10.0-monty merge

includes:
* remove some remnants of "Bug#14521864: MYSQL 5.1 TO 5.5 BUGS PARTITIONING"
* introduce LOCK_share, now LOCK_ha_data is strictly for engines
* rea_create_table() always creates .par file (even in "frm-only" mode)
* fix a 5.6 bug, temp file leak on dummy ALTER TABLE

1 files changed, 3200 insertions, 0 deletions

diff --git a/libevent/evdns.c b/libevent/evdns.c
new file mode 100644
index 00000000000..e13357f1596
--- /dev/null
+++ b/libevent/evdns.c
@@ -0,0 +1,3200 @@
+/* $Id: evdns.c 6979 2006-08-04 18:31:13Z nickm $ */
+
+/* The original version of this module was written by Adam Langley; for
+ * a history of modifications, check out the subversion logs.
+ *
+ * When editing this module, try to keep it re-mergeable by Adam.  Don't
+ * reformat the whitespace, add Tor dependencies, or so on.
+ *
+ * TODO:
+ *   - Support IPv6 and PTR records.
+ *   - Replace all externally visible magic numbers with #defined constants.
+ *   - Write doccumentation for APIs of all external functions.
+ */
+
+/* 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>
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef DNS_USE_FTIME_FOR_ID
+#include <sys/timeb.h>
+#endif
+
+#ifndef DNS_USE_CPU_CLOCK_FOR_ID
+#ifdef HAVE_GETTIMEOFDAY
+#define DNS_USE_GETTIMEOFDAY_FOR_ID     1
+#endif
+#endif
+
+#ifndef DNS_USE_CPU_CLOCK_FOR_ID
+#ifdef HAVE_GETTIMEOFDAY
+#define DNS_USE_GETTIMEOFDAY_FOR_ID     1
+#endif
+#endif
+
+#ifndef DNS_USE_CPU_CLOCK_FOR_ID
+#ifndef DNS_USE_GETTIMEOFDAY_FOR_ID
+#ifndef DNS_USE_OPENSSL_FOR_ID
+#ifndef DNS_USE_FTIME_FOR_ID
+#error Must configure at least one id generation method.
+#error Please see the documentation.
+#endif
+#endif
+#endif
+#endif
+
+/* #define _POSIX_C_SOURCE 200507 */
+#define _GNU_SOURCE
+
+#ifdef DNS_USE_CPU_CLOCK_FOR_ID
+#ifdef DNS_USE_OPENSSL_FOR_ID
+#error Multiple id options selected
+#endif
+#ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
+#error Multiple id options selected
+#endif
+#include <time.h>
+#endif
+
+#ifdef DNS_USE_OPENSSL_FOR_ID
+#ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
+#error Multiple id options selected
+#endif
+#include <openssl/rand.h>
+#endif
+
+#ifndef _FORTIFY_SOURCE
+#define _FORTIFY_SOURCE 3
+#endif
+
+#include <string.h>
+#include <fcntl.h>
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <limits.h>
+#include <sys/stat.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdarg.h>
+
+#include "evdns.h"
+#include "evutil.h"
+#include "log.h"
+#ifdef WIN32
+#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 HAVE_NETINET_IN6_H
+#include <netinet/in6.h>
+#endif
+
+#define EVDNS_LOG_DEBUG 0
+#define EVDNS_LOG_WARN 1
+
+#ifndef HOST_NAME_MAX
+#define HOST_NAME_MAX 255
+#endif
+
+#include <stdio.h>
+
+#undef MIN
+#define MIN(a,b) ((a)<(b)?(a):(b))
+
+#ifdef __USE_ISOC99B
+/* libevent doesn't work without this */
+typedef ev_uint8_t u_char;
+typedef unsigned int uint;
+#endif
+#include <event.h>
+
+#define u64 ev_uint64_t
+#define u32 ev_uint32_t
+#define u16 ev_uint16_t
+#define u8  ev_uint8_t
+
+#ifdef WIN32
+#define open _open
+#define read _read
+#define close _close
+#define strdup _strdup
+#endif
+
+#define MAX_ADDRS 32  /* maximum number of addresses from a single packet */
+/* which we bother recording */
+
+#define TYPE_A         EVDNS_TYPE_A
+#define TYPE_CNAME     5
+#define TYPE_PTR       EVDNS_TYPE_PTR
+#define TYPE_AAAA      EVDNS_TYPE_AAAA
+
+#define CLASS_INET     EVDNS_CLASS_INET
+
+struct request {
+	u8 *request;  /* the dns packet data */
+	unsigned int request_len;
+	int reissue_count;
+	int tx_count;  /* the number of times that this packet has been sent */
+	unsigned int request_type; /* TYPE_PTR or TYPE_A */
+	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 */
+
+	/* 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;
+
+	/* these objects are kept in a circular list */
+	struct request *next, *prev;
+
+	struct event timeout_event;
+
+	u16 trans_id;  /* the transaction id */
+	char request_appended;  /* true if the request pointer is data which follows this struct */
+	char transmit_me;  /* needs to be transmitted */
+};
+
+#ifndef HAVE_STRUCT_IN6_ADDR
+struct in6_addr {
+	u8 s6_addr[16];
+};
+#endif
+
+struct reply {
+	unsigned int type;
+	unsigned int have_answer;
+	union {
+		struct {
+			u32 addrcount;
+			u32 addresses[MAX_ADDRS];
+		} a;
+		struct {
+			u32 addrcount;
+			struct in6_addr addresses[MAX_ADDRS];
+		} aaaa;
+		struct {
+			char name[HOST_NAME_MAX];
+		} ptr;
+	} data;
+};
+
+struct nameserver {
+	int socket;  /* a connected UDP socket */
+	u32 address;
+	u16 port;
+	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 */
+	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 */
+};
+
+static struct request *req_head = NULL, *req_waiting_head = NULL;
+static struct nameserver *server_head = NULL;
+
+/* Represents a local port where we're listening for DNS requests. Right now, */
+/* only UDP is supported. */
+struct evdns_server_port {
+	int 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;
+};
+
+/* 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 : 16; /* The RR type */
+	u16 class : 16; /* 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 */
+	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;
+};
+
+/* helper macro */
+#define OFFSET_OF(st, member) ((off_t) (((char*)&((st*)0)->member)-(char*)0))
+
+/* 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) - OFFSET_OF(struct server_request, base))))
+
+/* The number of good nameservers that we have */
+static int global_good_nameservers = 0;
+
+/* inflight requests are contained in the req_head list */
+/* and are actually going out across the network */
+static int global_requests_inflight = 0;
+/* requests which aren't inflight are in the waiting list */
+/* and are counted here */
+static int global_requests_waiting = 0;
+
+static int global_max_requests_inflight = 64;
+
+static struct timeval global_timeout = {5, 0};  /* 5 seconds */
+static int global_max_reissues = 1;  /* a reissue occurs when we get some errors from the server */
+static int global_max_retransmits = 3;  /* 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 */
+static int global_max_nameserver_timeout = 3;
+
+/* These are the timeout values for nameservers. If we find a nameserver is down */
+/* we try to probe it at intervals as given below. Values are in seconds. */
+static const struct timeval global_nameserver_timeouts[] = {{10, 0}, {60, 0}, {300, 0}, {900, 0}, {3600, 0}};
+static const int global_nameserver_timeouts_length = sizeof(global_nameserver_timeouts)/sizeof(struct timeval);
+
+static struct nameserver *nameserver_pick(void);
+static void evdns_request_insert(struct request *req, struct request **head);
