Re: iwlwifi and tx info in skb->cb

[Johannes Berg <johannes@sipsolutions.net>]

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On Fri, 2008-05-09 at 01:17 +0200, Johannes Berg wrote:
> > >  That's not really related to wireless at all, if you want to do
> > >  zero-copy IO then you need to checksum when the stuff hits the wire
> > >  which means out of hardware buffers, which some hardware (including
> > >  802.11) doesn't support so you need to copy, nothing wireless specific
> > >  here :)
> > >
> > 
> > The FCS/CRS checksum of the wireless packet is performed in the HW but
> > why should I care about IP layer?
> 
> Because the data you're sending is sent via TCP?

Basically, it boils down to this:

If you want to checksum the data in software then you need to checksum a
snapshot of the data and not allow the application to modify it after
you have checksummed it, so you need to make a copy and then checksum it
after copying. But if you're making a copy anyway, you can put it all
into one buffer too.

johannes

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