route withdrawals are not sent upon protocol removal

[Thomás S. Bregolin]

On Wed, Jun 6, 2018 at 2:25 PM, Ondrej Zajicek <santiago at crfreenet.org>
wrote:

> On Wed, Jun 06, 2018 at 01:33:53PM +0100, Thomás S. Bregolin wrote:
> [...]
> > I've attached a modified version of the test-withdraw script showing the
> > issue. It seems my problem is related to the "start delay time" option.
> > When I set it to 1, sometimes the withdrawal is sent, and sometimes it
> > isn't. However, when it *isn't* sent, it is *never* sent, no matter how
> > long I wait. The problem is solved by setting the timeout to a higher
> > value, or using the default 5 seconds.
>
> Hello
>
> Note that in the modified version no protocols are removed, both testproto
> and testproto2 are still configured and running. Just the BGP export
> filter was changed, and because 'configure soft' was used, then it was
> not reloaded. That is expected.
>
> But it is likely that if both changes happen simultaneously, i.e. a
> static protocol is removed and a BGP export filter is changed to no
> longer allow routes from that protocol, then withdraws are not sent. This
> is likely a bug, could be avoided by not doing both protocol removal and
> export filter change at the same time.
>

Oh, interesting! Indeed, if I remove just the filter or both the filter and
route, the withdrawals are not sent. However, if I remove only the route,
the withdrawal is sent.

Indeed, as you say, it sounds like a bug. For two reasons:

- BIRD should never remove a protocol without sending a withdrawal (unless
that is wanted as a feature or configuration option);
- There is no reason why removing the filter at the same time as the route
should change the behaviour;

Thank you once again for looking into this. Please let me know if I should
write up a proper bug report and send it here.


Thomás
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