From b61979a9e590c2aa8eabf563c9e154c9be33069c Mon Sep 17 00:00:00 2001
From: Viktor Dukhovni <postfix-users@dukhovni.org>
Date: Thu, 14 May 2020 23:12:04 -0400
Subject: [PATCH] Flush the OpenSSL error queue before each BIO op.

---
 postfix/src/tls/tls_bio_ops.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/postfix/src/tls/tls_bio_ops.c b/postfix/src/tls/tls_bio_ops.c
index 93d3535d7..39818f815 100644
--- a/postfix/src/tls/tls_bio_ops.c
+++ b/postfix/src/tls/tls_bio_ops.c
@@ -196,6 +196,12 @@ int     tls_bio(int fd, int timeout, TLS_SESS_STATE *TLScontext,
      * handling any pending network I/O.
      */
     for (;;) {
+        /*
+         * Flush stale data from SSL error queue, stale errors can confuse
+         * SSL_get_error().
+         */
+        ERR_clear_error();
+
 	if (hsfunc)
 	    status = hsfunc(TLScontext->con);
 	else if (rfunc)
-- 
2.47.3