xref: /NextBSD/contrib/ntp/sntp/libevent/evutil.c (revision 287e3b14e9552995def1802ec9c5034f4adf28ec)

/*
 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
 *
 * 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.
 */

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

#ifdef _WIN32
#include <winsock2.h>
#include <ws2tcpip.h>
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#include <io.h>
#include <tchar.h>
#include <process.h>
#undef _WIN32_WINNT
/* For structs needed by GetAdaptersAddresses */
#define _WIN32_WINNT 0x0501
#include <iphlpapi.h>
#endif

#include <sys/types.h>
#ifdef EVENT__HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef EVENT__HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef EVENT__HAVE_FCNTL_H
#include <fcntl.h>
#endif
#ifdef EVENT__HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#ifdef EVENT__HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef EVENT__HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif
#ifdef EVENT__HAVE_NETINET_TCP_H
#include <netinet/tcp.h>
#endif
#ifdef EVENT__HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#include <time.h>
#include <sys/stat.h>
#ifdef EVENT__HAVE_IFADDRS_H
#include <ifaddrs.h>
#endif

#include "event2/util.h"
#include "util-internal.h"
#include "log-internal.h"
#include "mm-internal.h"
#include "evthread-internal.h"

#include "strlcpy-internal.h"
#include "ipv6-internal.h"

#ifdef _WIN32
#define HT_NO_CACHE_HASH_VALUES
#include "ht-internal.h"
#define open _open
#define read _read
#define close _close
#ifndef fstat
#define fstat _fstati64
#endif
#ifndef stat
#define stat _stati64
#endif
#define mode_t int
#endif

int
evutil_open_closeonexec_(const char *pathname, int flags, unsigned mode)
{
	int fd;

#ifdef O_CLOEXEC
	fd = open(pathname, flags|O_CLOEXEC, (mode_t)mode);
	if (fd >= 0 || errno == EINVAL)
		return fd;
	/* If we got an EINVAL, fall through and try without O_CLOEXEC */
#endif
	fd = open(pathname, flags, (mode_t)mode);
	if (fd < 0)
		return -1;

#if defined(FD_CLOEXEC)
	if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0) {
		close(fd);
		return -1;
	}
#endif

	return fd;
}

/**
   Read the contents of 'filename' into a newly allocated NUL-terminated
   string.  Set *content_out to hold this string, and *len_out to hold its
   length (not including the appended NUL).  If 'is_binary', open the file in
   binary mode.

   Returns 0 on success, -1 if the open fails, and -2 for all other failures.

   Used internally only; may go away in a future version.
 */
int
evutil_read_file_(const char *filename, char **content_out, size_t *len_out,
    int is_binary)
{
	int fd, r;
	struct stat st;
	char *mem;
	size_t read_so_far=0;
	int mode = O_RDONLY;

	EVUTIL_ASSERT(content_out);
	EVUTIL_ASSERT(len_out);
	*content_out = NULL;
	*len_out = 0;

#ifdef O_BINARY
	if (is_binary)
		mode |= O_BINARY;
#endif

	fd = evutil_open_closeonexec_(filename, mode, 0);
	if (fd < 0)
		return -1;
	if (fstat(fd, &st) || st.st_size < 0 ||
	    st.st_size > EV_SSIZE_MAX-1 ) {
		close(fd);
		return -2;
	}
	mem = mm_malloc((size_t)st.st_size + 1);
	if (!mem) {
		close(fd);
		return -2;
	}
	read_so_far = 0;
#ifdef _WIN32
#define N_TO_READ(x) ((x) > INT_MAX) ? INT_MAX : ((int)(x))
#else
#define N_TO_READ(x) (x)
#endif
	while ((r = read(fd, mem+read_so_far, N_TO_READ(st.st_size - read_so_far))) > 0) {
		read_so_far += r;
		if (read_so_far >= (size_t)st.st_size)
			break;
		EVUTIL_ASSERT(read_so_far < (size_t)st.st_size);
	}
	close(fd);
	if (r < 0) {
		mm_free(mem);
		return -2;
	}
	mem[read_so_far] = 0;

	*len_out = read_so_far;
	*content_out = mem;
	return 0;
}

int
evutil_socketpair(int family, int type, int protocol, evutil_socket_t fd[2])
{
#ifndef _WIN32
	return socketpair(family, type, protocol, fd);
#else
	return evutil_ersatz_socketpair_(family, type, protocol, fd);
#endif
}

int
evutil_ersatz_socketpair_(int family, int type, int protocol,
    evutil_socket_t fd[2])
{
	/* This code is originally from Tor.  Used with permission. */

	/* This socketpair does not work when localhost is down. So
	 * it's really not the same thing at all. But it's close enough
	 * for now, and really, when localhost is down sometimes, we
	 * have other problems too.
	 */
#ifdef _WIN32
#define ERR(e) WSA##e
#else
#define ERR(e) e
#endif
	evutil_socket_t listener = -1;
	evutil_socket_t connector = -1;
	evutil_socket_t acceptor = -1;
	struct sockaddr_in listen_addr;
	struct sockaddr_in connect_addr;
	ev_socklen_t size;
	int saved_errno = -1;

	if (protocol
		|| (family != AF_INET
#ifdef AF_UNIX
		    && family != AF_UNIX
#endif
		)) {
		EVUTIL_SET_SOCKET_ERROR(ERR(EAFNOSUPPORT));
		return -1;
	}
	if (!fd) {
		EVUTIL_SET_SOCKET_ERROR(ERR(EINVAL));
		return -1;
	}

	listener = socket(AF_INET, type, 0);
	if (listener < 0)
		return -1;
	memset(&listen_addr, 0, sizeof(listen_addr));
	listen_addr.sin_family = AF_INET;
	listen_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
	listen_addr.sin_port = 0;	/* kernel chooses port.	 */
	if (bind(listener, (struct sockaddr *) &listen_addr, sizeof (listen_addr))
		== -1)
		goto tidy_up_and_fail;
	if (listen(listener, 1) == -1)
		goto tidy_up_and_fail;

	connector = socket(AF_INET, type, 0);
	if (connector < 0)
		goto tidy_up_and_fail;
	/* We want to find out the port number to connect to.  */
	size = sizeof(connect_addr);
	if (getsockname(listener, (struct sockaddr *) &connect_addr, &size) == -1)
		goto tidy_up_and_fail;
	if (size != sizeof (connect_addr))
		goto abort_tidy_up_and_fail;
	if (connect(connector, (struct sockaddr *) &connect_addr,
				sizeof(connect_addr)) == -1)
		goto tidy_up_and_fail;

	size = sizeof(listen_addr);
	acceptor = accept(listener, (struct sockaddr *) &listen_addr, &size);
	if (acceptor < 0)
		goto tidy_up_and_fail;
	if (size != sizeof(listen_addr))
		goto abort_tidy_up_and_fail;
	/* Now check we are talking to ourself by matching port and host on the
	   two sockets.	 */
	if (getsockname(connector, (struct sockaddr *) &connect_addr, &size) == -1)
		goto tidy_up_and_fail;
	if (size != sizeof (connect_addr)
		|| listen_addr.sin_family != connect_addr.sin_family
		|| listen_addr.sin_addr.s_addr != connect_addr.sin_addr.s_addr
		|| listen_addr.sin_port != connect_addr.sin_port)
		goto abort_tidy_up_and_fail;
	evutil_closesocket(listener);
	fd[0] = connector;
	fd[1] = acceptor;

	return 0;

 abort_tidy_up_and_fail:
	saved_errno = ERR(ECONNABORTED);
 tidy_up_and_fail:
	if (saved_errno < 0)
		saved_errno = EVUTIL_SOCKET_ERROR();
	if (listener != -1)
		evutil_closesocket(listener);
	if (connector != -1)
		evutil_closesocket(connector);
	if (acceptor != -1)
		evutil_closesocket(acceptor);

	EVUTIL_SET_SOCKET_ERROR(saved_errno);
	return -1;
#undef ERR
}

int
evutil_make_socket_nonblocking(evutil_socket_t fd)
{
#ifdef _WIN32
	{
		u_long nonblocking = 1;
		if (ioctlsocket(fd, FIONBIO, &nonblocking) == SOCKET_ERROR) {
			event_sock_warn(fd, "fcntl(%d, F_GETFL)", (int)fd);
			return -1;
		}
	}
#else
	{
		int flags;
		if ((flags = fcntl(fd, F_GETFL, NULL)) < 0) {
			event_warn("fcntl(%d, F_GETFL)", fd);
			return -1;
		}
		if (!(flags & O_NONBLOCK)) {
			if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
				event_warn("fcntl(%d, F_SETFL)", fd);
				return -1;
			}
		}
	}
#endif
	return 0;
}

/* Faster version of evutil_make_socket_nonblocking for internal use.
 *
 * Requires that no F_SETFL flags were previously set on the fd.
 */
static int
evutil_fast_socket_nonblocking(evutil_socket_t fd)
{
#ifdef _WIN32
	return evutil_make_socket_nonblocking(fd);
#else
	if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) {
		event_warn("fcntl(%d, F_SETFL)", fd);
		return -1;
	}
	return 0;
#endif
}

int
evutil_make_listen_socket_reuseable(evutil_socket_t sock)
{
#ifndef _WIN32
	int one = 1;
	/* REUSEADDR on Unix means, "don't hang on to this address after the
	 * listener is closed."  On Windows, though, it means "don't keep other
	 * processes from binding to this address while we're using it. */
	return setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void*) &one,
	    (ev_socklen_t)sizeof(one));
#else
	return 0;
#endif
}

int
evutil_make_listen_socket_reuseable_port(evutil_socket_t sock)
{
#if defined __linux__ && defined(SO_REUSEPORT)
	int one = 1;
	/* REUSEPORT on Linux 3.9+ means, "Multiple servers (processes or
	 * threads) can bind to the same port if they each set the option. */
	return setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, (void*) &one,
	    (ev_socklen_t)sizeof(one));
#else
	return 0;
#endif
}

int
evutil_make_tcp_listen_socket_deferred(evutil_socket_t sock)
{
#if defined(EVENT__HAVE_NETINET_TCP_H) && defined(TCP_DEFER_ACCEPT)
	int one = 1;

	/* TCP_DEFER_ACCEPT tells the kernel to call defer accept() only after data
	 * has arrived and ready to read */
	return setsockopt(sock, IPPROTO_TCP, TCP_DEFER_ACCEPT, &one,
		(ev_socklen_t)sizeof(one));
#endif
	return 0;
}

int
evutil_make_socket_closeonexec(evutil_socket_t fd)
{
#if !defined(_WIN32) && defined(EVENT__HAVE_SETFD)
	int flags;
	if ((flags = fcntl(fd, F_GETFD, NULL)) < 0) {
		event_warn("fcntl(%d, F_GETFD)", fd);
		return -1;
	}
	if (!(flags & FD_CLOEXEC)) {
		if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1) {
			event_warn("fcntl(%d, F_SETFD)", fd);
			return -1;
		}
	}
#endif
	return 0;
}

