BMP: no monitoring messages when enabled after BGP sessions (BIRD 3.2.1)

[Thomas Holterbach]

Dear BIRD community,

I am running a BMP collector and encountering an issue where no monitoring messages are exported over BMP, even though I am using the latest BIRD version (3.2.1), which should include the fix for the previous route export bug:

https://gitlab.nic.cz/labs/bird/-/commit/2500b450b404ab41eeff3b2d92ba943d0178fb50

We tested this both in our lab and with a network operator, and consistently observe the following behavior:

If the BMP session is activated before the BGP sessions, everything works as expected, and monitoring messages are exported.

If the BGP sessions are established before enabling BMP, then BMP does not export monitoring messages at all.

This suggests that BMP does not correctly pick up already-established BGP sessions.

Below is a minimal configuration example. The behavior depends solely on the order in which the sessions are established :

debug protocols all;

router id 192.168.222.54;

protocol kernel {
    ipv4 {
        export all;
    };
}

protocol device {
    scan time 10;
}

filter ALLOW_ALL { accept; }

protocol bmp {
    station address ip 192.168.222.1 port 4567;
    monitoring rib in pre_policy;
    tx buffer limit 1024;
}

protocol bgp peer_asn_10 {
    local 192.168.222.54 as 11;
    neighbor 192.168.222.52 as 10;
    multihop 255;

    ipv4 {
        import all;
        export all;
        next hop self;
        import table on;
    };

    ipv6 {
        import all;
        export all;
        next hop self;
        import table on;
    };
}

protocol bgp peer_asn_12 {
    local 192.168.222.54 as 11;
    neighbor 192.168.222.53 as 12;
    multihop 255;

    ipv4 {
        import all;
        export all;
        next hop self;
    };

    ipv6 {
        import all;
        export all;
        next hop self;
    };
}
Has anyone else experienced similar behavior? Could this be another bug related to BMP?

Thanks in advance for your help.

Best regards,
Thomas
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