Re: nd6_na_input: duplicate IP6 address

[Roy Marples <roy%marples.name@localhost>]

Hi Mike

On 06/05/2019 00:00, Mike Pumford wrote:
> Seeing a lot of these messages coming from the kernel after my update to 
> the latest 8.0-STABLE branch (as of yesterday morning)
>
> nd6_na_input: duplicate IP6 address <IPv6 address of machine>
>
> First one appears when booting just after printing duplicate detection.
>
> Network interface is:
> wm0 at pci0 dev 25 function 0: I218 V Ethernet Connection (rev. 0x00)
> wm0: interrupting at msi2 vec 0
> wm0: PCI-Express bus
> wm0: 2048 words FLASH
> wm0: Ethernet address 10:c3:7b:95:20:ed
> wm0: 0x2a4480<FLASH,IOH_VALID,PCIE,ASF_FIRM,AMT,WOL>
> ihphy0 at wm0 phy 2: i217 10/100/1000 media interface, rev. 5
>
> This is using dhcpd with default config apart from the fact that I've 
> disabled slaac private and enabled slaac hwaddr
>
> Another machine on the same network with a static V6 address does not 
> see these message when running the same kernel.
>
> It doesn't seem to impact v6 connectivity as far as I can tell.

Looking at the -8 kernel code, it will print this message before 
deciding on a course of action.

As it's not impacted v6 connectivity - and you can verify by ifconfig 
that no address is duplicated, then the kernel is notifying another node 
that it's address is the dupliate and not yours.

The other machine won't see this because it's using a different address.

We should probably fix the kernel messages to at least print the lla of 
the other node to help debugging.

Roy