From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Ahern <dsa@cumulusnetworks.com>
Subject: Re: Increasing skb->mark size
Date: Tue, 1 Dec 2015 21:42:45 -0800
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Cc: Lorenzo Colitti <lorenzo@google.com>,
	Matt Bennett <Matt.Bennett@alliedtelesis.co.nz>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Luuk Paulussen <Luuk.Paulussen@alliedtelesis.co.nz>,
	davem@davemloft.net
To: Andi Kleen <andi@firstfloor.org>,
	Daniel Borkmann <daniel@iogearbox.net>
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On 12/1/15 6:58 PM, Andi Kleen wrote:
>>> - skb_iff is either skb->dev->iff or 0. so it could be replaced with a
>>> single bit flag for the 0 case.
>>
>> ... and that one wouldn't work on ingress.
>
> Please explain.

skb->dev is dropped fairly early in the Rx path. skb_iif is needed for 
example for IP_CMSG_PKTINFO.