[Dnsmasq-discuss] WG: clients of DHCPv6 with constructed IPv6 address range are not notified on address range change

[Andrey Vakhitov]

Hi Simon,

>> I've set it up as you suggested, initially name resolution seems to 
>> work fine. But after some days of operation (and some nightly 
>> reconnects) dnsmasq seems to loose associated IPv6 adresses: DNS 
>> request reports only IPv6 address assigned via DHCP. The SLAAC-based 
>> IPv6 addresses on hosts are present and correct. How can I investigate
and fix this issue?

> Look in the log for lines that look like
>
> DHCPv4-derived IPv6 names on ........
>
> which should occur after a reconnect with a different address which causes
new DHCP address ranges to be constructed.
>
> After that happens, dnsmasq will take a guess at the IPv6 addresses that
hosts will assign themselves, 
> based on the network address and the MAC address of the host (transformed
into EUI-64) 
> It then starts to ping those addresses, and when it gets a reply, it will
log
>
> SLAAC_CONFIRM(interface) <address> <hostname>
>
> and start using the address/name in the DNS.
>
> Once confirmed, the addresses remain valid until the DHCPv4 lease it's
based on expires or goes 
> though init-reboot state or the MAC address or interface it's accessible
by changes.
>
> The only other thing that will delete these addresses in a new address
appearing and a new dhcp 
> range being created, hence it's interesting to look at what happens in the
logs after each of those events.

Strange thing: sometimes after reconnect I can observe expected behaviour
(like you described it, see log 1), sometimes not (SLAAC-CONFIRM is missing,
see log 2)

---------- log1 --------
Sep 17 20:22:45 rtr dnsmasq-dhcp[7855]: DHCPv6 stateless on
2001:16b8:2284:f5fc::, constructed for lan0
Sep 17 20:22:45 rtr dnsmasq-dhcp[7855]: DHCPv4-derived IPv6 names on
2001:16b8:2284:f5fc::, constructed for lan0
Sep 17 20:22:45 rtr dnsmasq-dhcp[7855]: router advertisement on
2001:16b8:2284:f5fc::, constructed for lan0
Sep 17 20:22:45 rtr dnsmasq-dhcp[7855]: DHCPv6 stateless on
2001:16b8:2284:f5fd::, constructed for dmz0
Sep 17 20:22:45 rtr dnsmasq-dhcp[7855]: DHCPv4-derived IPv6 names on
2001:16b8:2284:f5fd::, constructed for dmz0
Sep 17 20:22:45 rtr dnsmasq-dhcp[7855]: router advertisement on
2001:16b8:2284:f5fd::, constructed for dmz0
Sep 17 20:22:45 rtr dnsmasq[7855]: reading /etc/dnsmasq-resolv.conf
Sep 17 20:22:45 rtr dnsmasq[7855]: using local addresses only for domain
homenet
Sep 17 20:22:45 rtr dnsmasq[7855]: using nameserver 8.8.4.4#53
Sep 17 20:22:45 rtr dnsmasq[7855]: using nameserver 8.8.8.8#53
Sep 17 20:22:45 rtr dnsmasq[7855]: ignoring nameserver
fd00::7eff:4dff:fe03:2c18 - cannot make/bind socket: Address alr>
Sep 17 20:22:45 rtr dnsmasq[7855]: setting upstream servers from DBus
Sep 17 20:22:45 rtr dnsmasq[7855]: using local addresses only for domain
homenet
Sep 17 20:22:45 rtr dnsmasq[7855]: using nameserver 8.8.4.4#53
Sep 17 20:22:45 rtr dnsmasq[7855]: using nameserver 8.8.8.8#53
Sep 17 20:22:47 rtr dhcpcd[15081]: lan0: DHCPv6 DAD completed
Sep 17 20:22:47 rtr dhcpcd[15081]: lan0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' DELEGATED6
Sep 17 20:22:47 rtr dhcpcd[15081]: dmz0: DHCPv6 DAD completed
Sep 17 20:22:47 rtr dhcpcd[15081]: dmz0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' DELEGATED6
Sep 17 20:22:49 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 17 20:22:55 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 17 20:22:56 rtr dhcpcd[15081]: wan0: fe80::7eff:4dff:fe03:2c18 is
unreachable, expiring it
Sep 17 20:22:56 rtr dhcpcd[15081]: wan0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' ROUTERADVERT
Sep 17 20:22:58 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2284:f5fc::
Sep 17 20:22:58 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2250:65f8:: old prefix
Sep 17 20:22:58 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 17 20:22:59 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2284:f5fd::
Sep 17 20:22:59 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2250:65f9:: old prefix
Sep 17 20:23:03 rtr dnsmasq-dhcp[7855]: SLAAC-CONFIRM(lan0)
2001:16b8:2284:f5fc:d250:99ff:fe84:93d0 vdrmain
Sep 17 20:23:03 rtr dnsmasq-dhcp[7855]: SLAAC-CONFIRM(dmz0)
2001:16b8:2284:f5fd:5054:ff:fe12:3456 dmzhost
Sep 17 20:23:03 rtr dhcpcd[15081]: wan0: fe80::7eff:4dff:fe03:2c18 is
reachable again
Sep 17 20:23:03 rtr dhcpcd[15081]: wan0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' ROUTERADVERT
Sep 17 20:23:05 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2284:f5fd::
Sep 17 20:23:05 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2250:65f9:: old prefix
Sep 17 20:23:05 rtr dnsmasq-dhcp[7855]: SLAAC-CONFIRM(lan0)
2001:16b8:2284:f5fc:222:4dff:fea7:dcdc vdrkit
Sep 17 20:23:05 rtr dnsmasq-dhcp[7855]: SLAAC-CONFIRM(lan0)
2001:16b8:2284:f5fc:fca1:42ff:fed2:a2bd xenhost
-------------------------

