# plag

Tools to optimize a list of IP (v4 or v6) prefixes.
The tools read prefix list on stdin and output the result to stdout.

 - plagmax - returns a minimal superset of prefixes (loose mode)
 - plageq - aggregates to equal set of prefixes with submasks

## plagmax

`plagmax` aggregates prefixes in loose mode, in case where all subprefixes
are also allowed.
So in the output all subprefixes are ignored and neighbour prefixes are folded.

### Example

Input:

```
10.0.0.0/24
10.0.1.0/24
10.0.2.0/24
10.0.2.1/32
10.0.3.0/24
```

Output:

```
10.0.0.0/22
```

## plageq

`plagmax` aggregates prefixes in strict mode.
So it does not add or remove prefixes, but aggregates sets of subprefixes
with the same mask into larger prefixes with a submask.
It tries to get the minimal number of prefixes in its output.

### Example

Input:

```
10.0.0.0/24
10.0.1.0/24
10.0.2.0/24
10.0.2.1/32
10.0.3.0/24
```

Output:

```
10.0.0.0/22{24,24}
10.0.2.1/32
```

## Building

You will need only a C compiler and a standard library to build the tools.
A simple `make` run should do the job.

```bash
$ make
gcc -O3 -o lib.o -c lib.c
gcc -O3 -o plagmax plagmax.c lib.o
gcc -O3 -o plageq plageq.c lib.o
```

## Running

The tools read stdin where they expect IP prefixes one per line.
Prefixes are of the standard form: `<IP>[/<mask>]`.
Both IPv4 and IPv6 are allowed, you can freely mix them
and the input doesn't need to be sorted.
Mask part is optional, in this case prefix is considered a single IP
and the default of `32` for IPv4 and `128` for IPv6 is used.

`plagmax` outputs simple prefixes in the same format and
`plageq` outputs prefixes with added submask range:  
`<IP>/<mask>{<low>,<high>}`  
This matches all prefixes, having masks in range `<low>`-`<high>`
(inclusive) that lie inside the prefix `<IP>/<mask>`.
In case `<mask> = <low> = <high>` the submasks part is omitted.
This notation of submasks is used in `bird` routing daemon.

You can use `bgpq4` tool for example to fetch the list of prefixes
and pipe its output to the tools:

```bash
bgpq4 -4 -F '%n/%l\n' as-set-name | ./plageq > as-set-name.ipv4.strict.txt
bgpq4 -6 -F '%n/%l\n' as-set-name | ./plagmax > as-set-name.ipv6.loose.txt
```

Tools also output to stderr some statistics of using preallocated memory.