/* Faster version of evutil_make_socket_closeonexec for internal use.
 *
 * Requires that no F_SETFD flags were previously set on the fd.
 */
static int
evutil_fast_socket_closeonexec(evutil_socket_t fd)
{
#if !defined(_WIN32) && defined(EVENT__HAVE_SETFD)
	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) {
		event_warn("fcntl(%d, F_SETFD)", fd);
		return -1;
	}
#endif
	return 0;
}

int
evutil_closesocket(evutil_socket_t sock)
{
#ifndef _WIN32
	return close(sock);
#else
	return closesocket(sock);
#endif
}

ev_int64_t
evutil_strtoll(const char *s, char **endptr, int base)
{
#ifdef EVENT__HAVE_STRTOLL
	return (ev_int64_t)strtoll(s, endptr, base);
#elif EVENT__SIZEOF_LONG == 8
	return (ev_int64_t)strtol(s, endptr, base);
#elif defined(_WIN32) && defined(_MSC_VER) && _MSC_VER < 1300
	/* XXXX on old versions of MS APIs, we only support base
	 * 10. */
	ev_int64_t r;
	if (base != 10)
		return 0;
	r = (ev_int64_t) _atoi64(s);
	while (isspace(*s))
		++s;
	if (*s == '-')
		++s;
	while (isdigit(*s))
		++s;
	if (endptr)
		*endptr = (char*) s;
	return r;
#elif defined(_WIN32)
	return (ev_int64_t) _strtoi64(s, endptr, base);
#elif defined(EVENT__SIZEOF_LONG_LONG) && EVENT__SIZEOF_LONG_LONG == 8
	long long r;
	int n;
	if (base != 10 && base != 16)
		return 0;
	if (base == 10) {
		n = sscanf(s, "%lld", &r);
	} else {
		unsigned long long ru=0;
		n = sscanf(s, "%llx", &ru);
		if (ru > EV_INT64_MAX)
			return 0;
		r = (long long) ru;
	}
	if (n != 1)
		return 0;
	while (EVUTIL_ISSPACE_(*s))
		++s;
	if (*s == '-')
		++s;
	if (base == 10) {
		while (EVUTIL_ISDIGIT_(*s))
			++s;
	} else {
		while (EVUTIL_ISXDIGIT_(*s))
			++s;
	}
	if (endptr)
		*endptr = (char*) s;
	return r;
#else
#error "I don't know how to parse 64-bit integers."
#endif
}

#ifdef _WIN32
int
evutil_socket_geterror(evutil_socket_t 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;
}
#endif

/* XXX we should use an enum here. */
/* 2 for connection refused, 1 for connected, 0 for not yet, -1 for error. */
int
evutil_socket_connect_(evutil_socket_t *fd_ptr, struct sockaddr *sa, int socklen)
{
	int made_fd = 0;

	if (*fd_ptr < 0) {
		if ((*fd_ptr = socket(sa->sa_family, SOCK_STREAM, 0)) < 0)
			goto err;
		made_fd = 1;
		if (evutil_make_socket_nonblocking(*fd_ptr) < 0) {
			goto err;
		}
	}

	if (connect(*fd_ptr, sa, socklen) < 0) {
		int e = evutil_socket_geterror(*fd_ptr);
		if (EVUTIL_ERR_CONNECT_RETRIABLE(e))
			return 0;
		if (EVUTIL_ERR_CONNECT_REFUSED(e))
			return 2;
		goto err;
	} else {
		return 1;
	}

err:
	if (made_fd) {
		evutil_closesocket(*fd_ptr);
		*fd_ptr = -1;
	}
	return -1;
}

/* Check whether a socket on which we called connect() is done
   connecting. Return 1 for connected, 0 for not yet, -1 for error.  In the
   error case, set the current socket errno to the error that happened during
   the connect operation. */
int
evutil_socket_finished_connecting_(evutil_socket_t fd)
{
	int e;
	ev_socklen_t elen = sizeof(e);

	if (getsockopt(fd, SOL_SOCKET, SO_ERROR, (void*)&e, &elen) < 0)
		return -1;

	if (e) {
		if (EVUTIL_ERR_CONNECT_RETRIABLE(e))
			return 0;
		EVUTIL_SET_SOCKET_ERROR(e);
		return -1;
	}

	return 1;
}

#if (EVUTIL_AI_PASSIVE|EVUTIL_AI_CANONNAME|EVUTIL_AI_NUMERICHOST| \
     EVUTIL_AI_NUMERICSERV|EVUTIL_AI_V4MAPPED|EVUTIL_AI_ALL| \
     EVUTIL_AI_ADDRCONFIG) != \
    (EVUTIL_AI_PASSIVE^EVUTIL_AI_CANONNAME^EVUTIL_AI_NUMERICHOST^ \
     EVUTIL_AI_NUMERICSERV^EVUTIL_AI_V4MAPPED^EVUTIL_AI_ALL^ \
     EVUTIL_AI_ADDRCONFIG)
#error "Some of our EVUTIL_AI_* flags seem to overlap with system AI_* flags"
#endif

/* We sometimes need to know whether we have an ipv4 address and whether we
   have an ipv6 address. If 'have_checked_interfaces', then we've already done
   the test.  If 'had_ipv4_address', then it turns out we had an ipv4 address.
   If 'had_ipv6_address', then it turns out we had an ipv6 address.   These are
   set by evutil_check_interfaces. */
static int have_checked_interfaces, had_ipv4_address, had_ipv6_address;

/* Macro: True iff the IPv4 address 'addr', in host order, is in 127.0.0.0/8
 */
#define EVUTIL_V4ADDR_IS_LOCALHOST(addr) (((addr)>>24) == 127)

/* Macro: True iff the IPv4 address 'addr', in host order, is a class D
 * (multiclass) address.
 */
#define EVUTIL_V4ADDR_IS_CLASSD(addr) ((((addr)>>24) & 0xf0) == 0xe0)

static void
evutil_found_ifaddr(const struct sockaddr *sa)
{
	const char ZEROES[] = "\x00\x00\x00\x00\x00\x00\x00\x00"
	    "\x00\x00\x00\x00\x00\x00\x00\x00";

	if (sa->sa_family == AF_INET) {
		const struct sockaddr_in *sin = (struct sockaddr_in *)sa;
		ev_uint32_t addr = ntohl(sin->sin_addr.s_addr);
		if (addr == 0 ||
		    EVUTIL_V4ADDR_IS_LOCALHOST(addr) ||
		    EVUTIL_V4ADDR_IS_CLASSD(addr)) {
			/* Not actually a usable external address. */
		} else {
			event_debug(("Detected an IPv4 interface"));
			had_ipv4_address = 1;
		}
	} else if (sa->sa_family == AF_INET6) {
		const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;
		const unsigned char *addr =
		    (unsigned char*)sin6->sin6_addr.s6_addr;
		if (!memcmp(addr, ZEROES, 8) ||
		    ((addr[0] & 0xfe) == 0xfc) ||
		    (addr[0] == 0xfe && (addr[1] & 0xc0) == 0x80) ||
		    (addr[0] == 0xfe && (addr[1] & 0xc0) == 0xc0) ||
		    (addr[0] == 0xff)) {
			/* This is a reserved, ipv4compat, ipv4map, loopback,
			 * link-local, multicast, or unspecified address. */
		} else {
			event_debug(("Detected an IPv6 interface"));
			had_ipv6_address = 1;
		}
	}
}

#ifdef _WIN32
typedef ULONG (WINAPI *GetAdaptersAddresses_fn_t)(
              ULONG, ULONG, PVOID, PIP_ADAPTER_ADDRESSES, PULONG);
#endif

static int
evutil_check_ifaddrs(void)
{
#if defined(EVENT__HAVE_GETIFADDRS)
	/* Most free Unixy systems provide getifaddrs, which gives us a linked list
	 * of struct ifaddrs. */
	struct ifaddrs *ifa = NULL;
	const struct ifaddrs *i;
	if (getifaddrs(&ifa) < 0) {
		event_warn("Unable to call getifaddrs()");
		return -1;
	}

	for (i = ifa; i; i = i->ifa_next) {
		if (!i->ifa_addr)
			continue;
		evutil_found_ifaddr(i->ifa_addr);
	}

	freeifaddrs(ifa);
	return 0;
#elif defined(_WIN32)
	/* Windows XP began to provide GetAdaptersAddresses. Windows 2000 had a
	   "GetAdaptersInfo", but that's deprecated; let's just try
	   GetAdaptersAddresses and fall back to connect+getsockname.
	*/
	HMODULE lib = evutil_load_windows_system_library_(TEXT("ihplapi.dll"));
	GetAdaptersAddresses_fn_t fn;
	ULONG size, res;
	IP_ADAPTER_ADDRESSES *addresses = NULL, *address;
	int result = -1;

#define FLAGS (GAA_FLAG_SKIP_ANYCAST | \
               GAA_FLAG_SKIP_MULTICAST | \
               GAA_FLAG_SKIP_DNS_SERVER)

	if (!lib)
		goto done;

	if (!(fn = (GetAdaptersAddresses_fn_t) GetProcAddress(lib, "GetAdaptersAddresses")))
		goto done;

	/* Guess how much space we need. */
	size = 15*1024;
	addresses = mm_malloc(size);
	if (!addresses)
		goto done;
	res = fn(AF_UNSPEC, FLAGS, NULL, addresses, &size);
	if (res == ERROR_BUFFER_OVERFLOW) {
		/* we didn't guess that we needed enough space; try again */
		mm_free(addresses);
		addresses = mm_malloc(size);
		if (!addresses)
			goto done;
		res = fn(AF_UNSPEC, FLAGS, NULL, addresses, &size);
	}
	if (res != NO_ERROR)
		goto done;

	for (address = addresses; address; address = address->Next) {
		IP_ADAPTER_UNICAST_ADDRESS *a;
		for (a = address->FirstUnicastAddress; a; a = a->Next) {
			/* Yes, it's a linked list inside a linked list */
			struct sockaddr *sa = a->Address.lpSockaddr;
			evutil_found_ifaddr(sa);
		}
	}

	result = 0;
done:
	if (lib)
		FreeLibrary(lib);
	if (addresses)
		mm_free(addresses);
	return result;
#else
	return -1;
#endif
}

/* Test whether we have an ipv4 interface and an ipv6 interface.  Return 0 if
 * the test seemed successful. */
static int
evutil_check_interfaces(int force_recheck)
{
	evutil_socket_t fd = -1;
	struct sockaddr_in sin, sin_out;
	struct sockaddr_in6 sin6, sin6_out;
	ev_socklen_t sin_out_len = sizeof(sin_out);
	ev_socklen_t sin6_out_len = sizeof(sin6_out);
	int r;
	if (have_checked_interfaces && !force_recheck)
		return 0;

	if (evutil_check_ifaddrs() == 0) {
		/* Use a nice sane interface, if this system has one. */
		return 0;
	}

