[Twisted-Python] matching ip ranges

[Maarten ter Huurne]

On Wednesday 29 August 2007, Alec Matusis wrote:
> We need to match IP ranges of connections, were ranges are specified in the
> "/" notation (e.g. 10.10.2.0/24)
>
> What is the best way to do this without consuming too much CPU resources
> when the connection rate is very high?

Convert the IP address to an integer and check using an AND mask:

if ip & mask == base:
  # in range

where "ip" is the IP address of the incoming connection as an integer, "mask" 
is the netmask as an integer (/24 => 0xFFFFFF00) and "base" is the lowest IP 
address in the range ("base & mask == base" must hold).

Bye,
		Maarten
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