[patch] interface routes

[Ermal Luçi]

On Thu, Mar 7, 2013 at 2:51 PM, Andre Oppermann <andre at freebsd.org> wrote:

> On 07.03.2013 14:38, Ermal Luçi wrote:
>
>> On Thu, Mar 7, 2013 at 12:55 PM, Andre Oppermann <andre at freebsd.org<mailto:
>> andre at freebsd.org>> wrote:
>>
>>     On 07.03.2013 12:43, Alexander V. Chernikov wrote:
>>
>>         On 07.03.2013 11:39, Andre Oppermann wrote:
>>
>>             On 07.03.2013 07:34, Alexander V. Chernikov wrote:
>>
>>                 Hello list!
>>
>>                 There is a known long-lived issue with interface routes
>>                 addition/deletion:
>>
>>                 ifconfig iface inet 1.2.3.4/24 <http://1.2.3.4/24> can
>> fail if given prefix is
>>
>>                 already in
>>                 kernel route table (for
>>                 example, advertised by IGP like OSPF).
>>
>>                 Interface route can be deleted via route(8) or any route
>> socket user
>>                 (sometimes this happens with
>>                 popular opensource daemons like bird/quagga).
>>
>>                 Problem is reported at least in kern/106722 and
>> kern/155772.
>>
>>
>>             You patch is a welcome addition.
>>
>>                 This can be fixed the following way:
>>                 Immutable route flag (RTM_PINNED, added in 19995 with
>> 'for future use'
>>                 comment) is utilised to mark
>>                 route 'immutable'.
>>                 rtrequest1_fib refuses to delete routes with given flag
>> unless
>>                 RTM_PINNED is set in rti_flags.
>>
>>
>>             How do the routing daemons react to being unable to
>> change/delete
>>             such a route?
>>
>>         routing daemons live long with the fact that there route socket
>> cmds can
>>         fail (and the is route(8) utility which can do anything), so
>> typically
>>         bird/quagga yells like
>>         'bird: KRT: Error sending route 11.0.0.0/24 <http://11.0.0.0/24>
>> to kernel: File exists'
>>
>>         and marks given route as not installed in internal RIB.
>> Additionally,
>>         daemon will probably re-try to insert such routes on every
>> periodic KRT
>>         rescan (tens of minutes).
>>
>>
>>
>> Isn't it better to teach the routing code about metrics.
>> Routing daemons cope better this way and they can handle this.
>> So the policy of this behaviour can be controled by administrator rather
>> than by code!
>> With metrics you can add routes with bigger metric for interfaces and
>> lower from routing daemons.
>> This also can mitigate somehow on interfaces with the same subnet
>> configured possibly.
>>
>
> Generally I agree with you that this would be the ideal outcome.
> However we're still quite a bit away from reaching that goal.
> To make this really work we have make mpath plus metrics a first
> class citizen in the routing code and also the update the routing
> daemons kernel interfaces to know about this.  I hope we get there
> in the not too distant future.
>
> As a first step I think it is important that Alexanders patch goes
> in to fix a long standing and very annoying problem with the code
> we have.  Also the link down route withdraw should be added asap.
> Then we can take the next steps towards the ultimate goal you describe.
>
> I hope you do not object to Alexanders patch?



No objection, just trying to put the focus where it needs to be.

Yeah its good to have options there just as always the interface route
should not be scrubbed on interface event
since bound sockets to that interface will behave strangely.


>
>
> --
> Andre
>
>


-- 
Ermal