, char *line) { char *strtok_state; static const char *const delims = " \t"; char *const addr = strtok_r(line, delims, &strtok_state); char *hostname, *hash; struct sockaddr_storage ss; int socklen = sizeof(ss); ASSERT_LOCKED(base); #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) if (!addr || *addr == '#') return 0; memset(&ss, 0, sizeof(ss)); if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0) return -1; if (socklen > (int)sizeof(struct sockaddr_in6)) return -1; if (sockaddr_getport((struct sockaddr*)&ss)) return -1; while ((hostname = NEXT_TOKEN)) { struct hosts_entry *he; size_t namelen; if ((hash = strchr(hostname, '#'))) { if (hash == hostname) return 0; *hash = '\0'; } namelen = strlen(hostname); he = mm_calloc(1, sizeof(struct hosts_entry)+namelen); if (!he) return -1; EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr)); memcpy(&he->addr, &ss, socklen); memcpy(he->hostname, hostname, namelen+1); he->addrlen = socklen; TAILQ_INSERT_TAIL(&base->hostsdb, he, next); if (hash) return 0; } return 0; #undef NEXT_TOKEN } static int evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname) { char *str=NULL, *cp, *eol; size_t len; int err=0; ASSERT_LOCKED(base); if (hosts_fname == NULL || (err = evutil_read_file(hosts_fname, &str, &len, 0)) < 0) { char tmp[64]; strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp)); evdns_base_parse_hosts_line(base, tmp); strlcpy(tmp, "::1 localhost", sizeof(tmp)); evdns_base_parse_hosts_line(base, tmp); return err ? -1 : 0; } /* This will break early if there is a NUL in the hosts file. * Probably not a problem.*/ cp = str; for (;;) { eol = strchr(cp, '\n'); if (eol) { *eol = '\0'; evdns_base_parse_hosts_line(base, cp); cp = eol+1; } else { evdns_base_parse_hosts_line(base, cp); break; } } mm_free(str); return 0; } int evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname) { int res; if (!base) base = current_base; EVDNS_LOCK(base); res = evdns_base_load_hosts_impl(base, hosts_fname); EVDNS_UNLOCK(base); return res; } /* A single request for a getaddrinfo, either v4 or v6. */ struct getaddrinfo_subrequest { struct evdns_request *r; ev_uint32_t type; }; /* State data used to implement an in-progress getaddrinfo. */ struct evdns_getaddrinfo_request { struct evdns_base *evdns_base; /* Copy of the modified 'hints' data that we'll use to build * answers. */ struct evutil_addrinfo hints; /* The callback to invoke when we're done */ evdns_getaddrinfo_cb user_cb; /* User-supplied data to give to the callback. */ void *user_data; /* The port to use when building sockaddrs. */ ev_uint16_t port; /* The sub_request for an A record (if any) */ struct getaddrinfo_subrequest ipv4_request; /* The sub_request for an AAAA record (if any) */ struct getaddrinfo_subrequest ipv6_request; /* The cname result that we were told (if any) */ char *cname_result; /* If we have one request answered and one request still inflight, * then this field holds the answer from the first request... */ struct evutil_addrinfo *pending_result; /* And this event is a timeout that will tell us to cancel the second * request if it's taking a long time. */ struct event timeout; /* And this field holds the error code from the first request... */ int pending_error; /* If this is set, the user canceled this request. */ unsigned user_canceled : 1; /* If this is set, the user can no longer cancel this request; we're * just waiting for the free. */ unsigned request_done : 1; }; /* Convert an evdns errors to the equivalent getaddrinfo error. */ static int evdns_err_to_getaddrinfo_err(int e1) { /* XXX Do this better! */ if (e1 == DNS_ERR_NONE) return 0; else if (e1 == DNS_ERR_NOTEXIST) return EVUTIL_EAI_NONAME; else return EVUTIL_EAI_FAIL; } /* Return the more informative of two getaddrinfo errors. */ static int getaddrinfo_merge_err(int e1, int e2) { /* XXXX be cleverer here. */ if (e1 == 0) return e2; else return e1; } static void free_getaddrinfo_request(struct