[PATCH v3] Babel: Replace internal route selection by bird's nest

[Maria Matejka]

Hello!

Picking up this, hoping that it is still relevant.

>> Is there a way we can easily trigger a protocol restart instead of crashing
>> all of bird with an assertion here if this does happen against all odds?
> 
> Hmm, no, I don't think there's any way that the protocol can signal to
> the nest that it has gotten itself into an inconsistent state and needs
> to be restarted. Not sure if it's better to just crash in this case, or
> if we should add such a mechanism? Hopefully Ondrej has an opinion...

You can do this as the import/export limits in BGP do exactly this, yet 
the appropriate function

   void proto_schedule_down(struct proto *p, byte restart, byte code);

is currently marked static. There is no problem making this function 
static in case the protocol needs restart.

Another way to do this is to initiate the protocol shutdown yourself by 
calling proto_notify_state(p, PS_DOWN) which restarts the protocol 
unless you set disabled = 1 … or if you need to do some asynchronous 
work, you may call first proto_notify_state(p, PS_STOP), then do and 
schedule that work and after it is finally done, you call 
proto_notify_state(p, PS_DOWN).

Note that notifying DOWN is the last thing you want to do; your memory 
may get freed any time after that.

I should definitely put some time into writing a "how to write a 
protocol" guide.

Hope this helps you.
Maria
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