+static void nameserver_ready_callback(int fd, short events, void *arg);
+static int evdns_transmit(void);
+static int evdns_request_transmit(struct request *req);
+static void nameserver_send_probe(struct nameserver *const ns);
+static void search_request_finished(struct request *const);
+static int search_try_next(struct request *const req);
+static int search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg);
+static void evdns_requests_pump_waiting_queue(void);
+static u16 transaction_id_pick(void);
+static struct request *request_new(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(int fd, short events, void *arg);
+
+static int strtoint(const char *const str);
+
+#ifdef WIN32
+static int
+last_error(int sock)
+{
+	int optval, optvallen=sizeof(optval);
+	int err = WSAGetLastError();
+	if (err == WSAEWOULDBLOCK && sock >= 0) {
+		if (getsockopt(sock, SOL_SOCKET, SO_ERROR, (void*)&optval,
+			       &optvallen))
+			return err;
+		if (optval)
+			return optval;
+	}
+	return err;
+
+}
+static int
+error_is_eagain(int err)
+{
+	return err == EAGAIN || err == WSAEWOULDBLOCK;
+}
+static int
+inet_aton(const char *c, struct in_addr *addr)
+{
+	ev_uint32_t r;
+	if (strcmp(c, "255.255.255.255") == 0) {
+		addr->s_addr = 0xffffffffu;
+	} else {
+		r = inet_addr(c);
+		if (r == INADDR_NONE)
+			return 0;
+		addr->s_addr = r;
+	}
+	return 1;
+}
+#else
+#define last_error(sock) (errno)
+#define error_is_eagain(err) ((err) == EAGAIN)
+#endif
+#define CLOSE_SOCKET(s) EVUTIL_CLOSESOCKET(s)
+
+#define ISSPACE(c) isspace((int)(unsigned char)(c))
+#define ISDIGIT(c) isdigit((int)(unsigned char)(c))
+
+static const char *
+debug_ntoa(u32 address)
+{
+	static char buf[32];
+	u32 a = ntohl(address);
+	evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d",
+                      (int)(u8)((a>>24)&0xff),
+                      (int)(u8)((a>>16)&0xff),
+                      (int)(u8)((a>>8 )&0xff),
+  		      (int)(u8)((a    )&0xff));
+	return 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;
+  static char buf[512];
+  if (!evdns_log_fn)
+    return;
+  va_start(args,fmt);
+  evutil_vsnprintf(buf, sizeof(buf), fmt, args);
+  buf[sizeof(buf)-1] = '\0';
+  evdns_log_fn(warn, buf);
+  va_end(args);
+}
+
+#define log _evdns_log
+
+/* This walks the list of inflight requests to find the */
+/* one with a matching transaction id. Returns NULL on */
+/* failure */
+static struct request *
+request_find_from_trans_id(u16 trans_id) {
+	struct request *req = req_head, *const started_at = req_head;
+
+	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(int fd, short events, void *arg) {
+	struct nameserver *const ns = (struct nameserver *) arg;
+        (void)fd;
+        (void)events;
+
+	nameserver_send_probe(ns);
+}
+
+/* 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) {
+	const struct timeval * timeout;
+	(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;
+	}
+
+	timeout =
+	  &global_nameserver_timeouts[MIN(ns->failed_times,
+					  global_nameserver_timeouts_length - 1)];
+	ns->failed_times++;
+
+	if (evtimer_add(&ns->timeout_event, (struct timeval *) timeout) < 0) {
+          log(EVDNS_LOG_WARN,
+              "Error from libevent when adding timer event for %s",
+              debug_ntoa(ns->address));
+          /* ???? Do more? */
+        }
+}
+
+/* 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;
+	/* if this nameserver has already been marked as failed */
+	/* then don't do anything */
+	if (!ns->state) return;
+
+	log(EVDNS_LOG_WARN, "Nameserver %s has failed: %s",
+            debug_ntoa(ns->address), msg);
+	global_good_nameservers--;
+	assert(global_good_nameservers >= 0);
+	if (global_good_nameservers == 0) {
+		log(EVDNS_LOG_WARN, "All nameservers have failed");
+	}
+
+	ns->state = 0;
+	ns->failed_times = 1;
+
+	if (evtimer_add(&ns->timeout_event, (struct timeval *) &global_nameserver_timeouts[0]) < 0) {
+		log(EVDNS_LOG_WARN,
+		    "Error from libevent when adding timer event for %s",
+		    debug_ntoa(ns->address));
+		/* ???? 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 (!global_good_nameservers) return;
+
+	req = req_head;
+	started_at = req_head;
+	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();
+			}
+			req = req->next;
+		} while (req != started_at);
+	}
+}
+
+static void
+nameserver_up(struct nameserver *const ns) {
+	if (ns->state) return;
+	log(EVDNS_LOG_WARN, "Nameserver %s is back up",
+	    debug_ntoa(ns->address));
+	evtimer_del(&ns->timeout_event);
+	ns->state = 1;
+	ns->failed_times = 0;
+	ns->timedout = 0;
+	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. */
+static void
+request_finished(struct request *const req, struct request **head) {
+	if (head) {
+		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;
+		}
+	}
+
+	log(EVDNS_LOG_DEBUG, "Removing timeout for request %lx",
+	    (unsigned long) req);
+	evtimer_del(&req->timeout_event);
+
+	search_request_finished(req);
+	global_requests_inflight--;
+
+	if (!req->request_appended) {
+		/* need to free the request data on it's own */
+		free(req->request);
+	} else {
+		/* the request data is appended onto the header */
+		/* so everything gets free()ed when we: */
+	}
+
+	free(req);
+
+	evdns_requests_pump_waiting_queue();
+}
+
+/* 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;
+	/* 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();
+	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(void) {
+	while (global_requests_inflight < global_max_requests_inflight &&
+	    global_requests_waiting) {
+		struct request *req;
+		/* move a request from the waiting queue to the inflight queue */
+		assert(req_waiting_head);
+		if (req_waiting_head->next == req_waiting_head) {
+			/* only one item in the queue */
+			req = req_waiting_head;
+			req_waiting_head = NULL;
+		} else {
+			req = req_waiting_head;
+			req->next->prev = req->prev;
+			req->prev->next = req->next;
+			req_waiting_head = req->next;
+		}
+
+		global_requests_waiting--;
+		global_requests_inflight++;
+
+		req->ns = nameserver_pick();
+		request_trans_id_set(req, transaction_id_pick());
+
+		evdns_request_insert(req, &req_head);
+		evdns_request_transmit(req);
+		evdns_transmit();
+	}
+}
+
+static void
+reply_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) {
+	switch (req->request_type) {
+	case TYPE_A:
+		if (reply)
+			req->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
+							   reply->data.a.addrcount, ttl,
+						 reply->data.a.addresses,
+							   req->user_pointer);
+		else
+			req->user_callback(err, 0, 0, 0, NULL, req->user_pointer);
+		return;
+	case TYPE_PTR:
+		if (reply) {
+			char *name = reply->data.ptr.name;
