BIRD ripng default gateway route strange behavior

[olivier a]

Hello all ^^

I'm puzzled with a really weird RIPng default gateway propagation problem.
I don't quite understand what's happening. Here is what happens ...

Network topology :

PC1---Router1---Router2----InternetGateway---z

RIPng enabled on PC1, Router1, Router2
Router2 has a static IPv6 DG ( Default Gateway ) to InternetGateway
Router1 has no static IPv6 DG, and no kernel{learn} directive.

Router2=Ubuntu14.04 LTS, Router1=raspbian Wheezy, bird = last version,
compiled from sources
link-local addresses replaces with symbolic names ( ie [fe80::Router1] )

Something really strange seems to happen :

. Router2 gets this routing table :

default via InternetGateway dev eth0  proto static  metric 1
default via [fe80::Router1] dev eth1  proto bird  metric 1024

But Router1 isn't announcing any IPv6 DefaultGateway, just ::/0 metric 16 (
ie it is poisoning the route ).
( I checked using Wireshark ).

Is there a bug that transforms a received "::/0 metric 16" into a "default
via [fe80::Router1] dev eth1  proto bird  metric 1024" route ?

Here is Router2 bird6.conf file :

-------------------------------------------------
log syslog all;
debug protocols all;
#log stderr all;
#log "tmp" all;

router id 192.168.4.1;
protocol kernel {
learn;
scan time 20;
export all;
import all;
}

protocol direct {
#interface "eth0";
}

protocol device {
scan time 10;
}

protocol rip {
debug all;
port 521;
interface "*" { mode multicast; ttl security on; };
honor neighbor;
authentication none;
import all;
export all;
}
-------------------------------------------------------------

I managed to solve the problem, by having Router2 drop incomming ::/0
announcements :

---------------------------------------------------------
import filter {   # This block filters ::/0 in
                if net ~ [ ::/0+ ] then
                        reject "ripng:rejected:DG";
                else
                        accept "ripng:accepted:not-DG";
        };

export all;

---------------------------------------------------------

the problem is solved, yet it puzzles me.
This is really strange. Does anybody understand what is happening ??
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