sandbox: eth: Add ability to disable ping reply in sandbox eth driver

This is needed to test the netretry functionality (make the command fail
on a sandbox eth device).

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/include/asm/eth.h

+/*
+ * Copyright (c) 2015 National Instruments
+ *
+ * (C) Copyright 2015
+ * Joe Hershberger <joe.hershberger@ni.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#ifndef __ETH_H
+#define __ETH_H
+
+void sandbox_eth_disable_response(int index, bool disable);
+
+#endif /* __ETH_H */

drivers/net/sandbox.c

@@ -29,6 +29,19 @@ struct eth_sandbox_priv {
 	int recv_packet_length;
 };
 
+static bool disabled[8] = {false};
+
+/*
+ * sandbox_eth_disable_response()
+ *
+ * index - The alias index (also DM seq number)
+ * disable - If non-zero, ignore sent packets and don't send mock response
+ */
+void sandbox_eth_disable_response(int index, bool disable)
+{
+	disabled[index] = disable;
+}
+
 static int sb_eth_start(struct udevice *dev)
 {
 	struct eth_sandbox_priv *priv = dev_get_priv(dev);
@@ -48,6 +61,10 @@ static int sb_eth_send(struct udevice *dev, void *packet, int length)
 
 	debug("eth_sandbox: Send packet %d\n", length);
 
+	if (dev->seq >= 0 && dev->seq < ARRAY_SIZE(disabled) &&
+	    disabled[dev->seq])
+		return 0;
+
 	if (ntohs(eth->et_protlen) == PROT_ARP) {
 		struct arp_hdr *arp = packet + ETHER_HDR_SIZE;