Re: [PATCH 0/2] [RFC] Extended accounting infrastructure for iptables

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Dec 14, 2011 at 09:12:52PM +0800, Changli Gao wrote:
> On Wed, Dec 14, 2011 at 7:00 PM,  <pablo@netfilter.org> wrote:
> > From: Pablo Neira Ayuso <pablo@netfilter.org>
> >
> > Hi!
> >
> > We currently have two ways to account traffic in netfilter:
> >
> > - iptables chain and rule counters:
> >
> >  # iptables -L -n -v
> > Chain INPUT (policy DROP 3 packets, 867 bytes)
> >  pkts bytes target     prot opt in     out     source               destinat
> >    8  1104 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/
> >
> > - use flow-based accounting provided by ctnetlink:
> >
> >  # conntrack -L
> > tcp      6 431999 ESTABLISHED src=192.168.1.130 dst=212.106.219.168 sport=58
> >
> > While trying to display real-time accounting statistics, we require
> > to pool the kernel periodically to obtain this information. This is
> > OK if the number of flows is relatively low. However, in case that
> > the number of flows is huge, we can spend a considerable amount of
> > cycles to iterate over the list of flows that have been obtained.
> >
> > Moreover, if we want to obtain the sum of the flow accounting results
> > that match some criteria, we have to iterate over the whole list of
> > existing flows, look for matchings and update the counters.
> >
> > This patchset adds the extended accounting infrastructure in
> > kernel-space. It is composed of one nfnetlink interface that
> > allows you to create, to update and to retrieve accounting objects.
> > These objects can be used to account traffic with the flexibility
> > that iptables rules provide (by means of the new NFACCT target).
> >
> > Quick example of use:
> >
> > 1) You create the accounting object:
> >
> > libnetfilter_acct/examples# ./nfacct-add http-traffic
> >
> > 2) Add the iptables rules for traffic you want to account:
> >
> > # iptables -I INPUT -p tcp --sport 80 -j NFACCT --nfacct-name http-traffic
> > # iptables -I OUTPUT -p tcp --dport 80 -j NFACCT --nfacct-name http-traffic
> >
> 
> Why not use the counters of iptables instead?
> 
> iptables-save -c

If you want to obtain the sum of the counters that match some criteria,
you have to iterate over the whole list of existing rules, look for
matchings and update the counters.

Moreover, if you have a large rule-set, polling periodically
iptables-save -c can be expensive.
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