BIRD continues exporting routes but reports no exports
Alexander Zubkov
green at qrator.net
Fri Mar 3 19:17:56 CET 2023
Hi,
It is documented in recent versions and on the bird's site too. Pay
attention to this:
[(import|export) table p.c]
On Fri, Mar 3, 2023, 18:32 Hugo Slabbert via Bird-users <
bird-users at network.cz> wrote:
> Right, so,
>
> I've gone ahead and enabled export tables on the channels for the relevant
> peers, per Alexander's suggestion for possibly getting additional
> visibility. I don't seem to spot any different views for route status,
> though. I don't see any particular docs on how to *view* export tables;
> does enabling export tables make a different view available to look at the
> export table contents specifically? Or does it just shift the behaviour so `show
> route export <protocol>` displays the export table contents rather than a
> point-in-time evaluation of export filters for the specified neighbor?
>
> Snippet showing export tables config enabled for the peers:
>
> ```
> template bgp GATEWAY_v6 {
> hold time 6;
> startup hold time 20;
> connect delay time 3;
> connect retry time 6;
> error wait time 3, 12;
> med metric;
> allow local as 1;
>
> local fdff::4:2 as MENLO_ASN;
>
> ipv6 {
> export table on;
> import filter GATEWAY_IMPORT_v6;
> export filter GATEWAY_EXPORT_v6;
> };
> ipv4 {
> export table on;
> extended next hop on;
> add paths rx;
> import filter GATEWAY_IMPORT_v4;
> export filter GATEWAY_EXPORT_v4;
> };
> }
> # ...
> protocol bgp gw_085ea85_euwest2 from GATEWAY_v6 {
> neighbor fdff::8005:f4d1 as 65000;
> }
> ```
>
> I don't see any different behaviour on the affected hosts, though. E.g. a
> host that just had `configure` called once after setting the draining
> flag is showing these symptoms, showing nothing for `show route export
> <protocol>`:
>
> ```
> bird> show route export gw_085ea85_euwest2
> bird>
> ```
>
> ...but still showing exports under the protocol details:
>
> ```
> bird> show protocols all gw_085ea85_euwest2
> Name Proto Table State Since Info
> gw_085ea85_euwest2 BGP --- up 2023-03-03 16:33:43
> Established
> BGP state: Established
> # ...
> Channel ipv6
> State: UP
> Table: master6
> Preference: 100
> Input filter: GATEWAY_IMPORT_v6
> Output filter: GATEWAY_EXPORT_v6
> Routes: 2 imported, 2 exported, 1 preferred
> Route change stats: received rejected filtered ignored
> accepted
> Import updates: 3 0 1 0
> 2
> Import withdraws: 0 0 --- 0
> 0
> Export updates: 109 5 96 ---
> 8
> Export withdraws: 2 --- --- ---
> 2
> BGP Next hop: fdff::4:2
> Channel ipv4
> State: UP
> Table: master4
> Preference: 100
> Input filter: GATEWAY_IMPORT_v4
> Output filter: GATEWAY_EXPORT_v4
> Routes: 12 imported, 1 exported, 0 preferred
> Route change stats: received rejected filtered ignored
> accepted
> Import updates: 12 0 0 0
> 12
> Import withdraws: 0 0 --- 0
> 0
> Export updates: 39 4 31 ---
> 4
> Export withdraws: 0 --- --- ---
> 1
> BGP Next hop: fdff::4:2
> ```
>
> Note this is still on 2.0.7. We've bumped some hosts to 2.0.10, but as
> indicated in the previous message, just a simple restart clears this issue
> from occurring. We've enabled the export table config on both a 2.0.7 and
> a 2.0.10 host, to be able to possibly spot if this reoccurs on the 2.0.10
> host as well after a period. An example host on 2.0.7 showing this
> behaviour has been up for ~2 weeks. The box upgraded to 2.0.10 has had BIRD
> running for just ~16 hours at this point and is not yet showing any issues.
