diff --git a/libc/netbsd/net/reentrant.h b/libc/netbsd/net/reentrant.h
new file mode 100644
index 0000000..15507eb
--- /dev/null
+++ b/libc/netbsd/net/reentrant.h
@@ -0,0 +1,268 @@
+/*	$NetBSD: reentrant.h,v 1.10 2004/12/14 00:23:19 nathanw Exp $	*/
+
+/*-
+ * Copyright (c) 1997, 1998, 2003 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by J.T. Conklin, by Nathan J. Williams, and by Jason R. Thorpe.
+ *
+ * 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 NetBSD
+ *        Foundation, Inc. and its contributors.
+ * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
+ */
+
+/*
+ * Requirements:
+ * 
+ * 1. The thread safe mechanism should be lightweight so the library can
+ *    be used by non-threaded applications without unreasonable overhead.
+ * 
+ * 2. There should be no dependency on a thread engine for non-threaded
+ *    applications.
+ * 
+ * 3. There should be no dependency on any particular thread engine.
+ * 
+ * 4. The library should be able to be compiled without support for thread
+ *    safety.
+ * 
+ * 
+ * Rationale:
+ * 
+ * One approach for thread safety is to provide discrete versions of the
+ * library: one thread safe, the other not.  The disadvantage of this is
+ * that libc is rather large, and two copies of a library which are 99%+
+ * identical is not an efficent use of resources.
+ * 
+ * Another approach is to provide a single thread safe library.  However,
+ * it should not add significant run time or code size overhead to non-
+ * threaded applications.
+ * 
+ * Since the NetBSD C library is used in other projects, it should be
+ * easy to replace the mutual exclusion primitives with ones provided by
+ * another system.  Similarly, it should also be easy to remove all
+ * support for thread safety completely if the target environment does
+ * not support threads.
+ * 
+ * 
+ * Implementation Details:
+ * 
+ * The thread primitives used by the library (mutex_t, mutex_lock, etc.)
+ * are macros which expand to the cooresponding primitives provided by
+ * the thread engine or to nothing.  The latter is used so that code is
+ * not unreasonably cluttered with #ifdefs when all thread safe support
+ * is removed.
+ * 
+ * The thread macros can be directly mapped to the mutex primitives from
+ * pthreads, however it should be reasonably easy to wrap another mutex
+ * implementation so it presents a similar interface.
+ * 
+ * The thread functions operate by dispatching to symbols which are, by
+ * default, weak-aliased to no-op functions in thread-stub/thread-stub.c
+ * (some uses of thread operations are conditional on __isthreaded, but
+ * not all of them are).
+ *
+ * When the thread library is linked in, it provides strong-alias versions
+ * of those symbols which dispatch to its own real thread operations.
+ *
+ */
+
+#ifdef _REENTRANT
+
+/*
+ * Abtract thread interface for thread-safe libraries.  These routines
+ * will use stubs in libc if the application is not linked against the
+ * pthread library, and the real function in the pthread library if it
+ * is.
+ */
+
+#include <pthread.h>
+#include <signal.h>
+
+#define	mutex_t			pthread_mutex_t
+#define	MUTEX_INITIALIZER	PTHREAD_MUTEX_INITIALIZER
+
+#define	mutexattr_t		pthread_mutexattr_t
+
+#define	MUTEX_TYPE_NORMAL	PTHREAD_MUTEX_NORMAL
+#define	MUTEX_TYPE_ERRORCHECK	PTHREAD_MUTEX_ERRORCHECK
+#define	MUTEX_TYPE_RECURSIVE	PTHREAD_MUTEX_RECURSIVE
+
+#define	cond_t			pthread_cond_t
+#define	COND_INITIALIZER	PTHREAD_COND_INITIALIZER
+
+#define	condattr_t		pthread_condattr_t
+
+#define	rwlock_t		pthread_rwlock_t
+#define	RWLOCK_INITIALIZER	PTHREAD_RWLOCK_INITIALIZER
+
+#define	rwlockattr_t		pthread_rwlockattr_t
+
+#define	thread_key_t		pthread_key_t
+
+#define	thr_t			pthread_t
+
+#define	thrattr_t		pthread_attr_t
+
+#define	once_t			pthread_once_t
+#define	ONCE_INITIALIZER	PTHREAD_ONCE_INIT
+
+#ifndef __LIBC_THREAD_STUBS
+
+__BEGIN_DECLS
+int	__libc_mutex_init(mutex_t *, const mutexattr_t *);
+int	__libc_mutex_lock(mutex_t *);
+int	__libc_mutex_trylock(mutex_t *);
+int	__libc_mutex_unlock(mutex_t *);
+int	__libc_mutex_destroy(mutex_t *);
+
+int	__libc_mutexattr_init(mutexattr_t *);
+int	__libc_mutexattr_settype(mutexattr_t *, int);
