Hello there,
I am currently working on my thesis and experimenting with the BIRD routing
daemon. As part of my work, I added a new optional transitive BGP path
attribute using the following configuration line:
attribute bgp 200 bytestring new_attribute;
The attribute appears correctly in the routing table as follows: (birdc show
route all)
192.168.5.0/24 unicast [router5 15:00:40.321] * (100) [AS5i]
via 10.0.51.5 on eth2
Type: BGP univ
BGP.origin: IGP
BGP.as_path: 5
BGP.next_hop: 10.0.51.5
BGP.local_pref: 100
BGP.c8 [t]: 20
And this is the way I declare it in my bird.conf file:
filter export_with_new_attribute {
new_attribute = hex:20;
accept;
}
But now I would like to use it as part of traffic engineering decisions.
Specifically, I would like to understand what steps are required in order to
make this new attribute influence the BGP decision-making process for choosing
the best path to route the traffic.
Could you please advise:
1.
Which files and functions in the BIRD source code are responsible for the BGP
path selection process that I need to edit to make my new attribute come after
LOCAL_PREF attribute in the priority list? Or if there is a way to do this
without the need to edit the source code.
2.
Are the previous things correct to add a custom path attribute that is doing
something?
3.
Why is it displaying like this: BGP.c8 [t]: 20? Is there a way to make it
appear like this: BGP.new_attribute [t]: 20?
4.
Is there a standard or recommended way to extend BIRD so that a custom
attribute can be incorporated into route preference / best path selection, and
if I want to compare 2 values and choose the lowest path that has this value?
I would greatly appreciate any pointers or guidance that could help me move
forward because I did not find any clues on that in your documentation.
Thank you very much for your time and support.
Best regards,
Yazan.