	/* Ugh. There was no nice sane interface.  So to check whether we have
	 * an interface open for a given protocol, will try to make a UDP
	 * 'connection' to a remote host on the internet.  We don't actually
	 * use it, so the address doesn't matter, but we want to pick one that
	 * keep us from using a host- or link-local interface. */
	memset(&sin, 0, sizeof(sin));
	sin.sin_family = AF_INET;
	sin.sin_port = htons(53);
	r = evutil_inet_pton(AF_INET, "18.244.0.188", &sin.sin_addr);
	EVUTIL_ASSERT(r);

	memset(&sin6, 0, sizeof(sin6));
	sin6.sin6_family = AF_INET6;
	sin6.sin6_port = htons(53);
	r = evutil_inet_pton(AF_INET6, "2001:4860:b002::68", &sin6.sin6_addr);
	EVUTIL_ASSERT(r);

	memset(&sin_out, 0, sizeof(sin_out));
	memset(&sin6_out, 0, sizeof(sin6_out));

	/* XXX some errnos mean 'no address'; some mean 'not enough sockets'. */
	if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) >= 0 &&
	    connect(fd, (struct sockaddr*)&sin, sizeof(sin)) == 0 &&
	    getsockname(fd, (struct sockaddr*)&sin_out, &sin_out_len) == 0) {
		/* We might have an IPv4 interface. */
		evutil_found_ifaddr((struct sockaddr*) &sin_out);
	}
	if (fd >= 0)
		evutil_closesocket(fd);

	if ((fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP)) >= 0 &&
	    connect(fd, (struct sockaddr*)&sin6, sizeof(sin6)) == 0 &&
	    getsockname(fd, (struct sockaddr*)&sin6_out, &sin6_out_len) == 0) {
		/* We might have an IPv6 interface. */
		evutil_found_ifaddr((struct sockaddr*) &sin6_out);
	}

	if (fd >= 0)
		evutil_closesocket(fd);

	return 0;
}

/* Internal addrinfo flag.  This one is set when we allocate the addrinfo from
 * inside libevent.  Otherwise, the built-in getaddrinfo() function allocated
 * it, and we should trust what they said.
 **/
#define EVUTIL_AI_LIBEVENT_ALLOCATED 0x80000000

/* Helper: construct a new addrinfo containing the socket address in
 * 'sa', which must be a sockaddr_in or a sockaddr_in6.  Take the
 * socktype and protocol info from hints.  If they weren't set, then
 * allocate both a TCP and a UDP addrinfo.
 */
struct evutil_addrinfo *
evutil_new_addrinfo_(struct sockaddr *sa, ev_socklen_t socklen,
    const struct evutil_addrinfo *hints)
{
	struct evutil_addrinfo *res;
	EVUTIL_ASSERT(hints);

	if (hints->ai_socktype == 0 && hints->ai_protocol == 0) {
		/* Indecisive user! Give them a UDP and a TCP. */
		struct evutil_addrinfo *r1, *r2;
		struct evutil_addrinfo tmp;
		memcpy(&tmp, hints, sizeof(tmp));
		tmp.ai_socktype = SOCK_STREAM; tmp.ai_protocol = IPPROTO_TCP;
		r1 = evutil_new_addrinfo_(sa, socklen, &tmp);
		if (!r1)
			return NULL;
		tmp.ai_socktype = SOCK_DGRAM; tmp.ai_protocol = IPPROTO_UDP;
		r2 = evutil_new_addrinfo_(sa, socklen, &tmp);
		if (!r2) {
			evutil_freeaddrinfo(r1);
			return NULL;
		}
		r1->ai_next = r2;
		return r1;
	}

	/* We're going to allocate extra space to hold the sockaddr. */
	res = mm_calloc(1,sizeof(struct evutil_addrinfo)+socklen);
	if (!res)
		return NULL;
	res->ai_addr = (struct sockaddr*)
	    (((char*)res) + sizeof(struct evutil_addrinfo));
	memcpy(res->ai_addr, sa, socklen);
	res->ai_addrlen = socklen;
	res->ai_family = sa->sa_family; /* Same or not? XXX */
	res->ai_flags = EVUTIL_AI_LIBEVENT_ALLOCATED;
	res->ai_socktype = hints->ai_socktype;
	res->ai_protocol = hints->ai_protocol;

	return res;
}

/* Append the addrinfo 'append' to the end of 'first', and return the start of
 * the list.  Either element can be NULL, in which case we return the element
 * that is not NULL. */
struct evutil_addrinfo *
evutil_addrinfo_append_(struct evutil_addrinfo *first,
    struct evutil_addrinfo *append)
{
	struct evutil_addrinfo *ai = first;
	if (!ai)
		return append;
	while (ai->ai_next)
		ai = ai->ai_next;
	ai->ai_next = append;

	return first;
}

static int
parse_numeric_servname(const char *servname)
{
	int n;
	char *endptr=NULL;
	n = (int) strtol(servname, &endptr, 10);
	if (n>=0 && n <= 65535 && servname[0] && endptr && !endptr[0])
		return n;
	else
		return -1;
}

/** Parse a service name in 'servname', which can be a decimal port.
 * Return the port number, or -1 on error.
 */
static int
evutil_parse_servname(const char *servname, const char *protocol,
    const struct evutil_addrinfo *hints)
{
	int n = parse_numeric_servname(servname);
	if (n>=0)
		return n;
#if defined(EVENT__HAVE_GETSERVBYNAME) || defined(_WIN32)
	if (!(hints->ai_flags & EVUTIL_AI_NUMERICSERV)) {
		struct servent *ent = getservbyname(servname, protocol);
		if (ent) {
			return ntohs(ent->s_port);
		}
	}
#endif
	return -1;
}

/* Return a string corresponding to a protocol number that we can pass to
 * getservyname.  */
static const char *
evutil_unparse_protoname(int proto)
{
	switch (proto) {
	case 0:
		return NULL;
	case IPPROTO_TCP:
		return "tcp";
	case IPPROTO_UDP:
		return "udp";
#ifdef IPPROTO_SCTP
	case IPPROTO_SCTP:
		return "sctp";
#endif
	default:
#ifdef EVENT__HAVE_GETPROTOBYNUMBER
		{
			struct protoent *ent = getprotobynumber(proto);
			if (ent)
				return ent->p_name;
		}
#endif
		return NULL;
	}
}

static void
evutil_getaddrinfo_infer_protocols(struct evutil_addrinfo *hints)
{
	/* If we can guess the protocol from the socktype, do so. */
	if (!hints->ai_protocol && hints->ai_socktype) {
		if (hints->ai_socktype == SOCK_DGRAM)
			hints->ai_protocol = IPPROTO_UDP;
		else if (hints->ai_socktype == SOCK_STREAM)
			hints->ai_protocol = IPPROTO_TCP;
	}

	/* Set the socktype if it isn't set. */
	if (!hints->ai_socktype && hints->ai_protocol) {
		if (hints->ai_protocol == IPPROTO_UDP)
			hints->ai_socktype = SOCK_DGRAM;
		else if (hints->ai_protocol == IPPROTO_TCP)
			hints->ai_socktype = SOCK_STREAM;
#ifdef IPPROTO_SCTP
		else if (hints->ai_protocol == IPPROTO_SCTP)
			hints->ai_socktype = SOCK_STREAM;
#endif
	}
}

#if AF_UNSPEC != PF_UNSPEC
#error "I cannot build on a system where AF_UNSPEC != PF_UNSPEC"
#endif

/** Implements the part of looking up hosts by name that's common to both
 * the blocking and nonblocking resolver:
 *   - Adjust 'hints' to have a reasonable socktype and protocol.
 *   - Look up the port based on 'servname', and store it in *portnum,
 *   - Handle the nodename==NULL case
 *   - Handle some invalid arguments cases.
 *   - Handle the cases where nodename is an IPv4 or IPv6 address.
 *
 * If we need the resolver to look up the hostname, we return
 * EVUTIL_EAI_NEED_RESOLVE.  Otherwise, we can completely implement
 * getaddrinfo: we return 0 or an appropriate EVUTIL_EAI_* error, and
 * set *res as getaddrinfo would.
 */
int
evutil_getaddrinfo_common_(const char *nodename, const char *servname,
    struct evutil_addrinfo *hints, struct evutil_addrinfo **res, int *portnum)
{
	int port = 0;
	const char *pname;

	if (nodename == NULL && servname == NULL)
		return EVUTIL_EAI_NONAME;

	/* We only understand 3 families */
	if (hints->ai_family != PF_UNSPEC && hints->ai_family != PF_INET &&
	    hints->ai_family != PF_INET6)
		return EVUTIL_EAI_FAMILY;

	evutil_getaddrinfo_infer_protocols(hints);

	/* Look up the port number and protocol, if possible. */
	pname = evutil_unparse_protoname(hints->ai_protocol);
	if (servname) {
		/* XXXX We could look at the protocol we got back from
		 * getservbyname, but it doesn't seem too useful. */
		port = evutil_parse_servname(servname, pname, hints);
		if (port < 0) {
			return EVUTIL_EAI_NONAME;
		}
	}

	/* If we have no node name, then we're supposed to bind to 'any' and
	 * connect to localhost. */
	if (nodename == NULL) {
		struct evutil_addrinfo *res4=NULL, *res6=NULL;
		if (hints->ai_family != PF_INET) { /* INET6 or UNSPEC. */
			struct sockaddr_in6 sin6;
			memset(&sin6, 0, sizeof(sin6));
			sin6.sin6_family = AF_INET6;
			sin6.sin6_port = htons(port);
			if (hints->ai_flags & EVUTIL_AI_PASSIVE) {
				/* Bind to :: */
			} else {
				/* connect to ::1 */
				sin6.sin6_addr.s6_addr[15] = 1;
			}
			res6 = evutil_new_addrinfo_((struct sockaddr*)&sin6,
			    sizeof(sin6), hints);
			if (!res6)
				return EVUTIL_EAI_MEMORY;
		}

		if (hints->ai_family != PF_INET6) { /* INET or UNSPEC */
			struct sockaddr_in sin;
			memset(&sin, 0, sizeof(sin));
			sin.sin_family = AF_INET;
			sin.sin_port = htons(port);
			if (hints->ai_flags & EVUTIL_AI_PASSIVE) {
				/* Bind to 0.0.0.0 */
			} else {
				/* connect to 127.0.0.1 */
				sin.sin_addr.s_addr = htonl(0x7f000001);
			}
			res4 = evutil_new_addrinfo_((struct sockaddr*)&sin,
			    sizeof(sin), hints);
			if (!res4) {
				if (res6)
					evutil_freeaddrinfo(res6);
				return EVUTIL_EAI_MEMORY;
			}
		}
		*res = evutil_addrinfo_append_(res4, res6);
		return 0;
	}

