usresmonitor 0.1.1

This library is inspired by an issue opened by Thomas Mangin on the repository of [InvalidRoutesReporter](https://github.com/pierky/invalidroutesreporter): https://github.com/pierky/invalidroutesreporter/issues/1

Given a set (or stream) of IP prefixes, this library calculates the unique smallest routable entries (SREs) covered by them.

De-duplication of overlapping prefixes is performed. SREs are calculated on the basis of a target prefix length that can be set on input.

Prefixes can be added and removed as they come (for example from a BGP session) and the resultant set of unique SREs is computed accordingly.

Example:

` >>> from pierky.usres_monitor import UniqueSmallestRoutableEntriesMonitor >>> monitor = UniqueSmallestRoutableEntriesMonitor(target_prefix_len4=24) >>> monitor.add_net("192.168.0.0/16") >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(4)] ['first: 192.168.0.0, last: 192.168.255.0, cnt: 256'] >>> monitor.get_count(4) 256 `

So, 192.168.0.0/16 contains 256 /24 subnets.

Now, add a prefix that is already covered by the previous one:

` >>> monitor.add_net("192.168.0.0/21") >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(4)] ['first: 192.168.0.0, last: 192.168.255.0, cnt: 256'] `

Nothing changed. Add a prefix that covers the 2 already added before:

` >>> monitor.add_net("192.0.0.0/8") >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(4)] ['first: 192.0.0.0, last: 192.255.255.0, cnt: 65536'] `

Here it is, 192.0.0.0/8 covers both 192.168.0.0/16 and 192.168.0.0/21 and contains 65536 /24 subnets.

Now remove the two larger prefixes:

` >>> monitor.del_net("192.0.0.0/8") >>> monitor.del_net("192.168.0.0/16") >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(4)] ['first: 192.168.0.0, last: 192.168.7.0, cnt: 8'] `

Only 192.168.0.0/21 remains, with its 8 /24 subnets.

Add now a second prefix:

` >>> monitor.add_net("192.168.8.0/21") >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(4)] ['first: 192.168.0.0, last: 192.168.7.0, cnt: 8', 'first: 192.168.8.0, last: 192.168.15.0, cnt: 8'] >>> monitor.get_count(4) 16 `

Two prefixes are printed, each one covering 8 SREs, for a total of 16 SREs.

Both IPv4 and IPv6 can be used, also simultaneously with the same monitor object:

` >>> from pierky.usres_monitor import UniqueSmallestRoutableEntriesMonitor >>> monitor = UniqueSmallestRoutableEntriesMonitor(target_prefix_len4=24, target_prefix_len6=56) >>> monitor.add_net("192.168.0.0/16") >>> monitor.add_net("10.0.0.0/8") >>> monitor.add_net("2001:db8:aaaa::/48") >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(4)] ['first: 192.168.0.0, last: 192.168.255.0, cnt: 256', 'first: 10.0.0.0, last: 10.255.255.0, cnt: 65536'] >>> ["first: {first_ip}, last: {last_ip}, cnt: {cnt}".format(**prefix) for prefix in monitor.get_prefixes(6)] ['first: 2001:db8:aaaa::, last: 2001:db8:aaaa:ff00::, cnt: 256'] >>> monitor.get_count(4) 65792 >>> monitor.get_count(6) 256 `