diff --git a/include/netdb.h b/include/netdb.h
index 0fa4d16c57f8..ba3ed32f39a9 100644
--- a/include/netdb.h
+++ b/include/netdb.h
@@ -82,7 +82,7 @@ typedef	__socklen_t	socklen_t;
 #define	_PATH_PROTOCOLS	"/etc/protocols"
 #define	_PATH_SERVICES	"/etc/services"
 
-extern int h_errno;
+#define	h_errno (*__h_error())
 
 /*
  * Structures returned by network data base library.  All addresses are
@@ -135,7 +135,7 @@ struct addrinfo {
 
 /*
  * Error return codes from gethostbyname() and gethostbyaddr()
- * (left in extern int h_errno).
+ * (left in h_errno).
  */
 
 #define	NETDB_INTERNAL	-1	/* see errno */
@@ -254,6 +254,7 @@ void		setservent(int);
  */
 
 /* DO NOT USE THESE, THEY ARE SUBJECT TO CHANGE AND ARE NOT PORTABLE!!! */
+int	* __h_error(void);
 void	_sethosthtent(int);
 void	_endhosthtent(void);
 void	_sethostdnsent(int);
diff --git a/include/resolv.h b/include/resolv.h
index 9305023dbb9a..942d2d6f8721 100644
--- a/include/resolv.h
+++ b/include/resolv.h
@@ -200,7 +200,12 @@ struct res_sym {
 	char *	humanname;	/* Its fun name, like "mail exchanger" */
 };
 
-extern struct __res_state _res;
+__BEGIN_DECLS
+extern struct __res_state *___res(void);
+extern struct __res_state_ext *___res_ext(void);
+__END_DECLS
+#define	_res		(*___res())
+#define	_res_ext	(*___res_ext())
 /* for INET6 */
 extern struct __res_state_ext _res_ext;
 
diff --git a/lib/libc/include/reentrant.h b/lib/libc/include/reentrant.h
index 8ce3af67e304..8ab328bc6279 100644
--- a/lib/libc/include/reentrant.h
+++ b/lib/libc/include/reentrant.h
@@ -94,10 +94,12 @@
 #define mutex_t			pthread_mutex_t
 #define cond_t			pthread_cond_t
 #define rwlock_t		pthread_rwlock_t
+#define once_t			pthread_once_t
 
 #define thread_key_t		pthread_key_t
 #define MUTEX_INITIALIZER	PTHREAD_MUTEX_INITIALIZER
 #define RWLOCK_INITIALIZER	PTHREAD_RWLOCK_INITIALIZER
+#define ONCE_INITIALIZER	PTHREAD_ONCE_INIT
 
 #define mutex_init(m, a)	_pthread_mutex_init(m, a)
 #define mutex_lock(m)		if (__isthreaded) \
@@ -127,6 +129,7 @@
 #define thr_getspecific(k)	_pthread_getspecific(k)
 #define thr_sigsetmask(f, n, o)	_pthread_sigmask(f, n, o)
 
+#define thr_once(o, i)		_pthread_once(o, i)
 #define thr_self()		_pthread_self()
 #define thr_exit(x)		_pthread_exit(x)
 #define thr_main()		_pthread_main_np()
diff --git a/lib/libc/net/getaddrinfo.3 b/lib/libc/net/getaddrinfo.3
index 36922dab8521..472a9183ac18 100644
--- a/lib/libc/net/getaddrinfo.3
+++ b/lib/libc/net/getaddrinfo.3
@@ -618,10 +618,14 @@ and documented in
 (RFC2553).
 .\"
 .Sh BUGS
-Though the current implementation should be thread-safe, using
+Although the current implementation is otherwise thread-safe, using
 .Fn getaddrinfo
 in conjunction with
 .Fn gethostby*
-breaks thread-safeness.
+(see
+.Xr gethostbyname 3 )
+or
+.Xr yp 8
+breaks the thread-safety of both.
 .Pp
 The text was shamelessly copied from RFC2553.
diff --git a/lib/libc/net/getaddrinfo.c b/lib/libc/net/getaddrinfo.c
index df05b0e53847..dc21cc231f04 100644
--- a/lib/libc/net/getaddrinfo.c
+++ b/lib/libc/net/getaddrinfo.c
@@ -305,10 +305,10 @@ static struct ai_errlist {
 };
 
