dnsmasq doesn't listen for DNS queries to its global IPv6 address
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| neutron |
New
|
Undecided
|
Unassigned | ||
Bug Description
On Kilo, when setting up an IPv6 subnet with DHCP enabled, the qdhcp namespace on the l3 agents will acquire global IPv6 addresses from the subnet prefix. These addresses are also advertised to instances requesting DNS servers via DHCPv6. However, dnsmasq does not listen for incoming DNS queries to these addresses (it only listens queries sent to its link-local IPv4 and IPv6 addresses). The end result is that the instances are provisioned with a set of DNS servers which simply does not work, and therefore cannot resolve any hostnames. The console output below should help explain the issue:
Creating the network/subnet and attaching it to Internet router:
-------
tore@ctrl01:~$ neutron net-create foobarnet
Created a new network:
+------
| Field | Value |
+------
| admin_state_up | True |
| id | a125a5a5-
| mtu | 0 |
| name | foobarnet |
| router:external | False |
| shared | False |
| status | ACTIVE |
| subnets | |
| tenant_id | ebeb8cab76e94d1
+------
tore@ctrl01:~$ neutron subnet-create --ip-version 6 --ipv6-ra-mode dhcpv6-stateless --ipv6-address-mode dhcpv6-stateless foobarnet 2a02:c0:
Created a new subnet:
+------
| Field | Value |
+------
| allocation_pools | {"start": "2a02:c0:
| cidr | 2a02:c0:
| dns_nameservers | |
| enable_dhcp | True |
| gateway_ip | 2a02:c0:200:f02f::1 |
| host_routes | |
| id | 9f8d4190-
| ip_version | 6 |
| ipv6_address_mode | dhcpv6-stateless |
| ipv6_ra_mode | dhcpv6-stateless |
| name | |
| network_id | a125a5a5-
| subnetpool_id | |
| tenant_id | ebeb8cab76e94d1
+------
tore@ctrl01:~$ neutron router-
Added interface 40544ba9-
Network node 01 status:
-------
tore@net01:~$ sudo ip netns exec qdhcp-a125a5a5-
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
94: tapd21c1dc1-bd: <BROADCAST,
link/ether fa:16:3e:8a:82:5e brd ff:ff:ff:ff:ff:ff
inet 169.254.169.254/16 brd 169.254.255.255 scope global tapd21c1dc1-bd
valid_lft forever preferred_lft forever
inet6 2a02:c0:
valid_lft 86398sec preferred_lft 14398sec
inet6 fe80::f816:
valid_lft forever preferred_lft forever
tore@net01:~$ sudo ip netns exec qdhcp-a125a5a5-
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dnsmasq 12789 nobody 7u IPv4 88487703 0t0 UDP 169.254.
dnsmasq 12789 nobody 8u IPv4 88487704 0t0 TCP 169.254.
dnsmasq 12789 nobody 12u IPv6 88590343 0t0 UDP [fe80::
dnsmasq 12789 nobody 13u IPv6 88590344 0t0 TCP [fe80::
Network node 02 status:
-------
tore@net02:~$ sudo ip netns exec qdhcp-a125a5a5-
1: lo: <LOOPBACK,
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
94: tap0d726e47-80: <BROADCAST,
link/ether fa:16:3e:7a:29:4d brd ff:ff:ff:ff:ff:ff
inet 169.254.169.254/16 brd 169.254.255.255 scope global tap0d726e47-80
valid_lft forever preferred_lft forever
inet6 2a02:c0:
valid_lft 86400sec preferred_lft 14400sec
inet6 fe80::f816:
valid_lft forever preferred_lft forever
tore@net02:~$ sudo ip netns exec qdhcp-a125a5a5-
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dnsmasq 17217 nobody 7u IPv4 65048317 0t0 UDP 169.254.
dnsmasq 17217 nobody 8u IPv4 65048318 0t0 TCP 169.254.
dnsmasq 17217 nobody 12u IPv6 65047373 0t0 UDP [fe80::
dnsmasq 17217 nobody 13u IPv6 65047374 0t0 TCP [fe80::
Testing resolving hostnames on network node 02:
-------
tore@net02:~$ sudo ip netns exec qdhcp-a125a5a5-
Using domain server:
Name: 169.254.169.254
Address: 169.254.169.254#53
Aliases:
launchpad.net has address 91.189.89.222
launchpad.net has address 91.189.89.223
launchpad.net mail is handled by 10 mx.launchpad.net.
tore@net02:~$ sudo ip netns exec qdhcp-a125a5a5-
Using domain server:
Name: fe80::f816:
Address: fe80::f816:
Aliases:
launchpad.net has address 91.189.89.223
launchpad.net has address 91.189.89.222
launchpad.net mail is handled by 10 mx.launchpad.net.
tore@net02:~$ sudo ip netns exec qdhcp-a125a5a5-
;; connection timed out; no servers could be reached
Are you 100% certain that bug #1498665 is a duplicate of this one?
From its description, it is not - that bug relates to IPv6 host entries belonging to the instances being written into the lease databases, while this bug is about dnsmasq not listening for DNS queries coming in over IPv6 to the addresses assigned to its own router:dhcp ports (because it explicitly binds its listening AF_INET6 socket to its link-local IPv6 addresses only).
Tore