Re: [UDP6]: Restore sk_filter optimisation
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: 2007-10-31 14:43:31
On Wed, Oct 31, 2007 at 11:05:45PM +0900, Mitsuru Chinen wrote:
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1. udp6InDatagrams is incremented instead of udpInErrors 2. In userland, recvfrom() replies an error with EAGAIN. recvfrom() wasn't aware of such a packet before. Are these changes intentional?As far as I tested, this doesn't happen with the old code even if a filter is attached. However, this happen with the new code without a filter and I don't see this rather when a filter is attached. So, I'm afraid it's new.
Sorry, I read the patch the wrong way around :) 1) is just an accounting issue. It shouldn't be too difficult to fix it up. In fact, I think udpInErrors will still be incremented once we detect the error. 2) shouldn't be an issue because we've already solved the problem by making poll/select do the checksum verification before indiciating that the socket is readable.
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And, we're not sure how much the "optimization"'s benefit is. It is even worse when we are hand
The checksum verification is costly because we have to bring the payload into cache. Since filters are very rare it's worthwhile to postpone the checksum verification for the common case. Also as a general rule, we want to avoid divergent behaviour between IPv4 and IPv6. So for changes like this we should really modify both stacks in future rather than have each stack do its own thing. Thanks, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} [off-list ref] Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt