Domain name resolution not working in Java Applications on Ubuntu64 9.04 machine. All other software resolves DNS correctly

Question

I have an number of Java applications installed on an Ubuntu64 9.04 PC, and none of them can resolve domain names (there are multiple JRE\'s too - some of them are IBM produ

Answer 1

Once again, thanks to the guidance of the people here, I've found an answer. The Java program above works when I do the following:

java -Djava.net.preferIPv4Stack=true DomainResolutionTest

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Details:

jgreenwood@jeg-ubuntu64:~$ java -Djava.net.preferIPv4Stack=true DomainResolutionTest 
www.google.com/209.85.225.106
jgreenwood@jeg-ubuntu64:~$ java DomainResolutionTest ERROR: www.google.com
java.net.UnknownHostException: www.google.com
    at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
    at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:849)
    at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1200)
    at java.net.InetAddress.getAllByName0(InetAddress.java:1153)
    at java.net.InetAddress.getAllByName(InetAddress.java:1083)
    at java.net.InetAddress.getAllByName(InetAddress.java:1019)
    at java.net.InetAddress.getByName(InetAddress.java:969)
    at DomainResolutionTest.main(DomainResolutionTest.java:12)

It turns out that there is a bug in the IPv6 stack. There are a couple of posts that led me to this conclusion:

http://uclue.com/?xq=2127

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=477211

https://answers.launchpad.net/ubuntu/+question/23024

I sure hope I don't have to add the IPv4 crap in every time I run a Java app. The final solution may be in the second link - a missing package. We shall see.

Debian Bug report logs - #477211 ia32-sun-java6-bin: Needs to depend on lib32nss-mdns ... Cannot resolve domain names. Resolve fine on the rest of the system, have not tested with other JDK's. Installed from package and set with update-java-alternatives.

DNS works for everything else on my system. Running on Debian 2.6.23-AMD64. Have tried both Lenny packages and Sid packages. Works as expected with sun-java6-bin, fails with ia32-sun-java6-bin. Arg. ... If you hit java with strace you'll see that it is trying to use libnss_mdns4_minimal.so.2, which is available in the package lib32nss-mdns. You should add a dependency on that to fix the bug.

Same thing happens for sun-java6-bin - libnss-mdns is used here.

The package is indeed missing on my machine:

jgreenwood@jeg-ubuntu64:~$ dpkg -L lib32nss-mdns
Package `lib32nss-mdns' is not installed.
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.

Either way, I hope this post helps someone else, because this was a major PITA to figure out.

Answer 2

This solution (-Djava.net.preferIPv4Stack=true) also works when there is long runing lookupAllHostAddr.