 /*
- * XXX: Our res_*() is not thread-safe.  So, we share lock between
+ * XXX: Many dependencies are not thread-safe.  So, we share lock between
  * getaddrinfo() and getipnodeby*().  Still, we cannot use
  * getaddrinfo() and getipnodeby*() in conjunction with other
- * functions which call res_*().
+ * functions which call them.
  */
 pthread_mutex_t __getaddrinfo_thread_lock = PTHREAD_MUTEX_INITIALIZER;
 #define THREAD_LOCK() \
@@ -1348,9 +1348,13 @@ get_port(ai, servname, matchonly)
 			break;
 		}
 
-		if ((sp = getservbyname(servname, proto)) == NULL)
+		THREAD_LOCK();
+		if ((sp = getservbyname(servname, proto)) == NULL) {
+			THREAD_UNLOCK();
 			return EAI_SERVICE;
+		}
 		port = sp->s_port;
+		THREAD_UNLOCK();
 	}
 
 	if (!matchonly) {
@@ -1501,15 +1505,11 @@ explore_fqdn(pai, hostname, servname, res)
 
 	result = NULL;
 
-	THREAD_LOCK();
-
 	/*
 	 * if the servname does not match socktype/protocol, ignore it.
 	 */
-	if (get_portmatch(pai, servname) != 0) {
-		THREAD_UNLOCK();
+	if (get_portmatch(pai, servname) != 0)
 		return 0;
-	}
 
 	switch (_nsdispatch(&result, dtab, NSDB_HOSTS, "getaddrinfo",
 			default_dns_files, hostname, pai)) {
@@ -1530,14 +1530,12 @@ explore_fqdn(pai, hostname, servname, res)
 		}
 		break;
 	}
-	THREAD_UNLOCK();
 
 	*res = result;
 
 	return 0;
 
 free:
-	THREAD_UNLOCK();
 	if (result)
 		freeaddrinfo(result);
 	return error;
@@ -2037,6 +2035,7 @@ _files_getaddrinfo(rv, cb_data, ap)
 	memset(&sentinel, 0, sizeof(sentinel));
 	cur = &sentinel;
 
+	THREAD_LOCK();
 	_sethtent();
 	while ((p = _gethtent(name, pai)) != NULL) {
 		cur->ai_next = p;
@@ -2044,6 +2043,7 @@ _files_getaddrinfo(rv, cb_data, ap)
 			cur = cur->ai_next;
 	}
 	_endhtent();
+	THREAD_UNLOCK();
 
 	*((struct addrinfo **)rv) = sentinel.ai_next;
 	if (sentinel.ai_next == NULL)
@@ -2152,9 +2152,12 @@ _yp_getaddrinfo(rv, cb_data, ap)
 	memset(&sentinel, 0, sizeof(sentinel));
 	cur = &sentinel;
 
+	THREAD_LOCK();
 	if (!__ypdomain) {
-		if (_yp_check(&__ypdomain) == 0)
+		if (_yp_check(&__ypdomain) == 0) {
+			THREAD_UNLOCK();
 			return NS_UNAVAIL;
+		}
 	}
 	if (__ypcurrent)
 		free(__ypcurrent);
@@ -2189,6 +2192,7 @@ _yp_getaddrinfo(rv, cb_data, ap)
 				cur = cur->ai_next;
 		}
 	}
+	THREAD_UNLOCK();
 
 	if (sentinel.ai_next == NULL) {
 		h_errno = HOST_NOT_FOUND;
@@ -2202,7 +2206,6 @@ _yp_getaddrinfo(rv, cb_data, ap)
 /* resolver logic */
 
 extern const char *__hostalias(const char *);
-extern int h_errno;
 
 /*
  * Formulate a normal query, send, and await answer.
diff --git a/lib/libc/net/gethostbydns.c b/lib/libc/net/gethostbydns.c
index 02cd223b2439..82f515214caf 100644
--- a/lib/libc/net/gethostbydns.c
+++ b/lib/libc/net/gethostbydns.c
@@ -116,7 +116,6 @@ typedef union {
     char ac;
 } align;
 
-extern int h_errno;
 int _dns_ttl_;
 
 #ifdef DEBUG
diff --git a/lib/libc/net/gethostbyname.3 b/lib/libc/net/gethostbyname.3
index e703e3221275..a4486bc6e9f8 100644
--- a/lib/libc/net/gethostbyname.3
+++ b/lib/libc/net/gethostbyname.3
@@ -369,6 +369,12 @@ version 4.9.4.
 These functions use static data storage;
 if the data is needed for future use, it should be
 copied before any subsequent calls overwrite it.
+Threaded applications should never use them, as they will also conflict
+with the
+.Xr getaddrinfo 3
+and
+.Xr getipnodebyname 3
+families of functions (which should be used instead).
 Only the Internet
 address format is currently understood.
 .Pp
diff --git a/lib/libc/net/gethostbynis.c b/lib/libc/net/gethostbynis.c
index 73b12edbc15b..88bd310b8dca 100644
--- a/lib/libc/net/gethostbynis.c
+++ b/lib/libc/net/gethostbynis.c
@@ -48,8 +48,6 @@ __FBSDID("$FreeBSD$");
 #define	MAXALIASES	35
 #define	MAXADDRS	35
 
-extern int h_errno;
-
 #ifdef YP
 static char *host_aliases[MAXALIASES];
 static char hostaddr[MAXADDRS];
diff --git a/lib/libc/net/getipnodebyname.3 b/lib/libc/net/getipnodebyname.3
index d0b0b8cffefe..1ade42d2cee8 100644
--- a/lib/libc/net/getipnodebyname.3
+++ b/lib/libc/net/getipnodebyname.3
@@ -455,6 +455,15 @@ are documented in
 (RFC2553).
 .\"
 .Sh BUGS
+Although the current implementation is otherwise thread-safe, using
+it in conjunction with
+.Fn gethostby*
+(see 
+.Xr gethostbyname 3 )
+or
+.Xr yp 8
+breaks the thread-safety of both.
+.Pp
 The
 .Fn getipnodebyname
 and
@@ -469,6 +478,4 @@ and
 .Fn getnameinfo 3
 are recommended.
 .Pp
-The current implementation is not thread-safe.
-.Pp
 The text was shamelessly copied from RFC2553.
diff --git a/lib/libc/net/herror.c b/lib/libc/net/herror.c
index 9f3dbb7d18f2..b84c06c1069f 100644
--- a/lib/libc/net/herror.c
+++ b/lib/libc/net/herror.c
@@ -69,9 +69,7 @@ const char *h_errlist[] = {
 	"Unknown server error",			/* 3 NO_RECOVERY */
 	"No address associated with name",	/* 4 NO_ADDRESS */
 };
-int	h_nerr = { sizeof h_errlist / sizeof h_errlist[0] };
-
-int	h_errno;
+const int h_nerr = { sizeof h_errlist / sizeof h_errlist[0] };
 
 /*
  * herror --
@@ -110,3 +108,6 @@ hstrerror(err)
 		return (h_errlist[err]);
 	return ("Unknown resolver error");
 }
+
+#undef h_errno
+int	h_errno;
diff --git a/lib/libc/net/name6.c b/lib/libc/net/name6.c
index c8abf9a4d76c..3d42e3c196bc 100644
--- a/lib/libc/net/name6.c
+++ b/lib/libc/net/name6.c
@@ -211,10 +211,10 @@ static int	 _icmp_ghbyaddr(void *, void *, va_list);
 #endif /* ICMPNL */
 
 /*
- * XXX: Our res_*() is not thread-safe.  So, we share lock between
+ * XXX: Many dependencies are not thread-safe.  So, we share lock between
  * getaddrinfo() and getipnodeby*().  Still, we cannot use
  * getaddrinfo() and getipnodeby*() in conjunction with other
- * functions which call res_*().
+ * functions which call them.
  */
 #include "libc_private.h"
 extern pthread_mutex_t __getaddrinfo_thread_lock;
@@ -309,10 +309,8 @@ _ghbyname(const char *name, int af, int flags, int *errp)
 		}
 	}
 
-	THREAD_LOCK();
 	rval = _nsdispatch(&hp, dtab, NSDB_HOSTS, "ghbyname", default_src,
 			  name, af, errp);
-	THREAD_UNLOCK();
 	return (rval == NS_SUCCESS) ? hp : NULL;
 }
 
@@ -456,10 +454,8 @@ getipnodebyaddr(const void *src, size_t len, int af, int *errp)
 		return NULL;
 	}
 
