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Date: Sat, 7 Feb 2015 19:15:35 +0000 (UTC)
From: "Steve Loughran (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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 <JIRA.12398839.1214232961170@arcas>
Subject: [jira] [Commented] (HADOOP-3619) DNS.getHosts triggers an
 ArrayIndexOutOfBoundsException in reverseDNS if one of the interfaces is
 IPv6
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    [ https://issues.apache.org/jira/browse/HADOOP-3619?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14310878#comment-14310878 ] 

Steve Loughran commented on HADOOP-3619:
----------------------------------------

-1 as is, though with a couple of iterations it should be ready to go in.

h3. production code

# no need to explicitly use {{java.net.Inet4Address}} & {{java.net.Inet6Address}}; they are imported & can be used directly.

# recommend: the naming exception to include a link to new hadoop wiki entry (ideally https://wiki.apache.org/hadoop/DNS) which we can expand to cover DNS issues for those users who don't know anything about them.
# the new ipv4/ipv6 methods should be private.
# {{getNibbleFromAddress()}} should be package scoped, tagged {{@VisibleForTesting}}, and have a test which that the example result comes from the example input. Given that there's no way to create a stub IPv6 address, the bytes->string generation logic could be pulled out and tested standalone.

h3. Test case
# {{assertEquals()}} comparators are inverted: expected value comes first.
# We can't have tests that expect the external network to be there, not even DNS. Is there a way to test this such that only localhost DNS lookup is needed?
# what happens to these tests on machines without IPv6 support? It's not directly a test failure, just a machine/network configuration. The test needs to recognise and handle this situation.

General

* hadoop style guide is 2 chars, no tabs, amongst other things.
see https://github.com/steveloughran/formality/blob/master/styleguide/styleguide.md for a side project of mine to document what is generally expected.

> DNS.getHosts triggers an ArrayIndexOutOfBoundsException in reverseDNS if one of the interfaces is IPv6
> ------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-3619
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3619
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: net
>            Reporter: Steve Loughran
>            Assignee: Dr. Martin Menzel
>              Labels: ipv6, patch
>         Attachments: HADOOP-3619-v2.patch
>
>
> reverseDNS tries to split a host address string by ".", and so fails if ":" is the separator, as it is in IPv6. When it tries to access the parts of the address, a stack trace is seen.


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