	/* If we can, we should try to parse the hostname without resolving
	 * it. */
	/* Try ipv6. */
	if (hints->ai_family == PF_INET6 || hints->ai_family == PF_UNSPEC) {
		struct sockaddr_in6 sin6;
		memset(&sin6, 0, sizeof(sin6));
		if (1==evutil_inet_pton(AF_INET6, nodename, &sin6.sin6_addr)) {
			/* Got an ipv6 address. */
			sin6.sin6_family = AF_INET6;
			sin6.sin6_port = htons(port);
			*res = evutil_new_addrinfo_((struct sockaddr*)&sin6,
			    sizeof(sin6), hints);
			if (!*res)
				return EVUTIL_EAI_MEMORY;
			return 0;
		}
	}

	/* Try ipv4. */
	if (hints->ai_family == PF_INET || hints->ai_family == PF_UNSPEC) {
		struct sockaddr_in sin;
		memset(&sin, 0, sizeof(sin));
		if (1==evutil_inet_pton(AF_INET, nodename, &sin.sin_addr)) {
			/* Got an ipv6 address. */
			sin.sin_family = AF_INET;
			sin.sin_port = htons(port);
			*res = evutil_new_addrinfo_((struct sockaddr*)&sin,
			    sizeof(sin), hints);
			if (!*res)
				return EVUTIL_EAI_MEMORY;
			return 0;
		}
	}


	/* If we have reached this point, we definitely need to do a DNS
	 * lookup. */
	if ((hints->ai_flags & EVUTIL_AI_NUMERICHOST)) {
		/* If we're not allowed to do one, then say so. */
		return EVUTIL_EAI_NONAME;
	}
	*portnum = port;
	return EVUTIL_EAI_NEED_RESOLVE;
}

#ifdef EVENT__HAVE_GETADDRINFO
#define USE_NATIVE_GETADDRINFO
#endif

#ifdef USE_NATIVE_GETADDRINFO
/* A mask of all the flags that we declare, so we can clear them before calling
 * the native getaddrinfo */
static const unsigned int ALL_NONNATIVE_AI_FLAGS =
#ifndef AI_PASSIVE
    EVUTIL_AI_PASSIVE |
#endif
#ifndef AI_CANONNAME
    EVUTIL_AI_CANONNAME |
#endif
#ifndef AI_NUMERICHOST
    EVUTIL_AI_NUMERICHOST |
#endif
#ifndef AI_NUMERICSERV
    EVUTIL_AI_NUMERICSERV |
#endif
#ifndef AI_ADDRCONFIG
    EVUTIL_AI_ADDRCONFIG |
#endif
#ifndef AI_ALL
    EVUTIL_AI_ALL |
#endif
#ifndef AI_V4MAPPED
    EVUTIL_AI_V4MAPPED |
#endif
    EVUTIL_AI_LIBEVENT_ALLOCATED;

static const unsigned int ALL_NATIVE_AI_FLAGS =
#ifdef AI_PASSIVE
    AI_PASSIVE |
#endif
#ifdef AI_CANONNAME
    AI_CANONNAME |
#endif
#ifdef AI_NUMERICHOST
    AI_NUMERICHOST |
#endif
#ifdef AI_NUMERICSERV
    AI_NUMERICSERV |
#endif
#ifdef AI_ADDRCONFIG
    AI_ADDRCONFIG |
#endif
#ifdef AI_ALL
    AI_ALL |
#endif
#ifdef AI_V4MAPPED
    AI_V4MAPPED |
#endif
    0;
#endif

#ifndef USE_NATIVE_GETADDRINFO
/* Helper for systems with no getaddrinfo(): make one or more addrinfos out of
 * a struct hostent.
 */
static struct evutil_addrinfo *
addrinfo_from_hostent(const struct hostent *ent,
    int port, const struct evutil_addrinfo *hints)
{
	int i;
	struct sockaddr_in sin;
	struct sockaddr_in6 sin6;
	struct sockaddr *sa;
	int socklen;
	struct evutil_addrinfo *res=NULL, *ai;
	void *addrp;

	if (ent->h_addrtype == PF_INET) {
		memset(&sin, 0, sizeof(sin));
		sin.sin_family = AF_INET;
		sin.sin_port = htons(port);
		sa = (struct sockaddr *)&sin;
		socklen = sizeof(struct sockaddr_in);
		addrp = &sin.sin_addr;
		if (ent->h_length != sizeof(sin.sin_addr)) {
			event_warnx("Weird h_length from gethostbyname");
			return NULL;
		}
	} else if (ent->h_addrtype == PF_INET6) {
		memset(&sin6, 0, sizeof(sin6));
		sin6.sin6_family = AF_INET6;
		sin6.sin6_port = htons(port);
		sa = (struct sockaddr *)&sin6;
		socklen = sizeof(struct sockaddr_in);
		addrp = &sin6.sin6_addr;
		if (ent->h_length != sizeof(sin6.sin6_addr)) {
			event_warnx("Weird h_length from gethostbyname");
			return NULL;
		}
	} else
		return NULL;

	for (i = 0; ent->h_addr_list[i]; ++i) {
		memcpy(addrp, ent->h_addr_list[i], ent->h_length);
		ai = evutil_new_addrinfo_(sa, socklen, hints);
		if (!ai) {
			evutil_freeaddrinfo(res);
			return NULL;
		}
		res = evutil_addrinfo_append_(res, ai);
	}

	if (res && ((hints->ai_flags & EVUTIL_AI_CANONNAME) && ent->h_name)) {
		res->ai_canonname = mm_strdup(ent->h_name);
		if (res->ai_canonname == NULL) {
			evutil_freeaddrinfo(res);
			return NULL;
		}
	}

	return res;
}
#endif

/* If the EVUTIL_AI_ADDRCONFIG flag is set on hints->ai_flags, and
 * hints->ai_family is PF_UNSPEC, then revise the value of hints->ai_family so
 * that we'll only get addresses we could maybe connect to.
 */
void
evutil_adjust_hints_for_addrconfig_(struct evutil_addrinfo *hints)
{
	if (!(hints->ai_flags & EVUTIL_AI_ADDRCONFIG))
		return;
	if (hints->ai_family != PF_UNSPEC)
		return;
	if (!have_checked_interfaces)
		evutil_check_interfaces(0);
	if (had_ipv4_address && !had_ipv6_address) {
		hints->ai_family = PF_INET;
	} else if (!had_ipv4_address && had_ipv6_address) {
		hints->ai_family = PF_INET6;
	}
}

#ifdef USE_NATIVE_GETADDRINFO
static int need_numeric_port_hack_=0;
static int need_socktype_protocol_hack_=0;
static int tested_for_getaddrinfo_hacks=0;

/* Some older BSDs (like OpenBSD up to 4.6) used to believe that
   giving a numeric port without giving an ai_socktype was verboten.
   We test for this so we can apply an appropriate workaround.  If it
   turns out that the bug is present, then:

    - If nodename==NULL and servname is numeric, we build an answer
      ourselves using evutil_getaddrinfo_common_().

    - If nodename!=NULL and servname is numeric, then we set
      servname=NULL when calling getaddrinfo, and post-process the
      result to set the ports on it.

   We test for this bug at runtime, since otherwise we can't have the
   same binary run on multiple BSD versions.

   - Some versions of Solaris believe that it's nice to leave to protocol
     field set to 0.  We test for this so we can apply an appropriate
     workaround.
*/
static void
test_for_getaddrinfo_hacks(void)
{
	int r, r2;
	struct evutil_addrinfo *ai=NULL, *ai2=NULL;
	struct evutil_addrinfo hints;

	memset(&hints,0,sizeof(hints));
	hints.ai_family = PF_UNSPEC;
	hints.ai_flags =
#ifdef AI_NUMERICHOST
	    AI_NUMERICHOST |
#endif
#ifdef AI_NUMERICSERV
	    AI_NUMERICSERV |
#endif
	    0;
	r = getaddrinfo("1.2.3.4", "80", &hints, &ai);
	hints.ai_socktype = SOCK_STREAM;
	r2 = getaddrinfo("1.2.3.4", "80", &hints, &ai2);
	if (r2 == 0 && r != 0) {
		need_numeric_port_hack_=1;
	}
	if (ai2 && ai2->ai_protocol == 0) {
		need_socktype_protocol_hack_=1;
	}

	if (ai)
		freeaddrinfo(ai);
	if (ai2)
		freeaddrinfo(ai2);
	tested_for_getaddrinfo_hacks=1;
}

static inline int
need_numeric_port_hack(void)
{
	if (!tested_for_getaddrinfo_hacks)
		test_for_getaddrinfo_hacks();
	return need_numeric_port_hack_;
}

static inline int
need_socktype_protocol_hack(void)
{
	if (!tested_for_getaddrinfo_hacks)
		test_for_getaddrinfo_hacks();
	return need_socktype_protocol_hack_;
}

static void
apply_numeric_port_hack(int port, struct evutil_addrinfo **ai)
{
	/* Now we run through the list and set the ports on all of the
	 * results where ports would make sense. */
	for ( ; *ai; ai = &(*ai)->ai_next) {
		struct sockaddr *sa = (*ai)->ai_addr;
		if (sa && sa->sa_family == AF_INET) {
			struct sockaddr_in *sin = (struct sockaddr_in*)sa;
			sin->sin_port = htons(port);
		} else if (sa && sa->sa_family == AF_INET6) {
			struct sockaddr_in6 *sin6 = (struct sockaddr_in6*)sa;
			sin6->sin6_port = htons(port);
		} else {
			/* A numeric port makes no sense here; remove this one
			 * from the list. */
			struct evutil_addrinfo *victim = *ai;
			*ai = victim->ai_next;
			victim->ai_next = NULL;
			freeaddrinfo(victim);
		}
	}
}

static int
apply_socktype_protocol_hack(struct evutil_addrinfo *ai)
{
	struct evutil_addrinfo *ai_new;
	for (; ai; ai = ai->ai_next) {
		evutil_getaddrinfo_infer_protocols(ai);
		if (ai->ai_socktype || ai->ai_protocol)
			continue;
		ai_new = mm_malloc(sizeof(*ai_new));
		if (!ai_new)
			return -1;
		memcpy(ai_new, ai, sizeof(*ai_new));
		ai->ai_socktype = SOCK_STREAM;
		ai->ai_protocol = IPPROTO_TCP;
		ai_new->ai_socktype = SOCK_DGRAM;
		ai_new->ai_protocol = IPPROTO_UDP;

		ai_new->ai_next = ai->ai_next;
		ai->ai_next = ai_new;
	}
	return 0;
}
#endif

int
evutil_getaddrinfo(const char *nodename, const char *servname,
    const struct evutil_addrinfo *hints_in, struct evutil_addrinfo **res)
{
#ifdef USE_NATIVE_GETADDRINFO
	struct evutil_addrinfo hints;
	int portnum=-1, need_np_hack, err;

	if (hints_in) {
		memcpy(&hints, hints_in, sizeof(hints));
	} else {
		memset(&hints, 0, sizeof(hints));
		hints.ai_family = PF_UNSPEC;
	}

