The Tor Browser: comparison ipc/chromium/src/third

--1:000000000000
+:1e0b06fc6577
+/* Copyright 2006-2007 Niels Provos
+* Copyright 2007-2012 Nick Mathewson and Niels Provos
+*
+* Redistribution and use in source and binary forms, with or without
+* modification, are permitted provided that the following conditions
+* are met:
+* 1. Redistributions of source code must retain the above copyright
+*    notice, this list of conditions and the following disclaimer.
+* 2. Redistributions in binary form must reproduce the above copyright
+*    notice, this list of conditions and the following disclaimer in the
+*    documentation and/or other materials provided with the distribution.
+* 3. The name of the author may not be used to endorse or promote products
+*    derived from this software without specific prior written permission.
+*
+* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+/* Based on software by Adam Langly. Adam's original message:
+*
+* Async DNS Library
+* Adam Langley <agl@imperialviolet.org>
+* http://www.imperialviolet.org/eventdns.html
+* Public Domain code
+*
+* This software is Public Domain. To view a copy of the public domain dedication,
+* visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
+* Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
+*
+* I ask and expect, but do not require, that all derivative works contain an
+* attribution similar to:
+*	Parts developed by Adam Langley <agl@imperialviolet.org>
+*
+* You may wish to replace the word "Parts" with something else depending on
+* the amount of original code.
+*
+* (Derivative works does not include programs which link against, run or include
+* the source verbatim in their source distributions)
+*
+* Version: 0.1b
+*/
+#include <sys/types.h>
+#include "event2/event-config.h"
+#ifndef _FORTIFY_SOURCE
+#define _FORTIFY_SOURCE 3
+#endif
+#include <string.h>
+#include <fcntl.h>
+#ifdef _EVENT_HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+#ifdef _EVENT_HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#ifdef _EVENT_HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <limits.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdarg.h>
+#ifdef WIN32
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#ifndef _WIN32_IE
+#define _WIN32_IE 0x400
+#endif
+#include <shlobj.h>
+#endif
+#include "event2/dns.h"
+#include "event2/dns_struct.h"
+#include "event2/dns_compat.h"
+#include "event2/util.h"
+#include "event2/event.h"
+#include "event2/event_struct.h"
+#include "event2/thread.h"
+#include "event2/bufferevent.h"
+#include "event2/bufferevent_struct.h"
+#include "bufferevent-internal.h"
+#include "defer-internal.h"
+#include "log-internal.h"
+#include "mm-internal.h"
+#include "strlcpy-internal.h"
+#include "ipv6-internal.h"
+#include "util-internal.h"
+#include "evthread-internal.h"
+#ifdef WIN32
+#include <ctype.h>
+#include <winsock2.h>
+#include <windows.h>
+#include <iphlpapi.h>
+#include <io.h>
+#else
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#endif
+#ifdef _EVENT_HAVE_NETINET_IN6_H
+#include <netinet/in6.h>
+#endif
+#define EVDNS_LOG_DEBUG 0
+#define EVDNS_LOG_WARN 1
+#define EVDNS_LOG_MSG 2
+#ifndef HOST_NAME_MAX
+#define HOST_NAME_MAX 255
+#endif
+#include <stdio.h>
+#undef MIN
+#define MIN(a,b) ((a)<(b)?(a):(b))
+#define ASSERT_VALID_REQUEST(req) \
+	EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req))
+#define u64 ev_uint64_t
+#define u32 ev_uint32_t
+#define u16 ev_uint16_t
+#define u8  ev_uint8_t
+/* maximum number of addresses from a single packet */
+/* that we bother recording */
+#define MAX_V4_ADDRS 32
+#define MAX_V6_ADDRS 32
+#define TYPE_A	       EVDNS_TYPE_A
+#define TYPE_CNAME     5
+#define TYPE_PTR       EVDNS_TYPE_PTR
+#define TYPE_SOA       EVDNS_TYPE_SOA
+#define TYPE_AAAA      EVDNS_TYPE_AAAA
+#define CLASS_INET     EVDNS_CLASS_INET
+/* Persistent handle.  We keep this separate from 'struct request' since we
+* need some object to last for as long as an evdns_request is outstanding so
+* that it can be canceled, whereas a search request can lead to multiple
+* 'struct request' instances being created over its lifetime. */
+struct evdns_request {
+	struct request *current_req;
+	struct evdns_base *base;
+	int pending_cb; /* Waiting for its callback to be invoked; not
+			 * owned by event base any more. */
+	/* elements used by the searching code */
+	int search_index;
+	struct search_state *search_state;
+	char *search_origname;	/* needs to be free()ed */
+	int search_flags;
+};
+struct request {
+	u8 *request;  /* the dns packet data */
+	u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */
+	unsigned int request_len;
+	int reissue_count;
+	int tx_count;  /* the number of times that this packet has been sent */
+	void *user_pointer;  /* the pointer given to us for this request */
+	evdns_callback_type user_callback;
+	struct nameserver *ns;	/* the server which we last sent it */
+	/* these objects are kept in a circular list */
+	/* XXX We could turn this into a CIRCLEQ. */
+	struct request *next, *prev;
+	struct event timeout_event;
+	u16 trans_id;  /* the transaction id */
+	unsigned request_appended :1;	/* true if the request pointer is data which follows this struct */
+	unsigned transmit_me :1;  /* needs to be transmitted */
+	/* XXXX This is a horrible hack. */
+	char **put_cname_in_ptr; /* store the cname here if we get one. */
+	struct evdns_base *base;
+	struct evdns_request *handle;
+};
+struct reply {
+	unsigned int type;
+	unsigned int have_answer : 1;
+	union {
+		struct {
+			u32 addrcount;
+			u32 addresses[MAX_V4_ADDRS];
+		} a;
+		struct {
+			u32 addrcount;
+			struct in6_addr addresses[MAX_V6_ADDRS];
+		} aaaa;
+		struct {
+			char name[HOST_NAME_MAX];
+		} ptr;
+	} data;
+};
+struct nameserver {
+	evutil_socket_t socket;	 /* a connected UDP socket */
+	struct sockaddr_storage address;
+	ev_socklen_t addrlen;
+	int failed_times;  /* number of times which we have given this server a chance */
+	int timedout;  /* number of times in a row a request has timed out */
+	struct event event;
+	/* these objects are kept in a circular list */
+	struct nameserver *next, *prev;
+	struct event timeout_event;  /* used to keep the timeout for */
+				     /* when we next probe this server. */
+				     /* Valid if state == 0 */
+	/* Outstanding probe request for this nameserver, if any */
+	struct evdns_request *probe_request;
+	char state;  /* zero if we think that this server is down */
+	char choked;  /* true if we have an EAGAIN from this server's socket */
+	char write_waiting;  /* true if we are waiting for EV_WRITE events */
+	struct evdns_base *base;
+};
+/* Represents a local port where we're listening for DNS requests. Right now, */
+/* only UDP is supported. */
+struct evdns_server_port {
+	evutil_socket_t socket; /* socket we use to read queries and write replies. */
+	int refcnt; /* reference count. */
+	char choked; /* Are we currently blocked from writing? */
+	char closing; /* Are we trying to close this port, pending writes? */
+	evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
+	void *user_data; /* Opaque pointer passed to user_callback */
+	struct event event; /* Read/write event */
+	/* circular list of replies that we want to write. */
+	struct server_request *pending_replies;
+	struct event_base *event_base;
+#ifndef _EVENT_DISABLE_THREAD_SUPPORT
+	void *lock;
+#endif
+};
+/* Represents part of a reply being built.	(That is, a single RR.) */
+struct server_reply_item {
+	struct server_reply_item *next; /* next item in sequence. */
+	char *name; /* name part of the RR */
+	u16 type; /* The RR type */
+	u16 class; /* The RR class (usually CLASS_INET) */
+	u32 ttl; /* The RR TTL */
+	char is_name; /* True iff data is a label */
+	u16 datalen; /* Length of data; -1 if data is a label */
+	void *data; /* The contents of the RR */
+};
+/* Represents a request that we've received as a DNS server, and holds */
+/* the components of the reply as we're constructing it. */
+struct server_request {
+	/* Pointers to the next and previous entries on the list of replies */
+	/* that we're waiting to write.	 Only set if we have tried to respond */
+	/* and gotten EAGAIN. */
+	struct server_request *next_pending;
+	struct server_request *prev_pending;
+	u16 trans_id; /* Transaction id. */
+	struct evdns_server_port *port; /* Which port received this request on? */
+	struct sockaddr_storage addr; /* Where to send the response */
+	ev_socklen_t addrlen; /* length of addr */
+	int n_answer; /* how many answer RRs have been set? */
+	int n_authority; /* how many authority RRs have been set? */
+	int n_additional; /* how many additional RRs have been set? */
+	struct server_reply_item *answer; /* linked list of answer RRs */
+	struct server_reply_item *authority; /* linked list of authority RRs */
+	struct server_reply_item *additional; /* linked list of additional RRs */
+	/* Constructed response.  Only set once we're ready to send a reply. */
+	/* Once this is set, the RR fields are cleared, and no more should be set. */
+	char *response;
+	size_t response_len;
+	/* Caller-visible fields: flags, questions. */
+	struct evdns_server_request base;
+};
+struct evdns_base {
+	/* An array of n_req_heads circular lists for inflight requests.
+	 * Each inflight request req is in req_heads[req->trans_id % n_req_heads].
+	 */
+	struct request **req_heads;
+	/* A circular list of requests that we're waiting to send, but haven't
+	 * sent yet because there are too many requests inflight */
+	struct request *req_waiting_head;
+	/* A circular list of nameservers. */
+	struct nameserver *server_head;
+	int n_req_heads;
+	struct event_base *event_base;
+	/* The number of good nameservers that we have */
+	int global_good_nameservers;
+	/* inflight requests are contained in the req_head list */
+	/* and are actually going out across the network */
+	int global_requests_inflight;
+	/* requests which aren't inflight are in the waiting list */
+	/* and are counted here */
+	int global_requests_waiting;
+	int global_max_requests_inflight;
+	struct timeval global_timeout;	/* 5 seconds by default */
+	int global_max_reissues;  /* a reissue occurs when we get some errors from the server */
+	int global_max_retransmits;  /* number of times we'll retransmit a request which timed out */
+	/* number of timeouts in a row before we consider this server to be down */
+	int global_max_nameserver_timeout;
+	/* true iff we will use the 0x20 hack to prevent poisoning attacks. */
+	int global_randomize_case;
+	/* The first time that a nameserver fails, how long do we wait before
+	 * probing to see if it has returned?  */
+	struct timeval global_nameserver_probe_initial_timeout;
+	/** Port to bind to for outgoing DNS packets. */
+	struct sockaddr_storage global_outgoing_address;
+	/** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */
+	ev_socklen_t global_outgoing_addrlen;
+	struct timeval global_getaddrinfo_allow_skew;
+	int getaddrinfo_ipv4_timeouts;
+	int getaddrinfo_ipv6_timeouts;
+	int getaddrinfo_ipv4_answered;
+	int getaddrinfo_ipv6_answered;
+	struct search_state *global_search_state;
+	TAILQ_HEAD(hosts_list, hosts_entry) hostsdb;
+#ifndef _EVENT_DISABLE_THREAD_SUPPORT
+	void *lock;
+#endif
+};
+struct hosts_entry {
+	TAILQ_ENTRY(hosts_entry) next;
+	union {
+		struct sockaddr sa;
+		struct sockaddr_in sin;
+		struct sockaddr_in6 sin6;
+	} addr;
+	int addrlen;
+	char hostname[1];
+};
+static struct evdns_base *current_base = NULL;
+struct evdns_base *
+evdns_get_global_base(void)
+{
+	return current_base;
+}
+/* Given a pointer to an evdns_server_request, get the corresponding */
+/* server_request. */
+#define TO_SERVER_REQUEST(base_ptr)					\
+	((struct server_request*)					\
+	  (((char*)(base_ptr) - evutil_offsetof(struct server_request, base))))
+#define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads])
+static struct nameserver *nameserver_pick(struct evdns_base *base);
+static void evdns_request_insert(struct request *req, struct request **head);
+static void evdns_request_remove(struct request *req, struct request **head);
+static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg);
+static int evdns_transmit(struct evdns_base *base);
+static int evdns_request_transmit(struct request *req);
+static void nameserver_send_probe(struct nameserver *const ns);
+static void search_request_finished(struct evdns_request *const);
+static int search_try_next(struct evdns_request *const req);
+static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg);
+static void evdns_requests_pump_waiting_queue(struct evdns_base *base);
+static u16 transaction_id_pick(struct evdns_base *base);
+static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr);
+static void request_submit(struct request *const req);
+static int server_request_free(struct server_request *req);
+static void server_request_free_answers(struct server_request *req);
+static void server_port_free(struct evdns_server_port *port);
+static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg);
+static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename);
+static int evdns_base_set_option_impl(struct evdns_base *base,
+const char *option, const char *val, int flags);
+static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests);
+static int strtoint(const char *const str);
+#ifdef _EVENT_DISABLE_THREAD_SUPPORT
+#define EVDNS_LOCK(base)  _EVUTIL_NIL_STMT
+#define EVDNS_UNLOCK(base) _EVUTIL_NIL_STMT
+#define ASSERT_LOCKED(base) _EVUTIL_NIL_STMT
+#else
+#define EVDNS_LOCK(base)			\
+	EVLOCK_LOCK((base)->lock, 0)
+#define EVDNS_UNLOCK(base)			\
+	EVLOCK_UNLOCK((base)->lock, 0)
+#define ASSERT_LOCKED(base)			\
+	EVLOCK_ASSERT_LOCKED((base)->lock)
+#endif
+static void
+default_evdns_log_fn(int warning, const char *buf)
+{
+	if (warning == EVDNS_LOG_WARN)
+		event_warnx("[evdns] %s", buf);
+	else if (warning == EVDNS_LOG_MSG)
+		event_msgx("[evdns] %s", buf);
+	else
+		event_debug(("[evdns] %s", buf));
+}
+static evdns_debug_log_fn_type evdns_log_fn = NULL;
+void
+evdns_set_log_fn(evdns_debug_log_fn_type fn)
+{
+	evdns_log_fn = fn;
+}
+#ifdef __GNUC__
+#define EVDNS_LOG_CHECK	 __attribute__ ((format(printf, 2, 3)))
+#else
+#define EVDNS_LOG_CHECK
+#endif
+static void _evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK;
+static void
+_evdns_log(int warn, const char *fmt, ...)
