routesum

routesum - summarize a list of IPs and networks to its shortest form

• Project Description
• Notice of Beta Status
• Command-Line Program
  • Usage
  • Description
  • Installation
• Golang Library
  • Sample Code
• Caveats
• Reporting Bugs and Issues
• Copyright and License

Project Description

routesum is both a command-line program and a Golang library that performs route summarization on a list of IP addresses and CIDR-formatted networks. Route summarization is the proess of reducing a list of IPs and networks to its shortest possible form. For example, given the following list of IPs and networks:

198.51.100.1
198.51.100.4
198.51.100.5
198.51.100.2/31
198.51.100.6/31

routesum will output:

198.51.100.1
198.51.100.2/31
198.51.100.4/30

How?

• 198.51.100.4 and 198.51.100.5 summarize to 198.51.100.4/31.
• 198.51.100.4/31 and 198.51.100.6/31 summarize to 198.51.100.4/30.
• 198.51.100.1 and 198.51.100.2/31 weren't summarized, so they are just returned.

This project has utility anywhere the shortest possible form of a list of IPs and networks is preferrable. It was initially conceived to facilitate automatic daily updates to a set of firewall rules for blocking incoming connections. In that application, the number of items on the blocklist corresponds to the maximum number of comparisons that the firewall needs to make against every single arriving packet. The shorter that list can be, the less work the firewall needs to do.

Notice of Beta Status

This software is in beta. No guarantees are made, including relating to interface stability. Also, take note of the caveats listed below. Comments, questions or suggestions for improvements are welcome on our GitHub Issue Tracker.

Command-Line Program

Usage

$ routesum -h
Usage of routesum:
  -show-mem-stats
        Whether or not to write memory usage stats to STDERR.

Description

routesum is a well-behaved CLI citizen. It takes input from STDIN, and outputs to STDOUT.

$ routesum < infile.txt > outfile.txt
$ cat infile.txt | routesum > outfile.txt
$ routesum
192.0.2.0
192.0.2.1
^D
192.0.2.0/31
$

Installation

Binary Releases

Precompiled releases are currently available on our Releases page for the following platforms and architectures:

• Linux (i386 and x86_64)
• macOS (x86_64 and arm64)
• Windows (i386 and x86_64)

Look for a release that ends in .tar.gz or .zip. Download the release archive for your platform and architecture. Uncompress the archive and you'll see an eponymous folder. In that folder, you'll find the routesum program. Copy that program to wherever you want it to live, and start using it.

Linux Packages

Prebuilt packages are currently available on our Releases page in the following formats:

• .deb (Ubuntu or Debian)
• .rpm (RedHat or CentOS)

On Ubuntu or Debian, use dpkg -i /path/to/the.deb as root. On RedHat or CentOS, rpm -i /path/to/the.rpm as root. routesum will be installed in to /usr/bin/routesum.

Building From Source

routesum is written in Golang, so you'll need a reasonably recent version of Go (1.16+). This project aims to maintain support for the two most recent major versions of the Go compiler.

With this in place, simply run:

$ go install github.com/PatrickCronin/routesum/cmd/routesum@latest

which will install routesum into the directory named by the GOBIN environment variable, which defaults to $GOPATH/bin or $HOME/go/bin if the GOPATH environment variable is not set.

Golang Library

The routesum library provides a type that maintains an ongoing summary of IPs and CIDR-formatted networks as they are added:

• rs := routesum.NewRouteSum()

The type offers two methods:

• rs.InsertFromString() adds an IP or a CIDR-formatted network to its internal summary.
• rs.SummaryStrings() returns the summarized routes as a slice of strings.

Library documentation is viewable in the code, or at pkg.go.dev.

Sample Code

import "github.com/PatrickCronin/routesum/pkg/routesum"

...

ipsAndNetworks := []string{
    "198.51.100.1",
    "198.51.100.4",
    "198.51.100.5",
    "198.51.100.2/31",
    "198.51.100.6/31",
}

rs := routesum.NewRouteSum()
for _, s := range ipsAndNetworks {
    if err := rs.InsertFromString(s); err != nil {
        ...
    }
}

summary := rs.SummaryStrings()
for _, s := range summary {
    fmt.Println(s)
}

Will print:

198.51.100.1
198.51.100.2/31
198.51.100.4/30

Caveats

• IPv4-embedded IPv6 addresses: routesum treats IPv4-embedded IPv6 addresses as distinct from their IPv4 counterparts. As an example, routesum will not think of 192.0.2.0 and ::ffff:192.0.2.0 as duplicates.

• Zero-Host Networks: To simplify its implementation, routesum internally converts IP addresses to 0-host networks (e.g. 192.0.2.1 => 192.0.2.1/32, and 2600:: => 2600::/128) for processing, and then converts all 0-host networks back to IPs when it returns its results.

• Sorting: routesum's output is not currently guaranteed to be sorted in any particular order.

Reporting Bugs and Issues

Bugs and other issues can be reported by filing an issue on our GitHub issue tracker.

Copyright and License

This software is Copyright (c) 2020-2021 by Patrick Cronin.

This is free software, licensed under the terms of the MIT License.