com.fasterxml.uuid

Class EgressInterfaceFinder

java.lang.Object

com.fasterxml.uuid.EgressInterfaceFinder

public class EgressInterfaceFinder
extends Object

A utility to attempt to find the default egress interface on the current system. The egress interface is the interface which is assigned the default network route, such that outbound network traffic is routed out through that interface.

Since:

4.2

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	EgressInterfaceFinder.EgressResolutionException An exception representing a failure to determine a default egress network interface.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_TIMEOUT_MILLIS

Constructor Summary

Constructors

Constructor and Description
EgressInterfaceFinder()

Method Summary

Modifier and Type	Method and Description
NetworkInterface	egressInterface() Attempt to find the default egress interface on the current system.
NetworkInterface	fromAggregate(com.fasterxml.uuid.EgressInterfaceFinder.Finder[] finders) Attempt to find the default egress interface on the current system, by trying each of the specified discovery mechanisms, in order, until one of them succeeds.
NetworkInterface	fromDefaultMechanisms(int timeoutMillis) Attempt to find the default egress interface on the current system, using the specified connection timeout duration.
NetworkInterface	fromLocalAddress(InetAddress localAddress) Attempt to find the default egress interface on the current system, by finding a NetworkInterface that has the specified network address.
NetworkInterface	fromRemoteConnection(int timeoutMillis, InetSocketAddress remoteAddress) Attempt to find the default egress interface on the current system, by connection to the specified address.
NetworkInterface	fromRemoteDatagramSocketConnection(InetSocketAddress remoteAddress) Attempt to find the default egress interface on the current system, using the specified connection timeout duration and connecting with a DatagramSocket.
NetworkInterface	fromRemoteSocketConnection(int timeoutMillis, InetSocketAddress remoteAddress) Attempt to find the default egress interface on the current system, using the specified connection timeout duration and connecting with a Socket.
NetworkInterface	fromRootNameserverConnection(int timeoutMillis) Attempt to find the default egress interface on the current system, by connecting to one of the root name servers (chosen at random).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_TIMEOUT_MILLIS

public static final int DEFAULT_TIMEOUT_MILLIS

See Also:

Constant Field Values

Constructor Detail

EgressInterfaceFinder

public EgressInterfaceFinder()

Method Detail

egressInterface

public NetworkInterface egressInterface()
                                 throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system.

This is done on a best efforts basis, as Java does not provide the necessary level of OS integration that is required to do this robustly. However, this utility should do a decent job on Windows, Linux and macOS so long as the local system has a working network connection at the time of execution. If the current system is multihomed with multiple egress interfaces, one such interface will be chosen indeterminately.

Accurately determining the egress interface necessitates us attempting to make outbound network connections. This will be done synchronously and can be a very slow process. You can tune the amount of time allowed to establish the outbound connections by increasing/decreasing the timeout value.

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromDefaultMechanisms

public NetworkInterface fromDefaultMechanisms(int timeoutMillis)
                                       throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, using the specified connection timeout duration.

This will attempt to connect to one of the root DNS nameservers (chosen randomly), and failing that, simply to IPv4 address 1.1.1.1 and finally IPv6 address 1::1.

Parameters:

timeoutMillis - the amount of time (milliseconds) allowed to establish an outbound connection

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromAggregate

public NetworkInterface fromAggregate(com.fasterxml.uuid.EgressInterfaceFinder.Finder[] finders)
                               throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, by trying each of the specified discovery mechanisms, in order, until one of them succeeds.

Parameters:

finders - array of finder callbacks to be executed

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromRootNameserverConnection

public NetworkInterface fromRootNameserverConnection(int timeoutMillis)
                                              throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, by connecting to one of the root name servers (chosen at random).

Parameters:

timeoutMillis - the amount of time (milliseconds) allowed to establish an outbound connection

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromRemoteConnection

public NetworkInterface fromRemoteConnection(int timeoutMillis,
                                             InetSocketAddress remoteAddress)
                                      throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, by connection to the specified address. This will try two different methods:

• using a DatagramSocket, which seems to work well for Windows & Linux, and is faster to uses than Socket as opening one does not actually require negotiate a handshake connection, but this does not appear to work on MacOS
• using a Socket, which seems to work better for MacOS, but needs to actually negotiate a connection handshake from a remote host

Parameters:

timeoutMillis - the amount of time (milliseconds) allowed to establish an outbound connection

remoteAddress - the address to which a connection will be attempted in order to determine which interface is used to connect

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromRemoteSocketConnection

public NetworkInterface fromRemoteSocketConnection(int timeoutMillis,
                                                   InetSocketAddress remoteAddress)
                                            throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, using the specified connection timeout duration and connecting with a Socket.

Parameters:

timeoutMillis - the amount of time (milliseconds) allowed to establish an outbound connection

remoteAddress - the address to which a connection will be attempted in order to determine which interface is used to connect

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromRemoteDatagramSocketConnection

public NetworkInterface fromRemoteDatagramSocketConnection(InetSocketAddress remoteAddress)
                                                    throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, using the specified connection timeout duration and connecting with a DatagramSocket.

Parameters:

remoteAddress - the address to which a connection will be attempted in order to determine which interface is used to connect

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2

fromLocalAddress

public NetworkInterface fromLocalAddress(InetAddress localAddress)
                                  throws EgressInterfaceFinder.EgressResolutionException

Attempt to find the default egress interface on the current system, by finding a NetworkInterface that has the specified network address. If more than one interface has the specified address, then one of them will be selected indeterminately.

Parameters:

localAddress - the local address which is assigned to an interface

Returns:

the egress interface

Throws:

EgressInterfaceFinder.EgressResolutionException - if an egress interface could not be determined

Since:

4.2