+{
+	va_list args;
+	char buf[512];
+	if (!evdns_log_fn)
+		return;
+	va_start(args,fmt);
+	evutil_vsnprintf(buf, sizeof(buf), fmt, args);
+	va_end(args);
+	if (evdns_log_fn) {
+		if (warn == EVDNS_LOG_MSG)
+			warn = EVDNS_LOG_WARN;
+		evdns_log_fn(warn, buf);
+	} else {
+		default_evdns_log_fn(warn, buf);
+	}
+}
+#define log _evdns_log
+/* This walks the list of inflight requests to find the */
+/* one with a matching transaction id. Returns NULL on */
+/* failure */
+static struct request *
+request_find_from_trans_id(struct evdns_base *base, u16 trans_id) {
+	struct request *req = REQ_HEAD(base, trans_id);
+	struct request *const started_at = req;
+	ASSERT_LOCKED(base);
+	if (req) {
+		do {
+			if (req->trans_id == trans_id) return req;
+			req = req->next;
+		} while (req != started_at);
+	}
+	return NULL;
+}
+/* a libevent callback function which is called when a nameserver */
+/* has gone down and we want to test if it has came back to life yet */
+static void
+nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) {
+	struct nameserver *const ns = (struct nameserver *) arg;
+	(void)fd;
+	(void)events;
+	EVDNS_LOCK(ns->base);
+	nameserver_send_probe(ns);
+	EVDNS_UNLOCK(ns->base);
+}
+/* a libevent callback which is called when a nameserver probe (to see if */
+/* it has come back to life) times out. We increment the count of failed_times */
+/* and wait longer to send the next probe packet. */
+static void
+nameserver_probe_failed(struct nameserver *const ns) {
+	struct timeval timeout;
+	int i;
+	ASSERT_LOCKED(ns->base);
+	(void) evtimer_del(&ns->timeout_event);
+	if (ns->state == 1) {
+		/* This can happen if the nameserver acts in a way which makes us mark */
+		/* it as bad and then starts sending good replies. */
+		return;
+	}
+#define MAX_PROBE_TIMEOUT 3600
+#define TIMEOUT_BACKOFF_FACTOR 3
+	memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout,
+	    sizeof(struct timeval));
+	for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) {
+		timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR;
+		timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR;
+		if (timeout.tv_usec > 1000000) {
+			timeout.tv_sec += timeout.tv_usec / 1000000;
+			timeout.tv_usec %= 1000000;
+		}
+	}
+	if (timeout.tv_sec > MAX_PROBE_TIMEOUT) {
+		timeout.tv_sec = MAX_PROBE_TIMEOUT;
+		timeout.tv_usec = 0;
+	}
+	ns->failed_times++;
+	if (evtimer_add(&ns->timeout_event, &timeout) < 0) {
+		char addrbuf[128];
+		log(EVDNS_LOG_WARN,
+		    "Error from libevent when adding timer event for %s",
+		    evutil_format_sockaddr_port(
+			    (struct sockaddr *)&ns->address,
+			    addrbuf, sizeof(addrbuf)));
+	}
+}
+/* called when a nameserver has been deemed to have failed. For example, too */
+/* many packets have timed out etc */
+static void
+nameserver_failed(struct nameserver *const ns, const char *msg) {
+	struct request *req, *started_at;
+	struct evdns_base *base = ns->base;
+	int i;
+	char addrbuf[128];
+	ASSERT_LOCKED(base);
+	/* if this nameserver has already been marked as failed */
+	/* then don't do anything */
+	if (!ns->state) return;
+	log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s",
+	    evutil_format_sockaddr_port(
+		    (struct sockaddr *)&ns->address,
+		    addrbuf, sizeof(addrbuf)),
+	    msg);
+	base->global_good_nameservers--;
+	EVUTIL_ASSERT(base->global_good_nameservers >= 0);
+	if (base->global_good_nameservers == 0) {
+		log(EVDNS_LOG_MSG, "All nameservers have failed");
+	}
+	ns->state = 0;
+	ns->failed_times = 1;
+	if (evtimer_add(&ns->timeout_event,
+		&base->global_nameserver_probe_initial_timeout) < 0) {
+		log(EVDNS_LOG_WARN,
+		    "Error from libevent when adding timer event for %s",
+		    evutil_format_sockaddr_port(
+			    (struct sockaddr *)&ns->address,
+			    addrbuf, sizeof(addrbuf)));
+		/* ???? Do more? */
+	}
+	/* walk the list of inflight requests to see if any can be reassigned to */
+	/* a different server. Requests in the waiting queue don't have a */
+	/* nameserver assigned yet */
+	/* if we don't have *any* good nameservers then there's no point */
+	/* trying to reassign requests to one */
+	if (!base->global_good_nameservers) return;
+	for (i = 0; i < base->n_req_heads; ++i) {
+		req = started_at = base->req_heads[i];
+		if (req) {
+			do {
+				if (req->tx_count == 0 && req->ns == ns) {
+					/* still waiting to go out, can be moved */
+					/* to another server */
+					req->ns = nameserver_pick(base);
+				}
+				req = req->next;
+			} while (req != started_at);
+		}
+	}
+}
+static void
+nameserver_up(struct nameserver *const ns)
+{
+	char addrbuf[128];
+	ASSERT_LOCKED(ns->base);
+	if (ns->state) return;
+	log(EVDNS_LOG_MSG, "Nameserver %s is back up",
+	    evutil_format_sockaddr_port(
+		    (struct sockaddr *)&ns->address,
+		    addrbuf, sizeof(addrbuf)));
+	evtimer_del(&ns->timeout_event);
+	if (ns->probe_request) {
+		evdns_cancel_request(ns->base, ns->probe_request);
+		ns->probe_request = NULL;
+	}
+	ns->state = 1;
+	ns->failed_times = 0;
+	ns->timedout = 0;
+	ns->base->global_good_nameservers++;
+}
+static void
+request_trans_id_set(struct request *const req, const u16 trans_id) {
+	req->trans_id = trans_id;
+	*((u16 *) req->request) = htons(trans_id);
+}
+/* Called to remove a request from a list and dealloc it. */
+/* head is a pointer to the head of the list it should be */
+/* removed from or NULL if the request isn't in a list. */
+/* when free_handle is one, free the handle as well. */
+static void
+request_finished(struct request *const req, struct request **head, int free_handle) {
+	struct evdns_base *base = req->base;
+	int was_inflight = (head != &base->req_waiting_head);
+	EVDNS_LOCK(base);
+	ASSERT_VALID_REQUEST(req);
+	if (head)
+		evdns_request_remove(req, head);
+	log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req);
+	if (was_inflight) {
+		evtimer_del(&req->timeout_event);
+		base->global_requests_inflight--;
+	} else {
+		base->global_requests_waiting--;
+	}
+	/* it was initialized during request_new / evtimer_assign */
+	event_debug_unassign(&req->timeout_event);
+	if (!req->request_appended) {
+		/* need to free the request data on it's own */
+		mm_free(req->request);
+	} else {
+		/* the request data is appended onto the header */
+		/* so everything gets free()ed when we: */
+	}
+	if (req->handle) {
+		EVUTIL_ASSERT(req->handle->current_req == req);
+		if (free_handle) {
+			search_request_finished(req->handle);
+			req->handle->current_req = NULL;
+			if (! req->handle->pending_cb) {
+				/* If we're planning to run the callback,
+				 * don't free the handle until later. */
+				mm_free(req->handle);
+			}
+			req->handle = NULL; /* If we have a bug, let's crash
+					     * early */
+		} else {
+			req->handle->current_req = NULL;
+		}
+	}
+	mm_free(req);
+	evdns_requests_pump_waiting_queue(base);
+	EVDNS_UNLOCK(base);
+}
+/* This is called when a server returns a funny error code. */
+/* We try the request again with another server. */
+/* */
+/* return: */
+/*   0 ok */
+/*   1 failed/reissue is pointless */
+static int
+request_reissue(struct request *req) {
+	const struct nameserver *const last_ns = req->ns;
+	ASSERT_LOCKED(req->base);
+	ASSERT_VALID_REQUEST(req);
+	/* the last nameserver should have been marked as failing */
+	/* by the caller of this function, therefore pick will try */
+	/* not to return it */
+	req->ns = nameserver_pick(req->base);
+	if (req->ns == last_ns) {
+		/* ... but pick did return it */
+		/* not a lot of point in trying again with the */
+		/* same server */
+		return 1;
+	}
+	req->reissue_count++;
+	req->tx_count = 0;
+	req->transmit_me = 1;
+	return 0;
+}
+/* this function looks for space on the inflight queue and promotes */
+/* requests from the waiting queue if it can. */
+static void
+evdns_requests_pump_waiting_queue(struct evdns_base *base) {
+	ASSERT_LOCKED(base);
+	while (base->global_requests_inflight < base->global_max_requests_inflight &&
+		   base->global_requests_waiting) {
+		struct request *req;
+		/* move a request from the waiting queue to the inflight queue */
+		EVUTIL_ASSERT(base->req_waiting_head);
+		req = base->req_waiting_head;
+		evdns_request_remove(req, &base->req_waiting_head);
+		base->global_requests_waiting--;
+		base->global_requests_inflight++;
+		req->ns = nameserver_pick(base);
+		request_trans_id_set(req, transaction_id_pick(base));
+		evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
+		evdns_request_transmit(req);
+		evdns_transmit(base);
+	}
+}
+/* TODO(nickm) document */
+struct deferred_reply_callback {
+	struct deferred_cb deferred;
+	struct evdns_request *handle;
+	u8 request_type;
+	u8 have_reply;
+	u32 ttl;
+	u32 err;
+	evdns_callback_type user_callback;
+	struct reply reply;
+};
+static void
+reply_run_callback(struct deferred_cb *d, void *user_pointer)
+{
+	struct deferred_reply_callback *cb =
+	    EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred);
+	switch (cb->request_type) {
+	case TYPE_A:
+		if (cb->have_reply)
+			cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
+			    cb->reply.data.a.addrcount, cb->ttl,
+			    cb->reply.data.a.addresses,
+			    user_pointer);
+		else
+			cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
+		break;
+	case TYPE_PTR:
+		if (cb->have_reply) {
+			char *name = cb->reply.data.ptr.name;
+			cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl,
+			    &name, user_pointer);
+		} else {
+			cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
+		}
+		break;
+	case TYPE_AAAA:
+		if (cb->have_reply)
+			cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA,
+			    cb->reply.data.aaaa.addrcount, cb->ttl,
+			    cb->reply.data.aaaa.addresses,
+			    user_pointer);
+		else
+			cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
+		break;
+	default:
+		EVUTIL_ASSERT(0);
+	}
+	if (cb->handle && cb->handle->pending_cb) {
+		mm_free(cb->handle);
+	}
+	mm_free(cb);
+}
+static void
+reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply)
+{
+	struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d));
+	if (!d) {
+		event_warn("%s: Couldn't allocate space for deferred callback.",
+		    __func__);
+		return;
+	}
+	ASSERT_LOCKED(req->base);
+	d->request_type = req->request_type;
+	d->user_callback = req->user_callback;
+	d->ttl = ttl;
+	d->err = err;
+	if (reply) {
+		d->have_reply = 1;
+		memcpy(&d->reply, reply, sizeof(struct reply));
+	}
+	if (req->handle) {
+		req->handle->pending_cb = 1;
+		d->handle = req->handle;
+	}
+	event_deferred_cb_init(&d->deferred, reply_run_callback,
+	    req->user_pointer);
+	event_deferred_cb_schedule(
+		event_base_get_deferred_cb_queue(req->base->event_base),
+		&d->deferred);
+}
+/* this processes a parsed reply packet */
+static void
+reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) {
+	int error;
+	char addrbuf[128];
+	static const int error_codes[] = {
+		DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST,
+		DNS_ERR_NOTIMPL, DNS_ERR_REFUSED
+	};
+	ASSERT_LOCKED(req->base);
+	ASSERT_VALID_REQUEST(req);
+	if (flags & 0x020f || !reply || !reply->have_answer) {
+		/* there was an error */
+		if (flags & 0x0200) {
+			error = DNS_ERR_TRUNCATED;
+		} else if (flags & 0x000f) {
+			u16 error_code = (flags & 0x000f) - 1;
+			if (error_code > 4) {
+				error = DNS_ERR_UNKNOWN;
+			} else {
+				error = error_codes[error_code];
+			}
+		} else if (reply && !reply->have_answer) {
+			error = DNS_ERR_NODATA;
+		} else {
+			error = DNS_ERR_UNKNOWN;
+		}
+		switch (error) {
+		case DNS_ERR_NOTIMPL:
+		case DNS_ERR_REFUSED:
+			/* we regard these errors as marking a bad nameserver */
+			if (req->reissue_count < req->base->global_max_reissues) {
+				char msg[64];
+				evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)",
+					 error, evdns_err_to_string(error));
+				nameserver_failed(req->ns, msg);
+				if (!request_reissue(req)) return;
+			}
+			break;
+		case DNS_ERR_SERVERFAILED:
+			/* rcode 2 (servfailed) sometimes means "we
+			 * are broken" and sometimes (with some binds)
+			 * means "that request was very confusing."
+			 * Treat this as a timeout, not a failure.