+			req->user_callback(DNS_ERR_NONE, DNS_PTR, 1, ttl,
+							   &name, req->user_pointer);
+		} else {
+			req->user_callback(err, 0, 0, 0, NULL,
+							   req->user_pointer);
+		}
+		return;
+	case TYPE_AAAA:
+		if (reply)
+			req->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA,
+							   reply->data.aaaa.addrcount, ttl,
+							   reply->data.aaaa.addresses,
+							   req->user_pointer);
+		else
+			req->user_callback(err, 0, 0, 0, NULL, req->user_pointer);
+                return;
+	}
+	assert(0);
+}
+
+/* this processes a parsed reply packet */
+static void
+reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) {
+	int error;
+	static const int error_codes[] = {
+		DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST,
+		DNS_ERR_NOTIMPL, DNS_ERR_REFUSED
+	};
+
+	if (flags & 0x020f || !reply || !reply->have_answer) {
+		/* there was an error */
+		if (flags & 0x0200) {
+			error = DNS_ERR_TRUNCATED;
+		} else {
+			u16 error_code = (flags & 0x000f) - 1;
+			if (error_code > 4) {
+				error = DNS_ERR_UNKNOWN;
+			} else {
+				error = error_codes[error_code];
+			}
+		}
+
+		switch(error) {
+		case DNS_ERR_NOTIMPL:
+		case DNS_ERR_REFUSED:
+			/* we regard these errors as marking a bad nameserver */
+			if (req->reissue_count < 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 %s; "
+				"will allow the request to time out.",
+				debug_ntoa(req->ns->address));
+			break;
+		default:
+			/* we got a good reply from the nameserver */
+			nameserver_up(req->ns);
+		}
+
+		if (req->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)) {
+				/* 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. */
+				request_finished(req, &req_head);
+				return;
+			}
+		}
+
+		/* all else failed. Pass the failure up */
+		reply_callback(req, 0, error, NULL);
+		request_finished(req, &req_head);
+	} else {
+		/* all ok, tell the user */
+		reply_callback(req, ttl, 0, reply);
+		nameserver_up(req->ns);
+		request_finished(req, &req_head);
+	}
+}
+
+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(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 */
+
+	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;
+
+	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(trans_id);
+	if (!req) return -1;
+
+	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) {
+		/* there was an error */
+		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 (memcmp(tmp_name, cmp_name, strlen (tmp_name)) != 0)	\
+			return (-1); /* we ignore mismatching names */	\
+	} 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;
+	}
+
+	/* 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_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_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_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_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_ADDRS) break;
+		} else {
+			/* skip over any other type of resource */
+			j += datalength;
+		}
+	}
+
+	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, 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;
+
+	/* Get the header fields */
+	GET16(trans_id);
+	GET16(flags);
+	GET16(questions);
+	GET16(answers);
+	GET16(authority);
+	GET16(additional);
+
+	if (flags & 0x8000) return -1; /* Must not be an answer. */
+	flags &= 0x0110; /* Only RD and CD get preserved. */
+
+	server_req = 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 = malloc(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 = strlen(tmp_name);
+		q = 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)
+				free(server_req->base.questions[i]);
+			free(server_req->base.questions);
+		}
+		free(server_req);
+	}
+	return -1;
+
+#undef SKIP_NAME
+#undef GET32
+#undef GET16
+#undef GET8
+}
+
+static u16
+default_transaction_id_fn(void)
+{
+	u16 trans_id;
+#ifdef DNS_USE_CPU_CLOCK_FOR_ID
+	struct timespec ts;
+	static int clkid = -1;
+	if (clkid == -1) {
+		clkid = CLOCK_REALTIME;
+#ifdef CLOCK_MONOTONIC
+		if (clock_gettime(CLOCK_MONOTONIC, &ts) != -1)
+			clkid = CLOCK_MONOTONIC;
+#endif
+	}
+	if (clock_gettime(clkid, &ts) == -1)
+		event_err(1, "clock_gettime");
+	trans_id = ts.tv_nsec & 0xffff;
+#endif
+
+#ifdef DNS_USE_FTIME_FOR_ID
+	struct _timeb tb;
+	_ftime(&tb);
+	trans_id = tb.millitm & 0xffff;
+#endif
+
+#ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
+	struct timeval tv;
+	evutil_gettimeofday(&tv, NULL);
+	trans_id = tv.tv_usec & 0xffff;
+#endif
+
+#ifdef DNS_USE_OPENSSL_FOR_ID
+	if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) {
+		/* in the case that the RAND call fails we back */
+		/* down to using gettimeofday. */
+		/*
+		  struct timeval tv;
+		  evutil_gettimeofday(&tv, NULL);
+		  trans_id = tv.tv_usec & 0xffff;
+		*/
+		abort();
+	}
+#endif
+	return trans_id;
+}
+
+static ev_uint16_t (*trans_id_function)(void) = default_transaction_id_fn;
+
+void
+evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void))
+{
+	if (fn)
+		trans_id_function = fn;
+	else
+		trans_id_function = default_transaction_id_fn;
+}
+
+/* Try to choose a strong transaction id which isn't already in flight */
+static u16
+transaction_id_pick(void) {
+	for (;;) {
+		const struct request *req = req_head, *started_at;
+		u16 trans_id = trans_id_function();
+
+		if (trans_id == 0xffff) continue;
+		/* now check to see if that id is already inflight */
+		req = started_at = req_head;
+		if (req) {
+			do {
+				if (req->trans_id == trans_id) break;
+				req = req->next;
+			} while (req != started_at);
+		}
+		/* we didn't find it, so this is a good id */
+		if (req == started_at) 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(void) {
+	struct nameserver *started_at = server_head, *picked;
+	if (!server_head) return NULL;
+
+	/* if we don't have any good nameservers then there's no */
+	/* point in trying to find one. */
+	if (!global_good_nameservers) {
+		server_head = server_head->next;
+		return server_head;
+	}
+
+	/* remember that nameservers are in a circular list */
+	for (;;) {
+		if (server_head->state) {
+			/* we think this server is currently good */
+			picked = server_head;
+			server_head = server_head->next;
+			return picked;
+		}
+
+		server_head = server_head->next;
+		if (server_head == started_at) {
+			/* all the nameservers seem to be down */
+			/* so we just return this one and hope for the */
+			/* best */
+			assert(global_good_nameservers == 0);
+			picked = server_head;
+			server_head = server_head->next;
+			return picked;
+		}
+	}
+}
+
+static int
+address_is_correct(struct nameserver *ns, struct sockaddr *sa, socklen_t slen)
+{
+	struct sockaddr_in *sin = (struct sockaddr_in*) sa;
+	if (sa->sa_family != AF_INET || slen != sizeof(struct sockaddr_in))
