Bogus hostname 14.LL created when dhcp config has multiple MAC addresses

[DanaGoyette]

I have some dhcp configs with multiple mac addresses, and it results in a bogus hostname record of 14.LL.home (where home) is the configured domain.

From /etc/config/dhcp:

config host
        option dns '1'
        option name 'server10g'
        option ip '192.168.1.51'
        option mac '<mac1> <mac2>'

In /tmp/ip6neigh.cache, I see this: <mac1> <mac2> 14 server10g
So, 14 is picked up as the name.

[cvmiller]

This does appear to be a parsing error by ip6neigh.

But I am curious, what is the use case for a host having 2 MAC addresses, but only 1 IP address? I would think this would thrash your ARP cache, or at a minimum set you up for a duplicate IP address on your network.

[DanaGoyette]

In my use case, I was using it when I have several NICs (two 1G ports and two 10G ports) on a machine, and I want to be able to troubleshoot things by moving the cable around. I have one name + ip for the 1G pair, and a different name + ip for the 10G pair.

[DanaGoyette]

I found another case where I end up having to have two MAC address entries on one host:
option mac 'e4:5f:01:f7:6f:34 id:01:e4:5f:01:f7:6f:34'

[cvmiller]

I found another case where I end up having to have two MAC address entries on one host: option mac 'e4:5f:01:f7:6f:34 id:01:e4:5f:01:f7:6f:34'

Isn't this the same use case, or are both the MACs active at the same time?

[DanaGoyette]

That's actually the same machine and same NIC twice… it seems like depending on OS, sometimes it sends a dhcp-client-id (the id:01:…) and sometimes doesn't (the plain MAC address). So, I need both to reserve it properly.

I have a couple of hosts where I've done that to make sure the reservation works.

It seems like ip6neigh stops adding a bogus hostname record if I swap the order so the id: is first.