+			 */
+			log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver"
+				"at %s; will allow the request to time out.",
+			    evutil_format_sockaddr_port(
+				    (struct sockaddr *)&req->ns->address,
+				    addrbuf, sizeof(addrbuf)));
+			break;
+		default:
+			/* we got a good reply from the nameserver: it is up. */
+			if (req->handle == req->ns->probe_request) {
+				/* Avoid double-free */
+				req->ns->probe_request = NULL;
+			}
+			nameserver_up(req->ns);
+		}
+		if (req->handle->search_state &&
+		    req->request_type != TYPE_PTR) {
+			/* if we have a list of domains to search in,
+			 * try the next one */
+			if (!search_try_next(req->handle)) {
+				/* a new request was issued so this
+				 * request is finished and */
+				/* the user callback will be made when
+				 * that request (or a */
+				/* child of it) finishes. */
+				return;
+			}
+		}
+		/* all else failed. Pass the failure up */
+		reply_schedule_callback(req, ttl, error, NULL);
+		request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
+	} else {
+		/* all ok, tell the user */
+		reply_schedule_callback(req, ttl, 0, reply);
+		if (req->handle == req->ns->probe_request)
+			req->ns->probe_request = NULL; /* Avoid double-free */
+		nameserver_up(req->ns);
+		request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
+	}
+}
+static int
+name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) {
+	int name_end = -1;
+	int j = *idx;
+	int ptr_count = 0;
+#define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while (0)
+#define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while (0)
+#define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0)
+	char *cp = name_out;
+	const char *const end = name_out + name_out_len;
+	/* Normally, names are a series of length prefixed strings terminated */
+	/* with a length of 0 (the lengths are u8's < 63). */
+	/* However, the length can start with a pair of 1 bits and that */
+	/* means that the next 14 bits are a pointer within the current */
+	/* packet. */
+	for (;;) {
+		u8 label_len;
+		if (j >= length) return -1;
+		GET8(label_len);
+		if (!label_len) break;
+		if (label_len & 0xc0) {
+			u8 ptr_low;
+			GET8(ptr_low);
+			if (name_end < 0) name_end = j;
+			j = (((int)label_len & 0x3f) << 8) + ptr_low;
+			/* Make sure that the target offset is in-bounds. */
+			if (j < 0 || j >= length) return -1;
+			/* If we've jumped more times than there are characters in the
+			 * message, we must have a loop. */
+			if (++ptr_count > length) return -1;
+			continue;
+		}
+		if (label_len > 63) return -1;
+		if (cp != name_out) {
+			if (cp + 1 >= end) return -1;
+			*cp++ = '.';
+		}
+		if (cp + label_len >= end) return -1;
+		memcpy(cp, packet + j, label_len);
+		cp += label_len;
+		j += label_len;
+	}
+	if (cp >= end) return -1;
+	*cp = '\0';
+	if (name_end < 0)
+		*idx = j;
+	else
+		*idx = name_end;
+	return 0;
+err:
+	return -1;
+}
+/* parses a raw request from a nameserver */
+static int
+reply_parse(struct evdns_base *base, u8 *packet, int length) {
+	int j = 0, k = 0;  /* index into packet */
+	u16 _t;	 /* used by the macros */
+	u32 _t32;  /* used by the macros */
+	char tmp_name[256], cmp_name[256]; /* used by the macros */
+	int name_matches = 0;
+	u16 trans_id, questions, answers, authority, additional, datalength;
+	u16 flags = 0;
+	u32 ttl, ttl_r = 0xffffffff;
+	struct reply reply;
+	struct request *req = NULL;
+	unsigned int i;
+	ASSERT_LOCKED(base);
+	GET16(trans_id);
+	GET16(flags);
+	GET16(questions);
+	GET16(answers);
+	GET16(authority);
+	GET16(additional);
+	(void) authority; /* suppress "unused variable" warnings. */
+	(void) additional; /* suppress "unused variable" warnings. */
+	req = request_find_from_trans_id(base, trans_id);
+	if (!req) return -1;
+	EVUTIL_ASSERT(req->base == base);
+	memset(&reply, 0, sizeof(reply));
+	/* If it's not an answer, it doesn't correspond to any request. */
+	if (!(flags & 0x8000)) return -1;  /* must be an answer */
+	if ((flags & 0x020f) && (flags & 0x020f) != DNS_ERR_NOTEXIST) {
+		/* there was an error and it's not NXDOMAIN */
+		goto err;
+	}
+	/* if (!answers) return; */  /* must have an answer of some form */
+	/* This macro skips a name in the DNS reply. */
+#define SKIP_NAME						\
+	do { tmp_name[0] = '\0';				\
+		if (name_parse(packet, length, &j, tmp_name,	\
+			sizeof(tmp_name))<0)			\
+			goto err;				\
+	} while (0)
+#define TEST_NAME							\
+	do { tmp_name[0] = '\0';					\
+		cmp_name[0] = '\0';					\
+		k = j;							\
+		if (name_parse(packet, length, &j, tmp_name,		\
+			sizeof(tmp_name))<0)				\
+			goto err;					\
+		if (name_parse(req->request, req->request_len, &k,	\
+			cmp_name, sizeof(cmp_name))<0)			\
+			goto err;					\
+		if (base->global_randomize_case) {			\
+			if (strcmp(tmp_name, cmp_name) == 0)		\
+				name_matches = 1;			\
+		} else {						\
+			if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0) \
+				name_matches = 1;			\
+		}							\
+	} while (0)
+	reply.type = req->request_type;
+	/* skip over each question in the reply */
+	for (i = 0; i < questions; ++i) {
+		/* the question looks like
+		 *   <label:name><u16:type><u16:class>
+		 */
+		TEST_NAME;
+		j += 4;
+		if (j > length) goto err;
+	}
+	if (!name_matches)
+		goto err;
+	/* now we have the answer section which looks like
+	 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...>
+	 */
+	for (i = 0; i < answers; ++i) {
+		u16 type, class;
+		SKIP_NAME;
+		GET16(type);
+		GET16(class);
+		GET32(ttl);
+		GET16(datalength);
+		if (type == TYPE_A && class == CLASS_INET) {
+			int addrcount, addrtocopy;
+			if (req->request_type != TYPE_A) {
+				j += datalength; continue;
+			}
+			if ((datalength & 3) != 0) /* not an even number of As. */
+			    goto err;
+			addrcount = datalength >> 2;
+			addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount);
+			ttl_r = MIN(ttl_r, ttl);
+			/* we only bother with the first four addresses. */
+			if (j + 4*addrtocopy > length) goto err;
+			memcpy(&reply.data.a.addresses[reply.data.a.addrcount],
+				   packet + j, 4*addrtocopy);
+			j += 4*addrtocopy;
+			reply.data.a.addrcount += addrtocopy;
+			reply.have_answer = 1;
+			if (reply.data.a.addrcount == MAX_V4_ADDRS) break;
+		} else if (type == TYPE_PTR && class == CLASS_INET) {
+			if (req->request_type != TYPE_PTR) {
+				j += datalength; continue;
+			}
+			if (name_parse(packet, length, &j, reply.data.ptr.name,
+						   sizeof(reply.data.ptr.name))<0)
+				goto err;
+			ttl_r = MIN(ttl_r, ttl);
+			reply.have_answer = 1;
+			break;
+		} else if (type == TYPE_CNAME) {
+			char cname[HOST_NAME_MAX];
+			if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) {
+				j += datalength; continue;
+			}
+			if (name_parse(packet, length, &j, cname,
+				sizeof(cname))<0)
+				goto err;
+			*req->put_cname_in_ptr = mm_strdup(cname);
+		} else if (type == TYPE_AAAA && class == CLASS_INET) {
+			int addrcount, addrtocopy;
+			if (req->request_type != TYPE_AAAA) {
+				j += datalength; continue;
+			}
+			if ((datalength & 15) != 0) /* not an even number of AAAAs. */
+				goto err;
+			addrcount = datalength >> 4;  /* each address is 16 bytes long */
+			addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount);
+			ttl_r = MIN(ttl_r, ttl);
+			/* we only bother with the first four addresses. */
+			if (j + 16*addrtocopy > length) goto err;
+			memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount],
+				   packet + j, 16*addrtocopy);
+			reply.data.aaaa.addrcount += addrtocopy;
+			j += 16*addrtocopy;
+			reply.have_answer = 1;
+			if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break;
+		} else {
+			/* skip over any other type of resource */
+			j += datalength;
+		}
+	}
+	if (!reply.have_answer) {
+		for (i = 0; i < authority; ++i) {
+			u16 type, class;
+			SKIP_NAME;
+			GET16(type);
+			GET16(class);
+			GET32(ttl);
+			GET16(datalength);
+			if (type == TYPE_SOA && class == CLASS_INET) {
+				u32 serial, refresh, retry, expire, minimum;
+				SKIP_NAME;
+				SKIP_NAME;
+				GET32(serial);
+				GET32(refresh);
+				GET32(retry);
+				GET32(expire);
+				GET32(minimum);
+				(void)expire;
+				(void)retry;
+				(void)refresh;
+				(void)serial;
+				ttl_r = MIN(ttl_r, ttl);
+				ttl_r = MIN(ttl_r, minimum);
+			} else {
+				/* skip over any other type of resource */
+				j += datalength;
+			}
+		}
+	}
+	if (ttl_r == 0xffffffff)
+		ttl_r = 0;
+	reply_handle(req, flags, ttl_r, &reply);
+	return 0;
+err:
+	if (req)
+		reply_handle(req, flags, 0, NULL);
+	return -1;
+}
+/* Parse a raw request (packet,length) sent to a nameserver port (port) from */
+/* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */
+/* callback. */
+static int
+request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen)
+{
+	int j = 0;	/* index into packet */
+	u16 _t;	 /* used by the macros */
+	char tmp_name[256]; /* used by the macros */
+	int i;
+	u16 trans_id, flags, questions, answers, authority, additional;
+	struct server_request *server_req = NULL;
+	ASSERT_LOCKED(port);
+	/* Get the header fields */
+	GET16(trans_id);
+	GET16(flags);
+	GET16(questions);
+	GET16(answers);
+	GET16(authority);
+	GET16(additional);
+	(void)answers;
+	(void)additional;
+	(void)authority;
+	if (flags & 0x8000) return -1; /* Must not be an answer. */
+	flags &= 0x0110; /* Only RD and CD get preserved. */
+	server_req = mm_malloc(sizeof(struct server_request));
+	if (server_req == NULL) return -1;
+	memset(server_req, 0, sizeof(struct server_request));
+	server_req->trans_id = trans_id;
+	memcpy(&server_req->addr, addr, addrlen);
+	server_req->addrlen = addrlen;
+	server_req->base.flags = flags;
+	server_req->base.nquestions = 0;
+	server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions);
+	if (server_req->base.questions == NULL)
+		goto err;
+	for (i = 0; i < questions; ++i) {
+		u16 type, class;
+		struct evdns_server_question *q;
+		int namelen;
+		if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)
+			goto err;
+		GET16(type);
+		GET16(class);
+		namelen = (int)strlen(tmp_name);
+		q = mm_malloc(sizeof(struct evdns_server_question) + namelen);
+		if (!q)
+			goto err;
+		q->type = type;
+		q->dns_question_class = class;
+		memcpy(q->name, tmp_name, namelen+1);
+		server_req->base.questions[server_req->base.nquestions++] = q;
+	}
+	/* Ignore answers, authority, and additional. */
+	server_req->port = port;
+	port->refcnt++;
+	/* Only standard queries are supported. */
+	if (flags & 0x7800) {
+		evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL);
+		return -1;
+	}
+	port->user_callback(&(server_req->base), port->user_data);
+	return 0;
+err:
+	if (server_req) {
+		if (server_req->base.questions) {
+			for (i = 0; i < server_req->base.nquestions; ++i)
+				mm_free(server_req->base.questions[i]);
+			mm_free(server_req->base.questions);
+		}
+		mm_free(server_req);
+	}
+	return -1;
+#undef SKIP_NAME
+#undef GET32
+#undef GET16
+#undef GET8
+}
+void
+evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void))
+{
+}
+void
+evdns_set_random_bytes_fn(void (*fn)(char *, size_t))
+{
+}
+/* Try to choose a strong transaction id which isn't already in flight */
+static u16
+transaction_id_pick(struct evdns_base *base) {
+	ASSERT_LOCKED(base);
+	for (;;) {
+		u16 trans_id;
+		evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id));
+		if (trans_id == 0xffff) continue;
+		/* now check to see if that id is already inflight */
+		if (request_find_from_trans_id(base, trans_id) == NULL)
+			return trans_id;
+	}
+}
+/* choose a namesever to use. This function will try to ignore */
+/* nameservers which we think are down and load balance across the rest */
+/* by updating the server_head global each time. */
+static struct nameserver *
+nameserver_pick(struct evdns_base *base) {
+	struct nameserver *started_at = base->server_head, *picked;
+	ASSERT_LOCKED(base);
+	if (!base->server_head) return NULL;
+	/* if we don't have any good nameservers then there's no */
+	/* point in trying to find one. */
+	if (!base->global_good_nameservers) {
+		base->server_head = base->server_head->next;
+		return base->server_head;
+	}
+	/* remember that nameservers are in a circular list */
+	for (;;) {
+		if (base->server_head->state) {
+			/* we think this server is currently good */
+			picked = base->server_head;
+			base->server_head = base->server_head->next;
+			return picked;
+		}
+		base->server_head = base->server_head->next;
+		if (base->server_head == started_at) {
+			/* all the nameservers seem to be down */
+			/* so we just return this one and hope for the */
+			/* best */
+			EVUTIL_ASSERT(base->global_good_nameservers == 0);
+			picked = base->server_head;
+			base->server_head = base->server_head->next;
+			return picked;
+		}
+	}
+}
+/* this is called when a namesever socket is ready for reading */
+static void
+nameserver_read(struct nameserver *ns) {
+	struct sockaddr_storage ss;
+	ev_socklen_t addrlen = sizeof(ss);
+	u8 packet[1500];
+	char addrbuf[128];
+	ASSERT_LOCKED(ns->base);
+	for (;;) {
+		const int r = recvfrom(ns->socket, (void*)packet,
+		    sizeof(packet), 0,
+		    (struct sockaddr*)&ss, &addrlen);
+		if (r < 0) {
+			int err = evutil_socket_geterror(ns->socket);
+			if (EVUTIL_ERR_RW_RETRIABLE(err))
+				return;
+			nameserver_failed(ns,
+			    evutil_socket_error_to_string(err));
+			return;
+		}
+		if (evutil_sockaddr_cmp((struct sockaddr*)&ss,
+			(struct sockaddr*)&ns->address, 0)) {
+			log(EVDNS_LOG_WARN, "Address mismatch on received "
+			    "DNS packet.  Apparent source was %s",
+			    evutil_format_sockaddr_port(
+				    (struct sockaddr *)&ss,
+				    addrbuf, sizeof(addrbuf)));
+			return;
+		}
+		ns->timedout = 0;
+		reply_parse(ns->base, packet, r);
+	}
+}
+/* Read a packet from a DNS client on a server port s, parse it, and */
+/* act accordingly. */
+static void
+server_port_read(struct evdns_server_port *s) {
+	u8 packet[1500];
+	struct sockaddr_storage addr;
+	ev_socklen_t addrlen;
+	int r;
+	ASSERT_LOCKED(s);
+	for (;;) {
+		addrlen = sizeof(struct sockaddr_storage);
+		r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0,
+					 (struct sockaddr*) &addr, &addrlen);
+		if (r < 0) {
+			int err = evutil_socket_geterror(s->socket);
+			if (EVUTIL_ERR_RW_RETRIABLE(err))
+				return;
+			log(EVDNS_LOG_WARN,
+			    "Error %s (%d) while reading request.",
+			    evutil_socket_error_to_string(err), err);
+			return;
+		}
+		request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen);
+	}
+}
+/* Try to write all pending replies on a given DNS server port. */
+static void
+server_port_flush(struct evdns_server_port *port)
+{
+	struct server_request *req = port->pending_replies;