---------- log2 --------
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPv6 stateless on
2001:16b8:22c4:83fc::, constructed for lan0
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPv4-derived IPv6 names on
2001:16b8:22c4:83fc::, constructed for lan0
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: router advertisement on
2001:16b8:22c4:83fc::, constructed for lan0
Sep 18 04:35:20 rtr dhcpcd[15081]: lan0: waiting for DHCPv6 DAD to complete
Sep 18 04:35:20 rtr dhcpcd[15081]: dmz0: adding address
2001:16b8:22c4:83fd::1/64
Sep 18 04:35:20 rtr dhcpcd[15081]: dmz0: pltime 3600 seconds, vltime 7200
seconds
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPv6 stateless on
2001:16b8:22c4:83fd::, constructed for dmz0
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPv4-derived IPv6 names on
2001:16b8:22c4:83fd::, constructed for dmz0
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: router advertisement on
2001:16b8:22c4:83fd::, constructed for dmz0
Sep 18 04:35:20 rtr dhcpcd[15081]: dmz0: waiting for DHCPv6 DAD to complete
Sep 18 04:35:20 rtr dhcpcd[15081]: lan0: adding route to
2001:16b8:22c4:83fc::/64
Sep 18 04:35:20 rtr dhcpcd[15081]: dmz0: adding route to
2001:16b8:22c4:83fd::/64
Sep 18 04:35:20 rtr dhcpcd[15081]: wan0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' BOUND6
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:35:20 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:20 rtr dhcpcd[15081]: wan0: Router Advertisement DAD completed
Sep 18 04:35:20 rtr dhcpcd[15081]: wan0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' ROUTERADVERT
Sep 18 04:35:21 rtr ddclient[1597]: SUCCESS:  updating rtrhomevak.spdns.de:
good: IP address set to 2001:16b8:22c4:8300>
Sep 18 04:35:21 rtr dhcpcd[15081]: dmz0: DHCPv6 DAD completed
Sep 18 04:35:21 rtr dhcpcd[15081]: dmz0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' DELEGATED6
Sep 18 04:35:21 rtr dhcpcd[15081]: lan0: DHCPv6 DAD completed
Sep 18 04:35:21 rtr dhcpcd[15081]: lan0: executing
`/usr/lib/dhcpcd/dhcpcd-run-hooks' DELEGATED6
Sep 18 04:35:29 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:29 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:29 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:29 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:31 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:35:31 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:35:31 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:34 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:35:36 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:36 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:36 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:36 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:42 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:42 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:42 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:42 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:43 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:35:43 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:35:43 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:35:44 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:44 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:44 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:44 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:48 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:35:48 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:35:48 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:35:51 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:35:51 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:35:51 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:35:54 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:54 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:54 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:35:54 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:35:54 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:35:54 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:35:58 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:35:58 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:35:58 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:36:00 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:36:00 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:36:00 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:36:01 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:36:01 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
Sep 18 04:36:01 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:ee:62:d8:4d:ca:9f:9d:d5
Sep 18 04:36:01 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(lan0)
00:02:00:00:ab:11:d5:97:98:17:01:41:27:3e
Sep 18 04:36:08 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:22c4:83fd::
Sep 18 04:36:08 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(dmz0)
2001:16b8:2285:3afd:: old prefix
Sep 18 04:36:08 rtr dnsmasq-dhcp[7855]: DHCPINFORMATION-REQUEST(dmz0)
00:02:00:00:ab:11:9b:74:21:c0:e9:5d:1c:18
Sep 18 04:36:10 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:22c4:83fc::
Sep 18 04:36:10 rtr dnsmasq-dhcp[7855]: RTR-ADVERT(lan0)
2001:16b8:2285:3afc:: old prefix
-------------------------

Best Regards,
--
Andrey Vakhitov

E-Mail:  andrey at vakhitov.net            Stuttgart, Germany