diff --git a/bufferevent_pair.c b/bufferevent_pair.c
new file mode 100644
index 0000000..e9ed9f5
--- /dev/null
+++ b/bufferevent_pair.c
@@ -0,0 +1,334 @@
+/*
+ * Copyright (c) 2009-2012 Niels Provos, 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 <sys/types.h>
+
+#ifdef WIN32
+#include <winsock2.h>
+#endif
+
+#include "event2/event-config.h"
+
+#include "event2/util.h"
+#include "event2/buffer.h"
+#include "event2/bufferevent.h"
+#include "event2/bufferevent_struct.h"
+#include "event2/event.h"
+#include "defer-internal.h"
+#include "bufferevent-internal.h"
+#include "mm-internal.h"
+#include "util-internal.h"
+
+struct bufferevent_pair {
+	struct bufferevent_private bev;
+	struct bufferevent_pair *partner;
+};
+
+
+/* Given a bufferevent that's really a bev part of a bufferevent_pair,
+ * return that bufferevent_filtered. Returns NULL otherwise.*/
+static inline struct bufferevent_pair *
+upcast(struct bufferevent *bev)
+{
+	struct bufferevent_pair *bev_p;
+	if (bev->be_ops != &bufferevent_ops_pair)
+		return NULL;
+	bev_p = EVUTIL_UPCAST(bev, struct bufferevent_pair, bev.bev);
+	EVUTIL_ASSERT(bev_p->bev.bev.be_ops == &bufferevent_ops_pair);
+	return bev_p;
+}
+
+#define downcast(bev_pair) (&(bev_pair)->bev.bev)
+
+static inline void
+incref_and_lock(struct bufferevent *b)
+{
+	struct bufferevent_pair *bevp;
+	_bufferevent_incref_and_lock(b);
+	bevp = upcast(b);
+	if (bevp->partner)
+		_bufferevent_incref_and_lock(downcast(bevp->partner));
+}
+
+static inline void
+decref_and_unlock(struct bufferevent *b)
+{
+	struct bufferevent_pair *bevp = upcast(b);
+	if (bevp->partner)
+		_bufferevent_decref_and_unlock(downcast(bevp->partner));
+	_bufferevent_decref_and_unlock(b);
+}
+
+/* XXX Handle close */
+
+static void be_pair_outbuf_cb(struct evbuffer *,
+    const struct evbuffer_cb_info *, void *);
+
+static struct bufferevent_pair *
+bufferevent_pair_elt_new(struct event_base *base,
+    int options)
+{
+	struct bufferevent_pair *bufev;
+	if (! (bufev = mm_calloc(1, sizeof(struct bufferevent_pair))))
+		return NULL;
+	if (bufferevent_init_common(&bufev->bev, base, &bufferevent_ops_pair,
+		options)) {
+		mm_free(bufev);
+		return NULL;
+	}
+	if (!evbuffer_add_cb(bufev->bev.bev.output, be_pair_outbuf_cb, bufev)) {
+		bufferevent_free(downcast(bufev));
+		return NULL;
+	}
+
+	_bufferevent_init_generic_timeout_cbs(&bufev->bev.bev);
+
+	return bufev;
+}
+
+int
+bufferevent_pair_new(struct event_base *base, int options,
+    struct bufferevent *pair[2])
+{
+	struct bufferevent_pair *bufev1 = NULL, *bufev2 = NULL;
+	int tmp_options;
+
+	options |= BEV_OPT_DEFER_CALLBACKS;
+	tmp_options = options & ~BEV_OPT_THREADSAFE;
+
+	bufev1 = bufferevent_pair_elt_new(base, options);
+	if (!bufev1)
+		return -1;
+	bufev2 = bufferevent_pair_elt_new(base, tmp_options);
+	if (!bufev2) {
+		bufferevent_free(downcast(bufev1));
+		return -1;
+	}
+
+	if (options & BEV_OPT_THREADSAFE) {
+		/*XXXX check return */
+		bufferevent_enable_locking(downcast(bufev2), bufev1->bev.lock);
+	}
+
+	bufev1->partner = bufev2;
+	bufev2->partner = bufev1;
+
+	evbuffer_freeze(downcast(bufev1)->input, 0);
+	evbuffer_freeze(downcast(bufev1)->output, 1);
+	evbuffer_freeze(downcast(bufev2)->input, 0);
+	evbuffer_freeze(downcast(bufev2)->output, 1);
+
+	pair[0] = downcast(bufev1);
+	pair[1] = downcast(bufev2);
+
+	return 0;
+}
+
+static void
+be_pair_transfer(struct bufferevent *src, struct bufferevent *dst,
+    int ignore_wm)
+{
+	size_t src_size, dst_size;
+	size_t n;
+
+	evbuffer_unfreeze(src->output, 1);
+	evbuffer_unfreeze(dst->input, 0);
+
+	if (dst->wm_read.high) {
+		dst_size = evbuffer_get_length(dst->input);
+		if (dst_size < dst->wm_read.high) {
+			n = dst->wm_read.high - dst_size;
+			evbuffer_remove_buffer(src->output, dst->input, n);
+		} else {
+			if (!ignore_wm)
+				goto done;
+			n = evbuffer_get_length(src->output);
+			evbuffer_add_buffer(dst->input, src->output);
+		}
+	} else {
+		n = evbuffer_get_length(src->output);