+		return 0;
+	if (sin->sin_addr.s_addr != ns->address)
+		return 0;
+	return 1;
+}
+
+/* this is called when a namesever socket is ready for reading */
+static void
+nameserver_read(struct nameserver *ns) {
+	u8 packet[1500];
+	struct sockaddr_storage ss;
+	socklen_t addrlen = sizeof(ss);
+
+	for (;;) {
+          	const int r = recvfrom(ns->socket, packet, sizeof(packet), 0,
+		    (struct sockaddr*)&ss, &addrlen);
+		if (r < 0) {
+			int err = last_error(ns->socket);
+			if (error_is_eagain(err)) return;
+			nameserver_failed(ns, strerror(err));
+			return;
+		}
+		if (!address_is_correct(ns, (struct sockaddr*)&ss, addrlen)) {
+			log(EVDNS_LOG_WARN, "Address mismatch on received "
+			    "DNS packet.");
+			return;
+		}
+		ns->timedout = 0;
+		reply_parse(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;
+	socklen_t addrlen;
+	int r;
+
+	for (;;) {
+		addrlen = sizeof(struct sockaddr_storage);
+		r = recvfrom(s->socket, packet, sizeof(packet), 0,
+					 (struct sockaddr*) &addr, &addrlen);
+		if (r < 0) {
+			int err = last_error(s->socket);
+			if (error_is_eagain(err)) return;
+			log(EVDNS_LOG_WARN, "Error %s (%d) while reading request.",
+				strerror(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)
+{
+	while (port->pending_replies) {
+		struct server_request *req = port->pending_replies;
+		int r = sendto(port->socket, req->response, req->response_len, 0,
+			   (struct sockaddr*) &req->addr, req->addrlen);
+		if (r < 0) {
+			int err = last_error(port->socket);
+			if (error_is_eagain(err))
+				return;
+			log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", strerror(err), err);
+		}
+		if (server_request_free(req)) {
+			/* we released the last reference to req->port. */
+			return;
+		}
+	}
+
+	/* We have no more pending requests; stop listening for 'writeable' events. */
+	(void) event_del(&port->event);
+	event_set(&port->event, 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) {
+	if (ns->write_waiting == waiting) return;
+
+	ns->write_waiting = waiting;
+	(void) event_del(&ns->event);
+	event_set(&ns->event, ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST,
+			nameserver_ready_callback, ns);
+	if (event_add(&ns->event, NULL) < 0) {
+          log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s",
+              debug_ntoa(ns->address));
+          /* ???? 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(int fd, short events, void *arg) {
+	struct nameserver *ns = (struct nameserver *) arg;
+        (void)fd;
+
+	if (events & EV_WRITE) {
+		ns->choked = 0;
+		if (!evdns_transmit()) {
+			nameserver_write_waiting(ns, 0);
+		}
+	}
+	if (events & EV_READ) {
+		nameserver_read(ns);
+	}
+}
+
+/* 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(int fd, short events, void *arg) {
+	struct evdns_server_port *port = (struct evdns_server_port *) arg;
+	(void) fd;
+
+	if (events & EV_WRITE) {
+		port->choked = 0;
+		server_port_flush(port);
+	}
+	if (events & EV_READ) {
+		server_port_read(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)
+		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 = 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 int 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 unsigned int 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++] = label_len;
+
+			memcpy(buf + j, start, end - start);
+			j += end - start;
+			break;
+		} else {
+			/* append length of the label. */
+			const unsigned int 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++] = label_len;
+
+			memcpy(buf + j, start, name - start);
+			j += name - start;
+			/* 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 int
+evdns_request_len(const int 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 int 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(int socket, int is_tcp, evdns_request_callback_fn_type cb, void *user_data)
+{
+	struct evdns_server_port *port;
+	if (!(port = malloc(sizeof(struct evdns_server_port))))
+		return NULL;
+	memset(port, 0, sizeof(struct evdns_server_port));
+
+	assert(!is_tcp); /* TCP sockets not yet implemented */
+	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;
+
+	event_set(&port->event, port->socket, EV_READ | EV_PERSIST,
+			  server_port_ready_callback, port);
+	event_add(&port->event, NULL); /* check return. */
+	return port;
+}
+
+/* exported function */
+void
+evdns_close_server_port(struct evdns_server_port *port)
+{
+	if (--port->refcnt == 0)
+		server_port_free(port);
+	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;
+
+	if (req->response) /* have we already answered? */
+		return (-1);
+
+	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:
+		return (-1);
+	}
+	while (*itemp) {
+		itemp = &((*itemp)->next);
+	}
+	item = malloc(sizeof(struct server_reply_item));
+	if (!item)
+		return -1;
+	item->next = NULL;
+	if (!(item->name = strdup(name))) {
+		free(item);
+		return -1;
+	}
+	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 = strdup(data))) {
+				free(item->name);
+				free(item);
+				return -1;
+			}
+			item->datalen = (u16)-1;
+		} else {
+			if (!(item->data = malloc(datalen))) {
+				free(item->name);
+				free(item);
+				return -1;
+			}
+			item->datalen = datalen;
+			memcpy(item->data, data, datalen);
+		}
+	}
+
+	*itemp = item;
+	++(*countp);
+	return 0;
+}
+
+/* exported function */
+int
+evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, 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, 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];
+	assert(in || inaddr_name);
+	assert(!(in && inaddr_name));
+	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);
+}
+
+
+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 = 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;
+	if (!req->response) {
+		if ((r = evdns_server_request_format_response(req, err))<0)
+			return r;
+	}
+
+	r = sendto(port->socket, req->response, req->response_len, 0,
+			   (struct sockaddr*) &req->addr, req->addrlen);
+	if (r<0) {
+		int sock_err = last_error(port->socket);
+		if (! error_is_eagain(sock_err))
+			return -1;
+
+		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_set(&port->event, 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");
+			}
+
+		}
+
+		return 1;
+	}
+	if (server_request_free(req))
+		return 0;
+
+	if (port->pending_replies)
+		server_port_flush(port);
+
+	return 0;
+}
+
+/* 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;
+			free(victim->name);
+			if (victim->data)
+				free(victim->data);
+			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;
+	if (req->base.questions) {
+		for (i = 0; i < req->base.nquestions; ++i)
+			free(req->base.questions[i]);
+		free(req->base.questions);
+	}
+
