Re: [PATCH installer 2/2] install: do not force gateway to IPv6 RA-received on non-bridged setups

[Gabriel Goller <g.goller@proxmox.com>]

On 10.06.2026 15:27, Christoph Heiss wrote:
> Skip writing the default gateway for the management interface to
> /etc/network/interfaces if it was originally received through an IPv6
> RA.
> 
> Otherwise, fresh, non-bridged (aka. anything other than PVE)
> installations will repeatedly, i.e. on every received RA advertising a
> different SLAAC-capable prefix, report an error in the journal that a
> default gateway already exists.
> 
> The Rust struct definitions are not touched, as the information is not
> needed there (yet).
> 
> Suggested-by: Gabriel Goller <g.goller@proxmox.com>
> Signed-off-by: Christoph Heiss <c.heiss@proxmox.com>

Also for the record, because we talked about it:

This only affects pmg, pbs and pdm, because there we set the ip address directly
on the physical interface. In pve the physical interface is enslaved on the
default vmbr0 bridge and the bridge has an ip address. When
ifupdown2 creates a bridge with an ip address, then automatically
adds net.ipv6.conf.vmbr0.forwarding=1 (the bridge also has the default
net.ipv6.conf.vmbr0.accept_ra=1), which means it will drop every RA. So maybe we
should set accept_ra=2 so that the bridge can accept RAs?

Anyway, we can defer the pve problem for later -- pbs,pmg,pdm are more important
because there we get a kernel error every few seconds.

We also thought more generally about if we should disable RAs on the physical
(or management) nics, because we always want to have a static address on our
installations and dhcp/slaac are actually just "autofills" in the installer?

Note: Search "accept_ra" on https://docs.kernel.org/networking/ip-sysctl.html.