tor-browser

evdns.c (132561B)

---

/* 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 "event2/event-config.h"
#include "evconfig-private.h"

#include <sys/types.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 <winerror.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 "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 EVENT_LOG_DEBUG
#define EVDNS_LOG_WARN EVENT_LOG_WARN
#define EVDNS_LOG_MSG EVENT_LOG_MSG

#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;

/* Number of currently inflight requests: used
 * to track when we should add/del the event. */
int requests_inflight;
};


/* 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 so_rcvbuf;
int so_sndbuf;

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

int disable_when_inactive;
};

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 void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg);

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 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 severity, const char *fmt, ...) EVDNS_LOG_CHECK;
static void
evdns_log_(int severity, const char *fmt, ...)
{
va_list args;
va_start(args,fmt);
if (evdns_log_fn) {
	char buf[512];
	int is_warn = (severity == EVDNS_LOG_WARN);
	evutil_vsnprintf(buf, sizeof(buf), fmt, args);
	evdns_log_fn(is_warn, buf);
} else {
	event_logv_(severity, NULL, fmt, args);
}
va_end(args);
}

#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)));
}
}

static void
request_swap_ns(struct request *req, struct nameserver *ns) {
if (ns && req->ns != ns) {
	EVUTIL_ASSERT(req->ns->requests_inflight > 0);
	req->ns->requests_inflight--;
	ns->requests_inflight++;

	req->ns = ns;
}
}

/* 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 */
				request_swap_ns(req, 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--;
	req->ns->requests_inflight--;
} else {
	base->global_requests_waiting--;
}
/* it was initialized during request_new / evtimer_assign */
event_debug_unassign(&req->timeout_event);

if (req->ns &&
    req->ns->requests_inflight == 0 &&
    req->base->disable_when_inactive) {
	event_del(&req->ns->event);
	evtimer_del(&req->ns->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 */
request_swap_ns(req, 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. */
/* */
/* TODO: */
/* add return code, see at nameserver_pick() and other functions. */
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;

	EVUTIL_ASSERT(base->req_waiting_head);
	req = base->req_waiting_head;

	req->ns = nameserver_pick(base);
	if (!req->ns)
		return;

	/* move a request from the waiting queue to the inflight queue */
	req->ns->requests_inflight++;

	evdns_request_remove(req, &base->req_waiting_head);

	base->global_requests_waiting--;
	base->global_requests_inflight++;

	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 event_callback 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 event_callback *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,
    event_get_priority(&req->timeout_event),
    reply_run_callback,
    req->user_pointer);
event_deferred_cb_schedule_(
	req->base->event_base,
	&d->deferred);
}


#define _QR_MASK    0x8000U
#define _OP_MASK    0x7800U
#define _AA_MASK    0x0400U
#define _TC_MASK    0x0200U
#define _RD_MASK    0x0100U
#define _RA_MASK    0x0080U
#define _Z_MASK     0x0040U
#define _AD_MASK    0x0020U
#define _CD_MASK    0x0010U
#define _RCODE_MASK 0x000fU
#define _Z_MASK_DEPRECATED 0x0070U

/* 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 & (_RCODE_MASK | _TC_MASK) || !reply || !reply->have_answer) {
	/* there was an error */
	if (flags & _TC_MASK) {
		error = DNS_ERR_TRUNCATED;
	} else if (flags & _RCODE_MASK) {
		u16 error_code = (flags & _RCODE_MASK) - 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)));
		/* Call the timeout function */
		evdns_request_timeout_callback(0, 0, req);
		return;
	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;
	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;
	if (j + label_len > length) 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 & _QR_MASK)) return -1;  /* must be an answer */
if ((flags & (_RCODE_MASK|_TC_MASK)) && (flags & (_RCODE_MASK|_TC_MASK)) != 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)

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>
	 */
	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;
	}

	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 & _QR_MASK) return -1; /* Must not be an answer. */
flags &= (_RD_MASK|_CD_MASK); /* 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 & _OP_MASK) {
	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->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;
	EVDNS_UNLOCK(port);
}
}

/* 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 |= (_QR_MASK | 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;
struct evdns_base *base = req->base;

