net: core: Always propagate flag changes to interfaces

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=d2615bf450694c1302d86b9cc8a8958edfe4c3a4
Commit:     d2615bf450694c1302d86b9cc8a8958edfe4c3a4
Parent:     dcdfdf56b4a6c9437fc37dbc9cee94a788f9b0c4
Author:     Vlad Yasevich <vyasevic at redhat.com>
AuthorDate: Tue Nov 19 20:47:15 2013 -0500
Committer:  David S. Miller <davem at davemloft.net>
CommitDate: Wed Nov 20 15:29:56 2013 -0500

    net: core: Always propagate flag changes to interfaces
    
    The following commit:
        b6c40d68ff6498b7f63ddf97cf0aa818d748dee7
        net: only invoke dev->change_rx_flags when device is UP
    
    tried to fix a problem with VLAN devices and promiscuouse flag setting.
    The issue was that VLAN device was setting a flag on an interface that
    was down, thus resulting in bad promiscuity count.
    This commit blocked flag propagation to any device that is currently
    down.
    
    A later commit:
        deede2fabe24e00bd7e246eb81cd5767dc6fcfc7
        vlan: Don't propagate flag changes on down interfaces
    
    fixed VLAN code to only propagate flags when the VLAN interface is up,
    thus fixing the same issue as above, only localized to VLAN.
    
    The problem we have now is that if we have create a complex stack
    involving multiple software devices like bridges, bonds, and vlans,
    then it is possible that the flags would not propagate properly to
    the physical devices.  A simple examle of the scenario is the
    following:
    
      eth0----> bond0 ----> bridge0 ---> vlan50
    
    If bond0 or eth0 happen to be down at the time bond0 is added to
    the bridge, then eth0 will never have promisc mode set which is
    currently required for operation as part of the bridge.  As a
    result, packets with vlan50 will be dropped by the interface.
    
    The only 2 devices that implement the special flag handling are
    VLAN and DSA and they both have required code to prevent incorrect
    flag propagation.  As a result we can remove the generic solution
    introduced in b6c40d68ff6498b7f63ddf97cf0aa818d748dee7 and leave
    it to the individual devices to decide whether they will block
    flag propagation or not.
    
    Reported-by: Stefan Priebe <s.priebe at profihost.ag>
    Suggested-by: Veaceslav Falico <vfalico at redhat.com>
    Signed-off-by: Vlad Yasevich <vyasevic at redhat.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
---
 net/core/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 7e00a73..ba3b7ea 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4996,7 +4996,7 @@ static void dev_change_rx_flags(struct net_device *dev, int flags)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
 
-	if ((dev->flags & IFF_UP) && ops->ndo_change_rx_flags)
+	if (ops->ndo_change_rx_flags)
 		ops->ndo_change_rx_flags(dev, flags);
 }