hello,

i'm using BIRD 3.2.0 on FreeBSD 15.0.  i have a PPPoE interface with a
point-to-point IPv4 address configured:

        ng0: 
flags=10088d1<UP,POINTOPOINT,RUNNING,NOARP,SIMPLEX,MULTICAST,LOWER_UP> metric 0 
mtu 1500
                options=0
                inet 81.187.73.117 --> 81.187.81.187/32
                inet6 2001:8b0:aab5:1::1/128
                inet6 fe80::227c:14ff:fef3:d8f7%ng0/64 scopeid 0x12
                groups: arpa
                nd6 options=1<PERFORMNUD>

i would like to advertise this in OSPF as a passive interface, so i configured
the OSPF protocol:

        define OSPF_V6_EXPORT = [
        ];

        define OSPF_V4_EXPORT = [
                0.0.0.0/0
        ];

        filter ospf_export {
                if (net ~ OSPF_V6_EXPORT) then accept;
                if (net ~ OSPF_V4_EXPORT) then accept;
                reject;
        };

        protocol ospf v2 core4 {
                ipv4 {
                        export filter ospf_export;
                        import all;
                };

                area 0 {
                        interface "ng0" {
                                stub yes;
                        };
                        [... other config elided ...]
                };
        }

however, BIRD does not advertise 81.187.73.117/32 in OSPF.  it *does* advertise
81.187.81.187/32, which is the remote side of the interface.

the interface looks fine in BIRD:

        bird> show ospf interface "ng0"
        core6:

        core4:
        Interface ng0 (peer 81.187.81.187)
                Type: ptp
                Area: 0.0.0.0 (0)
                State: PtP (stub)
                Priority: 1
                Cost: 10
                ECMP weight: 1
                Hello timer: 10
                Wait timer: 40
                Dead timer: 40
                Retransmit timer: 5

the route:

        bird> show route for 81.187.73.117/32
        Table master4:
        0.0.0.0/0            unicast [kernel4 2026-07-04] ! (10)
                via 81.187.81.187 on ng0
        81.187.73.117/32     unicast [kernel4 2026-07-04] ! (10)
                dev lo0

if i add 81.187.73.117/32 to OSPF_V4_EXPORT, then it is correctly advertised as
an E2 route, which is fine as a workaround, but i would like to understand why
the interface configuration doesn't work.

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