netdev - Re: Can ndo_select_queue save data in skb->cb?

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Message-ID: <1415211391.13896.10.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 05 Nov 2014 10:16:31 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	James Yonan <james@...nvpn.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: Can ndo_select_queue save data in skb->cb?

On Wed, 2014-11-05 at 10:57 -0700, James Yonan wrote:
> Is it permissible for a net driver's ndo_select_queue method to save 
> data in skb->cb for later use in ndo_start_xmit?
> 
> Also, is it necessary for users of skb->cb to zero out their private 
> data after use to prevent it from being misinterpreted by other layers? 
>   I noticed some commits in the log (such as 462fb2) are zeroing out the 
> skb->cb area for this reason.

Its ok to use skb->cb[] from ndo_select_queue()

Look at bond_select_queue() for such a case.

You do not need to cleanup skb->cb[] to zero before giving skb to the
driver.

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