sandbox: eth: Add ARP and PING response to sandbox driver

The sandbox driver will now generate response traffic to exercise the
ping command even when no network exists.  This allows the basic data
pathways of the DM to be tested.

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

arch/sandbox/dts/sandbox.dts

@@ -204,5 +204,6 @@
 	eth@10002000 {
 		compatible = "sandbox,eth";
 		reg = <0x10002000 0x1000>;
+		fake-host-hwaddr = [00 00 66 44 22 00];
 	};
 };

drivers/net/sandbox.c

@@ -14,22 +14,128 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+/**
+ * struct eth_sandbox_priv - memory for sandbox mock driver
+ *
+ * fake_host_hwaddr: MAC address of mocked machine
+ * fake_host_ipaddr: IP address of mocked machine
+ * recv_packet_buffer: buffer of the packet returned as received
+ * recv_packet_length: length of the packet returned as received
+ */
+struct eth_sandbox_priv {
+	uchar fake_host_hwaddr[ARP_HLEN];
+	IPaddr_t fake_host_ipaddr;
+	uchar *recv_packet_buffer;
+	int recv_packet_length;
+};
+
 static int sb_eth_start(struct udevice *dev)
 {
+	struct eth_sandbox_priv *priv = dev_get_priv(dev);
+
 	debug("eth_sandbox: Start\n");
 
+	fdtdec_get_byte_array(gd->fdt_blob, dev->of_offset, "fake-host-hwaddr",
+			      priv->fake_host_hwaddr, ARP_HLEN);
+	priv->recv_packet_buffer = net_rx_packets[0];
 	return 0;
 }
 
 static int sb_eth_send(struct udevice *dev, void *packet, int length)
 {
+	struct eth_sandbox_priv *priv = dev_get_priv(dev);
+	struct ethernet_hdr *eth = packet;
+
 	debug("eth_sandbox: Send packet %d\n", length);
 
+	if (ntohs(eth->et_protlen) == PROT_ARP) {
+		struct arp_hdr *arp = packet + ETHER_HDR_SIZE;
+
+		if (ntohs(arp->ar_op) == ARPOP_REQUEST) {
+			struct ethernet_hdr *eth_recv;
+			struct arp_hdr *arp_recv;
+
+			/* store this as the assumed IP of the fake host */
+			priv->fake_host_ipaddr = NetReadIP(&arp->ar_tpa);
+			/* Formulate a fake response */
+			eth_recv = (void *)priv->recv_packet_buffer;
+			memcpy(eth_recv->et_dest, eth->et_src, ARP_HLEN);
+			memcpy(eth_recv->et_src, priv->fake_host_hwaddr,
+			       ARP_HLEN);
+			eth_recv->et_protlen = htons(PROT_ARP);
+
+			arp_recv = (void *)priv->recv_packet_buffer +
+				ETHER_HDR_SIZE;
+			arp_recv->ar_hrd = htons(ARP_ETHER);
+			arp_recv->ar_pro = htons(PROT_IP);
+			arp_recv->ar_hln = ARP_HLEN;
+			arp_recv->ar_pln = ARP_PLEN;
+			arp_recv->ar_op = htons(ARPOP_REPLY);
+			memcpy(&arp_recv->ar_sha, priv->fake_host_hwaddr,
+			       ARP_HLEN);
+			NetWriteIP(&arp_recv->ar_spa, priv->fake_host_ipaddr);
+			memcpy(&arp_recv->ar_tha, &arp->ar_sha, ARP_HLEN);
+			NetCopyIP(&arp_recv->ar_tpa, &arp->ar_spa);
+
+			priv->recv_packet_length = ETHER_HDR_SIZE +
+				ARP_HDR_SIZE;
+		}
+	} else if (ntohs(eth->et_protlen) == PROT_IP) {
+		struct ip_udp_hdr *ip = packet + ETHER_HDR_SIZE;
+
+		if (ip->ip_p == IPPROTO_ICMP) {
+			struct icmp_hdr *icmp = (struct icmp_hdr *)&ip->udp_src;
+
+			if (icmp->type == ICMP_ECHO_REQUEST) {
+				struct ethernet_hdr *eth_recv;
+				struct ip_udp_hdr *ipr;
+				struct icmp_hdr *icmpr;
+
+				/* reply to the ping */
+				memcpy(priv->recv_packet_buffer, packet,
+				       length);
+				eth_recv = (void *)priv->recv_packet_buffer;
+				ipr = (void *)priv->recv_packet_buffer +
+					ETHER_HDR_SIZE;
+				icmpr = (struct icmp_hdr *)&ipr->udp_src;
+				memcpy(eth_recv->et_dest, eth->et_src,
+				       ARP_HLEN);
+				memcpy(eth_recv->et_src, priv->fake_host_hwaddr,
+				       ARP_HLEN);
+				ipr->ip_sum = 0;
+				ipr->ip_off = 0;
+				NetCopyIP((void *)&ipr->ip_dst, &ip->ip_src);
+				NetWriteIP((void *)&ipr->ip_src,
+					   priv->fake_host_ipaddr);
+				ipr->ip_sum = compute_ip_checksum(ipr,
+					IP_HDR_SIZE);
+
+				icmpr->type = ICMP_ECHO_REPLY;
+				icmpr->checksum = 0;
+				icmpr->checksum = compute_ip_checksum(icmpr,
+					ICMP_HDR_SIZE);
+
+				priv->recv_packet_length = length;
+			}
+		}
+	}
+
 	return 0;
 }
 
 static int sb_eth_recv(struct udevice *dev, uchar **packetp)
 {
+	struct eth_sandbox_priv *priv = dev_get_priv(dev);
+
+	if (priv->recv_packet_length) {
+		int lcl_recv_packet_length = priv->recv_packet_length;
+
+		debug("eth_sandbox: received packet %d\n",
+		      priv->recv_packet_length);
+		priv->recv_packet_length = 0;
+		*packetp = priv->recv_packet_buffer;
+		return lcl_recv_packet_length;
+	}
 	return 0;
 }
 
@@ -80,5 +186,6 @@ U_BOOT_DRIVER(eth_sandbox) = {
 	.ofdata_to_platdata = sb_eth_ofdata_to_platdata,
 	.remove	= sb_eth_remove,
 	.ops	= &sb_eth_ops,
+	.priv_auto_alloc_size = sizeof(struct eth_sandbox_priv),
 	.platdata_auto_alloc_size = sizeof(struct eth_pdata),
 };

include/configs/sandbox.h

@@ -130,6 +130,7 @@
 /* include default commands */
 #include <config_cmd_default.h>
 
+#define CONFIG_CMD_PING
 
 #define CONFIG_CMD_HASH
 #define CONFIG_HASH_VERIFY