Re: kernel protocol ignores default preference during scan

[Maria Matejka via Bird-users]

Hello!






Have a nice day!
Maria

On 9/22/22 21:19, Alexander Zubkov wrote:

I've used your original patch, for now I don't like doing much refactoring like this to keep merging with v3 as simple as possible. Anyway, thank you for sending the patch, I've implemented a kernel-route-learn test, found out that indeed there is the bug you found and applied it.

And just an idea. I've attached the patch as an example, although it
should be functional too. I mentioned that functions krt_learn_async()
and krt_learn_scan() are very similar and I thought that it may be
useful to join them into a single function. If I did not make a
mistake, all code pathes should be almost the same, with a couple of
minor exceptions:
1) old_best is set in the beginning, but was earlier only for async version
2) g = NULL after rte_free(g) in one of the branches, but it does not
affect anything and may be dropped

On Wed, Sep 21, 2022 at 6:00 PM Maria Matejka via Bird-users
<bird-users@network.cz> wrote:

Hello!

Thank you for finding and fixing. Will check and include.

Maria

On 9/21/22 17:15, Alexander Zubkov via Bird-users wrote:

I made a trivial patch for the case.

On Tue, Sep 20, 2022 at 6:23 PM Alexander Zubkov <gr...@qrator.net> wrote:

Hi,

Bird from master branch ignores the default preference set in channel
for a kernel protocol, like that:

protocol kernel {
          learn yes;
          ipv4 {
                  preference 200;
                  import all;
                  export none;
          };
}

Version 2.0.10 seems ok. I suppose the change was introduced with this commit:

https://gitlab.nic.cz/labs/bird/-/commit/eb937358c087eaeb6f209660cc7ecfe6d6eff739

It adds setting of the preference to the krt_learn_async() function.
But as I understand when route is learned with netlink hook it is
processed like this:
nl_parse_route -> krt_got_route_async -> krt_learn_async
But when it is learned from scan, it is processed like this:
nl_parse_route -> krt_got_route -> krt_learn_scan

And setting preference was not added to krt_learn_scan() function.

I also saw that in my test - when I added a new route to the kernel
while bird was running, it appeared in bird with correct preference.
But some time after, the scan updated the route and it was replaced
with the default preference.

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