#ifndef AI_ADDRCONFIG
	/* Not every system has AI_ADDRCONFIG, so fake it. */
	if (hints.ai_family == PF_UNSPEC &&
	    (hints.ai_flags & EVUTIL_AI_ADDRCONFIG)) {
		evutil_adjust_hints_for_addrconfig_(&hints);
	}
#endif

#ifndef AI_NUMERICSERV
	/* Not every system has AI_NUMERICSERV, so fake it. */
	if (hints.ai_flags & EVUTIL_AI_NUMERICSERV) {
		if (servname && parse_numeric_servname(servname)<0)
			return EVUTIL_EAI_NONAME;
	}
#endif

	/* Enough operating systems handle enough common non-resolve
	 * cases here weirdly enough that we are better off just
	 * overriding them.  For example:
	 *
	 * - Windows doesn't like to infer the protocol from the
	 *   socket type, or fill in socket or protocol types much at
	 *   all.  It also seems to do its own broken implicit
	 *   always-on version of AI_ADDRCONFIG that keeps it from
	 *   ever resolving even a literal IPv6 address when
	 *   ai_addrtype is PF_UNSPEC.
	 */
#ifdef _WIN32
	{
		int tmp_port;
		err = evutil_getaddrinfo_common_(nodename,servname,&hints,
		    res, &tmp_port);
		if (err == 0 ||
		    err == EVUTIL_EAI_MEMORY ||
		    err == EVUTIL_EAI_NONAME)
			return err;
		/* If we make it here, the system getaddrinfo can
		 * have a crack at it. */
	}
#endif

	/* See documentation for need_numeric_port_hack above.*/
	need_np_hack = need_numeric_port_hack() && servname && !hints.ai_socktype
	    && ((portnum=parse_numeric_servname(servname)) >= 0);
	if (need_np_hack) {
		if (!nodename)
			return evutil_getaddrinfo_common_(
				NULL,servname,&hints, res, &portnum);
		servname = NULL;
	}

	if (need_socktype_protocol_hack()) {
		evutil_getaddrinfo_infer_protocols(&hints);
	}

	/* Make sure that we didn't actually steal any AI_FLAGS values that
	 * the system is using.  (This is a constant expression, and should ge
	 * optimized out.)
	 *
	 * XXXX Turn this into a compile-time failure rather than a run-time
	 * failure.
	 */
	EVUTIL_ASSERT((ALL_NONNATIVE_AI_FLAGS & ALL_NATIVE_AI_FLAGS) == 0);

	/* Clear any flags that only libevent understands. */
	hints.ai_flags &= ~ALL_NONNATIVE_AI_FLAGS;

	err = getaddrinfo(nodename, servname, &hints, res);
	if (need_np_hack)
		apply_numeric_port_hack(portnum, res);

	if (need_socktype_protocol_hack()) {
		if (apply_socktype_protocol_hack(*res) < 0) {
			evutil_freeaddrinfo(*res);
			*res = NULL;
			return EVUTIL_EAI_MEMORY;
		}
	}
	return err;
#else
	int port=0, err;
	struct hostent *ent = NULL;
	struct evutil_addrinfo hints;

	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);

	err = evutil_getaddrinfo_common_(nodename, servname, &hints, res, &port);
	if (err != EVUTIL_EAI_NEED_RESOLVE) {
		/* We either succeeded or failed.  No need to continue */
		return err;
	}

	err = 0;
	/* Use any of the various gethostbyname_r variants as available. */
	{
#ifdef EVENT__HAVE_GETHOSTBYNAME_R_6_ARG
		/* This one is what glibc provides. */
		char buf[2048];
		struct hostent hostent;
		int r;
		r = gethostbyname_r(nodename, &hostent, buf, sizeof(buf), &ent,
		    &err);
#elif defined(EVENT__HAVE_GETHOSTBYNAME_R_5_ARG)
		char buf[2048];
		struct hostent hostent;
		ent = gethostbyname_r(nodename, &hostent, buf, sizeof(buf),
		    &err);
#elif defined(EVENT__HAVE_GETHOSTBYNAME_R_3_ARG)
		struct hostent_data data;
		struct hostent hostent;
		memset(&data, 0, sizeof(data));
		err = gethostbyname_r(nodename, &hostent, &data);
		ent = err ? NULL : &hostent;
#else
		/* fall back to gethostbyname. */
		/* XXXX This needs a lock everywhere but Windows. */
		ent = gethostbyname(nodename);
#ifdef _WIN32
		err = WSAGetLastError();
#else
		err = h_errno;
#endif
#endif

		/* Now we have either ent or err set. */
		if (!ent) {
			/* XXX is this right for windows ? */
			switch (err) {
			case TRY_AGAIN:
				return EVUTIL_EAI_AGAIN;
			case NO_RECOVERY:
			default:
				return EVUTIL_EAI_FAIL;
			case HOST_NOT_FOUND:
				return EVUTIL_EAI_NONAME;
			case NO_ADDRESS:
#if NO_DATA != NO_ADDRESS
			case NO_DATA:
#endif
				return EVUTIL_EAI_NODATA;
			}
		}

		if (ent->h_addrtype != hints.ai_family &&
		    hints.ai_family != PF_UNSPEC) {
			/* This wasn't the type we were hoping for.  Too bad
			 * we never had a chance to ask gethostbyname for what
			 * we wanted. */
			return EVUTIL_EAI_NONAME;
		}

		/* Make sure we got _some_ answers. */
		if (ent->h_length == 0)
			return EVUTIL_EAI_NODATA;

		/* If we got an address type we don't know how to make a
		   sockaddr for, give up. */
		if (ent->h_addrtype != PF_INET && ent->h_addrtype != PF_INET6)
			return EVUTIL_EAI_FAMILY;

		*res = addrinfo_from_hostent(ent, port, &hints);
		if (! *res)
			return EVUTIL_EAI_MEMORY;
	}

	return 0;
#endif
}

void
evutil_freeaddrinfo(struct evutil_addrinfo *ai)
{
#ifdef EVENT__HAVE_GETADDRINFO
	if (!(ai->ai_flags & EVUTIL_AI_LIBEVENT_ALLOCATED)) {
		freeaddrinfo(ai);
		return;
	}
#endif
	while (ai) {
		struct evutil_addrinfo *next = ai->ai_next;
		if (ai->ai_canonname)
			mm_free(ai->ai_canonname);
		mm_free(ai);
		ai = next;
	}
}

static evdns_getaddrinfo_fn evdns_getaddrinfo_impl = NULL;

void
evutil_set_evdns_getaddrinfo_fn_(evdns_getaddrinfo_fn fn)
{
	if (!evdns_getaddrinfo_impl)
		evdns_getaddrinfo_impl = fn;
}

/* Internal helper function: act like evdns_getaddrinfo if dns_base is set;
 * otherwise do a blocking resolve and pass the result to the callback in the
 * way that evdns_getaddrinfo would.
 */
int
evutil_getaddrinfo_async_(struct evdns_base *dns_base,
    const char *nodename, const char *servname,
    const struct evutil_addrinfo *hints_in,
    void (*cb)(int, struct evutil_addrinfo *, void *), void *arg)
{
	if (dns_base && evdns_getaddrinfo_impl) {
		evdns_getaddrinfo_impl(
			dns_base, nodename, servname, hints_in, cb, arg);
	} else {
		struct evutil_addrinfo *ai=NULL;
		int err;
		err = evutil_getaddrinfo(nodename, servname, hints_in, &ai);
		cb(err, ai, arg);
	}
	return 0;
}

const char *
evutil_gai_strerror(int err)
{
	/* As a sneaky side-benefit, this case statement will get most
	 * compilers to tell us if any of the error codes we defined
	 * conflict with the platform's native error codes. */
	switch (err) {
	case EVUTIL_EAI_CANCEL:
		return "Request canceled";
	case 0:
		return "No error";

	case EVUTIL_EAI_ADDRFAMILY:
		return "address family for nodename not supported";
	case EVUTIL_EAI_AGAIN:
		return "temporary failure in name resolution";
	case EVUTIL_EAI_BADFLAGS:
		return "invalid value for ai_flags";
	case EVUTIL_EAI_FAIL:
		return "non-recoverable failure in name resolution";
	case EVUTIL_EAI_FAMILY:
		return "ai_family not supported";
	case EVUTIL_EAI_MEMORY:
		return "memory allocation failure";
	case EVUTIL_EAI_NODATA:
		return "no address associated with nodename";
	case EVUTIL_EAI_NONAME:
		return "nodename nor servname provided, or not known";
	case EVUTIL_EAI_SERVICE:
		return "servname not supported for ai_socktype";
	case EVUTIL_EAI_SOCKTYPE:
		return "ai_socktype not supported";
	case EVUTIL_EAI_SYSTEM:
		return "system error";
	default:
#if defined(USE_NATIVE_GETADDRINFO) && defined(_WIN32)
		return gai_strerrorA(err);
#elif defined(USE_NATIVE_GETADDRINFO)
		return gai_strerror(err);
#else
		return "Unknown error code";
#endif
	}
}

#ifdef _WIN32
/* destructively remove a trailing line terminator from s */
static void
chomp (char *s)
{
	size_t len;
	if (s && (len = strlen (s)) > 0 && s[len - 1] == '\n') {
		s[--len] = 0;
		if (len > 0 && s[len - 1] == '\r')
			s[--len] = 0;
	}
}

/* FormatMessage returns allocated strings, but evutil_socket_error_to_string
 * is supposed to return a string which is good indefinitely without having
 * to be freed.  To make this work without leaking memory, we cache the
 * string the first time FormatMessage is called on a particular error
 * code, and then return the cached string on subsequent calls with the
 * same code.  The strings aren't freed until libevent_global_shutdown
 * (or never).  We use a linked list to cache the errors, because we
 * only expect there to be a few dozen, and that should be fast enough.
 */

struct cached_sock_errs_entry {
	HT_ENTRY(cached_sock_errs_entry) node;
	DWORD code;
	char *msg; /* allocated with LocalAlloc; free with LocalFree */
};

static inline unsigned
hash_cached_sock_errs(const struct cached_sock_errs_entry *e)
{
	/* Use Murmur3's 32-bit finalizer as an integer hash function */
	DWORD h = e->code;
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;
	return h;
}

static inline int
eq_cached_sock_errs(const struct cached_sock_errs_entry *a,
		    const struct cached_sock_errs_entry *b)
{
	return a->code == b->code;
}