+	if (req->port) {
+		if (req->port->pending_replies == req) {
+			if (req->next_pending)
+				req->port->pending_replies = req->next_pending;
+			else
+				req->port->pending_replies = NULL;
+		}
+		rc = --req->port->refcnt;
+	}
+
+	if (req->response) {
+		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) {
+		server_port_free(req->port);
+		free(req);
+		return (1);
+	}
+	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)
+{
+	assert(port);
+	assert(!port->refcnt);
+	assert(!port->pending_replies);
+	if (port->socket > 0) {
+		CLOSE_SOCKET(port->socket);
+		port->socket = -1;
+	}
+	(void) event_del(&port->event);
+	/* XXXX actually free the port? -NM */
+}
+
+/* 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(int fd, short events, void *arg) {
+	struct request *const req = (struct request *) arg;
+        (void) fd;
+        (void) events;
+
+	log(EVDNS_LOG_DEBUG, "Request %lx timed out", (unsigned long) arg);
+
+	req->ns->timedout++;
+	if (req->ns->timedout > global_max_nameserver_timeout) {
+		req->ns->timedout = 0;
+		nameserver_failed(req->ns, "request timed out.");
+	}
+
+	(void) evtimer_del(&req->timeout_event);
+	if (req->tx_count >= global_max_retransmits) {
+		/* this request has failed */
+		reply_callback(req, 0, DNS_ERR_TIMEOUT, NULL);
+		request_finished(req, &req_head);
+	} else {
+		/* retransmit it */
+		evdns_request_transmit(req);
+	}
+}
+
+/* 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) {
+	struct sockaddr_in sin;
+	int r;
+	memset(&sin, 0, sizeof(sin));
+	sin.sin_addr.s_addr = req->ns->address;
+	sin.sin_port = req->ns->port;
+	sin.sin_family = AF_INET;
+
+	r = sendto(server->socket, req->request, req->request_len, 0,
+	    (struct sockaddr*)&sin, sizeof(sin));
+	if (r < 0) {
+		int err = last_error(server->socket);
+		if (error_is_eagain(err)) return 1;
+		nameserver_failed(req->ns, strerror(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;
+
+	/* if we fail to send this packet then this flag marks it */
+	/* for evdns_transmit */
+	req->transmit_me = 1;
+	if (req->trans_id == 0xffff) abort();
+
+	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 in some other way */
+		retcode = 1;
+		/* fall through */
+	default:
+		/* all ok */
+		log(EVDNS_LOG_DEBUG,
+		    "Setting timeout for request %lx", (unsigned long) req);
+		if (evtimer_add(&req->timeout_event, &global_timeout) < 0) {
+                  log(EVDNS_LOG_WARN,
+		      "Error from libevent when adding timer for request %lx",
+                      (unsigned long) 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_NONE || result == DNS_ERR_NOTEXIST) {
+		/* this is a good reply */
+		nameserver_up(ns);
+	} else nameserver_probe_failed(ns);
+}
+
+static void
+nameserver_send_probe(struct nameserver *const ns) {
+	struct request *req;
+	/* here we need to send a probe to a given nameserver */
+	/* in the hope that it is up now. */
+
+  	log(EVDNS_LOG_DEBUG, "Sending probe to %s", debug_ntoa(ns->address));
+
+	req = request_new(TYPE_A, "www.google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns);
+        if (!req) return;
+	/* we force this into the inflight queue no matter what */
+	request_trans_id_set(req, transaction_id_pick());
+	req->ns = ns;
+	request_submit(req);
+}
+
+/* returns: */
+/*   0 didn't try to transmit anything */
+/*   1 tried to transmit something */
+static int
+evdns_transmit(void) {
+	char did_try_to_transmit = 0;
+
+	if (req_head) {
+		struct request *const started_at = req_head, *req = req_head;
+		/* 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_count_nameservers(void)
+{
+	const struct nameserver *server = server_head;
+	int n = 0;
+	if (!server)
+		return 0;
+	do {
+		++n;
+		server = server->next;
+	} while (server != server_head);
+	return n;
+}
+
+/* exported function */
+int
+evdns_clear_nameservers_and_suspend(void)
+{
+	struct nameserver *server = server_head, *started_at = server_head;
+	struct request *req = req_head, *req_started_at = req_head;
+
+	if (!server)
+		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->socket >= 0)
+			CLOSE_SOCKET(server->socket);
+		free(server);
+		if (next == started_at)
+			break;
+		server = next;
+	}
+	server_head = NULL;
+	global_good_nameservers = 0;
+
+	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;
+
+		global_requests_waiting++;
+		evdns_request_insert(req, &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.*/
+		req_waiting_head = req_waiting_head->prev;
+
+		if (next == req_started_at)
+			break;
+		req = next;
+	}
+	req_head = NULL;
+	global_requests_inflight = 0;
+
+	return 0;
+}
+
+
+/* exported function */
+int
+evdns_resume(void)
+{
+	evdns_requests_pump_waiting_queue();
+	return 0;
+}
+
+static int
+_evdns_nameserver_add_impl(unsigned long int address, int port) {
+	/* first check to see if we already have this nameserver */
+
+	const struct nameserver *server = server_head, *const started_at = server_head;
+	struct nameserver *ns;
+	int err = 0;
+	if (server) {
+		do {
+			if (server->address == address) return 3;
+			server = server->next;
+		} while (server != started_at);
+	}
+
+	ns = (struct nameserver *) malloc(sizeof(struct nameserver));
+        if (!ns) return -1;
+
+	memset(ns, 0, sizeof(struct nameserver));
+
+	evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
+
+	ns->socket = socket(PF_INET, SOCK_DGRAM, 0);
+	if (ns->socket < 0) { err = 1; goto out1; }
+        evutil_make_socket_nonblocking(ns->socket);
+
+	ns->address = address;
+	ns->port = htons(port);
+	ns->state = 1;
+	event_set(&ns->event, 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", debug_ntoa(address));
+
+	/* insert this nameserver into the list of them */
+	if (!server_head) {
+		ns->next = ns->prev = ns;
+		server_head = ns;
+	} else {
+		ns->next = server_head->next;
+		ns->prev = server_head;
+		server_head->next = ns;
+		if (server_head->prev == server_head) {
+			server_head->prev = ns;
+		}
+	}
+
+	global_good_nameservers++;
+
+	return 0;
+
+out2:
+	CLOSE_SOCKET(ns->socket);
+out1:
+	free(ns);
+	log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", debug_ntoa(address), err);
+	return err;
+}
+
+/* exported function */
+int
+evdns_nameserver_add(unsigned long int address) {
+	return _evdns_nameserver_add_impl(address, 53);
+}
+
+/* exported function */
+int
+evdns_nameserver_ip_add(const char *ip_as_string) {
+	struct in_addr ina;
+	int port;
+	char buf[20];
+	const char *cp;
+	cp = strchr(ip_as_string, ':');
+	if (! cp) {
+		cp = ip_as_string;
+		port = 53;
+	} else {
+		port = strtoint(cp+1);
+		if (port < 0 || port > 65535) {
+			return 4;
+		}
+		if ((cp-ip_as_string) >= (int)sizeof(buf)) {
+			return 4;
+		}
+		memcpy(buf, ip_as_string, cp-ip_as_string);