-	THREAD_LOCK();
 	rval = _nsdispatch(&hp, dtab, NSDB_HOSTS, "ghbyaddr", default_src,
 			  src, len, af, errp);
-	THREAD_UNLOCK();
 	return (rval == NS_SUCCESS) ? hp : NULL;
 }
 
@@ -1169,9 +1165,11 @@ _nis_ghbyname(void *rval, void *cb_data, va_list ap)
 	if (af == AF_UNSPEC)
 		af = AF_INET;
 	if (af == AF_INET) {
+		THREAD_LOCK();
 		hp = _gethostbynisname(name, af);
 		if (hp != NULL)
 			hp = _hpcopy(hp, errp);
+		THREAD_UNLOCK();
 	}
 	
 	*(struct hostent **)rval = hp;
@@ -1193,9 +1191,11 @@ _nis_ghbyaddr(void *rval, void *cb_data, va_list ap)
 	af = va_arg(ap, int);
 
 	if (af == AF_INET) {
+		THREAD_LOCK();
 		hp = _gethostbynisaddr(addr, addrlen, af);
 		if (hp != NULL)
 			hp = _hpcopy(hp, errp);
+		THREAD_UNLOCK();
 	}
 	*(struct hostent **)rval = hp;
 	return (hp != NULL) ? NS_SUCCESS : NS_NOTFOUND;
@@ -1932,18 +1932,17 @@ _icmp_fqdn_query(const struct in6_addr *addr, int ifindex)
 	struct timeval tout;
 	int len;
 	char *name;
-	static int pid;
 	static struct _icmp_host_cache *hc_head;
 
+	THREAD_LOCK();
 	for (hc = hc_head; hc; hc = hc->hc_next) {
 		if (hc->hc_ifindex == ifindex
-		&&  IN6_ARE_ADDR_EQUAL(&hc->hc_addr, addr))
-			return hc->hc_name;
+		&&  IN6_ARE_ADDR_EQUAL(&hc->hc_addr, addr)) {
+			THREAD_UNLOCK();
+			return hc->hc_name;	/* XXX: never freed */
+		}
 	}
 
-	if (pid == 0)
-		pid = getpid();
-
 	ICMP6_FILTER_SETBLOCKALL(&filter);
 	ICMP6_FILTER_SETPASS(ICMP6_FQDN_REPLY, &filter);
 
@@ -1955,7 +1954,7 @@ _icmp_fqdn_query(const struct in6_addr *addr, int ifindex)
 	fq->icmp6_fqdn_type = ICMP6_FQDN_QUERY;
 	fq->icmp6_fqdn_code = 0;
 	fq->icmp6_fqdn_cksum = 0;
-	fq->icmp6_fqdn_id = (u_short)pid;
+	fq->icmp6_fqdn_id = (u_short)getpid();
 	fq->icmp6_fqdn_unused = 0;
 	fq->icmp6_fqdn_cookie[0] = 0;
 	fq->icmp6_fqdn_cookie[1] = 0;
@@ -2038,8 +2037,10 @@ _icmp_fqdn_query(const struct in6_addr *addr, int ifindex)
 	hc->hc_ifindex = ifindex;
 	hc->hc_addr = *addr;
 	hc->hc_name = strdup(name);
+	THREAD_LOCK();
 	hc->hc_next = hc_head;
 	hc_head = hc;
+	THREAD_UNLOCK();
 	return hc->hc_name;
 }
 
diff --git a/lib/libc/net/res_init.c b/lib/libc/net/res_init.c
index 6c229730df77..1d48f606d156 100644
--- a/lib/libc/net/res_init.c
+++ b/lib/libc/net/res_init.c
@@ -91,7 +91,14 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 #include <netdb.h>
 
+#include "namespace.h"
+#include "reentrant.h"
+#include "un-namespace.h"
 #include "res_config.h"
+#include "res_send_private.h"
+
+#undef h_errno
+extern int h_errno;
 
 static void res_setoptions(char *, char *);
 
