[systemd-devel] networkd : ipv6 RA (not prefix delegation)

[Ede Wolf]

Am 05.09.22 um 19:45 schrieb Arian van Putten:
> Just thinking out loud here but aren't RA messages are sent as link 
> local multicast messages? How can it send them if you disable link local 
> addressing?

Yes, RA are being sent as ll multicast. But the interface  does have a 
valid link local address. LinkLocalAddressing= refers to 
autoconfiguration (according to the documentation on freedesktop), not 
to the disablement of link local adresses.
A link local address ist of course required, I just happen to configure 
it manually, not via autoconfiguration.

Unless I miss something fundamentally, this looks more and more like a bug.
Either we need a LinkLocalAddressing=ipv6manual option or it should be 
checked, wether a valid scope local address is being provided later on.

But of course, I may be wrong

> On Mon, 5 Sept 2022, 19:14 Ede Wolf, <listac at nebelschwaden.de 
> <mailto:listac at nebelschwaden.de>> wrote:
> 
>     Am 05.09.22 um 18:34 schrieb Ede Wolf:
>      > Hello,
>      >
>      > For a simple setup, I've tried to replace radvd with systemds
>      > IPv6SendRA=true.
>      >
>      > Now the link supposed to send the RA of course has both a fixed
>     local as
>      > well as fixed global (ULA) address. As it happens to be the
>     default gw
>      > as well.
>      >
>      > Since the local address is being configured manually,
>      > LinkLocalAddressing is consequently set to no
>      >
>      >
>      > Now networkd complains, from the journal:
>      >
>      > IPv6PrefixDelegation= is enabled but IPv6 link-local addressing is
>      > disabled. Disabling IPv6PrefixDelegation=.
>      >
>      >
>      > Not sure what I am overlooking, but the SendRA is meant for other
>      > clients, not for this link. Otherwise I would have set
>     IPv6AcceptRA to
>      > true, not IPv6SendRA.
>      >
>      > What am I misinterpreting here?
>      >
>      > Thanks
>      >
>      > Ede
> 
>     I may have mixed up terms, something that, however, does not make
>     things
>     more comprehendable to me.
>     I am not using DHCPv6, I would just like to announce the prefix via RA
>     to other clients on that link. So prefix delegation is likely something
>     else. I've just concluded that from the journal message.
> 
>     However, my .network file has no DHCPv6 related stanzas:
> 
>     [Match]
>     Name=brlan
> 
>     [Link]
>     MACAddress=02:...
>     RequiredForOnline=yes
> 
>     [Network]
>     Description=Bridge
>     LinkLocalAddressing=no
>     IPForward=ipv4
>     IPForward=ipv6
>     IPv6AcceptRA=no
>     ConfigureWithoutCarrier=true
>     IgnoreCarrierLoss=true
>     DHCPServer=yes
>     IPv6AcceptRA=false
>     IPv6SendRA=true
> 
>     [Address]
>     Address=192.168.38.1/24 <http://192.168.38.1/24>
> 
>     [Address]
>     Address=fe80::38:1/64
>     Scope=link
> 
>     [Address]
>     Address=fde3:8b13:f1a5:38::1/64
>     Scope=global
> 
>     [DHCPServer]
>     PoolOffset=200
>     PoolSize=32
>     EmitNTP=yes
>     NTP=192.168.38.101
> 
>     [IPv6SendRA]
>     Managed=no
>     OtherInformation=no
> 
>     [IPv6Prefix]
>     AddressAutoconfiguration=true
>     Prefix=fde3:8b13:f1a5:38::/64
>