public static List getLocalHostLANAddresses()

in commons-jcs3-core/src/main/java/org/apache/commons/jcs3/utils/net/HostNameUtil.java [116:186]
54 lines of code
13 McCabe index (conditional complexity)

    public static List<InetAddress> getLocalHostLANAddresses()
        throws UnknownHostException
    {
        List<InetAddress> addresses = new ArrayList<>();

        try
        {
            InetAddress candidateAddress = null;
            // Iterate all NICs (network interface cards)...
            final Enumeration<NetworkInterface> ifaces = NetworkInterface.getNetworkInterfaces();
            while ( ifaces.hasMoreElements() )
            {
                final NetworkInterface iface = ifaces.nextElement();

                // Skip loopback interfaces
                if (iface.isLoopback() || !iface.isUp())
                {
                    continue;
                }

                // Iterate all IP addresses assigned to each card...
                for ( final Enumeration<InetAddress> inetAddrs = iface.getInetAddresses(); inetAddrs.hasMoreElements(); )
                {
                    final InetAddress inetAddr = inetAddrs.nextElement();
                    if ( !inetAddr.isLoopbackAddress() )
                    {
                        if (inetAddr.isSiteLocalAddress())
                        {
                            // Found non-loopback site-local address.
                            addresses.add(inetAddr);
                        }
                        if ( candidateAddress == null )
                        {
                            // Found non-loopback address, but not necessarily site-local.
                            // Store it as a candidate to be returned if site-local address is not subsequently found...
                            candidateAddress = inetAddr;
                            // Note that we don't repeatedly assign non-loopback non-site-local addresses as candidates,
                            // only the first. For subsequent iterations, candidate will be non-null.
                        }
                    }
                }
            }
            if (candidateAddress != null && addresses.isEmpty())
            {
                // We did not find a site-local address, but we found some other non-loopback address.
                // Server might have a non-site-local address assigned to its NIC (or it might be running
                // IPv6 which deprecates the "site-local" concept).
                addresses.add(candidateAddress);
            }
            // At this point, we did not find a non-loopback address.
            // Fall back to returning whatever InetAddress.getLocalHost() returns...
            if (addresses.isEmpty())
            {
                final InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();
                if ( jdkSuppliedAddress == null )
                {
                    throw new UnknownHostException( "The JDK InetAddress.getLocalHost() method unexpectedly returned null." );
                }
                addresses.add(jdkSuppliedAddress);
            }
        }
        catch ( final SocketException e )
        {
            final UnknownHostException unknownHostException = new UnknownHostException( "Failed to determine LAN address: "
                + e );
            unknownHostException.initCause( e );
            throw unknownHostException;
        }

        return addresses;
    }