(void) fd;
(void) events;

log(EVDNS_LOG_DEBUG, "Request %p timed out", arg);
EVDNS_LOCK(base);

if (req->tx_count >= req->base->global_max_retransmits) {
	struct nameserver *ns = req->ns;
	/* this request has failed */
	log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d",
	    arg, req->tx_count);
	reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL);

	request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
	nameserver_failed(ns, "request timed out.");
} else {
	/* retransmit it */
	log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d",
	    arg, req->tx_count);
	(void) evtimer_del(&req->timeout_event);
	request_swap_ns(req, nameserver_pick(base));
	evdns_request_transmit(req);

	req->ns->timedout++;
	if (req->ns->timedout > req->base->global_max_nameserver_timeout) {
		req->ns->timedout = 0;
		nameserver_failed(req->ns, "request timed out.");
	}
}

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);

if (server->requests_inflight == 1 &&
	req->base->disable_when_inactive &&
	event_add(&server->event, NULL) < 0) {
	return 1;
}

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)
{
	/* unable to transmit request if no nameservers */
	return 1;
}

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. we can fallthrough since
	 * we'll set a timeout, which will time out, and make us retransmit the
	 * request anyway. */
	retcode = 1;
	EVUTIL_FALLTHROUGH;
default:
	/* all ok */
	log(EVDNS_LOG_DEBUG,
	    "Setting timeout for request %p, sent to nameserver %p", req, req->ns);
	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) {
	mm_free(handle);
	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 = evutil_socket_(address->sa_family,
    SOCK_DGRAM|EVUTIL_SOCK_NONBLOCK|EVUTIL_SOCK_CLOEXEC, 0);
if (ns->socket < 0) { err = 1; goto out1; }

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;
	}
}

if (base->so_rcvbuf) {
	if (setsockopt(ns->socket, SOL_SOCKET, SO_RCVBUF,
	    (void *)&base->so_rcvbuf, sizeof(base->so_rcvbuf))) {
		log(EVDNS_LOG_WARN, "Couldn't set SO_RCVBUF to %i", base->so_rcvbuf);
		err = -SO_RCVBUF;
		goto out2;
	}
}
if (base->so_sndbuf) {
	if (setsockopt(ns->socket, SOL_SOCKET, SO_SNDBUF,
	    (void *)&base->so_sndbuf, sizeof(base->so_sndbuf))) {
		log(EVDNS_LOG_WARN, "Couldn't set SO_SNDBUF to %i", base->so_sndbuf);
		err = -SO_SNDBUF;
		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 (!base->disable_when_inactive && event_add(&ns->event, NULL) < 0) {
	err = 2;
	goto out2;
}

log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p",
    evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), ns);

/* 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;
memset(&sin, 0, sizeof(sin));
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;
}

int
evdns_base_get_nameserver_addr(struct evdns_base *base, int idx,
   struct sockaddr *sa, ev_socklen_t len)
{
int result = -1;
int i;
struct nameserver *server;
EVDNS_LOCK(base);
server = base->server_head;
for (i = 0; i < idx && server; ++i, server = server->next) {
	if (server->next == base->server_head)
		goto done;
}
if (! server)
	goto done;

if (server->addrlen > len) {
	result = (int) server->addrlen;
	goto done;
}

memcpy(sa, &server->address, server->addrlen);
result = (int) server->addrlen;
done:
EVDNS_UNLOCK(base);
return result;
}

/* 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++;
	req->ns->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);
char need_to_append_dot;
struct search_domain *dom;

if (!base_len) return NULL;
need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1;

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? */
		if (req)
			mm_free(req);
		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) {
int add_default = flags & DNS_OPTION_NAMESERVERS;
if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
	add_default = 0;

/* 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 (add_default)
	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
evdns_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 (evdns_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 (evdns_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 (randcase == -1) return -1;
	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 (evdns_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));
} else if (str_matches_option(option, "so-rcvbuf:")) {
	int buf = strtoint(val);
	if (buf == -1) return -1;
	if (!(flags & DNS_OPTION_MISC)) return 0;
	log(EVDNS_LOG_DEBUG, "Setting SO_RCVBUF to %s", val);
	base->so_rcvbuf = buf;
} else if (str_matches_option(option, "so-sndbuf:")) {
	int buf = strtoint(val);
	if (buf == -1) return -1;
	if (!(flags & DNS_OPTION_MISC)) return 0;
	log(EVDNS_LOG_DEBUG, "Setting SO_SNDBUF to %s", val);
	base->so_sndbuf = buf;
}
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)+1;
path_out = mm_malloc(len_out);
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;
int add_default;

