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https://issues.apache.org/jira/browse/HDFS-4043?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17579761#comment-17579761
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ASF GitHub Bot commented on HDFS-4043:
--------------------------------------
snmvaughan commented on code in PR #4693:
URL: https://github.com/apache/hadoop/pull/4693#discussion_r945856788
##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/DNSDomainNameResolver.java:
##########
@@ -40,6 +48,16 @@ public String getHostnameByIP(InetAddress address) {
&& host.charAt(host.length()-1) == '.') {
host = host.substring(0, host.length()-1);
}
+ // Protect against the Java behaviour of returning the IP address as a
string from a cache
+ // instead of performing a reverse lookup.
+ if (host.equals(address.getHostAddress())) {
Review Comment:
It either returns what it figured out, or returns the IP address as a
string. There is no way of knowing when it is failing to provide an actual
FQDN, which is why there is the additional check to see if it is just the IP
address.
> Namenode Kerberos Login does not use proper hostname for host qualified hdfs
> principal name.
> --------------------------------------------------------------------------------------------
>
> Key: HDFS-4043
> URL: https://issues.apache.org/jira/browse/HDFS-4043
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: security
> Affects Versions: 2.0.0-alpha, 2.0.1-alpha, 2.0.2-alpha, 2.0.3-alpha,
> 3.4.0, 3.3.9
> Environment: CDH4U1 on Ubuntu 12.04
> Reporter: Ahad Rana
> Priority: Major
> Labels: pull-request-available
> Original Estimate: 24h
> Time Spent: 50m
> Remaining Estimate: 23h 10m
>
> The Namenode uses the loginAsNameNodeUser method in NameNode.java to login
> using the hdfs principal. This method in turn invokes SecurityUtil.login with
> a hostname (last parameter) obtained via a call to InetAddress.getHostName.
> This call does not always return the fully qualified host name, and thus
> causes the namenode to login to fail due to kerberos's inability to find a
> matching hdfs principal in the hdfs.keytab file. Instead it should use
> InetAddress.getCanonicalHostName. This is consistent with what is used
> internally by SecurityUtil.java to login in other services, such as the
> DataNode.
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