From: cliff wu <uncutstone@...>
Date: 2006-05-16T13:06:19+09:00
Subject: A bug? Socket broken due to resource leak in failed connect?

It is really a triky problem.

Following code is used to illustrate the problem I encountered. Before 
you execute it, please ensure to be offline, so it can be run very fast. 
Please notice the line in tcpclient.rb "145.times do", it is the key 
issue.

Let me explain it.

Tcpserver.rb is a local tcp server simply sends a hello message whenever 
a client connects and sends a request. Tcpclient.rb first makes a 
connect to the local tcp server, then tries many times to connect to a 
bad ip addresses which indeed can never be connected.  So every try will 
raise a exception " Unknown Error - connect(2)". This exception is 
simply ignored and the client continues trying.

The wierd thing is , after certain number of tries, the established
connection between the tcp client and the local tcp server is broken.
So the line "from tcpclient.rb:19:in goodConn.puts" also raises a 
exception . Even more,
what exception "goodConn.puts" raised is realted to the number of
tries to connect to the bad ip.

a. if times is less than 140 , it acts normally, nothing wrong, a hello
message is received from the local tcp server. I got this:

Exception raised: Unknown Error - connect(2)
Hello from local tcp server

b. If 140< times <145, I got this :

Exception raised: Unknown Error - connect(2)
tcpclient.rb:19:in `write': Bad file descriptor (Errno::EBADF)
        from tcpclient.rb:19:in `puts'
        from tcpclient.rb:19:in `testsocket'
        from tcpclient.rb:25

c. if times > 145, I got this:
Exception raised: Unknown Error - connect(2)
tcpclient.rb:19:in `write': Invalid argument (Errno::EINVAL)
        from tcpclient.rb:19:in `puts'
        from tcpclient.rb:19:in `testsocket'
        from tcpclient.rb:25

General speaking, it seems a resource leak happens every time a
"Unknown Error-connect(2)" exception raised when the tcpclient
failed to connnect to a bad ip address. So after substantial times
of  tries, the leak accumulates and the socket is crushed. Is it a bug
of socket library??

Code is listed below, if you are insterested, please try it, run the
ftpserver.rb first, the run the tcpclient in another console. Be sure to 
be offline when you try the code. Being offline will make it run fast, 
otherwise it will take long time to run

tcpserver.rb:
require 'socket'

server = TCPServer.new('localhost',21)
while(session = server.accept)
  puts "Client Request: #{session.gets}"
  session.print "Hello from local tcp server"
  session.close
end

tcpclient.rb:

require 'socket'
def testsocket
  goodAddr = "localhost"
  goodConn = TCPSocket.new(goodAddr,21)

  badAddr = "137.144.70.12" #no connection could established on this
address
  145.times do
    badconn = nil
    begin
      badconn = TCPSocket.new(badAddr,21)
    rescue Exception => aException
      puts "Exception raised: #{aException.to_s}"
    ensure
      badconn.close if @badconn and not @badconn.closed?
    end
  end

  goodConn.puts("hello")
  s = goodConn.gets
  puts s
  goodConn.close
end

testsocket

My OS is windows 98, ruby version is ruby
1.8.2 (2004-12-25) [i386-mswin32].

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