netdev - Re: tun: Use netif_receive_skb instead of netif

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Message-ID: <20100520052059.GC7443@gondor.apana.org.au>
Date:	Thu, 20 May 2010 15:20:59 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, bmb@...enacr.com,
	tgraf@...hat.com, nhorman@...driver.com, nhorman@...hat.com,
	netdev@...r.kernel.org
Subject: Re: tun: Use netif_receive_skb instead of netif_rx

On Thu, May 20, 2010 at 07:15:07AM +0200, Eric Dumazet wrote:
> 
> I find this very biased, sorry.
> 
> In fact, fd passing is just fine today, if we consider that we classify
> packets using the identity of the process *using* the fd, not the one
> that *created* it.
> 
> Now your patch changes this, to the reverse, and you justify the caching
> effect on socket. Sorry, this must be too convoluted for me.

I'm sorry you find this convoluted, but using the sending process's
classid is inherently broken.

Here is why: consider a TCP socket shared by two processes with
different classids both writing data to it.  Now suppose further
that each writes just one byte, which is then coalesced into a
single skb.

Whose classid should we use on the resulting skb?

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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