[jboss-jira] [JBoss JIRA] (JGRP-1973) FRAG2: message corruption when thread pools are disabled

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1973?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13124760#comment-13124760 ] 

Bela Ban commented on JGRP-1973:
--------------------------------

* Created a reproducer {{FragTest2}}. {{FRAG}} is *not* affected.
* Removing the {{pool instanceof DirectExecutor}} fixes the issue as the packet is copied. IMO it's better to copy here that in {{FRAG2}}.

> FRAG2: message corruption when thread pools are disabled
> --------------------------------------------------------
>
>                 Key: JGRP-1973
>                 URL: https://issues.jboss.org/browse/JGRP-1973
>             Project: JGroups
>          Issue Type: Bug
>    Affects Versions: 3.6.6
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.6.7
>
>
> When disabling the thread pools (regular, OOB) and using {{UDP}}, fragments of a message get corrupted as a single buffer ({{UDP.receive_buf}}) is reused.
> * If we send a message of 1000 bytes, and {{FRAG2.frag_size}} is set to 600, then {{FRAG2}} sends 2 fragments: f1 (offset=0, length=600) and f2 (offset=600, length=400).
> * f1 is received and placed into {{receive_buf}}, then sent up the stack *without copying* as the {{DirectExecutor}} thread pool doesn't copy the data
> * f1 is received by {{FRAG2}} and added to the fragments list at index 0. The buffer of the message points to {{receive_buf}}
> * f2 is received and *overwrites* f1 in {{receive_buf}} !
> * f2 is received by {{FRAG2}} and added to the fragments list at index 1. The buffer of the message points to {{receive_buf}}
> * {{FRAG2}} now creates a new message whose buffer is {{receive_buf}}[0-600] and {{receive_buf}}[600-1000].
> * The problem here is that {{receive_buf}} contains only f2, which overwrote f1, so the resulting message will be incorrect !
> This probably affects {{FRAG}}, too.
> Not too critical, as thread pools are enabled by default, and disabling them might even be removed in the future.
> SOLUTION: remove the check for DirectExecutor and copy the data if {{copy_buffer}} is true
> {code:title=Bar.java|borderStyle=solid}
> if(!copy_buffer || pool instanceof DirectExecutor)
>     pool.execute(new MyHandler(sender, data, offset, length)); // we don't make a copy if we execute on this thread
> else {
>     byte[] tmp=new byte[length];
>     System.arraycopy(data, offset, tmp, 0, length);
>     pool.execute(new MyHandler(sender, tmp, 0, tmp.length));
> }
> {code}



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