print BGP AGGREGATOR attribute?

[Job Snijders]

Dear all,

I want to inject information into syslog when certain magic prefixes are announced or withdrawn. 

So far I have this snippet of configuration, but I'd also like to print the BGP AGGREGATOR ip address, and the AGGREGATOR AS number. How can I do this? 

filter collector_in {                                                                                                                                                       
    if (net ~ [ 84.205.64.0/24, 84.205.65.0/24 ]) then {                                                                                                                    
        print "MAGIC PREFIX SIGNALLED: " , net, "' from AS", bgp_path.last, " via AS", bgp_path.first, " [", proto, "]";                                                    
        accept;                                                                                                                                                             
    }                                                                                                                                                                       
    else accept;                                                                                                                                                            
} 

How can I get BIRD to print something when a prefix is withdrawn? 

Kind regards,

Job