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This module provides types and useful methods for working with IPv4 and IPv6 network addresses, commonly called IP prefixes. The new `IpNet`, `Ipv4Net`, and `Ipv6Net` types build on the existing `IpAddr`, `Ipv4Addr`, and `Ipv6Addr` types already provided in Rust's standard library and align to their design to stay consistent.

The module also provides the `IpSubnets`, `Ipv4Subnets`, and `Ipv6Subnets` types for iterating over the subnets contained in an IP address range. The `IpAddrRange`, `Ipv4AddrRange`, and `Ipv6AddrRange` types for iterating over IP addresses in a range. And traits that extend `Ipv4Addr` and `Ipv6Addr` with methods for addition, subtraction, bitwise-and, and bitwise-or operations that are missing in Rust's standard library.

The module only uses stable features so it is guaranteed to compile using the stable toolchain. Tests aim for thorough coverage and can be found in both the test modules and doctests. Please file an [issue on GitHub] if you have any problems, requests, or suggested improvements.

Read the [documentation] for the full details. And find it on [Crates.io].

[documentation]: https://docs.rs/ipnet/
[Crates.io]: https://crates.io/crates/ipnet
[issue on GitHub]: https://github.com/krisprice/ipnet/issues

## Release 2.0 requirements

Release 2.0 requires Rust 1.26 or later. Release 1.0 used a custom emulated 128-bit integer type (`Emu128`) to fully support IPv6 addresses. This has been replaced with Rust's built-in 128-bit integer, which is now stable as of Rust 1.26. There are reports of issues using Rust's 128-bit integers on some targets (e.g. Emscripten). If you have issues on your chosen target, please continue to use the 1.0 release until that has been resolved.

## Examples

### Create a network address and print the hostmask and netmask

```rust
extern crate ipnet;
use std::net::{Ipv4Addr, Ipv6Addr};
use std::str::FromStr;
use ipnet::{IpNet, Ipv4Net, Ipv6Net};

fn main() {
    // Create an Ipv4Net and Ipv6Net from their constructors.

    let net4 = Ipv4Net::new(Ipv4Addr::new(10, 1, 1, 0), 24).unwrap();
    let net6 = Ipv6Net::new(Ipv6Addr::new(0xfd, 0, 0, 0, 0, 0, 0, 0), 24).unwrap();

    // They can also be created by a constructor that panics when the prefix length is invalid,

    let net4 = Ipv4Net::new_assert(Ipv4Addr::new(10, 1, 1, 0), 24);
    let net6 = Ipv6Net::new_assert(Ipv6Addr::new(0xfd, 0, 0, 0, 0, 0, 0, 0), 24);

    // or does not compile when called from a const context.

    const NET4: Ipv4Net = Ipv4Net::new_assert(Ipv4Addr::new(10, 1, 1, 0), 24);
    const NET6: Ipv6Net = Ipv6Net::new_assert(Ipv6Addr::new(0xfd, 0, 0, 0, 0, 0, 0, 0), 24);

    // They can also be created from string representations.

    let net4 = Ipv4Net::from_str("10.1.1.0/24").unwrap();
    let net6 = Ipv6Net::from_str("fd00::/24").unwrap();

    // Or alternatively as follows.
    
    let net4: Ipv4Net = "10.1.1.0/24".parse().unwrap();
    let net6: Ipv6Net = "fd00::/24".parse().unwrap();

    // IpNet can represent either an IPv4 or IPv6 network address.

    let net = IpNet::from(net4);
    
    // It can also be created from string representations.

    let net = IpNet::from_str("10.1.1.0/24").unwrap();
    let net: IpNet = "10.1.1.0/24".parse().unwrap();

    // There are a number of methods that can be used. Read the
    // documentation for the full details.

    println!("{} hostmask = {}", net, net.hostmask());
    println!("{} netmask = {}", net4, net4.netmask());
}
```

### Subdivide an existing IP network into smaller subnets

```rust
extern crate ipnet;
use ipnet::Ipv4Net;

fn main() {
    let net: Ipv4Net = "192.168.0.0/23".parse().unwrap();

    println!("\n/25 subnets in {}:", net);

    // Note: `subnets()` returns a `Result`. If the given prefix length
    // is less than the existing prefix length the `Result` will contain
    // an error.

    let subnets = net.subnets(25)
        .expect("PrefixLenError: new prefix length cannot be shorter than existing");

    // Output:
    //  subnet 0 = 192.168.0.0/25
    //  subnet 1 = 192.168.0.128/25
    //  subnet 2 = 192.168.1.0/25
    //  subnet 3 = 192.168.1.128/25

    for (i, n) in subnets.enumerate() {
        println!("\tsubnet {} = {}", i, n);
    }
}
```