@@ -106,16 +113,14 @@ static u_int32_t net_mask(struct in_addr);
 #endif
 
 /*
- * Resolver state default settings.
+ * Check structure for failed per-thread allocations.
  */
-
-struct __res_state _res
-# if defined(__BIND_RES_TEXT)
-	= { RES_TIMEOUT, }	/* Motorola, et al. */
-# endif
-	;
-
-struct __res_state_ext _res_ext;
+static struct res_per_thread {
+	struct __res_state res_state;
+	struct __res_state_ext res_state_ext;
+	struct __res_send_private res_send_private;
+	int h_errno;
+} _res_per_thread_bogus = { .res_send_private = { .s = -1 } }; /* socket */
 
 /*
  * Set up default settings.  If the configuration file exist, the values
@@ -142,6 +147,7 @@ int
 res_init()
 {
 	FILE *fp;
+	struct __res_send_private *rsp;
 	char *cp, **pp;
 	int n;
 	char buf[MAXDNAME];
@@ -156,6 +162,19 @@ res_init()
 	int dots;
 #endif
 
+	/*
+	 * If allocation of memory for this thread's resolver has failed,
+	 * return the error to the user.
+	 */
+	if (&_res == &_res_per_thread_bogus.res_state)
+		return (-1);
+	rsp = ___res_send_private();
+	rsp->s = -1;
+	rsp->connected = 0;
+	rsp->vc = 0;
+	rsp->af = 0;
+	rsp->Qhook = NULL;
+	rsp->Rhook = NULL;
 	/*
 	 * These three fields used to be statically initialized.  This made
 	 * it hard to use this code in a shared library.  It is necessary,
@@ -597,6 +616,97 @@ res_randomid()
 	return (0xffff & (now.tv_sec ^ now.tv_usec ^ getpid()));
 }
 
+/*
+ * Resolver state default settings.
+ */
+
+#undef _res
+#undef _res_ext
+#ifdef __BIND_RES_TEXT
+struct __res_state _res = { RES_TIMEOUT };	/* Motorola, et al. */
+#else
+struct __res_state _res;
+#endif
+struct __res_state_ext _res_ext;
+static struct __res_send_private _res_send_private = { .s = -1 }; /* socket */
+
+static thread_key_t res_key;
+static once_t res_init_once = ONCE_INITIALIZER;
+static int res_thr_keycreated = 0;
+
+static void
+free_res(void *ptr)
+{
+	struct res_per_thread *myrsp = ptr;
+
+	if (myrsp->res_state.options & RES_INIT)
+		res_close();
+	free(myrsp);
+}
+
+static void
+res_keycreate(void)
+{
+	res_thr_keycreated = thr_keycreate(&res_key, free_res) == 0;
+}
+
+static struct res_per_thread *
+allocate_res(void)
+{
+	struct res_per_thread *myrsp;
+	
+	if (thr_once(&res_init_once, res_keycreate) != 0 ||
+	    !res_thr_keycreated)
+		return (&_res_per_thread_bogus);
+
+	myrsp = thr_getspecific(res_key);
+	if (myrsp != NULL)
+		return (myrsp);
+	myrsp = calloc(1, sizeof(*myrsp));
+	if (myrsp == NULL)
+		return (&_res_per_thread_bogus);
+#ifdef __BIND_RES_TEXT
+	myrsp->res_state.options = RES_TIMEOUT;		/* Motorola, et al. */
+#endif
+	myrsp->res_send_private.s = -1;			/* socket */
+	if (thr_setspecific(res_key, myrsp) == 0)
+		return (myrsp);
+	free(myrsp);
+	return (&_res_per_thread_bogus);
+}
+
+struct __res_state *
+___res(void)
+{
+	if (thr_main() != 0)
+		return (&_res);
+	return (&allocate_res()->res_state);
+}
+
+struct __res_state_ext *
+___res_ext(void)
+{
+	if (thr_main() != 0)
+		return (&_res_ext);
+	return (&allocate_res()->res_state_ext);
+}
+
+struct __res_send_private *
+___res_send_private(void)
+{
+	if (thr_main() != 0)
+		return (&_res_send_private);
+	return (&allocate_res()->res_send_private);
+}
+
+int *
+__h_error(void)
+{
+	if (thr_main() != 0)
+		return (&h_errno);
+	return (&allocate_res()->h_errno);
+}
+
 /*
  * Weak aliases for applications that use certain private entry points,
  * and fail to include <resolv.h>.
diff --git a/lib/libc/net/res_send.c b/lib/libc/net/res_send.c
index fea5f5423d45..d39bbc5a09fa 100644
--- a/lib/libc/net/res_send.c
+++ b/lib/libc/net/res_send.c
@@ -101,14 +101,15 @@ __FBSDID("$FreeBSD$");
 #include "un-namespace.h"
 
