Loop in AS macro

Hi, Shane,

  Thank for the tip. It works.

Ping Lu
Cable & Wireless USA
Network Tools and Analysis Group
W: +1-703-292-2359
E: plu at cw.net


> -----Original Message-----
> From: Shane Kerr [mailto:shane at ripe.net]
> Sent: Thursday, January 11, 2001 4:46 AM
> To: Lu, Ping
> Cc: 'cengiz at packetdesign.com'; Wilfried Woeber, UniVie/ACOnet;
> farrache at cc.in2p3.fr; db-wg at ripe.net; routing-wg at ripe.net;
> Henk.Uijterwaal at ripe.net
> Subject: RE: Loop in AS macro
> 
> 
> Ping,
> 
> What I usually do (in Perl) is something like this:
> 
> my %entries_seen;
> foreach my $as_set (@as_sets) {
>     # if we've seen this value (recursive as-set), skip
>     next if ($entries_seen{$as_set});
> 
>     # note that we've seen this as-set
>     $entries_seen{$as_set}++;
> 
>     # get a list of members of the as-set, and process appropriately
>     foreach my $member (members($as_set)) {
>         # add member as-sets to the list of as-sets to process
>         push(@as_sets, $member) if ($member =~ /^AS-/i);
> 
>         # other processing here
>           .
>           .
>           .
>     }
> }
> 
> If you're using some other scripting language, it will be 
> different, but
> typically no more difficult.  If you're in C, you may want to 
> use glib or
> something like that, otherwise you'll need to use a list or 
> hash you write
> yourself.
> 
> Shane Kerr <shane at ripe.net>
> Database Software Engineer
> RIPE NCC
> +31 20 535 4427
> 
> On Wed, 10 Jan 2001, Lu, Ping wrote:
> 
> > Hi, I am new to this list and would like to ask a (maybe 
> stupid) question to
> > the dicussion:
> > 
> > If we want to write a script to expand the AS MACRO, how 
> can we avoid to go
> > into a loop if multiple AS-MACROs reference each other ?
> > 
> > Ping Lu
> > Cable & Wireless USA
> > Network Tools and Analysis Group
> > W: 703-292-2359
> > E: plu at cw.net
> > 
> > > -----Original Message-----
> > > From: Cengiz Alaettinoglu [mailto:cengiz at packetdesign.com]
> > > Sent: Wednesday, January 10, 2001 12:14 PM
> > > To: Shane Kerr
> > > Cc: Wilfried Woeber, UniVie/ACOnet; farrache at cc.in2p3.fr;
> > > db-wg at ripe.net; routing-wg at ripe.net; Henk.Uijterwaal at ripe.net
> > > Subject: RE: Loop in AS macro
> > > 
> > > 
> > > 
> > > Shane Kerr (shane at ripe.net) on January 10:
> > > > Gilles, Wilfried, and all,
> > > > 
> > > > This is not a bug, or even an inconsistency.  Consider 
> the following
> > > > as-macro objects:
> > > > 
> > > >   as-macro: AS-X
> > > >   members:  AS-Y, AS123
> > > > 
> > > >   as-macro: AS-Y
> > > >   members:  AS-X, AS456, AS789
> > > > 
> > > > In this case, AS-X and AS-Y both expand to the same 
> aut-num objects:
> > > > AS123, AS456, and AS789.  However, they may have different 
> > > maintainers,
> > > > contacts, descriptions, and so on.  In RPSL, many more 
> > > kinds of loops are
> > > > possible as well, in as-set, route-set, and filter-set objects.
> > > 
> > > RPSL defines semantics when loops exist. However, it does 
> not promote
> > > them, or prohibit additional restrictions by the registry 
> operators
> > > not to have loops.
> > > 
> > > > 
> > > > External software that deals with the set objects needs 
> to do loop
> > > > detection in order to prevent infinite loops.  For as-set 
> > > objects (which
> > > > are as-macro objects in RIPE-181), this is fairly easy:  
> > > keep a list or
> > > > hash of the AS sets expanded, and don't expand them again.  
> > > For route-set
> > > > and filter-set objects it is not quite so easy.  If you 
> > > need help with
> > > > these, you can send me and e-mail and I can explain the 
> > > techniques that
> > > > I've used for these objects.
> > > > 
> > > > Shane Kerr <shane at ripe.net>
> > > > Database Software Engineer
> > > > RIPE NCC
> > > > +31 20 535 4427
> > > > 
> > > > p.s.  This is actually a feature, not an bug.  :)
> > > > 
> > > > p.p.s.  It has been argued (by me) that RPSL allows 
> objects that are
> > > > logically impossible, but the RFC authors don't seem to 
> think so!
> > > > 
> > > > On Wed, 10 Jan 2001, Wilfried Woeber, UniVie/ACOnet wrote:
> > > > 
> > > > >   Hi Gilles,
> > > > >   
> > > > >   I guess we wouldn't be able to check against those 
> > > accidents at the time
> > > > >   of a DB _update_...
> > > > >   
> > > > >   But checking the RR internal _data_ consistency could 
> > > maybe become part
> > > > >   of the RIS (or similar) project?
