regular expression to detect ipv4 IP address

[Brian Julin]

Alex Sharaz <alex.sharaz at york.ac.uk> wrote:

>> ipv4_regexp = '^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$'
>> but am getting

>> Thu Sep  1 16:22:35 2016 : Error:
>> /etc/freeradius/policy.d/canonicalization[95]: Invalid regular
>> expression:

Either check into whether FR is configured to use pcre expressions,
or write it out longhand.  The latter is probably the faster resolution.