+	ASSERT_LOCKED(port);
+	while (req) {
+		int r = sendto(port->socket, req->response, (int)req->response_len, 0,
+			   (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen);
+		if (r < 0) {
+			int err = evutil_socket_geterror(port->socket);
+			if (EVUTIL_ERR_RW_RETRIABLE(err))
+				return;
+			log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err);
+		}
+		if (server_request_free(req)) {
+			/* we released the last reference to req->port. */
+			return;
+		} else {
+			EVUTIL_ASSERT(req != port->pending_replies);
+			req = port->pending_replies;
+		}
+	}
+	/* We have no more pending requests; stop listening for 'writeable' events. */
+	(void) event_del(&port->event);
+	event_assign(&port->event, port->event_base,
+				 port->socket, EV_READ | EV_PERSIST,
+				 server_port_ready_callback, port);
+	if (event_add(&port->event, NULL) < 0) {
+		log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server.");
+		/* ???? Do more? */
+	}
+}
+/* set if we are waiting for the ability to write to this server. */
+/* if waiting is true then we ask libevent for EV_WRITE events, otherwise */
+/* we stop these events. */
+static void
+nameserver_write_waiting(struct nameserver *ns, char waiting) {
+	ASSERT_LOCKED(ns->base);
+	if (ns->write_waiting == waiting) return;
+	ns->write_waiting = waiting;
+	(void) event_del(&ns->event);
+	event_assign(&ns->event, ns->base->event_base,
+	    ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST,
+	    nameserver_ready_callback, ns);
+	if (event_add(&ns->event, NULL) < 0) {
+		char addrbuf[128];
+		log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s",
+		    evutil_format_sockaddr_port(
+			    (struct sockaddr *)&ns->address,
+			    addrbuf, sizeof(addrbuf)));
+		/* ???? Do more? */
+	}
+}
+/* a callback function. Called by libevent when the kernel says that */
+/* a nameserver socket is ready for writing or reading */
+static void
+nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) {
+	struct nameserver *ns = (struct nameserver *) arg;
+	(void)fd;
+	EVDNS_LOCK(ns->base);
+	if (events & EV_WRITE) {
+		ns->choked = 0;
+		if (!evdns_transmit(ns->base)) {
+			nameserver_write_waiting(ns, 0);
+		}
+	}
+	if (events & EV_READ) {
+		nameserver_read(ns);
+	}
+	EVDNS_UNLOCK(ns->base);
+}
+/* a callback function. Called by libevent when the kernel says that */
+/* a server socket is ready for writing or reading. */
+static void
+server_port_ready_callback(evutil_socket_t fd, short events, void *arg) {
+	struct evdns_server_port *port = (struct evdns_server_port *) arg;
+	(void) fd;
+	EVDNS_LOCK(port);
+	if (events & EV_WRITE) {
+		port->choked = 0;
+		server_port_flush(port);
+	}
+	if (events & EV_READ) {
+		server_port_read(port);
+	}
+	EVDNS_UNLOCK(port);
+}
+/* This is an inefficient representation; only use it via the dnslabel_table_*
+* functions, so that is can be safely replaced with something smarter later. */
+#define MAX_LABELS 128
+/* Structures used to implement name compression */
+struct dnslabel_entry { char *v; off_t pos; };
+struct dnslabel_table {
+	int n_labels; /* number of current entries */
+	/* map from name to position in message */
+	struct dnslabel_entry labels[MAX_LABELS];
+};
+/* Initialize dnslabel_table. */
+static void
+dnslabel_table_init(struct dnslabel_table *table)
+{
+	table->n_labels = 0;
+}
+/* Free all storage held by table, but not the table itself. */
+static void
+dnslabel_clear(struct dnslabel_table *table)
+{
+	int i;
+	for (i = 0; i < table->n_labels; ++i)
+		mm_free(table->labels[i].v);
+	table->n_labels = 0;
+}
+/* return the position of the label in the current message, or -1 if the label */
+/* hasn't been used yet. */
+static int
+dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label)
+{
+	int i;
+	for (i = 0; i < table->n_labels; ++i) {
+		if (!strcmp(label, table->labels[i].v))
+			return table->labels[i].pos;
+	}
+	return -1;
+}
+/* remember that we've used the label at position pos */
+static int
+dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos)
+{
+	char *v;
+	int p;
+	if (table->n_labels == MAX_LABELS)
+		return (-1);
+	v = mm_strdup(label);
+	if (v == NULL)
+		return (-1);
+	p = table->n_labels++;
+	table->labels[p].v = v;
+	table->labels[p].pos = pos;
+	return (0);
+}
+/* Converts a string to a length-prefixed set of DNS labels, starting */
+/* at buf[j]. name and buf must not overlap. name_len should be the length */
+/* of name.	 table is optional, and is used for compression. */
+/* */
+/* Input: abc.def */
+/* Output: <3>abc<3>def<0> */
+/* */
+/* Returns the first index after the encoded name, or negative on error. */
+/*	 -1	 label was > 63 bytes */
+/*	 -2	 name too long to fit in buffer. */
+/* */
+static off_t
+dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
+				  const char *name, const size_t name_len,
+				  struct dnslabel_table *table) {
+	const char *end = name + name_len;
+	int ref = 0;
+	u16 _t;
+#define APPEND16(x) do {						\
+		if (j + 2 > (off_t)buf_len)				\
+			goto overflow;					\
+		_t = htons(x);						\
+		memcpy(buf + j, &_t, 2);				\
+		j += 2;							\
+	} while (0)
+#define APPEND32(x) do {						\
+		if (j + 4 > (off_t)buf_len)				\
+			goto overflow;					\
+		_t32 = htonl(x);					\
+		memcpy(buf + j, &_t32, 4);				\
+		j += 4;							\
+	} while (0)
+	if (name_len > 255) return -2;
+	for (;;) {
+		const char *const start = name;
+		if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) {
+			APPEND16(ref | 0xc000);
+			return j;
+		}
+		name = strchr(name, '.');
+		if (!name) {
+			const size_t label_len = end - start;
+			if (label_len > 63) return -1;
+			if ((size_t)(j+label_len+1) > buf_len) return -2;
+			if (table) dnslabel_table_add(table, start, j);
+			buf[j++] = (ev_uint8_t)label_len;
+			memcpy(buf + j, start, label_len);
+			j += (int) label_len;
+			break;
+		} else {
+			/* append length of the label. */
+			const size_t label_len = name - start;
+			if (label_len > 63) return -1;
+			if ((size_t)(j+label_len+1) > buf_len) return -2;
+			if (table) dnslabel_table_add(table, start, j);
+			buf[j++] = (ev_uint8_t)label_len;
+			memcpy(buf + j, start, label_len);
+			j += (int) label_len;
+			/* hop over the '.' */
+			name++;
+		}
+	}
+	/* the labels must be terminated by a 0. */
+	/* It's possible that the name ended in a . */
+	/* in which case the zero is already there */
+	if (!j || buf[j-1]) buf[j++] = 0;
+	return j;
+overflow:
+	return (-2);
+}
+/* Finds the length of a dns request for a DNS name of the given */
+/* length. The actual request may be smaller than the value returned */
+/* here */
+static size_t
+evdns_request_len(const size_t name_len) {
+	return 96 + /* length of the DNS standard header */
+		name_len + 2 +
+		4;  /* space for the resource type */
+}
+/* build a dns request packet into buf. buf should be at least as long */
+/* as evdns_request_len told you it should be. */
+/* */
+/* Returns the amount of space used. Negative on error. */
+static int
+evdns_request_data_build(const char *const name, const size_t name_len,
+const u16 trans_id, const u16 type, const u16 class,
+u8 *const buf, size_t buf_len) {
+	off_t j = 0;  /* current offset into buf */
+	u16 _t;	 /* used by the macros */
+	APPEND16(trans_id);
+	APPEND16(0x0100);  /* standard query, recusion needed */
+	APPEND16(1);  /* one question */
+	APPEND16(0);  /* no answers */
+	APPEND16(0);  /* no authority */
+	APPEND16(0);  /* no additional */
+	j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL);
+	if (j < 0) {
+		return (int)j;
+	}
+	APPEND16(type);
+	APPEND16(class);
+	return (int)j;
+overflow:
+	return (-1);
+}
+/* exported function */
+struct evdns_server_port *
+evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data)
+{
+	struct evdns_server_port *port;
+	if (flags)
+		return NULL; /* flags not yet implemented */
+	if (!(port = mm_malloc(sizeof(struct evdns_server_port))))
+		return NULL;
+	memset(port, 0, sizeof(struct evdns_server_port));
+	port->socket = socket;
+	port->refcnt = 1;
+	port->choked = 0;
+	port->closing = 0;
+	port->user_callback = cb;
+	port->user_data = user_data;
+	port->pending_replies = NULL;
+	port->event_base = base;
+	event_assign(&port->event, port->event_base,
+				 port->socket, EV_READ | EV_PERSIST,
+				 server_port_ready_callback, port);
+	if (event_add(&port->event, NULL) < 0) {
+		mm_free(port);
+		return NULL;
+	}
+	EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	return port;
+}
+struct evdns_server_port *
+evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data)
+{
+	return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data);
+}
+/* exported function */
+void
+evdns_close_server_port(struct evdns_server_port *port)
+{
+	EVDNS_LOCK(port);
+	if (--port->refcnt == 0) {
+		EVDNS_UNLOCK(port);
+		server_port_free(port);
+	} else {
+		port->closing = 1;
+	}
+}
+/* exported function */
+int
+evdns_server_request_add_reply(struct evdns_server_request *_req, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data)
+{
+	struct server_request *req = TO_SERVER_REQUEST(_req);
+	struct server_reply_item **itemp, *item;
+	int *countp;
+	int result = -1;
+	EVDNS_LOCK(req->port);
+	if (req->response) /* have we already answered? */
+		goto done;
+	switch (section) {
+	case EVDNS_ANSWER_SECTION:
+		itemp = &req->answer;
+		countp = &req->n_answer;
+		break;
+	case EVDNS_AUTHORITY_SECTION:
+		itemp = &req->authority;
+		countp = &req->n_authority;
+		break;
+	case EVDNS_ADDITIONAL_SECTION:
+		itemp = &req->additional;
+		countp = &req->n_additional;
+		break;
+	default:
+		goto done;
+	}
+	while (*itemp) {
+		itemp = &((*itemp)->next);
+	}
+	item = mm_malloc(sizeof(struct server_reply_item));
+	if (!item)
+		goto done;
+	item->next = NULL;
+	if (!(item->name = mm_strdup(name))) {
+		mm_free(item);
+		goto done;
+	}
+	item->type = type;
+	item->dns_question_class = class;
+	item->ttl = ttl;
+	item->is_name = is_name != 0;
+	item->datalen = 0;
+	item->data = NULL;
+	if (data) {
+		if (item->is_name) {
+			if (!(item->data = mm_strdup(data))) {
+				mm_free(item->name);
+				mm_free(item);
+				goto done;
+			}
+			item->datalen = (u16)-1;
+		} else {
+			if (!(item->data = mm_malloc(datalen))) {
+				mm_free(item->name);
+				mm_free(item);
+				goto done;
+			}
+			item->datalen = datalen;
+			memcpy(item->data, data, datalen);
+		}
+	}
+	*itemp = item;
+	++(*countp);
+	result = 0;
+done:
+	EVDNS_UNLOCK(req->port);
+	return result;
+}
+/* exported function */
+int
+evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
+{
+	return evdns_server_request_add_reply(
+		  req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET,
+		  ttl, n*4, 0, addrs);
+}
+/* exported function */
+int
+evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
+{
+	return evdns_server_request_add_reply(
+		  req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET,
+		  ttl, n*16, 0, addrs);
+}
+/* exported function */
+int
+evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl)
+{
+	u32 a;
+	char buf[32];
+	if (in && inaddr_name)
+		return -1;
+	else if (!in && !inaddr_name)
+		return -1;
+	if (in) {
+		a = ntohl(in->s_addr);
+		evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
+				(int)(u8)((a	)&0xff),
+				(int)(u8)((a>>8 )&0xff),
+				(int)(u8)((a>>16)&0xff),
+				(int)(u8)((a>>24)&0xff));
+		inaddr_name = buf;
+	}
+	return evdns_server_request_add_reply(
+		  req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET,
+		  ttl, -1, 1, hostname);
+}
+/* exported function */
+int
+evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl)
+{
+	return evdns_server_request_add_reply(
+		  req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET,
+		  ttl, -1, 1, cname);
+}
+/* exported function */
+void
+evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags)
+{
+	struct server_request *req = TO_SERVER_REQUEST(exreq);
+	req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD);
+	req->base.flags |= flags;
+}
+static int
+evdns_server_request_format_response(struct server_request *req, int err)
+{
+	unsigned char buf[1500];
+	size_t buf_len = sizeof(buf);
+	off_t j = 0, r;
+	u16 _t;
+	u32 _t32;
+	int i;
+	u16 flags;
+	struct dnslabel_table table;
+	if (err < 0 || err > 15) return -1;
+	/* Set response bit and error code; copy OPCODE and RD fields from
+	 * question; copy RA and AA if set by caller. */
+	flags = req->base.flags;
+	flags |= (0x8000 | err);
+	dnslabel_table_init(&table);
+	APPEND16(req->trans_id);
+	APPEND16(flags);
+	APPEND16(req->base.nquestions);
+	APPEND16(req->n_answer);
+	APPEND16(req->n_authority);
+	APPEND16(req->n_additional);
+	/* Add questions. */
+	for (i=0; i < req->base.nquestions; ++i) {
+		const char *s = req->base.questions[i]->name;
+		j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table);
+		if (j < 0) {
+			dnslabel_clear(&table);
+			return (int) j;
+		}
+		APPEND16(req->base.questions[i]->type);
+		APPEND16(req->base.questions[i]->dns_question_class);
+	}
+	/* Add answer, authority, and additional sections. */
+	for (i=0; i<3; ++i) {
+		struct server_reply_item *item;
+		if (i==0)
+			item = req->answer;
+		else if (i==1)
+			item = req->authority;
+		else
+			item = req->additional;
+		while (item) {
+			r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
+			if (r < 0)
+				goto overflow;
+			j = r;
+			APPEND16(item->type);
+			APPEND16(item->dns_question_class);
+			APPEND32(item->ttl);
+			if (item->is_name) {
+				off_t len_idx = j, name_start;
+				j += 2;
+				name_start = j;
+				r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
+				if (r < 0)
+					goto overflow;
+				j = r;
+				_t = htons( (short) (j-name_start) );
+				memcpy(buf+len_idx, &_t, 2);
+			} else {
+				APPEND16(item->datalen);
+				if (j+item->datalen > (off_t)buf_len)
+					goto overflow;
+				memcpy(buf+j, item->data, item->datalen);
+				j += item->datalen;
+			}
+			item = item->next;
+		}
+	}
+	if (j > 512) {
+overflow:
+		j = 512;
+		buf[2] |= 0x02; /* set the truncated bit. */
+	}
+	req->response_len = j;
+	if (!(req->response = mm_malloc(req->response_len))) {
+		server_request_free_answers(req);
+		dnslabel_clear(&table);
+		return (-1);
+	}
+	memcpy(req->response, buf, req->response_len);
+	server_request_free_answers(req);
+	dnslabel_clear(&table);
+	return (0);
+}
+/* exported function */
+int
+evdns_server_request_respond(struct evdns_server_request *_req, int err)
+{
+	struct server_request *req = TO_SERVER_REQUEST(_req);
+	struct evdns_server_port *port = req->port;
+	int r = -1;
+	EVDNS_LOCK(port);
+	if (!req->response) {
+		if ((r = evdns_server_request_format_response(req, err))<0)
+			goto done;
+	}
+	r = sendto(port->socket, req->response, (int)req->response_len, 0,
