RFR: 7903730: Enhance the agentvm to be tolerant to unexpected connection on the port the Agent listens on for handshake with the AgentServer [v3]

[Mark Sheppard]

On Fri, 24 May 2024 14:49:45 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> JP, yes understood
>> I should have been more direct and precise in my comment i.e. 
>> the assert is not needed — restructure the if statement.
>> 
>> The condition can’t occur and if it did occur then what would that mean?
>> Is there a problem with either the code generated by javac ? or 
>> that the java runtime has a problem? or the return from InputStream.read is greater than expected, 
>> thus the InputStream has a problem?
>> 
>> An AgentServer is (nearly) always launched with “-ea” option — only if jtreg is launched from command line without -ea will it not have asserts enabled.
>> 
>> Looking at the current logic, rather than testing all negative cases, it can be restructured with
>> 
>> if (totalRead != JTREG_AGENT_HANDSHAKE_MAGIC.length) {
>>    // problem
>> } else {
>>    // check for connect message
>> }
>
> So we could do:
> 
> if (totalRead != JTREG_AGENT_HANDSHAKE_MAGIC.length) {
>     assert totalRead < JTREG_AGENT_HANDSHAKE_MAGIC.length
>    // problem
> } else {
>    // check for connect message
> }

just log the error and return null

           log("handshake failed - " + totalRead + " bytes received from " + s);
            return null;

assert is the equivalent of a programming wart

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PR Review Comment: https://git.openjdk.org/jtreg/pull/195#discussion_r1613853568