sandbox: eth-raw: Allow interface to be specified by index

With systemd stable interface names, eth0 will almost never exist.
Instead of using that name in the sandbox.dts, use an index.

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

arch/sandbox/cpu/eth-raw-os.c

@@ -44,6 +44,13 @@ out:
 	return ret;
 }
 
+int sandbox_eth_raw_os_idx_to_name(struct eth_sandbox_raw_priv *priv)
+{
+	if (!if_indextoname(priv->host_ifindex, priv->host_ifname))
+		return -errno;
+	return 0;
+}
+
 static int _raw_packet_start(struct eth_sandbox_raw_priv *priv,
 			     unsigned char *ethmac)
 {

arch/sandbox/include/asm/eth-raw-os.h

@@ -42,6 +42,15 @@ struct eth_sandbox_raw_priv {
  */
 int sandbox_eth_raw_os_is_local(const char *ifname);
 
+/*
+ * Look up the name of the interface based on the ifindex populated in priv.
+ *
+ * Overwrite the host_ifname member in priv based on looking up host_ifindex
+ *
+ * returns - 0 if success, negative if error
+ */
+int sandbox_eth_raw_os_idx_to_name(struct eth_sandbox_raw_priv *priv);
+
 int sandbox_eth_raw_os_start(struct eth_sandbox_raw_priv *priv,
 			     unsigned char *ethmac);
 int sandbox_eth_raw_os_send(void *packet, int length,

drivers/net/sandbox-raw.c

@@ -143,6 +143,7 @@ static int sb_eth_raw_ofdata_to_platdata(struct udevice *dev)
 	struct eth_sandbox_raw_priv *priv = dev_get_priv(dev);
 	const char *ifname;
 	u32 local;
+	int ret;
 
 	pdata->iobase = dev_read_addr(dev);
 
@@ -151,6 +152,16 @@ static int sb_eth_raw_ofdata_to_platdata(struct udevice *dev)
 		strncpy(priv->host_ifname, ifname, IFNAMSIZ);
 		printf(": Using %s from DT\n", priv->host_ifname);
 	}
+	if (dev_read_u32(dev, "host-raw-interface-idx",
+			 &priv->host_ifindex) < 0) {
+		priv->host_ifindex = 0;
+	} else {
+		ret = sandbox_eth_raw_os_idx_to_name(priv);
+		if (ret < 0)
+			return ret;
+		printf(": Using interface index %d from DT (%s)\n",
+		       priv->host_ifindex, priv->host_ifname);
+	}
 
 	local = sandbox_eth_raw_os_is_local(priv->host_ifname);
 	if (local < 0)