IPv6 addresses in bridge mode do not automatically configure IP

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Wybert Yonge

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Jul 20, 2021, 11:18:50 PM7/20/21
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Using Bridge's interface, virt-launcher pod will not create an IPv6 DHCP server so that the virtual machine cannot get the IP via DHCP. Why not start a DHCP server using the same mode as Masquerade?

Marcus S

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Sep 3, 2021, 2:46:53 PM9/3/21
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Yes, I was just looking at that. In the case where the pod gets a native V6 address, all of the plumbing seems to work if I manually configure the VM with the pod's assigned IP, but it doesn't seem we have the DHCP being advertised yet in Kubevirt, is that right?

Petr Horacek

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Sep 6, 2021, 3:22:27 AM9/6/21
to Marcus S, kubevirt-dev
Correct, unlike with IPv4, there is no DHCP server in virt-launcher that would serve the guest with the IP. You really have to configure it manually or via cloud init: https://kubevirt.io/user-guide/virtual_machines/interfaces_and_networks/#masquerade-ipv4-and-ipv6-dual-stack-support

pá 3. 9. 2021 v 20:47 odesílatel Marcus S <shad...@gmail.com> napsal:
Yes, I was just looking at that. In the case where the pod gets a native V6 address, all of the plumbing seems to work if I manually configure the VM with the pod's assigned IP, but it doesn't seem we have the DHCP being advertised yet in Kubevirt, is that right?

On Tuesday, July 20, 2021 at 9:18:50 PM UTC-6 youzh...@gmail.com wrote:
Using Bridge's interface, virt-launcher pod will not create an IPv6 DHCP server so that the virtual machine cannot get the IP via DHCP. Why not start a DHCP server using the same mode as Masquerade?

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Edward Haas

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Sep 6, 2021, 4:14:59 AM9/6/21
to Petr Horacek, Marcus S, kubevirt-dev
On Mon, Sep 6, 2021 at 10:22 AM Petr Horacek <phor...@redhat.com> wrote:
Correct, unlike with IPv4, there is no DHCP server in virt-launcher that would serve the guest with the IP. You really have to configure it manually or via cloud init: https://kubevirt.io/user-guide/virtual_machines/interfaces_and_networks/#masquerade-ipv4-and-ipv6-dual-stack-support

I think the documentation is not up-to-date.
This is only true for bridge binding, but for masquerade I think it should work.


pá 3. 9. 2021 v 20:47 odesílatel Marcus S <shad...@gmail.com> napsal:
Yes, I was just looking at that. In the case where the pod gets a native V6 address, all of the plumbing seems to work if I manually configure the VM with the pod's assigned IP, but it doesn't seem we have the DHCP being advertised yet in Kubevirt, is that right?

On Tuesday, July 20, 2021 at 9:18:50 PM UTC-6 youzh...@gmail.com wrote:
Using Bridge's interface, virt-launcher pod will not create an IPv6 DHCP server so that the virtual machine cannot get the IP via DHCP. Why not start a DHCP server using the same mode as Masquerade?

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Marcus S

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Oct 6, 2021, 1:30:53 PM10/6/21
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On Monday, September 6, 2021 at 2:14:59 AM UTC-6 Edward Haas wrote:
On Mon, Sep 6, 2021 at 10:22 AM Petr Horacek <phor...@redhat.com> wrote:
Correct, unlike with IPv4, there is no DHCP server in virt-launcher that would serve the guest with the IP. You really have to configure it manually or via cloud init: https://kubevirt.io/user-guide/virtual_machines/interfaces_and_networks/#masquerade-ipv4-and-ipv6-dual-stack-support

I think the documentation is not up-to-date.
This is only true for bridge binding, but for masquerade I think it should work.

Yes, I think that's the original question. Now that there is a DHCPv6 server, it seems we would be farther along to supporting DHCP with bridge mode, perhaps.