+			   (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen);
+	if (r<0) {
+		int sock_err = evutil_socket_geterror(port->socket);
+		if (EVUTIL_ERR_RW_RETRIABLE(sock_err))
+			goto done;
+		if (port->pending_replies) {
+			req->prev_pending = port->pending_replies->prev_pending;
+			req->next_pending = port->pending_replies;
+			req->prev_pending->next_pending =
+				req->next_pending->prev_pending = req;
+		} else {
+			req->prev_pending = req->next_pending = req;
+			port->pending_replies = req;
+			port->choked = 1;
+			(void) event_del(&port->event);
+			event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port);
+			if (event_add(&port->event, NULL) < 0) {
+				log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server");
+			}
+		}
+		r = 1;
+		goto done;
+	}
+	if (server_request_free(req)) {
+		r = 0;
+		goto done;
+	}
+	if (port->pending_replies)
+		server_port_flush(port);
+	r = 0;
+done:
+	EVDNS_UNLOCK(port);
+	return r;
+}
+/* Free all storage held by RRs in req. */
+static void
+server_request_free_answers(struct server_request *req)
+{
+	struct server_reply_item *victim, *next, **list;
+	int i;
+	for (i = 0; i < 3; ++i) {
+		if (i==0)
+			list = &req->answer;
+		else if (i==1)
+			list = &req->authority;
+		else
+			list = &req->additional;
+		victim = *list;
+		while (victim) {
+			next = victim->next;
+			mm_free(victim->name);
+			if (victim->data)
+				mm_free(victim->data);
+			mm_free(victim);
+			victim = next;
+		}
+		*list = NULL;
+	}
+}
+/* Free all storage held by req, and remove links to it. */
+/* return true iff we just wound up freeing the server_port. */
+static int
+server_request_free(struct server_request *req)
+{
+	int i, rc=1, lock=0;
+	if (req->base.questions) {
+		for (i = 0; i < req->base.nquestions; ++i)
+			mm_free(req->base.questions[i]);
+		mm_free(req->base.questions);
+	}
+	if (req->port) {
+		EVDNS_LOCK(req->port);
+		lock=1;
+		if (req->port->pending_replies == req) {
+			if (req->next_pending && req->next_pending != req)
+				req->port->pending_replies = req->next_pending;
+			else
+				req->port->pending_replies = NULL;
+		}
+		rc = --req->port->refcnt;
+	}
+	if (req->response) {
+		mm_free(req->response);
+	}
+	server_request_free_answers(req);
+	if (req->next_pending && req->next_pending != req) {
+		req->next_pending->prev_pending = req->prev_pending;
+		req->prev_pending->next_pending = req->next_pending;
+	}
+	if (rc == 0) {
+		EVDNS_UNLOCK(req->port); /* ????? nickm */
+		server_port_free(req->port);
+		mm_free(req);
+		return (1);
+	}
+	if (lock)
+		EVDNS_UNLOCK(req->port);
+	mm_free(req);
+	return (0);
+}
+/* Free all storage held by an evdns_server_port.  Only called when  */
+static void
+server_port_free(struct evdns_server_port *port)
+{
+	EVUTIL_ASSERT(port);
+	EVUTIL_ASSERT(!port->refcnt);
+	EVUTIL_ASSERT(!port->pending_replies);
+	if (port->socket > 0) {
+		evutil_closesocket(port->socket);
+		port->socket = -1;
+	}
+	(void) event_del(&port->event);
+	event_debug_unassign(&port->event);
+	EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	mm_free(port);
+}
+/* exported function */
+int
+evdns_server_request_drop(struct evdns_server_request *_req)
+{
+	struct server_request *req = TO_SERVER_REQUEST(_req);
+	server_request_free(req);
+	return 0;
+}
+/* exported function */
+int
+evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len)
+{
+	struct server_request *req = TO_SERVER_REQUEST(_req);
+	if (addr_len < (int)req->addrlen)
+		return -1;
+	memcpy(sa, &(req->addr), req->addrlen);
+	return req->addrlen;
+}
+#undef APPEND16
+#undef APPEND32
+/* this is a libevent callback function which is called when a request */
+/* has timed out. */
+static void
+evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) {
+	struct request *const req = (struct request *) arg;
+	struct evdns_base *base = req->base;
+	(void) fd;
+	(void) events;
+	log(EVDNS_LOG_DEBUG, "Request %p timed out", arg);
+	EVDNS_LOCK(base);
+	req->ns->timedout++;
+	if (req->ns->timedout > req->base->global_max_nameserver_timeout) {
+		req->ns->timedout = 0;
+		nameserver_failed(req->ns, "request timed out.");
+	}
+	if (req->tx_count >= req->base->global_max_retransmits) {
+		/* this request has failed */
+		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);
+	} else {
+		/* retransmit it */
+		struct nameserver *new_ns;
+		log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d",
+		    arg, req->tx_count);
+		(void) evtimer_del(&req->timeout_event);
+		new_ns = nameserver_pick(base);
+		if (new_ns)
+			req->ns = new_ns;
+		evdns_request_transmit(req);
+	}
+	EVDNS_UNLOCK(base);
+}
+/* try to send a request to a given server. */
+/* */
+/* return: */
+/*   0 ok */
+/*   1 temporary failure */
+/*   2 other failure */
+static int
+evdns_request_transmit_to(struct request *req, struct nameserver *server) {
+	int r;
+	ASSERT_LOCKED(req->base);
+	ASSERT_VALID_REQUEST(req);
+	r = sendto(server->socket, (void*)req->request, req->request_len, 0,
+	    (struct sockaddr *)&server->address, server->addrlen);
+	if (r < 0) {
+		int err = evutil_socket_geterror(server->socket);
+		if (EVUTIL_ERR_RW_RETRIABLE(err))
+			return 1;
+		nameserver_failed(req->ns, evutil_socket_error_to_string(err));
+		return 2;
+	} else if (r != (int)req->request_len) {
+		return 1;  /* short write */
+	} else {
+		return 0;
+	}
+}
+/* try to send a request, updating the fields of the request */
+/* as needed */
+/* */
+/* return: */
+/*   0 ok */
+/*   1 failed */
+static int
+evdns_request_transmit(struct request *req) {
+	int retcode = 0, r;
+	ASSERT_LOCKED(req->base);
+	ASSERT_VALID_REQUEST(req);
+	/* if we fail to send this packet then this flag marks it */
+	/* for evdns_transmit */
+	req->transmit_me = 1;
+	EVUTIL_ASSERT(req->trans_id != 0xffff);
+	if (req->ns->choked) {
+		/* don't bother trying to write to a socket */
+		/* which we have had EAGAIN from */
+		return 1;
+	}
+	r = evdns_request_transmit_to(req, req->ns);
+	switch (r) {
+	case 1:
+		/* temp failure */
+		req->ns->choked = 1;
+		nameserver_write_waiting(req->ns, 1);
+		return 1;
+	case 2:
+		/* failed to transmit the request entirely. */
+		retcode = 1;
+		/* fall through: we'll set a timeout, which will time out,
+		 * and make us retransmit the request anyway. */
+	default:
+		/* all ok */
+		log(EVDNS_LOG_DEBUG,
+		    "Setting timeout for request %p, 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 = socket(address->sa_family, SOCK_DGRAM, 0);
+	if (ns->socket < 0) { err = 1; goto out1; }
+	evutil_make_socket_closeonexec(ns->socket);
+	evutil_make_socket_nonblocking(ns->socket);
+	if (base->global_outgoing_addrlen &&
+	    !evutil_sockaddr_is_loopback(address)) {
+		if (bind(ns->socket,
+			(struct sockaddr*)&base->global_outgoing_address,
+			base->global_outgoing_addrlen) < 0) {
+			log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address");
+			err = 2;
+			goto out2;
+		}
+	}
+	memcpy(&ns->address, address, addrlen);
+	ns->addrlen = addrlen;
+	ns->state = 1;
+	event_assign(&ns->event, ns->base->event_base, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns);
+	if (event_add(&ns->event, NULL) < 0) {
+		err = 2;
+		goto out2;
+	}
+	log(EVDNS_LOG_DEBUG, "Added nameserver %s 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;
+}
+/* remove from the queue */
+static void
+evdns_request_remove(struct request *req, struct request **head)
+{
+	ASSERT_LOCKED(req->base);
+	ASSERT_VALID_REQUEST(req);
+#if 0
+	{
+		struct request *ptr;
+		int found = 0;
+		EVUTIL_ASSERT(*head != NULL);
+		ptr = *head;
+		do {
+			if (ptr == req) {
+				found = 1;
+				break;
+			}
+			ptr = ptr->next;
+		} while (ptr != *head);
+		EVUTIL_ASSERT(found);
+		EVUTIL_ASSERT(req->next);
+	}
+#endif
+	if (req->next == req) {
+		/* only item in the list */
+		*head = NULL;
+	} else {
+		req->next->prev = req->prev;
+		req->prev->next = req->next;
+		if (*head == req) *head = req->next;
+	}
+	req->next = req->prev = NULL;
+}
+/* insert into the tail of the queue */
+static void
+evdns_request_insert(struct request *req, struct request **head) {
+	ASSERT_LOCKED(req->base);
+	ASSERT_VALID_REQUEST(req);
+	if (!*head) {
+		*head = req;
+		req->next = req->prev = req;
+		return;
+	}
+	req->prev = (*head)->prev;
+	req->prev->next = req;
+	req->next = *head;
+	(*head)->prev = req;
+}
+static int
+string_num_dots(const char *s) {
+	int count = 0;
+	while ((s = strchr(s, '.'))) {
+		s++;
+		count++;
+	}
+	return count;
+}
+static struct request *
+request_new(struct evdns_base *base, struct evdns_request *handle, int type,
+	    const char *name, int flags, evdns_callback_type callback,
+	    void *user_ptr) {
+	const char issuing_now =
+	    (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0;
+	const size_t name_len = strlen(name);
+	const size_t request_max_len = evdns_request_len(name_len);
+	const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff;
+	/* the request data is alloced in a single block with the header */
+	struct request *const req =
+	    mm_malloc(sizeof(struct request) + request_max_len);
+	int rlen;
+	char namebuf[256];
+	(void) flags;
+	ASSERT_LOCKED(base);
+	if (!req) return NULL;
+	if (name_len >= sizeof(namebuf)) {
+		mm_free(req);
+		return NULL;
+	}
+	memset(req, 0, sizeof(struct request));
+	req->base = base;
+	evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req);
+	if (base->global_randomize_case) {
+		unsigned i;
+		char randbits[(sizeof(namebuf)+7)/8];
+		strlcpy(namebuf, name, sizeof(namebuf));
+		evutil_secure_rng_get_bytes(randbits, (name_len+7)/8);
+		for (i = 0; i < name_len; ++i) {
+			if (EVUTIL_ISALPHA(namebuf[i])) {
+				if ((randbits[i >> 3] & (1<<(i & 7))))
+					namebuf[i] |= 0x20;
+				else
+					namebuf[i] &= ~0x20;
+			}
+		}
+		name = namebuf;
+	}
+	/* request data lives just after the header */
+	req->request = ((u8 *) req) + sizeof(struct request);
+	/* denotes that the request data shouldn't be free()ed */
+	req->request_appended = 1;
+	rlen = evdns_request_data_build(name, name_len, trans_id,
+	    type, CLASS_INET, req->request, request_max_len);
+	if (rlen < 0)
+		goto err1;
+	req->request_len = rlen;
+	req->trans_id = trans_id;
+	req->tx_count = 0;
+	req->request_type = type;
+	req->user_pointer = user_ptr;
+	req->user_callback = callback;
+	req->ns = issuing_now ? nameserver_pick(base) : NULL;
+	req->next = req->prev = NULL;
+	req->handle = handle;
+	if (handle) {
+		handle->current_req = req;
+		handle->base = base;
+	}
+	return req;
+err1:
+	mm_free(req);
+	return NULL;
+}
+static void
+request_submit(struct request *const req) {
+	struct evdns_base *base = req->base;
+	ASSERT_LOCKED(base);
+	ASSERT_VALID_REQUEST(req);
+	if (req->ns) {
+		/* if it has a nameserver assigned then this is going */
+		/* straight into the inflight queue */
+		evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
+		base->global_requests_inflight++;
+		evdns_request_transmit(req);
+	} else {
+		evdns_request_insert(req, &base->req_waiting_head);
+		base->global_requests_waiting++;
+	}
+}
+/* exported function */
+void
+evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle)
+{
+	struct request *req;
+	if (!handle->current_req)
+		return;
+	if (!base) {
+		/* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */
+		base = handle->base;
+		if (!base)
+			base = handle->current_req->base;
+	}
+	EVDNS_LOCK(base);
+	if (handle->pending_cb) {
+		EVDNS_UNLOCK(base);
+		return;
+	}
+	req = handle->current_req;
+	ASSERT_VALID_REQUEST(req);
+	reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL);
+	if (req->ns) {
+		/* remove from inflight queue */
+		request_finished(req, &REQ_HEAD(base, req->trans_id), 1);
+	} else {
+		/* remove from global_waiting head */
+		request_finished(req, &base->req_waiting_head, 1);
+	}
+	EVDNS_UNLOCK(base);
+}
+/* exported function */
+struct evdns_request *
+evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags,
+evdns_callback_type callback, void *ptr) {
+	struct evdns_request *handle;
+	struct request *req;
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
+	handle = mm_calloc(1, sizeof(*handle));
+	if (handle == NULL)
+		return NULL;
+	EVDNS_LOCK(base);
+	if (flags & DNS_QUERY_NO_SEARCH) {
+		req =
+			request_new(base, handle, TYPE_A, name, flags,
+				    callback, ptr);
+		if (req)
+			request_submit(req);
+	} else {
+		search_request_new(base, handle, TYPE_A, name, flags,
+		    callback, ptr);
+	}
+	if (handle->current_req == NULL) {
+		mm_free(handle);
+		handle = NULL;
+	}
+	EVDNS_UNLOCK(base);
+	return handle;
+}
+int evdns_resolve_ipv4(const char *name, int flags,
+					   evdns_callback_type callback, void *ptr)
+{
+	return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr)
+		? 0 : -1;
+}
+/* exported function */
+struct evdns_request *
+evdns_base_resolve_ipv6(struct evdns_base *base,
+const char *name, int flags,
+evdns_callback_type callback, void *ptr)
+{
+	struct evdns_request *handle;
+	struct request *req;
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
+	handle = mm_calloc(1, sizeof(*handle));
+	if (handle == NULL)
+		return NULL;
+	EVDNS_LOCK(base);
+	if (flags & DNS_QUERY_NO_SEARCH) {
+		req = request_new(base, handle, TYPE_AAAA, name, flags,
+				  callback, ptr);
+		if (req)
+			request_submit(req);
+	} else {
+		search_request_new(base, handle, TYPE_AAAA, name, flags,
+		    callback, ptr);
+	}
+	if (handle->current_req == NULL) {
+		mm_free(handle);
+		handle = NULL;
+	}
+	EVDNS_UNLOCK(base);
+	return handle;
+}
+int evdns_resolve_ipv6(const char *name, int flags,
+evdns_callback_type callback, void *ptr) {
+	return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr)
+		? 0 : -1;
+}
+struct evdns_request *
+evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
+	char buf[32];
+	struct evdns_request *handle;
+	struct request *req;
+	u32 a;
+	EVUTIL_ASSERT(in);
+	a = ntohl(in->s_addr);
+	evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
+			(int)(u8)((a	)&0xff),
+			(int)(u8)((a>>8 )&0xff),
+			(int)(u8)((a>>16)&0xff),
+			(int)(u8)((a>>24)&0xff));
+	handle = mm_calloc(1, sizeof(*handle));
+	if (handle == NULL)
+		return NULL;
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
+	EVDNS_LOCK(base);
+	req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr);
+	if (req)
+		request_submit(req);
+	if (handle->current_req == NULL) {
+		mm_free(handle);
+		handle = NULL;
+	}
+	EVDNS_UNLOCK(base);
+	return (handle);
+}
+int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
+	return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr)
+		? 0 : -1;
+}
+struct evdns_request *
+evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
+	/* 32 nybbles, 32 periods, "ip6.arpa", NUL. */
