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  1. Commons Net
  2. NET-501

Race Condition on TelnetClient.disconnect() and TelnetInputStream.run() . java.lang.IllegalStateException: Queue is full! Cannot process another character.

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: 3.2
    • Fix Version/s: 3.3
    • Component/s: Telnet
    • Labels:
      None
    • Environment:

      Ubuntu 12.04 64 bits x86

      Description

      I'm getting the following exception while disconnecting a threaded (readerThread=true) TelnetClient connection.

      Exception in thread "Thread-160" java.lang.IllegalStateException: Queue is full! Cannot process another character. 
      	at org.apache.commons.net.telnet.TelnetInputStream.__processChar(TelnetInputStream.java:339)
      	at org.apache.commons.net.telnet.TelnetInputStream.run(TelnetInputStream.java:647)
      	at java.lang.Thread.run(Thread.java:722)
      

      I noticed that when TelnetClient.disconnect() is called the attribute _threaded is set to false while the thread in the TelnetInputStream.run() method could call TelnetInputStream()._processChar(...) throwing IllegalStateException

      This is a test program to reproduce the issue

      public class TestTelnetClient implements Runnable {
      
      	/**
      	 * @param args
      	 */
      	public static void main(String[] args) {
      		ArrayList<Thread> workers = new ArrayList<Thread>();
      		for( int i=0; i<1000; ++i){
      			Thread t = new Thread ( new TestTelnetClient() );
      			t.start();
      			workers.add(t);
      		}
      		for (Thread t : workers ) {			
      			try {
      				t.join();			
      			} catch (InterruptedException e) {
      				e.printStackTrace();
      			}
      		}			
      
      	}
      
      	@Override
      	public void run() {
      		System.out.println("Starting thread...");
      		TelnetClient tc = new TelnetClient();
      //		tc.setReaderThread(false);
      		try {
      			tc.connect("localhost", 23);
      			tc.setSoTimeout(1000);
      			InputStream in = tc.getInputStream();
      			int ch;
      			in.read();
      		} catch (SocketException e) {
      			e.printStackTrace();
      		} catch (IOException e) {
      			e.printStackTrace();
      		} finally {
      			System.out.println("Disconnecting...");
      			try {
      				tc.disconnect();
      			} catch (IOException e) {
      				// TODO Auto-generated catch block
      				e.printStackTrace();
      			}
      		}
      		
      	}
      
      }
      

      A telnet server (telnetd) is required. I also modified the initial banner ( /etc/issue.net ) with a lot of characters to get a better chance to receive information while calling disconnect.

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            • Assignee:
              Unassigned
              Reporter:
              jlastiri Julián Lastiri
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              Dates

              • Created:
                Updated:
                Resolved: