Improper exports with BGP6 over IPv4

[Stefan Jakob]

Ave,

I am not sure, if I totally understand what you're trying to achieve.

Do you think bird is behaving different for a not bird endpoint like the
Mikrotic?

Independent of your problem a general approach for debugging bgp
awkwardness. I love to use tcpdump and Wireshark to see what's going on, so
you do not have to rely on debug output or built-in counters.

Rgds, SJ



Ave <ave at ave.zone> schrieb am Mo., 29. Juni 2020, 00:50:

> Hello,
>
> I believe I stumbled upon a bug in BIRD 2.x while doing something that can
> only be summed up as "testing things on someone else's network with limited
> access provided to me".
>
> When peering over IPv4 yet exporting a full table, I am noticing that all
> exports, withdraw or update, are exported as withdrawals.
>
> Export side:
>
>     Routes:         0 imported, 85839 exported, 0 preferred
>     Route change stats:     received   rejected   filtered    ignored
> accepted
>       Import updates:              0          0          0
> 0          0
>       Import withdraws:            0          0        ---
> 0          0
>       Export updates:          85840          0          0        ---
> 85840
>       Export withdraws:            0        ---        ---
> ---          0
>
> Import side:
>
>     Routes:         0 imported, 0 exported, 0 preferred
>     Route change stats:     received   rejected   filtered    ignored
> accepted
>       Import updates:              0          0          0
> 0          0
>       Import withdraws:        85823          0        ---
> 85823          0
>       Export updates:              0          0          0
> ---          0
>       Export withdraws:            0        ---        ---
> ---          0
>
> I've also tested with an instance where there were both updates and
> withdrawals exported, and as a result a sum of both were displayed as
> imported withdrawals.
>
> The configurations I've tested with are quite simple:
>
> Full import config (seems to import "correctly", but as exports seem to be
> faulty it all gets recorded as withdrawals):
>
> > log syslog all;
> > router id 192.168.4.22;
> > protocol device {
> >         scan time 5;
> > }
> >
> > protocol bgp bird1 {
> >         local 192.168.4.22 as 65529;
> >         neighbor 192.168.4.1 as 65530;
> >         multihop;
> >
> >         ipv6 {
> >                 import all;
> >                 export none;
> >         };
> > }
>
> Trimmed export config that doesn't export correctly:
>
> > protocol bgp bird2 {
> >     local 192.168.4.1 as 65530;
> >     neighbor 192.168.4.22 as 65529;
> >     multihop;
> >
> >     ipv6 {
> >         import none;
> >         export all;
> >     };
> > }
>
> Things I've so far:
>
> - Doing BGP4 over IPv4 (renaming "ipv6" blocks to "ipv4" in configs). This
> had no issues, exports and imports were correct.
> - Doing BGP4 over IPv6 (doing same change as last point, plus changing
> IPv4 addresses to IPv6 ones in configs). This had no issues, exports and
> imports were correct.
> - Switching from IPv4 to IPv6 (changing IPv4 addresses to IPv6 ones in
> configs). This resulted in proper imports, hinting that problem only
> happens on BGP6 over IPv4.
> - Exporting to a non-bird2 BGP daemon. Specifically, I exported to a
> mikrotik router running ROS v6.46.6. It also classified these as
> withdrawals ("Withdrawn Received        85 979", with empty "Prefix Count"
> and "Updates Received").
>
> Thanks and I hope I'm not just doing something wrong and wasting your time
> as a result,
> Ave
>
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