Petr Horacek

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Oct 7, 2021, 3:49:25 AM10/7/21
to Marcus S, kubevirt-dev


st 6. 10. 2021 v 19:31 odesílatel Marcus S <shad...@gmail.com> napsal:


On Monday, September 6, 2021 at 2:14:59 AM UTC-6 Edward Haas wrote:
On Mon, Sep 6, 2021 at 10:22 AM Petr Horacek <phor...@redhat.com> wrote:
Correct, unlike with IPv4, there is no DHCP server in virt-launcher that would serve the guest with the IP. You really have to configure it manually or via cloud init: https://kubevirt.io/user-guide/virtual_machines/interfaces_and_networks/#masquerade-ipv4-and-ipv6-dual-stack-support

I think the documentation is not up-to-date.
This is only true for bridge binding, but for masquerade I think it should work.

Unfortunately, I do not think the RA implementation on the masquerade binding was finished, so even though you may have DHCPv6, it would still require some manual steps. Keep me honest here.

 

Yes, I think that's the original question. Now that there is a DHCPv6 server, it seems we would be farther along to supporting DHCP with bridge mode, perhaps.

I don't think there are reasons against it, but it is a capacity problem. Finishing the RA support and extending both DHCPv6 and RA to bridge binding would require a big amount of work.

Just out of curiosity, you would like to use this for bridge mode on the Pod network or Multus?
 

 


pá 3. 9. 2021 v 20:47 odesílatel Marcus S <shad...@gmail.com> napsal:
Yes, I was just looking at that. In the case where the pod gets a native V6 address, all of the plumbing seems to work if I manually configure the VM with the pod's assigned IP, but it doesn't seem we have the DHCP being advertised yet in Kubevirt, is that right?

On Tuesday, July 20, 2021 at 9:18:50 PM UTC-6 youzh...@gmail.com wrote:
Using Bridge's interface, virt-launcher pod will not create an IPv6 DHCP server so that the virtual machine cannot get the IP via DHCP. Why not start a DHCP server using the same mode as Masquerade?

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Alona Paz

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Oct 7, 2021, 4:15:15 AM10/7/21
to Marcus S, kubevirt-dev
On Wed, Oct 6, 2021 at 8:31 PM Marcus S <shad...@gmail.com> wrote:


On Monday, September 6, 2021 at 2:14:59 AM UTC-6 Edward Haas wrote:
On Mon, Sep 6, 2021 at 10:22 AM Petr Horacek <phor...@redhat.com> wrote:
Correct, unlike with IPv4, there is no DHCP server in virt-launcher that would serve the guest with the IP. You really have to configure it manually or via cloud init: https://kubevirt.io/user-guide/virtual_machines/interfaces_and_networks/#masquerade-ipv4-and-ipv6-dual-stack-support

I think the documentation is not up-to-date.
This is only true for bridge binding, but for masquerade I think it should work.

For masquerade we indeed have a DHCPv6 server. But DHCPv6 server is not enough to get all the required IPv6 info. RA, which is currently not supported, is needed as well.
If a DHCP request is sent from the vm (since there is no RA it won't automatically happen, it can be manually invoked by for example - `dhclient -6 eth0`), the existing DHCPv6 server will reply to this request and the IPv6 address will be configured on the VM interface. However, the routes have to be manually configured. An example can be found in this test -https://github.com/kubevirt/kubevirt/blob/main/tests/network/vmi_networking.go#L657
 

Yes, I think that's the original question. Now that there is a DHCPv6 server, it seems we would be farther along to supporting DHCP with bridge mode, perhaps.

Currently, bridge binding on the primary interface doesn't support ipv6 at all. Not even manually.
 

 


pá 3. 9. 2021 v 20:47 odesílatel Marcus S <shad...@gmail.com> napsal:
Yes, I was just looking at that. In the case where the pod gets a native V6 address, all of the plumbing seems to work if I manually configure the VM with the pod's assigned IP, but it doesn't seem we have the DHCP being advertised yet in Kubevirt, is that right?

On Tuesday, July 20, 2021 at 9:18:50 PM UTC-6 youzh...@gmail.com wrote:
Using Bridge's interface, virt-launcher pod will not create an IPv6 DHCP server so that the virtual machine cannot get the IP via DHCP. Why not start a DHCP server using the same mode as Masquerade?

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