netdev - Re: [PATCH net-next RESEND] net: Do not call ndo_dflt_fdb_dump if ndo_fdb

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Date:	Fri, 19 Dec 2014 15:17:31 +0000
From:	Hubert Sokolowski <hubert.sokolowski@...el.com>
To:	Jamal Hadi Salim <jhs@...atatu.com>, vyasevic@...hat.com
CC:	John Fastabend <john.fastabend@...il.com>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next RESEND] net: Do not call ndo_dflt_fdb_dump if
 ndo_fdb_dump is defined.

On 18/12/14 22:32, Jamal Hadi Salim wrote:

> Sorry for the latency (head-buried-in-sand in effect)
> On 12/17/14 11:18, Hubert Sokolowski wrote:
>> I have just prepared a patch where I dump uc/mc for bridge devices
>> by looking at (dev->priv_flags & IFF_EBRIDGE), so I have same results
>> as without my changes. This should satisfy Jamal and Roopa.
>> I could send it as v3 of my patch along with the results if you are
>> interested.
> Please do. If you satisfy Vlad's goals then we are all happy.

Posted as v3, please review.
There is still open question I asked sometime ago but never got explained.
It is about the new filter_dev parameter that was added to ndo_fdb_dump:
        int                     (*ndo_fdb_dump)(struct sk_buff *skb,
                                                struct netlink_callback *cb,
                                                struct net_device *dev,
                                                struct net_device *filter_dev,
                                                int idx);

When we call this function for a device, dev pointer is passed as the filter_dev:
                if (dev->netdev_ops->ndo_fdb_dump)
                        idx = dev->netdev_ops->ndo_fdb_dump(skb, cb, bdev, dev,
                                                            idx);

This is not an issue for a bridge device and a device that is not enslaved
in a bridge because bdev == dev, but this can be dangerous in other cases.
Let's assume QLogic NIC has a master device, in this case bdev != dev.
Now look what is happening, dev is passed as filter_dev to:
static int qlcnic_fdb_dump(struct sk_buff *skb, struct netlink_callback *ncb,
                        struct net_device *netdev,
                        struct net_device *filter_dev, int idx)
{
        struct qlcnic_adapter *adapter = netdev_priv(netdev);
...

netdev_priv(netdev) returns a pointer to private struct of the bridge,but the driver
is expecting it's own private stuff.

Should we fix the driver and assume filter_dev is /me and dev is our master
or the parameters were reversed and should be passed as (skb, cb, dev, bdev, idx) ?
Is this something for another patch/discussion?

regards,
Hubert

-- 
Hubert Sokolowski          Intel Corporation

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