vlan: support "loose binding" to the underlying network device

Currently the UP/DOWN state of VLANs is synchronized to the state of the
underlying device, meaning all VLANs are set down once the underlying
device is set down. This causes all routes to the VLAN devices to vanish.

Add a flag to specify a "loose binding" mode, in which only the operstate
is transfered, but the VLAN device state is independant.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/if_vlan.h

@@ -339,6 +339,7 @@ enum vlan_ioctl_cmds {
 enum vlan_flags {
 	VLAN_FLAG_REORDER_HDR	= 0x1,
 	VLAN_FLAG_GVRP		= 0x2,
+	VLAN_FLAG_LOOSE_BINDING	= 0x4,
 };
 
 enum vlan_name_types {

net/8021q/vlan.c

@@ -431,6 +431,7 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
 	struct vlan_group *grp;
 	int i, flgs;
 	struct net_device *vlandev;
+	struct vlan_dev_info *vlan;
 	LIST_HEAD(list);
 
 	if (is_vlan_dev(dev))
@@ -507,7 +508,9 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
 			if (!(flgs & IFF_UP))
 				continue;
 
-			dev_change_flags(vlandev, flgs & ~IFF_UP);
+			vlan = vlan_dev_info(vlandev);
+			if (!(vlan->flags & VLAN_FLAG_LOOSE_BINDING))
+				dev_change_flags(vlandev, flgs & ~IFF_UP);
 			vlan_transfer_operstate(dev, vlandev);
 		}
 		break;
@@ -523,7 +526,9 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
 			if (flgs & IFF_UP)
 				continue;
 
-			dev_change_flags(vlandev, flgs | IFF_UP);
+			vlan = vlan_dev_info(vlandev);
+			if (!(vlan->flags & VLAN_FLAG_LOOSE_BINDING))
+				dev_change_flags(vlandev, flgs | IFF_UP);
 			vlan_transfer_operstate(dev, vlandev);
 		}
 		break;

net/8021q/vlan_dev.c

@@ -431,7 +431,8 @@ int vlan_dev_change_flags(const struct net_device *dev, u32 flags, u32 mask)
 	struct vlan_dev_info *vlan = vlan_dev_info(dev);
 	u32 old_flags = vlan->flags;
 
-	if (mask & ~(VLAN_FLAG_REORDER_HDR | VLAN_FLAG_GVRP))
+	if (mask & ~(VLAN_FLAG_REORDER_HDR | VLAN_FLAG_GVRP |
+		     VLAN_FLAG_LOOSE_BINDING))
 		return -EINVAL;
 
 	vlan->flags = (old_flags & ~mask) | (flags & mask);
@@ -456,7 +457,8 @@ static int vlan_dev_open(struct net_device *dev)
 	struct net_device *real_dev = vlan->real_dev;
 	int err;
 
-	if (!(real_dev->flags & IFF_UP))
+	if (!(real_dev->flags & IFF_UP) &&
+	    !(vlan->flags & VLAN_FLAG_LOOSE_BINDING))
 		return -ENETDOWN;
 
 	if (compare_ether_addr(dev->dev_addr, real_dev->dev_addr)) {

net/8021q/vlan_netlink.c

@@ -60,7 +60,8 @@ static int vlan_validate(struct nlattr *tb[], struct nlattr *data[])
 	if (data[IFLA_VLAN_FLAGS]) {
 		flags = nla_data(data[IFLA_VLAN_FLAGS]);
 		if ((flags->flags & flags->mask) &
-		    ~(VLAN_FLAG_REORDER_HDR | VLAN_FLAG_GVRP))
+		    ~(VLAN_FLAG_REORDER_HDR | VLAN_FLAG_GVRP |
+		      VLAN_FLAG_LOOSE_BINDING))
 			return -EINVAL;
 	}