#ifndef EVENT__DISABLE_THREAD_SUPPORT
static void *windows_socket_errors_lock_ = NULL;
#endif

static HT_HEAD(cached_sock_errs_map, cached_sock_errs_entry)
     windows_socket_errors = HT_INITIALIZER();

HT_PROTOTYPE(cached_sock_errs_map,
	     cached_sock_errs_entry,
	     node,
	     hash_cached_sock_errs,
	     eq_cached_sock_errs);

HT_GENERATE(cached_sock_errs_map,
	    cached_sock_errs_entry,
	    node,
	    hash_cached_sock_errs,
	    eq_cached_sock_errs,
	    0.5,
	    mm_malloc,
	    mm_realloc,
	    mm_free);

/** Equivalent to strerror, but for windows socket errors. */
const char *
evutil_socket_error_to_string(int errcode)
{
	struct cached_sock_errs_entry *errs, *newerr, find;
	char *msg = NULL;

	EVLOCK_LOCK(windows_socket_errors_lock_, 0);

	find.code = errcode;
	errs = HT_FIND(cached_sock_errs_map, &windows_socket_errors, &find);
	if (errs) {
		msg = errs->msg;
		goto done;
	}

	if (0 != FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM |
			       FORMAT_MESSAGE_IGNORE_INSERTS |
			       FORMAT_MESSAGE_ALLOCATE_BUFFER,
			       NULL, errcode, 0, (LPTSTR)&msg, 0, NULL))
		chomp (msg);	/* because message has trailing newline */
	else {
		size_t len = 50;
		/* use LocalAlloc because FormatMessage does */
		msg = LocalAlloc(LMEM_FIXED, len);
		if (!msg) {
			msg = (char *)"LocalAlloc failed during Winsock error";
			goto done;
		}
		evutil_snprintf(msg, len, "winsock error 0x%08x", errcode);
	}

	newerr = (struct cached_sock_errs_entry *)
		mm_malloc(sizeof (struct cached_sock_errs_entry));

	if (!newerr) {
		LocalFree(msg);
		msg = (char *)"malloc failed during Winsock error";
		goto done;
	}

	newerr->code = errcode;
	newerr->msg = msg;
	HT_INSERT(cached_sock_errs_map, &windows_socket_errors, newerr);

 done:
	EVLOCK_UNLOCK(windows_socket_errors_lock_, 0);

	return msg;
}

#ifndef EVENT__DISABLE_THREAD_SUPPORT
int
evutil_global_setup_locks_(const int enable_locks)
{
	EVTHREAD_SETUP_GLOBAL_LOCK(windows_socket_errors_lock_, 0);
	return 0;
}
#endif

static void
evutil_free_sock_err_globals(void)
{
	struct cached_sock_errs_entry **errs, *tofree;

	for (errs = HT_START(cached_sock_errs_map, &windows_socket_errors)
		     ; errs; ) {
		tofree = *errs;
		errs = HT_NEXT_RMV(cached_sock_errs_map,
				   &windows_socket_errors,
				   errs);
		LocalFree(tofree->msg);
		mm_free(tofree);
	}

	HT_CLEAR(cached_sock_errs_map, &windows_socket_errors);

#ifndef EVENT__DISABLE_THREAD_SUPPORT
	if (windows_socket_errors_lock_ != NULL) {
		EVTHREAD_FREE_LOCK(windows_socket_errors_lock_, 0);
		windows_socket_errors_lock_ = NULL;
	}
#endif
}

#else

#ifndef EVENT__DISABLE_THREAD_SUPPORT
int
evutil_global_setup_locks_(const int enable_locks)
{
	return 0;
}
#endif

static void
evutil_free_sock_err_globals(void)
{
}

#endif

int
evutil_snprintf(char *buf, size_t buflen, const char *format, ...)
{
	int r;
	va_list ap;
	va_start(ap, format);
	r = evutil_vsnprintf(buf, buflen, format, ap);
	va_end(ap);
	return r;
}

int
evutil_vsnprintf(char *buf, size_t buflen, const char *format, va_list ap)
{
	int r;
	if (!buflen)
		return 0;
#if defined(_MSC_VER) || defined(_WIN32)
	r = _vsnprintf(buf, buflen, format, ap);
	if (r < 0)
		r = _vscprintf(format, ap);
#elif defined(sgi)
	/* Make sure we always use the correct vsnprintf on IRIX */
	extern int      _xpg5_vsnprintf(char * __restrict,
		__SGI_LIBC_NAMESPACE_QUALIFIER size_t,
		const char * __restrict, /* va_list */ char *);

	r = _xpg5_vsnprintf(buf, buflen, format, ap);
#else
	r = vsnprintf(buf, buflen, format, ap);
#endif
	buf[buflen-1] = '\0';
	return r;
}

#define USE_INTERNAL_NTOP
#define USE_INTERNAL_PTON

const char *
evutil_inet_ntop(int af, const void *src, char *dst, size_t len)
{
#if defined(EVENT__HAVE_INET_NTOP) && !defined(USE_INTERNAL_NTOP)
	return inet_ntop(af, src, dst, len);
#else
	if (af == AF_INET) {
		const struct in_addr *in = src;
		const ev_uint32_t a = ntohl(in->s_addr);
		int r;
		r = evutil_snprintf(dst, len, "%d.%d.%d.%d",
		    (int)(ev_uint8_t)((a>>24)&0xff),
		    (int)(ev_uint8_t)((a>>16)&0xff),
		    (int)(ev_uint8_t)((a>>8 )&0xff),
		    (int)(ev_uint8_t)((a    )&0xff));
		if (r<0||(size_t)r>=len)
			return NULL;
		else
			return dst;
#ifdef AF_INET6
	} else if (af == AF_INET6) {
		const struct in6_addr *addr = src;
		char buf[64], *cp;
		int longestGapLen = 0, longestGapPos = -1, i,
			curGapPos = -1, curGapLen = 0;
		ev_uint16_t words[8];
		for (i = 0; i < 8; ++i) {
			words[i] =
			    (((ev_uint16_t)addr->s6_addr[2*i])<<8) + addr->s6_addr[2*i+1];
		}
		if (words[0] == 0 && words[1] == 0 && words[2] == 0 && words[3] == 0 &&
		    words[4] == 0 && ((words[5] == 0 && words[6] && words[7]) ||
			(words[5] == 0xffff))) {
			/* This is an IPv4 address. */
			if (words[5] == 0) {
				evutil_snprintf(buf, sizeof(buf), "::%d.%d.%d.%d",
				    addr->s6_addr[12], addr->s6_addr[13],
				    addr->s6_addr[14], addr->s6_addr[15]);
			} else {
				evutil_snprintf(buf, sizeof(buf), "::%x:%d.%d.%d.%d", words[5],
				    addr->s6_addr[12], addr->s6_addr[13],
				    addr->s6_addr[14], addr->s6_addr[15]);
			}
			if (strlen(buf) > len)
				return NULL;
			strlcpy(dst, buf, len);
			return dst;
		}
		i = 0;
		while (i < 8) {
			if (words[i] == 0) {
				curGapPos = i++;
				curGapLen = 1;
				while (i<8 && words[i] == 0) {
					++i; ++curGapLen;
				}
				if (curGapLen > longestGapLen) {
					longestGapPos = curGapPos;
					longestGapLen = curGapLen;
				}
			} else {
				++i;
			}
		}
		if (longestGapLen<=1)
			longestGapPos = -1;

		cp = buf;
		for (i = 0; i < 8; ++i) {
			if (words[i] == 0 && longestGapPos == i) {
				if (i == 0)
					*cp++ = ':';
				*cp++ = ':';
				while (i < 8 && words[i] == 0)
					++i;
				--i; /* to compensate for loop increment. */
			} else {
				evutil_snprintf(cp,
								sizeof(buf)-(cp-buf), "%x", (unsigned)words[i]);
				cp += strlen(cp);
				if (i != 7)
					*cp++ = ':';
			}
		}
		*cp = '\0';
		if (strlen(buf) > len)
			return NULL;
		strlcpy(dst, buf, len);
		return dst;
#endif
	} else {
		return NULL;
	}
#endif
}

int
evutil_inet_pton(int af, const char *src, void *dst)
{
#if defined(EVENT__HAVE_INET_PTON) && !defined(USE_INTERNAL_PTON)
	return inet_pton(af, src, dst);
#else
	if (af == AF_INET) {
		unsigned a,b,c,d;
		char more;
		struct in_addr *addr = dst;
		if (sscanf(src, "%u.%u.%u.%u%c", &a,&b,&c,&d,&more) != 4)
			return 0;
		if (a > 255) return 0;
		if (b > 255) return 0;
		if (c > 255) return 0;
		if (d > 255) return 0;
		addr->s_addr = htonl((a<<24) | (b<<16) | (c<<8) | d);
		return 1;
#ifdef AF_INET6
	} else if (af == AF_INET6) {
		struct in6_addr *out = dst;
		ev_uint16_t words[8];
		int gapPos = -1, i, setWords=0;
		const char *dot = strchr(src, '.');
		const char *eow; /* end of words. */
		if (dot == src)
			return 0;
		else if (!dot)
			eow = src+strlen(src);
		else {
			unsigned byte1,byte2,byte3,byte4;
			char more;
			for (eow = dot-1; eow >= src && EVUTIL_ISDIGIT_(*eow); --eow)
				;
			++eow;

