netdev - Re: (Lack of) specification for RX n-tuple filtering

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Date:	Wed, 8 Dec 2010 19:31:32 +0200
From:	"Vladislav Zolotarov" <vladz@...adcom.com>
To:	"David Miller" <davem@...emloft.net>
cc:	"bhutchings@...arflare.com" <bhutchings@...arflare.com>,
	"dm@...lsio.com" <dm@...lsio.com>,
	"peter.p.waskiewicz.jr@...el.com" <peter.p.waskiewicz.jr@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: (Lack of) specification for RX n-tuple filtering

> > I also agree with Dimitris: what we have here is an offload of some
> > Netfilter functionality to HW. Regardless the HW implementation (TCAM or
> > not) if it's allowed to configure more than one rule for the same
> > protocol the ordering of filtering rules is important: for instance if u
> > change the order of applying the rules in the example below the result
> > of the filtering for the traffic with both VLAN 4 and destination port
> > 3000 will be different.
> 
> It's not the same, this whole ordering thing you expect in netfilter
> land is simply not present in these hardware implementations.
> 
> The hardware does a parallel TCAM match lookup, and whatever matches
> is used.

So, u say that in scope of a single protocol all rules create a set
which ordering is a vendor specific and the same configuration of
n-tuple rules may generate different results for the same traffic on
NICs from different vendors? Don't u think it's confusing from the user
point of view? ;)




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