in6_pfx_newpersistaddr: %s is already configured

[Tore Anderson]

* Jared Mauch

> Anyone seen these logs on their machines?
> 
> I get a fairly consistent set of syslogs on my machines (MacOS 10.9) each time I get a RA from my cable modem.
> 
> 14:18:13.209477 20:e5:2a:b8:10:cf > 33:33:00:00:00:01, ethertype IPv6 (0x86dd), length 174: (hlim 255, next-header ICMPv6 (58) payload length: 120) fe80::22e5:2aff:feb8:10cf > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 120
> 	hop limit 64, Flags [managed, other stateful], pref medium, router lifetime 1800s, reachable time 0s, retrans time 0s
> 	  source link-address option (1), length 8 (1): 20:e5:2a:b8:10:cf
> 	    0x0000:  20e5 2ab8 10cf
> 	  prefix info option (3), length 32 (4): 2601:4:2180:300::/64, Flags [onlink, auto], valid time 345600s, pref. time 345600s
> 	    0x0000:  40c0 0005 4600 0005 4600 0000 0000 2601
> 	    0x0010:  0004 2180 0300 0000 0000 0000 0000
> 	  unknown option (24), length 24 (3): 
> 	    0x0000:  3800 0005 4600 2601 0004 2180 0300 0000
> 	    0x0010:  0000 0000 0000
> 	  rdnss option (25), length 40 (5):  lifetime 1200s, addr: 2001:558:feed::2 addr: 2001:558:feed::1
> 	    0x0000:  0000 0000 04b0 2001 0558 feed 0000 0000
> 	    0x0010:  0000 0000 0002 2001 0558 feed 0000 0000
> 	    0x0020:  0000 0000 0001
> 
> Dec  3 14:57:43 Jareds-NTT-iMac kernel[0]: in6_pfx_newpersistaddr: 2601:4:2180:300:426c:8fff:fe33:d4b0 is already configured!
> Dec  3 14:58:13 Jareds-NTT-iMac kernel[0]: in6_pfx_newpersistaddr: 2601:4:2180:300:426c:8fff:fe33:d4b0 is already configured!
> Dec  3 14:58:43 Jareds-NTT-iMac kernel[0]: in6_pfx_newpersistaddr: 2601:4:2180:300:426c:8fff:fe33:d4b0 is already configured!
> Dec  3 14:59:13 Jareds-NTT-iMac kernel[0]: in6_pfx_newpersistaddr: 2601:4:2180:300:426c:8fff:fe33:d4b0 is already configured!
> Dec  3 14:59:43 Jareds-NTT-iMac kernel[0]: in6_pfx_newpersistaddr: 2601:4:2180:300:426c:8fff:fe33:d4b0 is already configured!
> 
> I'm trying to diagnose if this is related to a problem I'm seeing as well.

I haven't seen these myself (I don't have anything running Mac OS), but
the fact that the "managed" flag is set reminds me of a strange
behaviour I saw from a Cisco EPC3928 cable modem. It would give out
DHCPv6 IA_NA leases that was based on the client's MAC address using
EUI-64, in other words it would give out the exact same address as the
client would auto-configure itself with using SLAAC. I see you have a
Netgear, but if it behaves in the same way as my Cisco ... well, it
would make the "is already configured" message make some sense as it
probably got that address from DHCPv6 and so the SLAAC code would
probably fail to add it (again).

Tore