RFC 5575 question: is Destination Prefix mendatory?

[Alarig Le Lay]

Hi,

it seems that for bird, the flowspec destination prefix is mentatory. I
have a session with an exabgp and if I send this
	echo 'announce flow route { match { source 213.167.241.55/32; destination 0.0.0.0/0; } then { discard; } }' > /var/run/exabgp.cmd
It works, I have the route:

	bird> show route all table flowtab4
	Table flowtab4:
	flow4 { dst 0.0.0.0/0; src 213.167.241.55/32; }  [bgp_wfiltr1_ipv4 15:44:14.440 from 217.70.176.118] * (100) [i]
		Type: BGP univ
		BGP.origin: IGP
		BGP.as_path:
		BGP.local_pref: 100
		BGP.ext_community: (generic, 0x80060000, 0x0)

But, if I send this:
	echo 'announce flow route { match { source 213.167.241.55/32; } then { discard; } }' > /var/run/exabgp.cmd
It doesn’t work, the session is in error state (BGP Error: Malformed
attribute list) and the log says "Invalid flow route: Destination prefix
is missing".

However, https://tools.ietf.org/html/rfc5575#section-4 says
   We define a "Flow Specification" NLRI type that may include several
   components such as destination prefix, source prefix, protocol,
   ports, etc.  This NLRI is treated as an opaque bit string prefix by
   BGP.  Each bit string identifies a key to a database entry with which
   a set of attributes can be associated.

As it’s “may”, I would say that it’s not mendatory. The sessions toward
ASR9K routers accept the annoucement.

Regards,
-- 
Alarig