From: Matthieu Baerts <matttbe@kernel•org>
To: Stefano Brivio <sbrivio@redhat•com>,
Fernando Fernandez Mancera <fmancera@suse•de>
Cc: netdev@vger•kernel.org, yuhuang@redhat•com,
justin.iurman@gmail•com, horms@kernel•org, pabeni@redhat•com,
kuba@kernel•org, edumazet@google•com, davem@davemloft•net,
idosch@nvidia•com, dsahern@kernel•org,
Chris Adams <linux@cmadams•net>,
David Gibson <david@gibson•dropbear.id.au>,
Beniamino Galvani <bgalvani@redhat•com>,
Thorsten Leemhuis <regressions@leemhuis•info>,
Andrew Lunn <andrew@lunn•ch>,
ihuguet@redhat•com, regressions@lists•linux.dev
Subject: Re: [PATCH net v2] Revert "ipv6: preserve insertion order for same-scope addresses"
Date: Mon, 1 Jun 2026 12:03:59 +1000 [thread overview]
Message-ID: <5079261a-79e5-421b-bf6a-a511acaaeca4@kernel.org> (raw)
In-Reply-To: <20260529134045.56330243@elisabeth>
Hi Stefano,
On 29/05/2026 21:41, Stefano Brivio wrote:
> On Fri, 29 May 2026 13:23:57 +0200
> Fernando Fernandez Mancera <fmancera@suse•de> wrote:
>
>> Chris Adams reported that preserving insertion order for same-scope
>> addresses is causing SSH connections to be dropped after stopping a VM
>> while running NetworkManager.
>>
>> NetworkManager caches the IPv6 address configuration, when a RA arrives,
>> it determines the list of addresses to configure and checks if the
>> addresses are already in the right order in the kernel. If they aren't,
>> NetworkManager removes and re-adds them to achieve the desired order.
>>
>> As the order changes, NetworkManager is confused and reconfigures the
>> addresses on every update. In addition, this would also affect to cloud
>> tooling that relies on IPv6 addresses order to identify primary and
>> secondaries addresses.
>
> By the way, I'm still looking into this part, trying to find
> "problematic" examples.
>
> And I couldn't find any, yet, because it looks like there's always a
> _single_ IPv6 address being used as a secondary for a primary IPv4
> address.
FYI, the order change also affected some specific scripts, e.g. here
with MPTCP and packetdrill:
https://github.com/multipath-tcp/packetdrill/commit/1b7cd4482ce8
Because the order was not "natural" before, and different from IPv4, a
workaround was needed to keep the same order. I was happy to remove it,
but now it looks like I need to re-apply it :)
It would be nice to get the "natural" order back without breaking the
userspace (or with a way to choose the order).
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
next prev parent reply other threads:[~2026-06-01 2:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-29 11:23 [PATCH net v2] Revert "ipv6: preserve insertion order for same-scope addresses" Fernando Fernandez Mancera
2026-05-29 11:41 ` Stefano Brivio
2026-05-29 11:45 ` Fernando Fernandez Mancera
2026-05-29 12:06 ` Chris Adams
2026-06-01 2:03 ` Matthieu Baerts [this message]
2026-06-01 13:35 ` Stefano Brivio
2026-06-01 14:01 ` Íñigo Huguet
2026-06-01 14:22 ` Thorsten Leemhuis
2026-06-03 5:46 ` Matthieu Baerts
2026-06-03 6:53 ` Íñigo Huguet
2026-06-03 7:17 ` Thorsten Leemhuis
2026-06-03 7:29 ` Fernando Fernandez Mancera
2026-06-03 8:00 ` Ido Schimmel
2026-06-03 8:06 ` Fernando Fernandez Mancera
2026-06-03 9:27 ` Matthieu Baerts
2026-06-03 8:02 ` David Gibson
2026-06-02 6:44 ` IPv6 address insertion order (was Re: [PATCH net v2] Revert "ipv6: preserve insertion order for same-scope addresses") David Gibson
2026-06-02 12:46 ` Andrew Lunn
2026-06-03 1:56 ` David Gibson
2026-06-02 13:21 ` Ido Schimmel
2026-06-03 2:34 ` David Gibson
2026-06-03 7:47 ` Ido Schimmel
2026-06-03 15:45 ` Stefano Brivio
2026-06-04 1:26 ` David Gibson
2026-06-04 18:39 ` Ido Schimmel
2026-06-04 22:55 ` Jakub Kicinski
2026-06-05 10:13 ` Stefano Brivio
2026-06-03 15:47 ` Nicolas Dichtel
2026-05-29 20:20 ` [PATCH net v2] Revert "ipv6: preserve insertion order for same-scope addresses" patchwork-bot+netdevbpf
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