How do I access the Connection-specific DNS Suffix for each NetworkInterface in Java?

Question

Is it possible within a Java program to access the string contained in the "Connection-specific DNS Suffix" field of a Windows machine's ipconfig /all output?

Eg:

C:>ipconfig /all

Ethernet adapter Local Area Connection:

    Connection-specific DNS Suffix  . : myexample.com  <======== This string
    Description . . . . . . . . . . . : Broadcom NetXtreme Gigabit Ethernet
    Physical Address. . . . . . . . . : 00-30-1B-B2-77-FF
    Dhcp Enabled. . . . . . . . . . . : Yes
    Autoconfiguration Enabled . . . . : Yes
    IP Address. . . . . . . . . . . . : 192.168.1.66
    Subnet Mask . . . . . . . . . . . : 255.255.255.0

I know that getDisplayName() will get return the Description (Eg: Broadcom NetXtreme Gigabit Ethernet above) and that getInetAddresses() will give me a list of the IP addresses bound to this network interface.

But are there also ways of reading the "Connection-specific DNS Suffix"?

score 3 · Answer 1 · answered Jun 02 '11 at 01:59

Ok so I figured out how to do this on Windows XP and Windows 7:

The string (eg: myexample.com) contained in the Connection-specific DNS Suffix field of each network interface listed in the output of ipconfig /all can be found in the registry at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces{GUID} (where GUID is the GUID of the network interface of interest) as the string value (type REG_SZ) named DhcpDomain.
Accessing windows registry keys is not straightforward in Java but by some clever use of reflection it is possible to access the required network adaptor's key found under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\ and then read the string data element with name DhcpDomain; its value is the required string.
See the following links for examples of accessing the windows registry from Java:
- http://www.rgagnon.com/javadetails/java-0630.html
- http://lenkite.blogspot.com/2008/05/access-windows-registry-using-java.html

score 1 · Answer 2 · answered Jan 29 '14 at 15:51

I used a much more complicated approach, which works on all platforms.

Tested on Windows 7, Ubuntu 12.04 and some unknown Linux distributions (Jenkins build hosts) and one MacBook (unknown MacOS X version).

Always with the Oracle JDK6. Never tested with other VM vendors.

String findDnsSuffix() {

// First I get the hosts name
// This one never contains the DNS suffix (Don't know if that is the case for all VM vendors)
String hostName = InetAddress.getLocalHost().getHostName().toLowerCase();

// Alsways convert host names to lower case. Host names are 
// case insensitive and I want to simplify comparison.

// Then I iterate over all network adapters that might be of interest
Enumeration<NetworkInterface> ifs = NetworkInterface.getNetworkInterfaces();

if (ifs == null) return ""; // Might be null

for (NetworkInterface iF : Collections.list(ifs)) { // convert enumeration to list.
    if (!iF.isUp()) continue;

    for (InetAddress address : Collections.list(iF.getInetAddresses())) {
        if (address.isMulticastAddress()) continue;

        // This name typically contains the DNS suffix. Again, at least on Oracle JDK
        String name = address.getHostName().toLowerCase();

        if (name.startsWith(hostName)) {
            String dnsSuffix = name.substring(hostName.length());
            if (dnsSuffix.startsWith(".")) return dnsSuffix;
        }
    }
}

return "";
}

Note: I wrote the code in the editor, did not copy the solution actually used. It also contains no error handling, like computers without a name, failure to resolve a DNS name, ...

This is rather late, but can you explain what exactly the outcome is for you on Windows 10. A very similar code works in production for years and it always worked. Also on Windows 10. There may be bugs though. — AndiHofi, Oct 22 '18 at 08:10

How do I access the Connection-specific DNS Suffix for each NetworkInterface in Java?

2 Answers2