[bird-ospf] LSA forward-address is incorrect

[danilov]

Hello.

I have a small network with several bird routers as bgp and ospf routers.

EBGP-session has been established between one of our bgp-routers and customer
router with multihop feature through OSPF-domain and iBGP-domain.

Then bgp-router advertises the customer announce to other bgp-router, that
also works as OSPF ASBR (ospf-domain on the one side and ibgp-domain on the
other side). On this ASBR-router I see the valid next-hop value (customer
router IP-address in OSPF-domain) in the corresponded routes of customer.

This routes are installed to OSPF-domain, but in the outgoing LSA-updates
I see only 0.0.0.0 forward-address values instead the customer router IP-address
(I have checked it with wireshark).

Brief flowchart:

(CUSTOMER-ROUTER)--(PE)--<ospf-domain>--(ASBR)--<ibgp-domain>--(BGP-ROUTER)
          \                                                      /
           \-------------------EBGP session---------------------/


Some info from ASBR:

>From bird command line.

bird> show route all XX.XX.102.0/23 export ospf_tst
XX.XX.102.0/23    via YY.YY.0.210 on eth1 [bgp_tst_r1 12:41:09] * (100) [AS____i]
        Type: BGP unicast univ
        BGP.origin: IGP
        BGP.as_path: 48938
        BGP.next_hop: ZZ.ZZ.21.94 <-- this address of the customer router in the ospf network (correct)
        BGP.med: 0
        BGP.local_pref: 800
        OSPF.metric1: 16777215
        OSPF.metric2: 10000
        OSPF.tag: 0x00000000
        OSPF.router_id: 0.0.0.0

bird> show route all for ZZ.ZZ.21.94 protocol ospf_tst
ZZ.ZZ.21.92/30    via WW.WW.6.32 on eth0.4 [ospf_tst 13:47:14] * I (150/16) [WW.WW.6.32]
        Type: OSPF unicast univ
        OSPF.metric1: 16
        OSPF.metric2: 16777215
        OSPF.tag: 0x00000000
        OSPF.router_id: WW.WW.6.32 <-- pe-router

-------------------------
Dump of LSA-packet:

Open Shortest Path First
    OSPF Header
        Version: 2
        Message Type: LS Update (4)
        Packet Length: 64
        Source OSPF Router: YY.YY.0.10 (YY.YY.0.10)
        Area ID: 0.0.0.0 (0.0.0.0) (Backbone)
        Checksum: 0x0000 (None)
        Auth Type: Cryptographic (2)
        Auth Crypt Key id: 1
        Auth Crypt Data Length: 16
        Auth Crypt Sequence Number: 6541704
        Auth Crypt Data: 973debe532daa553f846053cd44d481f
    LS Update Packet
        Number of LSAs: 1
        AS-External-LSA (ASBR)
            .000 0000 0000 0001 = LS Age (seconds): 1
            0... .... .... .... = Do Not Age Flag: 0
            Options: 0x02 (E)
                0... .... = DN: Not set
                .0.. .... = O: Not set
                ..0. .... = DC: Demand Circuits are NOT supported
                ...0 .... = L: The packet does NOT contain LLS data block
                .... 0... = NP: NSSA is NOT supported
                .... .0.. = MC: NOT Multicast Capable
                .... ..1. = E: External Routing Capability
                .... ...0 = MT: NO Multi-Topology Routing
            LS Type: AS-External-LSA (ASBR) (5)
            Link State ID: XX.XX.102.0 (XX.XX.102.0)
            Advertising Router: YY.YY.0.10 (YY.YY.0.10)
            Sequence Number: 0x80000001
            Checksum: 0xb1b5
            Length: 36
            Netmask: 255.255.254.0 (255.255.254.0)
            External Type: Type 1 (metric is specified in the same units as interface cost)
            Metric: 20
            Forwarding Address: 0.0.0.0 (0.0.0.0) <-- should be ZZ.ZZ.21.94
            External Route Tag: 0
---------------------

Currently the workaround are used  -static route on the PE,
but this way has corresponded issues.


With best regards, Anton Danilov

littlesmilingcloud at gmail.com