Messages in this thread | | | Date | Mon, 20 Sep 2010 19:08:37 +0200 | From | Patrick McHardy <> | Subject | Re: [PATCH v5 2/2] netfilter: save the hash of the tuple in the original direction for latter use |
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On 20.09.2010 17:04, Changli Gao wrote: > On Thu, Sep 16, 2010 at 2:18 PM, Patrick McHardy <kaber@trash.net> wrote: >> On 21.08.2010 00:49, Changli Gao wrote: >>> Since we don't change the tuple in the original direction, we can save it >>> in ct->tuplehash[IP_CT_DIR_REPLY].hnode.pprev for __nf_conntrack_confirm() >>> use. >> >> I like this idea. We could actually do the same for the reply tuple >> and invalidate the saved hash in case the reply tuple is changed >> (nf_conntrack_alter_reply()), which only happens when NAT is used. >> > > We can't do that, as the unconfirmed ct owned maybe dropped, and > pre-computing will wast CPU cycles in this case.
Sure we can, dropping unconfirmed conntracks is a rare exception, not a common case. Even under DoS we usually drop *unassured* conntracks, which have already enterered the hash. If we're unable to do that, we won't even allocate a new conntrack.
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