log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);

add_default = flags & DNS_OPTION_NAMESERVERS;
if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
	add_default = 0;

if (flags & DNS_OPTION_HOSTSFILE) {
	char *fname = evdns_get_default_hosts_filename();
	evdns_base_load_hosts(base, fname);
	if (fname)
		mm_free(fname);
}

if (!filename) {
	evdns_resolv_set_defaults(base, flags);
	return 1;
}

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 && add_default) {
	/* 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);
fname = evdns_get_default_hosts_filename();
log(EVDNS_LOG_DEBUG, "Loading hosts entries from %s", fname);
evdns_base_load_hosts(base, fname);
if (fname)
	mm_free(fname);

if (load_nameservers_with_getnetworkparams(base) == 0) {
	EVDNS_UNLOCK(base);
	return 0;
}
r = load_nameservers_from_registry(base);

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 flags)
{
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);
evutil_set_evdns_getaddrinfo_cancel_fn_(evdns_getaddrinfo_cancel);

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);

#define EVDNS_BASE_ALL_FLAGS ( \
EVDNS_BASE_INITIALIZE_NAMESERVERS | \
EVDNS_BASE_DISABLE_WHEN_INACTIVE  | \
EVDNS_BASE_NAMESERVERS_NO_DEFAULT | \
0)

if (flags & ~EVDNS_BASE_ALL_FLAGS) {
	flags = EVDNS_BASE_INITIALIZE_NAMESERVERS;
	log(EVDNS_LOG_WARN,
	    "Unrecognized flag passed to evdns_base_new(). Assuming "
	    "you meant EVDNS_BASE_INITIALIZE_NAMESERVERS.");
}
#undef EVDNS_BASE_ALL_FLAGS

if (flags & EVDNS_BASE_INITIALIZE_NAMESERVERS) {
	int r;
	int opts = DNS_OPTIONS_ALL;
	if (flags & EVDNS_BASE_NAMESERVERS_NO_DEFAULT) {
		opts |= DNS_OPTION_NAMESERVERS_NO_DEFAULT;
	}

#ifdef _WIN32
	r = evdns_base_config_windows_nameservers(base);
#else
	r = evdns_base_resolv_conf_parse(base, opts, "/etc/resolv.conf");
#endif
	if (r) {
		evdns_base_free_and_unlock(base, 0);
		return NULL;
	}
}
if (flags & EVDNS_BASE_DISABLE_WHEN_INACTIVE) {
	base->disable_when_inactive = 1;
}

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);
if (server->probe_request) {
	evdns_cancel_request(server->base, server->probe_request);
	server->probe_request = NULL;
}
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. */

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);
}
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);
	}
}
base->global_requests_inflight = base->global_requests_waiting = 0;

for (server = base->server_head; server; server = server_next) {
	server_next = server->next;
	/** already done something before */
	server->probe_request = NULL;
	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_base_clear_host_addresses(struct evdns_base *base)
{
struct hosts_entry *victim;
EVDNS_LOCK(base);
while ((victim = TAILQ_FIRST(&base->hostsdb))) {
	TAILQ_REMOVE(&base->hostsdb, victim, next);
	mm_free(victim);
}
EVDNS_UNLOCK(base);
}

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) {
	/* XXXX This does nothing if the request's callback is already
	 * running (pending_cb is set). */
	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) {
	/* XXXX This does nothing if the request's callback is already
	 * running (pending_cb is set). */
	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);
}

data->user_cb = NULL; /* prevent double-call if evdns callbacks are
		       * in-progress. XXXX It would be better if this
		       * weren't necessary. */

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;
}

/** Called from evdns_base_free() with @fail_requests == 1 */
if (result != DNS_ERR_SHUTDOWN) {
	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);
} else {
	data->evdns_base = NULL;
	user_canceled = data->user_canceled;
}

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 (data->user_cb == NULL) {
	/* We already answered.  XXXX This shouldn't be needed; see
	 * comments in evdns_getaddrinfo_timeout_cb */
	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 */
		if (result != DNS_ERR_SHUTDOWN) {
			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;
int started = 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.)
 */

EVDNS_LOCK(dns_base);

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)
		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)
		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);

started = (data->ipv4_request.r || data->ipv6_request.r);

EVDNS_UNLOCK(dns_base);

if (started) {
	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);
}