			/* We use "scanf" because some platform inet_aton()s are too lax
			 * about IPv4 addresses of the form "1.2.3" */
			if (sscanf(eow, "%u.%u.%u.%u%c",
					   &byte1,&byte2,&byte3,&byte4,&more) != 4)
				return 0;

			if (byte1 > 255 ||
			    byte2 > 255 ||
			    byte3 > 255 ||
			    byte4 > 255)
				return 0;

			words[6] = (byte1<<8) | byte2;
			words[7] = (byte3<<8) | byte4;
			setWords += 2;
		}

		i = 0;
		while (src < eow) {
			if (i > 7)
				return 0;
			if (EVUTIL_ISXDIGIT_(*src)) {
				char *next;
				long r = strtol(src, &next, 16);
				if (next > 4+src)
					return 0;
				if (next == src)
					return 0;
				if (r<0 || r>65536)
					return 0;

				words[i++] = (ev_uint16_t)r;
				setWords++;
				src = next;
				if (*src != ':' && src != eow)
					return 0;
				++src;
			} else if (*src == ':' && i > 0 && gapPos==-1) {
				gapPos = i;
				++src;
			} else if (*src == ':' && i == 0 && src[1] == ':' && gapPos==-1) {
				gapPos = i;
				src += 2;
			} else {
				return 0;
			}
		}

		if (setWords > 8 ||
			(setWords == 8 && gapPos != -1) ||
			(setWords < 8 && gapPos == -1))
			return 0;

		if (gapPos >= 0) {
			int nToMove = setWords - (dot ? 2 : 0) - gapPos;
			int gapLen = 8 - setWords;
			/* assert(nToMove >= 0); */
			if (nToMove < 0)
				return -1; /* should be impossible */
			memmove(&words[gapPos+gapLen], &words[gapPos],
					sizeof(ev_uint16_t)*nToMove);
			memset(&words[gapPos], 0, sizeof(ev_uint16_t)*gapLen);
		}
		for (i = 0; i < 8; ++i) {
			out->s6_addr[2*i  ] = words[i] >> 8;
			out->s6_addr[2*i+1] = words[i] & 0xff;
		}

		return 1;
#endif
	} else {
		return -1;
	}
#endif
}

int
evutil_parse_sockaddr_port(const char *ip_as_string, struct sockaddr *out, int *outlen)
{
	int port;
	char buf[128];
	const char *cp, *addr_part, *port_part;
	int is_ipv6;
	/* recognized formats are:
	 * [ipv6]:port
	 * ipv6
	 * [ipv6]
	 * ipv4:port
	 * ipv4
	 */

	cp = strchr(ip_as_string, ':');
	if (*ip_as_string == '[') {
		int len;
		if (!(cp = strchr(ip_as_string, ']'))) {
			return -1;
		}
		len = (int) ( cp-(ip_as_string + 1) );
		if (len > (int)sizeof(buf)-1) {
			return -1;
		}
		memcpy(buf, ip_as_string+1, len);
		buf[len] = '\0';
		addr_part = buf;
		if (cp[1] == ':')
			port_part = cp+2;
		else
			port_part = NULL;
		is_ipv6 = 1;
	} else if (cp && strchr(cp+1, ':')) {
		is_ipv6 = 1;
		addr_part = ip_as_string;
		port_part = NULL;
	} else if (cp) {
		is_ipv6 = 0;
		if (cp - ip_as_string > (int)sizeof(buf)-1) {
			return -1;
		}
		memcpy(buf, ip_as_string, cp-ip_as_string);
		buf[cp-ip_as_string] = '\0';
		addr_part = buf;
		port_part = cp+1;
	} else {
		addr_part = ip_as_string;
		port_part = NULL;
		is_ipv6 = 0;
	}

	if (port_part == NULL) {
		port = 0;
	} else {
		port = atoi(port_part);
		if (port <= 0 || port > 65535) {
			return -1;
		}
	}

	if (!addr_part)
		return -1; /* Should be impossible. */
#ifdef AF_INET6
	if (is_ipv6)
	{
		struct sockaddr_in6 sin6;
		memset(&sin6, 0, sizeof(sin6));
#ifdef EVENT__HAVE_STRUCT_SOCKADDR_IN6_SIN6_LEN
		sin6.sin6_len = sizeof(sin6);
#endif
		sin6.sin6_family = AF_INET6;
		sin6.sin6_port = htons(port);
		if (1 != evutil_inet_pton(AF_INET6, addr_part, &sin6.sin6_addr))
			return -1;
		if ((int)sizeof(sin6) > *outlen)
			return -1;
		memset(out, 0, *outlen);
		memcpy(out, &sin6, sizeof(sin6));
		*outlen = sizeof(sin6);
		return 0;
	}
	else
#endif
	{
		struct sockaddr_in sin;
		memset(&sin, 0, sizeof(sin));
#ifdef EVENT__HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
		sin.sin_len = sizeof(sin);
#endif
		sin.sin_family = AF_INET;
		sin.sin_port = htons(port);
		if (1 != evutil_inet_pton(AF_INET, addr_part, &sin.sin_addr))
			return -1;
		if ((int)sizeof(sin) > *outlen)
			return -1;
		memset(out, 0, *outlen);
		memcpy(out, &sin, sizeof(sin));
		*outlen = sizeof(sin);
		return 0;
	}
}

const char *
evutil_format_sockaddr_port_(const struct sockaddr *sa, char *out, size_t outlen)
{
	char b[128];
	const char *res=NULL;
	int port;
	if (sa->sa_family == AF_INET) {
		const struct sockaddr_in *sin = (const struct sockaddr_in*)sa;
		res = evutil_inet_ntop(AF_INET, &sin->sin_addr,b,sizeof(b));
		port = ntohs(sin->sin_port);
		if (res) {
			evutil_snprintf(out, outlen, "%s:%d", b, port);
			return out;
		}
	} else if (sa->sa_family == AF_INET6) {
		const struct sockaddr_in6 *sin6 = (const struct sockaddr_in6*)sa;
		res = evutil_inet_ntop(AF_INET6, &sin6->sin6_addr,b,sizeof(b));
		port = ntohs(sin6->sin6_port);
		if (res) {
			evutil_snprintf(out, outlen, "[%s]:%d", b, port);
			return out;
		}
	}

	evutil_snprintf(out, outlen, "<addr with socktype %d>",
	    (int)sa->sa_family);
	return out;
}

int
evutil_sockaddr_cmp(const struct sockaddr *sa1, const struct sockaddr *sa2,
    int include_port)
{
	int r;
	if (0 != (r = (sa1->sa_family - sa2->sa_family)))
		return r;

	if (sa1->sa_family == AF_INET) {
		const struct sockaddr_in *sin1, *sin2;
		sin1 = (const struct sockaddr_in *)sa1;
		sin2 = (const struct sockaddr_in *)sa2;
		if (sin1->sin_addr.s_addr < sin2->sin_addr.s_addr)
			return -1;
		else if (sin1->sin_addr.s_addr > sin2->sin_addr.s_addr)
			return 1;
		else if (include_port &&
		    (r = ((int)sin1->sin_port - (int)sin2->sin_port)))
			return r;
		else
			return 0;
	}
#ifdef AF_INET6
	else if (sa1->sa_family == AF_INET6) {
		const struct sockaddr_in6 *sin1, *sin2;
		sin1 = (const struct sockaddr_in6 *)sa1;
		sin2 = (const struct sockaddr_in6 *)sa2;
		if ((r = memcmp(sin1->sin6_addr.s6_addr, sin2->sin6_addr.s6_addr, 16)))
			return r;
		else if (include_port &&
		    (r = ((int)sin1->sin6_port - (int)sin2->sin6_port)))
			return r;
		else
			return 0;
	}
#endif
	return 1;
}

/* Tables to implement ctypes-replacement EVUTIL_IS*() functions.  Each table
 * has 256 bits to look up whether a character is in some set or not.  This
 * fails on non-ASCII platforms, but so does every other place where we
 * take a char and write it onto the network.
 **/
static const ev_uint32_t EVUTIL_ISALPHA_TABLE[8] =
  { 0, 0, 0x7fffffe, 0x7fffffe, 0, 0, 0, 0 };
static const ev_uint32_t EVUTIL_ISALNUM_TABLE[8] =
  { 0, 0x3ff0000, 0x7fffffe, 0x7fffffe, 0, 0, 0, 0 };
static const ev_uint32_t EVUTIL_ISSPACE_TABLE[8] = { 0x3e00, 0x1, 0, 0, 0, 0, 0, 0 };
static const ev_uint32_t EVUTIL_ISXDIGIT_TABLE[8] =
  { 0, 0x3ff0000, 0x7e, 0x7e, 0, 0, 0, 0 };
static const ev_uint32_t EVUTIL_ISDIGIT_TABLE[8] = { 0, 0x3ff0000, 0, 0, 0, 0, 0, 0 };
static const ev_uint32_t EVUTIL_ISPRINT_TABLE[8] =
  { 0, 0xffffffff, 0xffffffff, 0x7fffffff, 0, 0, 0, 0x0 };
static const ev_uint32_t EVUTIL_ISUPPER_TABLE[8] = { 0, 0, 0x7fffffe, 0, 0, 0, 0, 0 };
static const ev_uint32_t EVUTIL_ISLOWER_TABLE[8] = { 0, 0, 0, 0x7fffffe, 0, 0, 0, 0 };
/* Upper-casing and lowercasing tables to map characters to upper/lowercase
 * equivalents. */
static const unsigned char EVUTIL_TOUPPER_TABLE[256] = {
  0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
  16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,
  32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,
  48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,
  64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,
  80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,
  96,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,
  80,81,82,83,84,85,86,87,88,89,90,123,124,125,126,127,
  128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
  144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,
  160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,
  176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,
  192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,
  208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,
  224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,
  240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,
};
static const unsigned char EVUTIL_TOLOWER_TABLE[256] = {
  0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
  16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,
  32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,
  48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,
  64,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,
  112,113,114,115,116,117,118,119,120,121,122,91,92,93,94,95,
  96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,
  112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,
  128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
  144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,
  160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,
  176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,
  192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,
  208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,
  224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,
  240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,
};

#define IMPL_CTYPE_FN(name)						\
	int EVUTIL_##name##_(char c) {					\
		ev_uint8_t u = c;					\
		return !!(EVUTIL_##name##_TABLE[(u >> 5) & 7] & (1 << (u & 31))); \
	}
IMPL_CTYPE_FN(ISALPHA)
IMPL_CTYPE_FN(ISALNUM)
IMPL_CTYPE_FN(ISSPACE)
IMPL_CTYPE_FN(ISDIGIT)
IMPL_CTYPE_FN(ISXDIGIT)
IMPL_CTYPE_FN(ISPRINT)
IMPL_CTYPE_FN(ISLOWER)
IMPL_CTYPE_FN(ISUPPER)

char EVUTIL_TOLOWER_(char c)
{
	return ((char)EVUTIL_TOLOWER_TABLE[(ev_uint8_t)c]);
}
char EVUTIL_TOUPPER_(char c)
{
	return ((char)EVUTIL_TOUPPER_TABLE[(ev_uint8_t)c]);
}
int
evutil_ascii_strcasecmp(const char *s1, const char *s2)
{
	char c1, c2;
	while (1) {
		c1 = EVUTIL_TOLOWER_(*s1++);
		c2 = EVUTIL_TOLOWER_(*s2++);
		if (c1 < c2)
			return -1;
		else if (c1 > c2)
			return 1;
		else if (c1 == 0)
			return 0;
	}
}
int evutil_ascii_strncasecmp(const char *s1, const char *s2, size_t n)
{
	char c1, c2;
	while (n--) {
		c1 = EVUTIL_TOLOWER_(*s1++);
		c2 = EVUTIL_TOLOWER_(*s2++);
		if (c1 < c2)
			return -1;
		else if (c1 > c2)
			return 1;
		else if (c1 == 0)
			return 0;
	}
	return 0;
}

void
evutil_rtrim_lws_(char *str)
{
	char *cp;

	if (str == NULL)
		return;

	if ((cp = strchr(str, '\0')) == NULL || (cp == str))
		return;

	--cp;

	while (*cp == ' ' || *cp == '\t') {
		*cp = '\0';
		if (cp == str)
			break;
		--cp;
	}
}

static int
evutil_issetugid(void)
{
#ifdef EVENT__HAVE_ISSETUGID
	return issetugid();
#else

