From ab877e64d0580feaac3a510b11f553c6d10b0013 Mon Sep 17 00:00:00 2001
From: Mark Johnston <markj@FreeBSD.org>
Date: Wed, 19 Jun 2019 16:09:20 +0000
Subject: [PATCH] Make zlib encoding messages idempotent.

Otherwise duplicate messages can trigger a reinitialization of the
compression stream while the update thread is running.  Also ensure
that the stream is initialized before the update thread may attempt
to use it.

PR:		238333
Reviewed by:	cem, rgrimes
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D20673
---
 usr.sbin/bhyve/rfb.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/usr.sbin/bhyve/rfb.c b/usr.sbin/bhyve/rfb.c
index d572037b25fe..0a0538f80e53 100644
--- a/usr.sbin/bhyve/rfb.c
+++ b/usr.sbin/bhyve/rfb.c
@@ -273,8 +273,10 @@ rfb_recv_set_encodings_msg(struct rfb_softc *rc, int cfd)
 			rc->enc_raw_ok = true;
 			break;
 		case RFB_ENCODING_ZLIB:
-			rc->enc_zlib_ok = true;
-			deflateInit(&rc->zstream, Z_BEST_SPEED);
+			if (!rc->enc_zlib_ok) {
+				deflateInit(&rc->zstream, Z_BEST_SPEED);
+				rc->enc_zlib_ok = true;
+			}
 			break;
 		case RFB_ENCODING_RESIZE:
 			rc->enc_resize_ok = true;