Re: [PATCH] test: Improve logic for waiting for SLAAC & DAD to complete in NDP tests

[Stefano Brivio <sbrivio@redhat.com>]

On Tue, 26 Nov 2024 14:27:27 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Since 9a0e544f05bf the NDP tests attempt to explicitly wait for DAD to
> complete, rather than just having a hard coded sleep.  However, the
> conditions we use are a bit sloppy and allow for a number of possible cases
> where it might not work correctly.  Stefano seems to be hitting one of
> these (though I'm not sure which) with some later patches.
> 
>  - We wait for *lack* of a tentative address, so if the first check occurs
>    before we have even a tentative address it will bypass the delay
>  - It's not entirely clear if the permanent address will always appear
>    as soon as the tentative address disappears
>  - We weren't filtering on interface
>  - We were doing the filtering with ip-address options rather than in jq.
>    However in at least in some circumstances this seems to result in an
>    empty .addr_info field, rather than omitting it entirely, which could
>    cause us to get the wrong result
> 
> So, instead, explicitly wait for the address we need to be present: an
> RA provided address on the external interface.  While we're here we remove
> the requirement that it have global scope: the "kernel_ra" check is already
> sufficient to make sure this address comes from an NDP RA, not something
> else.  If it's not the global scope address we expect, better to check it
> and fail, rather than keep waiting.
> 
> Fixes: 9a0e544f05bf ("test: Improve test for NDP assigned prefix")
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Applied.

-- 
Stefano