### Iterate over the valid subnets between two IPv4 addresses

```rust
extern crate ipnet;
use std::net::Ipv4Addr;
use ipnet::Ipv4Subnets;

fn main() {
    let start = Ipv4Addr::new(10, 0, 0, 0);
    let end = Ipv4Addr::new(10, 0, 0, 239);

    println!("\n/0 or greater subnets between {} and {}:", start, end);

    // Output all subnets starting with the largest that will fit. This
    // will give us the smallest possible set of valid subnets.
    //
    // Output:
    //  subnet 0 = 10.0.0.0/25
    //  subnet 1 = 10.0.0.128/26
    //  subnet 2 = 10.0.0.192/27
    //  subnet 3 = 10.0.0.224/28

    let subnets = Ipv4Subnets::new(start, end, 0);

    for (i, n) in subnets.enumerate() {
        println!("\tsubnet {} = {}", i, n);
    }

    println!("\n/26 or greater subnets between {} and {}:", start, end);

    // Output all subnets with prefix lengths less than or equal to 26.
    // This results in more subnets, but limits them to a maximum size.
    //
    // Output:
    //  subnet 0 = 10.0.0.0/26
    //  subnet 1 = 10.0.0.64/26
    //  subnet 2 = 10.0.0.128/26
    //  subnet 3 = 10.0.0.192/27
    //  subnet 4 = 10.0.0.224/28

    let subnets = Ipv4Subnets::new(start, end, 26);

    for (i, n) in subnets.enumerate() {
        println!("\tsubnet {} = {}", i, n);
    }
}
```

### Aggregate a list of IP prefixes

```rust
extern crate ipnet;
use ipnet::IpNet;

fn main() {
    // Example input list of overlapping and adjacent prefixes.

    let strings = vec![
        "10.0.0.0/24", "10.0.1.0/24", "10.0.1.1/24", "10.0.1.2/24",
        "10.0.2.0/24",
        "10.1.0.0/24", "10.1.1.0/24",
        "192.168.0.0/24", "192.168.1.0/24", "192.168.2.0/24", "192.168.3.0/24",
        "fd00::/32", "fd00:1::/32",
    ];

    let nets: Vec<IpNet> = strings.iter().filter_map(|p| p.parse().ok()).collect();
    
    println!("\nAggregated IP prefixes:");
    
    // Output:
    //  10.0.0.0/23
    //  10.0.2.0/24
    //  10.1.0.0/23
    //  192.168.0.0/22
    //  fd00::/31
    
    for n in IpNet::aggregate(&nets) {
        println!("\t{}", n);
    }
}
```

## Future

* Implementing `std::ops::{Add, Sub, BitAnd, BitOr}` for `Ipv4Addr` and `Ipv6Addr` would be useful as these are common operations on IP addresses. If done, the extension traits provided in this module would be removed and the major version incremented. Implementing these requires a change to the standard library. I've started a thread on this topic on the [Rust Internals](https://internals.rust-lang.org/t/pre-rfc-implementing-add-sub-bitand-bitor-for-ipaddr-ipv4addr-ipv6addr/) discussion board.
* The results of `hosts()` and potentially `subnets()` should be represented as a `Range` rather than the custom `IpAddrRange` and `IpSubnets` types provided in this module. This requires the target types to have `Add` and `Step` implemented for them. Implementing `Add` for `IpAddr`, `Ipv4Addr`, and `Ipv6Addr` requires a change to the standard library (see above). And `Step` is still unstable so exploring this will also wait until it has stablized.

## License

Copyright (c) 2017, Juniper Networks, Inc. All rights reserved.

This code is licensed to you under either the MIT License or Apache License, Version 2.0 at your choice (the "License"). You may not use this code except in compliance with the License. This code is not an official Juniper product. You can obtain a copy of the License at: https://opensource.org/licenses/MIT or http://www.apache.org/licenses/LICENSE-2.0