>
> On Thu, Mar 2, 2023 at 4:07 PM Hugo Slabbert <
> hugo.slabbert at menlosecurity.com> wrote:
>
>> A slight update on this:
>>
>> 3f477ccb
>> <https://gitlab.nic.cz/labs/bird/-/commit/3f477ccb03ed99cf6754baaca179fcf791bcda55>
>> does appear to be in 2.0.7, which we're running, so if that's the issue
>> that may not be the problem.
>>
>> This looked to be successful initially when upgrading to 2.0.10. But, I
>> then checked a box that was still running 2.0.7 and where we could repro
>> it. I simply restarted bird there, and then could no longer repro it.
>>
>> So, just restarting bird at 2.0.7 was sufficient to clear the problem, at
>> least temporarily, and the bump to 2.0.10 then wasn't a clear test, given
>> that's obviously a fresh instance of bird running.
>>
>> We'll try to validate if the problem eventually returns on the 2.0.7
>> box(es) after a restart, and if it does *not* return on the 2.0.10
>> instance, but we don't have a clear timeline at the moment on this if it's
>> something that pops up "in a while" of bird running.
>>
>> On Thu, Mar 2, 2023 at 2:54 PM Hugo Slabbert <
>> hugo.slabbert at menlosecurity.com> wrote:
>>
>>> Was this perhaps 3f477ccb
>>> <https://gitlab.nic.cz/labs/bird/-/commit/3f477ccb03ed99cf6754baaca179fcf791bcda55>
>>> ?
>>>
>>> Filters: Function body comparison result now used.
>>>> Function bodies were compared in post-parse time, yet the result was not
>>>> used and the functions were incorrectly considered the same as before.
>>>
>>>
>>>
>>> Now the result is used to reload affected protocols.
>>>
>>>
>>> On Thu, Mar 2, 2023 at 2:51 PM Hugo Slabbert <
>>> hugo.slabbert at menlosecurity.com> wrote:
>>>
>>>> ah, right, apologies.
>>>>
>>>> bird 2.0.7-4.1 on Debian 11.6, kernel 5.10.136-1
>>>>
>>>> Looks like 2.0.7 was released Oct 16 2019 (
>>>> https://bird.network.cz/?download), so a fair chance we might be
>>>> hitting this? It looks like something from 2.0.10 is available from the
>>>> bullseye backports, with the most recent being 2.0.12 in bookworm or sid.
>>>> I'll look at pulling one of those in to validate.
>>>>
>>>> ...where changes in functions sometimes got ignored.
>>>>
>>>>
>>>> This might be reaching, but would that explain the difference between
>>>> what's shown in route export status output versus what's actually being
>>>> exported?
>>>>
>>>> On Thu, Mar 2, 2023 at 2:39 PM Maria Matejka via Bird-users <
>>>> bird-users at network.cz> wrote:
>>>>
>>>>> Hello!
>>>>>
>>>>>
>>>>> > We've tried adding a sleep between when the include snippet that
>>>>> changes
>>>>> > the DRAIN_NODE value is written and when we hit `birdc configure`,
>>>>> but
>>>>> > that doesn't appear to make any difference. If we execute `birdc
>>>>> > configure` *twice*, though, everything's fine: The actual exports
>>>>> are
>>>>> > stopped. That's true without any sleep or break between running
>>>>> > configure as well; literally just `birdc configure` back to back in
>>>>> the
>>>>> > script that manages this.
>>>>> >
>>>>> > We do not see any indication of issues in the `birdc configure` runs
>>>>> or
>>>>> > in BIRD's logs.
>>>>>
>>>>> You are not disclosing the version of BIRD you are using. I vaguely
>>>>> remember that we fixed this kind of bug several years ago where
>>>>> changes
>>>>> in functions sometimes got ignored.
>>>>>
>>>>> Thus if you are not using a recent BIRD version, you are probably
>>>>> hitting that old bug.
>>>>>
>>>>> Maria
>>>>>
>>>>
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