OSPF bad packet

[Ondrej Zajicek]

On Mon, Apr 15, 2024 at 02:22:01PM +0000, Benoit Chesneau wrote:
> Hi Ondrej,
> 
> Not sure I undersand, these are the IPs of this router itself:
> 
> ```
> root at gw0:~ # ifconfig vlan600
> vlan600: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 9000
>         description: backbone
>         options=1c680703<RXCSUM,TXCSUM,TSO4,TSO6,LRO,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6,MEXTPG,TXTLS4,TXTLS6>
>         ether fa:9b:80:06:d7:f9
>         inet 198.19.4.33 netmask 0xffffffe0 broadcast 198.19.4.63
>         inet6 fe80::f89b:80ff:fe06:d7f9%vlan600 prefixlen 64 scopeid 0x5
>         inet6 2001:7f8::2:103::1 prefixlen 64
>         groups: vlan
>         vlan: 600 vlanproto: 802.1q vlanpcp: 0 parent interface: mce0
>         media: Ethernet 25GBase-SR <full-duplex,txpause>
>         status: active
>         nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> ```
> 
> 
> I didn't find equivalent router id on the network. I also tried to uniquely change the ID but the same error appears. Is there anything I could do to debug this issue ? 

Hi

It seems like the OSPF receives its own packets back. There is a check
that should make them to be silently ignored:

  /* We want just packets from sk->iface. Unfortunately, on BSD we cannot filter
     out other packets at kernel level and we receive all packets on all sockets */
  if (sk->lifindex != sk->iface->index)
    return 1;

But for some reason it does not work in your case, AFAIK it worked in
older BSDs. It should be harmless outside of spanning your logs.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
"To err is human -- to blame it on a computer is even more so."