+	char buf[73];
+	char *cp;
+	struct evdns_request *handle;
+	struct request *req;
+	int i;
+	EVUTIL_ASSERT(in);
+	cp = buf;
+	for (i=15; i >= 0; --i) {
+		u8 byte = in->s6_addr[i];
+		*cp++ = "0123456789abcdef"[byte & 0x0f];
+		*cp++ = '.';
+		*cp++ = "0123456789abcdef"[byte >> 4];
+		*cp++ = '.';
+	}
+	EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf));
+	memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1);
+	handle = mm_calloc(1, sizeof(*handle));
+	if (handle == NULL)
+		return NULL;
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
+	EVDNS_LOCK(base);
+	req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr);
+	if (req)
+		request_submit(req);
+	if (handle->current_req == NULL) {
+		mm_free(handle);
+		handle = NULL;
+	}
+	EVDNS_UNLOCK(base);
+	return (handle);
+}
+int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
+	return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr)
+		? 0 : -1;
+}
+/* ================================================================= */
+/* Search support */
+/* */
+/* the libc resolver has support for searching a number of domains */
+/* to find a name. If nothing else then it takes the single domain */
+/* from the gethostname() call. */
+/* */
+/* It can also be configured via the domain and search options in a */
+/* resolv.conf. */
+/* */
+/* The ndots option controls how many dots it takes for the resolver */
+/* to decide that a name is non-local and so try a raw lookup first. */
+struct search_domain {
+	int len;
+	struct search_domain *next;
+	/* the text string is appended to this structure */
+};
+struct search_state {
+	int refcount;
+	int ndots;
+	int num_domains;
+	struct search_domain *head;
+};
+static void
+search_state_decref(struct search_state *const state) {
+	if (!state) return;
+	state->refcount--;
+	if (!state->refcount) {
+		struct search_domain *next, *dom;
+		for (dom = state->head; dom; dom = next) {
+			next = dom->next;
+			mm_free(dom);
+		}
+		mm_free(state);
+	}
+}
+static struct search_state *
+search_state_new(void) {
+	struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state));
+	if (!state) return NULL;
+	memset(state, 0, sizeof(struct search_state));
+	state->refcount = 1;
+	state->ndots = 1;
+	return state;
+}
+static void
+search_postfix_clear(struct evdns_base *base) {
+	search_state_decref(base->global_search_state);
+	base->global_search_state = search_state_new();
+}
+/* exported function */
+void
+evdns_base_search_clear(struct evdns_base *base)
+{
+	EVDNS_LOCK(base);
+	search_postfix_clear(base);
+	EVDNS_UNLOCK(base);
+}
+void
+evdns_search_clear(void) {
+	evdns_base_search_clear(current_base);
+}
+static void
+search_postfix_add(struct evdns_base *base, const char *domain) {
+	size_t domain_len;
+	struct search_domain *sdomain;
+	while (domain[0] == '.') domain++;
+	domain_len = strlen(domain);
+	ASSERT_LOCKED(base);
+	if (!base->global_search_state) base->global_search_state = search_state_new();
+	if (!base->global_search_state) return;
+	base->global_search_state->num_domains++;
+	sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len);
+	if (!sdomain) return;
+	memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len);
+	sdomain->next = base->global_search_state->head;
+	sdomain->len = (int) domain_len;
+	base->global_search_state->head = sdomain;
+}
+/* reverse the order of members in the postfix list. This is needed because, */
+/* when parsing resolv.conf we push elements in the wrong order */
+static void
+search_reverse(struct evdns_base *base) {
+	struct search_domain *cur, *prev = NULL, *next;
+	ASSERT_LOCKED(base);
+	cur = base->global_search_state->head;
+	while (cur) {
+		next = cur->next;
+		cur->next = prev;
+		prev = cur;
+		cur = next;
+	}
+	base->global_search_state->head = prev;
+}
+/* exported function */
+void
+evdns_base_search_add(struct evdns_base *base, const char *domain) {
+	EVDNS_LOCK(base);
+	search_postfix_add(base, domain);
+	EVDNS_UNLOCK(base);
+}
+void
+evdns_search_add(const char *domain) {
+	evdns_base_search_add(current_base, domain);
+}
+/* exported function */
+void
+evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) {
+	EVDNS_LOCK(base);
+	if (!base->global_search_state) base->global_search_state = search_state_new();
+	if (base->global_search_state)
+		base->global_search_state->ndots = ndots;
+	EVDNS_UNLOCK(base);
+}
+void
+evdns_search_ndots_set(const int ndots) {
+	evdns_base_search_ndots_set(current_base, ndots);
+}
+static void
+search_set_from_hostname(struct evdns_base *base) {
+	char hostname[HOST_NAME_MAX + 1], *domainname;
+	ASSERT_LOCKED(base);
+	search_postfix_clear(base);
+	if (gethostname(hostname, sizeof(hostname))) return;
+	domainname = strchr(hostname, '.');
+	if (!domainname) return;
+	search_postfix_add(base, domainname);
+}
+/* warning: returns malloced string */
+static char *
+search_make_new(const struct search_state *const state, int n, const char *const base_name) {
+	const size_t base_len = strlen(base_name);
+	const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1;
+	struct search_domain *dom;
+	for (dom = state->head; dom; dom = dom->next) {
+		if (!n--) {
+			/* this is the postfix we want */
+			/* the actual postfix string is kept at the end of the structure */
+			const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain);
+			const int postfix_len = dom->len;
+			char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1);
+			if (!newname) return NULL;
+			memcpy(newname, base_name, base_len);
+			if (need_to_append_dot) newname[base_len] = '.';
+			memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len);
+			newname[base_len + need_to_append_dot + postfix_len] = 0;
+			return newname;
+		}
+	}
+	/* we ran off the end of the list and still didn't find the requested string */
+	EVUTIL_ASSERT(0);
+	return NULL; /* unreachable; stops warnings in some compilers. */
+}
+static struct request *
+search_request_new(struct evdns_base *base, struct evdns_request *handle,
+		   int type, const char *const name, int flags,
+		   evdns_callback_type user_callback, void *user_arg) {
+	ASSERT_LOCKED(base);
+	EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA);
+	EVUTIL_ASSERT(handle->current_req == NULL);
+	if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) &&
+	     base->global_search_state &&
+		 base->global_search_state->num_domains) {
+		/* we have some domains to search */
+		struct request *req;
+		if (string_num_dots(name) >= base->global_search_state->ndots) {
+			req = request_new(base, handle, type, name, flags, user_callback, user_arg);
+			if (!req) return NULL;
+			handle->search_index = -1;
+		} else {
+			char *const new_name = search_make_new(base->global_search_state, 0, name);
+			if (!new_name) return NULL;
+			req = request_new(base, handle, type, new_name, flags, user_callback, user_arg);
+			mm_free(new_name);
+			if (!req) return NULL;
+			handle->search_index = 0;
+		}
+		EVUTIL_ASSERT(handle->search_origname == NULL);
+		handle->search_origname = mm_strdup(name);
+		if (handle->search_origname == NULL) {
+			/* XXX Should we dealloc req? If yes, how? */
+			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) {
+	/* if the file isn't found then we assume a local resolver */
+	ASSERT_LOCKED(base);
+	if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(base);
+	if (flags & DNS_OPTION_NAMESERVERS) evdns_base_nameserver_ip_add(base,"127.0.0.1");
+}
+#ifndef _EVENT_HAVE_STRTOK_R
+static char *
+strtok_r(char *s, const char *delim, char **state) {
+	char *cp, *start;
+	start = cp = s ? s : *state;
+	if (!cp)
+		return NULL;
+	while (*cp && !strchr(delim, *cp))
+		++cp;
+	if (!*cp) {
+		if (cp == start)
+			return NULL;
+		*state = NULL;
+		return start;
+	} else {
+		*cp++ = '\0';
+		*state = cp;
+		return start;
+	}
+}
+#endif
+/* helper version of atoi which returns -1 on error */
+static int
+strtoint(const char *const str)
+{
+	char *endptr;
+	const int r = strtol(str, &endptr, 10);
+	if (*endptr) return -1;
+	return r;
+}
+/* Parse a number of seconds into a timeval; return -1 on error. */
+static int
+strtotimeval(const char *const str, struct timeval *out)
+{
+	double d;
+	char *endptr;
+	d = strtod(str, &endptr);
+	if (*endptr) return -1;
+	if (d < 0) return -1;
+	out->tv_sec = (int) d;
+	out->tv_usec = (int) ((d - (int) d)*1000000);
+	if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */
+		return -1;
+	return 0;
+}
+/* helper version of atoi that returns -1 on error and clips to bounds. */
+static int
+strtoint_clipped(const char *const str, int min, int max)
+{
+	int r = strtoint(str);
+	if (r == -1)
+		return r;
+	else if (r<min)
+		return min;
+	else if (r>max)
+		return max;
+	else
+		return r;
+}
+static int
+evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight)
+{
+	int old_n_heads = base->n_req_heads, n_heads;
+	struct request **old_heads = base->req_heads, **new_heads, *req;
+	int i;
+	ASSERT_LOCKED(base);
+	if (maxinflight < 1)
+		maxinflight = 1;
+	n_heads = (maxinflight+4) / 5;
+	EVUTIL_ASSERT(n_heads > 0);
+	new_heads = mm_calloc(n_heads, sizeof(struct request*));
+	if (!new_heads)
+		return (-1);
+	if (old_heads) {
+		for (i = 0; i < old_n_heads; ++i) {
+			while (old_heads[i]) {
+				req = old_heads[i];
+				evdns_request_remove(req, &old_heads[i]);
+				evdns_request_insert(req, &new_heads[req->trans_id % n_heads]);
+			}
+		}
+		mm_free(old_heads);
+	}
+	base->req_heads = new_heads;
+	base->n_req_heads = n_heads;
+	base->global_max_requests_inflight = maxinflight;
+	return (0);
+}
+/* exported function */
+int
+evdns_base_set_option(struct evdns_base *base,
+const char *option, const char *val)
+{
+	int res;
+	EVDNS_LOCK(base);
+	res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL);
+	EVDNS_UNLOCK(base);
+	return res;
+}
+static inline int
+str_matches_option(const char *s1, const char *optionname)
+{
+	/* Option names are given as "option:" We accept either 'option' in
+	 * s1, or 'option:randomjunk'.  The latter form is to implement the
+	 * resolv.conf parser. */
+	size_t optlen = strlen(optionname);
+	size_t slen = strlen(s1);
+	if (slen == optlen || slen == optlen - 1)
+		return !strncmp(s1, optionname, slen);
+	else if (slen > optlen)
+		return !strncmp(s1, optionname, optlen);
+	else
+		return 0;
+}
+static int
+evdns_base_set_option_impl(struct evdns_base *base,
+const char *option, const char *val, int flags)
+{
+	ASSERT_LOCKED(base);
+	if (str_matches_option(option, "ndots:")) {
+		const int ndots = strtoint(val);
+		if (ndots == -1) return -1;
+		if (!(flags & DNS_OPTION_SEARCH)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots);
+		if (!base->global_search_state) base->global_search_state = search_state_new();
+		if (!base->global_search_state) return -1;
+		base->global_search_state->ndots = ndots;
+	} else if (str_matches_option(option, "timeout:")) {
+		struct timeval tv;
+		if (strtotimeval(val, &tv) == -1) return -1;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val);
+		memcpy(&base->global_timeout, &tv, sizeof(struct timeval));
+	} else if (str_matches_option(option, "getaddrinfo-allow-skew:")) {
+		struct timeval tv;
+		if (strtotimeval(val, &tv) == -1) return -1;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s",
+		    val);
+		memcpy(&base->global_getaddrinfo_allow_skew, &tv,
+		    sizeof(struct timeval));
+	} else if (str_matches_option(option, "max-timeouts:")) {
+		const int maxtimeout = strtoint_clipped(val, 1, 255);
+		if (maxtimeout == -1) return -1;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d",
+			maxtimeout);
+		base->global_max_nameserver_timeout = maxtimeout;
+	} else if (str_matches_option(option, "max-inflight:")) {
+		const int maxinflight = strtoint_clipped(val, 1, 65000);
+		if (maxinflight == -1) return -1;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d",
+			maxinflight);
+		evdns_base_set_max_requests_inflight(base, maxinflight);
+	} else if (str_matches_option(option, "attempts:")) {
+		int retries = strtoint(val);
+		if (retries == -1) return -1;
+		if (retries > 255) retries = 255;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries);
+		base->global_max_retransmits = retries;
+	} else if (str_matches_option(option, "randomize-case:")) {
+		int randcase = strtoint(val);
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		base->global_randomize_case = randcase;
+	} else if (str_matches_option(option, "bind-to:")) {
+		/* XXX This only applies to successive nameservers, not
+		 * to already-configured ones.	We might want to fix that. */
+		int len = sizeof(base->global_outgoing_address);
+		if (!(flags & DNS_OPTION_NAMESERVERS)) return 0;
+		if (evutil_parse_sockaddr_port(val,
+			(struct sockaddr*)&base->global_outgoing_address, &len))
+			return -1;
+		base->global_outgoing_addrlen = len;
+	} else if (str_matches_option(option, "initial-probe-timeout:")) {
+		struct timeval tv;
+		if (strtotimeval(val, &tv) == -1) return -1;
+		if (tv.tv_sec > 3600)
+			tv.tv_sec = 3600;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s",
+		    val);
+		memcpy(&base->global_nameserver_probe_initial_timeout, &tv,
+		    sizeof(tv));
+	}
+	return 0;
+}
+int
+evdns_set_option(const char *option, const char *val, int flags)
+{
+	if (!current_base)
+		current_base = evdns_base_new(NULL, 0);
+	return evdns_base_set_option(current_base, option, val);
+}
+static void
+resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) {
+	char *strtok_state;
+	static const char *const delims = " \t";
+#define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
+	char *const first_token = strtok_r(start, delims, &strtok_state);
+	ASSERT_LOCKED(base);
+	if (!first_token) return;
+	if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) {
+		const char *const nameserver = NEXT_TOKEN;
+		if (nameserver)
+			evdns_base_nameserver_ip_add(base, nameserver);
+	} else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) {
+		const char *const domain = NEXT_TOKEN;
+		if (domain) {
+			search_postfix_clear(base);
+			search_postfix_add(base, domain);
+		}
+	} else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) {
+		const char *domain;
+		search_postfix_clear(base);
+		while ((domain = NEXT_TOKEN)) {
+			search_postfix_add(base, domain);
+		}
+		search_reverse(base);
+	} else if (!strcmp(first_token, "options")) {
+		const char *option;
+		while ((option = NEXT_TOKEN)) {
+			const char *val = strchr(option, ':');
+			evdns_base_set_option_impl(base, option, val ? val+1 : "", flags);
+		}
+	}
+#undef NEXT_TOKEN
+}
+/* exported function */
+/* returns: */
+/*   0 no errors */
+/*   1 failed to open file */
+/*   2 failed to stat file */
+/*   3 file too large */
+/*   4 out of memory */
