ipfw rule processing performances

[Ian Smith]

On Wed, 26 Oct 2011, Julian Elischer wrote:
 > On 10/26/11 2:39 PM, Michael Sierchio wrote:
 > > On Wed, Oct 26, 2011 at 11:39 AM, Julian Elischer<julian at freebsd.org>
 > > wrote:
 > > 
 > > > read up on all the things you can do with tablearg.. sometimes a single
 > > > table can replace dozens of rules.
 > > Julian - would you be so kind as to give an example?
 > > 
 > > - M
 > > 
 > off the top of my head:
 > 
 > implement an ad-hoc RErouting table using   fwd  tablearg
 > implement entirely differnt rules for a complicated set of subnets using
 > skipto tablearg

But in this context, isn't skipto tablearg time-expensive, in that it 
can't use the cached target of a normal skipto, but must to walk the 
ruleset from the skipto to the resulting rule each time?

 > arbitrarily slow down all the traffic from everyone you don't like in the
 > company using "lookup" and queue.
 > 
 > from the man page:
 > 
 >       The tablearg argument can be used with the following
 >      actions: nat, pipe, queue, divert, tee, netgraph, ngtee, fwd, skipto
 >      action parameters: tag, untag, rule options: limit, tagged.
 > 
 > and...
 > 
 >           # addresses we don't want to be seeing coming from outside..
 >         ${fwcmd} table 1 add 10.0.0.0/8
 >         ${fwcmd} table 1 add 172.16.0.0/12
 >         ${fwcmd} table 1 add 192.168.0.0/16
 >          # Stop draft-manning-dsua-03.txt (1 May 2000) nets (includes
 >          # RESERVED-1, DHCP auto-configuration, NET-TEST, MULTICAST (class
 > D),
 >          # and class E) on the outside interface
 >         ${fwcmd} table 1 add 0.0.0.0/8
 >         ${fwcmd} table 1 add 169.254.0.0/16
 >         ${fwcmd} table 1 add 192.0.2.0/24
 >         ${fwcmd} table 1 add 224.0.0.0/4
 >         ${fwcmd} table 1 add 240.0.0.0/4

Indeed, I was entirely bemused by the arguments against incorporating 
this into rc.firewall a year or two ago ..

cheers, Ian