Re: [PATCH v4 0/5] Improve robustness of migration

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 27 Feb 2025 16:55:12 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> From Red Hat internal testing we've had some reports that if
> attempting to migrate without passt-repair, the failure mode is uglier
> than we'd like.  The migration fails, which is somewhat expected, but
> we don't correctly roll things back on the source, so it breaks
> network there as well.
> 
> Address this and several other fragilities in the migration.
> 
> Everything tested with the basic test suite, plus some additional
> testing for the specific functionality of the patches:
> 
> For patches 1..2:
>  * I get a clean migration if there are now active flows
>  * Migration completes, although connections are broken if
>    passt-repair isn't connected
> 
> For patches 3..5:
>  * Migration completes ok if the source and destination hosts have
>    different IPs
>  * Target correctly sees the bind() failure and abandons the flow
>  * Unfortunately, target-side client doesn't get a reset, it just sits
>    there not working.  This is because a) the RST we try to send is
>    lost because the queue is still inactive over the migration and b)
>    we don't send RSTs or ICMPs for packets from the guest which no
>    longer match a flow (I hope to tackle this soon)
>  * After manually quitting the stuck client on the target, other
>    connectivity works

Applied. I didn't manage to try out the setup you proposed yet, but I
tried things out in my partial flow (with migration succeeding but
connections closing right away) and everything looks fine there.

-- 
Stefano