On 02.08.2014 12:33, Alexander V. Chernikov wrote:
On 02.08.2014 10:33, Luigi Rizzo wrote:
On Fri, Aug 1, 2014 at 11:08 PM, Alexander V. Chernikov
<melif...@freebsd.org <mailto:melif...@freebsd.org>> wrote:
Hello all.
I'm currently working on to enhance ipfw in some areas.
The most notable (and user-visible) change is named table support.
The other one is support for different lookup algorithms for different
key types.
For example, new ipfw permits writing this:
ipfw table tb1 create type cidr
ipfw add allow ip from table(tl1) to any
ipfw add allow ip from any lookup dst-ip tb1
ipfw table if1 create type iface
ipfw add skipto tablearg ip from any to any via table(if1)
or even this:
ipfw table fl1 create type flow:src-ip,proto,dst-ip,dst-port
ipfw table fl1 add 10.0.0.5,tcp,10.0.0.6,80 4444
ipfw add allow ip from any to any flow table(fl1)
all these changes fully preserve backward compatibility.
(actually tables needs now to be created before use and their type needs
to match with opcode used, but new ipfw(8) performs auto-creation
for cidr tables).
There is another thing I'm going to change and I'm not sure I can keep
the same compatibility level.
Table values, from one point of view, can be classified to the following
types:
- skipto argument
- fwd argument (*)
- link to another object (nat, pipe, queue)
- plain u32 (not bound to any object)
(divert/tee,netgraph,tag/utag,limit)
There are the following reasons why I think it is necessary to implement
explicit table values typing (like tables):
- Implementing fwd tablearg for IPv6 hosts requires indirection table
- Converting nat/pipe instance ids to names renders values unusable
- retiring old hack with storing saved pointer of found object/rule
inside rule w/o proper locking
- making faster skipto
i don't buy the idea that you need typed arguments
for all the cases above. Maybe the case that
may make sense is the fwd argument (and in the future
something else).
We already discussed, i think, the fact that now it
is legal to have references to non existing things
(skipto, pipes etc.) implemented as u32.
Removing that would break configurations.
It depends on actual implementation. This can be preserved by
auto-creating necessary objects in kernel and/or in userspace, so
we can (and should) avoid breaking in this particular way.
Can you please explain your vision on values another time?
As far as I understand, you're not against it in general, but the
details matter:
* IP address can be one of the types (it won't break much, and we can
simply skip that one for MFC)
* what about typing for nat/pipes ? we're not going to convert their ids
to names? (or maybe you can suggest other non-disruptive way?)
* everything else is type "u32"
Efficiency is not affected, even for skipto,
It depends on workload. While binary search is fast in terms of cpu, it
is may be not so fast in terms of memory (since each of the rule is
allocated by separate malloc() (and that is another thing which is worth
discussing)).
and while i agree that unprotected writes to the pointers
in rules should not happen, these pointers are changed
infrequently so a global read-mostly lock should be
sufficient to protect all changes to the rules.
cheers
luigi
So, as the result, table will have lookup key type (already done),
value type ('skipto', 'nexthop', 'nat', 'pipe', 'number', ..) and some
additional restrictions (like inability to add non-existing nat instance
id).
This change will break (at least) scenarios where people are
using one table for both nat/pipe instances (and keep nat ids in sync
with pipe ones). For example:
ipfw table 1 add 10.0.10.0/24 <http://10.0.10.0/24> 110
ipfw table 1 add 10.0.20.0/24 <http://10.0.20.0/24> 120
ipfw add 100 nat tablearg from table(1) to any via vlanX in
..
ipfw add 500 pipe tablearg from table(1) to any via ix0 out
It looks like it is not so easy to bind values for given table to
different objects (or different tasks) (and lack of compatibility kills
hope for MFC).
Ideas?
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Prof. Luigi RIZZO, ri...@iet.unipi.it <mailto:ri...@iet.unipi.it> .
Dip. di Ing. dell'Informazione
http://www.iet.unipi.it/~luigi/ . Universita` di Pisa
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Mobile +39-338-6809875 <tel:%2B39-338-6809875> . 56122
PISA (Italy)
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