From: Chris Adams <linux@cmadams•net>
To: Stefano Brivio <sbrivio@redhat•com>
Cc: Fernando Fernandez Mancera <fmancera@suse•de>,
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,
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: Fri, 29 May 2026 07:06:41 -0500 [thread overview]
Message-ID: <20260529120641.GA19331@cmadams.net> (raw)
In-Reply-To: <20260529134045.56330243@elisabeth>
Once upon a time, Stefano Brivio <sbrivio@redhat•com> said:
> 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.
I hit two cases that triggered the behavior:
- after an overnight suspend/resume cycle (not sure if there's a minimum
time suspended)
- with a bridge NIC, after stopping a VM with a NIC on the bridge (which
removed an fe80:: link-local address); this is the case I used to
bisect since it was easy to script
In both cases, the next IPv6 router-advertisement received was what
triggered NetworkManager to replace the current privacy addresses. This
could be 2-3 minutes after the trigger.
> > This reverts commit cb3de96eea66f5e4a580086c6a1be46e765f97f4.
> >
> > Fixes: cb3de96eea66 ("ipv6: preserve insertion order for same-scope addresses")
> > Reported-by: Chris Adams <linux@cmadams•net>
> > Closes: https://lore.kernel.org/netdev/20260521135310.GC977@cmadams.net/
> > Signed-off-by: Fernando Fernandez Mancera <fmancera@suse•de>
> > ---
> > v2: updated commit description to make it more accurate
> > ---
> > net/ipv6/addrconf.c | 2 +-
> > tools/testing/selftests/net/ioam6.sh | 2 +-
> > 2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> > index 5476b6536eb7..bb84a78b80f6 100644
> > --- a/net/ipv6/addrconf.c
> > +++ b/net/ipv6/addrconf.c
> > @@ -1013,7 +1013,7 @@ ipv6_link_dev_addr(struct inet6_dev *idev, struct inet6_ifaddr *ifp)
> > list_for_each(p, &idev->addr_list) {
> > struct inet6_ifaddr *ifa
> > = list_entry(p, struct inet6_ifaddr, if_list);
> > - if (ifp_scope > ipv6_addr_src_scope(&ifa->addr))
> > + if (ifp_scope >= ipv6_addr_src_scope(&ifa->addr))
> > break;
> > }
> >
> > diff --git a/tools/testing/selftests/net/ioam6.sh b/tools/testing/selftests/net/ioam6.sh
> > index b2b99889942f..845c26dd01a9 100755
> > --- a/tools/testing/selftests/net/ioam6.sh
> > +++ b/tools/testing/selftests/net/ioam6.sh
> > @@ -273,8 +273,8 @@ setup()
> > ip -netns $ioam_node_beta link set ioam-veth-betaR name veth1 &>/dev/null
> > ip -netns $ioam_node_gamma link set ioam-veth-gamma name veth0 &>/dev/null
> >
> > - ip -netns $ioam_node_alpha addr add 2001:db8:1::2/64 dev veth0 &>/dev/null
> > ip -netns $ioam_node_alpha addr add 2001:db8:1::50/64 dev veth0 &>/dev/null
> > + ip -netns $ioam_node_alpha addr add 2001:db8:1::2/64 dev veth0 &>/dev/null
> > ip -netns $ioam_node_alpha link set veth0 up &>/dev/null
> > ip -netns $ioam_node_alpha link set lo up &>/dev/null
> > ip -netns $ioam_node_alpha route add 2001:db8:2::/64 \
>
> --
> Stefano
--
Chris Adams <linux@cmadams•net>
next prev parent reply other threads:[~2026-05-29 12:06 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 [this message]
2026-06-01 2:03 ` Matthieu Baerts
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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