netdev - Re: [PATCH net-next 3/7] ipv6: improve ipv6_find

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Message-ID: <20121203180611.GA20305@1984>
Date:	Mon, 3 Dec 2012 19:06:11 +0100
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Jesse Gross <jesse@...ira.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	dev@...nvswitch.org, Ansis Atteka <aatteka@...ira.com>
Subject: Re: [PATCH net-next 3/7] ipv6: improve ipv6_find_hdr() to skip
 empty routing headers

On Mon, Dec 03, 2012 at 09:28:55AM -0800, Jesse Gross wrote:
> On Mon, Dec 3, 2012 at 6:04 AM, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > On Thu, Nov 29, 2012 at 10:35:45AM -0800, Jesse Gross wrote:
> >> @@ -159,9 +162,10 @@ int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
> >>       }
> >>       len = skb->len - start;
> >>
> >> -     while (nexthdr != target) {
> >
> > If the offset is set as parameter via ipv6_find_hdr, we now are always
> > entering the loop even if we found the target header we're looking
> > for, before that didn't happen.
> >
> > Something seems wrong here to me.
> 
> If the target header is a routing header then you might still need to
> continue searching because the first one that you see could be empty.

OK, but if it's not a routing header what we're searching for (which
seems to be the case of netfilter/IPVS) we waste way more cycles on
copying the IPv6 header again and with way more things that are
completely useless.
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