Using as set a list of routes to advertise

[Ross Tajvar]

What are you using the prefix set for in the first place?

On Thu, May 11, 2023, 2:34 AM William <bird at is.unlawful.id.au> wrote:

> On 10/05/2023 19:46, Maria Matejka via Bird-users wrote:
> > Hello!
>
> Thanks for replying.
>
> > On 5/10/23 11:13, William wrote:
> >> Hi All,
> >> I've been digging around trying to find a nice way of doing it but
> >> can't seem to find a valid answer.
> >>
> >> Is there a way to use a prefix set to create static routes?
> >
> > No, this is not possible and implementing this would be surprisingly
> > difficult as the prefix sets are implemented as a compressed trie
> > optimized for fast lookup and not enumeration.
> >
> > Also imagine this:
> >
> >   define my_route_set = [ 2001:db8/32+ ]; # note the plus sign
> >   protocol static { ipv6; route my_route_set via 2001:db8::dead:beef; }
> >
> > This short code would generate approx. 7.9e28 routes.
>
> Yeah, that could hurt.
>
> >
> > If you could elaborate more precisely what you are trying to achieve
> > as a whole result, we may try to help you find how to do it in the way
> > BIRD is designed.
>
> We have a number of remote sites where there are non-dynamically routed
> downstream subnets that we need to add as static routes (anything from 1
> to 20+ per site) but also advertise upstream back into the WAN.
>
> Instead of specifying each prefix as an individual static route I was
> hoping to be able to use the existing prefix set to act as a list of
> routes to add.  If there was a way to iterate over the set in a loop
> fashion then that would suffice.  In our instance there aren't modifiers
> on the masks (no -'s, +'s or {minlen, maxlen}) hence the idea of being
> able to use the set as "just a list" - this could be a condition of
> using it for that function.
>
> For example (twist on my original):
>
> define my_route_set = [ 10.1.2.3/24, 172.20.4.2/24, 10.200.0.0/23 ];
>
> protocol static route_set {
>    ipv4 {
>      table Some_Routes;
>    }
>    for ThisRoute in my_route_set {
>      route ThisRoute via 192.168.55.2;    # downstream static gateway
>    }
>    route 5.6.7.8/32 via 192.168.55.1;
> }
>
> Resulting in:
> bird> sh route table Some_Routes
> Table Some_Routes:
> 10.1.2.3/24            unicast [route_set 2023-05-10] * (200)
>         via 192.168.55.2 on ens256
> 10.20.4.2/24           unicast [route_set 2023-05-10] * (200)
>         via 192.168.55.2 on ens256
> 10.200.0.0/23          unicast [route_set 2023-05-10] * (200)
>         via 192.168.55.2 on ens256
> 5.6.7.8/32             unicast [route_set 2023-05-10] * (200)
>         via 192.168.55.1 on ens256
> 192.168.55.0/24        unicast [Local_Ints 2023-05-10] * (240)
>         dev ens256
> bird>
>
> Hope that explains better what I'm hoping to achieve.  I couldn't see a
> way of doing it with if..then..else or case statements.  The only other
> option would be to have a script scrape the set out of the config and
> prepare an include file *shudder*.
>
> Regards,
> William
>
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