+		evbuffer_add_buffer(dst->input, src->output);
+	}
+
+	if (n) {
+		BEV_RESET_GENERIC_READ_TIMEOUT(dst);
+
+		if (evbuffer_get_length(dst->output))
+			BEV_RESET_GENERIC_WRITE_TIMEOUT(dst);
+		else
+			BEV_DEL_GENERIC_WRITE_TIMEOUT(dst);
+	}
+
+	src_size = evbuffer_get_length(src->output);
+	dst_size = evbuffer_get_length(dst->input);
+
+	if (dst_size >= dst->wm_read.low) {
+		_bufferevent_run_readcb(dst);
+	}
+	if (src_size <= src->wm_write.low) {
+		_bufferevent_run_writecb(src);
+	}
+done:
+	evbuffer_freeze(src->output, 1);
+	evbuffer_freeze(dst->input, 0);
+}
+
+static inline int
+be_pair_wants_to_talk(struct bufferevent_pair *src,
+    struct bufferevent_pair *dst)
+{
+	return (downcast(src)->enabled & EV_WRITE) &&
+	    (downcast(dst)->enabled & EV_READ) &&
+	    !dst->bev.read_suspended &&
+	    evbuffer_get_length(downcast(src)->output);
+}
+
+static void
+be_pair_outbuf_cb(struct evbuffer *outbuf,
+    const struct evbuffer_cb_info *info, void *arg)
+{
+	struct bufferevent_pair *bev_pair = arg;
+	struct bufferevent_pair *partner = bev_pair->partner;
+
+	incref_and_lock(downcast(bev_pair));
+
+	if (info->n_added > info->n_deleted && partner) {
+		/* We got more data.  If the other side's reading, then
+		   hand it over. */
+		if (be_pair_wants_to_talk(bev_pair, partner)) {
+			be_pair_transfer(downcast(bev_pair), downcast(partner), 0);
+		}
+	}
+
+	decref_and_unlock(downcast(bev_pair));
+}
+
+static int
+be_pair_enable(struct bufferevent *bufev, short events)
+{
+	struct bufferevent_pair *bev_p = upcast(bufev);
+	struct bufferevent_pair *partner = bev_p->partner;
+
+	incref_and_lock(bufev);
+
+	if (events & EV_READ) {
+		BEV_RESET_GENERIC_READ_TIMEOUT(bufev);
+	}
+	if ((events & EV_WRITE) && evbuffer_get_length(bufev->output))
+		BEV_RESET_GENERIC_WRITE_TIMEOUT(bufev);
+
+	/* We're starting to read! Does the other side have anything to write?*/
+	if ((events & EV_READ) && partner &&
+	    be_pair_wants_to_talk(partner, bev_p)) {
+		be_pair_transfer(downcast(partner), bufev, 0);
+	}
+	/* We're starting to write! Does the other side want to read? */
+	if ((events & EV_WRITE) && partner &&
+	    be_pair_wants_to_talk(bev_p, partner)) {
+		be_pair_transfer(bufev, downcast(partner), 0);
+	}
+	decref_and_unlock(bufev);
+	return 0;
+}
+
+static int
+be_pair_disable(struct bufferevent *bev, short events)
+{
+	if (events & EV_READ) {
+		BEV_DEL_GENERIC_READ_TIMEOUT(bev);
+	}
+	if (events & EV_WRITE)
+		BEV_DEL_GENERIC_WRITE_TIMEOUT(bev);
+	return 0;
+}
+
+static void
+be_pair_destruct(struct bufferevent *bev)
+{
+	struct bufferevent_pair *bev_p = upcast(bev);
+
+	if (bev_p->partner) {
+		bev_p->partner->partner = NULL;
+		bev_p->partner = NULL;
+	}
+
+	_bufferevent_del_generic_timeout_cbs(bev);
+}
+
+static int
+be_pair_flush(struct bufferevent *bev, short iotype,
+    enum bufferevent_flush_mode mode)
+{
+	struct bufferevent_pair *bev_p = upcast(bev);
+	struct bufferevent *partner;
+	incref_and_lock(bev);
+	if (!bev_p->partner)
+		return -1;
+
+	partner = downcast(bev_p->partner);
+
+	if (mode == BEV_NORMAL)
+		return 0;
+
+	if ((iotype & EV_READ) != 0)
+		be_pair_transfer(partner, bev, 1);
+
+	if ((iotype & EV_WRITE) != 0)
+		be_pair_transfer(bev, partner, 1);
+
+	if (mode == BEV_FINISHED) {
+		_bufferevent_run_eventcb(partner, iotype|BEV_EVENT_EOF);
+	}
+	decref_and_unlock(bev);
+	return 0;
+}
+
+struct bufferevent *
+bufferevent_pair_get_partner(struct bufferevent *bev)
+{
+	struct bufferevent_pair *bev_p;
+	struct bufferevent *partner = NULL;
+	bev_p = upcast(bev);
+	if (! bev_p)
+		return NULL;
+
+	incref_and_lock(bev);
+	if (bev_p->partner)
+		partner = downcast(bev_p->partner);
+	decref_and_unlock(bev);
+	return partner;
+}
+
+const struct bufferevent_ops bufferevent_ops_pair = {
+	"pair_elt",
+	evutil_offsetof(struct bufferevent_pair, bev.bev),
+	be_pair_enable,
+	be_pair_disable,
+	be_pair_destruct,
+	_bufferevent_generic_adj_timeouts,
+	be_pair_flush,
+	NULL, /* ctrl */
+};