 #include "res_config.h"
+#include "res_send_private.h"
 
-static int s = -1;		/* socket used for communications */
-static int connected = 0;	/* is the socket connected */
-static int vc = 0;		/* is the socket a virtual circuit? */
-static int af = 0;		/* address family of socket */
-static res_send_qhook Qhook = NULL;
-static res_send_rhook Rhook = NULL;
 
+#define	s		___res_send_private()->s
+#define	connected	___res_send_private()->connected
+#define	vc		___res_send_private()->vc
+#define	af		___res_send_private()->af
+#define	Qhook		___res_send_private()->Qhook
+#define	Rhook		___res_send_private()->Rhook
 
 #define CAN_RECONNECT 1
 
@@ -123,8 +124,6 @@ static res_send_rhook Rhook = NULL;
 			fprintf args;\
 			__fp_nquery(query, size, stdout);\
 		} else {}
-static char abuf[NI_MAXHOST];
-static char pbuf[NI_MAXSERV];
 static void Aerror(FILE *, char *, int, struct sockaddr *);
 static void Perror(FILE *, char *, int);
 
@@ -138,6 +137,9 @@ static void Perror(FILE *, char *, int);
 	int save = errno;
 
 	if (_res.options & RES_DEBUG) {
+		char abuf[NI_MAXHOST];
+		char pbuf[NI_MAXSERV];
+
 		if (getnameinfo(address, address->sa_len, abuf, sizeof(abuf),
 		    pbuf, sizeof(pbuf),
 		    NI_NUMERICHOST|NI_NUMERICSERV|NI_WITHSCOPEID) != 0) {
@@ -388,6 +390,7 @@ res_send(buf, buflen, ans, anssiz)
 	 */
 	for (try = 0; try < _res.retry; try++) {
 	    for (ns = 0; ns < _res.nscount; ns++) {
+		char abuf[NI_MAXHOST];
 		struct sockaddr *nsap = get_nsaddr(ns);
 		socklen_t salen;
 
diff --git a/lib/libc/net/res_send_private.h b/lib/libc/net/res_send_private.h
new file mode 100644
index 000000000000..df96dda27608
--- /dev/null
+++ b/lib/libc/net/res_send_private.h
@@ -0,0 +1,82 @@
+/* $FreeBSD$ */
+
+/*
+ * Copyright (c) 1985, 1989, 1993
+ *    The Regents of the University of California.  All rights reserved.
+ * 
+ * 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. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ * 	This product includes software developed by the University of
+ * 	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
+ */
+
+/*
+ * Portions Copyright (c) 1993 by Digital Equipment Corporation.
+ * 
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies, and that
+ * the name of Digital Equipment Corporation not be used in advertising or
+ * publicity pertaining to distribution of the document or software without
+ * specific, written prior permission.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
+ * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
+ * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+/*
+ * Portions Copyright (c) 1996 by Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+struct __res_send_private {
+	int s;			/* socket used for communications */
+	int connected;		/* is the socket connected */
+	int vc;			/* is the socket a virtual circuit? */
+	int af;			/* address family of socket */
+	res_send_qhook Qhook;
+	res_send_rhook Rhook;
+};
+
+struct __res_send_private *___res_send_private(void);
diff --git a/lib/libc/net/resolver.3 b/lib/libc/net/resolver.3
index 7c5e7bb61d32..68d80d8eeb8a 100644
--- a/lib/libc/net/resolver.3
+++ b/lib/libc/net/resolver.3
@@ -396,6 +396,17 @@ function puts a 32-bit quantity
 .Fa src
 to a buffer pointed to by
 .Fa dst .
+.Sh RETURN VALUES
+The
+.Fn res_init
+function will return 0 on success, or -1 in a threaded program if
+per-thread storage could not be allocated.
+.Sh IMPLEMENTATION NOTES
+This implementation of the resolver is thread-safe, but it will not
+function properly if the programmer attempts to declare his or her own
+.Va _res
+structure in an attempt to replace the per-thread version referred to
+by that macro.
 .Sh FILES
 .Bl -tag -width /etc/resolv.conf
 .It Pa /etc/resolv.conf