Crude fix for libtls issue #266

tls_changes.diff

--- tls/tls.c	2017-01-25 18:20:41.087748566 +0000
+++ /home/vinay/tmp/tls.c	2017-01-29 08:26:00.343170297 +0000
@@ -635,6 +635,21 @@
 	return (rv);
 }
 
+static BOOL
+socket_is_valid(SOCKET fd)
+{
+	fd_set fds;
+	int rc;
+	TIMEVAL t;
+
+	ZeroMemory(&fds, sizeof(fds));
+	t.tv_sec = t.tv_usec = 0;
+	fds.fd_count = 1;
+	fds.fd_array[0] = fd;
+	rc = select(1, &fds, &fds, &fds, &t);
+	return rc >= 0;
+}
+
 int
 tls_close(struct tls *ctx)
 {
@@ -651,12 +666,14 @@
 
 	if (ctx->ssl_conn != NULL) {
 		ERR_clear_error();
-		ssl_ret = SSL_shutdown(ctx->ssl_conn);
-		if (ssl_ret < 0) {
-			rv = tls_ssl_error(ctx, ctx->ssl_conn, ssl_ret,
-			    "shutdown");
-			if (rv == TLS_WANT_POLLIN || rv == TLS_WANT_POLLOUT)
-				goto out;
+		if (socket_is_valid(ctx->ssl_conn->wbio->num)) {
+			ssl_ret = SSL_shutdown(ctx->ssl_conn);
+			if (ssl_ret < 0) {
+				rv = tls_ssl_error(ctx, ctx->ssl_conn, ssl_ret,
+					"shutdown");
+				if (rv == TLS_WANT_POLLIN || rv == TLS_WANT_POLLOUT)
+					goto out;
+			}
 		}
 	}