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From "Hong Tang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6722) NetUtils.connect should check that it hasn't connected a socket to itself
Date Sun, 25 Apr 2010 01:29:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12860624#action_12860624
] 

Hong Tang commented on HADOOP-6722:
-----------------------------------

I was bit by this "feature" of TCP in my past life too. :)

> NetUtils.connect should check that it hasn't connected a socket to itself
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-6722
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6722
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hadoop-6722.txt
>
>
> I had no idea this was possible, but it turns out that a TCP connection will be established
in the rare case that the local side of the socket binds to the ephemeral port that you later
try to connect to. This can present itself in very very rare occasion when an RPC client is
trying to connect to a daemon running on the same node, but that daemon is down. To see what
I'm talking about, run "while true ; do telnet localhost 60020 ; done" on a multicore box
and wait several minutes.
> This can be easily detected in NetUtils.connect by making sure the local address/port
is not equal to the remote address/port.

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