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>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index de0dc6bacbe8..b7889782047e 100644
--- a/net/8021q/vlan_dev.c
+++ b/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)) {