+		buf[cp-ip_as_string] = '\0';
+		cp = buf;
+	}
+	if (!inet_aton(cp, &ina)) {
+		return 4;
+	}
+	return _evdns_nameserver_add_impl(ina.s_addr, port);
+}
+
+/* insert into the tail of the queue */
+static void
+evdns_request_insert(struct request *req, struct request **head) {
+	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(int type, const char *name, int flags,
+    evdns_callback_type callback, void *user_ptr) {
+	const char issuing_now =
+	    (global_requests_inflight < global_max_requests_inflight) ? 1 : 0;
+
+	const int name_len = strlen(name);
+	const int request_max_len = evdns_request_len(name_len);
+	const u16 trans_id = issuing_now ? transaction_id_pick() : 0xffff;
+	/* the request data is alloced in a single block with the header */
+	struct request *const req =
+	    (struct request *) malloc(sizeof(struct request) + request_max_len);
+	int rlen;
+        (void) flags;
+
+        if (!req) return NULL;
+	memset(req, 0, sizeof(struct request));
+
+	evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req);
+
+	/* 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() : NULL;
+	req->next = req->prev = NULL;
+
+	return req;
+err1:
+	free(req);
+	return NULL;
+}
+
+static void
+request_submit(struct request *const 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);
+		global_requests_inflight++;
+		evdns_request_transmit(req);
+	} else {
+		evdns_request_insert(req, &req_waiting_head);
+		global_requests_waiting++;
+	}
+}
+
+/* exported function */
+int evdns_resolve_ipv4(const char *name, int flags,
+    evdns_callback_type callback, void *ptr) {
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
+	if (flags & DNS_QUERY_NO_SEARCH) {
+		struct request *const req =
+			request_new(TYPE_A, name, flags, callback, ptr);
+		if (req == NULL)
+			return (1);
+		request_submit(req);
+		return (0);
+	} else {
+		return (search_request_new(TYPE_A, name, flags, callback, ptr));
+	}
+}
+
+/* exported function */
+int evdns_resolve_ipv6(const char *name, int flags,
+					   evdns_callback_type callback, void *ptr) {
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
+	if (flags & DNS_QUERY_NO_SEARCH) {
+		struct request *const req =
+			request_new(TYPE_AAAA, name, flags, callback, ptr);
+		if (req == NULL)
+			return (1);
+		request_submit(req);
+		return (0);
+	} else {
+		return (search_request_new(TYPE_AAAA, name, flags, callback, ptr));
+	}
+}
+
+int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
+	char buf[32];
+	struct request *req;
+	u32 a;
+	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));
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
+	req = request_new(TYPE_PTR, buf, flags, callback, ptr);
+	if (!req) return 1;
+	request_submit(req);
+	return 0;
+}
+
+int evdns_resolve_reverse_ipv6(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 request *req;
+	int i;
+	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++ = '.';
+	}
+	assert(cp + strlen("ip6.arpa") < buf+sizeof(buf));
+	memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1);
+	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
+	req = request_new(TYPE_PTR, buf, flags, callback, ptr);
+	if (!req) return 1;
+	request_submit(req);
+	return 0;
+}
+
+/*/////////////////////////////////////////////////////////////////// */
+/* 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 struct search_state *global_search_state = NULL;
+
+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;
+			free(dom);
+		}
+		free(state);
+	}
+}
+
+static struct search_state *
+search_state_new(void) {
+	struct search_state *state = (struct search_state *) 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(void) {
+	search_state_decref(global_search_state);
+
+	global_search_state = search_state_new();
+}
+
+/* exported function */
+void
+evdns_search_clear(void) {
+	search_postfix_clear();
+}
+
+static void
+search_postfix_add(const char *domain) {
+	int domain_len;
+	struct search_domain *sdomain;
+	while (domain[0] == '.') domain++;
+	domain_len = strlen(domain);
+
+	if (!global_search_state) global_search_state = search_state_new();
+        if (!global_search_state) return;
+	global_search_state->num_domains++;
+
+	sdomain = (struct search_domain *) malloc(sizeof(struct search_domain) + domain_len);
+        if (!sdomain) return;
+	memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len);
+	sdomain->next = global_search_state->head;
+	sdomain->len = domain_len;
+
+	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(void) {
+	struct search_domain *cur, *prev = NULL, *next;
+	cur = global_search_state->head;
+	while (cur) {
+		next = cur->next;
+		cur->next = prev;
+		prev = cur;
+		cur = next;
+	}
+
+	global_search_state->head = prev;
+}
+
+/* exported function */
+void
+evdns_search_add(const char *domain) {
+	search_postfix_add(domain);
+}
+
+/* exported function */
+void
+evdns_search_ndots_set(const int ndots) {
+	if (!global_search_state) global_search_state = search_state_new();
+        if (!global_search_state) return;
+	global_search_state->ndots = ndots;
+}
+
+static void
+search_set_from_hostname(void) {
+	char hostname[HOST_NAME_MAX + 1], *domainname;
+
+	search_postfix_clear();
+	if (gethostname(hostname, sizeof(hostname))) return;
+	domainname = strchr(hostname, '.');
+	if (!domainname) return;
+	search_postfix_add(domainname);
+}
+
+/* warning: returns malloced string */
+static char *
+search_make_new(const struct search_state *const state, int n, const char *const base_name) {
+	const int 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 *) 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 */
+	abort();
+	return NULL; /* unreachable; stops warnings in some compilers. */
+}
+
+static int
+search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg) {
+	assert(type == TYPE_A || type == TYPE_AAAA);
+	if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) &&
+	     global_search_state &&
+		 global_search_state->num_domains) {
+		/* we have some domains to search */
+		struct request *req;
+		if (string_num_dots(name) >= global_search_state->ndots) {
+			req = request_new(type, name, flags, user_callback, user_arg);
+			if (!req) return 1;
+			req->search_index = -1;
+		} else {
+			char *const new_name = search_make_new(global_search_state, 0, name);
+                        if (!new_name) return 1;
+			req = request_new(type, new_name, flags, user_callback, user_arg);
+			free(new_name);
+			if (!req) return 1;
+			req->search_index = 0;
+		}
+		req->search_origname = strdup(name);
+		req->search_state = global_search_state;
+		req->search_flags = flags;
+		global_search_state->refcount++;
+		request_submit(req);
+		return 0;
+	} else {