+int	__libc_mutexattr_destroy(mutexattr_t *);
+__END_DECLS
+
+#define	mutex_init(m, a)	__libc_mutex_init((m), (a))
+#define	mutex_lock(m)		__libc_mutex_lock((m))
+#define	mutex_trylock(m)	__libc_mutex_trylock((m))
+#define	mutex_unlock(m)		__libc_mutex_unlock((m))
+#define	mutex_destroy(m)	__libc_mutex_destroy((m))
+
+#define	mutexattr_init(ma)	__libc_mutexattr_init((ma))
+#define	mutexattr_settype(ma, t) __libc_mutexattr_settype((ma), (t))
+#define	mutexattr_destroy(ma)	__libc_mutexattr_destroy((ma))
+
+__BEGIN_DECLS
+int	__libc_cond_init(cond_t *, const condattr_t *);
+int	__libc_cond_signal(cond_t *);
+int	__libc_cond_broadcast(cond_t *);
+int	__libc_cond_wait(cond_t *, mutex_t *);
+int	__libc_cond_timedwait(cond_t *, mutex_t *, const struct timespec *);
+int	__libc_cond_destroy(cond_t *);
+__END_DECLS
+
+#define	cond_init(c, t, a)     	__libc_cond_init((c), (a))
+#define	cond_signal(c)		__libc_cond_signal((c))
+#define	cond_broadcast(c)	__libc_cond_broadcast((c))
+#define	cond_wait(c, m)		__libc_cond_wait((c), (m))
+#define	cond_timedwait(c, m, t)	__libc_cond_timedwait((c), (m), (t))
+#define	cond_destroy(c)		__libc_cond_destroy((c))
+
+__BEGIN_DECLS
+int	__libc_rwlock_init(rwlock_t *, const rwlockattr_t *);
+int	__libc_rwlock_rdlock(rwlock_t *);
+int	__libc_rwlock_wrlock(rwlock_t *);
+int	__libc_rwlock_tryrdlock(rwlock_t *);
+int	__libc_rwlock_trywrlock(rwlock_t *);
+int	__libc_rwlock_unlock(rwlock_t *);
+int	__libc_rwlock_destroy(rwlock_t *);
+__END_DECLS
+
+#define	rwlock_init(l, a)	__libc_rwlock_init((l), (a))
+#define	rwlock_rdlock(l)	__libc_rwlock_rdlock((l))
+#define	rwlock_wrlock(l)	__libc_rwlock_wrlock((l))
+#define	rwlock_tryrdlock(l)	__libc_rwlock_tryrdlock((l))
+#define	rwlock_trywrlock(l)	__libc_rwlock_trywrlock((l))
+#define	rwlock_unlock(l)	__libc_rwlock_unlock((l))
+#define	rwlock_destroy(l)	__libc_rwlock_destroy((l))
+
+__BEGIN_DECLS
+int	__libc_thr_keycreate(thread_key_t *, void (*)(void *));
+int	__libc_thr_setspecific(thread_key_t, const void *);
+void	*__libc_thr_getspecific(thread_key_t);
+int	__libc_thr_keydelete(thread_key_t);
+__END_DECLS
+
+#define	thr_keycreate(k, d)	__libc_thr_keycreate((k), (d))
+#define	thr_setspecific(k, p)	__libc_thr_setspecific((k), (p))
+#define	thr_getspecific(k)	__libc_thr_getspecific((k))
+#define	thr_keydelete(k)	__libc_thr_keydelete((k))
+
+__BEGIN_DECLS
+int	__libc_thr_once(once_t *, void (*)(void));
+int	__libc_thr_sigsetmask(int, const sigset_t *, sigset_t *);
+thr_t	__libc_thr_self(void);
+int	__libc_thr_yield(void);
+void	__libc_thr_create(thr_t *, const thrattr_t *,
+	    void *(*)(void *), void *);
+void	__libc_thr_exit(void *) __attribute__((__noreturn__));
+int	*__libc_thr_errno(void);
+int	__libc_thr_setcancelstate(int, int *);
+
+extern int __isthreaded;
+__END_DECLS
+
+#define	thr_once(o, f)		__libc_thr_once((o), (f))
+#define	thr_sigsetmask(f, n, o)	__libc_thr_sigsetmask((f), (n), (o))
+#define	thr_self()		__libc_thr_self()
+#define	thr_yield()		__libc_thr_yield()
+#define	thr_create(tp, ta, f, a) __libc_thr_create((tp), (ta), (f), (a))
+#define	thr_exit(v)		__libc_thr_exit((v))
+#define	thr_errno()		__libc_thr_errno()
+#define	thr_enabled()		(__isthreaded)
+#define thr_setcancelstate(n, o) __libc_thr_setcancelstate((n),(o))
+#endif /* __LIBC_THREAD_STUBS */
+
+#define	FLOCKFILE(fp)		__flockfile_internal(fp, 1)
+#define	FUNLOCKFILE(fp)		__funlockfile_internal(fp, 1)
+
+#else /* _REENTRANT */
+
+#define	mutex_init(m, a)
+#define	mutex_lock(m)
+#define	mutex_trylock(m)
+#define	mutex_unlock(m)
+#define	mutex_destroy(m)
+
+#define	cond_init(c, t, a)
+#define	cond_signal(c)
+#define	cond_broadcast(c)
+#define	cond_wait(c, m)
+#define	cond_timedwait(c, m, t)
+#define	cond_destroy(c)
+
+#define	rwlock_init(l, a)
+#define	rwlock_rdlock(l)
+#define	rwlock_wrlock(l)
+#define	rwlock_tryrdlock(l)
+#define	rwlock_trywrlock(l)
+#define	rwlock_unlock(l)
+#define	rwlock_destroy(l)
+
+#define	thr_keycreate(k, d)
+#define	thr_setspecific(k, p)
+#define	thr_getspecific(k)
+#define	thr_keydelete(k)
+
+#define	thr_once(o, f)
+#define	thr_sigsetmask(f, n, o)
+#define	thr_self()
+#define	thr_errno()
+
+#define	FLOCKFILE(fp)		
+#define	FUNLOCKFILE(fp)		
+
+#endif /* _REENTRANT */