JDK-4773521 : InetAddress.getCanonicalHostName() does not return FQDN on SuSE Linux 8.0
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.net
  • Affected Version: 1.4.1,1.4.1_06
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • OS: linux,linux_suse_sles_8.2
  • CPU: x86
  • Submitted: 2002-11-04
  • Updated: 2003-01-14
  • Resolved: 2003-01-14
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1.4.2 b13Fixed
Related Reports
Duplicate :  

Name: rmT116609			Date: 11/04/2002

java version "1.4.1"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1-b21)
Java HotSpot(TM) Client VM (build 1.4.1-b21, mixed mode)


Linux swlinux 2.4.18-4GB #1 Wed May 29 15:47:24 UTC 2002 i686

SuSE Linux 8.0 (i386)

InetAddress.getCanonicalHostName() is not returning the fully-qualified domain name.  Instead, it is returning the IP address.  We really need the fully-qualified domain name, and this is the only routine documented to return
it.  The code only fails on SuSE 8.0.  We're sucessfully running in on Windows 2000, several versions of Red Hat Linux, and several versions of HP-UX.

The output of my test program on Red Hat Linux 7.1
(expected results):
My name is: kothay.fc.hp.com
My FQDN is: kothay.fc.hp.com
  My IP is:

InetAddress: kothay.fc.hp.com/

The output of my test program on SuSE 8.0 (actual results):
My name is: swlinux
My FQDN is:
  My IP is:

InetAddress: swlinux/

There are no error messages.

This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.net.UnknownHostException;

public class hostnameBug
    public static void main(String args[])
            InetAddress ia = InetAddress.getLocalHost();
            System.out.println("My name is: " + ia.getHostName());
            System.out.println("My FQDN is: " + ia.getCanonicalHostName());
            System.out.println("  My IP is: " + ia.getHostAddress());

            System.out.println("\nInetAddress: " + ia);
        catch (UnknownHostException e)
            System.out.println("oops, couldn't get localhost");

---------- END SOURCE ----------

(Review ID: 166641) 

CONVERTED DATA BugTraq+ Release Management Values COMMIT TO FIX: mantis-beta FIXED IN: mantis-beta INTEGRATED IN: mantis-b13 mantis-beta

EVALUATION InetAddress.getCanonicalHostName() method is specified to do best effort. But depending on the system configuration, we may not be able to return FQDN. In order for us to further the investigation, please provide us with your system configuration files, such as the hosts, your host name search path, your nslookup results on ptr record for your IP address. In the meantime, here's several things you can check: 1. Check your nsswitch.conf file or equivalent. On linux, you can use linuxconf to check your hostname search path. Does it contain DNS? if not, that could be the problem, 'cause usually hosts file or nis doesn't contain FQDN/IP mappings. If your host name search path do contain DNS, AND it precedes either hosts or other name lookup mechanisms, try the following: 2. Do a nslookup. issue a ptr command for your ip address does it return a FQDN? if it does, your DNS server does contain an A record for your machine. otherwise it doesn't. In case it doesn't, you will have to additional things to configure the FQDN/IP mapping, such as add appropriate entries to the DNS database. If your name search path does contain DNS, but it's not the first in the search path. Furthermore, you can't change the search sequence on your system, you can do the following: 3. Specify the JNDI DNS service provider to bypass the default system name service provider. Use the properties defined at http://java.sun.com/j2se/1.4/docs/guide/net/properties.html and look for JNDI DNS service provider settings. ###@###.### 2002-11-04 --------------------------------------------------------------- In glibc2.2.4 the IPv6 support in libnss_dns.so was moved to to a libnss_dns6.so. This means that IPv6-enabled applications using getaddrinfo/getnameinfo need /etc/nsswitch.conf changed to search the hosts database using "dns6" instead of "dns". In order words, "dns" is IPv4 only, and "dns6" is IPv4 and IPv6. SuSE 8.0 ships with IPv6 compiled into the kernel and glibc2.2.5. However it ships with /etc/nsswitch.conf configured to use "dns". This means that IPv6 lookups and reverse lookups aren't possible with an out-of-the-box SuSE 8.0 installation. Hopefully SuSE will fix this. J2SE 1.4.x is IPv6-enabled. When run on a machine with IPv6 enabled java.net.InetAddress's default name service provider will use getaddrinfo/getnameinfo to do lookups and reverse lookups resp. Reverse lookups of IPv4 addresses are done by providing an IPv4-mapped IPv6 address to getnameinfo. If /etc/nsswitch.conf is configured to search "dns" then this fails if glibc2.2.4 or newer is installed. RedHat 8.0 uses their own glibc2.2.93 and this is why the problem isn't observed on RedHat. On reflection the right thing would have been to provide the IPv4 address to getnameinfo rather than assuming that getnameinfo can handle an IPv4-mapped IPv6 address. Note that the issue isn't specific to the getCanonicalHostName method. Any reverse lookups via InetAddress.getByName will also run into this issue. This means that most applications using J2SE 1.4/1.4.1 on SuSE 8.0 will run into this issue. In the case of SuSE 8.0 the issue can be worked around by changing the hosts entry in /etc/nsswitch.conf to use dns6 instead of dns. Alternatively J2SE can be configured be IPv4-only by running it with java.net.preferIPv4Stack property set to "true". Yet another workaround is to use the DNS name service provider for InetAddress by configuring the sun.net.spi.nameservice.provider.1 system property to "dns,sun". ###@###.### 2002-11-15 If this issue isn't addressed in 1.4.2 then we should try to get it documented as a post-installation task for SuSE 8.0. ###@###.### 2002-11-22