dhcpcd, IPv6 & DAD

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

I seem to be having a bit of bother getting a T60 laptop to get an IPv6 
address correctly using dhcpcd.

The basic setup I have is an ADSL router hardwired to a server 
(current-ish NetBSD amd64) which gets an ipv6 feed via a HE tunnel. The 
router hands out IPv4 addresses and the server uses rtadvd to hand out 
IPv6 prefixes etc.

The laptop is running a recent version of current:

NetBSD t60.anduin.org.uk 6.99.47 NetBSD 6.99.47 (GENERIC.201407190440Z) 
#0: Sat Jul 19 06:45:26 UTC 2014 
builds%b48.netbsd.org@localhost:/home/builds/ab/HEAD/i386/201407190440Z-obj/home/source/ab/HEAD/src/sys/arch/i386/compile/GENERIC 
i386

The networking parts of rc.conf:

wpa_supplicant=YES      wpa_supplicant_flags="-B -i wpi0 -c 
/etc/wpa_supplicant.conf"
dhcpcd=YES              dhcpcd_flags="-w"
ip6mode=host

and dhcpcd.conf is as supplied.

On startup dhcpcd seems to get both IPV4 and IPV6 addresses, but DAD 
fires off twice and the resulting
IPv6 address is marked as a duplicate. What I cannot understand is why 
this occurs and what I need to do to fix it...

rc.log:

Starting dhcpcd.
dhcpcd[151]: version 6.4.2 starting
dhcpcd[151]: wm0: adding address fe80::e26c:74d7:db55:bee7
dhcpcd[151]: wm0: waiting for carrier
dhcpcd[151]: wpi0: waiting for carrier
dhcpcd[151]: wpi0: carrier acquired
dhcpcd[151]: DUID 00:01:00:01:1b:6a:a0:37:00:13:02:7b:ca:44
dhcpcd[151]: wpi0: IAID 02:7b:ca:44
dhcpcd[151]: wpi0: soliciting a DHCP lease
dhcpcd[151]: wpi0: soliciting an IPv6 router
dhcpcd[151]: wpi0: Router Advertisement from fe80::1
dhcpcd[151]: wpi0: adding default route via fe80::1
dhcpcd[151]: wpi0: soliciting a DHCPv6 lease
dhcpcd[151]: wpi0: fe80::1 is unreachable, expiring it
dhcpcd[151]: wpi0: Router Advertisement from fe80::3e4a:92ff:fe77:bc6a
dhcpcd[151]: wpi0: adding address 2001:470:1f08:a8e:455e:1100:e823:ac03/64
dhcpcd[151]: wpi0: adding route to 2001:470:1f08:a8e::/64
dhcpcd[151]: wpi0: changing default route via fe80::3e4a:92ff:fe77:bc6a
dhcpcd[151]: wpi0: fe80::3e4a:92ff:fe77:bc6a is unreachable, expiring it
dhcpcd[151]: wpi0: DAD detected 2001:470:1f08:a8e:455e:1100:e823:ac03/64
dhcpcd[151]: wpi0: deleting address 2001:470:1f08:a8e:455e:1100:e823:ac03/64
dhcpcd[151]: wpi0: adding address 2001:470:1f08:a8e:da29:27e0:601b:993/64
dhcpcd[151]: wpi0: offered 192.168.0.10 from 192.168.0.1
dhcpcd[151]: wpi0: changing default route via fe80::1
dhcpcd[151]: wpi0: fe80::1 is unreachable, expiring it
dhcpcd[151]: wpi0: changing default route via fe80::3e4a:92ff:fe77:bc6a
dhcpcd[151]: wpi0: leased 192.168.0.10 for 86400 seconds
dhcpcd[151]: wpi0: adding host route to 192.168.0.10 via 127.0.0.1
dhcpcd[151]: wpi0: adding route to 192.168.0.0/24
dhcpcd[151]: wpi0: adding default route via 192.168.0.1
dhcpcd[151]: forked to background, child pid 788

and in the message log:

Jul 29 19:11:13 t60 /netbsd: wpi0: DAD detected duplicate IPv6 address 
2001:470:1f08:a8e:455e:1100:e823:ac03: NS in/out=1/1, NA in=0
Jul 29 19:11:13 t60 /netbsd: wpi0: DAD complete for 
2001:470:1f08:a8e:455e:1100:e823:ac03 - duplicate found
Jul 29 19:11:13 t60 /netbsd: wpi0: manual intervention required
Jul 29 19:11:13 t60 /netbsd: wpi0: DAD detected duplicate IPv6 address 
2001:470:1f08:a8e:da29:27e0:601b:993: NS in/out=1/1, NA in=0
Jul 29 19:11:13 t60 /netbsd: wpi0: DAD complete for 
2001:470:1f08:a8e:da29:27e0:601b:993 - duplicate found
Jul 29 19:11:13 t60 /netbsd: wpi0: manual intervention required

Anyone got an idea of what to do?

TIA,
Dave

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