IPFW missing feature

[Lowell Gilbert]

KES <kes-kes at yandex.ru> writes:

> Здравствуйте, Lowell.
>
> Вы писали 16 апреля 2009 г., 15:22:31:
>
> LG> KES <kes-kes at yandex.ru> writes:
>
>>>      The tablearg feature provides the ability to use a value, looked up in
>>>      the table, as the argument for a rule action, action parameter or rule
>>>      option.  This can significantly reduce number of rules in some configura-
>>>      tions.  If two tables are used in a rule, the result of the second (des-
>>>      tination) is used.  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.
>>>
>>>
>>> Why tablearg cannot be used with setfib?
>
> LG> Because tables are a feature of IPFW, and the FIB isn't.
>
> setfib is also feature of ipfw. see man:
>
>      setfib fibnum
>              The packet is tagged so as to use the FIB (routing table) fibnum
>              in any subsequent forwarding decisions. Initially this is limited
>              to the values  0 through 15. See setfib(8).  Processing continues
>              at the next rule.
>
> There is no any difficulties to use 'tablearg' as 'fibnum'
>
> ipfw add 3 setfib 2 all from 192.168.0.0/16 to any in recv <IFACE>
> ipfw add 3 setfib tablearg all from table(<X>) to any in recv <IFACE>
>
> but now this is not mistake to write 'setfib tablearg'. IPFW just replace tablearg in rule with 0
> It seems like a bug. because of it MUST work in proper way or DO NOT
> work at all. IMHO

This does not make sense to me.  What do you expect the "tablearg" to be
in the second line you listed?  That keyword is used to apply the output
of an ipfw table lookup, and you haven't used an ipfw table before that
line.  If you want table(<X>) to give back a fib to use, then you need
to do that lookup before you do a setfib action.

On the other hand, I don't see any point in doing that, because there
can only be one result for a given address in your table(<X>), so
there's no reason to have more than one FIB.

-- 
Lowell Gilbert, embedded/networking software engineer, Boston area
		http://be-well.ilk.org/~lowell/