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Helper Methods

Helper methods are for working with IP address and CIDR subnet masks.

Since IP objects are meant to be immutable, whenever an IP is returned it is returned as a new instance of Darsyn\IP\IpInterface rather than modifying the existing object - they are also returned as a static instance meaning an IPv4 object would return a new IPv4 object, an IPv6 returns IPv6, etc.

Concepts

CIDR (Subnet Mask)

Most of the the helper methods require a CIDR value. Anyone who has worked with CIDR notation before will most likely be used to a subnet mask between 0 and 32. However, since the Multi class deals with both IPv4 and IPv6 the CIDR values can range up to 128.

Instances of IPv4 will always deal with CIDR values between 0 and 32.

Instances of IPv6 will always deal with CIDR values between 0 and 128.

Instances of Multi will:

  • Detect if the IP address is a version 4 address (according to the embedding strategy).
  • If version 4 and the CIDR is less or equal to 32, attempt the method as if it was called from an IPv4 instance.
  • Otherwise, attempt the method as if it was called from an IPv6 instance.
<?php
use Darsyn\IP\Version\Multi as IP;

// IP is version 4 address and CIDR is <= 32. Uses IPv4::getNetworkIp().
IP::factory('127.0.0.1')->getNetworkIp(26);

// IP is version 4 address but CIDR is more than 32. Uses IPv6::getNetworkIp().
IP::factory('127.0.0.1')->getNetworkIp(107);

// IP is version 6 address. Uses IPv6::getNetworkIp(), even though CIDR is below 32.
IP::factory('2001:db8::a60:8a2e:0:7334')->getNetworkIp(31);

A Darsyn\IP\Exception\InvalidCidrException is thrown whenever a CIDR value that is out of range is supplied. Out of range values are any value that is:

  • Not an integer,
  • Below zero,
  • Above 32 (for IPv4), or
  • Above 128 (for IPv6 and Multi).

IP Comparison

Some of the helper methods accept another IP address to work against. To successfully compare IP address, both must be the same byte-length:

  • IPv4 instances can only be compared against other, as internally they are represented as 4-byte strings.
  • IPv6 and Multi can be compared against themselves and each other, as internally they are represented as 16-byte strings.

When using the Multi class to call the helper method, it will attempt the method as if it was called from an IPv4 instance if:

  • Both are IPv4-embedded addresses, and
  • Both are embedded using the same embedding strategy.

Otherwise, Multi attempts the method as if it was called from an IPv6 instance.

Examples

<?php

// IPv6 operation: helper method called from IPv6.
IPv6::factory('ffff:7f00:1')->inRange(Multi::factory('127.0.0.1'), 23);

// IPv4 operation: called from Multi, both IPs are IPv4-embedded, CIDR below 32.
Multi::factory('127.0.0.1')->inRange(Multi::factory('127.0.0.1'), 23);

// IPv6 operation: both IPv4-embedded, but CIDR above 32.
Multi::factory('127.0.0.1')->inRange(Multi::factory('127.0.0.1'), 35);

// IPv6 operation: supplied IP is not IPv4-embedded.
Multi::factory('127.0.0.1')->inRange(Multi::factory('d6be:583:b07a::c7'), 23);

// IPv6 operation: embedding strategies do not match.
Multi::factory('127.0.0.1', new Mapped)
    ->inRange(Multi::factory('127.0.0.1', new Derived), 23);

// WrongVersionException: Multi and IPv4 are different byte lengths.
Multi::factory('127.0.0.1')->inRange(IPv4::factory('127.0.0.1'), 23);

// InvalidCidrException: CIDR above 128.
Multi::factory('127.0.0.1')->inRange(Multi::factory('127.0.0.1'), 129);

Method Reference

Network IP

@throws \Darsyn\IP\Exception\InvalidCidrException

getNetworkIp(int $cidr): IpInterface

<?php
use Darsyn\IP\Version\Multi as IP;

$ip = IP::factory('12.34.56.78');
// Get the network address of an IP address given a subnet mask.
$networkIp = $ip->getNetworkIp(19);
$networkIp->getProtocolAppropriateAddress(); // string("12.34.32.0")

Broadcast IP

@throws \Darsyn\IP\Exception\InvalidCidrException

getBroadcastIp(int $cidr): bool

<?php
use Darsyn\IP\Version\Multi as IP;

$ip = IP::factory('12.34.56.78');
// Get the broadcast address of an IP address given a subnet mask.
$broadcastIp = $ip->getBroadcastIp(19);
$broadcastIp->getProtocolAppropriateAddress(); // string("12.34.63.255")

Is IP in Range?

@throws \Darsyn\IP\Exception\WrongVersionException
@throws \Darsyn\IP\Exception\InvalidCidrException

inRange(IpInterface $ip, int $cidr): bool

<?php
use Darsyn\IP\Version\Multi as IP;

$hostIp = IP::factory(':ffff:c22:384e');
$clientIp = IP::factory('12.48.183.1');

$clientIp->inRange($hostIp, 11); // bool(true)
$clientIp->inRange($hostIp, 24); // bool(false)

Greatest Common CIDR

@throws \Darsyn\IP\Exception\WrongVersionException

getCommonCidr(IpInterface $ip): int

<?php
use Darsyn\IP\Version\Multi as IP;

$hostIp = IP::factory('d6be:583:71a4:aa6d:c77d:77dd:cec:f897');
$clientIp = IP::factory('d6be:583:71a4:aa67:b07a::c7');
$hostIp->getCommonCidr($clientIp); // int(60)

IPv6 vs Multi?

The Multi class tries to deal with both IPv4 and IPv6 interchangeably which can lead to some unexpected results if an IPv6 address is detected as an IPv4-embedded address. Valid CIDR values can be either 0-32 or 0-128 depending on internal state and the embedding strategy used.

All the helper methods of Multi are affected by this.

The IPv6 class, however, gives consistent results regardless of embedding strategy and always deals with CIDR values from 0 to 128.

It is recommended that you pick a concrete version (either IPv4 or IPv6) unless you absolutely know that you need to deal with both interchangeably. Using Multi can cause unexpected behaviour.

For example, Multi::factory('0.0.0.1', new Strategy\Compatible) results in an object which is both a loopback address ::1 if viewing as IPv6, but also not a loopback address 127.x.x.x if viewing as an IPv4-embedded address.

Use Multi with caution.

IPv6 From Embedded

If you want to embed IPv4 addresses into IPv6, but do not want Multi to return varying results depending on whether an IPv4 address is embedded or not, then use IPv6::fromEmbedded().

It accepts both IPv4 and IPv6 addresses, embeds IPv4 addresses into IPv6 according to the embedding strategy, and from that point on treats it purely as an IPv6 address.

<?php
use Darsyn\IP\Strategy\Mapped;
use Darsyn\IP\Version\Ipv6;

// Strategy is optional; defaults to Mapped unless
// Multi::setDefaultEmbeddingStrategy() called previously.
$ip = IPv6::fromEmbedded('127.0.0.1', new Mapped);
$ip->getCompactedAddress(); // string("::ffff:7f00:1")

try {
    $ip->getDotAddress();
} catch (\Error $e) {
    // IPv6 addresses are not considered IPv4 addresses and
    // therefore do not have the method getDotAddress().
}

Please note that calling Multi::fromEmbedded() returns an instance of Multi and effectively is the same as calling the factory method.