Handle SSL_ERROR_ZERO_RETURN in OpenSSL

It may be returned when the server closes the connection, see:
https://www.openssl.org/docs/manmaster/man3/SSL_get_error.html

We simply handle it as if there was no error and return zero bytes read.

Fixes: https://github.com/dillo-browser/dillo/issues/175

1 files changed, 3 insertions, 0 deletions

diff --git a/src/IO/tls_openssl.c b/src/IO/tls_openssl.c
index 90be78b7..3e53800d 100644
--- a/src/IO/tls_openssl.c
+++ b/src/IO/tls_openssl.c
@@ -1277,6 +1277,9 @@ static int Tls_handle_error(Conn_t *conn, int ret, const char *where)
    if (err1_ret == SSL_ERROR_NONE) {
       errno = 0;
       return ret;
+   } else if (err1_ret == SSL_ERROR_ZERO_RETURN) {
+      errno = 0;
+      return 0;
    } else if (err1_ret == SSL_ERROR_WANT_READ || err1_ret == SSL_ERROR_WANT_WRITE) {
       errno = EAGAIN;
       return -1;