netdev - Re: ip_gre headroom allocation

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Message-ID: <20090611113709.GA2545@gondor.apana.org.au>
Date:	Thu, 11 Jun 2009 21:37:09 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Timo Teräs <timo.teras@....fi>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kuznet@....inr.ac.ru
Subject: Re: ip_gre headroom allocation

On Thu, Jun 11, 2009 at 02:29:46PM +0300, Timo Teräs wrote:
>
> I guess this is easy for point-to-point tunnels. But how about the
> multipoint gre tunnels? The needed_headroom can vary on destination
> basis depending on if they are NATted or not, and on the cipher/hash
> used.

I don't think we need to worry about NAT, well at least we don't
worry about it on the normal path :)

> Can we change the needed_headroom on-the-fly? Increase it when ever
> we encounter a larger path? But this also means some packages would
> get extra headroom allocated.

Just make it the maximum.  It's OK to have extra head space.
If the head space is huge then you've got bigger problems than
wasted memory :)

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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