#ifdef EVENT__HAVE_GETEUID
	if (getuid() != geteuid())
		return 1;
#endif
#ifdef EVENT__HAVE_GETEGID
	if (getgid() != getegid())
		return 1;
#endif
	return 0;
#endif
}

const char *
evutil_getenv_(const char *varname)
{
	if (evutil_issetugid())
		return NULL;

	return getenv(varname);
}

ev_uint32_t
evutil_weakrand_seed_(struct evutil_weakrand_state *state, ev_uint32_t seed)
{
	if (seed == 0) {
		struct timeval tv;
		evutil_gettimeofday(&tv, NULL);
		seed = (ev_uint32_t)tv.tv_sec + (ev_uint32_t)tv.tv_usec;
#ifdef _WIN32
		seed += (ev_uint32_t) _getpid();
#else
		seed += (ev_uint32_t) getpid();
#endif
	}
	state->seed = seed;
	return seed;
}

ev_int32_t
evutil_weakrand_(struct evutil_weakrand_state *state)
{
	/* This RNG implementation is a linear congruential generator, with
	 * modulus 2^31, multiplier 1103515245, and addend 12345.  It's also
	 * used by OpenBSD, and by Glibc's TYPE_0 RNG.
	 *
	 * The linear congruential generator is not an industrial-strength
	 * RNG!  It's fast, but it can have higher-order patterns.  Notably,
	 * the low bits tend to have periodicity.
	 */
	state->seed = ((state->seed) * 1103515245 + 12345) & 0x7fffffff;
	return (ev_int32_t)(state->seed);
}

ev_int32_t
evutil_weakrand_range_(struct evutil_weakrand_state *state, ev_int32_t top)
{
	ev_int32_t divisor, result;

	/* We can't just do weakrand() % top, since the low bits of the LCG
	 * are less random than the high ones.  (Specifically, since the LCG
	 * modulus is 2^N, every 2^m for m<N will divide the modulus, and so
	 * therefore the low m bits of the LCG will have period 2^m.) */
	divisor = EVUTIL_WEAKRAND_MAX / top;
	do {
		result = evutil_weakrand_(state) / divisor;
	} while (result >= top);
	return result;
}

/**
 * Volatile pointer to memset: we use this to keep the compiler from
 * eliminating our call to memset.
 */
void * (*volatile evutil_memset_volatile_)(void *, int, size_t) = memset;

void
evutil_memclear_(void *mem, size_t len)
{
	evutil_memset_volatile_(mem, 0, len);
}

int
evutil_sockaddr_is_loopback_(const struct sockaddr *addr)
{
	static const char LOOPBACK_S6[16] =
	    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1";
	if (addr->sa_family == AF_INET) {
		struct sockaddr_in *sin = (struct sockaddr_in *)addr;
		return (ntohl(sin->sin_addr.s_addr) & 0xff000000) == 0x7f000000;
	} else if (addr->sa_family == AF_INET6) {
		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)addr;
		return !memcmp(sin6->sin6_addr.s6_addr, LOOPBACK_S6, 16);
	}
	return 0;
}

int
evutil_hex_char_to_int_(char c)
{
	switch(c)
	{
		case '0': return 0;
		case '1': return 1;
		case '2': return 2;
		case '3': return 3;
		case '4': return 4;
		case '5': return 5;
		case '6': return 6;
		case '7': return 7;
		case '8': return 8;
		case '9': return 9;
		case 'A': case 'a': return 10;
		case 'B': case 'b': return 11;
		case 'C': case 'c': return 12;
		case 'D': case 'd': return 13;
		case 'E': case 'e': return 14;
		case 'F': case 'f': return 15;
	}
	return -1;
}

#ifdef _WIN32
HMODULE
evutil_load_windows_system_library_(const TCHAR *library_name)
{
  TCHAR path[MAX_PATH];
  unsigned n;
  n = GetSystemDirectory(path, MAX_PATH);
  if (n == 0 || n + _tcslen(library_name) + 2 >= MAX_PATH)
    return 0;
  _tcscat(path, TEXT("\\"));
  _tcscat(path, library_name);
  return LoadLibrary(path);
}
#endif

/* Internal wrapper around 'socket' to provide Linux-style support for
 * syscall-saving methods where available.
 *
 * In addition to regular socket behavior, you can use a bitwise or to set the
 * flags EVUTIL_SOCK_NONBLOCK and EVUTIL_SOCK_CLOEXEC in the 'type' argument,
 * to make the socket nonblocking or close-on-exec with as few syscalls as
 * possible.
 */
evutil_socket_t
evutil_socket_(int domain, int type, int protocol)
{
	evutil_socket_t r;
#if defined(SOCK_NONBLOCK) && defined(SOCK_CLOEXEC)
	r = socket(domain, type, protocol);
	if (r >= 0)
		return r;
	else if ((type & (SOCK_NONBLOCK|SOCK_CLOEXEC)) == 0)
		return -1;
#endif
#define SOCKET_TYPE_MASK (~(EVUTIL_SOCK_NONBLOCK|EVUTIL_SOCK_CLOEXEC))
	r = socket(domain, type & SOCKET_TYPE_MASK, protocol);
	if (r < 0)
		return -1;
	if (type & EVUTIL_SOCK_NONBLOCK) {
		if (evutil_fast_socket_nonblocking(r) < 0) {
			evutil_closesocket(r);
			return -1;
		}
	}
	if (type & EVUTIL_SOCK_CLOEXEC) {
		if (evutil_fast_socket_closeonexec(r) < 0) {
			evutil_closesocket(r);
			return -1;
		}
	}
	return r;
}

/* Internal wrapper around 'accept' or 'accept4' to provide Linux-style
 * support for syscall-saving methods where available.
 *
 * In addition to regular accept behavior, you can set one or more of flags
 * EVUTIL_SOCK_NONBLOCK and EVUTIL_SOCK_CLOEXEC in the 'flags' argument, to
 * make the socket nonblocking or close-on-exec with as few syscalls as
 * possible.
 */
evutil_socket_t
evutil_accept4_(evutil_socket_t sockfd, struct sockaddr *addr,
    ev_socklen_t *addrlen, int flags)
{
	evutil_socket_t result;
#if defined(EVENT__HAVE_ACCEPT4) && defined(SOCK_CLOEXEC) && defined(SOCK_NONBLOCK)
	result = accept4(sockfd, addr, addrlen, flags);
	if (result >= 0 || (errno != EINVAL && errno != ENOSYS)) {
		/* A nonnegative result means that we succeeded, so return.
		 * Failing with EINVAL means that an option wasn't supported,
		 * and failing with ENOSYS means that the syscall wasn't
		 * there: in those cases we want to fall back.  Otherwise, we
		 * got a real error, and we should return. */
		return result;
	}
#endif
	result = accept(sockfd, addr, addrlen);
	if (result < 0)
		return result;

	if (flags & EVUTIL_SOCK_CLOEXEC) {
		if (evutil_fast_socket_closeonexec(result) < 0) {
			evutil_closesocket(result);
			return -1;
		}
	}
	if (flags & EVUTIL_SOCK_NONBLOCK) {
		if (evutil_fast_socket_nonblocking(result) < 0) {
			evutil_closesocket(result);
			return -1;
		}
	}
	return result;
}

/* Internal function: Set fd[0] and fd[1] to a pair of fds such that writes on
 * fd[0] get read from fd[1].  Make both fds nonblocking and close-on-exec.
 * Return 0 on success, -1 on failure.
 */
int
evutil_make_internal_pipe_(evutil_socket_t fd[2])
{
	/*
	  Making the second socket nonblocking is a bit subtle, given that we
	  ignore any EAGAIN returns when writing to it, and you don't usally
	  do that for a nonblocking socket. But if the kernel gives us EAGAIN,
	  then there's no need to add any more data to the buffer, since
	  the main thread is already either about to wake up and drain it,
	  or woken up and in the process of draining it.
	*/

#if defined(EVENT__HAVE_PIPE2)
	if (pipe2(fd, O_NONBLOCK|O_CLOEXEC) == 0)
		return 0;
#endif
#if defined(EVENT__HAVE_PIPE)
	if (pipe(fd) == 0) {
		if (evutil_fast_socket_nonblocking(fd[0]) < 0 ||
		    evutil_fast_socket_nonblocking(fd[1]) < 0 ||
		    evutil_fast_socket_closeonexec(fd[0]) < 0 ||
		    evutil_fast_socket_closeonexec(fd[1]) < 0) {
			close(fd[0]);
			close(fd[1]);
			fd[0] = fd[1] = -1;
			return -1;
		}
		return 0;
	} else {
		event_warn("%s: pipe", __func__);
	}
#endif

#ifdef _WIN32
#define LOCAL_SOCKETPAIR_AF AF_INET
#else
#define LOCAL_SOCKETPAIR_AF AF_UNIX
#endif
	if (evutil_socketpair(LOCAL_SOCKETPAIR_AF, SOCK_STREAM, 0, fd) == 0) {
		if (evutil_fast_socket_nonblocking(fd[0]) < 0 ||
		    evutil_fast_socket_nonblocking(fd[1]) < 0 ||
		    evutil_fast_socket_closeonexec(fd[0]) < 0 ||
		    evutil_fast_socket_closeonexec(fd[1]) < 0) {
			evutil_closesocket(fd[0]);
			evutil_closesocket(fd[1]);
			fd[0] = fd[1] = -1;
			return -1;
		}
		return 0;
	}
	fd[0] = fd[1] = -1;
	return -1;
}

/* Wrapper around eventfd on systems that provide it.  Unlike the system
 * eventfd, it always supports EVUTIL_EFD_CLOEXEC and EVUTIL_EFD_NONBLOCK as
 * flags.  Returns -1 on error or if eventfd is not supported.
 */
evutil_socket_t
evutil_eventfd_(unsigned initval, int flags)
{
#if defined(EVENT__HAVE_EVENTFD) && defined(EVENT__HAVE_SYS_EVENTFD_H)
	int r;
#if defined(EFD_CLOEXEC) && defined(EFD_NONBLOCK)
	r = eventfd(initval, flags);
	if (r >= 0 || flags == 0)
		return r;
#endif
	r = eventfd(initval, 0);
	if (r < 0)
		return r;
	if (flags & EVUTIL_EFD_CLOEXEC) {
		if (evutil_fast_socket_closeonexec(r) < 0) {
			evutil_closesocket(r);
			return -1;
		}
	}
	if (flags & EVUTIL_EFD_NONBLOCK) {
		if (evutil_fast_socket_nonblocking(r) < 0) {
			evutil_closesocket(r);
			return -1;
		}
	}
	return r;
#else
	return -1;
#endif
}

void
evutil_free_globals_(void)
{
	evutil_free_secure_rng_globals_();
	evutil_free_sock_err_globals();
}