Optional attribute error peering BGP with FRR

[Hansen, Christoffer]

Derrick,

Possible a missing next-hop attribute can be the case?

 From [0]:
         attribute           EBGP                    IBGP
          ORIGIN             mandatory               mandatory
          AS_PATH            mandatory               mandatory
          NEXT_HOP           mandatory               mandatory

ORIGIN and AS_PATH is attached as attributes to the BGP Update Message. 
No NEXT_HOP, thou.

Christoffer

[0]: https://tools.ietf.org/html/rfc4271#section-5 (p. 25)

On 11/07/2019 13:41, Derrick Lim wrote:
> Hello everyone,
> 
> I’m having an issue with FRR running on Cumulus (4.0+cl3u10), which is
> peering BGP to BIRD (2.0.2, also tried 1.6.3).
> 
> When certain routes from FRR are advertised to BIRD (I configured them
> through vrf leaking on FRR, but not sure if that matters, or its just
> something with the routes), BIRD terminates the BGP session with an
> `Optional attribute error` (on BIRD 2.0.2, different error on 1.6.3)
> when receiving the BGP UPDATE message.
> 
> I’m not sure if this an FRR or BIRD issue, so I'm hoping someone here
> could take a look if the UPDATE message from FRR could possibly be
> malformed, or is BIRD handling this in an odd way.
> 
> I've attached the tcpdump as well as error logs from BIRD, along with
> the bird.conf, as well a portion of the FRR config.
> 
> 100.91.38.1 is the host running BIRD.
> 100.91.38.61 is the host running FRR.
> 
> Regards,
> Derrick
> 
-------------- next part --------------
Frame 40: 130 bytes on wire (1040 bits), 130 bytes captured (1040 bits)
Linux cooked capture
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 1000
Internet Protocol Version 4, Src: 100.91.38.61, Dst: 100.91.38.1
Transmission Control Protocol, Src Port: 179, Dst Port: 54139, Seq: 112, Ack: 100, Len: 58
Border Gateway Protocol - UPDATE Message
    Marker: ffffffffffffffffffffffffffffffff
    Length: 58
    Type: UPDATE Message (2)
    Withdrawn Routes Length: 0
    Total Path Attribute Length: 34
    Path attributes
        Path Attribute - ORIGIN: IGP
            Flags: 0x40, Transitive, Well-known, Complete
                0... .... = Optional: Not set
                .1.. .... = Transitive: Set
                ..0. .... = Partial: Not set
                ...0 .... = Extended-Length: Not set
                .... 0000 = Unused: 0x0
            Type Code: ORIGIN (1)
            Length: 1
            Origin: IGP (0)
        Path Attribute - AS_PATH: 4272357393 4272357377 4272357378 4272357376 4259905537 54058 
            Flags: 0x50, Transitive, Extended-Length, Well-known, Complete
                0... .... = Optional: Not set
                .1.. .... = Transitive: Set
                ..0. .... = Partial: Not set
                ...1 .... = Extended-Length: Set
                .... 0000 = Unused: 0x0
            Type Code: AS_PATH (2)
            Length: 26
            AS Path segment: 4272357393 4272357377 4272357378 4272357376 4259905537 54058
                Segment type: AS_SEQUENCE (2)
                Segment length (number of ASN): 6
                AS4: 4272357393
                AS4: 4272357377
                AS4: 4272357378
                AS4: 4272357376
                AS4: 4259905537
                AS4: 54058
    Network Layer Reachability Information (NLRI)
        0.0.0.0/0
            NLRI prefix length: 0
            NLRI prefix: 0.0.0.0
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