IP-based hostname concatenated with a string is not accepted.

[Karan]

When assigning a hostname like '206-141-40-41-os-compute' to a node using web interface, it is not accepted and a random hostname is used in place of user supplied hostname.

How to reproduce.

Try changing hostname to '206-141-40-41-os-compute' of a node through web interface.

 Output from dpkg -l '*maas*'|cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-===================================-=====================================-============-===============================================================================
ii maas 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS server all-in-one metapackage
ii maas-cli 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS command line API tool
ii maas-cluster-controller 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS server cluster controller
ii maas-common 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS server common files
ii maas-dhcp 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS DHCP server
ii maas-dns 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS DNS server
ii maas-proxy 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS Caching Proxy
ii maas-region-controller 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS server complete region controller
ii maas-region-controller-min 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS Server minimum region controller
ii python-django-maas 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS server Django web framework
ii python-maas-client 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS python API client
ii python-maas-provisioningserver 1.9.0+bzr4533-0ubuntu1~trusty1 all MAAS server provisioning libraries

I looked into code and found this is happening because IP-based hostnames are replaced by randomly generated hostname.
Replacing
IP_BASED_HOSTNAME_REGEXP = re.compile('\d{1,3}-\d{1,3}-\d{1,3}-\d{1,3}')
with
IP_BASED_HOSTNAME_REGEXP = re.compile('^\d{1,3}-\d{1,3}-\d{1,3}-\d{1,3}$') fixes this

File: maasserver/forms.pyc

class WithMACAddressesMixin:
...
...
def save(self):
        # Generate a hostname for this node if the provided hostname is
        # IP-based (because this means that this name comes from a DNS
        # reverse query to the MAAS DNS) or an empty string.
        generate_hostname = (
            hostname == "" or
            IP_BASED_HOSTNAME_REGEXP.match(stripped_hostname) is not None)
        if generate_hostname:
            node.set_random_hostname()

[Andres Rodriguez (andreserl)]

Hi Karan,

How are you trying to change the hostname?

[Karan (karan-pugla)]

I am doing it through MAAS dashboard

[Karan (karan-pugla)]

It works fine with CLI though.

[LaMont Jones (lamont)]

Any hostname that the user attempts to assign via the form, which starts with (re.match is anchored to start of string) something that matches '\d{1,3}-\d{1,3}-\d{1,3}-\d{1,3}' will be rejected by the form. This was introduced in october 2012. The fix is to change the regex to have the trailing "$".

[LaMont Jones (lamont)]

As a trivial workaround, prepending anything before the IP-based name also avoids the issue.