dhcp-agent network namespace does not have a default route, can't use upstream dns

[Trevor Adams]

The network namespace that dnsmasq runs in does not have a default route on creation (to the router for that network) and as such trying to use an upstream nameserver fails.

root@somehost# for i in $(ip netns | grep dhcp); do ip netns exec $i route -n; done
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.137.0 0.0.0.0 255.255.255.0 U 0 0 0 tap1a7c6129-07
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.224.0 0.0.0.0 255.255.255.0 U 0 0 0 tap43bd32a8-82
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.225.0 0.0.0.0 255.255.255.0 U 0 0 0 tap01947148-b2
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 10.0.129.1 0.0.0.0 UG 0 0 0 tapb4f816ac-a4
10.0.129.0 0.0.0.0 255.255.255.0 U 0 0 0 tapb4f816ac-a4
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.10.0 0.0.0.0 255.255.255.0 U 0 0 0 tapb5919ca3-bc

I have added the default route on only 1 of the namespaces, the 10.0.129.0/24 one but all others do not have them and can therefore not resolve their upstream servers.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/31533

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/31533
Committed: http://github.com/openstack/quantum/commit/5dd0cf15463e181b92c8809c2dcc7603bb156a0e
Submitter: Jenkins
Branch: master

commit 5dd0cf15463e181b92c8809c2dcc7603bb156a0e
Author: Carl Baldwin <email address hidden>
Date: Fri May 31 20:44:14 2013 +0000

    Adds default route to DHCP namespace for upstream name resolution.

    Any time the DHCP server is updated this code will maintain a default
    route in the DHCP namespace using the gateway_ip attribute of the
    first DHCP-enabled IPV4 subnet in the list of subnets where gateway_ip
    is not None. This strategy uses the same gateway ip that the DHCP
    server hands to the VMs on the network.

    Change-Id: I0807550a848e1b610c7775d215643ad9c83629ed
    Fixes: Bug #1181378

[Jacob Godin (jacobgodin)]

Could this be back-ported into Grizzly as well?

[Kevin Bringard (kbringard)]

+1 for backport to grizzly

[John Dewey (retr0h)]

I agree with @Jacob. We see this exact problem in Grizzly and would love it back ported.

[Alan Meadows (alan-meadows)]

Backport would be very helpful.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/grizzly
Review: https://review.openstack.org/42247

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/42247
Committed: http://github.com/openstack/neutron/commit/a150dc668925ddccc2d4a8fa3001a1ba3bf19c36
Submitter: Jenkins
Branch: stable/grizzly

commit a150dc668925ddccc2d4a8fa3001a1ba3bf19c36
Author: Carl Baldwin <email address hidden>
Date: Fri May 31 20:44:14 2013 +0000

    Adds default route to DHCP namespace for upstream name resolution.

    Any time the DHCP server is updated this code will maintain a default
    route in the DHCP namespace using the gateway_ip attribute of the
    first DHCP-enabled IPV4 subnet in the list of subnets where gateway_ip
    is not None. This strategy uses the same gateway ip that the DHCP
    server hands to the VMs on the network.

    Fixes: Bug #1181378

    Conflicts:

     quantum/agent/dhcp_agent.py

    Change-Id: I0807550a848e1b610c7775d215643ad9c83629ed
    (cherry picked from commit 5dd0cf15463e181b92c8809c2dcc7603bb156a0e)