+/*   5 short read from file */
+int
+evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) {
+	int res;
+	EVDNS_LOCK(base);
+	res = evdns_base_resolv_conf_parse_impl(base, flags, filename);
+	EVDNS_UNLOCK(base);
+	return res;
+}
+static char *
+evdns_get_default_hosts_filename(void)
+{
+#ifdef WIN32
+	/* Windows is a little coy about where it puts its configuration
+	 * files.  Sure, they're _usually_ in C:\windows\system32, but
+	 * there's no reason in principle they couldn't be in
+	 * W:\hoboken chicken emergency\
+	 */
+	char path[MAX_PATH+1];
+	static const char hostfile[] = "\\drivers\\etc\\hosts";
+	char *path_out;
+	size_t len_out;
+	if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0))
+		return NULL;
+	len_out = strlen(path)+strlen(hostfile);
+	path_out = mm_malloc(len_out+1);
+	evutil_snprintf(path_out, len_out, "%s%s", path, hostfile);
+	return path_out;
+#else
+	return mm_strdup("/etc/hosts");
+#endif
+}
+static int
+evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) {
+	size_t n;
+	char *resolv;
+	char *start;
+	int err = 0;
+	log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
+	if (flags & DNS_OPTION_HOSTSFILE) {
+		char *fname = evdns_get_default_hosts_filename();
+		evdns_base_load_hosts(base, fname);
+		if (fname)
+			mm_free(fname);
+	}
+	if ((err = evutil_read_file(filename, &resolv, &n, 0)) < 0) {
+		if (err == -1) {
+			/* No file. */
+			evdns_resolv_set_defaults(base, flags);
+			return 1;
+		} else {
+			return 2;
+		}
+	}
+	start = resolv;
+	for (;;) {
+		char *const newline = strchr(start, '\n');
+		if (!newline) {
+			resolv_conf_parse_line(base, start, flags);
+			break;
+		} else {
+			*newline = 0;
+			resolv_conf_parse_line(base, start, flags);
+			start = newline + 1;
+		}
+	}
+	if (!base->server_head && (flags & DNS_OPTION_NAMESERVERS)) {
+		/* no nameservers were configured. */
+		evdns_base_nameserver_ip_add(base, "127.0.0.1");
+		err = 6;
+	}
+	if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) {
+		search_set_from_hostname(base);
+	}
+	mm_free(resolv);
+	return err;
+}
+int
+evdns_resolv_conf_parse(int flags, const char *const filename) {
+	if (!current_base)
+		current_base = evdns_base_new(NULL, 0);
+	return evdns_base_resolv_conf_parse(current_base, flags, filename);
+}
+#ifdef WIN32
+/* Add multiple nameservers from a space-or-comma-separated list. */
+static int
+evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) {
+	const char *addr;
+	char *buf;
+	int r;
+	ASSERT_LOCKED(base);
+	while (*ips) {
+		while (isspace(*ips) || *ips == ',' || *ips == '\t')
+			++ips;
+		addr = ips;
+		while (isdigit(*ips) || *ips == '.' || *ips == ':' ||
+		    *ips=='[' || *ips==']')
+			++ips;
+		buf = mm_malloc(ips-addr+1);
+		if (!buf) return 4;
+		memcpy(buf, addr, ips-addr);
+		buf[ips-addr] = '\0';
+		r = evdns_base_nameserver_ip_add(base, buf);
+		mm_free(buf);
+		if (r) return r;
+	}
+	return 0;
+}
+typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*);
+/* Use the windows GetNetworkParams interface in iphlpapi.dll to */
+/* figure out what our nameservers are. */
+static int
+load_nameservers_with_getnetworkparams(struct evdns_base *base)
+{
+	/* Based on MSDN examples and inspection of  c-ares code. */
+	FIXED_INFO *fixed;
+	HMODULE handle = 0;
+	ULONG size = sizeof(FIXED_INFO);
+	void *buf = NULL;
+	int status = 0, r, added_any;
+	IP_ADDR_STRING *ns;
+	GetNetworkParams_fn_t fn;
+	ASSERT_LOCKED(base);
+	if (!(handle = evutil_load_windows_system_library(
+			TEXT("iphlpapi.dll")))) {
+		log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll");
+		status = -1;
+		goto done;
+	}
+	if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) {
+		log(EVDNS_LOG_WARN, "Could not get address of function.");
+		status = -1;
+		goto done;
+	}
+	buf = mm_malloc(size);
+	if (!buf) { status = 4; goto done; }
+	fixed = buf;
+	r = fn(fixed, &size);
+	if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) {
+		status = -1;
+		goto done;
+	}
+	if (r != ERROR_SUCCESS) {
+		mm_free(buf);
+		buf = mm_malloc(size);
+		if (!buf) { status = 4; goto done; }
+		fixed = buf;
+		r = fn(fixed, &size);
+		if (r != ERROR_SUCCESS) {
+			log(EVDNS_LOG_DEBUG, "fn() failed.");
+			status = -1;
+			goto done;
+		}
+	}
+	EVUTIL_ASSERT(fixed);
+	added_any = 0;
+	ns = &(fixed->DnsServerList);
+	while (ns) {
+		r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String);
+		if (r) {
+			log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d",
+				(ns->IpAddress.String),(int)GetLastError());
+			status = r;
+		} else {
+			++added_any;
+			log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String);
+		}
+		ns = ns->Next;
+	}
+	if (!added_any) {
+		log(EVDNS_LOG_DEBUG, "No nameservers added.");
+		if (status == 0)
+			status = -1;
+	} else {
+		status = 0;
+	}
+done:
+	if (buf)
+		mm_free(buf);
+	if (handle)
+		FreeLibrary(handle);
+	return status;
+}
+static int
+config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey)
+{
+	char *buf;
+	DWORD bufsz = 0, type = 0;
+	int status = 0;
+	ASSERT_LOCKED(base);
+	if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz)
+	    != ERROR_MORE_DATA)
+		return -1;
+	if (!(buf = mm_malloc(bufsz)))
+		return -1;
+	if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
+	    == ERROR_SUCCESS && bufsz > 1) {
+		status = evdns_nameserver_ip_add_line(base,buf);
+	}
+	mm_free(buf);
+	return status;
+}
+#define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\")
+#define WIN_NS_9X_KEY  SERVICES_KEY TEXT("VxD\\MSTCP")
+#define WIN_NS_NT_KEY  SERVICES_KEY TEXT("Tcpip\\Parameters")
+static int
+load_nameservers_from_registry(struct evdns_base *base)
+{
+	int found = 0;
+	int r;
+#define TRY(k, name) \
+	if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \
+		log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \
+		found = 1;						\
+	} else if (!found) {						\
+		log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \
+		    #k,#name);						\
+	}
+	ASSERT_LOCKED(base);
+	if (((int)GetVersion()) > 0) { /* NT */
+		HKEY nt_key = 0, interfaces_key = 0;
+		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0,
+				 KEY_READ, &nt_key) != ERROR_SUCCESS) {
+			log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError());
+			return -1;
+		}
+		r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0,
+			     KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS,
+			     &interfaces_key);
+		if (r != ERROR_SUCCESS) {
+			log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError());
+			return -1;
+		}
+		TRY(nt_key, "NameServer");
+		TRY(nt_key, "DhcpNameServer");
+		TRY(interfaces_key, "NameServer");
+		TRY(interfaces_key, "DhcpNameServer");
+		RegCloseKey(interfaces_key);
+		RegCloseKey(nt_key);
+	} else {
+		HKEY win_key = 0;
+		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0,
+				 KEY_READ, &win_key) != ERROR_SUCCESS) {
+			log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError());
+			return -1;
+		}
+		TRY(win_key, "NameServer");
+		RegCloseKey(win_key);
+	}
+	if (found == 0) {
+		log(EVDNS_LOG_WARN,"Didn't find any nameservers.");
+	}
+	return found ? 0 : -1;
+#undef TRY
+}
+int
+evdns_base_config_windows_nameservers(struct evdns_base *base)
+{
+	int r;
+	char *fname;
+	if (base == NULL)
+		base = current_base;
+	if (base == NULL)
+		return -1;
+	EVDNS_LOCK(base);
+	if (load_nameservers_with_getnetworkparams(base) == 0) {
+		EVDNS_UNLOCK(base);
+		return 0;
+	}
+	r = load_nameservers_from_registry(base);
+	fname = evdns_get_default_hosts_filename();
+	evdns_base_load_hosts(base, fname);
+	if (fname)
+		mm_free(fname);
+	EVDNS_UNLOCK(base);
+	return r;
+}
+int
+evdns_config_windows_nameservers(void)
+{
+	if (!current_base) {
+		current_base = evdns_base_new(NULL, 1);
+		return current_base == NULL ? -1 : 0;
+	} else {
+		return evdns_base_config_windows_nameservers(current_base);
+	}
+}
+#endif
+struct evdns_base *
+evdns_base_new(struct event_base *event_base, int initialize_nameservers)
+{
+	struct evdns_base *base;
+	if (evutil_secure_rng_init() < 0) {
+		log(EVDNS_LOG_WARN, "Unable to seed random number generator; "
+		    "DNS can't run.");
+		return NULL;
+	}
+	/* Give the evutil library a hook into its evdns-enabled
+	 * functionality.  We can't just call evdns_getaddrinfo directly or
+	 * else libevent-core will depend on libevent-extras. */
+	evutil_set_evdns_getaddrinfo_fn(evdns_getaddrinfo);
+	base = mm_malloc(sizeof(struct evdns_base));
+	if (base == NULL)
+		return (NULL);
+	memset(base, 0, sizeof(struct evdns_base));
+	base->req_waiting_head = NULL;
+	EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	EVDNS_LOCK(base);
+	/* Set max requests inflight and allocate req_heads. */
+	base->req_heads = NULL;
+	evdns_base_set_max_requests_inflight(base, 64);
+	base->server_head = NULL;
+	base->event_base = event_base;
+	base->global_good_nameservers = base->global_requests_inflight =
+		base->global_requests_waiting = 0;
+	base->global_timeout.tv_sec = 5;
+	base->global_timeout.tv_usec = 0;
+	base->global_max_reissues = 1;
+	base->global_max_retransmits = 3;
+	base->global_max_nameserver_timeout = 3;
+	base->global_search_state = NULL;
+	base->global_randomize_case = 1;
+	base->global_getaddrinfo_allow_skew.tv_sec = 3;
+	base->global_getaddrinfo_allow_skew.tv_usec = 0;
+	base->global_nameserver_probe_initial_timeout.tv_sec = 10;
+	base->global_nameserver_probe_initial_timeout.tv_usec = 0;
+	TAILQ_INIT(&base->hostsdb);
+	if (initialize_nameservers) {
+		int r;
+#ifdef WIN32
+		r = evdns_base_config_windows_nameservers(base);
+#else
+		r = evdns_base_resolv_conf_parse(base, DNS_OPTIONS_ALL, "/etc/resolv.conf");
+#endif
+		if (r == -1) {
+			evdns_base_free_and_unlock(base, 0);
+			return NULL;
+		}
+	}
+	EVDNS_UNLOCK(base);
+	return base;
+}
+int
+evdns_init(void)
+{
+	struct evdns_base *base = evdns_base_new(NULL, 1);
+	if (base) {
+		current_base = base;
+		return 0;
+	} else {
+		return -1;
+	}
+}
+const char *
+evdns_err_to_string(int err)
+{
+switch (err) {
+	case DNS_ERR_NONE: return "no error";
+	case DNS_ERR_FORMAT: return "misformatted query";
+	case DNS_ERR_SERVERFAILED: return "server failed";
+	case DNS_ERR_NOTEXIST: return "name does not exist";
+	case DNS_ERR_NOTIMPL: return "query not implemented";
+	case DNS_ERR_REFUSED: return "refused";
+	case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed";
+	case DNS_ERR_UNKNOWN: return "unknown";
+	case DNS_ERR_TIMEOUT: return "request timed out";
+	case DNS_ERR_SHUTDOWN: return "dns subsystem shut down";
+	case DNS_ERR_CANCEL: return "dns request canceled";
+	case DNS_ERR_NODATA: return "no records in the reply";
+	default: return "[Unknown error code]";
+}
+}
+static void
+evdns_nameserver_free(struct nameserver *server)
+{
+	if (server->socket >= 0)
+	evutil_closesocket(server->socket);
+	(void) event_del(&server->event);
+	event_debug_unassign(&server->event);
+	if (server->state == 0)
+		(void) event_del(&server->timeout_event);
+	event_debug_unassign(&server->timeout_event);
+	mm_free(server);
+}
+static void
+evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests)
+{
+	struct nameserver *server, *server_next;
+	struct search_domain *dom, *dom_next;
+	int i;
+	/* Requires that we hold the lock. */
+	/* TODO(nickm) we might need to refcount here. */
+	for (i = 0; i < base->n_req_heads; ++i) {
+		while (base->req_heads[i]) {
+			if (fail_requests)
+				reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL);
+			request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1);
+		}
+	}
+	while (base->req_waiting_head) {
+		if (fail_requests)
+			reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL);
+		request_finished(base->req_waiting_head, &base->req_waiting_head, 1);
+	}
+	base->global_requests_inflight = base->global_requests_waiting = 0;
+	for (server = base->server_head; server; server = server_next) {
+		server_next = server->next;
+		evdns_nameserver_free(server);
+		if (server_next == base->server_head)
+			break;
+	}
+	base->server_head = NULL;
+	base->global_good_nameservers = 0;
+	if (base->global_search_state) {
+		for (dom = base->global_search_state->head; dom; dom = dom_next) {
+			dom_next = dom->next;
+			mm_free(dom);
+		}
+		mm_free(base->global_search_state);
+		base->global_search_state = NULL;
+	}
+	{
+		struct hosts_entry *victim;
+		while ((victim = TAILQ_FIRST(&base->hostsdb))) {
+			TAILQ_REMOVE(&base->hostsdb, victim, next);
+			mm_free(victim);
+		}
+	}
+	mm_free(base->req_heads);
+	EVDNS_UNLOCK(base);
+	EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
+	mm_free(base);
+}
+void
+evdns_base_free(struct evdns_base *base, int fail_requests)
+{
+	EVDNS_LOCK(base);
+	evdns_base_free_and_unlock(base, fail_requests);
+}
+void
+evdns_shutdown(int fail_requests)
+{
+	if (current_base) {
+		struct evdns_base *b = current_base;
+		current_base = NULL;
+		evdns_base_free(b, fail_requests);
+	}
+	evdns_log_fn = NULL;
+}
+static int
+evdns_base_parse_hosts_line(struct evdns_base *base, char *line)
+{
+	char *strtok_state;
+	static const char *const delims = " \t";
+	char *const addr = strtok_r(line, delims, &strtok_state);
+	char *hostname, *hash;
+	struct sockaddr_storage ss;
+	int socklen = sizeof(ss);
+	ASSERT_LOCKED(base);
+#define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
+	if (!addr || *addr == '#')
+		return 0;
+	memset(&ss, 0, sizeof(ss));
+	if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0)
+		return -1;
+	if (socklen > (int)sizeof(struct sockaddr_in6))
+		return -1;
+	if (sockaddr_getport((struct sockaddr*)&ss))
+		return -1;
+	while ((hostname = NEXT_TOKEN)) {
+		struct hosts_entry *he;
+		size_t namelen;
+		if ((hash = strchr(hostname, '#'))) {
+			if (hash == hostname)
+				return 0;
+			*hash = '\0';
+		}
+		namelen = strlen(hostname);
+		he = mm_calloc(1, sizeof(struct hosts_entry)+namelen);
+		if (!he)
+			return -1;
+		EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr));
+		memcpy(&he->addr, &ss, socklen);
+		memcpy(he->hostname, hostname, namelen+1);
+		he->addrlen = socklen;
+		TAILQ_INSERT_TAIL(&base->hostsdb, he, next);
+		if (hash)
+			return 0;
+	}
+	return 0;
+#undef NEXT_TOKEN
+}
+static int
+evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname)
+{
+	char *str=NULL, *cp, *eol;
+	size_t len;
+	int err=0;
+	ASSERT_LOCKED(base);
+	if (hosts_fname == NULL ||
+	    (err = evutil_read_file(hosts_fname, &str, &len, 0)) < 0) {
+		char tmp[64];
+		strlcpy(tmp, "127.0.0.1   localhost", sizeof(tmp));
+		evdns_base_parse_hosts_line(base, tmp);
+		strlcpy(tmp, "::1   localhost", sizeof(tmp));
+		evdns_base_parse_hosts_line(base, tmp);
+		return err ? -1 : 0;
+	}
+	/* This will break early if there is a NUL in the hosts file.
