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Re: nd6_na_input: duplicate IP6 address



On 06/05/2019 00:35, Mike Pumford wrote:
On 06/05/2019 00:21, Roy Marples wrote:

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.

So this seems to suggest that the machine thinks there is another host on the same network that has the same IP?

If so that's very odd because almost all of my machines are using auto assigned addresses based on MAC address and the ones with static addresses haven't moved for ages.

There are many situations where the NS/NA packets get looped back into the origination node, causing these false positives. I added RFC 7527 support to NetBSD over a year ago which will debut in NetBSD-9.0. This adds a nonce to the DAD packets to ensure looped back DAD packets can easily be ignored.

So from NetBSD-9.0 onwards you won't see those messages, unless a node really is using your IP address!

Hope this helps

Roy


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