+		struct request *const req = request_new(type, name, flags, user_callback, user_arg);
+		if (!req) return 1;
+		request_submit(req);
+		return 0;
+	}
+}
+
+/* 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 request *const req) {
+	if (req->search_state) {
+		/* it is part of a search */
+		char *new_name;
+		struct request *newreq;
+		req->search_index++;
+		if (req->search_index >= req->search_state->num_domains) {
+			/* no more postfixes to try, however we may need to try */
+			/* this name without a postfix */
+			if (string_num_dots(req->search_origname) < req->search_state->ndots) {
+				/* yep, we need to try it raw */
+				newreq = request_new(req->request_type, req->search_origname, req->search_flags, req->user_callback, req->user_pointer);
+				log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", req->search_origname);
+				if (newreq) {
+					request_submit(newreq);
+					return 0;
+				}
+			}
+			return 1;
+		}
+
+		new_name = search_make_new(req->search_state, req->search_index, req->search_origname);
+                if (!new_name) return 1;
+		log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, req->search_index);
+		newreq = request_new(req->request_type, new_name, req->search_flags, req->user_callback, req->user_pointer);
+		free(new_name);
+		if (!newreq) return 1;
+		newreq->search_origname = req->search_origname;
+		req->search_origname = NULL;
+		newreq->search_state = req->search_state;
+		newreq->search_flags = req->search_flags;
+		newreq->search_index = req->search_index;
+		newreq->search_state->refcount++;
+		request_submit(newreq);
+		return 0;
+	}
+	return 1;
+}
+
+static void
+search_request_finished(struct request *const req) {
+	if (req->search_state) {
+		search_state_decref(req->search_state);
+		req->search_state = NULL;
+	}
+	if (req->search_origname) {
+		free(req->search_origname);
+		req->search_origname = NULL;
+	}
+}
+
+/*/////////////////////////////////////////////////////////////////// */
+/* Parsing resolv.conf files */
+
+static void
+evdns_resolv_set_defaults(int flags) {
+	/* if the file isn't found then we assume a local resolver */
+	if (flags & DNS_OPTION_SEARCH) search_set_from_hostname();
+	if (flags & DNS_OPTION_NAMESERVERS) evdns_nameserver_ip_add("127.0.0.1");
+}
+
+#ifndef HAVE_STRTOK_R
+static char *
+strtok_r(char *s, const char *delim, char **state) {
+	return strtok(s, delim);
+}
+#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;
+}
+
+/* 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;
+}
+
+/* exported function */
+int
+evdns_set_option(const char *option, const char *val, int flags)
+{
+	if (!strncmp(option, "ndots:", 6)) {
+		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 (!global_search_state) global_search_state = search_state_new();
+		if (!global_search_state) return -1;
+		global_search_state->ndots = ndots;
+	} else if (!strncmp(option, "timeout:", 8)) {
+		const int timeout = strtoint(val);
+		if (timeout == -1) return -1;
+		if (!(flags & DNS_OPTION_MISC)) return 0;
+		log(EVDNS_LOG_DEBUG, "Setting timeout to %d", timeout);
+		global_timeout.tv_sec = timeout;
+	} else if (!strncmp(option, "max-timeouts:", 12)) {
+		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);
+		global_max_nameserver_timeout = maxtimeout;
+	} else if (!strncmp(option, "max-inflight:", 13)) {
+		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);
+		global_max_requests_inflight = maxinflight;
+	} else if (!strncmp(option, "attempts:", 9)) {
+		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);
+		global_max_retransmits = retries;
+	}
+	return 0;
+}
+
+static void
+resolv_conf_parse_line(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);
+	if (!first_token) return;
+
+	if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) {
+		const char *const nameserver = NEXT_TOKEN;
+		struct in_addr ina;
+
+		if (inet_aton(nameserver, &ina)) {
+			/* address is valid */
+			evdns_nameserver_add(ina.s_addr);
+		}
+	} else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) {
+		const char *const domain = NEXT_TOKEN;
+		if (domain) {
+			search_postfix_clear();
+			search_postfix_add(domain);
+		}
+	} else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) {
+		const char *domain;
+		search_postfix_clear();
+
+		while ((domain = NEXT_TOKEN)) {
+			search_postfix_add(domain);
+		}
+		search_reverse();
+	} else if (!strcmp(first_token, "options")) {
+		const char *option;
+		while ((option = NEXT_TOKEN)) {
+			const char *val = strchr(option, ':');
+			evdns_set_option(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_resolv_conf_parse(int flags, const char *const filename) {
+	struct stat st;
+	int fd, n, r;
+	u8 *resolv;
+	char *start;
+	int err = 0;
+
+	log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
+		evdns_resolv_set_defaults(flags);
+		return 1;
+	}
+
+	if (fstat(fd, &st)) { err = 2; goto out1; }
+	if (!st.st_size) {
+		evdns_resolv_set_defaults(flags);
+		err = (flags & DNS_OPTION_NAMESERVERS) ? 6 : 0;
+		goto out1;
+	}
+	if (st.st_size > 65535) { err = 3; goto out1; }  /* no resolv.conf should be any bigger */
+
+	resolv = (u8 *) malloc((size_t)st.st_size + 1);
+	if (!resolv) { err = 4; goto out1; }
+
+	n = 0;
+	while ((r = read(fd, resolv+n, (size_t)st.st_size-n)) > 0) {
+		n += r;
+		if (n == st.st_size)
+			break;
+		assert(n < st.st_size);
+ 	}
+	if (r < 0) { err = 5; goto out2; }
+	resolv[n] = 0;	 /* we malloced an extra byte; this should be fine. */
+
+	start = (char *) resolv;
+	for (;;) {
+		char *const newline = strchr(start, '\n');
+		if (!newline) {
+			resolv_conf_parse_line(start, flags);
+			break;
+		} else {
+			*newline = 0;
+			resolv_conf_parse_line(start, flags);
+			start = newline + 1;
+		}
+	}
+
+	if (!server_head && (flags & DNS_OPTION_NAMESERVERS)) {
+		/* no nameservers were configured. */
+		evdns_nameserver_ip_add("127.0.0.1");
+		err = 6;
+	}
+	if (flags & DNS_OPTION_SEARCH && (!global_search_state || global_search_state->num_domains == 0)) {
+		search_set_from_hostname();
+	}
+
+out2:
+	free(resolv);
+out1:
+	close(fd);
+	return err;
+}
+
+#ifdef WIN32
+/* Add multiple nameservers from a space-or-comma-separated list. */
+static int
+evdns_nameserver_ip_add_line(const char *ips) {
+	const char *addr;
+	char *buf;
+	int r;
+	while (*ips) {
+		while (ISSPACE(*ips) || *ips == ',' || *ips == '\t')
+			++ips;
+		addr = ips;
+		while (ISDIGIT(*ips) || *ips == '.' || *ips == ':')
+			++ips;
+		buf = malloc(ips-addr+1);
+		if (!buf) return 4;
+		memcpy(buf, addr, ips-addr);
+		buf[ips-addr] = '\0';
+		r = evdns_nameserver_ip_add(buf);
+		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(void)
+{
+	/* 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;
