Re: [PATCH net-next] ipv4: tcp: dont cache unconfirmed intput dst

[Eric Dumazet <eric.dumazet@xxxxxxxxx>]

On Wed, 2012-06-27 at 17:08 -0700, David Miller wrote:
> From: David Miller <davem@xxxxxxxxxxxxx>
> Date: Wed, 27 Jun 2012 17:01:01 -0700 (PDT)
> 
> > There are quite a number of unwanted side effects from this change, so
> > I think we'll have to revert unless you can fix up all of the relevant
> > cases quickly.
> 
> Actually I've decided to revert it now.
> 
> Whilst this was a swell idea, there is no way for you to know if
> we should really create a cached route or not.
> 
> Even if you could, there is a lot of logic you'll need to code up
> so that, f.e., once we determine that we've got a DST_NOCACHE route
> when we move to established state, we can insert it into the routing
> cache and not mark it DST_NOCACHE any longer.
> 
> But even if we did that, we're going to eat 2 uncached route lookups
> for every new incoming legitimate connection.

The initial idea was to perform this only for SYN packets received on a
listener in SYNCOOKIE mode. I'll resend the patch when fully
implemented, instead of a forward patch.

Thanks


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