From 327ef305304df23d10851ea1906e996a4f1bce56 Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Thu, 10 Feb 2022 23:50:35 +0100
Subject: [PATCH] wolfssl: when SSL_read() returns zero, check the error

Returning zero indicates end of connection, so if there's no data read
but the connection is alive, it needs to return -1 with CURLE_AGAIN.

Closes #8431
---
 lib/vtls/wolfssl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/vtls/wolfssl.c b/lib/vtls/wolfssl.c
index 314279dd13..d44a406b53 100644
--- a/lib/vtls/wolfssl.c
+++ b/lib/vtls/wolfssl.c
@@ -917,7 +917,7 @@ static ssize_t wolfssl_recv(struct Curl_easy *data,
 
   nread = SSL_read(backend->handle, buf, buffsize);
 
-  if(nread < 0) {
+  if(nread <= 0) {
     int err = SSL_get_error(backend->handle, nread);
 
     switch(err) {