Re: [PATCH net] Revert "ipv6: preserve insertion order for same-scope addresses"

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 28 May 2026 13:11:23 +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 is caching the networking information from the system and
> later operating with it. It relies on the order of IPv6 addresses to
> configure routes for outgoing traffic.

I think this paragraph should make it clear that NetworkManager relies
on a _reversed_ order (first inserted is returned last), and that it's
the opposite compared to IPv4.

> Revert to the previous ordering.

See my concern from:

  https://lore.kernel.org/all/20260528131250.1352ab48@elisabeth/

(sorry, I sent that email moments after you sent this patch it seems). It
fixes the issue for NetworkManager assuming it's the only issue, but it
causes a regression for others.

If this revert is the only practical solution, so be it. I'm just wondering
if it really is.

> 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>
> ---
>  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