+	 * Probably not a problem.*/
+	cp = str;
+	for (;;) {
+		eol = strchr(cp, '\n');
+		if (eol) {
+			*eol = '\0';
+			evdns_base_parse_hosts_line(base, cp);
+			cp = eol+1;
+		} else {
+			evdns_base_parse_hosts_line(base, cp);
+			break;
+		}
+	}
+	mm_free(str);
+	return 0;
+}
+int
+evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname)
+{
+	int res;
+	if (!base)
+		base = current_base;
+	EVDNS_LOCK(base);
+	res = evdns_base_load_hosts_impl(base, hosts_fname);
+	EVDNS_UNLOCK(base);
+	return res;
+}
+/* A single request for a getaddrinfo, either v4 or v6. */
+struct getaddrinfo_subrequest {
+	struct evdns_request *r;
+	ev_uint32_t type;
+};
+/* State data used to implement an in-progress getaddrinfo. */
+struct evdns_getaddrinfo_request {
+	struct evdns_base *evdns_base;
+	/* Copy of the modified 'hints' data that we'll use to build
+	 * answers. */
+	struct evutil_addrinfo hints;
+	/* The callback to invoke when we're done */
+	evdns_getaddrinfo_cb user_cb;
+	/* User-supplied data to give to the callback. */
+	void *user_data;
+	/* The port to use when building sockaddrs. */
+	ev_uint16_t port;
+	/* The sub_request for an A record (if any) */
+	struct getaddrinfo_subrequest ipv4_request;
+	/* The sub_request for an AAAA record (if any) */
+	struct getaddrinfo_subrequest ipv6_request;
+	/* The cname result that we were told (if any) */
+	char *cname_result;
+	/* If we have one request answered and one request still inflight,
+	 * then this field holds the answer from the first request... */
+	struct evutil_addrinfo *pending_result;
+	/* And this event is a timeout that will tell us to cancel the second
+	 * request if it's taking a long time. */
+	struct event timeout;
+	/* And this field holds the error code from the first request... */
+	int pending_error;
+	/* If this is set, the user canceled this request. */
+	unsigned user_canceled : 1;
+	/* If this is set, the user can no longer cancel this request; we're
+	 * just waiting for the free. */
+	unsigned request_done : 1;
+};
+/* Convert an evdns errors to the equivalent getaddrinfo error. */
+static int
+evdns_err_to_getaddrinfo_err(int e1)
+{
+	/* XXX Do this better! */
+	if (e1 == DNS_ERR_NONE)
+		return 0;
+	else if (e1 == DNS_ERR_NOTEXIST)
+		return EVUTIL_EAI_NONAME;
+	else
+		return EVUTIL_EAI_FAIL;
+}
+/* Return the more informative of two getaddrinfo errors. */
+static int
+getaddrinfo_merge_err(int e1, int e2)
+{
+	/* XXXX be cleverer here. */
+	if (e1 == 0)
+		return e2;
+	else
+		return e1;
+}
+static void
+free_getaddrinfo_request(struct evdns_getaddrinfo_request *data)
+{
+	/* DO NOT CALL this if either of the requests is pending.  Only once
+	 * both callbacks have been invoked is it safe to free the request */
+	if (data->pending_result)
+		evutil_freeaddrinfo(data->pending_result);
+	if (data->cname_result)
+		mm_free(data->cname_result);
+	event_del(&data->timeout);
+	mm_free(data);
+	return;
+}
+static void
+add_cname_to_reply(struct evdns_getaddrinfo_request *data,
+struct evutil_addrinfo *ai)
+{
+	if (data->cname_result && ai) {
+		ai->ai_canonname = data->cname_result;
+		data->cname_result = NULL;
+	}
+}
+/* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo
+* request has finished, but the other one took too long to answer. Pass
+* along the answer we got, and cancel the other request.
+*/
+static void
+evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr)
+{
+	int v4_timedout = 0, v6_timedout = 0;
+	struct evdns_getaddrinfo_request *data = ptr;
+	/* Cancel any pending requests, and note which one */
+	if (data->ipv4_request.r) {
+		/* 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;
+	}
+	EVDNS_LOCK(data->evdns_base);
+	if (evdns_result_is_answer(result)) {
+		if (req->type == DNS_IPv4_A)
+			++data->evdns_base->getaddrinfo_ipv4_answered;
+		else
+			++data->evdns_base->getaddrinfo_ipv6_answered;
+	}
+	user_canceled = data->user_canceled;
+	if (other_req->r == NULL)
+		data->request_done = 1;
+	EVDNS_UNLOCK(data->evdns_base);
+	req->r = NULL;
+	if (result == DNS_ERR_CANCEL && ! user_canceled) {
+		/* Internal cancel request from timeout or internal error.
+		 * we already answered the user. */
+		if (other_req->r == NULL)
+			free_getaddrinfo_request(data);
+		return;
+	}
+	if (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 */
+			evdns_getaddrinfo_set_timeout(data->evdns_base, data);
+			data->pending_error = err;
+			return;
+		}
+		if (user_canceled) {
+			data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data);
+		} else if (data->pending_result) {
+			/* If we have an answer waiting, and we weren't
+			 * canceled, ignore this error. */
+			add_cname_to_reply(data, data->pending_result);
+			data->user_cb(0, data->pending_result, data->user_data);
+			data->pending_result = NULL;
+		} else {
+			if (data->pending_error)
+				err = getaddrinfo_merge_err(err,
+				    data->pending_error);
+			data->user_cb(err, NULL, data->user_data);
+		}
+		free_getaddrinfo_request(data);
+		return;
+	} else if (user_canceled) {
+		if (other_req->r) {
+			/* The other request is still working; let it hit this
+			 * callback with EVUTIL_EAI_CANCEL callback and report
+			 * the failure. */
+			return;
+		}
+		data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data);
+		free_getaddrinfo_request(data);
+		return;
+	}
+	/* Looks like we got some answers. We should turn them into addrinfos
+	 * and then either queue those or return them all. */
+	EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA);
+	if (type == DNS_IPv4_A) {
+		memset(&sin, 0, sizeof(sin));
+		sin.sin_family = AF_INET;
+		sin.sin_port = htons(data->port);
+		sa = (struct sockaddr *)&sin;
+		socklen = sizeof(sin);
+		addrlen = 4;
+		addrp = &sin.sin_addr.s_addr;
+	} else {
+		memset(&sin6, 0, sizeof(sin6));
+		sin6.sin6_family = AF_INET6;
+		sin6.sin6_port = htons(data->port);
+		sa = (struct sockaddr *)&sin6;
+		socklen = sizeof(sin6);
+		addrlen = 16;
+		addrp = &sin6.sin6_addr.s6_addr;
+	}
+	res = NULL;
+	for (i=0; i < count; ++i) {
+		struct evutil_addrinfo *ai;
+		memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen);
+		ai = evutil_new_addrinfo(sa, socklen, &data->hints);
+		if (!ai) {
+			if (other_req->r) {
+				evdns_cancel_request(NULL, other_req->r);
+			}
+			data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data);
+			if (res)
+				evutil_freeaddrinfo(res);
+			if (other_req->r == NULL)
+				free_getaddrinfo_request(data);
+			return;
+		}
+		res = evutil_addrinfo_append(res, ai);
+	}
+	if (other_req->r) {
+		/* The other request is still in progress; wait for it */
+		/* XXXX handle failure from set_timeout */
+		evdns_getaddrinfo_set_timeout(data->evdns_base, data);
+		data->pending_result = res;
+		return;
+	} else {
+		/* The other request is done or never started; append its
+		 * results (if any) and return them. */
+		if (data->pending_result) {
+			if (req->type == DNS_IPv4_A)
+				res = evutil_addrinfo_append(res,
+				    data->pending_result);
+			else
+				res = evutil_addrinfo_append(
+				    data->pending_result, res);
+			data->pending_result = NULL;
+		}
+		/* Call the user callback. */
+		add_cname_to_reply(data, res);
+		data->user_cb(0, res, data->user_data);
+		/* Free data. */
+		free_getaddrinfo_request(data);
+	}
+}
+static struct hosts_entry *
+find_hosts_entry(struct evdns_base *base, const char *hostname,
+struct hosts_entry *find_after)
+{
+	struct hosts_entry *e;
+	if (find_after)
+		e = TAILQ_NEXT(find_after, next);
+	else
+		e = TAILQ_FIRST(&base->hostsdb);
+	for (; e; e = TAILQ_NEXT(e, next)) {
+		if (!evutil_ascii_strcasecmp(e->hostname, hostname))
+			return e;
+	}
+	return NULL;
+}
+static int
+evdns_getaddrinfo_fromhosts(struct evdns_base *base,
+const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port,
+struct evutil_addrinfo **res)
+{
+	int n_found = 0;
+	struct hosts_entry *e;
+	struct evutil_addrinfo *ai=NULL;
+	int f = hints->ai_family;
+	EVDNS_LOCK(base);
+	for (e = find_hosts_entry(base, nodename, NULL); e;
+	    e = find_hosts_entry(base, nodename, e)) {
+		struct evutil_addrinfo *ai_new;
+		++n_found;
+		if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) ||
+		    (e->addr.sa.sa_family == AF_INET6 && f == PF_INET))
+			continue;
+		ai_new = evutil_new_addrinfo(&e->addr.sa, e->addrlen, hints);
+		if (!ai_new) {
+			n_found = 0;
+			goto out;
+		}
+		sockaddr_setport(ai_new->ai_addr, port);
+		ai = evutil_addrinfo_append(ai, ai_new);
+	}
+	EVDNS_UNLOCK(base);
+out:
+	if (n_found) {
+		/* Note that we return an empty answer if we found entries for
+		 * this hostname but none were of the right address type. */
+		*res = ai;
+		return 0;
+	} else {
+		if (ai)
+			evutil_freeaddrinfo(ai);
+		return -1;
+	}
+}
+struct evdns_getaddrinfo_request *
+evdns_getaddrinfo(struct evdns_base *dns_base,
+const char *nodename, const char *servname,
+const struct evutil_addrinfo *hints_in,
+evdns_getaddrinfo_cb cb, void *arg)
+{
+	struct evdns_getaddrinfo_request *data;
+	struct evutil_addrinfo hints;
+	struct evutil_addrinfo *res = NULL;
+	int err;
+	int port = 0;
+	int want_cname = 0;
+	if (!dns_base) {
+		dns_base = current_base;
+		if (!dns_base) {
+			log(EVDNS_LOG_WARN,
+			    "Call to getaddrinfo_async with no "
+			    "evdns_base configured.");
+			cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */
+			return NULL;
+		}
+	}
+	/* If we _must_ answer this immediately, do so. */
+	if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) {
+		res = NULL;
+		err = evutil_getaddrinfo(nodename, servname, hints_in, &res);
+		cb(err, res, arg);
+		return NULL;
+	}
+	if (hints_in) {
+		memcpy(&hints, hints_in, sizeof(hints));
+	} else {
+		memset(&hints, 0, sizeof(hints));
+		hints.ai_family = PF_UNSPEC;
+	}
+	evutil_adjust_hints_for_addrconfig(&hints);
+	/* Now try to see if we _can_ answer immediately. */
+	/* (It would be nice to do this by calling getaddrinfo directly, with
+	 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't
+	 * a reliable way to distinguish the "that wasn't a numeric host!" case
+	 * from any other EAI_NONAME cases.) */
+	err = evutil_getaddrinfo_common(nodename, servname, &hints, &res, &port);
+	if (err != EVUTIL_EAI_NEED_RESOLVE) {
+		cb(err, res, arg);
+		return NULL;
+	}
+	/* If there is an entry in the hosts file, we should give it now. */
+	if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) {
+		cb(0, res, arg);
+		return NULL;
+	}
+	/* Okay, things are serious now. We're going to need to actually
+	 * launch a request.
+	 */
+	data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request));
+	if (!data) {
+		cb(EVUTIL_EAI_MEMORY, NULL, arg);
+		return NULL;
+	}
+	memcpy(&data->hints, &hints, sizeof(data->hints));
+	data->port = (ev_uint16_t)port;
+	data->ipv4_request.type = DNS_IPv4_A;
+	data->ipv6_request.type = DNS_IPv6_AAAA;
+	data->user_cb = cb;
+	data->user_data = arg;
+	data->evdns_base = dns_base;
+	want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME);
+	/* If we are asked for a PF_UNSPEC address, we launch two requests in
+	 * parallel: one for an A address and one for an AAAA address.  We
+	 * can't send just one request, since many servers only answer one
+	 * question per DNS request.
+	 *
+	 * Once we have the answer to one request, we allow for a short
+	 * timeout before we report it, to see if the other one arrives.  If
+	 * they both show up in time, then we report both the answers.
+	 *
+	 * If too many addresses of one type time out or fail, we should stop
+	 * launching those requests. (XXX we don't do that yet.)
+	 */
+	if (hints.ai_family != PF_INET6) {
+		log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p",
+		    nodename, &data->ipv4_request);
+		data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base,
+		    nodename, 0, evdns_getaddrinfo_gotresolve,
+		    &data->ipv4_request);
+		if (want_cname)
+			data->ipv4_request.r->current_req->put_cname_in_ptr =
+			    &data->cname_result;
+	}
+	if (hints.ai_family != PF_INET) {
+		log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p",
+		    nodename, &data->ipv6_request);
+		data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base,
+		    nodename, 0, evdns_getaddrinfo_gotresolve,
+		    &data->ipv6_request);
+		if (want_cname)
+			data->ipv6_request.r->current_req->put_cname_in_ptr =
+			    &data->cname_result;
+	}
+	evtimer_assign(&data->timeout, dns_base->event_base,
+	    evdns_getaddrinfo_timeout_cb, data);
+	if (data->ipv4_request.r || data->ipv6_request.r) {
+		return data;
+	} else {
+		mm_free(data);
+		cb(EVUTIL_EAI_FAIL, NULL, arg);
+		return NULL;
+	}
+}
+void
+evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data)
+{
+	EVDNS_LOCK(data->evdns_base);
+	if (data->request_done) {
+		EVDNS_UNLOCK(data->evdns_base);
+		return;
+	}
+	event_del(&data->timeout);
+	data->user_canceled = 1;
+	if (data->ipv4_request.r)
+		evdns_cancel_request(data->evdns_base, data->ipv4_request.r);
+	if (data->ipv6_request.r)
+		evdns_cancel_request(data->evdns_base, data->ipv6_request.r);
+	EVDNS_UNLOCK(data->evdns_base);
+}

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comparison: ipc/chromium/src/third_party/libevent/evdns.c

ipc/chromium/src/third_party/libevent/evdns.c