sandbox: eth-raw: Add a function to ask the host about localhost

Instead of doing a simple string compare against "lo", look for the flag
that indicates a localhost interface.

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

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

@@ -1,9 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2015 National Instruments
- *
- * (C) Copyright 2015
- * Joe Hershberger <joe.hershberger@ni.com>
+ * Copyright (c) 2015-2018 National Instruments
+ * Copyright (c) 2015-2018 Joe Hershberger <joe.hershberger@ni.com>
  */
 
 #include <asm/eth-raw-os.h>
@@ -25,6 +23,27 @@
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 
+int sandbox_eth_raw_os_is_local(const char *ifname)
+{
+	int fd = socket(AF_INET, SOCK_DGRAM, 0);
+	struct ifreq ifr;
+	int ret = 0;
+
+	if (fd < 0)
+		return -errno;
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
+	ret = ioctl(fd, SIOCGIFFLAGS, &ifr);
+	if (ret < 0) {
+		ret = -errno;
+		goto out;
+	}
+	ret = !!(ifr.ifr_flags & IFF_LOOPBACK);
+out:
+	close(fd);
+	return ret;
+}
+
 static int _raw_packet_start(struct eth_sandbox_raw_priv *priv,
 			     unsigned char *ethmac)
 {

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

@@ -34,6 +34,14 @@ struct eth_sandbox_raw_priv {
 	unsigned short local_bind_udp_port;
 };
 
+/*
+ * Check if the interface named "ifname" is a localhost interface or not.
+ * ifname - the interface name on the host to check
+ *
+ * returns - 0 if real interface, 1 if local, negative if error
+ */
+int sandbox_eth_raw_os_is_local(const char *ifname);
+
 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

@@ -29,6 +29,8 @@ static int sb_eth_raw_start(struct udevice *dev)
 	if (priv->local) {
 		env_set("ipaddr", "127.0.0.1");
 		env_set("serverip", "127.0.0.1");
+		net_ip = string_to_ip("127.0.0.1");
+		net_server_ip = net_ip;
 	}
 	return ret;
 }
@@ -140,6 +142,7 @@ static int sb_eth_raw_ofdata_to_platdata(struct udevice *dev)
 	struct eth_pdata *pdata = dev_get_platdata(dev);
 	struct eth_sandbox_raw_priv *priv = dev_get_priv(dev);
 	const char *ifname;
+	u32 local;
 
 	pdata->iobase = dev_read_addr(dev);
 
@@ -147,10 +150,13 @@ static int sb_eth_raw_ofdata_to_platdata(struct udevice *dev)
 	if (ifname) {
 		strncpy(priv->host_ifname, ifname, IFNAMSIZ);
 		printf(": Using %s from DT\n", priv->host_ifname);
-		if (strcmp(ifname, "lo") == 0)
-			priv->local = 1;
 	}
 
+	local = sandbox_eth_raw_os_is_local(priv->host_ifname);
+	if (local < 0)
+		return local;
+	priv->local = local;
+
 	return 0;
 }