as-path flter problem

[Alexander Zubkov]

You can filter malformed pathes with something like:
! bgp_path ~ [= * 65001 * 65001 * =]
But the whole expression grows bigger and bigger. Regex-like matches
would be much easier of course.

On Fri, Jan 3, 2020 at 4:24 PM Marcelo Balbinot <marcelo at gegnet.com.br> wrote:
>
>
> Hi! Thanks for the sugestion...
>
> It works with this malformed path restriction.
>
> But I get the feeling of not being perfect! :)
>
> Regex for AS-PATH filters would be ideal!
>
> Or maybe a bgp_path.uniq method like bgp_path.last and bgp_path.first
>
> bgp_path.uniq could remove all repeated ASes. Then the if would be
> simple.
>
> []'s
>
> ---
> Marcelo Balbinot
> IP/MPLS Backbone Manager at AS53062
> G G NET Telecomunicações
> www.gegnet.com.br
> +55 49 3561 4300
> +55 49 9 9923 9347
> INOC 53062*100
>
> Em 2020-01-02 17:10, Alexander Zubkov escreveu:
> > Hi,
> >
> > Maybe something like this will work:
> > bgp_path ~ [= 65001 * =] && bgp_path ~ [= * 65001 65002 * =] &&
> > bgp_path ~ [= * 65002 65003 * =] && bgp_path ~ [= * 65003 =]
> > It will though pass some malformed pathes like 65001 65999 65001 65002
> > 65003.
> >
> > On Thu, Jan 2, 2020 at 2:36 PM Marcelo Balbinot <marcelo at gegnet.com.br>
> > wrote:
> >>
> >>
> >> Hello
> >> I'm having difficulty using as-path math expressions
> >>
> >> Look at my case.
> >> correct as-path: 65001 65002 65003
> >>
> >> I would like to validate if the as-path of the received prefix
> >> conforms
> >> to the as-path above. But, I would like to allow prepend of all ASes,
> >> so:
> >> 65001 65001 65002 65003 is valid
> >> 65001 65002 65002 65003 is valid
> >> 65001 65002 65003 65003 is valid
> >> 65001 65001 65002 65002 65002 65003 65003 is valid
> >> 65001 65999 65002 65003 is NOT valid
> >>
> >> The best expression I found was
> >> if (bgp_path ~ [= 65001* 65002* 65003* =]) then
> >>
> >> but it considers the path '65001 65999 65002 65003' to be valid
> >>
> >> With regex that would be easier, but with bird bgpmask I couldn't
> >> solve
> >> it.
> >>
> >> Any suggestion?
> >>
> >>
> >> --
> >> Marcelo Balbinot
> >> IP/MPLS Backbone Manager at AS53062
> >> G G NET Telecomunicações
> >> www.gegnet.com.br
> >> INOC 53062*100
> >>