netdev - Re: [PATCH net-next 0/4] ila: Use NF_INET_PRE

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Message-ID: <20150928230010.GB19923@breakpoint.cc>
Date:	Tue, 29 Sep 2015 01:00:10 +0200
From:	Florian Westphal <fw@...len.de>
To:	Tom Herbert <tom@...bertland.com>
Cc:	Florian Westphal <fw@...len.de>,
	David Miller <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net-next 0/4] ila: Use NF_INET_PRE_ROUTING nfhook

Tom Herbert <tom@...bertland.com> wrote:
> RFC6296 doesn't work because it allows an invalid checksum to be sent
> on wire relative to the addresses used on the wire. That means we
> would lose CHECKSUM_UNNECESSARY for ILA which is way too big of a
> performance hit.

Not following.  I did not say you should use NPT instead of ILA.

[..]
> In any case, I did at one point create some netfilter targets for ILA
> to do the translation correctly updating the checksum. While this
> provided the required functionality, I couldn't get sufficient
> performance. A specialized fixed length lookup table gets most of the
> performance needed for ILA.

I'm not following at all.

Could you explain why you can't just 'relocate' your proposed
implementation to netfilter/ipv6?

F.e. I see no reason why you could not use a lookup table in a netfilter
target (or nft expression, for that matter) ... ?

Thanks,
Florian
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