> > > > >   
> > > > >   Henk, any comments?
> > > > >   
> > > > >   An interesting aside: I guess similar problems 
> could occur with
> > > > >   RPSL-based RRs?
> > > > >   
> > > > >   -WW
> > > > >  
> > > _________________________________:____________________________
> > > _________
> > > > >   Wilfried Woeber                 : e-mail: 
> Woeber at CC.UniVie.ac.at
> > > > >   UniVie Computer Center - ACOnet : Tel: +43 1 4277 - 140 33
> > > > >   Universitaetsstrasse 7          : Fax: +43 1 4277 - 9 140
> > > > >   A-1010 Vienna, Austria, Europe  : RIPE-DB: WW144, PGP 
> > > keyID 0xF0ACB369
> > > > >  
> > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > ~~~~~~~~~
> > > > > 
> > > > > To: staff at ip.tele.dk, peering at tli.de, ip-oper at tli.de, 
> > > admin-c at tli.de
> > > > > CC: farrache at cc.in2p3.fr, db-wg at ripe.net, routing-wg at ripe.net
> > > > > Subject: Loop in AS macro
> > > > > Date: Wed, 10 Jan 2001 10:28:15 +0100
> > > > > From: Gilles Farrache <farrache at cc.in2p3.fr>
> > > > > 
> > > > > Dear database managers,
> > > > > 
> > > > > I notice a loop in the followings AS-MACRO, in fact  
> > > AS-TELEDANMARKINTERNATIONAL
> > > > > is calling AS-TLI which is calling AS-TELEDK which is 
> > > calling AS-TELEDANMARKINTERNATIONAL.
> > > > > (and all that make that our automatic filter generation 
> > > tool fails)
> > > > > 
> > > > > Could you correct those macro and will the Ripe database 
> > > management provide any 
> > > > > control on that kind of loop ?
> > > > > 
> > > > > Gilles 
> > > > > 
> > > > > as-macro:    AS-TELEDANMARKINTERNATIONAL
> > > > > descr:       Tele Danmark customers outside Denmark
> > > > > as-list:     AS1902 AS12461
> > > > > as-list:     AS8881 AS-KOMTEL
> > > > > as-list:     AS13194 AS-BITE
> > > > > as-list:     AS6709
> > > > > as-list:     AS8650 AS-TLI
> > > > > as-list:     AS8542
> > > > > as-list:     AS12294 AS-TSUA AS6807 AS8349 AS12788 
> > > AS12837 AS12872 AS13249 AS15386 AS15497 AS15929 AS16007
> > > > > as-list:     AS12546
> > > > > as-list:     AS15389
> > > > > tech-c:      AS5071-RIPE
> > > > > admin-c:     AS5071-RIPE
> > > > > notify:      staff at ip.tele.dk
> > > > > notify:      peering at tli.de
> > > > > mnt-by:      AS3292-MNT
> > > > > changed:     jesper at skriver.dk 20001103
> > > > > changed:     toba at tdk.dk 20001117
> > > > > changed:     tee at tdk.dk 20001123
> > > > > changed:     jesper at skriver.dk 20001228
> > > > > changed:     jesper at skriver.dk 20010109
> > > > > source:      RIPE
> > > > > 
> > > > > as-macro:    AS-TLI
> > > > > descr:       Talkline GmbH, Internet Division
> > > > > descr:       List of ASes according to Talkline 
> Internet (AS8650)
> > > > > descr:       and customers
> > > > > as-list:     AS5605
> > > > > as-list:     AS6783
> > > > > as-list:     AS8650
> > > > > as-list:     AS8881
> > > > > as-list:     AS12461
> > > > > as-list:     AS12546
> > > > > as-list:     AS-TELEDK
> > > > > as-list:     AS-GLOBAL
> > > > > tech-c:      TLIP1-RIPE
> > > > > admin-c:     TLIP1-RIPE
> > > > > notify:      peering at tli.de
> > > > > mnt-by:      TALKLINE-MNT
> > > > > changed:     thomas at tli.de 19990923
> > > > > changed:     thomas at tli.de 19991020
> > > > > changed:     thomas at tli.de 19991025
> > > > > changed:     thomas at tli.de 20001023
> > > > > changed:     thomas at tli.de 20001025
> > > > > source:      RIPE
> > > > > 
> > > > > as-macro:    AS-TELEDK
> > > > > descr:       Tele Danmark and Tele Danmark customers
> > > > > as-list:     AS-TELEDANMARKDANISH
> > > > > as-list:     AS-TELEDANMARKINTERNATIONAL
> > > > > as-list:     AS-BELBONEMEMBERS
> > > > > as-list:     AS-GLOBAL
> > > > > tech-c:      AS5071-RIPE
> > > > > admin-c:     AS5071-RIPE
> > > > > notify:      staff at ip.tele.dk
> > > > > notify:      peering at tli.de
> > > > > mnt-by:      AS3292-MNT
> > > > > changed:     jesper at skriver.dk 19990922
> > > > > changed:     jesper at skriver.dk 19991019
> > > > > changed:     jesper at skriver.dk 19991025
> > > > > changed:     jesper at skriver.dk 19991210
> > > > > changed:     toba at tdk.dk 20000903
> > > > > source:      RIPE
> > > > > 
> > > --------------------------------------------------------------
> > > ------------------
> > > > > 
> > > > 
> > > > 
> > > 
> > > 
> > > Cengiz
> > > 
> > > -- 
> > > Cengiz Alaettinoglu           Packet Design Inc.
> > > 
> > > 
> > 
>