netdev - Re: [PATCHv3] net: core: Always propagate flag changes to interfaces

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Message-ID: <528C62F7.2000100@profihost.ag>
Date:	Wed, 20 Nov 2013 08:21:27 +0100
From:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
To:	Vlad Yasevich <vyasevic@...hat.com>, netdev@...r.kernel.org
CC:	vfalico@...hat.com
Subject: Re: [PATCHv3] net: core: Always propagate flag changes to interfaces

Hi,

Am 20.11.2013 02:47, schrieb Vlad Yasevich:
> 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@...fihost.ag>
> Suggested-by: Veaceslav Falico <vfalico@...hat.com>
> Signed-off-by: Vlad Yasevich <vyasevic@...hat.com>
> ---
> v2->v3:  Removed a strange chunk that modified comments.  Not sure where it
>          came from.
> 
>  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 974143d..da9c5e1 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4991,7 +4991,7 @@ 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);
>  }

thanks for this patch - in one of the first posts you send this one:

diff --git a/net/core/dev.c b/net/core/dev.c
index fc913f4..016857b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4525,7 +4525,9 @@ 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 (((dev->flags & IFF_UP) ||
+            (dev->flags & (IFF_MASTER | IFF_SLAVE)))
+           && ops->ndo_change_rx_flags)
                ops->ndo_change_rx_flags(dev, flags);
 }

-- 
1.8.4.2

why the differences? The one you send first works fine - have not tried v3.

Greets,
Stefan
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