+
+	if (!(handle = LoadLibrary("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 = 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) {
+		free(buf);
+		buf = 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;
+		}
+	}
+
+	assert(fixed);
+	added_any = 0;
+	ns = &(fixed->DnsServerList);
+	while (ns) {
+		r = evdns_nameserver_ip_add_line(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;
+			goto done;
+		} else {
+			log(EVDNS_LOG_DEBUG,"Succesfully added %s as nameserver",ns->IpAddress.String);
+		}
+
+		added_any++;
+		ns = ns->Next;
+	}
+
+	if (!added_any) {
+		log(EVDNS_LOG_DEBUG, "No nameservers added.");
+		status = -1;
+	}
+
+ done:
+	if (buf)
+		free(buf);
+	if (handle)
+		FreeLibrary(handle);
+	return status;
+}
+
+static int
+config_nameserver_from_reg_key(HKEY key, const char *subkey)
+{
+	char *buf;
+	DWORD bufsz = 0, type = 0;
+	int status = 0;
+
+	if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz)
+	    != ERROR_MORE_DATA)
+		return -1;
+	if (!(buf = malloc(bufsz)))
+		return -1;
+
+	if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
+	    == ERROR_SUCCESS && bufsz > 1) {
+		status = evdns_nameserver_ip_add_line(buf);
+	}
+
+	free(buf);
+	return status;
+}
+
+#define SERVICES_KEY "System\\CurrentControlSet\\Services\\"
+#define WIN_NS_9X_KEY  SERVICES_KEY "VxD\\MSTCP"
+#define WIN_NS_NT_KEY  SERVICES_KEY "Tcpip\\Parameters"
+
+static int
+load_nameservers_from_registry(void)
+{
+	int found = 0;
+	int r;
+#define TRY(k, name) \
+	if (!found && config_nameserver_from_reg_key(k,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);						\
+	}
+
+	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, "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_config_windows_nameservers(void)
+{
+	if (load_nameservers_with_getnetworkparams() == 0)
+		return 0;
+	return load_nameservers_from_registry();
+}
+#endif
+
+int
+evdns_init(void)
+{
+	int res = 0;
+#ifdef WIN32
+	res = evdns_config_windows_nameservers();
+#else
+	res = evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
+#endif
+
+	return (res);
+}
+
+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";
+	default: return "[Unknown error code]";
+    }
+}
+
+void
+evdns_shutdown(int fail_requests)
+{
+	struct nameserver *server, *server_next;
+	struct search_domain *dom, *dom_next;
+
+	while (req_head) {
+		if (fail_requests)
+			reply_callback(req_head, 0, DNS_ERR_SHUTDOWN, NULL);
+		request_finished(req_head, &req_head);
+	}
+	while (req_waiting_head) {
+		if (fail_requests)
+			reply_callback(req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL);
+		request_finished(req_waiting_head, &req_waiting_head);
+	}
+	global_requests_inflight = global_requests_waiting = 0;
+
+	for (server = server_head; server; server = server_next) {
+		server_next = server->next;
+		if (server->socket >= 0)
+			CLOSE_SOCKET(server->socket);
+		(void) event_del(&server->event);
+		if (server->state == 0)
+                        (void) event_del(&server->timeout_event);
+		free(server);
+		if (server_next == server_head)
+			break;
+	}
+	server_head = NULL;
+	global_good_nameservers = 0;
+
+	if (global_search_state) {
+		for (dom = global_search_state->head; dom; dom = dom_next) {
+			dom_next = dom->next;
+			free(dom);
+		}
+		free(global_search_state);
+		global_search_state = NULL;
+	}
+	evdns_log_fn = NULL;
+}
+
+#ifdef EVDNS_MAIN
+void
+main_callback(int result, char type, int count, int ttl,
+			  void *addrs, void *orig) {
+	char *n = (char*)orig;
+	int i;
+	for (i = 0; i < count; ++i) {
+		if (type == DNS_IPv4_A) {
+			printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i]));
+		} else if (type == DNS_PTR) {
+			printf("%s: %s\n", n, ((char**)addrs)[i]);
+		}
+	}
+	if (!count) {
+		printf("%s: No answer (%d)\n", n, result);
+	}
+	fflush(stdout);
+}
+void
+evdns_server_callback(struct evdns_server_request *req, void *data)
+{
+	int i, r;
+	(void)data;
+	/* dummy; give 192.168.11.11 as an answer for all A questions,
+	 *	give foo.bar.example.com as an answer for all PTR questions. */
+	for (i = 0; i < req->nquestions; ++i) {
+		u32 ans = htonl(0xc0a80b0bUL);
+		if (req->questions[i]->type == EVDNS_TYPE_A &&
+			req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
+			printf(" -- replying for %s (A)\n", req->questions[i]->name);
+			r = evdns_server_request_add_a_reply(req, req->questions[i]->name,
+										  1, &ans, 10);
+			if (r<0)
+				printf("eeep, didn't work.\n");
+		} else if (req->questions[i]->type == EVDNS_TYPE_PTR &&
+				   req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
+			printf(" -- replying for %s (PTR)\n", req->questions[i]->name);
+			r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name,
+											"foo.bar.example.com", 10);
+		} else {
+			printf(" -- skipping %s [%d %d]\n", req->questions[i]->name,
+				   req->questions[i]->type, req->questions[i]->dns_question_class);
+		}
+	}
+
+	r = evdns_request_respond(req, 0);
+	if (r<0)
+		printf("eeek, couldn't send reply.\n");
+}
+
+void
+logfn(int is_warn, const char *msg) {
+  (void) is_warn;
+  fprintf(stderr, "%s\n", msg);
+}
+int
+main(int c, char **v) {
+	int idx;
+	int reverse = 0, verbose = 1, servertest = 0;
+	if (c<2) {
+		fprintf(stderr, "syntax: %s [-x] [-v] hostname\n", v[0]);
+		fprintf(stderr, "syntax: %s [-servertest]\n", v[0]);
+		return 1;
+	}
+	idx = 1;
+	while (idx < c && v[idx][0] == '-') {
+		if (!strcmp(v[idx], "-x"))
+			reverse = 1;
+		else if (!strcmp(v[idx], "-v"))
+			verbose = 1;
+		else if (!strcmp(v[idx], "-servertest"))
+			servertest = 1;
+		else
+			fprintf(stderr, "Unknown option %s\n", v[idx]);
+		++idx;
+	}
+	event_init();
+	if (verbose)
+		evdns_set_log_fn(logfn);
+	evdns_resolv_conf_parse(DNS_OPTION_NAMESERVERS, "/etc/resolv.conf");
+	if (servertest) {
+		int sock;
+		struct sockaddr_in my_addr;
+		sock = socket(PF_INET, SOCK_DGRAM, 0);
+                evutil_make_socket_nonblocking(sock);
+		my_addr.sin_family = AF_INET;
+		my_addr.sin_port = htons(10053);
+		my_addr.sin_addr.s_addr = INADDR_ANY;
+		if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) {
+			perror("bind");
+			exit(1);
+		}
+		evdns_add_server_port(sock, 0, evdns_server_callback, NULL);
+	}
+	for (; idx < c; ++idx) {
+		if (reverse) {
+			struct in_addr addr;
+			if (!inet_aton(v[idx], &addr)) {
+				fprintf(stderr, "Skipping non-IP %s\n", v[idx]);
+				continue;
+			}
+			fprintf(stderr, "resolving %s...\n",v[idx]);
+			evdns_resolve_reverse(&addr, 0, main_callback, v[idx]);
+		} else {
+			fprintf(stderr, "resolving (fwd) %s...\n",v[idx]);
+			evdns_resolve_ipv4(v[idx], 0, main_callback, v[idx]);
+		}
+	}
+	fflush(stdout);
+	event_dispatch();
+	return 0;
+}
+#endif