evdns_getaddrinfo_request *data) { /* DO NOT CALL this if either of the requests is pending. Only once * both callbacks have been invoked is it safe to free the request */ if (data->pending_result) evutil_freeaddrinfo(data->pending_result); if (data->cname_result) mm_free(data->cname_result); event_del(&data->timeout); mm_free(data); return; } static void add_cname_to_reply(struct evdns_getaddrinfo_request *data, struct evutil_addrinfo *ai) { if (data->cname_result && ai) { ai->ai_canonname = data->cname_result; data->cname_result = NULL; } } /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo * request has finished, but the other one took too long to answer. Pass * along the answer we got, and cancel the other request. */ static void evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr) { int v4_timedout = 0, v6_timedout = 0; struct evdns_getaddrinfo_request *data = ptr; /* Cancel any pending requests, and note which one */ if (data->ipv4_request.r) { evdns_cancel_request(NULL, data->ipv4_request.r); v4_timedout = 1; EVDNS_LOCK(data->evdns_base); ++data->evdns_base->getaddrinfo_ipv4_timeouts; EVDNS_UNLOCK(data->evdns_base); } if (data->ipv6_request.r) { evdns_cancel_request(NULL, data->ipv6_request.r); v6_timedout = 1; EVDNS_LOCK(data->evdns_base); ++data->evdns_base->getaddrinfo_ipv6_timeouts; EVDNS_UNLOCK(data->evdns_base); } /* We only use this timeout callback when we have an answer for * one address. */ EVUTIL_ASSERT(!v4_timedout || !v6_timedout); /* Report the outcome of the other request that didn't time out. */ if (data->pending_result) { add_cname_to_reply(data, data->pending_result); data->user_cb(0, data->pending_result, data->user_data); data->pending_result = NULL; } else { int e = data->pending_error; if (!e) e = EVUTIL_EAI_AGAIN; data->user_cb(e, NULL, data->user_data); } if (!v4_timedout && !v6_timedout) { /* should be impossible? XXXX */ free_getaddrinfo_request(data); } } static int evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base, struct evdns_getaddrinfo_request *data) { return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew); } static inline int evdns_result_is_answer(int result) { return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED && result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL); } static void evdns_getaddrinfo_gotresolve(int result, char type, int count, int ttl, void *addresses, void *arg) { int i; struct getaddrinfo_subrequest *req = arg; struct getaddrinfo_subrequest *other_req; struct evdns_getaddrinfo_request *data; struct evutil_addrinfo *res; struct sockaddr_in sin; struct sockaddr_in6 sin6; struct sockaddr *sa; int socklen, addrlen; void *addrp; int err; int user_canceled; EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA); if (req->type == DNS_IPv4_A) { data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request); other_req = &data->ipv6_request; } else { data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request); other_req = &data->ipv4_request; } EVDNS_LOCK(data->evdns_base); if (evdns_result_is_answer(result)) { if (req->type == DNS_IPv4_A) ++data->evdns_base->getaddrinfo_ipv4_answered; else ++data->evdns_base->getaddrinfo_ipv6_answered; } user_canceled = data->user_canceled; if (other_req->r == NULL) data->request_done = 1; EVDNS_UNLOCK(data->evdns_base); req->r = NULL; if (result == DNS_ERR_CANCEL && ! user_canceled) { /* Internal cancel request from timeout or internal error. * we already answered the user. */ if (other_req->r == NULL) free_getaddrinfo_request(data); return; } if (result == DNS_ERR_NONE) { if (count == 0) err = EVUTIL_EAI_NODATA; else err = 0; } else { err = evdns_err_to_getaddrinfo_err(result); } if (err) { /* Looks like we got an error. */ if (other_req->r) { /* The other request is still working; maybe it will * succeed. */ /* XXXX handle failure from set_timeout */ evdns_getaddrinfo_set_timeout(data->evdns_base, data); data->pending_error = err; return; } if (user_canceled) { data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); } else if (data->pending_result) { /* If we have an answer waiting, and we weren't * canceled, ignore this error. */ add_cname_to_reply(data, data->pending_result); data->user_cb(0, data->pending_result, data->user_data); data->pending_result = NULL; } else { if (data->pending_error) err = getaddrinfo_merge_err(err, data->pending_error); data->user_cb(err, NULL, data->user_data); } free_getaddrinfo_request(data); return; } else if (user_canceled) { if (other_req->r) { /* The other request is still working; let it hit this * callback with EVUTIL_EAI_CANCEL callback and report * the failure. */ return; } data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data); free_getaddrinfo_request(data); return; } /* Looks like we got some answers. We should turn them into addrinfos * and then either queue those or return them all. */ EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA); if (type == DNS_IPv4_A) { memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_port = htons(data->port); sa = (struct sockaddr *)&sin; socklen = sizeof(sin); addrlen = 4; addrp = &sin.sin_addr.s_addr; } else { memset(&sin6, 0, sizeof(sin6)); sin6.sin6_family = AF_INET6; sin6.sin6_port = htons(data->port); sa = (struct sockaddr *)&sin6; socklen = sizeof(sin6); addrlen = 16; addrp = &sin6.sin6_addr.s6_addr; } res = NULL; for (i=0; i < count; ++i) { struct evutil_addrinfo *ai; memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen); ai = evutil_new_addrinfo(sa, socklen, &data->hints); if (!ai) { if (other_req->r) { evdns_cancel_request(NULL, other_req->r); } data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data); if (res) evutil_freeaddrinfo(res); if (other_req->r == NULL) free_getaddrinfo_request(data); return; } res = evutil_addrinfo_append(res, ai); } if (other_req->r) { /* The other request is still in progress; wait for it */ /* XXXX handle failure from set_timeout */ evdns_getaddrinfo_set_timeout(data->evdns_base, data); data->pending_result = res; return; } else { /* The other request is done or never started; append its * results (if any) and return them. */ if (data->pending_result) { if (req->type == DNS_IPv4_A) res = evutil_addrinfo_append(res, data->pending_result); else res = evutil_addrinfo_append( data->pending_result, res); data->pending_result = NULL; } /* Call the user callback. */ add_cname_to_reply(data, res); data->user_cb(0, res, data->user_data); /* Free data. */ free_getaddrinfo_request(data); } } static struct hosts_entry * find_hosts_entry(struct evdns_base *base, const char *hostname, struct hosts_entry *find_after) { struct hosts_entry *e; if (find_after) e = TAILQ_NEXT(find_after, next); else e = TAILQ_FIRST(&base->hostsdb); for (; e; e = TAILQ_NEXT(e, next)) { if (!evutil_ascii_strcasecmp(e->hostname, hostname)) return e; } return NULL; } static int evdns_getaddrinfo_fromhosts(struct evdns_base *base, const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port, struct evutil_addrinfo **res) { int n_found = 0; struct hosts_entry *e; struct evutil_addrinfo *ai=NULL; int f = hints->ai_family; EVDNS_LOCK(base); for (e = find_hosts_entry(base, nodename, NULL); e; e = find_hosts_entry(base, nodename, e)) { struct evutil_addrinfo *ai_new; ++n_found; if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) || (e->addr.sa.sa_family == AF_INET6 && f == PF_INET)) continue; ai_new = evutil_new_addrinfo(&e->addr.sa, e->addrlen, hints); if (!ai_new) { n_found = 0; goto out; } sockaddr_setport(ai_new->ai_addr, port); ai = evutil_addrinfo_append(ai, ai_new); } EVDNS_UNLOCK(base); out: if (n_found) { /* Note that we return an empty answer if we found entries for * this hostname but none were of the right address type. */ *res = ai; return 0; } else { if (ai) evutil_freeaddrinfo(ai); return -1; } } struct evdns_getaddrinfo_request * evdns_getaddrinfo(struct evdns_base *dns_base, const char *nodename, const char *servname, const struct evutil_addrinfo *hints_in, evdns_getaddrinfo_cb cb, void *arg) { struct evdns_getaddrinfo_request *data; struct evutil_addrinfo hints; struct evutil_addrinfo *res = NULL; int err; int port = 0; int want_cname = 0; if (!dns_base) { dns_base = current_base; if (!dns_base) { log(EVDNS_LOG_WARN, "Call to getaddrinfo_async with no " "evdns_base configured."); cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */ return NULL; } } /* If we _must_ answer this immediately, do so. */ if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) { res = NULL; err = evutil_getaddrinfo(nodename, servname, hints_in, &res); cb(err, res, arg); return NULL; } if (hints_in) { memcpy(&hints, hints_in, sizeof(hints)); } else { memset(&hints, 0, sizeof(hints)); hints.ai_family = PF_UNSPEC; } evutil_adjust_hints_for_addrconfig(&hints); /* Now try to see if we _can_ answer immediately. */ /* (It would be nice to do this by calling getaddrinfo directly, with * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't * a reliable way to distinguish the "that wasn't a numeric host!" case * from any other EAI_NONAME cases.) */ err = evutil_getaddrinfo_common(nodename, servname, &hints, &res, &port); if (err != EVUTIL_EAI_NEED_RESOLVE) { cb(err, res, arg); return NULL; } /* If there is an entry in the hosts file, we should give it now. */ if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) { cb(0, res, arg); return NULL; } /* Okay, things are serious now. We're going to need to actually * launch a request. */ data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request)); if (!data) { cb(EVUTIL_EAI_MEMORY, NULL, arg); return NULL; } memcpy(&data->hints, &hints, sizeof(data->hints)); data->port = (ev_uint16_t)port; data->ipv4_request.type = DNS_IPv4_A; data->ipv6_request.type = DNS_IPv6_AAAA; data->user_cb = cb; data->user_data = arg; data->evdns_base = dns_base; want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME); /* If we are asked for a PF_UNSPEC address, we launch two requests in * parallel: one for an A address and one for an AAAA address. We * can't send just one request, since many servers only answer one * question per DNS request. * * Once we have the answer to one request, we allow for a short * timeout before we report it, to see if the other one arrives. If * they both show up in time, then we report both the answers. * * If too many addresses of one type time out or fail, we should stop * launching those requests. (XXX we don't do that yet.) */ if (hints.ai_family != PF_INET6) { log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p", nodename, &data->ipv4_request); data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base, nodename, 0, evdns_getaddrinfo_gotresolve, &data->ipv4_request); if (want_cname) data->ipv4_request.r->current_req->put_cname_in_ptr = &data->cname_result; } if (hints.ai_family != PF_INET) { log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p", nodename, &data->ipv6_request); data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base, nodename, 0, evdns_getaddrinfo_gotresolve, &data->ipv6_request); if (want_cname) data->ipv6_request.r->current_req->put_cname_in_ptr = &data->cname_result; } evtimer_assign(&data->timeout, dns_base->event_base, evdns_getaddrinfo_timeout_cb, data); if (data->ipv4_request.r || data->ipv6_request.r) { return data; } else { mm_free(data); cb(EVUTIL_EAI_FAIL, NULL, arg); return NULL; } } void evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data) { EVDNS_LOCK(data->evdns_base); if (data->request_done) { EVDNS_UNLOCK(data->evdns_base); return; } event_del(&data->timeout); data->user_canceled = 1; if (data->ipv4_request.r) evdns_cancel_request(data->evdns_base, data->ipv4_request.r); if (data->ipv6_request.r) evdns_cancel_request(data->evdns_base, data->ipv6_request.r); EVDNS_UNLOCK(data->evdns_base); }