From 677f9754526a7923417fb70f9a8a38adaeb251a6 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@openwrt.org>
Date: Sun, 22 Jan 2012 19:00:04 +0100
Subject: [PATCH] save and restore previous device settings when overriding
 them via config

---
 device.h       |  1 +
 system-linux.c | 29 ++++++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/device.h b/device.h
index 12176ce..2b7fb13 100644
--- a/device.h
+++ b/device.h
@@ -112,6 +112,7 @@ struct device {
 
 	struct device_user parent;
 
+	struct device_settings orig_settings;
 	struct device_settings settings;
 };
 
diff --git a/system-linux.c b/system-linux.c
index 0ff2b3b..4fa0ead 100644
--- a/system-linux.c
+++ b/system-linux.c
@@ -569,6 +569,30 @@ int system_vlan_del(struct device *dev)
 	return system_vlan(dev, -1);
 }
 
+static void
+system_if_get_settings(struct device *dev, struct device_settings *s)
+{
+	struct ifreq ifr;
+
+	memset(&ifr, 0, sizeof(ifr));
+	strncpy(ifr.ifr_name, dev->ifname, sizeof(ifr.ifr_name));
+
+	if (ioctl(sock_ioctl, SIOCGIFMTU, &ifr) == 0) {
+		s->mtu = ifr.ifr_mtu;
+		s->flags |= DEV_OPT_MTU;
+	}
+
+	if (ioctl(sock_ioctl, SIOCGIFTXQLEN, &ifr) == 0) {
+		s->txqueuelen = ifr.ifr_qlen;
+		s->flags |= DEV_OPT_TXQUEUELEN;
+	}
+
+	if (ioctl(sock_ioctl, SIOCGIFHWADDR, &ifr) == 0) {
+		memcpy(s->macaddr, &ifr.ifr_hwaddr, sizeof(s->macaddr));
+		s->flags |= DEV_OPT_MACADDR;
+	}
+}
+
 static void
 system_if_apply_settings(struct device *dev, struct device_settings *s)
 {
@@ -592,6 +616,7 @@ system_if_apply_settings(struct device *dev, struct device_settings *s)
 
 int system_if_up(struct device *dev)
 {
+	system_if_get_settings(dev, &dev->orig_settings);
 	system_if_apply_settings(dev, &dev->settings);
 	dev->ifindex = system_if_resolve(dev);
 	return system_if_flags(dev->ifname, IFF_UP, 0);
@@ -599,7 +624,9 @@ int system_if_up(struct device *dev)
 
 int system_if_down(struct device *dev)
 {
-	return system_if_flags(dev->ifname, 0, IFF_UP);
+	int ret = system_if_flags(dev->ifname, 0, IFF_UP);
+	system_if_apply_settings(dev, &dev->orig_settings);
+	return ret;
 }
 
 int system_if_check(struct device *dev)
-- 
2.25.1