Masternode works incorrectly when additional interface with DHCP configured

[Aleksandr Shaposhnikov]

If masternode will have an additional interface (beside eth0) with DHCP configured then after reboot masternode using DNS servers from this DHCP interface and will not configure local DNS server to use. So after the restart ability to go on nodes by names, node-* mask will disappear.

How to reproduce:

1. Install masternode with at least two interfaces and for simplifying second interface should be connected to some network with DHCP server (usually it's kind of administrative network). After masternode will complete the installation reboot it and try to boot up some nodes.
2. Provision and deploy any openstack variant and try to ssh to any of the nodes using name (node-*, controller-* and so on). You wouldn't be able to do that.

[Sergii Golovatiuk (sgolovatiuk)]

What you describe is a normal behavior when you have several DHCP clients. However, Fuel has several techniques such as dhcp-enter-hooks. By normal circumstances it shouldn't allow to overwrite /etc/resolv.conf even if you have dhcp enabled for some interfaces.

https://github.com/stackforge/fuel-library/blob/master/deployment/puppet/nailgun/manifests/host.pp#L54

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/103932

[Aleksandr Shaposhnikov (alashai8)]

Hi Sergey,

There is no word about multiple DHCP client. One network is static by default (10.20.0/24) and another one where masternode acts as DHCP client.
Btw even in case with multiple dhcp clients this problem with DNS is solvable. We only need to keep our own DNS server as source for all dns-related queries about our nodes.

Thanks!

[Sergii Golovatiuk (sgolovatiuk)]

Hi Aleksandr,

Fuel master node uses resolv.conf where internal resolver is specified. It means that there are at least 2 dhcp servers (internal and external). Technically, settings of master node shouldn't allow to overwrite resolv.conf. It seemed to happen in your case. I've submitted patch that should explicitly set priority.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/103932
Committed: https://git.openstack.org/cgit/stackforge/fuel-library/commit/?id=6a7be9241b5a416f30f7f569b78537915152ced3
Submitter: Jenkins
Branch: master

commit 6a7be9241b5a416f30f7f569b78537915152ced3
Author: Sergii Golovatiuk <email address hidden>
Date: Tue Jul 1 15:57:46 2014 +0000

    Create dhclient.conf, set priority for nailgun DNS

    When there are couple of DHCP server, nailgun server will be set first resolv.conf

    Change-Id: I4077072f38ea445d065e9e49d91a909062529dcf
    Closes-bug: 1335210

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/5.0
Review: https://review.openstack.org/104169

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/104169
Committed: https://git.openstack.org/cgit/stackforge/fuel-library/commit/?id=21f5c08008f4c30c7e8cfc3318af3f321a6560cc
Submitter: Jenkins
Branch: stable/5.0

commit 21f5c08008f4c30c7e8cfc3318af3f321a6560cc
Author: Sergii Golovatiuk <email address hidden>
Date: Tue Jul 1 15:57:46 2014 +0000

    Create dhclient.conf, set priority for nailgun DNS

    When there are couple of DHCP server, nailgun server will be set first resolv.conf

    Change-Id: I4077072f38ea445d065e9e49d91a909062529dcf
    Closes-bug: 1335210