Conflicting sysnames cause ipdevpoll jobs to crash

[Morten Brekkevold]

If two IP Devices in NAV resolve to the same DNS name, any ipdevpoll job that runs the dnsname plugin will fail for one of the devices.

A typical situation where this happens is when the same multi-homed device has been added under multiple IP addresses in NAV (or where a DNS misconfiguration has two PTR records pointing two different IP addresses to the same name).

The ipdevpoll failure occurs because it naively attempts to store the new sysname, but a database constraint that requires unique sysnames will cause it to crash with a unhandled integrity error.

ipdevpoll should verify that there is no conflict before setting a new sysname from DNS. If there is a conflict, it should set the device's IP Address as its new sysname (which is what also happens if no DNS records could be found at all).

[Morten Brekkevold (mbrekkevold)]

fix here: https://nav.uninett.no/hg/stable/rev/9da7820ee876