BGP Confederation Internal ASN Filtering and is_bogon() Functionality in New BIRD Version

[Brandon Zhi]

Hi Maria,

Thanks for the reply

23.172.216.0/24      unicast [I_ZJ1 10:32:48.661 from 2a13:aac7:13:7::2] *
(100) [AS398741i]
        via 10.0.29.2 on CN-ZJ1
        Type: BGP univ
        BGP.origin: IGP
        BGP.as_path: 398741 60539 60539 (65000) 60539 398741
        BGP.next_hop: 10.0.29.2
        BGP.med: 101
        BGP.local_pref: 400
        BGP.large_community: (60539, 2, 1) (60539, 6, 65000) (60539, 6,
52000)

After I enabled is_bogon() function, this route from our downstream would
be filtered.

function is_bogon() {
   if is_bogon_asn() then return true;
   if is_bogon_prefix() then return true;
   if net_len_too_long() then return true;
   return false;
}


function bgp_export()
{
   # my_opt_prefix();
   if is_bogon() then return false; #关闭以防止过滤bgp conf的内部ASN
   if bgp_large_community ~ [(LOCAL_ASN, 4, NODE_ID)] then return false;
   if is_local_prefix()  then return true;
   # if proto = "BGP_Prefix_play" then return true;
   if source != RTS_BGP then return false;
   if bgp_large_community !~ [(LOCAL_ASN, 2, 1)] then return false;
   return true;
}

I always remember that in BIRD, BGP Confederation internal ASNs cannot be
counted in bgp_path.len. But BGP Confederation internal ASNs can be treated
as 'normal' ASNs for filtering?

Best,
*Brandon Zhi*
HUIZE LTD
www.huize.asia  <https://huize.asia/>| www.ixp.su | Twitter

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On Sat, 1 Jun 2024 at 22:36, Maria Matejka <maria.matejka at nic.cz> wrote:

> Hello Brandon,
>
> On Thu, May 30, 2024 at 09:52:53PM +0800, Brandon Zhi wrote:
>
> I am writing to inquire about the capabilities of the new version of BIRD
> regarding BGP Confederation internal ASNs. Specifically, I would like to
> know:
>
>    1. Can the new BIRD version filter BGP Confederation internal ASNs?
>    2. Does it support calculating the total AS path length, including
>    internal ASNs within a BGP Confederation?
>
> You are probably looking for something like bgp_path.filter() or
> bgp_path.len, or maybe for int p in bgp_path do { … }
>
> Additionally, I have encountered an issue while using the is_bogon()
> function. It currently filters a route with the AS path (65000) 398741. I
> suspect this is because (65000) is being treated as a BOGON ASN.
>
> Below is the define BOGON_ASNS I am using:
>
> define BOGON_ASNS = [
>     0,                      # RFC 7607
>     23456,                  # RFC 4893 AS_TRANS
>     64496..64511,           # RFC 5398 and documentation/example ASNs
>     64512..65534,           # RFC 6996 Private ASNs
>     65535,                  # RFC 7300 Last 16 bit ASN
>     65536..65551,           # RFC 5398 and documentation/example ASNs
>     65552..131071,          # RFC IANA reserved ASNs
>     4200000000..4294967294, # RFC 6996 Private ASNs
>     4294967295              # RFC 7300 Last 32 bit ASN
> ];
>
> Yes, this includes 65500. I can’t see your is_bogon() function definition
> though so I can’t help you more.
>
> Hoping that this helps.
>
> Maria
>
> – Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
>
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